CN102533345A - Method and device for coal gasification in combined type fluidized bed - Google Patents

Abstract

A compound fluidized bed coal gasification method is composed of seven parts: coal preparation, gas supply, gasification, slag removal, dust removal, waste heat recovery and fine powder transportation. Ash fusion fluidized bed gasification realizes large particles In the gasification of coal, the incompletely converted fine powder enters the entrained bed gasification furnace through dense phase pneumatic transportation, and adopts a short residence time and high temperature gasification method for secondary gasification. Carried into the intersection of the fluidized bed and the entrained flow bed, and quickly mixed with the "low temperature" large particle semi-coke in the fluidized bed and the "low temperature" gas generated, part of the ash is selectively discharged in solid form for gasification furnace. The invention has the advantages of being suitable for various coal types and having a high carbon conversion rate.

Description

Combined fluidized bed coal gasification method and device

Field

The invention belongs to a coal gasification method and device, in particular to a high-efficiency fluidized bed coal gasification method and device that adopt a fluidized bed and an entrained flow bed composite integration.

Background technique

Coal gasification is one of the core technologies for efficient and clean utilization of coal, and is the basis for the development of process industries such as coal-based chemicals, coal-based clean fuels, industrial gas and polygeneration systems.

Judging from the current development trend of coal gasification technology at home and abroad, large-scale, pressurized, adaptable to various pulverized coal, low pollution, and easy purification are the development directions of coal gasification. The existing foreign pressurized gasifiers are mainly divided into three categories: pressurized fixed-bed gasifiers (such as Lurgi furnaces), pressurized fluidized-bed gasifiers (HTW) and pressurized entrained-bed gasifiers (Texaco, Shell, DOW, GSP). These three types of gasifiers have their own advantages and disadvantages. The pressurized fixed bed gasifier uses weakly cohesive lump coal as raw material, and the technology is mature. The methane content in the gas is high and the cold gas efficiency is high, but the purification system is complicated (tar treatment) ; The entrained bed gasifier operates at high temperature, and the gasification intensity and gas quality are high, but it needs to use coal with low ash and low ash melting point as raw material, which requires high oxygen consumption and high equipment investment; the coal type of the fluidized bed gasifier has wide adaptability, Low investment, low oxygen consumption, and flexible scale, but the amount of fine powder entrained in the gas is high, and the total carbon conversion rate is low (about 90%).

The Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences has successfully developed a complete set of technology for "ash fusion fluidized bed pulverized coal gasification", which has a wide range of coal types (from lignite to anthracite), and is suitable for the gasification of high ash, high ash melting point, and high sulfur coal. At present, the industrial application of daily treatment of 100 tons of bituminous coal at normal pressure and 320 tons of high-sulfur anthracite at 0.6MPa pressure has been completed. At the same time, the pressurized ash fusion gasification of 0.6-2.5MPa anthracite has been completed on the pressurized gasification pilot plant test. The problem of ash carbon content is well solved, but the amount of fine powder entrained in the gas is high, and the total carbon conversion rate is low (about 90%).

Since the operating temperature of the fluidized bed gasifier is about 1000°C, under this temperature condition, the coal coke needs to have a residence time of 20-30 minutes to be completely converted, but the fine particles (<0.1mm, accounting for 10% of the total coal input) % or so) in the gasifier is usually within ten to tens of seconds for a residence time. Although the fine powder circulation is increased, the total reaction time is short and the carbon conversion rate is low. This part of the unconverted fine powder is taken out of the system, resulting in a decrease in the carbon utilization rate of the fluidized bed.

Contents of the invention

The first object of the present invention is to provide a high-efficiency composite fluidized bed gasification method that is suitable for various coal types and has a high carbon conversion rate.

The second object of the present invention is to design a composite fluidized bed gasification device with simple structure and low cost, which combines fluidized bed and entrained flow bed.

The present invention is based on the concept of coal graded transformation, realizes the gasification of large particle coal by ash fusion fluidized bed gasification, and the incompletely converted fine powder is carried out through the entrained bed gasification furnace by adopting a short residence time and high temperature gasification method Secondary gasification, and then improve the total carbon conversion rate and processing capacity of the system, reduce energy consumption and operating costs, and achieve high gasification capacity as the goal. The unreacted fine powder carried out is semi-coke fine powder with low volatile content and no water. Its particle size is similar to that of dry coal powder entrained bed raw material, and can enter the entrained bed through dense phase pneumatic conveying. The fine powder is gasified under high temperature conditions in the entrained bed section, and the ash produced is carried along with the high temperature gas into the intersection section of the fluidized bed and the entrained bed, and is quickly combined with the "low temperature" large particle semi-coke in the fluidized bed and the produced ash The "low temperature" gas is mixed and part of the ash is selectively discharged from the gasifier in solid form.

The method for composite fluidized bed coal gasification of the present invention comprises the steps:

(1) Preparation of raw coal for gasification

After the raw coal is crushed, it is dried and screened so that the coal moisture is less than 5wt%, and the particle size is less than 6mm, which is sent to the coal bunker as raw coal for fluidized bed gasification; the fine powder comes from semi-coke fine powder that has not completely reacted during the gasification process, The fine powder collected by the cyclone, radiant waste heat boiler and high temperature ceramic filter;

(2) Gasification

a. First, bake the gasifier. When the temperature of the lower part of the fluidized bed gasifier is greater than 900°C and the temperature of the upper part is greater than 600°C, air and steam are introduced into the gas distributor at the lower part of the fluidized bed, The gasification crushed coal is continuously added to the feed port, and the air-to-coal ratio is 2.5-3.5Nm ³ /kg, and the steam-to-coal ratio is 0.3-0.6kg/kg, so that the coal is burned in the gasifier and the semi-coke furnace charge is obtained. , and gradually build up the material in the gasifier, at this time the entrained flow bed is still in the oven stage and kept at 850-900°C;

b. When the bed pressure drop of semi-coke materials in the fluidized bed gasifier reaches 5-10KPa, switch to oxygen/steam blowing after the system operation is stable, and the temperature is controlled at 800-900°C during the switching process;

c. Operate with an oxygen-to-coal ratio of 0.4-0.5Nm ³ /kg and a steam-to-coal ratio of 0.5-1.0kg/kg, and the temperature at the bottom of the fluidized bed gasifier is stable in the range of 950-1050°C;

d. After the gasification of the lower part of the fluidized bed gasifier is stabilized, the fine powder is transported from the fine powder delivery tank to the entrained bed combustion nozzle, and then oxygen and steam are fed into the combustion nozzle. The ratio of oxygen to dry coal powder is 0.5-0.7Nm ³ /kg, steam-coal ratio 0.1-0.3kg/kg, the operating temperature of the entrained bed is in the range of 1100-1300°C, and the temperature of the intersection of the fluidized bed and the entrained bed in the fluidized bed is in the range of 1050-1150°C;

(3) Slagging of gasifier

During the gasification process, adjust the gas velocity of the annular separation tube at 5-10m/s, and the oxygen concentration in the gas <25Vol%; the gas velocity of the central jet tube is 15-30m/s, and the oxygen concentration in the gas is 40-60vol%, so that The height of the semi-coke charge in the gasifier is kept so that the bed pressure difference is between 4 and 8KPa;

(4) Purification of crude gas and recovery of waste heat

Spray chilled water at the outlet of the gasifier to ensure that the cyclone inlet temperature is less than 900°C. The crude gas is separated by the first-stage cyclone separator, and the captured semi-coke fine powder is blown into the pyrolysis through the standpipe and the high-temperature fine powder control valve. The dense phase fluidized bed gasification section at the lower part of the gasification reactor participates in the reaction again; the crude gas enters the secondary cyclone separator, and the captured semi-coke fine powder is sent to the semi-coke fine powder collection/cooling tank and fine powder conveyor. into the fine powder storage bin; the coarsely separated high-temperature gas enters the radiation waste heat boiler, the convection waste heat boiler and the gas ceramic filter, and the gas temperature drops to 150-200°C and enters the Venturi water scrubber and the water-cooled leaching tower for further cooling and dust removal After that, it is exported to the gas purification section, and the semi-coke fine powder collected by the radiant waste heat boiler and ceramic filter is also sent to the fine powder storage bin through the semi-coke fine powder collection/cooling tank and fine powder conveyor;

(5) Conveying of fine powder

The fine powder collected by the secondary cyclone, radiant waste heat boiler and ceramic filter enters the fine powder storage bin, and the fine powder is sent to the fine powder feeding weighing tank through the pneumatic conveying pump, and then enters the fine powder feeding balance tank and fine powder feeding The delivery tank is blown by nitrogen to send the fine powder into the entrained bed combustion nozzle for gasification.

5. Gasifier shutdown

During normal parking, turn off the oxygen of the entrained bed combustion nozzle, stop the fine powder delivery, and at the same time increase the steam volume of the combustion nozzle to protect the nozzle, purge and cool down the entrained bed part; cut off the gas pipeline entering the system, The gas is vented, and the pressure is gradually reduced to normal pressure; after that, the gas velocity of the fluidized bed annular pipe is reduced to increase the ash discharge capacity, and at the same time, the amount of steam used in the fluidized bed is increased, the oxygen valve is closed, and the coal feeding system of the fluidized bed is closed. The temperature is controlled below 900°C; after the charge is discharged, the air intake is stopped, and finally the system is purged with steam and air respectively.

In order to realize the present invention, a compound fluidized bed coal gasification device with simple structure and low cost is designed.

The composite fluidized bed gasification device of the present invention is composed of a composite fluidized bed coal gasification furnace and a semi-coke fine powder circulation device, and the composite fluidized bed coal gasification furnace is composed of a fluidized bed and an entrained flow bed , the fluidized bed is composed of a fluidized bed furnace body, a gasifier gas outlet pipe, a gas distributor and an annular separation ash fall pipe. The top of the fluidized bed furnace body has a gasifier gas outlet pipe and a furnace top quenching water pipe There is a coal feed pipe in the lower part of the fluidized bed furnace body, the bottom of the fluidized bed furnace body is connected to a gas distributor, and an annular separation and ash fall pipe is connected under the gas distributor, and the lower part of the fluidized bed furnace body is an ash fusion fluidized bed The gasification section, the middle part is the intersection section of the fluidized bed and the entrained bed, and the upper part is the enlarged section. The entrained bed is composed of the entrained bed furnace body, the entrained bed combustion nozzle and the steam connecting pipe. The entrained bed combustion nozzle is located on the top of the entrained bed furnace body. The steam connecting pipe is located in the middle of the entrained bed furnace body, and the lower part of the entrained bed furnace body and the fluidized bed in the middle of the fluidized bed and the confluence section of the entrained bed are connected through the high temperature gas connecting pipe. The coke fine powder circulation control high temperature valve consists of the top of the primary cyclone separator connected to the gasifier gas outlet pipe, the bottom of the primary cyclone separator connected with the semi-coke fine powder circulation standpipe, and the upper end of the semi-coke fine powder circulation control high temperature valve with the The semi-coke fine powder circulation standpipe is connected, and the lower end is connected with the semi-coke fine powder feeding pipe. There is a fine powder return steam blowing pipe on the semi-coke fine powder feeding pipe. connected.

The above-mentioned entrained-bed furnace body and fluidized-bed furnace body are composed of a steel furnace shell, a refractory material and an insulating material, and the insulating material is located between the steel furnace shell and the refractory material.

The above-mentioned gas distributor has a central pipe gasification agent inlet pipe and a distribution plate gasification agent inlet pipe,

The bottom of the above-mentioned annular separation ash-falling pipe is a slag outlet, and the middle part of the annular separation ash-falling pipe is provided with an annular separation pipe gasification agent inlet pipe.

The above-mentioned entrained bed combustion nozzle is connected with a fine powder dense phase conveying pipe and an entrained bed gasification agent inlet pipe.

The present invention has the following advantages:

1) The operating pressure of the gasifier can reach 3.0MPa, with large processing capacity and low compression energy consumption;

2) Selective ash separation, dry slag discharge, low carbon content in ash discharge;

3) After the fine powder entrained by the gas is circulated, it is gasified again at high temperature to achieve complete conversion, thereby increasing the total carbon conversion rate of gasification;

4) The entrained bed gasifier operates at a temperature close to the melting point of ash, and the high-temperature fine ash produced quickly enters the fluidized bed intersection section, realizing the coke-cooled slag, dry slag discharge process, and making full use of sensible heat to separate high-temperature gas and Sensible heat of hot ash is used for coal gasification reaction;

5) It can improve the fluidized bed gasification efficiency and processing capacity, and at the same time improve the effective gas composition;

6) The reactor has a simple structure, no special refractory materials, and low cost; simple operation and long service life;

7) Wide range of coal types, can gasify most coals in China.

Description of drawings

Figure 1 is a schematic diagram of the composite fluidized bed coal gasification device

Figure 2 is a flow chart of the composite fluidized bed coal gasification process

As shown in the figure, 1 is the gas distributor, 2 is the gasification agent inlet pipe of the central pipe, 3 is the gasification agent inlet pipe of the annular separation pipe, 4 is the slag discharge port, 5 is the annular separation ash falling pipe, and 6 is the distribution plate Gasification agent inlet pipe, 7 is steel furnace shell, 8 is refractory material, 9 is insulation material, 10 is coal feed pipe, 11 is lower dense phase fluidized bed gasification section, 12 is fluidized bed and entrained flow bed The intersection section, 13 is the upper expansion section, 14 is the quenching water pipe on the top of the furnace, 15 is the gasifier gas outlet pipe, 16 is the primary cyclone separator, 17 is the semi-coke fine powder circulation standpipe, 18 is the semi-coke fine powder Circulation control high temperature valve, 19 is fine powder return steam blowing pipe, 20 is semi-coke fine powder feeding pipe, 21 is fine powder dense phase conveying pipe, 22 is entrained bed gasification agent inlet pipe, 23 is entrained bed combustion nozzle, 24 is the entrained bed gasification section, 25 is the steam connecting pipe, 26 is the high-temperature gas connecting pipe, 27 is the coal feeding belt conveyor, 28 is the vibration screening machine, 29 is the crusher, 30 is the dryer, 31 is the dry coal 1 #Belt conveyor, 32 is dry coal 1# hoist, 33 is dry coal storage bin, 34 is dry coal 2# belt conveyor, 35 is dry coal 2# hoist, 36 is dry coal balance bucket, 37 is dry Coal inlet hopper, 38 is rotary feeder, 39 is fluidized bed gasifier, 40 is entrained gasifier, 41 is slag discharge upper slag hopper, 42 is slag discharge lower slag hopper, 43 is secondary cyclone Separator, 44 is a secondary cyclone separator to capture fine powder buffer tank, 45 is a secondary cyclone fine powder collection and delivery tank, 46 is a hot gas radiation waste heat recovery boiler, 47 is a hot gas convection waste heat recovery boiler, 48 is a waste heat boiler bubble , 49 is the radiant boiler trap fine powder buffer tank, 50 is the radiant boiler fine powder collection and delivery tank, 51 is the gas ceramic filter, 52 is the ceramic filter fine powder buffer tank, 53 is the ceramic filter trap Fine powder collecting and conveying tank, 54 is a Venturi scrubber, 55 is a tray type water washing tower, 56 is a flash tower, 57 is a gas-water separator, 58 is a crude desulfurization tower, 59 is a gas pressure regulating valve, 60 is 61 is a buffer/weigher for conveying fine powder, 62 is a fine powder storage bin, 63 is a pneumatic conveying pump for fine powder, 64 is a bag filter for feeding fine powder, 65 is a weighing tank for feeding fine powder , 66 is the fine powder feeding balance tank, 67 is the fine powder feeding delivery tank, 68 is the superheated steam sub-cylinder, 69 is the oxygen sub-cylinder, and 70 is the air sub-cylinder.

Detailed ways

Gasification method of the present invention and special equipment thereof are described as follows in conjunction with accompanying drawing:

Example 1:

The composite fluidized bed gasification device is composed of a composite fluidized bed coal gasification furnace and a semi-coke fine powder circulation device. The composite fluidized bed coal gasification furnace is composed of a fluidized bed and an entrained flow bed. The bed is composed of a fluidized bed furnace body, a gasifier gas outlet pipe 15, a gas distributor 1 and an annular separation ash fall pipe 5, and the fluidized bed furnace body is made of a steel furnace shell 7, refractory material 8 and thermal insulation material 9 , the insulation material 9 is located between the steel furnace shell 7 and the refractory material 8, the top of the fluidized bed furnace body has a gasifier gas outlet 15 and furnace top quenching water pipe 14, and the lower part of the fluidized bed furnace body has a coal feed pipe 10 , the bottom of the fluidized bed furnace body is connected to a gas distributor 1, the gas distributor 1 has a central tube gasification agent inlet pipe 2 and a distribution plate gasification agent inlet pipe 6, and the gas distributor 1 is connected with an annular separation and ash fall pipe 5 , the bottom of the annular separation ash pipe 5 is a slagging outlet 4, and the middle part of the annular separation ash pipe 5 has an annular separation pipe gasification agent inlet pipe 3. The lower part of the fluidized bed furnace body is the ash fusion fluidized bed gasification section 11, the middle part is the intersection section 12 of the fluidized bed and the entrained bed, and the upper part is the enlarged section 13. The entrained bed is composed of an entrained bed furnace body and an entrained bed combustion nozzle 23 and the steam connecting pipe 25, the entrained bed combustion nozzle 23 is connected with the fine powder dense phase conveying pipe 21 and the entrained bed gasification agent inlet pipe 22. The entrained bed combustion nozzle 23 is located at the top of the entrained bed furnace body, the steam connecting pipe 25 is located in the middle of the entrained bed furnace body, and the lower part of the entrained bed furnace body and the fluidized bed in the middle of the fluidized bed and the intersecting section 12 of the entrained bed are connected through a high temperature gas connecting pipe 26 , the semi-coke fine powder circulation device is composed of a primary cyclone separator 16 and a semi-coke fine powder circulation control high-temperature valve 18, the top of the primary cyclone separator 16 is connected with the gasifier gas outlet pipe 15, and the bottom of the primary cyclone separator 16 It is connected with the semi-coke fine powder circulation standpipe 17 and the semi-coke fine powder circulation control high temperature valve 18. There is a fine powder return steam blowing pipe 19 on the 20, and the semi-coke fine powder feeding pipe 20 is connected with the lower part of the fluidized bed furnace body.

The raw coal is sent to the vibrating screening machine 28 through the coal feeding belt conveyor 27, and the raw coal with a particle size greater than 6 mm is crushed by the crusher 29 to coal with a particle size less than 6 mm, and enters the dryer 30 together with the raw coal under the vibrating screening machine 28. Drying, coal The moisture content in <5wt%. After drying, through dry coal 1# belt conveyor 31, dry coal 1# hoist 32, enter dry coal storage bin 33 and stand by.

Firstly, the gasification furnace is baked, the furnace air comes from the air distribution cylinder 70, the fuel of the fluidized bed furnace is diesel, the fuel of the entrained bed furnace is methanol, and the air respectively passes through the distribution plate gasification agent inlet pipe 6, and the center Pipe gasification agent inlet pipe 2, annular separation pipe gasification agent inlet pipe 3 enters the fluidized bed gasification furnace; air passes through the entrained bed gasification agent inlet pipe 22 and enters the fine powder combustion nozzle 23, mixes with methanol and burns in the entrained bed. After the temperature of the dense-phase fluidized bed gasification section 11 in the lower part of the fluidized bed gasifier reaches 910°C and the temperature in the upper expansion section reaches 620°C, air of 2500Nm ³ /h and steam are introduced through the air inlet pipes 2, 3, and 6 400kg/h (steam comes from the superheated steam sub-cylinder 68), open the rotary feeder 38 and continuously add gasified coal quantitatively and continuously from the coal feed pipe 10 of the gasifier, keep the coal input at 1000kg/h, and the air volume at 2500Nm ³ /h , steam volume 400kg/h. Establish a bed (the pressure difference in the bed is about 6KPa), switch to oxygen/steam blowing when the temperature, pressure, and flow system reach the set conditions, the oxygen comes from the oxygen distribution cylinder 69, the oxygen intake is 500Nm ³ /h, The steam volume is 1000kg/h, the temperature is controlled at 870°C during the switching process, and then the oxygen and steam flow are slowly adjusted, and the pressure of the gasification system is gradually adjusted to 0.6MP, while the coal input volume is adjusted to 1500kg/h, and the oxygen volume is adjusted to 750Nm ³ / h, the steam volume is up to 1500kg/h, and the temperature is stable at 950°C. At this point the entrained bed is still in the oven stage and kept at 920°C.

After the system is stable, the fine powder is transported from the fine powder feed delivery tank 67 to the entrained bed combustion nozzle 23, and then oxygen and steam are fed into the combustion nozzle 23. Nm ³ /kg, steam-to-coal ratio 0.15kg/kg, and the operating temperature of the entrained bed part is 1180°C. The temperature at the confluence section of the fluidized bed and the entrained bed is 1120°C.

The ash in the gasifier 39 is discharged into the upper slag discharge hopper 41 and the lower slag discharge hopper 42 through the ash falling pipe 5 under the gasifier, and the ash is discharged from the lower slag discharge hopper 42 regularly. During operation, by adjusting the quenching water flow rate in the quenching water pipe 14 on the top of the furnace, the temperature of the gas at the outlet of the gasifier is guaranteed to be less than 900°C. The crude gas is separated by the first-stage cyclone separator 16, and the captured semi-coke fine powder passes through the semi-coke fine powder circulation standpipe 17 and the semi-coke fine powder circulation control high-temperature valve 18, and the fine powder is returned to the steam introduced by the steam blowing pipe 19 Blow into the dense-phase fluidized bed gasification section 11 of the gasifier to participate in the reaction again; the crude gas enters the secondary cyclone separator 43, and the captured semi-coke fine powder is captured by the secondary cyclone separator to capture the fine powder buffer tank 44 , two rotating fine collection and delivery tanks 45 are sent to the fine powder storage bin 62; the high-temperature gas after the coarse separation enters the hot gas radiation waste heat recovery boiler 46, the convection waste heat recovery boiler 47 and the gas ceramic filter 51, and the part in the radiation boiler 46 The fine powder is captured and enters the radiant boiler to capture the fine powder buffer tank 49 and the radiant boiler to capture the fine powder collection and delivery tank 50 and sends it to the fine powder storage bin 62, and the fine powder captured in the ceramic filter passes through the ceramic filter Capture fine powder buffer tank 52 and ceramic filter to capture fine powder collection and delivery tank 53 and send it to fine powder storage bin 62; gas temperature drops to 150-200°C and enters Venturi water scrubber 54, tray type water scrubber 55, gas The water separator 57 and the crude desulfurization tower 58 are further cooled and desulfurized, and then output to the gas purification section through the gas pressure regulating valve 59.

During normal parking, turn off the oxygen of the entrained bed combustion nozzle 23, stop the fine powder delivery, and at the same time increase the steam volume of the combustion nozzle 23 to protect the nozzle, purge and partially cool the entrained bed; cut off the gas entering the rear system Pipeline, coal gas is vented, and the pressure is gradually reduced to normal pressure; after that, reduce the gas velocity of the fluidized bed annular pipe to increase the ash discharge, and at the same time increase the amount of steam in the fluidized bed, close the oxygen valve, and close the coal feeding system of the fluidized bed. The temperature in the furnace is controlled below 900°C; after the charge is exhausted, the air intake is stopped, and finally the system is purged with steam and air respectively.

Example 2:

The fluidized bed coal feed rate is 2300kg/h, the oxygen feed rate is 1100Nm ³ /h, the steam rate is 2000kg/h, the entrained bed fine powder feed rate is 400kg/h, and the dry coal powder ratio of oxygen is 0.53Nm ³ /kg, steam coal The ratio of 0.16kg/kg is operated, the pressure of the gasifier is controlled at 1.0MPa, the temperature at the bottom of the fluidized bed gasifier is stable at 980°C, the operating temperature of the entrained bed part is at 1250°C, and the temperature at the intersection of the fluidized bed and the entrained bed is at 1100°C ℃. All the other are with embodiment 1.

Example 3:

The fluidized bed coal feed rate is 2800kg/h, the oxygen feed rate is 1380Nm ³ /h, the steam rate is 2700kg/h, the entrained bed fine powder feed rate is 600kg/h, and the dry coal powder ratio of oxygen is 0.55Nm ³ /kg, steam coal Operate at a ratio of 0.16kg/kg, the pressure of the gasifier is controlled at 1.5MPa, the temperature at the bottom of the fluidized bed gasifier is stable at 1000°C, the operating temperature of the entrained bed part is at 1200°C, and the temperature at the intersection of the fluidized bed and the entrained bed is at 1090 ℃. All the other are with embodiment 1.

Example 4:

The fluidized bed coal feed rate is 3300kg/h, the oxygen feed rate is 1600Nm ³ /h, the steam rate is 3150kg/h, the fine coal powder feed rate in the middle of the gasifier is 700kg/h, and the dry coal powder ratio according to oxygen is 0.54Nm ³ /kg , The steam-coal ratio is 0.158kg/kg, the pressure of the gasifier is controlled at 2.0MPa, the temperature at the bottom of the fluidized bed gasifier is stable at 1030°C, the operating temperature of the entrained bed part is at 1100°C, and the intersection of the fluidized bed and the entrained bed The temperature is at 1050°C. All the other are with embodiment 1.

Example 5:

The fluidized bed coal feed rate is 3700kg/h, the oxygen feed rate is 1800Nm ³ /h, the steam volume is 3560kg/h, the fine coal powder feed rate in the middle of the gasifier is 800kg/h, and the dry coal powder ratio according to oxygen is 0.7Nm ³ /kg , The steam-to-coal ratio is 0.3kg/kg, the pressure of the gasifier is controlled at 2.5MPa, the temperature at the bottom of the fluidized bed gasifier is stable at 1000°C, the operating temperature of the entrained bed part is at 1300°C, and the intersection of the fluidized bed and the entrained bed The temperature is at 1150°C. All the other are with embodiment 1.

The gas composition of the new solid-state slagging dry powder entrained bed coal gasification to produce synthesis gas under the conditions of Examples 1-5 is listed in Table 1.

Table 1 Gas composition of multi-stage staged conversion fluidized bed coal gasification to synthesis gas under different conditions

Example 1 Example 2 Example 3 Example 4 Example 5 Gasification pressure, MPa 0.6 1.0 1.5 2.0 2.5 Coal feed into fluidized bed, kg/h 1500 2300 2800 3300 3700 Air bed fine powder amount, kg/h 300 400 600 700 800 Total oxygen intake, Nm ³ /h 860 1312 1710 1978 2360 Total steam volume, kg/h 1530 2064 1796 3260.6 3800 Dry gas composition Vol.% H ₂ 36.43 38.04 37.72 37.23 37.98 N ₂ 8.8 5.17 5.54 6.05 5.57 CO 24.36 25.62 26.85 26.8 28.16 CH ₄ 4.61 5.17 5.09 5.32 5.69 CO ₂ 25.8 26 24.8 24.6 22.6 Gas production rate Nm3/kg 2.04 2.03 2.04 2.05 2.07 Calorific value of gas Kcal/Nm ³ 2073.4 2192.7 2243.77 2320.8 2352.8 Carbon Conversion % 93.5 93 93.2 93.6 94 Cold Gas Efficiency % 73.67 73.42 73.51 74.21 74.39

Claims (6)

1. a method for compound fluidized bed coal gasification, is characterized in that comprising the steps: (1) Preparation of raw coal for gasification After the raw coal is crushed, it is dried and screened so that the coal moisture is less than 5wt%, and the particle size is less than 6mm, which is sent to the coal bunker as raw coal for fluidized bed gasification; the fine powder comes from semi-coke fine powder that has not completely reacted during the gasification process, The fine powder collected by the cyclone, radiant waste heat boiler and high temperature ceramic filter; (2) Gasification a. First, bake the gasifier. When the temperature of the lower part of the fluidized bed gasifier is greater than 900°C and the temperature of the upper part is greater than 600°C, air and steam are introduced into the gas distributor at the lower part of the fluidized bed, The gasification crushed coal is continuously added to the feed port, and the air-to-coal ratio is 2.5-3.5Nm ³ /kg, and the steam-to-coal ratio is 0.3-0.6kg/kg, so that the coal is burned in the gasifier and the semi-coke furnace charge is obtained. , and gradually build up the material in the gasifier furnace, at this time the entrained flow bed is still in the oven stage and kept at 850-900°C; b. When the bed pressure drop of semi-coke materials in the fluidized bed gasifier reaches 5-10KPa, switch to oxygen/steam blowing after the system operation is stable, and the temperature is controlled at 800-900°C during the switching process; c. Operate with an oxygen-to-coal ratio of 0.4-0.5Nm ³ /kg and a steam-to-coal ratio of 0.5-1.0kg/kg, and the temperature at the bottom of the fluidized bed gasifier is stable in the range of 950-1050°C; d. After the gasification of the lower part of the fluidized bed gasifier is stabilized, the fine powder is transported from the fine powder delivery tank to the entrained bed combustion nozzle, and then oxygen and steam are fed into the combustion nozzle. The ratio of oxygen to dry coal powder is 0.5-0.7Nm ³ /kg, steam-coal ratio 0.1-0.3kg/kg, the operating temperature of the entrained bed is in the range of 1100-1300°C, and the temperature of the intersection of the fluidized bed and the entrained bed in the fluidized bed is in the range of 1050-1150°C; (3) Slagging of gasifier During the gasification process, adjust the gas velocity of the annular separation tube at 5-10m/s, and the oxygen concentration in the gas <25Vol%; the gas velocity of the central jet tube is 15-30m/s, and the oxygen concentration in the gas is 40-60vol%, so that The height of the semi-coke charge in the gasifier is kept so that the bed pressure difference is between 4 and 8KPa; (4) Purification of crude gas and recovery of waste heat Spray chilled water at the outlet of the gasifier to ensure that the cyclone inlet temperature is less than 900°C. The crude gas is separated by the first-stage cyclone separator, and the captured semi-coke fine powder is blown into the pyrolysis through the standpipe and the high-temperature fine powder control valve. The dense phase fluidized bed gasification section at the lower part of the gasification reactor participates in the reaction again; the crude gas enters the secondary cyclone separator, and the captured semi-coke fine powder is sent to the semi-coke fine powder collection/cooling tank and fine powder conveyor. into the fine powder storage bin; the coarsely separated high-temperature gas enters the radiant waste heat boiler, convection waste heat boiler and gas ceramic filter, and the gas temperature drops to 150-200°C and enters the Venturi water scrubber and water-cooled leaching tower for further cooling and dust removal After that, it is exported to the gas purification section, and the semi-coke fine powder collected by the radiant waste heat boiler and ceramic filter is also sent to the fine powder storage bin through the semi-coke fine powder collection/cooling tank and fine powder conveyor; (5) Conveying of fine powder The fine powder collected by the secondary cyclone, radiant waste heat boiler and ceramic filter enters the fine powder storage bin, and the fine powder is sent to the fine powder feeding weighing tank through the pneumatic conveying pump, and then enters the fine powder feeding balance tank and fine powder feeding The delivery tank is blown by nitrogen to send the fine powder into the entrained bed combustion nozzle for gasification. 5. Gasifier shutdown During normal parking, turn off the oxygen of the entrained bed combustion nozzle, stop the fine powder delivery, and at the same time increase the steam volume of the combustion nozzle to protect the nozzle, purge and cool down the entrained bed part; cut off the gas pipeline entering the system, The gas is vented, and the pressure is gradually reduced to normal pressure; after that, the gas velocity of the fluidized bed annular pipe is reduced to increase the ash discharge capacity, and at the same time, the amount of steam used in the fluidized bed is increased, the oxygen valve is closed, and the coal feeding system of the fluidized bed is closed. The temperature is controlled below 900°C; after the charge is discharged, the air intake is stopped, and finally the system is purged with steam and air respectively. 2. as the composite fluidized bed gasification device of the method for a kind of composite fluidized bed coal gasification as claimed in claim 1, it is made of composite fluidized bed coal gasification furnace, semi-coke fine powder circulation device Composition, it is characterized in that described composite fluidized bed coal gasifier is made up of fluidized bed and entrained flow bed, and fluidized bed is made of fluidized bed furnace body, gasifier gas outlet pipe (15), gas distributor (1) is composed of an annular separation ash pipe (5), the top of the fluidized bed furnace body has a gasifier gas outlet (15) and furnace top quenching water pipe (14), and the lower part of the fluidized bed furnace body has a coal feed pipe (10), the bottom of the fluidized bed furnace body is connected to the gas distributor (1), and the gas distributor (1) is connected with an annular separation ash falling pipe (5), and the lower part of the fluidized bed furnace body is ash fusion and fluidization Bed gasification section (11), the middle part is the intersection section (12) of fluidized bed and entrained bed, and the upper part is enlarged section (13). The entrained bed is composed of entrained bed furnace body, entrained bed combustion nozzle (23) and steam connecting pipe (25) composition, entrained bed combustion nozzle (23) is positioned at the top of entrained bed furnace body, and steam connecting pipe (25) is positioned at the middle part of entrained bed furnace body, and the fluidized bed and entrained bed intersection of entrained bed furnace body lower part and fluidized bed middle part Section (12) is connected by high-temperature gas connecting pipe (26), and the semi-coke fine powder circulation device is composed of a first-stage cyclone separator (16), a semi-coke fine powder circulation control high-temperature valve (18), and a first-stage cyclone separator (16 ) top is connected with the gasifier gas outlet pipe (15), the bottom of the primary cyclone separator (16) is connected with the semi-coke fine powder circulation standpipe (17), and the upper end of the semi-coke fine powder circulation control high temperature valve (18) is connected with the semi-coke fine powder circulation control valve (18). The coke fine powder circulation standpipe (17) is connected, and the lower end is connected with the semi-coke fine powder feed pipe (20). The powder feeding pipe (20) is connected with the lower part of the fluidized bed furnace body. 3. the composite fluidized bed gasification device of the method for a kind of composite fluidized bed coal gasification as claimed in claim 2, it is characterized in that described fluidized bed furnace body is made of steel shell (7), The refractory material (8) and the thermal insulation material (9) are made, and the thermal insulation material (9) is located between the steel furnace shell (7) and the refractory material (8), 4. the composite fluidized bed gasification device of the method for a kind of composite fluidized bed coal gasification as claimed in claim 2, it is characterized in that described gas distributor (1) has central pipe gasification agent inlet pipe (2) and distribution plate gasification agent inlet pipe (6). 5. the composite fluidized bed gasification device of the method for a kind of composite fluidized bed coal gasification as claimed in claim 2, it is characterized in that the bottom of described annular separation ash falling pipe (5) is slagging outlet (4), the middle part of the ring-shaped separating ash-falling pipe 5 has an annular separating pipe gasification agent inlet pipe (3). 6. the composite fluidized bed gasification device of the method for a kind of composite fluidized bed coal gasification as claimed in claim 2, it is characterized in that described entrained bed combustion nozzle (23) is connected with fine powder dense phase conveying Pipe (21) and entrained bed gasification agent inlet pipe (22).

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