CN111849560B

CN111849560B - Device and method for combined production of biochar by coupling gasification of reciprocating grate with coal-fired power generation

Info

Publication number: CN111849560B
Application number: CN202010734561.XA
Authority: CN
Inventors: 别如山
Original assignee: Harbin Institute of Technology
Current assignee: Harbin Institute of Technology
Priority date: 2020-07-27
Filing date: 2020-07-27
Publication date: 2021-04-20
Anticipated expiration: 2040-07-27
Also published as: CN111849560A

Abstract

A device and a method for combined production of biochar by gasification of a reciprocating grate and coupling coal-fired power generation belong to the technical field of new energy. The biomass reciprocating furnace exhaust gasifier comprises a reciprocating grate and a gasification furnace arranged on the upper portion of the reciprocating grate, at least six air chambers are arranged on the lower portion of the reciprocating grate, an open U-shaped water-cooling auger is arranged at the tail end of the reciprocating grate, a biochar water-cooling auger I is arranged at an outlet of the open U-shaped water-cooling auger, an outlet of the top of the gasification furnace is connected with an inlet of a vertical gradually-reducing and gradually-expanding cracker, an outlet of the vertical gradually-reducing and gradually-expanding cracker is connected with an inlet of a cyclone separator, a biochar water-cooling auger II is arranged at an outlet of the lower portion of the cyclone separator, a fuel gas outlet of the cyclone separator is connected with a large coal-fired boiler through an induced draft fan, a fuel gas valve is arranged between the induced draft fan and. The biomass gasification combined biomass charcoal gasification combined coal-fired power generation device is used for biomass gasification coupled coal-fired power generation and biochar co-production.

Description

Device and method for combined production of biochar by coupling gasification of reciprocating grate with coal-fired power generation

Technical Field

The invention belongs to the technical field of new energy, and particularly relates to a device and a method for biomass reciprocating grate gasification coupled coal-fired power generation and biochar co-production.

Background

Biomass gasification is a technology for thermochemically converting biomass into combustible gas, and the principle is that the biomass is incompletely combusted under the anoxic condition in a gasification furnace, and the released heat converts the biomass into CO and H₂、CH₄、CO₂And biochar and the like, wherein the biochar can be used as a steel mill molten steel heat insulation material, a soil conditioner, a fertilizer slow release carrier, a raw material of activated carbon and the like; the biomass gasified gas can be fed into a gas boiler for combustion and heat supply, and also can be fed into a high-capacity high-parameter coal-fired boiler for coupling power generation, the advantages of high power generation efficiency of the coal-fired boiler and centralized treatment and ultralow emission of pollutants are utilized, the biomass power generation efficiency is greatly improved, the economical efficiency of a power plant is improved, and simultaneously, the CO per KW is reduced₂And (4) discharging the amount. The existing biomass gasification furnaces comprise an updraft fixed bed gasification furnace, a downdraft fixed bed gasification furnace, a chain grate gasification furnace, a fluidized bed and a circulating fluidized bed gasification furnace. The capacities of an updraft fixed bed gasification furnace and a downdraft fixed bed gasification furnace are smaller, and the biomass treatment capacity is less than 3 t/h; the chain grate gasification furnace is only applied to rice hull gasification at present, the rice hull treatment capacity is not more than 3t/h, and when massive biomass is gasified, the problem of gasification impermeability exists, namely the biomass cannot be completely carbonized. The circulating fluidized bed is almost the only choice to meet the requirement of large coal-fired boiler coupled biomass gasification power generation, but the circulating fluidized bed has higher requirements on biomass granularity and moisture, and the expected granularity of wood particlesLess than 20mm, and for straw, it is undesirable for the length to exceed 50mm, while the moisture content of the biomass does not exceed 15%. The biomass charcoal obtained by the circulating fluidized bed gasification furnace is usually particles and powder with the particle size of less than 6mm, and the circulating fluidized bed is not enough for biomass which is expected to obtain massive biomass charcoal or does not change the original shape of the biomass and has the moisture content of more than 15%. In addition, because the temperature of the fuel gas at the outlet of the gasification furnace is 700-. In the prior art, a heat conduction oil heat exchanger is adopted to cool combustible gas to 450 ℃, then heat conduction oil and water or air and the like carry out secondary heat exchange, the heat conduction oil heat exchanger has the defects of large heat exchange area, high investment cost and complex system, the highest allowable heating temperature of the heat conduction oil at present is 360 ℃, therefore, the wall surface temperature of the heat conduction oil heat exchanger is lower than 400 ℃, macromolecular tar is easy to contaminate on the heat exchanger, the heat transfer is influenced, and the heat exchanger needs to be cleaned regularly.

Disclosure of Invention

The invention aims to solve the problems of the prior chain grate furnace exhaust gasifier, the circulating fluidized bed gasifier and the combustible gas cooling, and further provides a device and a method for co-producing biochar by coupling gasification of a reciprocating grate and coal-fired power generation, so as to achieve the aim of efficiently producing biochar while realizing biomass gasification and coal-fired coupled power generation.

In order to solve the technical problems, the invention adopts the technical scheme that:

a device for co-production of biochar by gasification coupling of a reciprocating grate and coal-fired power generation comprises a biomass reciprocating grate gasifier, a vertical gradually-reducing and gradually-expanding cracker, an open U-shaped water-cooling auger, a rotary valve feeder, a cyclone separator, an induced draft fan, a gas valve, a biochar water-cooling auger I, a biochar water-cooling auger II, a diffusion burner, an emptying valve and at least six air chambers;

the biomass reciprocating furnace exhaust gasifier comprises a reciprocating grate and a gasification furnace hearth arranged on the upper part of the reciprocating grate, wherein the lower part of the reciprocating grate is provided with at least six air chambers, the tail end of the reciprocating grate is provided with an open U-shaped water-cooling auger, the outlet of the open U-shaped water-cooling auger is provided with a biochar water-cooling auger I, the outlet at the top of the gasification furnace hearth is connected with the inlet of a vertical gradually-reducing and gradually-expanding cracker, the outlet of the vertical gradually-reducing and gradually-expanding cracker is connected with the inlet of a cyclone separator, the biochar water-cooling auger II is arranged at the outlet of the cyclone separator, the gas outlet of the cyclone separator is connected with the inlet of an induced draft fan, the outlet of the induced draft fan is connected with a large coal-fired boiler, a gas valve is arranged between the induced draft fan and the large coal-fired boiler, the, an exhaust valve is arranged on the fuel gas bleeding opening.

A method for combined production of biochar by gasification of a reciprocating grate and coupling coal-fired power generation comprises the following steps:

the method comprises the following steps: biomass fuel is pushed into a gasification furnace chamber to be gasified through a movable grate segment of a reciprocating grate, and biochar obtained after gasification is pushed into an open U-shaped water-cooling auger; in the process of gasifying the biomass fuel, at least six air chambers supply air to a gasification furnace chamber, the air supply amount accounts for 25-40% of theoretical air amount, and the temperature in the gasification furnace chamber is controlled to be between 700 and 800 ℃;

step two: the biomass with the particle size of less than 5mm and the moisture of less than 15 percent is sent into a combustible gas pipeline with the temperature of 700-; combustible gas at the top of the cyclone separator enters the large coal-fired boiler under the action of the induced draft fan.

Compared with the prior art, the invention has the beneficial effects that: the adoption of the biomass reciprocating furnace exhaust gasifier solves the severe requirements of the circulating fluidized bed on moisture and granularity, and can obtain biochar with the original shape; the reciprocating grate has a fire poking function (in the prior art), and solves the problem of incomplete gasification of the exhaust gasifier of the chain grate furnace; the manufacturing cost of the biomass reciprocating grate gasifier is only 1/2 of the circulating fluidized bed gasifier with the same volume, and a high-pressure fan is not needed, so that the power consumption of the fan is obviously reduced. The high-temperature fuel gas generated by biomass gasification is utilized to carbonize biomass in the vertical gradually-reducing and gradually-expanding cracker to co-produce biochar, thereby solving the problem of fuel gas cooling and achieving the dual effects of power generation and biochar co-production. The biomass gasification combined biomass charcoal gasification combined coal-fired power generation device is used for biomass gasification coupled coal-fired power generation and biochar co-production.

Drawings

FIG. 1 is a schematic structural diagram of a biomass reciprocating grate gasification coupled coal-fired power generation and biochar co-production device of the invention;

FIG. 2 is a partial view of a vertical tapered and diverging cracker;

FIG. 3 is a view from direction K of FIG. 1; in the figure W represents the width of the gasification furnace;

FIG. 4 is an enlarged view of a portion of the reciprocating grate 2;

FIG. 5 is a front and rear arch structure view of a biomass reciprocating grate gasifier.

The names and reference numbers of the components referred to in the above figures are as follows:

biomass reciprocating grate gasifier 1, reciprocating grate 2, air chamber I2-1, air chamber II 2-2, air chamber III 2-3, air chamber IV 2-4, air chamber V2-5, air chamber VI 2-6, movable grate segment 2-7, fixed grate segment 2-8, stokehold hopper 3, vertical gradually-reducing and gradually-expanding cracker 4, descending section 4-1, cylinder III 4-1-1, cylinder IV 4-1-2, ascending section 4-2, cylinder I4-2-1, cylinder II 4-2-2, elbow 4-3, open U-shaped water-cooling auger 5, rotary valve feeder 6, cyclone separator 7, draught fan 8, draught fan valve 9, large coal-scale boiler 10, biochar water-cooling auger I11, biochar water-cooling auger II 12, diffusion burner 13, coke-discharging burner 13, An emptying valve 14, a first rotary sealing valve 15, a second rotary sealing valve 16 and a blower 17.

Detailed Description

The first embodiment is as follows: as shown in fig. 1-5, the present embodiment discloses a device for combined production of biochar by gasification and coupling of a reciprocating grate and coal-fired power generation, comprising a biomass reciprocating grate gasifier 1, a vertical gradually-reducing and gradually-expanding cracker 4, an open U-shaped water-cooling auger 5, a rotary valve feeder 6, a cyclone separator 7, an induced draft fan 8, a gas valve 9, a biochar water-cooling auger I11, a biochar water-cooling auger II 12, a diffusion burner 13, an emptying valve 14, a stokehole hopper 3 and at least six air chambers,

the biomass reciprocating grate gasification furnace 1 comprises a reciprocating grate 2 (as shown in figures 1 and 4, the reciprocating grate is composed of fixed grate segments 2-8 and movable grate segments 2-7, the reciprocating grate has a stirring function and can completely carbonize biomass, but the conventional coal-fired reciprocating grate cannot be used for biomass gasification because the height and the pushing range of the movable grate segments 2-7 are far smaller than those required by the biomass gasification furnace, the reciprocating grate used by the biomass gasification furnace has the movable grate segments 2-7 with the height H of 100 plus 200mm and the pushing range L of 220 plus 400mm, in addition, the included angle alpha 1 between the reciprocating grate and the horizontal plane is 0-21 degrees as shown in figure 5) and a gasification furnace hearth arranged at the upper part of the reciprocating grate 2, the lower part of the reciprocating grate 2 is provided with at least six air chambers, the front hopper 3 is arranged at the upper end of the reciprocating grate 2, an opening U-shaped water-cooling auger 5 is arranged at the tail end of the reciprocating grate 2 (in the prior art), a biochar water-cooling auger I11 is arranged at the outlet of the opening U-shaped water-cooling auger 5, a top outlet of the gasification hearth is connected with an inlet of a vertical reducing and gradually expanding cracker 4, an outlet of the vertical reducing and gradually expanding cracker 4 is connected with an inlet of a cyclone separator 7, a biochar water-cooling auger II 12 is arranged at a biochar outlet of the cyclone separator 7, a gas outlet of the cyclone separator 7 is connected with an inlet of an induced draft fan 8, an outlet of the induced draft fan 8 is connected with a gas burner of a large coal-sized boiler 10 (the power is at least more than 300 megawatts and usually between 600 plus 1000 megawatts), a gas valve 9 (used for cutting off the connection between the biomass reciprocating grate gasifier 1 and the large-sized boiler 10 in an emergency situation) is arranged between the induced draft fan 8 and the large, through rotary valve feeder 6 with the particle diameter less than 5mm, the moisture is less than the living beings (like rice husk, saw-dust etc.) of 15% and gets into vertical convergent divergent cracker 4 after the high temperature gas mixes, living beings granule and combustible gas intensive mixing, dry distillation generate biomass charcoal and gas, gasification furnace top is equipped with the gas mouth that diffuses, the gas mouth tip that diffuses is equipped with diffuses combustor 13 (prior art), is equipped with blowoff valve 14 on the gas mouth that diffuses. When the gas valve 9 is closed, the evacuation valve 14 is opened to discharge the combustible gas to the outside, and at the same time, the diffusion burner 13 provided at the end of the gas diffusion port is ignited to burn the gas.

The second embodiment is as follows: as shown in fig. 1 and fig. 3, in the present embodiment, a first rotary sealing valve 15 is disposed at an outlet of the first biochar water-cooling auger 11, a second rotary sealing valve 16 is disposed at an outlet of the second biochar water-cooling auger 12, and the first rotary sealing valve 15 and the second rotary sealing valve 16 perform a sealing function, so as to prevent air from leaking into fuel gas and avoid explosion accidents.

The third concrete implementation mode: as shown in fig. 1, the present embodiment is a further description of the first embodiment, the number of the air chambers is six, six air chambers are, along the running direction (front-back direction) of the reciprocating grate 2, sequentially a first air chamber 2-1, a second air chamber 2-2, a third air chamber 2-3, a fourth air chamber 2-4, a fifth air chamber 2-5 and a sixth air chamber 2-6, and the air supply amounts of the six air chambers sequentially account for 15%, 20%, 15% and 10% of the total air amount. Six air chambers are supplied by blowers 17. This embodiment can effectively control temperature in the gasification furnace, avoids local high temperature to lead to the slagging scorification.

The fourth concrete implementation mode: as shown in fig. 1 and fig. 2, the first embodiment is further described, the vertical gradually-decreasing and gradually-expanding cracker 4 is of a 'snake' structure, the vertical gradually-decreasing and gradually-expanding cracker 4 (the vertical gradually-decreasing and gradually-expanding cracker 4 adopts a gradually-decreasing and gradually-expanding structure, which is beneficial to fully and uniformly mixing biomass and high-temperature fuel gas) is alternately arranged from an inlet to an outlet in sequence by a descending section 4-1 and an ascending section 4-2, and the descending section 4-1 and the ascending section 4-2 are connected and combined by an elbow 4-3;

the ascending section 4-2 is formed by coaxially and sequentially and alternately arranging a plurality of cylinders I4-2-1 and a plurality of cylinders II 4-2-2, the lower end of each cylinder I4-2-1 is connected with the upper end of each cylinder II 4-2-2 through a necking I, the lower end of each cylinder II 4-2-2 is connected with the upper end of each cylinder I4-2-1 through a flaring I, the flaring I at the lower end of each cylinder II 4-2-2 is combined with the cylinder I4-2-1 to form an expanding section I, and the necking I at the lower end of each cylinder I4-2-1 is combined with the cylinder II 4-2-2 to form a contracting section I;

the descending section 4-1 is formed by coaxially and sequentially and alternately arranging a plurality of cylinders three 4-1-1 and a plurality of cylinders four 4-1-2, the lower end of each cylinder three 4-1-1 is connected with the upper end of the cylinder four 4-1-2 through a necking II, the lower end of each cylinder four 4-1-2 is connected with the upper end of the cylinder three 4-1-1 through a flaring II, the flaring II at the lower end of each cylinder four 4-1-2 is combined with the cylinder three 4-1-1 to form an expanding section II, and the necking II at the lower end of each cylinder three 4-1-1 is combined with the cylinder four 4-1-2 to form a contracting section II. The structure ensures that the high-temperature fuel gas and the biomass are fully mixed, so that the biomass can be completely carbonized after staying for 8-10 s.

The fifth concrete implementation mode: as shown in fig. 1 and 2, in the fourth embodiment, in the ascending section 4-2, the gas velocity of the contracting section one is 18-20m/s, the gas velocity of the expanding section one is 14-16m/s, the distance between the middle parts of the two adjacent cylinders one 4-2-1 is one pitch one L1, the diameter of the inner wall of the cylinder two 4-2-2 is d1, and L1/d1 is 4-6. The ascending air flow needs to carry biomass particles, so the air speed must reach more than 14m/s, otherwise, the biomass particles cannot be carried away with the air flow, and usually 14-16m/s is taken; while the speed of the constriction needs to be 18-20m/s to achieve good mixing, too high a speed is not necessary, since the resistance is proportional to the square of the speed.

In the descending section 4-1, the second contracting section air speed is 8-10m/s, the second expanding section air speed is 5-6m/s, the distance between the middle parts of two adjacent cylinders three 4-1-1 is a pitch two L2, the diameter of the inner circular wall of the cylinder four 4-1-2 is D1, and L2/D1 is 4-6. In the descending section 4-1, in order to increase the retention time, the speed of the expanding section is selected to be 5-6m/s, and the speed of the contracting section is 8-10 m/so as to ensure good mixing; if the speed of the expansion section is lower, the diameter is larger, the material quantity is increased, and the investment is increased; the two speeds of the constriction zone below 8m/s do not mix well and the drag increases more above 10 m/s.

The sixth specific implementation mode: as shown in fig. 1 to 4, the present embodiment discloses a method for realizing the gasification and coupling of a reciprocating grate and coal-fired power generation for co-production of biochar by using the device according to any one of embodiments 1 to 5, which comprises the following steps:

the method comprises the following steps: the movable grates 2-7 of the reciprocating grate 2 are arranged on the fixed grate segments 2-8, biomass fuel is pushed into the gasification furnace chamber to be gasified through the movable grates 2-7 of the reciprocating grate 2, and biomass charcoal obtained after gasification is pushed into the lower layer from the upper layer until the biomass charcoal is pushed into the open U-shaped water-cooling auger 5; the push distance L of the movable grate segment 2-7 is 400mm, and the height H of the movable grate segment 2-7 is 200 mm; the included angle between the reciprocating grate and the horizontal plane is 0-21; in the gasification process of the biomass fuel, at least six air chambers supply air to the gasification furnace, the air supply amount is 25-40% of the theoretical air amount (the high value is taken when the water content is high) according to the difference of the biomass fuel and the water content, a steam spray gun is arranged below each air chamber, when the temperature of the local furnace exceeds 800 ℃, steam is sprayed, and the temperature in the gasification furnace is controlled between 700-800 ℃;

step two: in order to solve a series of problems caused by the reduction of the temperature of fuel gas by the heat transfer oil, the biomass with the particle size of less than 5mm and the moisture of less than 15 percent is sent into a combustible gas pipeline with the temperature of 700-, and the biomass and the high-temperature combustible gas enter a vertical type reducing and gradually expanding cracker 4 together to carbonize the biomass (the biomass and the combustible gas with the high temperature of 700 and 800 ℃ are fully mixed and carbonized to generate the biochar and the fuel gas), the retention time of the biomass is 8-10s, which is enough to carbonize the biomass, the biomass feeding amount is adjusted by adjusting the rotating speed of the rotary discharge valve 6, the temperature of the combustible gas is reduced from 700-plus 800 ℃ to 450 ℃ (so as to avoid a heat-conducting oil heat exchanger), then the combustible gas enters the cyclone separator 7 to separate the biochar, and the biochar enters the biochar water-cooling auger II 12 to be recovered after the temperature is reduced to below 150 ℃; combustible gas at the top of the cyclone separator 7 enters a large coal-fired boiler 10 under the action of an induced draft fan 8. The method has the advantages that the temperature in the gasification furnace hearth is controlled to be 700-; the biomass cracking heat absorption cooling is adopted, a heat conduction oil heat exchanger is omitted, and further expensive equipment investment is avoided. Meanwhile, the biochar and the fuel gas at 450 ℃ are obtained and are directly sent into a large coal-fired boiler 10 through an induced draft fan 8 to be coupled for power generation.

The seventh embodiment: the embodiment is further explained with respect to the sixth embodiment, in the first step, the biomass fuel includes straw bulk materials, straw briquettes and wood bars, and the adding amount of the biomass fuel is 5-40 t/h.

The specific implementation mode is eight: the seventh embodiment is further explained, the moisture of the straw bulk material is less than 35%, and the longest straw bulk material is not more than 150 mm; the cross section size of the straw briquetting is as follows: width x height 32 x 32mm, length less than 100mm (moisture less than 15%); the moisture of the wood bar stock is less than 25%, and the section size is as follows: the width multiplied by the height is less than 40 multiplied by 40mm, and the length is less than 200 mm. The beneficial effects of the embodiment are: gasifying the high-moisture straw bulk materials, and carbonizing wood bar materials and briquettes (generally, the moisture content is less than 15%) with the moisture content of less than 25%, so that all the results are obtained, and the functions of stirring by using a reciprocating grate and gasifying at the temperature of 800 ℃ are benefited by using the fire stirring function of the reciprocating grate.

The specific implementation method nine: as shown in fig. 1, the present embodiment is further described with respect to a sixth embodiment, in the first step, the number of the air chambers is six, the six air chambers sequentially include, along the traveling direction (i.e., the front-rear direction) of the reciprocating grate 2, a first air chamber 2-1, a second air chamber 2-2, a third air chamber 2-3, a fourth air chamber 2-4, a fifth air chamber 2-5, and a sixth air chamber 2-6, and the air supply volumes of the six air chambers sequentially account for 15%, 20%, 15%, and 10% of the total air volume.

The detailed implementation mode is ten: in the second step, the biomass is all the biomass with the grain size of less than 5mm and the water content of less than 15%. Rice hulls and wood chips are preferably considered for the biomass.

The concrete implementation mode eleven: as shown in fig. 1 and fig. 2, in the present embodiment, a sixth specific embodiment is further described, in the second step, the vertical gradually-decreasing and gradually-expanding cracker 4 is of a 'snake' -shaped structure, and the vertical gradually-decreasing and gradually-expanding cracker 4 (the vertical gradually-decreasing and gradually-expanding cracker 4 adopts a gradually-decreasing and gradually-expanding structure, which is beneficial to sufficiently and uniformly mixing biomass and high-temperature fuel gas) is sequentially and alternately arranged from an inlet to an outlet by a descending section 4-1 and an ascending section 4-2, and the two are connected and combined by an elbow 4-3;

the descending section 4-1 is formed by coaxially and sequentially and alternately arranging a plurality of cylinders III 4-1-1 and a plurality of cylinders IV 4-1-2, the lower end of each cylinder III 4-1-1 is connected with the upper end of the cylinder IV 4-1-2 through a necking II, the lower end of each cylinder IV 4-1-2 is connected with the upper end of the cylinder III 4-1-1 through a flaring II, the flaring II at the lower end of each cylinder IV 4-1-2 is combined with the cylinder III 4-1-1 to form an expanding section II, and the necking II at the lower end of each cylinder III 4-1-1 is combined with the cylinder IV 4-1-2 to form a contracting section II;

in the ascending section 4-2, the gas velocity of the contraction section I is 18-20m/s, the gas velocity of the expansion section I is 14-16m/s, the distance between the middle parts of two adjacent cylinders I4-2-1 is one pitch I1, the diameter of the inner circular wall of the cylinder II 4-2-2 is d1, and the L1/d1 is 4-6;

in the descending section 4-1, the second contracting section air speed is 8-10m/s, the second expanding section air speed is 5-6m/s, the distance between the middle parts of two adjacent cylinders three 4-1-1 is a pitch two L2, the diameter of the inner circular wall of the cylinder four 4-1-2 is D1, and L2/D1 is 4-6.

The size of the front arch and the rear arch of the gasification furnace is as follows: the included angle alpha 2 between the front arch and the horizontal plane is 38-42 degrees, the height L6 of the straight section of the front arch is 1.0-1.5m, and the front arch covers the length of the reciprocating grate: L3/L5 is more than or equal to 30 percent; the included angle alpha 3 between the rear arch and the horizontal is 12-30 degrees, the vertical height L7 between the tail end of the rear arch and the surface of the grate is 0.5-0.8m, and the rear arch covers the length of the reciprocating grate: and L4/L5 is 50% -60%. The length of the front arch and the rear arch covering the reciprocating grate is ensured to reach 80-90 percent, so that biomass bulk materials with high moisture (less than or equal to 35 percent), wood bars (blocks) with moisture less than or equal to 25 percent and biomass pressed blocks (moisture less than or equal to 15 percent) can be completely carbonized, as shown in figure 5. Wherein L3 is the length of the front arch horizontal projection, L5 is the length of the reciprocating grate horizontal projection, and L4 is the length of the rear arch horizontal projection.

Claims

1. A device for the gasification coupling of a reciprocating grate and the coal-fired power generation and the co-production of biochar is characterized in that: the biomass gasification furnace comprises a biomass reciprocating grate gasification furnace (1), a vertical gradually-reducing and gradually-expanding cracker (4), an open U-shaped water-cooling auger (5), a rotary valve feeder (6), a cyclone separator (7), an induced draft fan (8), a gas valve (9), a biochar water-cooling auger I (11), a biochar water-cooling auger II (12), a diffusion burner (13), an exhaust valve (14) and at least six air chambers;

the biomass reciprocating grate gasification furnace (1) comprises a reciprocating grate (2) and a gasification furnace arranged on the upper part of the reciprocating grate (2), wherein at least six air chambers are arranged on the lower part of the reciprocating grate (2), an opening U-shaped water-cooling auger (5) is arranged at the tail end of the reciprocating grate (2), a biochar water-cooling auger (11) is arranged at the outlet of the opening U-shaped water-cooling auger (5), the outlet of the top of the gasification furnace is connected with the inlet of a vertical gradually reducing and expanding cracker (4), the outlet of the vertical gradually reducing and expanding cracker (4) is connected with the inlet of a cyclone separator (7), a biochar water-cooling auger (12) is arranged at the outlet of the cyclone separator (7), the gas outlet of the cyclone separator (7) is connected with the inlet of an induced draft fan (8), the outlet of the induced draft fan (8) is connected with a large coal-fired boiler (10), and a gas valve (9) is arranged, a rotary valve feeder (6) is arranged at the inlet of the vertical type reducing and gradually expanding cracker (4), a fuel gas dispersing port is arranged at the top of the gasification hearth, a dispersing burner (13) is arranged at the end part of the fuel gas dispersing port, and an emptying valve (14) is arranged on the fuel gas dispersing port; the vertical type gradually-reducing and gradually-expanding cracker (4) is of a 'snake' -shaped structure, the vertical type gradually-reducing and gradually-expanding cracker (4) is formed by alternately arranging a descending section (4-1) and an ascending section (4-2) from an inlet to an outlet in sequence, and the descending section and the ascending section are connected and combined by a bent pipe (4-3);

the ascending section (4-2) is formed by coaxially and alternately arranging a plurality of cylinders I (4-2-1) and a plurality of cylinders II (4-2-2) in sequence, the lower end of each cylinder I (4-2-1) is connected with the upper end of each cylinder II (4-2-2) through a necking I, the lower end of each cylinder II (4-2-2) is connected with the upper end of each cylinder I (4-2-1) through a flaring I, the flaring I at the lower end of each cylinder II (4-2-2) is combined with the cylinder I (4-2-1) to form a flaring section I, and the necking I at the lower end of each cylinder I (4-2-1) is combined with the cylinder II (4-2-2) to form a shrinking section I;

the descending section (4-1) is formed by coaxially and sequentially and alternately arranging a plurality of cylinders three (4-1-1) and a plurality of cylinders four (4-1-2), the lower end of each cylinder three (4-1-1) is connected with the upper end of each cylinder four (4-1-2) through a necking II, the lower end of each cylinder four (4-1-2) is connected with the upper end of each cylinder three (4-1-1) through a flaring II, the flaring II at the lower end of each cylinder four (4-1-2) is combined with the cylinder three (4-1-1) to form a flaring section II, and the necking II at the lower end of each cylinder three (4-1-1) is combined with the cylinder four (4-1-2) to form a contracting section II;

in the ascending section (4-2), the gas velocity of the contraction section I is 18-20m/s, the gas velocity of the expansion section I is 14-16m/s, the distance between the middle parts of two adjacent cylinders I (4-2-1) is one pitch I L1, the diameter of the inner circular wall of the cylinder II (4-2-2) is d1, and the L1/d1 is 4-6;

in the descending section (4-1), the second contracting section gas velocity is 8-10m/s, the second expanding section gas velocity is 5-6m/s, the distance between the middle parts of two adjacent cylinders three (4-1-1) is two pitches L2, the diameter of the inner circular wall of cylinder four (4-1-2) is D1, and the L2/D1 is 4-6.

2. The reciprocating grate gasification coupled coal-fired power generation and biochar cogeneration device of claim 1, characterized in that: and the outlet of the biochar water-cooling auger I (11) is provided with a rotary sealing valve I (15), and the outlet of the biochar water-cooling auger II (12) is provided with a rotary sealing valve II (16).

3. The reciprocating grate gasification coupled coal-fired power generation and biochar cogeneration device of claim 1, characterized in that: the number of the air chambers is six, the six air chambers sequentially comprise an air chamber I (2-1), an air chamber II (2-2), an air chamber III (2-3), an air chamber IV (2-4), an air chamber V (2-5) and an air chamber VI (2-6) along the running direction of the reciprocating grate (2), and the air supply volumes of the six air chambers sequentially account for 15%, 20%, 15% and 10% of the total air volume.

4. A method for realizing the gasification of a reciprocating grate and the coupling of coal burning power generation for the co-production of biochar by utilizing the device of any one of claims 1 to 3, which is characterized in that: the method comprises the following steps:

the method comprises the following steps: biomass fuel is pushed into a gasification furnace chamber to be gasified through a movable grate segment (2-7) of the reciprocating grate (2), and biochar obtained after gasification is pushed into an open U-shaped water-cooling auger (5); in the process of gasifying the biomass fuel, at least six air chambers supply air to a gasification furnace chamber, the air supply amount accounts for 25-40% of theoretical air amount, and the temperature in the gasification furnace chamber is controlled to be between 700 and 800 ℃;

step two: the biomass with the particle size of less than 5mm and the moisture of less than 15 percent is sent into a combustible gas pipeline with the temperature of 700 plus materials at the top outlet of a gasification hearth through a rotary valve feeder (6), and enters a vertical type reducing and gradually expanding cracker (4) together with high-temperature combustible gas to carbonize the biomass, the retention time of the biomass is 8-10s, the feeding amount of the biomass is adjusted by adjusting the rotating speed of the rotary valve feeder (6), the temperature of the combustible gas is reduced from 800 plus materials to 450 ℃, and then the biomass enters a cyclone separator (7) to separate the biochar, and the temperature of the biochar enters a biochar water-cooling auger II (12) and is reduced to below 150 ℃ for recovery; combustible gas at the top of the cyclone separator (7) enters the large coal-fired boiler (10) under the action of the induced draft fan (8); the vertical type gradually-reducing and gradually-expanding cracker (4) is of a 'snake' -shaped structure, the vertical type gradually-reducing and gradually-expanding cracker (4) is formed by alternately arranging a descending section (4-1) and an ascending section (4-2) from an inlet to an outlet in sequence, and the descending section and the ascending section are connected and combined by a bent pipe (4-3);

the ascending section (4-2) is formed by coaxially and alternately arranging a plurality of cylinders I (4-2-1) and a plurality of cylinders II (4-2-2) in sequence, the lower end of each cylinder I (4-2-1) is connected with the upper end of each cylinder II (4-2-2) through a necking I, the lower end of each cylinder II (4-2-)2 is connected with the upper end of each cylinder I (4-2-1) through a flaring I, the flaring I at the lower end of each cylinder II (4-2-2) is combined with the cylinder I (4-2-1) to form a flaring section I, and the necking I at the lower end of each cylinder I (4-2-1) is combined with the cylinder II (4-2-2) to form a shrinking section I;

the descending section (4-1) is formed by coaxially and alternately arranging a plurality of cylinders three (4-1-1) and a plurality of cylinders four (4-1-2) in sequence, the lower end of each cylinder three (4-1-)1 is connected with the upper end of each cylinder four (4-1-2) through a necking II, the lower end of each cylinder four (4-1-2) is connected with the upper end of each cylinder three (4-1-1) through a flaring II, the flaring II at the lower end of each cylinder four (4-1-2) is combined with the cylinder three (4-1-1) to form a flaring section II, and the necking II at the lower end of each cylinder three (4-1-1) is combined with the cylinder four (4-1-2) to form a shrinking section II;

in the descending section (4-1), the second contracting section air velocity is 8-10m/s, the second expanding section air velocity is 5-6m/s, the distance between the middle parts of two adjacent cylinders three (4-1-)1 is two pitches L2, the diameter of the inner circular wall of cylinder four (4-1-2) is D1, and the L2/D1 is 4-6.

5. The method for the combined production of biochar by the gasification of the reciprocating grate and the power generation of the coal as claimed in claim 4, wherein: in the first step, the biomass fuel comprises straw bulk materials, straw briquettes and wood bars, and the adding amount of the biomass fuel is 5-40 t/h.

6. The method for the combined production of biochar by the gasification of the reciprocating grate and the power generation of the coal as claimed in claim 5, wherein: the moisture of the straw bulk material is less than 35 percent, and the longest straw bulk material is not more than 150 mm; the cross section size of the straw briquetting is as follows: the width is 32mm multiplied by 32mm, and the length is less than 100 mm; the moisture of the wood bar stock is less than 25%, and the section size is as follows: the width multiplied by the height is less than 40 multiplied by 40mm, and the length is less than 200 mm.

7. The method for the combined production of biochar by the gasification of the reciprocating grate and the power generation of the coal as claimed in claim 4, wherein: in the first step, the number of the air chambers is six, the six air chambers sequentially comprise an air chamber I (2-1), an air chamber II (2-2), an air chamber III (2-3), an air chamber IV (2-4), an air chamber V (2-5) and an air chamber VI (2-6) along the running direction of the reciprocating grate (2), and the air supply volumes of the six air chambers sequentially account for 15%, 20%, 15% and 10% of the total air volume.

8. The method for the combined production of biochar by the gasification of the reciprocating grate and the power generation of the coal as claimed in claim 4, wherein: in the second step, the biomass is rice hulls, sawdust and all other biomass with the particle size smaller than 5mm and the water content smaller than 15%.