Description:‘Method for improving synthesis gas quality in oxy-blown fluidized bed gasification process with petroleum coke’

FIELD OF INVENTION:
[001] This invention relates to the fluidized bed gasification process and method of operating the gasifier in an oxy-blown mode using petroleum coke as a feed stock. More particularly, the invention relates to oxy-blown fluidized bed gasification process. Thus, the present invention is directed to Method for improving synthesis gas quality in oxy-blown fluidized bed gasification process with petroleum coke as feed stock for power generation.

BACKGROUND OF THE INVENTION/PRIOR ART:
[002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.

[003] Recently petcoke gasification has gained considerable importance as coal shortages are increasing and petcoke is a cheap fuel which is very abundantly available. Petroleum coke in general has a poorer gasification reactivity, particularly at moderate temperatures, than does bituminous coal due, for example, to its highly crystalline carbon and elevated levels of organic sulphur derived from heavy-gravity oil. There are methods available for increasing the reactivity of petcoke by using oxygen as a process media, using recycle system, also using smaller feed particle size and providing more residence time to feed particle. Petroleum coke has emerged as an economically attractive feedstock for gasification to synthesis gas ("syngas") which can be subsequently used to generate the power, methanol, ammonia, urea, nitric acid, ammonium nitrate, ammonium sulfate etc.

[004] Petcoke (petroleum coke) is a solid carbonaceous residue derived from oil refinery Coker units. Petcoke has high carbon content and low ash because of which, it could be considered as potential fuel to mitigate the dependency on coal reserves. Also in view of numerous factors such as higher energy prices and environmental concerns, the production of value- added gaseous products from lower-fuel-value carbonaceous feedstock's, such as petroleum coke, is receiving renewed attention.

[005] Petroleum coke typically has high sulphur content, and all of it is organic sulphur. Typical sulphur levels are 1-4% on a moisture-free basis. The primary consequences of sulphur level are reflected in high H2S concentrations in syngas which require larger sulphur removal systems. To capture the sulphur from the syngas, limestone is added to the in-bed to capture the SO2 from syngas.

[006] In prior art, US patent No. US20100263278A1 claimed to have a Gasification reactor and process for entrained-flow gasification of liquid or fine-grain solid fuel materials with the aid of oxygen as a process media for gasification agents in a reactor. The synthesis gas is generated in a first reaction chamber arranged in the upper part of the reactor and the feedstock is fed to the upper part.

[007] In another prior art, US20090283447A1, claimed to have an Electro-gasification of pet¬coke, including the steps of providing a pet-coke material; treating the pet-coke material to obtain a treated pet-coke material having an average particle size of between about 20 and about 106 µm to produce synthesis gas and/or hydrogen.

[008] In other prior art, US4609456A, claimed to have a process for converting heavy petroleum residues to hydrogen and to gaseous and distillable hydrocarbons, comprising the association of a step of hydro-pyrolysis (inside tube 3) with a step of catalytic steam-gasification of the formed coke (outside tube 3), characterized in that the hydro pyrolysis step is performed in the presence of a solid supporting a carbon gasification catalyst circulating between the hydro pyrolysis zone and the coke steam-gasification zone.

[009] In other prior art US20070083072A1, claimed to have a catalytic steam gasification process for gasifying petroleum coke. The solids composition within the gasification reactor of the disclosed invention is maintained by controlling the catalyst composition of the feed. The process utilizes sour water from the raw gasification product gases to recover and recycle catalyst. Fine particles generated in the handling of coke are advantageously utilized to increase the efficiency of the process.

[0010] In other prior art WO2009048724A2, claimed to have a particulate compositions of a lower ash type petroleum coke containing at least two preselected components (alkali metal and calcium) that exhibit an efficient, enhanced-yielding gasification to value added gaseous products, particularly when used in a steady-state integrated gasification process. The compositions of the present invention are particularly useful for catalytic gasification of petroleum coke at moderate temperatures ranging from about 450°C to about 900°C.

[0011] In other prior art WO1995013339A1, claimed to have a method for the gasification of a petroleum coke feedstock comprising the steps of: admixing an ash-deficient substantially dry petroleum coke feed with at least an additive component being a slag-forming material selected from the group consisting of blast furnace slag, power plant fly ash, coal gasification slag, sand, X, AI203, and Si?2, where X is a basic ash-component selected from the group consisting of CaO, CaC?3, MgO, MgC?3, iron oxides, boron oxides, sodium oxides and potassium oxides and mixtures thereof, thereby producing at least an additive component(s) /feed mixture.

[0012] The present invention focuses on improving the calorific value and carbon conversion in an oxy-blown fluidized bed gasification technology with petroleum coke as a feed stock for power generation. The present invention can overcome the drawbacks of the above mentioned prior arts.

OBJECTIVES OF THE INVENTION:
[0013] An object of the present invention is to utilize the lower-fuel-value carbonaceous feed stocks such as petroleum coke in to power production.

[0014] Another object of present invention is to enhance the calorific value of syngas generated from fluidized bed petcoke gasification by using oxygen as a gasification medium.

[0015] A further object of present invention is to enhance the carbon conversion efficiency of low reactivity petcoke in fluidized bed gasification by using recycle system.

[0016] Yet another object of present invention is to enhance the carbon conversion efficiency of petcoke in fluidized bed gasification by increasing the residence time.

[0017] Still another object of present invention is to enhance the carbon conversion efficiency of petcoke in fluidized bed gasification by using smaller feed particle size.

[0018] A still another object of the present invention is to generate the qualitative syngas with higher calorific value through fluidized bed petcoke gasification suitable to meet the inlet requirements of syngas engine for power applications.

[0019] These and other objects and advantages of the present invention will be apparent to those skilled in the art after a consideration of the following detailed description taken in conjunction with the accompanying drawings in which a preferred form of the present invention is illustrated.

SUMMARY OF THE INVENTION:
[0020] One or more drawbacks of conventional systems and process are overcome, and additional advantages are provided through the apparatus/composition and a method as claimed in the present disclosure. Additional features and advantages are realized through the technicalities of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered to be part of the claimed disclosure.

[0021] According to this invention, there is provided Method for improving the synthesis gas quality in an oxy-blown fluidized bed gasification process with petroleum coke as a feed stock for power generation. The process comprises of below steps:

[0022] The synthesis gas (syngas) is generated in fluidized bed gasifier (13) where the petroleum coke (or) petcoke size of 0 to 2 mm is used as a feed stock and is fed in to a fluidized bed gasifier using rotary feeder (9). The petcoke is stored in petcoke hopper (8), and petcoke lock (9) system.

[0023] The fluidizing medium comprising of a mixture of pure oxygen, carbon di-oxide and steam is admitted in to fluidized bed gasifier (13) through distributor. The petcoke and fluidizing medium undergo the gasification reactions in the gasifier to enhance the calorific value of syngas generated from fluidized bed petcoke gasification. A constant inventory is maintained in fluidized bed gasifier (13) and sufficient fluidizing medium flow rate is admitted to maintain the inventory in bubbling region. The oxygen from the oxygen plant (3), carbon dioxide from the carbon dioxide receiver (2) and steam from steam generator (4) is sent to the plenum and is mixed as per the required proportionate before admitted into gasifier. The ash generated after gasification and unburnt carbon in gasifier are continuously extracted from the gasifier into ash discharge system (12) using ash extractor (11).

[0024] The petcoke is gasified in a gasifier (13) at an elevated temperatures and pressures to get the good carbon conversion efficiency. To get more carbon conversion efficiency, the residence time of the feed particle has to be increased. When the residence time of the feed particle increased which in turn increases the carbon conversion efficiency.

[0025] The generated syngas is cleaned from dust particles in a cyclone-1 (14), cyclone-2 (18) and candle filter system (20). The captured ash particles are recycled back in to the gasifier (13) from cyclone-1 (14) using recycle system (16). In cyclone-1 (14), approximately 25% unburnt carbon available which is recycled to the gasifier in order to increase the carbon conversion efficiency and reduce the unburnt carbon in cyclone-1 ash.

[0026] A multiple unit of ash locks are provided at bottom of the cyclone-1 (14), cyclone-2 (18) and candle filter system (20). The ash lock (17) is provided at the bottom of the cyclone-1 (14), the ash lock (19) is provided at the bottom of cyclone-2 and another ash lock (21) is provided at the bottom of the candle filter system (20) to store the ash which is captured by cyclone-1 (14), cyclone-2 (18) and candle filter system (20). The stored fly ashes from the ash vessels are withdrawn in a predetermined period.

[0027] After removing the ash particles using series of cyclones, the cleaned syngas is sent to the gas cooler (22) for cooling the said syngas. The cooled syngas is sent to the knock out drum (23) thereafter for removing the moisture content in the synthesis gas.

[0028] Removing the dust particles and moisture content in the synthesis gas thereupon, it is passed into a syngas receiver (24) where the syngas is stored. The stoichiometric required syngas from the syngas receiver (24) is sent to the syngas engine (26) at 60 degree C through mass flow meter (25). The mass flow meter (25) measures the flow rate of synthesis gas that is sent into the said gas engine (26) for power generation.

[0029] Various objects, features, aspects, and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.

[0030] It is to be understood that the aspects and embodiments of the disclosure described above may be used in any combination with each other. Several of the aspects and embodiments may be combined to form a further embodiment of the disclosure.

[0031] The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING:
[0032] The illustrated embodiments of the subject matter will be best understood by reference to the drawings, wherein like parts are designated by like numerals throughout. The following description is intended only by way of example, and simply illustrates certain selected embodiments of devices, systems, and processes that are consistent with the subject matter as claimed herein, wherein:-

[0033] Further objects and advantages of this invention will be more apparent from the ensuing description when read in conjunction with the accompanying drawings of the exemplary embodiments and wherein:
[0034] Figure 01 shows: A flow diagram of the oxy-blown fluidized bed gasification process with petroleum coke as a feed stock for power generation.
[0035] The figures depict embodiments of the disclosure for purposes of illustration only. One skilled in the art will readily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWING:
[0036] While the embodiments of the disclosure are subject to various modifications and alternative forms, specific embodiment thereof have been shown by way of example in the figures and will be described below. It should be understood, however, that it is not intended to limit the disclosure to the particular forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternative falling within the scope of the disclosure.

[0037] The present invention makes a disclosure regarding a technology pertaining to an invention for Method for improving synthesis gas quality in oxy-blown fluidized bed gasification process with petroleum coke.

[0038] Reference may be made to Figure 01 schematically illustrating the method for improving the synthesis gas quality in an oxy-blown fluidized bed gasification process with petroleum coke as a feed stock for power generation. As shown in Figure 1, the present invention comprises of a fluidized bed gasifier (13) where the petroleum coke (or) petcoke is gasified and generates the synthesis gas or syngas. Petroleum coke of size 0 to 2 mm is used as a feed stock and is to be fed in to a fluidized bed gasifier (13) using petcoke rotary feeder (9). The petcoke size of 0 to 2 mm is stored in petcoke hopper (8), and petcoke lock (9) system. The gasification process takes place in a fluidized bed gasifier (13) by admitting petcoke from petcoke hopper (8), petcoke lock (9) and rotary feeder (10) in to the fluidized bed gasifier (13). A lime stone is added to the gasification process through sorbent hopper (5), sorbent lock (6) and sorbent feeder (7) in order to capture the in bed Sulphur concentration in syngas.

[0039] Fluidizing medium comprising of a mixture of Oxygen, Carbon di oxide and steam, which is admitted in to said fluidized bed gasifier (13) through distributor. The petcoke and fluidizing medium undergoes the gasification reactions in the gasifier. Constant inventory is maintained in fluidized bed coal gasifier (13) and sufficient fluidizing medium flow rate is admitted to maintain the inventory in bubbling fluidization condition. The oxygen from the oxygen plant (3), carbon di-oxide from the carbon dioxide receiver (2) and steam from steam generator (4) is sent to the plenum and is mixed as per the required proportionate before admiting into gasifier. The ash generated after gasification and unburnt carbon in gasifier are continuously collected from the gasifier bottom into ash discharge system (12) through ash extractor (11).

[0040] The petcoke is gasified in said gasifier (13) at an elevated temperatures and pressures to get the good carbon conversion efficiency. To get more carbon conversion efficiency, the reactivity of the petcoke has to be increased. The reactivity of thee petcoke is increased by increasing the residence time of the feed particle, using smaller size feed particle and recycling the un-burnt carbon in to gasifier. To increase the residence time of the feed particle, the gasifier (13) free board diameter has to be increased. When the gasifier (13) free board diameter is increased, the residence time of the feed particle is increased. When the residence time of the feed particle is increased, the feed particle stays more time in the gasifier and gets converted more carbon available in the petcoke. Also a very smaller particle size of petcoke has to be used and also pure oxygen as a processing media has to be used.

[0041] The generated syngas is cleaned from dust particles in a cyclone-1 (14), cyclone-2 (18) and candle filter system (20). The captured ash particles are recycled back in to the gasifier (13) from cyclone-1 (14) using recycle system (16). In cyclone-1 (14), approximately 25% unburnt carbon is available which is recycled to the gasifier in order to increase the carbon conversion efficiency and reduce the unburnt carbon in cyclone-1 ash. A multiple unit of ash locks are provided at bottom of the cyclone-1 (14), cyclone-2 (18) and candle filter system (20). The ash lock (17) is provided at the bottom of the cyclone-1 (14), the ash lock (19) is provided at the bottom of cyclone-2 and another ash lock (21) is provided at the bottom of the candle filter system (20) to store the ash which is captured by cyclone-1 (14), cyclone-2 (18) and candle filter system (20). The stored fly ashes in the ash lock (17), ash lock (19) and ash lock (21) are withdrawn in a predetermined period.

[0042] After removing the ash particles using series of cyclones, the cleaned syngas is sent to the gas cooler (22) for cooling said syngas. The cooled syngas is sent to the knock out drum (23) thereafter for removing the moisture content in the synthesis gas. Removing the dust particles and moisture content in the synthesis gas thereupon, it is passed into a syngas receiver (24) where the syngas is stored. The stoichiometric required syngas from the syngas receiver (24) is sent to the syngas engine (26) at 60 degree C through mass flow meter (25). The mass flow meter (25) measures the flow rate of synthesis gas that is sent into the said gas engine (26) for power generation.

[0043] Thus the instant invention proposes a process of enhancing the calorific value of syngas generated through fluidized bed pet coke gasification using oxygen, carbon-di-oxide and steam as fluidizing agents wherein the invention is characterized by approximately 40% increment in calorific value of syngas by increasing the oxygen weight percentage by 92% in fluidizing agent. While varying the oxygen percentage in fluidizing medium, the operating temperature in the dense fluidization bed zone is maintained in the range of 1000-10200C and fluidization operating velocity also is maintained in the range of 1.9 -2.1 m/s. In order to maintain the same operating temperature and operating velocity, the input process parameters to fluidized bed gasifier is adjusted accordingly; the pet coke flow rate is increased approximately by 25%, CO2 flow rate maintained is 42% and steam flow rate is increased by 28 %. The syngas with higher calorific value generated through above mentioned process is more suitable in meeting the syngas engine inlet conditions.

[0044] Also there is a process of enhancing the carbon conversion in a fluidized bed petcoke gasification by using the recycle system. The main purpose of recycle system is to recycle the cyclone-1 ash from cyclone-1 to fluidized bed gasifier. When the petcoke is gasified in recycle mode, the carbon conversion is increased approximately in the range of 15¬-18% compared to non-recycle mode in oxy-blown gasification. Also there is another process to enhance the carbon conversion in a fluidized bed petcoke gasification by increasing the residence time of the feed particle. The residence time of the feed particle is increased by increasing the diameter of the gasifier free board zone. By increasing the gasifier free board diameter, the residence time of the feed particle is increased. When the residence time of the feed particle increases, there is an increment of carbon conversion efficiency in oxy-blown pet coke gasification. Also there is another process to enhance the carbon conversion in a fluidized bed pet coke gasification by using the smaller particle size of the feed. When the smaller particle feed is used, the reactivity of the petroleum coke is increased which in turn increases the carbon conversion efficiency.

[0045] Each of the appended claims defines a separate invention, which for infringement purposes is recognized as including equivalents to the various elements or limitations specified in the claims. Depending on the context, all references below to the "invention" may in some cases refer to certain specific embodiments only. In other cases, it will be recognized that references to the "invention" will refer to subject matter recited in one or more, but not necessarily all, of the claims.

[0046] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description of all groups used in the appended claims.

[0047] It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particulars claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should typically be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogues to “at least one of A, B and C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a convention analogous to “at least one of A, B, or C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, or C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase “A or B” will be understood to include the possibilities of “A” or “B” or “A and B”.

[0048] The above description does not provide specific details of manufacture or design of the various components. Those of skill in the art are familiar with such details, and unless departures from those techniques are set out, techniques, known, related art or later developed designs and materials should be employed. Those in the art are capable of choosing suitable manufacturing and design details.

[0049] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. It will be appreciated that several of the above-disclosed and other features and functions, or alternatives thereof, may be combined into other systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may subsequently be made by those skilled in the art without departing from the scope of the present disclosure as encompassed by the following claims.

[0050] The claims, as originally presented and as they may be amended, encompass variations, alternatives, modifications, improvements, equivalents, and substantial equivalents of the embodiments and teachings disclosed herein, including those that are presently unforeseen or unappreciated, and that, for example, may arise from applicants/patentees and others.

[0051] While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.
, Claims:WE CLAIM:

1. Method for improving synthesis gas quality in oxy-blown fluidized bed gasification process with petroleum coke as feed stock for power generation comprising of:
- gasification of petroleum coke/pet coke in a fluidized bed gasifier (13) and generation of the synthesis gas/syngas by admitting pet coke from pet coke hopper (8), pet coke lock (9) and rotary feeder (10) in to the fluidized bed gasifier (13);
- addition of lime stone to the gasification process through sorbent hopper (5), sorbent lock (6) and sorbent feeder (7) in order to capture the in bed Sulphur concentration in syngas;
- admission of fluidizing medium comprising of a mixture of Oxygen, Carbon di oxide and steam into said fluidized bed gasifier (13) through distributor;
- collection of ash generated after gasification and unburnt carbon from the gasifier bottom;
- cleaning of the generated syngas from dust particles in a cyclone-1 (14), cyclone-2 (18) and candle filter system (20).

2. The Method for improving synthesis gas quality as claimed in claim 1, wherein the Petroleum coke of size 0 to 2 mm is used as a feed stock and is to be fed in to the fluidized bed gasifier (13) using petcoke rotary feeder (9), in which the petcoke size of 0 to 2 mm is stored in petcoke hopper (8) and petcoke lock (9) system.

3. The Method for improving synthesis gas quality as claimed in claim 1 or 2, wherein the pet coke and fluidizing medium undergoes the gasification reactions in the gasifier, in which constant inventory is maintained in the fluidized bed coal gasifier (13) and sufficient fluidizing medium flow rate is admitted to maintain the inventory in bubbling fluidization condition.
4. The Method for improving synthesis gas quality as claimed in claims 1-3, wherein the oxygen from the oxygen plant (3), carbon di-oxide from the carbon dioxide receiver (2) and steam from steam generator (4) is sent to the plenum and is mixed as per the required proportionate before admitting into the gasifier.

5. The Method for improving synthesis gas quality as claimed in claims 1-4, wherein the ash generated after gasification and unburnt carbon in gasifier are continuously collected from the gasifier bottom into ash discharge system (12) through ash extractor (11).

6. The Method for improving synthesis gas quality as claimed in claims 1-5, wherein the captured ash particles are recycled back in to the gasifier (13) from cyclone-1 (14) using recycle system (16), in which in cyclone-1 (14), approximately 25% unburnt carbon is available which is recycled to the gasifier in order to increase the carbon conversion efficiency and reduce the unburnt carbon in cyclone-1 ash, wherein a multiple unit of ash locks are provided at bottom of the cyclone-1 (14), cyclone-2 (18) and candle filter system (20).

7. The Method for improving synthesis gas quality as claimed in claim 6, wherein the ash lock (17) is provided at the bottom of the cyclone-1 (14), the ash lock (19) is provided at the bottom of cyclone-2 and another ash lock (21) is provided at the bottom of the candle filter system (20) to store the ash which is captured by cyclone-1 (14), cyclone-2 (18) and candle filter system (20), in which the stored fly ashes in the ash lock (17), ash lock (19) and ash lock (21) are withdrawn in a predetermined period.

8. The Method for improving synthesis gas quality as claimed in claims 1-7, wherein after removing the ash particles using series of cyclones, the cleaned syngas is sent to the gas cooler (22) for cooling said syngas, in which the cooled syngas is sent to the knock out drum (23) thereafter for removing the moisture content in the synthesis gas, wherein removing the dust particles and moisture content in the synthesis gas thereupon, it is passed into a syngas receiver (24) where the syngas is stored.

9. The Method for improving synthesis gas quality as claimed in claims 1-8, wherein the stoichiometric required syngas from the syngas receiver (24) is sent to the syngas engine (26) through mass flow meter (25), in which the mass flow meter (25) measures the flow rate of synthesis gas that is sent into the said gas engine (26) for power generation.