FIELD OF INVENTION:
The invention relates to a system of regenerating ceramic candle type filters used in pressurized fluidized bed gasification process for removing solid particles from hot synthesis gas. The invention depicts the method, mechanism and mechanical arrangement of process, which uses axial movement of metallic meshes placed over ceramic filters.
BACKGROUND OF INVENTION:
Gasification is a process that converts organic or fossil fuel such as coal into carbon fuel gas along with particulates in the presence of controlled amount of oxygen and steam in a reactor called Gasifier. The resulting gas mixture is called syngas (from synthesis gas or synthetic gas) or producer gas and is itself a fuel. Selection of gasification process is dictated by the type and characteristics of the fuel, its reactivity and the process requirements. Basic generic classification of the gasification processes, based primarily on the method of contact between fuel and gasification medium (air/oxygen and steam), are: moving bed, fluidized bed and entrained flow gasification.
Pressurized Fluidized Bed Coal Gasification is one of the preferred methods to convert high ash coal into fuel gases. The pressurized fluidized bed process is especially suited for conversion of high ash coals having high ash content, such as coals containing ash content in the range of 25% to 50%. The produced fuel gas which basically contains Carbon Monoxide(CO) and Hydrogen(H2} usually fired in Gas Turbine to produce power or used for making useful chemical products like Methanol, Methane, Gasoline etc.
The outlet fuel gas from the pressurized fluidized bed gasifier contains not anfc fuel gases like Hydrogen (H2), Carbon Monoxide (CO) and Methane (CH4) but

also other components along with particulates. There are limitations on particulates for firing in gas turbine combustor as well as using as feedstock in coal chemicals application. Hence, it is very much essential to remove particulates from the fuel gas.
The technologies currently used for particulate removal could be broadly classified in to dry gas cleaning or dry gas collectors like cyclone separators, barrier filters, electrostatic precipitators and wet gas cleaning or wet scrubbers (spray towers, cyclone spray scrubbers, venturi scrubbers and packed bed scrubbers).
Dry gas cleaning can be divided in to hot gas cleaning with heat resistant filter at gas temperature near 400°C and dry gas cleaning in fabric filters below 200°C. Hot gas cleaning is important for gas utilization at high temperatures (gas turbine and Coal to Chemical applications) and to lower the particulate load in the heat exchangers during cooling. Dry gas cleaning at lower temperature (below 200°C) is mostly used for low temperature synthesis gas application like internal combustion engine.
In barrier filter, gases are separated from dispersed particles by passing it through ceramic filter "medium" with a large surface area. Particles that are not able to penetrate the medium will be retained on its surface, forming the so called "filter cake". The accumulated filter cake need to remove as soon as it reached to set level in order to avoid higher pressure drop across gas stream. The accumulated filter cake is removed from the filter element generally by employing blow back forces.
European patent EP2633894A1 describes a hot gas filtration system comprising a filter vessel comprising at its raw gas section a raw gas inlet and at its clean gas section a clean gas outlet, a tube sheet separating the interior

of filter vessel into a raw gas section and a clean gas section along with blowback arrangement for regenerating the filter elements.
US patent US 20020014156A1 describes a method and apparatus for cleaning pipe shaped filter elements arranged in a housing including a separation Wall dividing the housing into a clean gas space and a raw gas space into Which the filter elements extend from the clean gas space through the separation Wall and the raw gas is directed from the raw gas space through the filter elements into the clean gas space While dust is removed from the raw gas and collected on the filter elements, the filter elements are cleaned from time to time by supplying momentarily pressurized flushing gas to the clean air space Which, at the same time, is closed to generate a flushing gas pulse providing for a backflow of clean gas from the clean gas space to the raw gas space, Which dislodges dust collected on the filter elements.
US patent US20130312329A1 describes a mechanical filter system like ceramic filters along with filter regeneration process comprises of filter heating system and reverse air back pulse to clean the filter assembly.
European patent EP2169191A1 describes a method of regenerating filter by using a pulse generating device which produces at least one electric arc discharge pulse and thereby at least one pressure wave for dislodging the particulate material including soot, and other particulate materials trapped by the filter including ash.
US Patent US4812149 describes filter regeneration arrangement based on blowback gas. US patent US4343631 describes about filtration system and its regeneration system based on back pulse of clean air.

US Patent US005395409A describes a dust collecting apparatus wherein a plurality of elongate filter elements are periodically cleaned by a reverse pulse cleaning system which directs a reverse pulse of air through the open end of each filter element so as to remove contaminants which have collected on its external surface.
US patent US3798878 describes the invention relates to improvements in the self cleaning apparatus of dust filters comprising a plurality of porous filtering bags which are each periodically backwashed by the application of a jet or burst of clean gas in a manner to cause accumulated dust particles and solids to be removed from the porous bag surface.
US Patent US4661131 discloses pleated paper barrier type air filter elements having planar filter panels that are cleaned by a reverse air jet cleaning system which ̒includes one or more specifically shaped cleaning air manifolds or heads in which a plurality of jet nozzles or ̒orifices are arranged in a predetermined pattern to provide a totally enveloping air jet which is discharged into a flow tube immediately downstream of the clean air flow chamber of a generally tubular filter element.
US Patent US4909813 invention relates in general to pressure filters of the type in which a gas is purified by the passage thereof through a tubular filter element, and it relates more particularly to a new and improved method and apparatus for removing a filter cake from the outer surface of a tubular filter element by directing a high velocity stream of gas in a reverse direction through the filter element.
US Patent US3436899 describes the injection of a high energy gas into the interior of a porous filter bag, which gas is accelerated to a supersonic speed and forms waves or vibrations in the flexible bag surface to discharge

accumulated solids.US Patent US3499268 describes an improvement in the apparatus for forming the high energy gas wave in a manner which increases the high pressure backwash cleaning force.
In all the prior art mentioned above, none of the arts describes filter cake removal method using axially moving metallic mesh over ceramic filter.
Problems for high temperature gas cleaning processes will occur if the separated dust particles cannot be removed during the filter cleaning cycle from the surface of the filter medium. In principle, two main effects may affect the removal of the dust from the filter, the separated particles may not agglomerate to form a consistent dust cake which could be easily removed by pulse jet cleaning from the filter medium and settled into a dust bin, but would instead remain in the gas and finally return to the filter's surface. This would cause a steady increase of the amount of particles on the filter and thus of the pressure drop. Also, the particles which build the dust cake on the filter medium's surface may sinter or stick as fast together or may adhere on the filter medium not allowing a removal by pulse jet, back flow and possibly not even by rigorous use of mechanical forces. Both effects are well-known from conventional filter processes operating up to about 400°C.
Whereas problems with non-agglomerating particles might be overcome by means of other more expensive cleaning techniques for the filter medium than pulse jet cleaning, the sticking or sintering of particles will usually make it necessary to use other gas cleaning processes, for instance wet scrubbers which may operate under these conditions. The change of the gas process as a whole, however, offers in general no alternative to filters for hot gas clean-up, because at present no other high temperature dust separator does work as successfully as barrier filters do. Generally in barrier filters where ceramic candle filters are used to separate solids from gas stream, filter cake forms over

ceramic filters and beyond certain limit of filter cake, further filtration makes difficult in terms of pressure drop and filter elements breakdown. Conventionally filter cake is removed from ceramic filters using blowback gas process where there is a requirement of blow back gas.
SUMMARY OF THE INVENTION:
The invention teaches about a fluidized bed gasification system in which high ash coals such as coals used as raw material to produce fuel gas. The fluidized bed gasifier uses Coal, Steam and Air as raw materials in a pressurized fluidized bed reactor (gasifier) which operates at high temperatures such as 10000 C and pressure about 30 bar. The outlet gas stream of Fluidized Bed Gasifier contains fuel constituents viz Hydrogen (H2), Carbon Monoxide (CO), Methane (CH4) along with particulates (solid particles). The fuel gas can be used to produce power or chemical products after cleaning the gas with respect to particulates and other contaminants. Best suited solids removal system at temperature range of 4000 C and in terms of keeping fuel gas heat content intact is hot gas filtration by using ceramic or metallic filter elements. Ceranuc filtration system is cheapest one when compared to metallic filters.
The method comprises of metallic mesh over the hanging ceramic candle filters. All the metallic meshes are connected to a metallic mesh tube sheet which places just below the main ceramic filter tube sheet. A rotating corrugated metallic shaft is used to move metallic mesh tube sheet vertically such that all the metallic meshes move up and down. An electric motor is used to rotate the corrugated metallic shaft. The corrugated metallic shaft is placed below the metallic mesh tube sheet and supported by mechanical seal at one end and shaft fitting wall bracket internal socket welded on filter vessel inside wall at another end. The rotating corrugated metallic shaft makes up-down movement in metallic mesh tube sheet. The up-down movement of metallic mesh eventually moves all metallic meshes in axial direction. The axial movement of

metallic meshes over ceramic filters removes filter cake. The proposed method acts as alternative for pulse jet and blow back regenerative methods. The current inventive method is cheapest compared to blow back as it avoids back gas requirement. The current invention easily breaks the continuous filter cake formation between filter elements so that pressure drop increase across filter element is avoided.
OBJECTS OF THE INVENTION:
An object of the invention is to propose a ceramic candle filter regeneration or filter cake removal system which avoids blow back gas requirement.
Another object of the current invention is to find out an alternative filter regenerative system which protects the ceramic candle filters.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
It is to be noted, however, that the appended drawings illustrate only typical embodiments of the present subject matter and are therefore not to be considered for limiting of its scope, for the invention may admit to other equally effective embodiments. The detailed description is described with reference to the accompanying figures. In the figures, the left-most digit (a) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the figures to reference like features and components. Some embodiments of system or methods in accordance with embodiments of the present subject matter are now described, by way of example, and with reference to the accompanying figures, in which: Figure 1 shows the mechanical arrangement of overall invented method of cleaning filter cake by axial movement of metallic mesh over ceramic filter.

Figure 2 shows the detailed arrangement of tube sheets, coil suspension, shaft
and supports.
Figure 3 shows the details of corrugated metallic shaft arrangement.
The invention will now be described in detail in an exemplary embodiment as depicted in the accompanying drawings. There can however be other embodiments of the same invention, all of which are deemed covered by this description.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS:
Figure 1 shows the mechanical arrangement of overall invented method of cleaning filter cake by axial movement of metallic mesh over ceramic filter.
Ceramic filters (1) in the form of candles vertically suspended from a ceramic filter tube sheet (4) which separates raw gas zone and clean gas zone in a closed pressure vessel called filter vessel. Metallic mesh (2) wears over the ceramic candle filter. Five millimeters distance is selected between the ceramic filter outer diameters to inside diameter of metallic mesh in the current art which is crucial for avoiding erosive action of metallic mesh over ceramic filter and radial hitting of metallic mesh on ceramic filter. Metallic mesh elements over all the ceramic filters connects to metallic mesh tube sheet (3) by welding or nut bolt connection of all the metallic mesh top circumferences to metallic mesh tube sheet. Metallic mesh tube sheet places below the ceramic filter tube sheet and supported on a simple support structure elements (7) welded to inside filter vessel wall. The diameter of the metallic mesh tube sheet is set at a value less than ceramic filter tube sheet and also less than the filter vessel inner diameter such that metallic mesh tube sheet freely moves only in vertical direction. All the metallic meshes around ceramic filters moves axially whenever vertical movement occurs on metallic mesh tube sheet as they are

connected to metallic mesh tube sheet by welding or nut bolt. Ceramic filter tube sheet is connected firmly to filter vessel whereas metallic mesh tube sheet is placed or supported on simple support structure inside filter vessel. Coil suspension (6) are placed in the circumferential space between fixed ceramic filter tube sheet and metallic mesh tube sheet in order to facilitate smooth vertical movement of metallic mesh tube sheet. A corrugated metallic shaft (5) is used to move metallic mesh tube sheet vertically. The metallic shaft rotates using an electric motor (14) placed outside of filter vessel through a coupling (13). The metallic shaft is made up of three half cylindrical corrugations (9) axially on a central cylindrical shaft circumference at 120 degree angle. The metallic shaft is placed below the metallic mesh tube sheet at radial diameter and the distance is in such a way that the metallic shaft non-corrugated surface touches the metallic mesh tube sheet. The metallic shaft is connected to filter vessel wall (11) by Mechanical Seal (10) at driving end and shaft fitting wall bracket internal socket (8) at non-driving end. At driving end, the metallic shaft outside filter vessel (12) portion comes out through a mechanical seal and coupled to an electric motor which rotates the metallic shaft. The mechanical seal is provided with pressurized barrier fluid. At non-driving end, the metallic shaft is fixed in a shaft fitting wall bracket internal socket which is welded to filter vessel inside wall (15).
The metallic meshes over ceramic filters act as protective elements during gas filtration. During filtration start with fresh ceramic filters, metallic shaft rests at a position of non-corrugated circumference touches metallic mesh tube sheet which rests on simple support structure elements. Coil suspension in between metallic mesh tube sheet and ceramic filter tube sheet elongates metallic mesh tube sheet very close to metallic shaft non-corrugated circumference as well as simple support structure elements. As gas filtration proceeds, filter cake forms over metallic meshes. Pressure drop measurement across clean gas side and raw gas side gives a signal for filter regeneration. On

filter regeneration signal, electric motor rotates metallic shaft in set rpm. On rotation, metallic shaft half cylindrical corrugations pushes metallic mesh tube sheet upwards (vertical) and non-corrugated surface pulls back metallic mesh tube sheet to original position. The sequential action of metallic shaft corrugations makes up-down movement in metallic mesh tube sheet. The up-down movement of metallic mesh eventually moves all metallic meshes in axial direction. The axial movement of metallic meshes over ceramic filters removes filter cake. Pressure drop sensor brings back the system for filtration again.The electric motor can be coupled to pressure drop sensor or a timer based electric motor operation also makes filter regeneration. All metallic filters are inter connected with spacer rods each other at bottom in order to ensure the metallic filters verticality. The invention substitutes blow back system and blow back gas or air blow back system mentioned in all the prior arts.

WE CLAIM:
1. A filter cake removable system for a fluidized bed gasification system, the
system comprising:
- at least a ceramic candle filter (1) suspended from a ceramic filter tube
sheet (4);
- a metallic mesh (2) encapsulating the said ceramic candle filter (1), the
metallic mesh (2) and ceramic candle filter (1) maintaining a significant gap;
suspended from a metallic mesh tube sheet (4} placed horizontally below the
ceramic filter tube sheet (4);
wherein said metallic mesh tube sheet (4) is supported on a support structure element (7) welded to an inside filter vessel wall;
wherein coil suspension (6) is set up in the circumferential space between fixed ceramic filter tube sheet and metallic mesh tube sheet to facilitate smooth vertical movement of metallic mesh tube sheet;
wherein said metallic mesh tube sheet (4) bottom is coupled to a corrugated metallic shaft (5);
wherein said rotation of corrugated metallic shaft tends up-down movement in metallic mesh tube sheet(4) and initiates movement of metallic meshes in axial direction; and
wherein said axial movement of metallic meshes over ceramic candle filters (1) removes filter cake from ceramic candle filters (1).
2. The filter cake removable system as claimed in claim 1, wherein said corrugated metallic shaft below the metallic mesh (2) tube sheet (4) is so positioned that the metallic shaft non-corrugated surface is in contact with the metallic mesh tube sheet.
3. The filter cake removable system as claimed in claim 1, wherein said corrugated metallic shaft is coupled to filter vessel wall (11} by Mechanical Seal

(10) at driving end and shaft fitting wall bracket internal socket (8) welded to filter vessel inside wall (15) at non-driving end.
4. The filter cake removable system as claimed in claim 1, wherein said
corrugated metallic shaft at driving end is connected to an electric motor (14)
which rotates the metallic shaft through a mechanical seal at filter vessel wall.
5. The filter cake removable system as claimed in claimsl and 4, wherein said
electric motor rotates the corrugated metallic shaft in a predefined speed
pushing metallic mesh tube sheet upwards (vertical) and non-corrugated
surface pulls back metallic mesh tube sheet (4) to original position.
6. The filter cake removable system as claimed in claim 1, wherein as
illustrated in the accompanying drawings.