Oxygen-enriched air-blown pilot-scale pressurized fluidized bed refractory-lined gasifier.

Abstract

The present invention discloses a 1.5 ton / day oxygen enriched air blown pressurized fluidized bed pilot scale refractory lined gasifier for gasifying coal, biomass, wash rejects and mixtures thereof in any proportion in the practical environment of a commercial gasifier. The system is equipped to operate in air / oxygen / oxygen enriched air / steam and mixtures thereof in any proportion as per process requirements. The present invention provides a maximum feed capacity of 60 kg / hr, operating temperature of up to 1050°C and a maximum feed rate of 10 kg / cm. 2 The present invention discloses a gasifier having an operating pressure of 10 ...

Description

[Technical field]

[0001] The present invention relates to the development of an oxygen enriched air-blown pressurized fluidized bed pilot scale gasifier for evaluating the gasification performance of coal, biomass, wash rejects and their mixtures in any ratio. More specifically, the present invention relates to a pilot scale gasifier with a feed capacity of up to 60 kg / hr, an operating temperature of up to 1050°C and a gasification rate of up to 10 kg / cm. 2 The present invention relates to an oxygen-enriched air-blown pressurized fluidized bed gasification pilot-scale facility with a refractory-lined gasifier having an operating pressure of 10000 MPa. The facility consists of a gas and solids feed section, a gasification section, an ash recovery section, a gas cooling and purification section. In addition to gasification performance analysis, the present invention also intends to study the agglomeration characteristics, entrainment and other fluidized bed gasification related parameters. [Background technology]

[0002] In India, the vast coal stock is dominated by low quality, high ash non-coking coals. The high ash content of Indian coals is a major barrier in the development of suitable technologies. Among the available gasification technologies, entrained bed gasifiers are mature but are not recommended for high ash coals due to their huge heat losses and thermal imbalance associated with the flowing molten slag. Fixed bed gasification technologies are limited to coals with up to 30% ash and at the same time generate significant amounts of harmful tar and require large capital investments for downstream processing. Thus, utilization of high ash coals through the above mentioned technologies implies economic and environmental disadvantages in terms of beneficiation and downstream processing of the feed for various applications such as power, chemicals, fertilizer, DRI, and heat. Against these scientific and technological challenges, fluidized bed gasifiers are capable of gasifying a wide range of feed materials. It is best suited to utilize high ash coals in various applications without beneficiation to reduce ash levels, and is also excellent for handling not only biomass but also wash rejects and their mixtures in any proportion, with negligible levels of tar production, which considerably reduces downstream capital investment and operation and maintenance costs. In a fluidized bed gasifier, heat transfer between the gas and solid phases is easier since the reactants behave like fluids. However, high ash coals have some drawbacks such as low heating value, usage restrictions, and low efficiency. Agglomeration of ash particles can defluidize the bed and result in plant shutdown due to the inherent properties of some feed materials. Therefore, it is necessary to study the gasification behavior of certain coals, biomass, wash rejects and their mixtures in a fluidized bed gasifier to determine their suitability. As background to the present invention, the development of an oxygen-enriched air-blown pressurized fluidized bed gasification pilot-scale facility with a refractory-lined gasifier is relevant.

[0003] Reference may be made to U.S. Patent No. 4,968,325, issued November 6, 1990, by Black et al., in which the authors disclose a process and plant for gasifying biomass. The plant has a pressure vessel containing a hot fluidized sand bed. The biomass is pre-dried to a moisture content of 10% to 35% (by weight). A steam-free oxygen-containing gas is fed and dispersed through a grate device at the bottom of the hot sand bed to keep the bed fluidized and to form an oxygen-rich heat-producing combustion zone at its lower part and a hydrogen-rich gas-producing pyrolysis zone at its upper part. The pre-dried biomass is continuously fed into the pyrolysis zone in essentially the center of the hot fluidized bed, which is determined when the sand bed is stationary. The fluidized bed is maintained at an operating temperature of 750° C. to 860° C. under an operating pressure of 400 kPa to 1750 kPa by controlling the feed rate of the fluidizing gas and the feed rate of the biomass. The gas and biomass residue discharged from the hot fluidized bed are removed from the headspace above the bed in a gas stream and sent to a first cyclone which separates the useful gas from most of the biomass residue, which is returned to the combustion zone of the bed. The gas and biomass residue remaining in the first cyclone are then transferred to a second cyclone where the useful gas is collected and the biomass residue is discarded. The disadvantages are as follows:

[0004] This unit is for biomass only. -The maximum temperature is only 860℃. · No means are available for removing acidic components from the gas. · Preheating and depletion of gaseous reactants before they enter the gasifier is not available. - No online gas analyzer is available.

[0005] Yet another reference is US Patent No. 4,490,157, issued Dec. 25, 1984 by Fernandes, in which the author describes an indirectly heated fluidized bed gasifier. A fluidized bed gasifier for gasifying fuel first receives heat indirectly from a combustor fluidized bed that is at least partially disposed within the gasifier fluidized bed. Fuel for the combustor bed can be provided by removing a portion of the fluidized fuel from the gasification bed and transferring this removed portion to the combustor bed. Heat is transferred through the conductive wall of the combustor vessel. The heating value of the product gas is increased by separating and removing the combustion products from the gasifier and circulating a portion of the product fuel gas as fluidizing gas for the gasifier fluidized bed. A radiation shield is also provided to reduce heat loss from the gasifier bed and to remove material entrained in the product fuel gas. The disadvantages are as follows: Heat transfer from the combustion zone to the gasification zone occurs exclusively through a conducting wall placed between the two zones. · Means for pre-heating and complete de-heating of gaseous reactants before entering the gasifier are not available. - No online gas analyzer is available. -The equipment appears complex when manufacturing and operation are considered.

[0006] Yet another reference is US Pat. No. 9,181,502, dated July 8, 2013, in which the authors disclose a two-stage fluidized bed gasifier for high ash and high ash melting temperature bituminous coal, where the first stage gasifier is a circulating fluidized bed transport gasifier operating at a temperature range of about 900° C. to 1100° C., and the second stage gasifier is a fluidized bed partial oxidizer operating at a temperature range of about 1100° C. to 1400° C. The first stage gasifier serves as the primary gasifier, converting up to 90% of the carbon with some tar into syngas components. The residual char carbon and tar from the gasifier are then pyrolyzed in the second stage high temperature fluidized bed oxidizer and converted into syngas components. The two-stage process can convert more than about 98% of the total carbon into syngas components. However, this device is only for high ash and high ash melting temperature bituminous coals, and from the manufacturing and operation considerations, the device appears to be complicated, and no on-line gas analysis of the product gas is provided.

[0007] Yet another reference is China Patent Application No. 201610944225, which discloses a technology for coal gasification by bubbling fluidized bed. The technology includes the steps of coal grinding and drying, coal pressurization and coal feeding, coal gasification, coarse dedusting by cyclone separation, waste heat recovery, fine dedusting purification of syngas, and clinker treatment. However, this device is only intended for coal gasification. Other feed materials such as biomass / coal-biomass mixture cannot be utilized in this device. There is also no provision for online gas analysis.

[0008] Yet another reference is US Patent Application No. 05868959, which relates to a method of operating a fluidized bed apparatus combining a dense fluidized bed and an entrained fluidized bed, the bed containing particulate components having long-term chemical and physical stability in the apparatus, some particulate components being retained in the dense fluidized bed and other particulate components being entrained and recirculated through a portion of the dense bed to increase the residence time and promote a more complete reaction of the reactant feed particles therein. In particular, the invention relates to the operation of a seamless multiplex apparatus in which the dense bed is operated in two separate temperature zones for optimal control of the combustion or gasification of the fuel and the capture of the released sulfur by the added sorbent. With minor modifications, the method is utilized for both the combustion and gasification of high sulfur coal. However, it is of the circulating fluidized bed type and is used only for coal. To maintain two reaction zones in the reactor, the operation of the apparatus is very complicated.

[0009] Yet another reference is US Patent Application No. 10451727, which relates to a method and an apparatus for effectively utilizing the thermal energy of the hot combustion gas discharged from the combustor and for utilizing the hot oxygen contained in the hot combustion gas discharged from the combustor. A fluidized bed gasifier for gasifying combustibles in a fluidized bed furnace comprises a gasifier furnace in which the combustibles are gasified and a combustion furnace in which the combustible components are burned. The fluidized medium moves between the gasifier furnace and the combustion furnace, and the exhaust gas discharged from the other combustor is used as the fluidizing gas in the combustion furnace. It works on the principle of a two-part fluidized bed. No online gas analysis, no preheating of the reactants is shown. The operating principle is also complex.

[0010] Yet another reference is the publication by Engelbrecht et al. (Industrial Fluidization South Africa, pages 145-160, published by A. Luckos & P. ​​den Hoed Johannesburg, Southern African Institute of Mining and Metallurgy, 2011), where the authors report on the fluidized bed gasification of high ash South African coals in a pilot-scale bubbling fluidized bed gasifier with a coal feed rate capacity of 15 to 35 kg / h at atmospheric pressure. Coal feeding / unloading is performed using a screw feeder. However, this equipment is developed only for coal gasification and no two-part feeding device with a rotary feeder and a screw feeder is presented.

[0011] Yet another reference is the publication by Kumar et al. (Applied Thermal Engineering, Vol. 116, pp. 372-381, 2017), where the authors performed gasification of high ash coal in a bubbling fluidized bed gasifier. The gasifier has a height of 2.5 meters, has a single diameter throughout the height, and has a refractory lining. A screw feeder is used to feed the coal pieces into the gasifier, again, a two-part feeder with a rotary feeder and a screw feeder is not presented. The gaseous reactant feeder also lacks preheating and thorough mixing before entering the gasifier.

[0012] Yet another reference is Indian Patent Application No. 201811014119, which relates to a Pressurized Fluidized Bed Gasification (PFBG) pilot scale test facility having means of external heating for testing high ash coal, biomass, rejects and mixtures thereof. More particularly, the invention relates to an Air Blown Pressurized Fluidized Bed Gasification (PFBG) pilot scale test facility having a feed capacity varying from 7 kg / hr to 20 kg / hr. It has an operating temperature of up to 1000°C and a feed rate of up to 3 kg / cm. 2The test facility consists of an externally heated metallic pressurized fluidized bed gasifier. However, the unit does not have a refractory lined gasifier. The gasifier does not have an oxygen generator, which makes it impossible to carry out gasification performance analysis in an oxygen-steam mixture. Also, a two-part feeder with a rotary feeder and a screw feeder is not presented.

[0013] All the above mentioned inventions describe specific designs and related processes for different fluidized bed gasification configurations, limiting the flexibility for feed materials and operating conditions, while developing suitable gasifiers capable of handling different feedstocks becomes essential for further development in this emerging field. Current gasification facilities have the possibility to establish the desired fluid behavior to enhance the gasification performance such as gas composition, gas yield, carbon conversion and related parameters of different feedstocks. Summary of the Invention

[0014] Based on the details of the prior art and its shortcomings, the main objective of the present invention is to develop an oxygen enriched air blown pressurized fluidized bed pilot scale refractory lined gasifier for evaluating the gasification performance of coal, biomass, wash rejects and mixtures thereof in any proportion in a real environment, which is superior to commercial gasifiers including combusting a portion of the feedstock to provide enthalpy for endothermic gasification of a wide range of feedstocks to produce synthesis gas for thermal and various downstream applications, and obviates the shortcomings of the known prior art as detailed above.

[0015] Another object of the present invention is to develop an oxygen enriched air blown pressurized fluidized bed pilot scale refractory lined gasifier for evaluating the gasification performance of coal, biomass, wash rejects and any mixtures thereof in air / oxygen / oxygen enriched air / steam and any mixtures thereof in any proportion as per process requirement.

[0016] It is yet another object of the present invention to provide a method for treating a vascular endothelial cell comprising the steps of: 2 The objective of this study is to develop a pilot-scale oxygen-enriched air-blown pressurized fluidized bed gasifier to evaluate the agglomeration behavior of different feed materials in oxygen-enriched air and steam atmospheres at pressures of 1000 MPa.

[0017] Yet another object of the present invention is to develop a pilot scale oxygen enriched air blown pressurized fluidized bed gasification facility to study the entrainment behavior of different feed materials.

[0018] Yet another object of the present invention is to develop a pilot scale oxygen enriched air blown pressurized fluidized bed gasifier for measuring gas composition, gas yield and carbon conversion during gasification of different feedstocks.

[0019] It is yet another object of the present invention to determine the feeding behavior of various carbonaceous solids during gasification using screw feeders in addition to rotary feeders.

[0020] The present invention provides an oxygen-enriched air-blown pilot scale pressurized fluidized bed refractory lined gasifier comprising a heat resistant refractory lined gasifier having two different diameter cylindrical vessels with means for monitoring temperature at five different locations along the gasifier, fitted with a multi-hole removable conical distributor and means for pre-heating and thorough mixing of the gas stream before it enters the gasifier via an air plenum, with gaseous reactant generation and supply for reactants such as mixtures of air / steam / oxygen-enriched air / air-steam / oxygen-enriched air-steam in any ratio, with differential pressure measurement between the distributor and the bed, with a lock hopper system fuel supply, with different the feed nozzles for the various fuels, the variable RPM multi-pocket rotary feeders and screw feeders, the inclined feed lines with pneumatic conveying means for the feed material, the variable RPM multi-pocket rotary extractors, the means for removing ash particles in a controlled manner in either dry or agglomerated form, the purge devices and rupture disks / safety valves, the cyclone separators, cooling columns, venturi scrubbers, mist eliminators, settling tanks, gas sampling stations and flare stacks which provide a wide range of operational flexibility with respect to pressure, temperature, feed material, feed rate, gaseous reactants, residence time, particle size and particle density.

[0021] In one embodiment of the invention, the gasifier has an operating temperature of up to 1050°C and a maximum gasification temperature of up to 10 kg / cm 2 It has an operating pressure of 10000Kg / hr, a feed rate of up to 60kg / hr, and a particle size tolerance in the range of 0-6mm.

[0022] In another embodiment of the invention, the gasifier is refractory lined to protect the gasifier body from high temperatures exceeding 1100°C and has means for temperature measurement at two different locations in the bed and three different locations in the freeboard zone. The refractory lining is designed to withstand pressure and minimize degradation at high temperatures as well as expansion and contraction during heating and cooling cycles. It is also shown to measure the differential pressure in the distributor.

[0023] In another embodiment of the invention, the apparatus has reactants (air, oxygen, steam) supply system comprising steam generator with accumulator, air compressor with gas holder, PSA type oxygen generator, booster and header along with means to heat different gas streams to different levels as per process requirement before entering the gasifier including i) initial preheater for heating air / oxygen enriched air up to 150°C, ii) steam superheater with heating capacity up to 250°C, iii) initial mixer cum superheater with heating capacity up to 400°C and iv) final mixer cum superheater with heating capacity up to 600°C.

[0024] In yet another embodiment of the present invention, the apparatus has a solid fuel feed system with a variable RPM multi-pocket rotary feeder and screw feeder isolated by a dome valve and fitted with two feed lock containers for sequential pressurization and depressurization, the apparatus also has two feed nozzles connected to a feeder mechanism with feed lines with different slopes, one directly above the distributor and the other above the floor within the gasifier, to handle a wide range of carbonaceous feedstocks.

[0025] In yet another embodiment of the invention, the apparatus has a bottom ash recovery device comprising a variable RPM rotary extractor and two ash lock vessels fitted with dome valves for sequential pressurization and depressurization.

[0026] In yet another embodiment of the present invention, the unit not only has the capability of gasifying a single solid feed or a mixture of multiple feed materials, but also has a nitrogen flushing unit to handle any type of emergency.

[0027] In yet another embodiment of the present invention, the apparatus includes a high temperature cyclone device equipped with a cyclone ash lock isolated by a water jacketed dome valve for sequential pressurization and depressurization purposes.

[0028] In yet another embodiment of the invention, the apparatus includes a jacketed water cooling column for gas cooling and removing suspended solids from the gas stream, followed by a multi-compartment gravity settling tank for separating the suspended solids washed from the water stream from the cooling column.

[0029] In yet another embodiment of the invention, the apparatus includes a venturi scrubber for removing acidic components from the gas stream with alkaline water, followed by a mist eliminator to remove water from the gas prior to sampling and flaring.

[0030] In yet another embodiment of the invention, the apparatus comprises an LPG-assisted flare stack for flaring excess gas streams.

[0031] In yet another embodiment of the present invention, the apparatus has a process control and data acquisition system with a PLC-SCADA control station for controlling and monitoring all process parameters along with alarm system, safety fuses, safety control input signals for power failure, high temperature limit, sensor burnout and short circuit, high flow limit, safety control output signals for cutting off power to the heater. [Brief description of the drawings]

[0032] [Figure 1]In the drawings accompanying this specification, a gasification installation is represented, which is composed of various components 1 to 39 embodied in Fig. 1. 1. Boiler (steam generator), 2. Steam accumulator, 3. Steam superheater, 4. Oxygen generator, 5. Oxygen booster, 6. Air compressor, 7. Nitrogen generator, 8. Reactant process header / hopper, 9. Reactant preheater, 10. Reactant mixer and superheater-I, 11. Reactant mixer and superheater-II, 12. Feed hooper, 13. Dome valve and actuated ball valve, 14. Feed lock vessel-I, 15. Feed lock vessel-II, 16. A rotary feeder, 16. B Screw feeder, 17. Feed nozzle-I, 18. Feed nozzle-II, 19. Gasifier, 20. Cone distributor, 21. Air plenum, 22. Rotary extractor, 23. Ash lock vessel-I, 24. Ash lock vessel-II, 25. Thermocouple, 26. Cyclone separator, 27. Cyclone ash lock, 28. Cooling column, 29. Cooling seal pot, 30. Cooling water circulation pump, 31. Cooling water tank, 32. Settling tank, 33. Alkaline solution recirculation pump, 34. Alkaline solution tank, 35. Venturi alkaline solution seal pot, 36. Venturi scrubber, 37. Knockout drum (mist eliminator), 38. Flare stack, 39. Gas sampling port. Furthermore, Figure 1 also represents the PFBG test facility consisting of various sections such as solid and gaseous reactant feeding section, gasification section, gas cooling and scrubbing section, etc.

[0033] [Diagram 2] 1 shows details of the PFBG delivery nozzle and distributor.

[0034] Detailed Description of the Invention The present invention provides a PFBG test facility which consists of various sections such as solid and gaseous reactant supply section, gasification section, gas cooling and scrubbing section, etc. A detailed description of each section is given as follows:

[0035] i.Solid feeding device The feed is introduced into the gasifier (19) through a solids feeder. It has one hopper (12) and two feed locks (14, 15). The top lock is called feed lock 1 (14) and the bottom lock is feed lock 2 (15). The top lock is used for pressurization and depressurization, whereby material is fed from feed lock 1 to feed lock 2, which is constantly under pressure. A rotary feeder (16A) for coal / coal-biomass mixtures and a screw feeder (16B) for biomass and similar materials control the feed rate. The solids are pneumatically fed into the interior of the gasifier just above and inside the bed by two different nozzle pipes (17, 18) using conveying air. Nitrogen flushing lines with manual valves are provided in the solids feed line and in the feed lock for flushing / purging purposes. It may be mentioned here that there are two feed nozzles (17, 18) provided in the gasifier to introduce different feed materials into the gasifier. This arrangement helps to change the slope of the feed line so that feed materials of different densities flow smoothly. Moreover, while one nozzle is used for feeding, the other may be used for sampling the bed during experimental runs.

[0036] ii. Gas-like reactant feeding device A pressure control valve between the air supply compressor (6) and the air header controls the air / O 2 The pressure in the header (8) is about 10 kg / cm higher than the pressure in the gasifier. 2The oxygen pressure is maintained higher than the gasifier pressure by the pressure regulator and the oxygen booster (5) between the oxygen generator (4) and the initial preheater (9) for preheating, and then introduced into the initial mixer and superheater (10). The electrically heated initial preheater (9) preheats the air-oxygen to the required temperature. Steam is generated in the diesel-fired steam generator (1) and stored in the steam accumulator (2). The steam from the accumulator passes through the steam superheater (3). These air-oxygen and steam are further introduced into the initial mixer and superheater (10) and the final mixer and superheater (11). Both the initial and final mixer and superheaters are used to mix and superheat the air-oxygen-steam stream before entering the reactor. Mass flow meters and flow control valves are provided to regulate the air and oxygen flow rates in the fluidizing air line, oxygen line, and delivery line. Mass flow meters, flow controllers, and flow control valves regulate the steam flow rate. All lines from the steam generator and heater to the reactor are insulated. Nitrogen lines with manual valves are provided in the gaseous reactant supply lines for flushing / purging purposes in case of any emergency.

[0037] iii. Gasifier iv. The gasifier (19) can provide a maximum of 10 kg / cm 2It is a two diameter cylindrical vessel with an internally refractory lined device with three zones, with an operating pressure of 1000 psi and an operating temperature of up to 1050 °C. The refractory lining of the gasifier is designed to be able to withstand pressure and minimize degradation at high temperatures as well as expansion and contraction during heating and cooling cycles. It is also shown to measure the differential pressure in the distributor. The bottom of the gasifier is called the bed section, the top of the gasifier is called the freeboard section and the third section is called the transition section, which is conical in shape and connects the two cylindrical sections. The bottom of the reactor section is called the air plenum (21) and is integrated with a conical distributor (20) and is properly insulated to avoid condensation of steam. The air / oxygen enriched air and steam mixture is introduced as small jets through the distributor. The distributor is removable for its cleaning if necessary. The height of the reactor is about 5 m including the air-steam distributor. The gasifier is equipped with pressure, differential pressure, temperature measurements, internal temperature measurements at five heights, suitable nozzles for bed sampling, and safety devices such as pressure relief valves and rupture disks.

[0038] v. PFBG supply nozzle In this case, the gasifier operates in a bubbling fluidization state and is designed to handle a wide range of carbonaceous solid feed materials such as coal, various biomasses with different densities and reactivities, and coal-biomass mixtures in any ratio. In the case of gas-solid fluidization, when a gas flow is introduced at the bottom of a packed solid bed, the gas moves upwards through the spaces between the particles. When the gas velocity exceeds a certain threshold limit called the minimum fluidization velocity (Umf), the upward drag force becomes large enough to counter the negative buoyancy force of particle gravity. Now the particles move away from each other and become suspended in the fluid, expanding the volume of the bed and exhibiting a certain fluid-like behavior. If the gas velocity is further increased, the bed continues to expand, the bed height increases, the bulk density decreases, and finally entrainment occurs, where the particles are carried away from the bed with the gas flow. Furthermore, the expanded bed and higher bed height leads to an increase in the volume of the fluidized bed, which results in a longer residence time of the particles inside the bed and subsequently a higher carbon conversion rate. Conversely, once the gas bubbles leave the distributor holes and move through the fluidized bed, their diameter increases with height, causing a decrease in gas-particle contact and an increase in the possibility of entrainment, thus limiting the maximum bed height at a given height. Furthermore, if the fuel particles have a lower reactivity, a longer residence time is required to achieve the desired level of conversion. At the same time, low density materials occupy more volume to accommodate the desired residence amount, which requires a higher bed height. In this configuration, two feed nozzles (17, 18) are mounted on the gasifier at two different heights to adjust the bed height to the desired range (Figure 2). As mentioned above, one nozzle (17) is mounted directly above the expanded bed at the maximum possible height, and the other nozzle is mounted above the distributor (20) at a specified height, in order to appropriately vary the bed height depending on the fuel reactivity, the desired residence time, the density of the feed material, and the allowable bubble diameter. Therefore, placement of nozzles at different heights in the gasifier is one of the key factors in successfully handling a wide range of feed materials to obtain optimal levels of conversion without operational issues.

[0039] vi. Bottom ash extraction device The ash cooler at the bottom of the air plenum (21) is a jacketed pipe. Soft water coming from the spray tower flows through the jacket to cool the hot ash. The rotary ash extractor (22) located below the ash cooler extracts the ash from the reactor at a specified rate to maintain the bed height. Below the ash extractor are two bottom ash locks used to store the ash and to pressurize and depressurize in the reverse order of the coal locks. Ash lock vessel-I (23) is an intermediate storage vessel that holds the ash at the bottom when ash lock-2 (24) is discharging ash. Both ash lock vessel-I and ash lock vessel-II have the same capacity. Sealing / blanketing of the ash locks can be done by nitrogen from the nitrogen generator (7). A nitrogen line with a manual valve is provided in the bottom ash discharge line for flushing / purging purpose in case of any problem.

[0040] vii. Cyclone with fly ash collector During plant operation, the raw gas from the freeboard enters the cyclone (26) together with the entrained fines. Appropriate thermal tracking is performed to prevent condensation of condensable gases. The raw gas enters from the side and leaves from the top. Ash including unreacted carbon particles captured by the cyclone is collected in the cyclone ash lock (27) and then discharged. Sealing / blanketing of the ash lock can be done with nitrogen from a nitrogen generator. A nitrogen line with a manual valve is provided in the cyclone ash discharge line for flushing / purging purposes in case of problems.

[0041] viii. Gas Cooling and Purification Equipment The gas cooler consists of a cooling column (28) and a seal pot (29). Two concentric pipes are assembled to make the cooling column. The cooled soft water comes from the spray tower water tank, flows through its jacket and returns to the spray tower water tank in a closed loop to cool the inner shell. The cyclone outlet pipe is connected to the top of the cooling column. The inner shell has spray nozzles to spray water and cool the gas. The cooling water tank (31) is fitted with a pump (30) and is provided with an inlet strainer of sufficient capacity, taking into account the ash particles and the opening of the spray nozzles, so that the water can flow smoothly. The water filtration / sedimentation unit (32) is used to separate fine particles from the process water. The water filtration unit is of a size sufficient to wash the dusty water. The raw gas enters from the top of the cooling column and the cooled gas leaves from the bottom together with the water. A constant water level is maintained in the cooling seal pot (29). The gas scrubbing section also comprises a Venturi scrubber (36) with integral Venturi seal pot (35) for scrubbing the acid gas, and a knockout drum / mist eliminator (37) for removing moisture from the clean gas. Apparatus is also provided consisting of an alkaline solution tank (34) and a circulating pump (33) for circulating an alkaline solution within the Venturi scrubber.

[0042] ix. Exhaust Systems and Flare Stacks A small amount of the clean gas leaving the knockout drum is collected at a gas sampling point (39) for gas analysis. The majority of the clean gas from the knockout drum passes through a pressure control valve and a water-sealed flare stack before flaring. The flare stack (38) is equipped with an LPG burner as an auxiliary fuel.

[0043] x.PLC-SCADA control system The said installation comprises a control panel with individual heating controllers with MCBs, alarm system, safety fuses, data acquisition system with PLC-SCADA control station along with safety control input signals for power failure, high temperature limit, sensor burnt and short circuit, high flow limit, safety control output signals for stopping power to heaters. The system is fully subdivided through a programmable logic controller to maintain its gas flows, temperatures, pressures. The PLC records all parameters, trends and alarms for all parameters. The basic principle of the PLC is designed to ensure the necessary graphs with each and every parameter.

[0044] The inventive step included in the present invention is as follows:

[0045] i. An oxygen-enriched air-blown pressurized fluidized bed pilot-scale refractory-lined gasifier with 1.5 tonnes / day capacity for gasifying coal, biomass, wash rejects, and mixtures thereof in any proportion, in a real environment with continuous feed and ash recovery; in commercial gasifiers, it is mandatory to ensure combustion of a portion of the feedstock to provide enthalpy to drive a wide range of endothermic gasification of the feedstock to produce heat and synthesis gas for various downstream uses.

[0046] ii. The gasifier is a two diameter cylindrical vessel containing a bed section, a freeboard section and a transition section in between, which ensures sufficient residence time of the generated syngas at high temperatures to produce tar-free syngas from a variety of feedstocks while minimizing the escape of fines.

[0047] iii. The unit is equipped to operate in air / oxygen / oxygen enriched air / steam as well as mixtures thereof in any ratio as per process requirements.

[0048] iv. Refractory lined gasifiers are designed to withstand pressure and minimize degradation at high temperatures as well as expansion and contraction during heating and cooling cycles.

[0049] v. The apparatus includes a solid fuel feeder with a variable RPM multi-pocket rotary feeder and a screw feeder, two feed nozzles connected to a feeder assembly with feed lines of different slopes, one nozzle directly above the distributor and the other above the bed in the gasifier to handle a wide range of carbonaceous feedstocks. Additionally, while one nozzle is being used for feeding, the other may be used for sampling the bed during experimental runs.

[0050] vi.The apparatus has a removable air plenum section consisting of multiple distributors with various numbers and sizes of holes to adjust the velocity and flow of reactants during the endothermic gasification reaction according to the physical and chemical properties of different feedstocks. The removable air plenum has the advantage of easy cleaning and maintenance of the distributor plate, which results in smooth and trouble-free operation.

[0051] vii.The unit is equipped with nitrogen flushing device throughout the unit to deal with any kind of emergency during operation. The inflow of nitrogen dilutes the reactive components in the gasifier to stop the rapid temperature rise, and prevents the agglomeration of ash and the formation of clinker in the gasifier.

[0052] viii. The apparatus has a wide range of operational flexibility with respect to pressure, temperature, fuel and gaseous reactant feed rates, residence time, bed volume, particle size and particle density.

[0053] example The following examples are given as illustrations of the present invention and therefore should not be construed as limiting the scope of the present invention.

[0054] First, check the power and feed water before switching on the plant. The required amount of inert bed material (coal ash-2mm) is taken into the feed hopper, then the bed material is transferred from the hopper in the atmosphere to the feed lock-I, then from the feed lock-I to lock-II. The desired mass flow rate of inert bed material is then fed into the bed section of the gasifier from lock-II through a pneumatic conveying line using a rotary feeder to build the bed to the desired height. Preheated air, air-oxygen and steam are mixed and superheated in the air-steam mixer to a maximum of 550°C and enter the gasifier through a cone distributor at a controlled rate to maintain proper fluidization and meet the process requirements. The inert bed material is extracted from the bed at a controlled rate to maintain the desired bed height, and after cooling to about 55°C, it is discharged to the bottom ash lock-I and then to lock-II. The bed height is monitored by a differential pressure transmitter and maintained according to the process requirements. The bottom ash is collected at a controlled rate at 15-minute intervals using a rotary extractor. At the same time, the discharge temperature, reactor temperature, bottom ash weight, differential pressure, and discharge collection time are recorded. The feed rate and ash discharge rate are kept constant after the bed build-up is completed.

[0055] After achieving bed temperature of 500°C and stabilization of the entire unit, the feed sample i.e. coal / biomass / rejects or a mixture thereof in the desired range is fed into the gasifier. The combustion of fuel in the bed is then initiated and the temperature is gradually increased to 950-1050°C, taking care to avoid any kind of agglomeration / clinker formation in the bed. Further, the bed temperature is slowly increased to the desired temperature. Samples of the bottom ash are collected at regular intervals and kept aside for further analysis.

[0056] Hot, dusty raw fuel gas leaves the gasifier through the freeboard section and enters the cyclone where the majority of the entrained particles are captured. These particles are then discharged into the cyclone ash lock.

[0057] Fuel gas from the cyclone enters the cooling column. Water from the process water tank is sprayed directly onto the gas to reduce the temperature and capture residual solid particles. The spray nozzles are located at a fixed height. The cooling column is water jacketed and cold water circulates in a closed loop, with water pumped from the cooling tower. The cooled gas together with the sprayed water enters the seal pot located at the bottom of the cooling pipe. The water height in the seal pot is maintained by controlling the discharge rate of water into the water filtration unit. Clean water from the water filtration unit is returned to the process water tank and reused.

[0058] The cooled gas leaves the top side of the seal pot and enters a venturi scrubber where the fuel gas is further treated with alkaline water recirculation to remove acidic components. The moist clean gas containing water droplets then passes through a knock-out drum to remove all moisture from the clean gas. A portion of the clean gas coming out of the knock-out drum is periodically collected for gas analysis and the other portion of the pressurized clean gas from the knock-out drum passes through a pressure regulating valve and a water-sealed flare stack before flaring. The flare stack is provided with an LPG burner as an auxiliary fuel. The collected gas samples are analyzed using an offline gas chromatograph to obtain the composition of the gas. The gas components basically include carbon monoxide, hydrogen, carbon dioxide and methane.

[0059] The experimental conditions and product gas compositions of three experimental runs using two coals from different mines, namely MCL-I, MCL-II, are shown in Tables 1 and 2, respectively.

[0060] [Table 1]

[0061] [Table 2]

[0062] Advantages of the invention 1. An oxygen-enriched air-blown pressurized fluidized bed pilot-scale refractory-lined gasifier with a feed capacity of 1.5 tonnes / day is equipped to operate with air / oxygen / oxygen-enriched air / steam and mixtures of any ratio thereof as per process requirements. The gasification performance of a particular feedstock can be determined in this test facility within a short period for its commercial application.

[0063] 2. The said apparatus includes two feed nozzles connected to a variable RPM multi-pocket rotary feeder, screw feeder, and feeder configurations with different inclinations to handle coal, biomass, wash rejects, and mixtures thereof in any proportion in a real environment, one directly above the distributor and the other above the bed in the gasifier, with the distinct advantage of having a solid fuel feeder, which is superior in commercial gasifiers and expands the range to produce heat and synthesis gas for various downstream uses, ensuring the combustion of a portion of the feed material to provide enthalpy to drive the endothermic gasification of the feed material. Furthermore, while one nozzle is used for feeding, the other may be used for sampling the bed during experimental runs.

[0064] 3. The freeboard section of the refractory lined gasifier is long enough to ensure the desired residence time of the synthesis gas produced at high temperature, as well as the minimal scattering of fines, in order to produce tar-free synthesis gas from different feedstocks.

[0065] 4. The refractory lining of the gasifier is designed to withstand pressure, temperature, and minimize degradation as well as heat loss, expansion and contraction during heating and cooling cycles.

[0066] 5. The above system has the advantage of a reactant supply system comprising a steam generator with accumulator, an air compressor with gas holder, an oxygen generator of PSA type, a booster and headers, together with means to heat different gas streams in the range of 150-600°C as per process requirements before entering the gasifier depending on the combustibility and gasification characteristics of different carbonaceous feedstocks.

[0067] 6. The device has the advantage of removing ash particles in either a dry or agglomerated state in a controlled manner.

[0068] 7. The apparatus has a removable air plenum section consisting of multiple distributors with various numbers and sizes of holes to adjust the velocity and flow of reactants during the endothermic gasification reaction. The removable air plenum has the advantage of easy cleaning and maintenance of the distributors, thereby resulting in smooth and trouble-free operation.

[0069] 8. The unit is equipped with nitrogen flushing device throughout the unit to deal with any kind of emergency during operation. The inflow of nitrogen dilutes the reactive components in the gasifier and stops the sudden temperature rise which may cause ash agglomeration and clinker formation in the gasifier.

[0070] 9. The apparatus has a wide range of operating flexibility with respect to pressure, temperature, fuel and gaseous reactant feed rates, residence time, particle size and particle density.

[0071] 10. The apparatus also has an arrangement for product gas analysis using an on-line gas analyzer connected to the apparatus in the outlet line, or means for collection of the exiting gas from the sampling port using any gas sampling arrangement for off-line gas analysis purposes.

Claims

1. 1. An oxygen-enriched air-blown pilot-scale pressurized fluidized bed refractory-lined gasifier system (40), comprising: Cylindrical containers of two different diameters; A gaseous reactant generation and delivery system having means for preheating and thorough mixing prior to entering said gasifier (19); A removable multi-perforated conical distributor (20); Air plenum (21); a differential pressure measurement across the distributor and the bed; A fuel supply system having a feed hopper (12) arrangement with a rotary feeder (16A) and a screw feeder (16B); A plurality of delivery nozzles (17, 18); an inclined feed line having means for pneumatic conveying of the feed material; an ash recovery device consisting of a rotary extractor (22); Purge system; Rupture disc / safety valve; Cyclone separator (26); Cooling column (28); Venturi scrubber (36); Knockout drum (mist eliminator, 37); Settling tank (32); Gas sampling port (39); A flare stack (38); and Nitrogen Generator (7) Equipped with Nitrogen Flashing is an oxygen enriched air blown pilot scale pressurized fluidized bed refractory lined gasifier system with a control panel as well as data acquisition for storing and displaying all data including process parameters allowing a wide range of operational flexibility with respect to pressure, temperature, feedstock, feed rate, gaseous reactants, residence time, particle size and particle density.

2. 2. The gasifier system (40) of claim 1, wherein said heat resistant and refractory lined dual diameter cylindrical gasifier comprises a bed section, a freeboard section, and an intermediate transition section with temperature measurement by a thermocouple (25).

3. The gasifier system (40) of claim 1, wherein the gaseous reactant generation and supply device comprises a steam generator (1) with accumulator (2), an air compressor (6) with gas holder, a PSA type oxygen generator (4), an oxygen booster (5), and a reactant process header (8) with heating capability for different gas streams in the range of 150-600°C, utilizing (i) a reactant preheater (9) for heating air / oxygen enriched air up to 150°C, (ii) a steam superheater (3) with heating capacity up to 250°C, (iii) a reactant mixer and superheater-I (10) with heating capacity up to 400°C, and (iv) a reactant mixer and superheater-II (11) with heating capacity up to 600°C depending on the combustibility and gasification characteristics of different carbonaceous feedstocks before entering the gasifier (19).

4. The gasifier system (40) of claim 1, wherein the removable air plenum (21) is a multiple cone distributor (20).

5. The gasifier system (40) of claim 1, wherein the solid fuel feeder having a feed hopper (12) arrangement has a variable RPM multi-pocket rotary feeder (16A) and a screw feeder (16B) fitted with feedstock lock vessel-I (14) and feedstock lock vessel-II (15) for sequential pressurization and depressurization / isolation by dome valves and actuated ball valves (13), has two feed nozzles (17, 18) connected to a feeder assembly having feed lines with different slopes, one directly above the distributor and the other above the floor in the gasifier (19), and handles different carbonaceous feedstocks.

6. 2. The gasifier system (40) of claim 1, wherein the ash recovery unit comprises an ash cooler, a variable RPM rotary extractor (22), an ash lock vessel-I (23) and an ash lock vessel-II (24) for sequential pressurization and depressurization / isolation with a dome valve and an actuated ball valve (13).

7. 2. The gasifier system (40) of claim 1, wherein said cyclone separator (26) is fitted with one water jacketed cyclone ash lock (27) and a dome valve and an actuated ball valve (13) for sequential pressurization and depressurization purposes.

8. 2. The gasifier system (40) of claim 1, wherein the cooling column (28) is a jacketed water-cooled column consisting of two concentric pipes with spray nozzles on the inner shell, a cooling seal pot (29), a cooling water tank (31), a cooling water circulating pump (30), and a multi-compartment gravity settling tank (32) for separating suspended solids washed out of the cooling column water flow.

9. 10. The gasifier system (40) of claim 1, wherein the Venturi scrubber (36) is integrated with a Venturi alkaline solution seal pot (35), an alkaline solution tank (34), and an alkaline solution recirculation pump (33) for removing acidic components from the gas stream, followed by a knock-out drum (mist eliminator, 37) for removing moisture from the gas prior to sampling and flaring with the aid of an LPG supported flare stack (38).

10. 2. The gasifier system (40) of claim 1, wherein the system includes means for product gas analysis using an online gas analyzer connected to a device in the outlet line through the gas sampling port (39) or means for collection of the gas exiting the gas sampling port (39).

11. The gasifier system (40) of any preceding claim, wherein the system comprises a process control and data acquisition system comprising a PLC-SCADA control station for controlling and monitoring temperature and pressure of the gasifier (19).

12. The system has an operating temperature of up to 1050°C with grain size tolerance ranging from 0 to 6mm, a maximum of 10 kg / cm ２ 2. The gasifier system (40) of claim 1, having an operating pressure of 0.05 to 1.0001 psi and a feed rate of up to 60 kg / hr, said system being capable of gasifying coal (non-coking coal with ash content up to 60%), biomass, wash rejects and mixtures thereof in proportions of 0 to 100% (by weight).

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