AN OXYGEN ENRICHED AIR BLOWN PILOT SCALE PRESSURIZED FLUIDIZED BED REFRACTORY LINED GASIFIER
20250197747 ยท 2025-06-19
Inventors
- Prakash Dhondiram CHAVAN (Dhanbad, IN)
- Sujan SAHA (Dhanbad, IN)
- Nilesh D. DHAIGUDE (Dhanbad, IN)
- Vishal CHAUHAN (Dhanbad, IN)
- Gajanan SAHU (Dhanbad, IN)
- Sudipta DATTA (Dhanbad, IN)
- Pradeep Kumar SINGH (Dhanbad, IN)
Cpc classification
C10J3/723
CHEMISTRY; METALLURGY
International classification
Abstract
The present invention discloses oxygen enriched air blown pressurized fluidized bed pilot scale refractory lined gasifier of 1.5 TPD feed capacity to gasify coal, biomass, washery rejects, and their blends in any proportion in the actual atmosphere of commercial gasifier. The system is equipped in such a way that it can be operated in air/oxygen/oxygen enriched air/steam as well as their mixture in any proportion as per process requirement. The present invention discloses gasifier having feed rate carrying capacity up to 60 kg/hour, maximum operating temperature up to 1050 C. and pressure up to 10 kg/cm2. The facility consists different sections for gaseous and solid feeding, gasification, ash withdrawal, and gas Cooling & Cleaning. Besides gasification performance analysis, present invention is also discloses the study of agglomeration characteristics, entrainment and other fluidized bed gasification related parameters.
Claims
1-12. (canceled)
13. An oxygen enriched air blown pilot scale pressurized fluidized bed refractory lined gasifier system comprising: a cylindrical vessel of two different diameters; a gaseous reactant generation and supply system with the provision of preheating and thorough mixing before entering into the gasifier; plurality perforation removable conical distributors; an air plenum; differential pressure measurement instrument across the distributor and bed; a fuel feeding system with a feed hopper arrangement comprising of a rotary feeder and a screw feeder; plurality of feeding nozzles; an inclined feed lines with the provision of pneumatic conveying of feed materials; an ash withdrawal system consisting of a rotary extractor; a purging system; a rupture disc/safety valve; a cyclone separator; a quench column; a ventury scrubber; a knockout drum; a settling tank; a gas sampling port; a flare stack; and a nitrogen generator, wherein nitrogen flushing comprises a control panel and data acquisition section operative to store and display data including process parameters enabling a wide range of operational flexibility with respect to pressure, temperature, feedstock, feed rate, gaseous reactant, residence time, particle size and particle density.
14. The gasifier system of claim 13, wherein the heat resistant refractory lined two-diameter cylindrical gasifier comprises a bed section, a freeboard section, and a transition section between the bed section and the freeboard section, the transition section comprising thermocouples for temperature measurement.
15. The gasifier system of claim 13, wherein the gaseous reactant generation and supply system comprises a steam generator with an accumulator, an air compressor with a gas holder, a PSA based oxygen generator, an oxygen booster, and a reactant process header operable for heating different gaseous streams at 150 C. to 600 C., wherein, before entering into the gasifier with the aid of: (i) reactant pre-heater for heating air/oxygen enriched air up to 150 C.; (ii) steam super-heater with the capacity of heating up to 250 C.; (iii) a first reactant mixture-cum-super-heater with maximum heating capacity of 400 C.; and (iv) a second reactant mixture-cum-super-heater with the capacity of heating up to 600 C. depending on the combustibility and gasification characteristics of different carbonaceous feedstock.
16. The gasifier system of claim 13, wherein the removable air plenum is of multiple conical distributors.
17. The gasifier system of claim 13, wherein the solid fuel feeding system with the feed hopper arrangement has variable RPM multi-pocket rotary feeder and screw feeder fitted with a first feed lock vessel and a second feed lock vessel for sequential pressurization and depressurization/isolation by dome valve and actuated ball valve, having two feed nozzles connected to the feeder assembly with feed line having different inclination, one being above the distributor and another being above the bed in the gasifier to handle carbonaceous feedstocks.
18. The gasifier system of claim 13, wherein the ash withdrawal system comprises an ash cooler, a variable RPM rotary extractor, a first ash lock vessel, and a second ash lock vessel for sequential pressurization and depressurization or isolation by a dome valve and an actuated ball valve.
19. The gasifier system of claim 13, wherein the cyclone separator is fitted with a one water jacketed cyclone ash lock, a dome valve, and a actuated ball valve for sequential pressurization and depressurization.
20. The gasifier system of claim 13, wherein the quench column is a jacketed water quench column comprising two concentric pipes having spray nozzles at an inner shell thereof, a quench seal pot, a quench water tank, a quench water circulation pump, and a multi compartment gravity settling tank for separation of scrubbed suspended solids from a quench column water stream.
21. The gasifier system of claim 13, wherein the ventury scrubber is integrated with a ventury alkaline solution seal pot, an alkaline solution tank, and an alkaline solution recirculation pump adapted to remove acidic components from a gas stream followed by a knockout drum for removal of moisture from the gas stream before sampling and flaring with an LPG supported flare stack.
22. The gasifier system of claim 13, adapted for product gas analysis by an on-line gas analyzer coupled with the gasifier system in an exit line through the gas sampling port or for collecting outgoing gas from the gas sampling port.
23. The gasifier system of claim 13, further comprising a process control and data acquisition system comprising a PLC-SCADA control station operable to control and monitor temperature and pressure of the gasifier.
24. The gasifier system of claim 13, configured for a maximum operating temperature up to 1050 C., a pressure up to 10 kg/cm.sup.2, a feed rate up to 60 kg/hour, a particle size acceptability from greater than 0 mm to 6 mm, the system being capable to gasify coal; biomass; washery rejects; and blends thereof.
Description
BRIEF DESCRIPTION OF THE DRAWING
[0042] In the drawing accompanying the specification,
[0044]
DETAILED DESCRIPTION OF THE INVENTION
[0045] The present invention provides PFBG test facility consisting of various sections such as solid and gaseous reactants feeding section, gasifier section and gas cooling and cleaning section. Detailed descriptions of each section are as follow:
i. Solid Feeding System
[0046] Feed material is introduced into the gasifier (19) through solid feeding system. This system has one hopper (12) and two feed locks (14, 15). The top lock is known as Feed Lock1 (14) and the bottom one is Feed Lock 2 (15). The top lock is used for pressurization and depressurization, in order to feed the material from Feed Lock1 to Feed Lock2, which is always under pressure. The Rotary feeder (16 A) for coal/coal-biomass blends and Screw Feeder (16B) for biomass and like material control feed rate. Solid is pneumatically fed inside the gasifier just above the bed and inside the bed by two different nozzle pipes (17, 18) using conveying air. Nitrogen flushing line with manual valve is provided with solid feeding line and feed locks for flushing/purging purpose. It may be mentioned here that there are two feed nozzles (17, 18) provided in the gasifier to introduce different feeds in the gasifier. This arrangement helps to change the inclination of the feed lines for smooth flow of the feed materials of different densities. Further, while one nozzle is being used for feeding, the other may be used for bed sampling during the experimental run.
ii. Gaseous Reactant Supply System
[0047] The pressure of Air/O.sub.2 Header (8) is maintained about 10 kg/cm.sup.2 higher than that of gasifier by a pressure control valve between the air supply compressor (6) and air header. From air header, air is supplied to feed locks for pressurization, to solid transport line for conveying feed and to air heater. The Oxygen pressure is maintained higher than that of the gasifier by a pressure regulator as well as oxygen booster (5) between the oxygen generator (4) and initial pre-heater (9) for pre heating prior to introducing in initial mixer-cum super-heater (10). The electrically heated initial pre-heater (9) preheats air-oxygen to the required temperature. Steam is generated in a diesel fired steam generator (1) and stored in the steam accumulator (2). Steam from accumulator is passed through steam super-heater (3). These air-oxygen and steam are further introduced in initial mixer-cum-super-heater (10) and final mixer-cum-super-heater (11). Both the mixer-cum-super-heater-initial and final are used for mixing and super heating the air-oxygen-steam stream before admitting to the reactor. The Mass flow meters and flow control valves are provided to regulate airflow rates and oxygen flow rates in fluidizing air-line, oxygen line, and the transport line. Mass flow meter, flow controller and flow control valves regulate steam flow rate. All lines from steam generator and heater to reactor are thermal heat insulated. Nitrogen line with manual valve is provided on gaseous reactant feed line for flushing/purging purpose in case of any sort of emergency.
iii. Gasifier
[0048] iv. The Gasifier (19) is two-diameter cylindrical vessel with three zone internal refractory lining system with operating pressure up to 10 kg/cm.sup.2 and at a temperature up to 1050 C. Refractory lining of the gasifier is designed in such a way that it can withstand the pressure, minimize the erosion at high temperature as well as the expansion and contraction during heating and cooling cycle. There is also provision of measuring differential pressure across the distributor. The bottom portion of the gasifier is known as Bed Section, the top section of the gasifier is known as Freeboard Section and the third section is known as Transition piece that is conical in shape connects these two cylindrical portions. Bottom of the reactor section is known as Air plenum (21), which is integrated with a conical distributor (20) and 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 as and when required. The height of the reactor is about 5 m including the air-steam distributor. The gasifier is provided with adequate nozzles for pressure, differential pressure, temperature measurements, inside temperature measurement at five levels, bed sampling, and safety devices like pressure release valve and rupture disc.
v. PFBG Feeding Nozzles
[0049] In the present case gasifier operates in bubbling fluidization condition and is designed to handle a wide range of carbonaceous solid feed materials like coal and different biomass having different density and reactivity and coal-biomass blends in any proportion. In case of gas-solid fluidization, once a gas stream is introduced at the bottom of a packed solid bed, the gas will move upwards through the inter particle spaces. As the gas velocity exceeds a certain threshold limit called minimum fluidization velocity (U.sub.mf), the upward drag force turns out to be large enough to counter the particle gravity minus buoyancy. Where, the particles will move away from each other and become suspended within the fluid, causing the bed to expand in volume and show some fluid like behavior. As the gas velocity is further increased, the bed will keep expanding resulting in increase in bed height, reduction in the bulk density and finally entrainment wherein the particles will get carried away from the bed with the gas stream. Further, expanded bed and higher the bed height provides increase in volume of the fluidizing bed resulting in higher residence time of the particle inside the bed and subsequently higher carbon conversion. On the contrary, once gas bubble detaches from distributor hole and travels inside fluidizing bed, its diameter increases with height causing reduction in gas-particle contact and increase in probability of entrainment, thus restricting maximum bed height at certain level. Further, when the fuel particle has lower reactivity, higher residence time is required to achieve the desired level of conversion. Simultaneously, lower density materials occupies more volume requiring more bed height to accommodate desired holdup. In the present setup, to adjust the bed height in desired range, two feed nozzles (17, 18) are fitted in the gasifier at two different heights (
vi. Bottom Ash Extraction System
[0050] The ash cooler at the bottom of the air plenum (21) is a jacketed pipe. Soft water coming from spray tower flows through the jacket for cooling the hot ash. A rotary ash extractor (22) located below the ash cooler extracts the ash from the reactor at a specified rate for maintaining the bed level. Below the ash extractor there are two bottom ash locks that are employed for storage of the ash, pressurization and depressurization in the reverse sequence of coal locks. Ash lock vessel-I (23) is an intermediate storage vessel to hold the bottom ash when the ash lock 2 (24) is discharging the ash. Both ash lock vessel-I and ash lock vessel-II have identical capacities. Sealing/blanketing of ash locks can be done by nitrogen from nitrogen generator (7). Nitrogen line with manual valve is provided on bottom ash discharge line for flushing/purging purpose in case of problems.
vii. Cyclone with Fly Ash Collection System
[0051] During plant operation, the raw gas from the freeboard along with elutriated fines enters cyclone (26). It is properly heat traced to prevent the condensation of condensable gases. Raw gas enters from the side and exits from the top. Ash along with un-reacted carbon particles, captured by cyclone, is collected in the cyclone ash lock (27) and then discharged. Sealing/blanketing of ash locks can be done by nitrogen from nitrogen generator. Nitrogen line with manual valve is provided on cyclone ash discharge line for flushing/purging purpose in case of problems.
viii. Gas Cooling and Cleaning System
[0052] Gas cooling system consists of a quench Column (28) and a seal pot (29). Two concentric pipes are assembled to make the quench column. Cooled, soft water flows through its jacket coming from spray tower tank for cooling the inner shell and returns to a spray tower tank in closed loop. The cyclone exit pipe is connected at the top portion of the quench column. The inner shell has spray nozzles for spraying water and cooling the gas. Quench water tank (31) is fitted with a pump (30) wherein inlet strainer of sufficient capacity is provided considering ash particles and spray nozzle openings so as to get smooth flow of water. Water filtration/settling unit (32) is used for separation of particulates from the process water. The size of water filtration unit is sufficient to clean dust laden water. The raw gas enters from the top of the quench column and the cooled gas along with water exits from the bottom. A constant water level is maintained in quench seal pot (29). The gas cleaning section also consists of a venturi scrubber (36) integrated with a venturi seal pot (35) for cleaning the acidic gas and a knock out drum/mist eliminator (37) to remove moisture from the clean gas. The system consisting of alkali solution tank (34) and a circulation pump (33) for circulating alkali solution in the venturi scrubbers is also provided.
ix. Exhaust System and Flare Stack
[0053] A small portion of the clean gas coming out of knock out drum is collected at gas sampling point (39) for gas analysis. Major part of the clean gas from the knockout drum is passed through pressure regulation valve and water sealed flare stack before flaring it. Flare stack (38) is provided with LPG burner as a support fuel.
x. PLC-SCADA Control System
[0054] The said facility has control panel with data acquisition system comprising of PLC-SCADA control station along with individual heating controllers with MCBs, alarm system, safety fuses, safety managements inputs for power failure, high temperature limits, sensor burnout and shorting, high flow limits, safety management outputs to terminate power to heaters. The system is completely atomized through programmable logical controller to maintain its gas flow, temperature, pressure. PLC record all the parameters, all parameters trends and alarms. PLC philosophy is designed to get the required graphs with respective parameters.
The Inventive Steps Involved in the Present Invention are
[0055] i. The oxygen enriched air blown pressurized fluidized bed pilot scale refractory lined gasifier of 1.5 TPD feed capacity is to gasify the coal; biomass; washery rejects; and their blends in any proportion in the actual atmosphere with continuous feeding and ash withdrawal, essential in the commercial gasifier to ensure combustion of some fraction of the feed to provide enthalpy to drive endothermic gasification of the reaming feed to generate syngas for thermal and various downstream applications. [0056] ii. The Gasifier is two-diameter cylindrical vessel comprising of bed section, freeboard section and in between transition section which ensures sufficient residence time of the generated syngas at high temperature to produce tar-free syngas from different feedstock as well as minimum fine elutriation. [0057] iii. The system is equipped in such a way that it can be operated in air/oxygen/oxygen enriched air/steam as well as their mixture in any proportion as per process requirement. [0058] iv. Refractory lined gasifier is designed in such a way that it can withstand the pressure, minimize the erosion at high temperature as well as the expansion and contraction during heating and cooling cycle. [0059] v. The said device has solid fuel feeding system comprising of variable RPM multi-pocket rotary feeder, screw feeder and two feed nozzles connected to the feeder assembly with feed line having different inclination, one is just above the distributor and another is above the bed in the gasifier to handle wide range of carbonaceous feedstock. Further, while one nozzle is being used for feeding, the other may be used for bed sampling during the experimental run. [0060] vi. Present device has removable air plenum section of multiple distributors with varying number and sizes of orifices to adjust reactant velocity and flow during endothermic gasification reactions as per the physic-chemical properties of different feedstock. Removable air plenum has the advantages of easy cleaning and maintenance of the distributor plate leading to smooth and trouble free operation. [0061] vii. Present device has the Provision of Nitrogen flushing arrangement in the entire system to tackle any kind of emergency situation during operation. Inflow of nitrogen dilutes reactant components in the gasifier to stop sudden temperature shoot up to prevent ash agglomeration and clinker formation inside the gasifier. [0062] viii. Present device has wide range of operational flexibility with respect to pressure, temperature, feed rate of fuel and gaseous reactant, residence time, bed inventory, particle size and particle density.
EXAMPLE
[0063] The following example is given by way of illustration of the present invention and therefore should not be construed to limit the scope of the present invention.
[0064] At first, the power supply and water supply is checked before switch on the plant. Required quantity of inert bed material (coal ash-2 mm) is taken in the feed hopper and then bed material is transferred from the atmospheric hopper to feed lock-I and then from feed lock-I to lock-II. Then inert bed material at the desired mass flow rate is fed from lock II to the bed section of the gasifier using a rotary feeder through a pneumatic conveying line to build up the bed of desired height. Preheated air, air-oxygen and steam are mixed and superheated up to 550 C. in an air-steam mixer and admitted to the gasifier through the conical distributor at a controlled rate to maintain proper fluidization as well as to fulfill the process requirement. Inert bed material from the bed is extracted under controlled rate to maintain the desired bed height and cooled to about 55 C. prior to discharging in bottom ash lock-I and then lock II. Bed height is monitored through differential pressure transmitters and maintained as per the process requirement. The bottom ash is collected at the interval of 15 minutes with controlled rate using rotary extractor. At the same time, discharge temperature, reactor temperature, weight of the bottom ash, differential pressure and the time of discharge collection are noted down. The feed rate and ash discharge rate are maintained constant after the completion of bed build up.
[0065] After attaining bed temperature of 500 C. and stabilization of the entire system, feed sample i.e. coal/biomass/rejects or their blended composition of the desired range are fed to the gasifier. Then fuel inside bed start ignition and temperature is gradually raised up to 950-1050 C. with care so as to avoid any kind of agglomeration/clinker formation inside the bed. Further, bed temperature is slowly raised up to desired temperature.
[0066] Bottom ash samples are collected at regular intervals and kept for further analysis. The hot dusty raw fuel gases leave gasifier from freeboard section and enter into the cyclone where most of the elutriated particles are captured. The captured particles are discharged in cyclone ash lock.
[0067] The fuel gas from the cyclone enters into the Quench Column. The water from the process water tank is directly sprayed onto the gas to reduce the temperature and capture the residual solid particles. There are Spray Nozzles that are placed at regular heights. The Quench Column is water jacketed and cold water is circulated in a closed loop, drawing water from Cooling Tower. The cooled gas along with sprayed water comes in the Seal Pot situated at the bottom of the quench pipe. The level of water in Seal Pot is maintained by controlling the rate of water discharge to water filtration unit. The clean water from the water filtration unit is recycled back to the process water tank.
[0068] The cooled gas exits from the top side of the seal pot and enters into venturi scrubber where fuel gas is further treated with recirculation of alkaline water to remove the acidic components. The saturated clean gas, containing water droplets then passes through knock out drum to get all the moisture removed from the clean gas. One part of the clean gas coming out of knock out drum is collected for gas analysis on regular basis and other part of clean gas under pressure from the knockout drum is passed through pressure regulation valve and water sealed flare stack before flaring it. Flare stack is provided with LPG burner as a support fuel. The collected gas samples are analyzed using the off line Gas Chromatograph to get the gas composition. The gas composition basically comprises of carbon monoxide, hydrogen, carbon dioxide and methane.
[0069] Experimental conditions and product gas compositions of three experimental runs with two Coal from different mines i.e. MCL-I, MCL-II are shown in Table 1 and Table 2, respectively.
TABLE-US-00001 TABLE 1 Experimental Conditions Gas Temper- Feed Air yield Bottom Cyclone Carbon Experimental ature Pressure rate flow Steam Oxygen (Nm3/kg ash Ash conversion run Feed range (kg/cm.sup.2) (kg/h) (Nm.sup.3) (kg/h) (Nm.sup.3) feed) (kg/h) (kg/h) (%) Example I MCL-I 940-960 0.55 45 20 10.0 15 2.11 19.9 0.35 >90 Example II MCL-II 960-1010 0.65 45 15 10 20 2.35 19.9 0.35 >90 Example III MCL-II 1010-1050 0.75 45 10 10 25 2.35 19.9 0.35 >90
TABLE-US-00002 TABLE 2 Syngas Compositions Experimental run Feed CO % H.sub.2 % CH.sub.4 % CO.sub.2 % N.sub.2 % Example I Coal 19.06 17.82 1.64 27.07 34.41 Example II Coal 22.6 22.2 2.95 23.5 28.75 Example III Coal 16.6 18.87 1.46 17.11 45.96
Advantages of the Invention
[0070] 1. The oxygen enriched air blown pressurized fluidized bed pilot scale refractory lined gasifier of 1.5 TPD feed capacity is equipped in such a way that it can be operated in air/oxygen/oxygen enriched air/steam as well as their mixture in any proportion as per process requirement. Gasification performance of a particular feed material can be judged in this test facility within a short span of time for its commercial exploitation. [0071] 2. The said system has distinct advantages of having solid fuel feeding system comprising of variable RPM multi-pocket rotary feeder, screw feeder and two feed nozzles connected to the feeder assembly having different inclination, one is just above the distributor and another is above the bed in the gasifier to handle coal; biomass; washery rejects; and their blends in any proportion in the actual atmosphere which prevails in the commercial gasifier ensuring combustion of some fraction of the feed to provide enthalpy to drive endothermic gasification of the reaming feed to generate syngas for thermal and various downstream applications. Further, while one nozzle is being used for feeding, the other may be used for bed sampling during the experimental run. [0072] 3. Freeboard section of the refractory lined gasifier is of sufficient length to ensure desired residence time of the generated syngas at high temperature to produce tar-free syngas from different feedstock as well as minimum fine elutriation. [0073] 4. Refractory lining of the gasifier is designed in such a way that it can withstand the pressure, temperature, minimize the erosion and heat loss as well as the expansion and contraction during heating and cooling cycle. [0074] 5. The said system is having advantages of reactant feeding system comprising of steam generator with accumulator, air compressor with gas holder, PSA based oxygen generator, booster and header with the provision of heating of different gaseous streams in the range of 150-600 C. as per process requirement before entering into the gasifier depending on the combustibility and gasification characteristics of different carbonaceous feedstock. [0075] 6. Present device has advantage to withdraw the ash particles either in the dry form or in agglomerated form in a controlled manner. [0076] 7. Present system has removable air plenum section of multiple distributors with varying number and sizes of orifices to adjust reactant velocity and flow during endothermic gasification reactions. Removable air plenum has the advantages of easy cleaning and maintenance of the distributor leading to smooth and trouble free operation. [0077] 8. Present device has the Provision of Nitrogen flushing arrangement in the entire system to tackle any kind of emergency situation during operation. Inflow of nitrogen dilutes reactant components in the gasifier to stop sudden temperature shoot up which may cause ash agglomeration and clinker formation inside the gasifier. [0078] 9. Present device has wide range of operational flexibility with respect to pressure, temperature, feed rate of fuel and gaseous reactant, residence time, particle size and particle density. [0079] 10. The present system has also arrangement for product gas analysis with the help of on-line gas analyzer coupled with the system in exit line or provision for collecting the outgoing gas from the sampling port with the help of any gas sampling arrangement for off-line gas analysis purpose