DESC:FIELD
The present disclosure relates to a device and a process for cleaning a char filter. Particularly, the present disclosure relates to a device and a process for cleaning a char filter that is used in pet coke, coal and biomass gasification plants.
DEFINITIONS
As used in the present disclosure, the following terms are generally intended to have the meaning as set forth below, except to the extent that the context in which they are used, indicate otherwise.
Bubble point method: The “bubble point method” refers to a most widely used method for the determination of a pore size. It is based on the fact that for a given fluid and pore size with a constant wetting, the pressure required to force an air or nitrogen bubble through the pore is inversely proportional to the size of the hole.
Bubble point: The term “bubble point” refers to a pore size of the char filter as determined by using bubble point method.
Bubble pressure: The term “bubble pressure” refers to a pressure at which a first bubble comes out of the pore of a filter, when determined by using a bubble point method.
Char filter: The term “char filter” commonly refers to a filter assembly containing a primary filter element having length of 2 meters to 3 meters and diameter of 50 mm to 70 mm and optionally a secondary filter called as fail-safe fuse element having length of 0.35 to 0.7 meter and diameter of 30 mm to 50 mm. Various grades of char filter work with or without fuse elements. Sintered metal powder (SMP) based filters protected on either side with woven meshes and sintered metal fiber-based filters with fuse elements are commonly used in gasification units. FeCrAl type of alloy is commonly used for filter media.
Differential pressure: The term “differential pressure” refers to a difference in the inlet side pressure of a filter and outlet side pressure of the filter.
Back Pulse gas: The term “back-pulse gas” refers to the online cleaning of filters using recycled clean syngas during normal operation. This is done via a series of pulse jet systems, which provide highly directed sonic pulses of clean process syngas into the filter elements providing expanding pressure fronts to fluidize and release the filter cake. The agglomerated contaminants settle within the vessel and are removed.
Frazier nitrogen permeability: the term “Frazier nitrogen permeability” refers to a rate at which nitrogen passes through the filter, when determined by using a Frazier permeability test device.
Piezo transducer: The term ‘piezo transducer” also referred to as a “piezoelectric transducer’ is a type of electroacoustic transducer that converts electrical charges produced by some forms of solid material into energy. The word "piezoelectric" literally means electricity caused by pressure.
Radial crushing strength: The term “radial crushing strength” refers to an ASTM method, determined by subjecting a plain sleeve bearing or a thin-walled cylindrical test specimen to a controlled compressive force applied perpendicular to its central axis under uniformly increasing load until fracture occurs.
Sonication: The term “sonication” also known as “ultra-sonication”, refers to a process that uses high frequency soundwaves (20 kHz to 60 KHz) which breaks large particles into smaller fragments and removes them from pores.
BACKGROUND
The background information herein below relates to the present disclosure but is not necessarily prior art.
During the gasification of carbonaceous feedstock, the metal content present in the carbonaceous feedstock vaporizes and forms a mixture with combustion or gasification gases. During gasification, the metal content may undergo transformation to different phases as well as different chemical compounds such as oxides may be formed. The metal content includes, but is not limited to, metals such as vanadium, nickel, zinc, iron, calcium, aluminum, and silicon. The combustion or gasification gases also contain tar as an impurity.
Conventionally, the equipment downstream to the gasification unit is at a temperature lower than the gasification unit. The syngas mixture containing metal contaminants and char are filtered through the main filter and/or fuse elements whose filter media size is 0.5 µm to 25 µm, which are layered with 100 µm to 300 µm meshes from both sides. The metal contaminants and char particles are knocked down using back pulse valves every 90 to180 seconds for duration of 5 to 10 seconds. However, metal contaminants deposited on the filter element having a hard-crystalline structure do not get dislodged from the filter elements, which lead to a high rate of rise in the differential pressure across the filters during the filtering operation.
This accelerated rate of differential pressure rise limits the operation of the gasifiers and also necessitates plant shut down for replacement of new filter elements. Therefore, the continuous operation of the gasification unit and the associated equipment is not possible for a long duration due to choking of the filters contaminated with the metal and char.
A filtration system consisting of sintered metal fiber, metal powder or ceramic are provided in the gasification unit to filter and recycle the unconverted char from the gasifier. A function of these filters is to filter the raw syngas from the unconverted char through a non-transient filter cake that has been developed on the filters. Another function of these filters is to filter the solids through the filter media. In case of failure of any filter element, wherein char and other solid particles breaks through the filter and get carried over to the downstream equipment which can lead to process downtime or upset condition. To prevent such a scenario, there is an option to install a fail-safe fuse element which will get plugged instantly after the failure of the filter element and consequently will prevent any char or solid particle carryover to the downstream equipment.
Generally, plugging of the fuse elements is not anticipated if the process conditions are as per design. However, these fuse elements can get plugged, if (i) some char or solid particles manage to get across the main filter elements and start depositing on the fuses or (ii) ingress of char or solid particles occur from the back-pulse system, which is generally used to clean the filter elements online as per a definite back-pulsing schedule.
Refurbishment and re-use of char filters will reduce the OPEX and it is a challenge to recover these elements after the run length of 200 to 350 days. Further, the mixed alloy of a filter gets corroded with deposited contaminants over a period of time and some of the components of the filters are also sensitive to moisture.
Conventional cleaning methods do not provide effective cleaning to achieve the desired differential pressure (<20 mbar) across char filters. Further, these methods are associated with various drawbacks such as higher acid and solvent concentration, longer treatment time, high pressure steam or air and damage on the surface layer of the filter elements.
The filters of gasifiers get choked with char and metal contaminants during operation which lead to accelerated rise in Dp (differential pressure) (>400 mbar) which limits the Gasifier’s performance. Consequently, cleaning of the choked filter elements is very critical as the conventional acid treatments are not effective to bring down the differential pressure to the desired level of <20 mbar without damaging the structural integrity of the filter elements. Removal of spent solid contaminants trapped inside the filter element is very difficult and depends on the type of contamination, run time, filter design and method of chemical treatment.
There is therefore felt a need for an improved, cost-effective and environment-friendly process for cleaning the filter of gasification units that alleviates the aforementioned drawback or at least provide a useful alternative.
OBJECTS
Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows:
It is an object of the present disclosure to ameliorate one or more problems of the background or to at least provide a useful alternative.
An object of the present disclosure is to provide a process for cleaning a char filter.
Another object of the present disclosure is to provide a process for cleaning a char filter of gasification unit.
Still another object of the present disclosure is to provide a process for cleaning of a char filter that does not damage the surface structural integrity of the filter elements.
Yet another object of the present disclosure is to provide a device for cleaning a char filter.
Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure.
SUMMARY
In an aspect, the present disclosure provides a process for cleaning a char filter, the process comprising the following steps: in a first step, a char filter is vacuumed to obtain a vacuumed filter. In a second step, the vacuumed filter is soaked in a first aqueous solution for a first predetermined time period to obtain a partially soaked filter, wherein the first aqueous solution comprises a predetermined amount of at least one first acid, and optionally at least one first surfactant. In a third step, the partially soaked filter is soaked in a second aqueous solution at a temperature in the range of 50 oC to 70 oC for a second predetermined time period to obtain a soaked filter, wherein the second aqueous solution comprises a predetermined amount of at least one alkali, and optionally at least one additive. In a fourth step, the soaked filter is rinsed with water to obtain a rinsed filter. In a fifth step, the rinsed filter is purged with air at a predetermined pressure to obtain a purged filter. In a sixth step, the purged filter is sonicated in a third aqueous solution at a first predetermined frequency for a third predetermined time period to obtain a pre-treated filter, wherein the third aqueous solution comprises a predetermined amount of at least one second acid, optionally at least one solvent, and optionally at least one second surfactant. In a seventh step, the pre-treated filter is sonicated in a fourth aqueous solution at a second predetermined frequency for a fourth predetermined time period to obtain a treated filter, wherein the fourth aqueous solution comprises a predetermined amount of at least one anti-corrosive agent, and optionally at least one third acid.
In an eighth step, the treated filter is dried in hot air under vacuum to obtain a cleaned char filter.
In accordance with the embodiments of the present disclosure, in the second step, the predetermined amount of the first acid is in the range of 1 mass% to 20 mass% with respect to the total mass of the first aqueous solution; and the predetermined amount of the first surfactant is in the range of 0 mass% to 10 mass% with respect to the total mass of the first aqueous solution.
In accordance with the embodiments of the present disclosure, in the second step, the first predetermined time period is in the range of 30 minutes to 180 minutes.
In accordance with the embodiments of the present disclosure, in the third step, the predetermined amount of the alkali is in the range of 1 mass% to 20 mass% with respect to the total mass of the second aqueous solution; and the predetermined amount of the additive is in the range of 0 mass% to 5 mass% with respect to the total mass of the second aqueous solution.
In accordance with the embodiments of the present disclosure, in the third step, the second predetermined time period is in the range of 100 minutes to 150 minutes.
In accordance with the embodiments of the present disclosure, in the fifth step, the predetermined pressure of air is in the range of 3 bars to 10 bars.
In accordance with the embodiments of the present disclosure, in the sixth step, the predetermined amount of the second acid is in the range of 0.5 mass% to 10 mass% with respect to the total mass of the third aqueous solution; the predetermined amount of the solvent is in the range of 0 mass% to 5 mass% with respect to the total mass of the third aqueous solution; and the predetermined amount of the second surfactant is in the range of 0 mass% to 10 mass% with respect to the total mass of the third aqueous solution.
In accordance with the embodiments of the present disclosure, in the sixth step, the first predetermined frequency is in the range of 20 kHz to 60 kHz; and the third predetermined time period is in the range of 60 minutes to 120 minutes.
In accordance with the embodiments of the present disclosure, in the seventh step, the predetermined amount of the anti-corrosive agent is in the range of 0.01 mass% to 2 mass% with respect to the total mass of the fourth aqueous solution; and the predetermined amount of the third acid is in the range of 0 mass% to 20 mass% with respect to the total mass of the fourth aqueous solution.
In accordance with the embodiments of the present disclosure, in the seventh step, the second predetermined frequency is in the range of 20 kHz to 60 kHz; and the fourth predetermined time period is in the range of 60 minutes to 120 minutes.
In accordance with the embodiments of the present disclosure, in the eighth step, the hot air has a temperature in the range of 50 oC to 100 oC.
In accordance with the embodiments of the present disclosure, the first acid, the second acid and the third acid are same or different, and are independently selected from the group consisting of citric acid, formic acid, acetic acid, nitric acid and phosphoric acid.
In accordance with the embodiments of the present disclosure, the alkali is selected from the group consisting of sodium hydroxide, sodium carbonate, potassium hydroxide, calcium hydroxide, magnesium hydroxide, ammonium hydroxide, and potassium borohydride.
In accordance with the embodiments of the present disclosure, the solvent is selected from the group consisting of methanol, ethanol, propanol and isopropanol.
In accordance with the embodiments of the present disclosure, the first surfactant and the second surfactant are same or different, and are independently selected from the group consisting of sodium stearate, 4-[5-dodecyl] benzene sulfonate, dioctyl sodium sulfosuccinate, alkyl ether phosphates, and perfluorooctanesulfonate.
In accordance with the embodiments of the present disclosure, the anti-corrosive agent is selected from the group consisting of Rodine-92BTM, sodium nitrite, calcium nitrite, sodium benzoate, tri ethanol amine (TEA), mono ethanol amine (MEA), di ethanol amine (DEA), methyl di ethanol amine (MDEA), di ethyl hydroxyl amine (DEHA), di ethyl amino ethanol amine (DEAE), tri sodium phosphate (TSP), and cyclo hexyl amine (CHA).
In accordance with the embodiments of the present disclosure, the anti-corrosive agent is combination of Rodine-92BTM, mono ethanol amine (MEA) and tri ethanol amine (TEA).
In accordance with the embodiments of the present disclosure, the additive is selected from the group consisting of urea, ethylene diamine tetra acetic acid (EDTA) and hydrogen peroxide.
In accordance with the embodiments of the present disclosure, the cleaned char filter is characterized by having differential pressure in the range of 5 mbar to 30 mbar; Frazier nitrogen permeability in the range of 6.0 ft3/s/ft2 to 11 ft3/s/ft2; radial crushing strength in the range of 75 MPa to 90 MPa; bubble pressure in the range of 0.30 psi to 0.38 psi; mean pore diameter in the range of 9 µm to 12 µm; and bubble point in the range of 17 µm to 20 µm.
In another aspect, the present disclosure provides a device for cleaning a char filter, the device comprises at least one metal tank configured to hold the filter; at least one piezo transducer being bonded to a bottom side of the metal tank and/or at least one side of the metal tank; and an electrical generator configured to generate an electrical signal of a predetermined frequency; wherein, the at least one piezo transducer is configured to change the predetermined frequency instantly when excited by the electrical signal; and size the at least one metal tank is selected based on the size of the filter.
In accordance with the embodiments of the present disclosure, the predetermined frequency is in the range of 20 kHz to 60 kHz.
In accordance with the embodiments of the present disclosure, the metal tank is made of a stainless steel.
In accordance with the embodiments of the present disclosure, the piezo transducer is made of a material selected from ceramic and lead zirconium titanate.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
The present disclosure will now be described with the help of the accompanying drawing, in which:
Fig. 1(a) illustrates a schematic diagram of a char filter along with its components;
Fig. 1(b) illustrates the filter cake formation on a char filter;
Fig. 1(c) illustrates the consequences of non-removal of filter cake from a char filter;
Fig. 2(a) illustrates a surface view of sintered metal powder (SMP) type triple char filter;
Fig. 2(b) illustrates a scanning electron microscope image of the surface of sintered metal powder (SMP) type triple char filter; and
Fig. 3 illustrates set-up of differential pressure measurements before and after cleaning of the filter.
LIST OF REFERENCE NUMERALS
1000 -2 filter vessel with 18 filter clusters each
101 – tube sheet
103 – dirty syngas
105 – char to gasifier
107 – dirty side
109 – clean side
111 – back pulse valves
200 – 18 filter cluster/vessel with 30 filter elements each
300 -1080 filter elements fitted with one fuse each
301 – dust free syngas
303 – filter element
305 – porous fuse
307 – back pulse gas
401 – solid laden syngas
403 – non-permanent ‘transient’ cake
405 – permanent cake
407 – filter media
409 – solids to gasifier
411 – permanent cake
413 – filter media
415 – backpulse gas
501 - ½” connection for digital manometer
505 – Pipe size 4”
507 – blind flange
509 – rotameter for flow measurement
511 – 1” globe valve
513 – 1” instrument air
514 – vent to atmosphere
DETAILED DESCRIPTION
The present disclosure relates to a process and a device for cleaning filter. Particularly, the present disclosure relates to a device and a process for cleaning the filter that is used in pet coke, coal and biomass gasification plants.
Embodiments, of the present disclosure, will now be described with reference to the accompanying drawing.
Embodiments are provided so as to thoroughly and fully convey the scope of the present disclosure to the person skilled in the art. Numerous details are set forth, relating to specific components, and methods, to provide a complete understanding of embodiments of the present disclosure. It will be apparent to the person skilled in the art that the details provided in the embodiments should not be construed to limit the scope of the present disclosure. In some embodiments, well-known processes, well-known apparatus structures, and well-known techniques are not described in detail.
The terminology used, in the present disclosure, is only for the purpose of explaining a particular embodiment and such terminology shall not be considered to limit the scope of the present disclosure. As used in the present disclosure, the forms "a,” "an," and "the" may be intended to include the plural forms as well, unless the context clearly suggests otherwise. The terms "comprises," "comprising," “including,” and “having,” are open ended transitional phrases and therefore specify the presence of stated features, integers, steps, operations, elements, modules, units and/or components, but do not forbid the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The particular order of steps disclosed in the method and process of the present disclosure is not to be construed as necessarily requiring their performance as described or illustrated. It is also to be understood that additional or alternative steps may be employed.
As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed elements.
The terms first, second, third, etc., should not be construed to limit the scope of the present disclosure as the aforementioned terms may be only used to distinguish one element, component, region, layer or section from another component, region, layer or section. Terms such as first, second, third etc., when used herein do not imply a specific sequence or order unless clearly suggested by the present disclosure.
Terms such as “inner,” “outer,” "beneath," "below," "lower," "above," "upper," and the like, may be used in the present disclosure to describe relationships between different elements as depicted from the figures.
During the gasification of carbonaceous feedstock, the metal content present in the carbonaceous feedstock vaporizes and forms a mixture with combustion or gasification gases. During gasification, the metal content may undergo transformation to different phases as well as different chemical compounds such as oxides may be formed. The metal content includes, but is not limited to, metals such as vanadium, nickel, zinc, iron, calcium, aluminum, and silicon. The combustion or gasification gases also contain tar as an impurity.
Conventionally, the equipment downstream to the gasification unit is at a temperature lower than the gasification unit. The syngas mixture containing metal contaminants and char are filtered through the main filter and/or fuse elements whose filter media size is 0.5 µm to 25 µm, which are layered with 100 µm to 300 µm meshes from both sides. The metal contaminants and char particles are knocked down using back pulse valves every 90 to180 seconds for duration of 5 to 10 seconds. However, metal contaminants deposited on the filter element having a hard-crystalline structure do not get dislodged from the filter elements, which lead to a high rate of rise in the differential pressure across the filters during the filtering operation.
This accelerated rate of differential pressure rise limits the operation of the gasifiers and also necessitates plant shut down for replacement of new filter elements. Therefore, the continuous operation of the gasification unit and the associated equipment is not possible for a long duration due to choking of the filters contaminated with the metal and char.
A filtration system consisting of sintered metal fiber, metal powder or ceramic are provided in the gasification unit to filter and recycle the unconverted char from the gasifier. A function of these filters is to filter the raw syngas from the unconverted char through a non-transient filter cake that has been developed on the filters. Another function of these filters is to filter the solids through the filter media. In case of failure of any filter element, wherein char and other solid particles breaks through the filter and get carried over to the downstream equipment which can lead to process downtime or upset condition. To prevent such a scenario, there is an option to install a fail-safe fuse element which will get plugged instantly after the failure of the filter element and consequently will prevent any char or solid particle carryover to the downstream equipment.
Generally, plugging of the fuse elements is not anticipated if the process conditions are as per design. However, these fuse elements can get plugged, if (i) some char or solid particles manage to get across the main filter elements and start depositing on the fuses or (ii) ingress of char or solid particles occur from the back-pulse system, which is generally used to clean the filter elements online as per a definite back-pulsing schedule.
Refurbishment and re-use of char filters will reduce the OPEX and it is a challenge to recover these elements after the run length of 200 to 350 days. Further, the mixed alloy of a filter gets corroded with deposited contaminants over a period of time and some of the components of the filters are also sensitive to moisture.
Conventional cleaning methods do not provide effective cleaning to achieve the desired differential pressure (<20 mbar) across char filters. Further, these methods are associated with various drawbacks such as higher acid and solvent concentration, longer treatment time, high pressure steam or air and damage on the surface layer of the filter elements.
The filters of gasifiers get choked with char and metal contaminants during operation which lead to accelerated rise in Dp (differential pressure) (>400 mbar) which limits the Gasifier’s performance. Consequently, cleaning of the choked filter elements is very critical as the conventional acid treatments are not effective to bring down the differential pressure to the desired level of <20 mbar without damaging the structural integrity of the filter elements. Removal of spent solid contaminants trapped inside the filter element is very difficult and depends on the type of contamination, run time, filter design and method of chemical treatment.
The present disclosure provides a process and a device for cleaning char filters. Particularly, the present disclosure relates to a process and a device for cleaning char filters used in the pet coke, coal and biomass gasification units. In an embodiment, the process of the present disclosure is suitable for a char filter, which is utilized downstream of pet coke gasification. The feedstock used for the gasification can include, but is not limited to petroleum coke, coal, biomass and a mixture thereof. Other suitable feedstock can also be used.
Fig. 1(a) illustrates a schematic diagram of a commonly used char filter along with its components. The char filters commonly have two filter vessels 1000 that have filter clusters 200 and elements 300/303. The components of the char filter are tube sheet 101, dirty syngas inlet 103, char to gasifier 105, dirty side 107, clean side 109, back pulse valves 111, 18 filter cluster/vessel with 30 filter elements each 200, 1080 filter elements fitted with one fuse each 300, dust free syngas 301, filter element 303, porous fuse 305, and back pulse gas 307.
Fig. 1(b) illustrates filter cake formation on a char filter. Fig. 1(c) illustrates consequences of a choked char filter. A solid laden syngas 401 is passed through the filter media 407, forming a non-permanent ‘transient’ cake 403, and a permanent cake 405. If not removed, the solids flow to the gasifier 409, to form a permanent cake 411 on the filter media 413, is causing backpulse gas 415.
In an aspect, the present disclosure provides a process for cleaning a char filter. The process for cleaning the char filter comprises the following steps:
In a first step, a char filter is vacuumed to obtain a vacuumed filter.
In accordance with the present disclosure, the filter is vacuumed/vacuum cleaned in the first step to loosen or dislodging or remove excess surface char particles under vacuum. In an embodiment, the vacuuming is performed at a pressure of less than 0.5 atmosphere, typically in the range of 0.01 to 0.05 atmosphere.
In accordance with the embodiments of the present disclosure, the temperature of vacuuming the char filter is in the range of 30 oC to 40 oC. In an exemplary embodiment, the temperature of vacuuming the char filter is 35 oC.
In accordance with the embodiments of the present disclosure, the time period for vacuuming the filter is in the range of 5 minutes to 15 minutes. In an exemplary embodiment, the time period for vacuuming the filter is 10 minutes.
In a second step, the vacuumed filter is soaked in a first aqueous solution for a first predetermined time period to obtain a partially soaked filter, wherein the first aqueous solution comprises a predetermined amount of at least one first acid, and optionally at least one first surfactant.
In accordance with the embodiments of the present disclosure, the first acid is selected from the group consisting of citric acid, formic acid, acetic acid, nitric acid and phosphoric acid. In an exemplary embodiment, the first acid is citric acid. In another embodiment, the first acid is phosphoric acid.
In accordance with the embodiments of the present disclosure, the predetermined amount of the first acid is in the range of 1 mass% to 20 mass% with respect to the total mass of the first aqueous solution. In an exemplary embodiment, the predetermined amount of the first acid is 5 mass% with respect to the total mass of the first aqueous solution.
In accordance with the embodiments of the present disclosure, the first surfactant is selected from the group consisting of sodium stearate, 4-[5-dodecyl] benzene sulfonate, dioctyl sodium sulfosuccinate, and alkyl ether phosphates, perfluorooctanesulfonate. In an exemplary embodiment, the first surfactant is sodium stearate.
In accordance with the embodiments of the present disclosure, the predetermined amount of the first surfactant is in the range of 0 mass% to 10 mass% with respect to the total mass of the first aqueous solution. In an exemplary embodiment, the predetermined amount of the first surfactant is 1.5 mass% with respect to the total mass of the first aqueous solution.
In accordance with the embodiments of the present disclosure, the pH of the first aqueous solution is in the range of 3 to 6. In an exemplary embodiment, the pH of the first solution is 4.5. The pH is not adjusted in the process.
In accordance with the embodiments of the present disclosure, the first predetermined time period is in the range of 30 minutes to 180 minutes. In an exemplary embodiment, the first predetermined time period is 105 minutes.
In accordance with the embodiments of the present disclosure, the temperature of the first aqueous solution is in the range of 20 oC to 40 oC. In an exemplary embodiment of the present disclosure, the temperature of the first aqueous solution is 30 oC.
In a third step, the partially soaked filter is soaked in a second aqueous solution at a temperature in the range of 50 oC to 70 oC for a second predetermined time period to obtain a soaked filter, wherein the second aqueous solution comprises a predetermined amount of at least one alkali, and optionally at least one additive.
In accordance with the embodiments of the present disclosure, the pH of second aqueous solution is in the range of 8 to 12. In an exemplary embodiment, the pH of the second aqueous solution is 11. No pH is adjusted in the process.
In an exemplary embodiment, the temperature of the second aqueous solution is 60 oC.
In accordance with the embodiments of the present disclosure, the alkali is selected from the group consisting of sodium hydroxide, sodium carbonate, potassium hydroxide, calcium hydroxide, magnesium hydroxide, ammonium hydroxide, and potassium borohydride. In an exemplary embodiment, the alkali is sodium hydroxide. In another exemplary embodiment, the alkali is sodium carbonate.
In accordance with the embodiments of the present disclosure, the predetermined amount of the alkali is in the range of 1 mass% to 20 mass% with respect to the total mass of the second aqueous solution. In an exemplary embodiment, the predetermined amount of the alkali is 5 mass% with respect to the total mass of the second aqueous solution.
In accordance with the embodiments of the present disclosure, the additive is selected from the group consisting of urea, ethylene diamine tetra acetic acid (EDTA) and hydrogen peroxide. In an exemplary embodiment, the additive is EDTA.
In accordance with the embodiments of the present disclosure, the predetermined amount of the additive is in the range of 0 mass% to 5 mass% with respect to the total mass of the second aqueous solution. In an exemplary embodiment, the predetermined amount of additive is 2% with respect to the total mass of the second aqueous solution.
The steps of soaking the filter in first solution and in the second solution help to break the metallic bonds.
In a fourth step, the soaked filter is rinsed with water to obtain a rinsed filter. The step of rinsing the filter flushes the chemical used in the previous steps.
The step of rinsing in water is carried out at a temperature of 30 oC to 40 oC.
In a fifth step, the rinsed filter is purged with air at a predetermined pressure to obtain a purged filter.
In accordance with the embodiments of the present disclosure, the predetermined pressure of air is in the range of 3 bars to 10 bars. In an exemplary embodiment, the predetermined pressure of air is 7 bars.
In accordance with the embodiments of the present disclosure, the time period of purging the air through the rinsed filter is in the range of 5 minutes to 30 minutes. In an exemplary embodiment, the time period of purging the air through the rinsed filter is 15 minutes.
In accordance with the embodiments of the present disclosure, the rate of purging the air through the rinsed filter is in the range of 20 m3/h to 60 m3/h. In an exemplary embodiment, the predetermined rate of purging the air through the rinsed filter is 35 m3/h.
The step of purging the air through the rinsed filter removes the moisture and any stuck material in the pores of the filter.
In a sixth step, the purged filter is sonicated in a third aqueous solution at a first predetermined frequency for a third predetermined time period to obtain a pre-treated filter, wherein the third aqueous solution comprises a predetermined amount of at least one second acid, optionally at least one solvent, and optionally at least one second surfactant.
In accordance with the embodiments of the present disclosure, the second acid is selected from the group consisting of citric acid, formic acid, acetic acid, nitric acid and phosphoric acid. In an exemplary embodiment, the second acid is phosphoric acid.
In accordance with the embodiments of the present disclosure, the predetermined amount of the second acid is in the range of 0.5 mass% to 10 mass% with respect to the total mass of the third aqueous solution. In an exemplary embodiment, the predetermined amount of second acid is 5 mass% with respect to the total mass of the third aqueous solution.
In accordance with the embodiments of the present disclosure, the solvent is selected from the group consisting of methanol, ethanol, propanol and isopropanol. In an exemplary embodiment, the third solvent is isopropanol.
In accordance with the embodiments of the present disclosure, the predetermined amount of the solvent is in the range of 0 mass% to 5 mass% with respect to the total mass of the third aqueous solution. In an exemplary embodiment, the predetermined amount of the solvent is 2 mass% with respect to the total mass of the third aqueous solution.
In accordance with the embodiments of the present disclosure, the second surfactant is selected from the group consisting of sodium stearate, 4-[5-dodecyl] benzene sulfonate, dioctyl sodium sulfosuccinate, alkyl ether phosphates, perfluorooctanesulfonate. In an exemplary embodiment, the second surfactant is sodium stearate.
In accordance with the embodiments of the present disclosure, the predetermined amount of the second surfactant is in the range of 0 mass% to 10 mass% with respect to the total mass of the third aqueous solution. In an exemplary embodiment, the predetermined amount of the second surfactant is 1.5 mass% with respect to the total mass of the third aqueous solution.
In accordance with the embodiments of the present disclosure, the first predetermined frequency is in the range of 20 kHz to 60 kHz. In an exemplary embodiment, the first predetermined frequency is 40 kHz.
In accordance with the embodiments of the present disclosure, the third predetermined time period is in the range of 60 minutes to 120 minutes. In an exemplary embodiment, the third predetermined time period is 90 minutes.
This step of ultra-sonication helps to remove micro-char particles from filter pores. The micro-char particles refer to the char particles having a particle size of less than 1000 µm.
In a seventh step, the pre-treated filter is sonicated in a fourth aqueous solution at a second predetermined frequency for a fourth predetermined time period to obtain a treated filter, wherein the fourth aqueous solution comprises a predetermined amount of at least one anti-corrosive agent, and optionally at least one third acid.
In accordance with the embodiments of the present disclosure, the anti-corrosive agent is selected from the group consisting of Rodine-92BTM, sodium nitrite, calcium nitrite, sodium benzoate, tri ethanol amine (TEA), mono ethanol amine (MEA), di ethanol amine (DEA), methyl di ethanol amine (MDEA), di ethyl hydroxyl amine (DEHA), di ethyl amino ethanol amine (DEAE), tri sodium phosphate (TSP), and cyclo hexyl amine (CHA).
In accordance with an exemplary embodiment, the anti-corrosive agent is combination of Rodine-92BTM, mono ethanol amine (MEA) and tri ethanol amine (TEA).
In accordance with the embodiments of the present disclosure, the predetermined amount of the anti-corrosive agent is in the range of 0.01 mass% to 2 mass% with respect to the total mass of the fourth aqueous solution. In an exemplary embodiment, the predetermined amount of the anti-corrosive agent is 0.5 mass% with respect to the total mass of the fourth aqueous solution.
In accordance with the embodiments of the present disclosure, the third acid is selected from the group consisting of citric acid, formic acid, acetic acid, nitric acid and phosphoric acid. In an embodiment, the third acid is phosphoric acid. In another embodiment, the third acid is citric acid.
In accordance with the embodiments of the present disclosure, the predetermined amount of the third acid is in the range of 0 mass% to 20 mass% with respect to the total mass of the fourth aqueous solution. In an embodiment, the predetermined amount of the third acid is 5 mass% with respect to the total mass of the fourth aqueous solution.
In accordance with the embodiments of the present disclosure, the second predetermined frequency is in the range of 20 kHz to 60 kHz. In an exemplary embodiment, the second predetermined frequency is 40 kHz.
In accordance with the embodiments of the present disclosure, the fourth predetermined time period is in the range of 60 minutes to 120 minutes. In an exemplary embodiment, the fourth predetermined time period is 90 minutes.
Ultra-sonication of the filter with anti-corrosive agent improves removal of contaminants to achieve the desired differential pressure.
In an eighth step, the treated filter is dried in hot air under vacuum to obtain a cleaned char filter.
In accordance with the present disclosure, the filter is hot dried under vacuum to remove residual moisture.
In accordance with the embodiments of the present disclosure, the hot air has a temperature in the range of 50 oC to 100 oC. In an exemplary embodiment, the hot air has a temperature of 70 oC. In another exemplary embodiment, the hot air has a temperature of 90 oC.
In accordance with the embodiments of the present disclosure, the time period for drying the treated filter is 20 minutes to 70 minutes. In an exemplary embodiment, the time period for drying the treated filter under vacuum is 30 minutes. In another exemplary embodiment, the time period for drying under vacuum the treated filter is 60 minutes.
The step of drying the filter helps remove water from the surface and pores of the filter. Vaccum drying helps for better removal of moisture from the inside the pores which also helps for improvement in differential pressure. Hot air drying was performed for effective drying of the cleaned char filter to ensure that no moisture remains there in the filter post cleaning.
The so obtained cleaned filter is packed in polypropylene liner bag under inert atmosphere to prevent from moisture ingression.
In accordance with the embodiments of the present disclosure, the first acid, the second acid and the third acid are same or different, and are independently selected from the group consisting of citric acid, formic acid, acetic acid, nitric acid and phosphoric acid.
In accordance with the process of the present disclosure, a differential pressure of the filter achieved after cleaning is in the range of 5 mbar to 30 mbar. In an embodiment, the differential pressure of the filter achieved after cleaning is <20 mbar. In an exemplary embodiment, the differential pressure of the filter achieved after cleaning is 8 mbar. In an exemplary embodiment, the differential pressure of the filter achieved after cleaning is 12 mbar. The desired differential pressure of the filter after cleaning process is <20 mbar.
In an embodiment, the steps to the process can be repeated to obtain the desired differential pressure or results.
In accordance with the process of the present disclosure, Frazier nitrogen permeability of the filter achieved after cleaning is in the range of 6.0 ft3/s/ft2 to11 ft3/s/ft2. In an exemplary embodiment, the permeability of the filter achieved after cleaning is 9 ft3/s/ft2.
In accordance with the process of the present disclosure, a radial crushing strength of the filter achieved is in the range of 75 MPa to 90 MPa. In an exemplary embodiment, the radial crushing strength of the filter achieved is 76.4 MPa.
In accordance with the process of the present disclosure, bubble pressure of the filter achieved after cleaning is in the range of 0.30 psi to 0.38 psi. In an exemplary embodiment, the bubble pressure of the filter achieved after cleaning is 0.32 psi.
In accordance with the process of the present disclosure, a mean pore diameter of the filter achieved after cleaning is in the range of 9 µm to 12 µm. In an exemplary embodiment, the mean pore diameter is 10.6 µm.
In accordance with the process of the present disclosure, bubble point of the filter achieved after cleaning is in the range of 17 µm to 20 µm. In an exemplary embodiment, the bubble point is 19.8 µm.
In accordance with the present disclosure, the filter elements are cylindrical in form (see Fig. 1(a)). The filter elements are 2400 mm to 2800 mm in length and 60 mm to 70 mm in diameter. The filter elements are typically made up of sintered metal fiber composite (FeCrAl alloy) and sintered metal powder composite (iron aluminide based).
In accordance with the present disclosure, the filter can include, but is not limited to sintered metal powder-based filter, sintered metal fiber-based filter, ceramic based filter, and filter prepared from mixture of grades. Other suitable filters can also be used.
In accordance with an embodiment of the present disclosure, the sintered metal powder-based filter is constructed with alloy of Fe3Al-type.
Fig. 2(a) illustrates a surface view of sintered metal powder (SMP) type triple char filter. Fig. 2(b) illustrates a scanning electron microscope (SEM) image of the surface of sintered metal powder (SMP) type triple char filter. The SEM image showed a broad range of pore size distribution and void volume resulting in high filtration efficiency.
The typical chemical composition of the material deposit on the char filter is shown in TABLE 1 as measured from Inductively Coupled Plasma (ICP) analysis.
TABLE 1: Metal composition details of the deposited material from the char filter elements
Sample description Filter deposit
Sl. No. Parameter Result in wt.%
1 Ash at 750 °C 90.09
2 Carbon 22.1
3 Sulphur 6.1
4 Ash composition
MoO4 0.15
ZnO 5.08
P2O5 0.57
Pb2O3 1
CoO 0.01
NiO 17.82
Fe2O3 4.13
SiO2 21.13
MnO2 0.07
Cr2O3 0.2
MgO 1.29
V2O5 16.32
CaO 14.57
CuO 0.01
Al2O3 12.61
Na2O 1.43
K2O 1.55
TiO2 0.84
The filter deposited composition shown in Table 1 is the typical material recovered during the cleaning process.
The process of the present disclosure does not affect the structural/physical properties such as pore diameter and bubble point pressure and the like of the filter even after cleaning.
The process of the present disclosure provides the desired air flow test and permeability test results of the filter even after cleaning.
The process of the present disclosure does not affect the metallurgical properties such as crushing strength, material of construction and 3-point bending strength of the filter even after cleaning.
The process of the present disclosure allows the re-use of the filter for intend applications to reduce the OPEX cost. In another aspect, the present disclosure provides a device for cleaning a char filter. The device comprises at least one metal tank configured to hold the filter, at least one piezo transducer being bonded to a bottom side of the metal tank and/or at least one side of the metal tank; and an electrical generator configured to generate an electrical signal of a predetermined frequency. The at least one piezo transducer is configured to change the predetermined frequency instantly when excited by the electrical signal. Size of the at least one metal tank is selected based on the size of the filter.
In accordance with the embodiments of the present disclosure, the predetermined frequency is in the range of 20 kHz to 60 kHz. In an exemplary embodiment, the predetermined frequency is 40 kHz.
In accordance with the embodiments of the present disclosure, the metal tank is made of a stainless steel. The metal tank is used for chemical treatments as mentioned in various steps of the process.
In accordance with the embodiments of the present disclosure, the piezo transducer is made of a material selected from ceramic and lead zirconium titanate. Piezo transducer converts the electrical energy into mechanical energy and vice versa.
The movement of piezo transducer at the bottom or the side of the metal tank creates a compression wave in a liquid contained in the tank. By using an electrical generator, the transducer rapidly induces compression and rarefaction waves in the liquid. During the rarefaction cycle the liquid is torn apart. This creates a vacuum cavity within the liquid. These cavities will grow larger and smaller as the compression waves are continued. When the cavity reaches a certain size (based on the frequency and the wattage of the signal) the cavity can no longer retain its shape. The cavity collapses violently and creates enormous energy, temperature and pressure that impacts against whatever object is in the tank. There are millions of these bubbles created that collapses every second in an ultrasonic tank. These bubbles are small and capable of removing surface dirt and contaminants. The higher the frequency, the smaller the nodes between the cavitation points, which allows for cleaning in more intricate detail.
Determination of the cleaning efficiency of the filter:
For estimating the cleaning efficiency of the filter, a flow test rig is assembled as illustrated in the Fig. 3 mimicking the actual plant operating conditions. Fig. 3 illustrates an instrument for determination of differential pressure, wherein 501 is ½” connection for digital manometer, 505 is pipe size 4” 150# rating, 507 is blind flange 150# rating, 509 is rotameter for flow measurement, 511 is 1” globe valve
513 is 1” instrument air, and 514 is vent to atmosphere. Instrument air is flowed from outside to inside the filter element. The top of the filter is kept open to atmosphere to allow the instrument air to pass through the filter. To test the filters, instrument air used at the flow rate of the actual operating conditions and pressure differential across the filter elements is measured. This measurement of the differential pressure is measured before and after cleaning of the filters.
A typical standard operating procedure for testing of the filters comprises:
• pressure enclosure capable of housing filter
• air flow meter is set 0 to 30 m3/hour to simulate at actual conditions of syngas in gasification plant
• one liquid filled pressure gage having pressure in the range of 0 to 2 kg/cm2 (if testing for used elements)
• one Electronic manometer to measure pressure drop in the range 0 to 150 mbar (for cleaned filters)
• filter headpiece to allow independent flow testing of filter
• air supply pressure 6 to 8 kg/cm2 (sufficient air pressure to be ensured for constant flow conditions)
• needle valve to allow fine control of flow
• upper and lower filter element gaskets
• upper filter element gasket washer
• flange gasket
The foregoing description of the embodiments has been provided for purposes of illustration and not intended to limit the scope of the present disclosure. Individual components of a particular embodiment are generally not limited to that particular embodiment, but, are interchangeable. Such variations are not to be regarded as a departure from the present disclosure, and all such modifications are considered to be within the scope of the present disclosure.
The present disclosure is further illustrated herein below with the help of the following experiments. The experiments used herein are intended merely to facilitate an understanding of the ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the experiments should not be construed as limiting the scope of embodiments herein.
EXPERIMENTAL DETAILS
A process for cleaning of a char filter in accordance with the present disclosure
General procedure: Cleaning experiments were carried out by soaking the used char filter with various combinations of solvent, acid, alkali mixtures, and ultra-sonicating followed by drying to achieve the desired differential pressure <20 mbar without affecting the metallurgical properties. However, the cleaned filter with differential pressure <30 mbar can be used further.
The used char filters used in each of the following examples are different from each other.
Example 1
Step (i): A char filter was vacuumed at 35 oC for 10 minutes to obtain a vacuumed filter.
Step (ii): The vacuumed filter was soaked in a first aqueous solution comprising 5% citric acid at 30 oC for 105 minutes to obtain a partially soaked filter.
Step (iii): The partially soaked filter was soaked in a second aqueous solution comprising 5% NaOH at 60 oC for 120 minutes to obtain a soaked filter.
Step (iv): The soaked filter was rinsed with water to obtain a rinsed filter.
Step (v): The rinsed filter was purged with air at 7 bar for 10 minutes to obtain a purged filter.
Step (vi): The purged filter was sonicated in a third aqueous solution comprising 5% citric acid, and 1.5% sodium stearate (surfactant) at 35 oC for 90 minutes to obtain a pre-treated filter.
Step (vii): The pre-treated filter was sonicated in a fourth aqueous solution comprising 1.5% anti-corrosive agent at 40 Hz and at 35 oC for 90 minutes to obtain a treated filter. The anti-corrosive agent used was a combination of tri ethanol amine (TEA), mono ethanol amine (MEA) and Rodine-92BTM.
Step (viii): The treated filter was dried in hot air at 90 oC for 60 minutes under vacuum to obtain a cleaned char filter.
Example 2
Another/different used char filter was used for this example. Steps (i) to (vii) were performed same as given in example 1, except in step (viii), the treated filter was dried in hot air at 70 oC for 30 minutes under vacuum to obtain a cleaned char filter.
Example 3
Another used char filter was used for this example. Steps (i) to (v), and step (vi) were performed same as given in example 1, except in step (vi), the third aqueous solution comprises 5% phosphoric acid, and 1.5% surfactant, and in step (viii) the treated filter was dried in hot air at 70 oC for 30 minutes, without applying vacuum.
Example 4
Another used char filter was used for this example. Steps (i) to (v), were performed same as given in example 1. Except, in step (vi), the third aqueous solution comprises 5% phosphoric acid, and 1.5% surfactant; in step (vii) the anticorrosive agent used was a combination of tri ethanol amine (TEA) and Rodine-92BTM, and in step (viii) the treated filter was dried in hot air at 70 oC for 30 minutes, without applying vacuum.
Example 5
Another used char filter was used for this example. Steps (i) to (vi), were performed same as given in example 1. Except, in step (vii), the anticorrosive agent used was a combination of MEA and Rodine-92BTM, and in step (viii) the treated filter was dried in hot air at 70 oC for 30 minutes, without applying vacuum. Furthers, step (ii) to (vii) were repeated once.
Example 6
Another used char filter was used for this example. Steps (i) to (v), were performed same as given in example 1. Except, in step (vi) the third aqueous solution had 5% phosphoric acid, and 1.5% surfactant, and in step (viii) the treated filter was dried in hot air at 70 oC for 30 minutes, without applying vacuum. Step (vii) was not performed, and steps (ii) to (vi) were repeated once.

Example 7
Another used char filter was used for this example. Steps (i), (iii) to (v), were performed same as given in example 1. Except, in step (vi), the third aqueous solution had 5% citric acid and 1% isopropyl alcohol, and in step (viii) the treated filter was dried in hot air at 70 oC for 30 minutes, without applying vacuum. Steps (ii) and (vii) were not performed. Steps (iii) to (vi) were repeated twice.
Example 8
Another used char filter was used for this example. Steps (i), (iii) to (v), were performed same as given in example 1. Except, in step (vi), the third aqueous solution had 5% phosphoric acid, and 1.5% surfactant, and in step (viii) the treated filter was dried in hot air at 70 oC for 30 minutes, without applying vacuum. Steps (ii) and (vii) were not performed. Steps (iii) to (vi) were repeated twice.
Example 9
Another used char filter was used for this example. Steps (i), (iv) to (v) were performed same as given in example 1. Except, in step (iii), the second aqueous solution was 5% sodium carbonate solution, in step (vi) the third aqueous solution had 5% phosphoric acid, and 1.5% surfactant, and in step (viii) the treated filter was dried in hot air at 70 oC for 30 minutes, without applying vacuum. Steps (ii) and (vii) were not performed. Steps (iii) to (vi) were repeated twice.
Example 10
Another used char filter was used for this example. Steps (i), (iv) to (v) were performed same as given in example 1. Except, in step (iii), the second aqueous solution was a solution having a combination of 5% sodium hydroxide and 2% EDTA; in step (vi) the third aqueous solution had 5% phosphoric acid, and 1.5% surfactant; and in step (viii) the treated filter was dried in hot air at 70 oC for 30 minutes, without applying vacuum. Steps (ii) and (vii) were not performed. Steps (iii) to (vi) were repeated twice.
The experimental cleaning procedure and air flow test results are shown in Table 2 and Table 3 respectively.
TABLE 2: The process steps involved in cleaning of char contaminated char filter
Step Process Temperature (oC) Duration
(in minutes)
(i) Vacuum cleaning the filter for loosening or dislodging surface char particles 30 to 40 5 to 15
(ii) Soaking in the first aqueous solution containing acid, and optionally surfactant 20 to 40 30 to 180
(iii) Soaking in the second aqueous solution containing alkali, and optionally additive 50 to 60 100 to 150
(iv) Rinsing with water 30 to 40 10
(v) Air purging at 3 to 10 bar 30 to 40 10
(vi) Sonicating in the third aqueous solution containing acid, optionally solvent and optionally surfactant 30 to 40 60 to 120
(vii) Sonicating in the fourth aqueous solution containing anti-corrosive agent and optionally acid 30 to 40 60 to 120
(viii) Drying with clean, hot air 60 to 100 20 to 70

The cleaning efficiency of the char filter was achieved for the desired differential pressure and respective results are shown in Table 3.
TABLE 3: Differential pressure measurements prior and after cleaning for examples 1 to 10
Example no. Differential pressure before cleaning (mbar) Differential pressure after cleaning (mbar) at 30 m3/h
New char filter (Reference) 5.2 -
1 475 08
2 460 12
3 455 20
4 445 26
5 470 27
6 465 29
7 490 30
8 460 28
9 480 27
10 450 32

The cleaning process for the char filter of pet coke gasification unit using ultra-sonication as disclosed herein was able to achieve a differential pressure less than 20 mbar. With the process of the present disclosure, the differential pressure was brought down to <20 mbar.
Corrosion was observed during the process of examples 7 to 10. By careful optimization of cleaning steps such as sonication and treatment with anti-corrosion agents, it was possible to avoid corrosion as these filters were highly susceptible to corrosion due to high Fe content. Internal or surface corrosion was avoided after optimized cleaning in experiments 1 to 4 and no corrosion observed even after 6 to 12 weeks.
N2 permeability and metallurgical properties such as material of construction (MOC) and radial crushing strength of the char filter cleaned as per examples 1 to 10 are shown in Table 4.
TABLE 4: Permeability, elemental analysis and crushing strength of the char filter after cleaning

Experimental details Frazier Permeability
(Cubic ft./sq. foot-s)$ EDX Elemental Analysis Radial Crushing Strength, MPa
Fe
(wt%) Al
(wt%) Cr
(wt%)
Reference filter (unused new filter) 12.11 78.92 15.83 5.25 82.91
Example 1 10.2 78.64 14.92 6.44 76.4
Example 2 10.1 70.61 23.89 5.50 83.27
Example 5 9.6 77.55 17.39 5.06 79.03
Example 6 9.5 79.46 15.27 5.27 87.00
Example 7 9.2 76.00 17.54 6.45 70.84
Example 8 9.0 75.47 18.92 5.61 80.78
Frazier Permeability refers to a resistance of a material to the passage of air; EDX: Energy Dispersive X-ray; $Permeability of filter media is determined by using ASTM D737.
The mechanical strengths of the char filter cleaned by using the process of the present disclosure for the examples 1 to 10 were as desired. The filters were intact (without damaging the structural and mechanical properties of the cleaned filter) after the cleaning processes as given in examples 1 to 10. The results of Radial Crushing Strength showed that all the cleaned char filter meet the specified requirements of > 50 MPa. The data meets the requirements as per the desired process specifications and also comparable with new reference char filter.
There was 10% to 20% reduction in permeability in comparison to the reference filter. Less than 40% reduction in permeability was anticipated as the char filter was already used in the commercial plant for 200 to 300 days.
Pore size measurements by using the methods such as bubble point, mean pore diameter of the filter, bubble pressure and pore size distribution analysis were also carried out to validate the cleaning efficiency of the char filter as shown in Table 5.
TABLE 5: Bubble pressure, bubble point and mean pore diameter measurements of the cleaned char filter
Experimental details Bubble pressure
(psi) Mean pore diameter (µm)* Bubble Point (µm)*
Desired specifications =0.29 6 to 12 17 to 23
Reference filter (new unused filter) 0.29 12.0 22.9
Example 1 0.32 10.58 19.76
Example 2 0.33 10.84 19.08
Example 3 0.34 9.51 18.71
Example 4 0.36 10.5 17.72
Example 5 0.34 9.69 18.61
Example 6 0.34 9.24 18.43
Example 7 0.34 8.19 18.36
Example 8 0.33 9.4 19.12
* Mean pore diameter and bubble point was measured by using ASTM D6767 and ASTM F316, respectively.
All pore size data of the char filter of examples 1 to 8 met the desired specifications post cleaning (the general pore size distribution can be in the range of 2.5 microns to 25 microns). Therefore, the process of the present disclosure is efficient.
TECHNICAL ADVANCEMENTS
The present disclosure described hereinabove has several technical advantages including, but not limited to, the realization of a process for cleaning a char filter, that:
• reduces the differential pressure to less than or equal to 20 mbar;
• cleans the delicate and complex shape of the filter in short time without damaging the material geometry; and
a device for cleaning filters, that:
• is efficient to clean char filter of a size.
Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the disclosure to achieve one or more of the desired objects or results.
Any discussion of documents, acts, materials, devices, articles or the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.
The foregoing disclosure has been described with reference to the accompanying embodiments which do not limit the scope and ambit of the disclosure. The description provided is purely by way of example and illustration.
The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
The foregoing description of the specific embodiments so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.
Any discussion of materials, devices, articles or the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.
While considerable emphasis has been placed herein on the components and component parts of the preferred embodiments, it will be appreciated that many embodiments can be made and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other changes in the preferred embodiment as well as other embodiments of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation. ,CLAIMS:WE CLAIM:
1. A process for cleaning a char filter, said process comprising the following steps:
(i) vacuuming a char filter to obtain a vacuumed filter;
(ii) soaking said vacuumed filter in a first aqueous solution for a first predetermined time period to obtain a partially soaked filter, wherein said first aqueous solution comprises a predetermined amount of at least one first acid, and optionally at least one first surfactant;
(iii) soaking said partially soaked filter in a second aqueous solution at a temperature in the range of 50 oC to 70 oC for a second predetermined time period to obtain a soaked filter, wherein said second aqueous solution comprises a predetermined amount of at least one alkali, and optionally at least one additive;
(iv) rinsing said soaked filter with water to obtain a rinsed filter;
(v) purging said rinsed filter with air at a predetermined pressure to obtain a purged filter;
(vi) sonicating said purged filter in a third aqueous solution at a first predetermined frequency for a third predetermined time period to obtain a pre-treated filter, wherein said third aqueous solution comprises a predetermined amount of at least one second acid, optionally at least one solvent, and optionally at least one second surfactant;
(vii) sonicating said pre-treated filter in a fourth aqueous solution at a second predetermined frequency for a fourth predetermined time period to obtain a treated filter, wherein said fourth aqueous solution comprises a predetermined amount of at least one anti-corrosive agent, and optionally at least one third acid; and
(viii) drying said treated filter in hot air under vacuum to obtain a cleaned char filter.

2. The process as claimed in claim 1, wherein in step (ii)
(a) said predetermined amount of said first acid is in the range of 1 mass% to 20 mass% with respect to the total mass of said first aqueous solution; and
(b) said predetermined amount of said first surfactant is in the range of 0 mass% to 10 mass% with respect to the total mass of said first aqueous solution.
3. The process as claimed in claim 1, wherein in step (ii), said first predetermined time period is in the range of 30 minutes to 180 minutes.
4. The process as claimed in claim 1, wherein in step (iii)
(a) said predetermined amount of said alkali is in the range of 1 mass% to 20 mass% with respect to the total mass of said second aqueous solution; and
(b) said predetermined amount of said additive is in the range of 0 mass% to 5 mass% with respect to the total mass of said second aqueous solution.
5. The process as claimed in claim 1, wherein in step (iii), said second predetermined time period is in the range of 100 minutes to 150 minutes.
6. The process as claimed in claim 1, wherein in step (v), said predetermined pressure of air is in the range of 3 bars to 10 bars.
7. The process as claimed in claim 1, wherein in step (vi)
(a) said predetermined amount of said second acid is in the range of 0.5 mass% to 10 mass% with respect to the total mass of said third aqueous solution;
(b) said predetermined amount of said solvent is in the range of 0 mass% to 5 mass% with respect to the total mass of said third aqueous solution; and
(c) said predetermined amount of said second surfactant is in the range of 0 mass% to 10 mass% with respect to the total mass of said third aqueous solution.
8. The process as claimed in claim 1, wherein in step (vi)
(a) said first predetermined frequency is in the range of 20 kHz to 60 kHz; and
(b) said third predetermined time period is in the range of 60 minutes to 120 minutes.
9. The process as claimed in claim 1, wherein in step (vii)
(a) said predetermined amount of said anti-corrosive agent is in the range of 0.01 mass% to 2 mass% with respect to the total mass of said fourth aqueous solution; and
(b) said predetermined amount of said third acid is in the range of 0 mass% to 20 mass% with respect to the total mass of said fourth aqueous solution.
10. The process as claimed in claim 1, wherein in step (vii),
(a) said second predetermined frequency is in the range of 20 kHz to 60 kHz; and
(b) said fourth predetermined time period is in the range of 60 minutes to 120 minutes.
11. The process as claimed in claim 1, wherein in step (viii), said hot air has a temperature in the range of 50 oC to 100 oC.
12. The process as claimed in claim 1, wherein said first acid, said second acid and said third acid are same or different, and are independently selected from the group consisting of citric acid, formic acid, acetic acid, nitric acid and phosphoric acid.
13. The process as claimed in claim 1, wherein said alkali is selected from the group consisting of sodium hydroxide, sodium carbonate, potassium hydroxide, calcium hydroxide, magnesium hydroxide, ammonium hydroxide, and potassium borohydride.
14. The process as claimed in claim 1, wherein said solvent is selected from the group consisting of methanol, ethanol, propanol and isopropanol.
15. The process as claimed in claim 1, wherein said first surfactant and said second surfactant are same or different, and are independently selected from the group consisting of sodium stearate, 4-[5-dodecyl] benzene sulfonate, dioctyl sodium sulfosuccinate, alkyl ether phosphates, and perfluorooctanesulfonate.
16. The process as claimed in claim 1, wherein said anti-corrosive agent is selected from the group consisting of Rodine-92BTM, sodium nitrite, calcium nitrite, sodium benzoate, tri ethanol amine (TEA), mono ethanol amine (MEA), di ethanol amine (DEA), methyl di ethanol amine (MDEA), di ethyl hydroxyl amine (DEHA), di ethyl amino ethanol amine (DEAE), tri sodium phosphate (TSP), and cyclo hexyl amine (CHA).
17. The process as claimed in claim 1, wherein said anti-corrosive agent is combination of Rodine-92BTM, mono ethanol amine (MEA) and tri ethanol amine (TEA).
18. The process as claimed in claim 1, wherein said additive is selected from the group consisting of urea, ethylene diamine tetra acetic acid (EDTA) and hydrogen peroxide.
19. The process as claimed in claim 1, wherein said cleaned char filter is characterized by having
• differential pressure in the range of 5 mbar to 30 mbar;
• Frazier nitrogen permeability in the range of 6.0 ft3/s/ft2 to 11 ft3/s/ft2;
• radial crushing strength in the range of 75 MPa to 90 MPa;
• bubble pressure in the range of 0.30 psi to 0.38 psi;
• mean pore diameter in the range of 9 µm to 12 µm; and
• bubble point in the range of 17 µm to 20 µm.
20. A device for cleaning a char filter, said device comprises:
(a) at least one metal tank configured to hold said filter;
(b) at least one piezo transducer being bonded to a bottom side of said metal tank and/or at least one side of said metal tank; and
(c) an electrical generator configured to generate an electrical signal of a predetermined frequency;
wherein,
said at least one piezo transducer is configured to change said predetermined frequency instantly when excited by the electrical signal; and
size of said at least one metal tank is selected based on the size of said filter.
21. The device as claimed in claim 20, wherein said predetermined frequency is in the range of 20 kHz to 60 kHz.
22. The device as claimed in claim 20, wherein said metal tank is made of a stainless steel.
23. The device as claimed in claim 20, wherein said piezo transducer is made of a material selected from ceramic and lead zirconium titanate.

Dated this 13th day of July, 2024

_______________________________
MOHAN RAJKUMAR DEWAN, IN/PA – 25
OF R. K. DEWAN & CO.
AUTHORIZED AGENT OF APPLICANT

TO,
THE CONTROLLER OF PATENTS