CN103666570B - From drying type biomass gasification system - Google Patents

Abstract

The invention provides a self-drying biomass gasification system, which includes a self-drying fixed-bed biomass gasification furnace, the self-drying fixed-bed biomass gasification furnace includes a furnace body arranged vertically, the The furnace body includes a cone-shaped tailing ash section at the bottom and a reaction section above the tailing ash section. A grate is arranged between the tailing ash section and the reaction section; The side of the reaction section is provided with an air inlet; the upper side or top of the reaction section is provided with a fuel inlet; the self-drying fixed-bed biomass gasifier further includes a feeding device and a feeding pipe; the feeding pipe is inserted into the fuel inlet; The top of the feeding pipeline is closed, the side of the blanking pipeline is provided with a feed inlet, and the end of the feeding device is connected to the feeding inlet; the side or top of the blanking pipeline is also provided with a circulating gas outlet, and the circulating gas outlet is connected to the A gas return pipe, the side of the tail ash section is provided with a return inlet, and the other end of the gas return pipe is connected to the return inlet of the tail ash section.

Description

Self-drying biomass gasification system

technical field

The invention relates to a self-drying biomass gasification system.

Background technique

Biomass is a very important renewable energy, which has the characteristics of renewability, low pollution and wide distribution. The use of biomass as an alternative energy source is of great significance to low-carbon emission reduction, reduction of "greenhouse effect" and improvement of atmospheric acid rain environment. Biomass gasification system is to use biomass to burn in a closed anoxic furnace in a gasifier, and produce combustible gas after dry distillation, pyrolysis and thermochemical oxidation.

Biomass particles usually contain 40%-50% water or even higher, and the more suitable water content for biomass gasification is less than 20%. Thus, biomass pellets usually need to be dried before being gasified.

For example, Chinese patent application 95117448.7 discloses a biomass gasification drying and heating device, which is composed of a gasifier, a gas burner, a jet mixer, and a fan connection. The gas pipe of the gasifier is connected to the gas pipe of the gas burner. Connected, the fire path of the gas burner is connected with the nozzle pipe of the jet mixer, the hot air generated in the jet mixer is output through the mixing pipe, and the fan is respectively connected with the intake pipes of gasifier 1, burner 2 and mixer 3 .

Chinese patent application 201110123306.2 discloses a spiral biomass pyrolysis reactor with drying function. The outlet of the spiral feeder of the reactor is connected to the lower side of the vertical drying lifting cylinder; the bottom of the drying lifting cylinder is connected to the air outlet of the induced draft fan, and the top is connected to the spiral pyrolysis reaction through the cyclone separator. The feed port of the device; the other end of the spiral pyrolysis reactor is provided with a pyrolysis carbon outlet and a pyrolysis gas outlet; the input end of the spiral pyrolysis reactor is connected to a speed-regulating motor, and the middle part of the spiral pyrolysis reactor Located in the combustion heating chamber; the top middle of the combustion heating chamber is provided with a flue gas outlet, which is connected to the air inlet of the induced draft fan through a pipe.

Chinese patent 200910103426.9 discloses a biomass fuel mobile dryer related to agricultural machinery. An air-cooled biomass gasifier is placed on the carriage board of the mobile vehicle. The shell wall of the biomass gasifier is welded with an air inlet tube, and the symmetrical shell wall is welded with one end of the air outlet and the other end of the air outlet. Weld the shell wall of the air duct; one side wall of the air-cooled separator is welded with an air inlet with a mesh cover, the other side wall is welded with one end of the air outlet, and the other end of the air outlet is welded with the air inlet tube; the other side of the air duct is welded Weld one end of the hot air duct, the other end of the hot air duct is connected to the input port of the exhaust fan, and the output port of the exhaust fan is welded to the pipe wall of the small U-shaped groove in the lower part of the dryer.

Chinese patent 97216018.3 discloses a biomass heat conversion gasification and drying device. The grate in the burner adopts a grate with a hollow structure with openings at both ends and a supporting cooling device; the heat exchanger has a cyclone dust removal device.

All of the above technical solutions require a separate dedicated biomass drying device, resulting in high system costs and large space occupation.

Therefore, how to provide a biomass gasification system with a self-drying function has become a problem to be solved in the industry.

Contents of the invention

In view of the shortcomings of the prior art, the object of the present invention is to provide a self-drying biomass gasification system, which has the function of self-drying.

In order to achieve the above object, the present invention provides a self-drying biomass gasification system, which includes a self-drying fixed-bed biomass gasifier, and the self-drying fixed-bed biomass gasifier includes a vertically arranged The furnace body includes a cone-shaped bucket-shaped tailing ash section at the bottom and a reaction section above the tailing ash section. There is a grate between the tailing ash section and the reaction section; the bottom of the tailing ash section is equipped with a slag discharge The side of the tail ash section is provided with an air inlet; the upper side or top of the reaction section is provided with a fuel inlet;

Wherein, the self-drying fixed-bed biomass gasifier further includes a feeding device and a blanking pipeline; the blanking pipeline is inserted into the fuel inlet; the top of the blanking pipeline is closed, and the side of the blanking pipeline is provided with a feeding port, The end of the feeding device is connected to the feeding port; the side or top of the blanking pipe is also provided with a circulating gas outlet, and the circulating gas outlet is connected to a gas return pipe, and the side of the tail ash section is provided with a return inlet, and the gas returns The other end of the pipe is connected to the return inlet of the tail ash section.

In the present invention, in order to achieve a better drying effect, the side feed port of the blanking pipe can be set lower than the outlet of the circulating gas, so that the biomass particles fed from the feed port can be evenly distributed during the whole process of falling. Access to rising gases in the furnace.

In the present invention, the feeding device can be various suitable feeding devices, for example, it can be a screw conveyor for continuous feeding, or a drum valve (flap valve) for intermittent feeding.

In the present invention, an induced draft fan can be arranged on the gas return pipeline to ensure the directional flow of the gas in the pipeline.

In the present invention, by setting a circulating gas outlet on the side or top of the blanking pipe, the gas in the blanking pipe can flow out, and then part of the hot gas in the furnace enters through the opening at the lower end of the blanking pipe to form a gas outlet in the furnace. Part of the hot air circulates from bottom to top through the blanking pipeline to dry the biomass particles in the blanking pipeline. The moist hot gas that flows out through the circulating gas outlet passes through the gas return pipe and the return inlet, and returns to the high temperature area at the bottom of the furnace to participate in gasification. Therefore, this solution realizes the self-drying function by setting the circulating gas outlet, the gas return pipe and the return inlet; it does not need to use additional drying devices and drying means, which not only realizes the full utilization of resources, but also avoids It pollutes the environment, and at the same time makes the gasifier highly adaptable to the moisture of biomass raw materials, which breaks through the strict requirements of conventional gasifiers on moisture.

According to another specific embodiment of the present invention, the feeding device is a multi-stage feeding device, and the multi-stage feeding device at least includes a first-stage feeding device and a final-stage feeding device, and each stage of feeding device includes a The feed port at the top and the discharge port at the end; the first-stage feed device and the final-stage feed device are arranged up and down; the discharge port of the first-stage feed device is directly connected to the feed port of the final-stage feed device communicated, or communicated through indirect connection between one or more stages of intermediate feed devices located between the first-stage feed device and the final-stage feed device and the feed port of the final-stage feed device; the first-stage feed device and each The end of the intermediate feeding device is provided with a closed intermediate material box, and the outlet of the primary feeding device and each intermediate material conveying device is connected to the inlet of the next-level feeding device through the intermediate material box. Connected; the discharge port of the final feed device is connected to the feed port of the biomass gasification furnace.

The feed port of the first-stage feed device is the total feed port of the entire multi-stage feed device, and the discharge port of the last-stage feed device is the total feed port of the entire multi-stage feed device. Because the biomass material is light and small in size, it is easy to scatter and float, causing dust pollution. In the present invention, the closed intermediate material box can effectively prevent the diffusion of the biomass material when it enters the feed device of the next stage from the feed device of the upper stage. The multi-stage feeding device in front of the furnace is used to transport the biomass material in the silo to the biomass gasifier. The biomass material in the silo is input into the feed port of the primary feed device. A closed intermediate material box can also be set between the material opening of the silo and the material inlet of the primary feeding device to prevent material from spreading.

By setting up a multi-stage feeding device, and the feeding devices of each level are connected through a closed intermediate material box, when the biomass material is transported in the feeding device, it can effectively prevent the gas in the biomass gasifier from flowing along The material device reverses into the silo, thereby preventing accidents such as overhead bulging of the silo, poor feeding, personnel poisoning, and silo explosion caused by equipment anti-smoke.

According to another specific embodiment of the present invention, the reaction section includes at least two cylindrical gas production sections, the at least two gas production sections are vertically arranged and connected end to end, and a furnace is arranged between the tail ash section and the gas production section at the bottom. The side of each gas production section is provided with a gas outlet; each gas outlet is connected to a gas sub-pipeline, and multiple gas sub-pipelines are connected to a gas main pipeline. The shape of the reaction section can be cylindrical or square, and it is preferably cylindrical; the size of each gas-producing section, such as height, diameter, and width, can be the same or different. The number of gas producing sections is preferably 2-4. The gas outlet of each gas production section is preferably arranged at the upper end of its side. The gas sub-pipelines connected to the gas outlet of each gas production section and the merged gas main pipeline are internally or externally insulated to avoid heat loss and facilitate the use of downstream gas users. The air inlet on the side of the tail ash section can be connected to the air inlet pipe, and the air is supplied by the blower.

The content of gas produced by each gas production section is different. The gas produced by the higher furnace body has high tar content, high calorific value and low temperature, while the gas produced by the lower furnace body has a higher temperature and lower calorific value. By outputting and mixing the gas produced by multi-stage furnaces with different heights, the different physical and chemical characteristics of the gas produced by each gas production section can be integrated, and a more ideal biomass gas can be adjusted to make the temperature and calorific value of the gas uniform. Due to the adoption of multi-stage gas production process, the gasification efficiency is high. In addition, it can also increase the volumetric gas production rate (or cross-sectional gas production rate) of the biomass gasifier and reduce the investment in gasifier equipment. At the same time, the self-drying fixed-bed biomass gasifier has a compact structure, a high volumetric gasification rate, and convenient production and maintenance.

According to another specific embodiment of the present invention, each gas sub-pipeline is provided with a flow-adjustable valve. The gas output ratio of each stage can be adjusted by adjusting the valve, so that the calorific value of the produced biomass gas is stable, and the physical characteristics such as temperature can be adjusted within a certain range, which is convenient for adjustment for later application equipment.

According to another specific embodiment of the present invention, it further includes a dust removal device, the gas main pipeline leads into the dust removal device, the dust removal device includes an ash outlet and a gas outlet, the gas outlet is connected to a gas pipeline, and an induced draft fan can be arranged on the gas pipeline to Ensure the directional flow of gas in the pipeline. By setting up a dedusting device, the obtained gas is dedusted to avoid polluting the environment and blocking the downstream pipeline with dust. According to another specific embodiment of the present invention, the dedusting device is a single-tube cyclone dedusting device, or a multi-tube cyclone dedusting device, or a ceramic tube filter dedusting device, or a moving bed filter dedusting device.

According to another specific embodiment of the present invention, each gas production section is provided with a plurality of gas outlets, and the plurality of gas outlets are located at the same height. The number of gas outlets of each furnace body can be consistent or inconsistent. The number of gas outlets in each furnace body is preferably 1-5. Preferably, multiple gas outlets of each section of the furnace body are evenly distributed at a certain angle at the same height.

Generally speaking, there is no need to set a gas collecting pipe in the furnace body, and the gas outlet of each furnace body is the furnace wall exhaust port. As required, according to another specific embodiment of the present invention, each gas production section is provided with a gas collecting pipe, the gas collecting pipe includes a longitudinally arranged main pipe and a plurality of branch pipes connected to the main pipe, and the plurality of branch pipes are respectively inserted into a plurality of Gas outlet.

According to another specific embodiment of the present invention, the grate is a water-cooled grate, and the water-cooled grate includes a plurality of grate rods arranged in parallel, and each grate rod is a tube with a cavity made of a heat-conducting material (such as metal tubes or ceramic tubes), the water-cooled grate includes a drive motor for driving the grate rod in rotation. By rotating the grate rod of the fire grate, the ash accumulated on the fire grate can be promoted to fall from the gap of the fire grate, thereby achieving a better slag discharge effect.

According to another specific embodiment of the present invention, each grate rod is equipped with a blade that can be rotated by the grate rod as a rotating shaft, and the blades are all located in the furnace body of the gasifier. By driving the motor to drive the rotation of the grate rod, and then driving the blades on the grate rod to rotate, a better slag discharge effect can be achieved, and the continuous and active slag removal of the grate can be effectively carried out to prevent the accumulation of ash on the grate. Specifically, the blade can be helical, polygonal, or blade-shaped.

The ash and slag discharged from the slag outlet and the ash outlet can be conveyed by various means in the prior art, for example, it can be conveyed outward through a water-cooled auger, so as to cool the ash and slag while conveying. According to another specific embodiment of the present invention, the system of the present invention further includes a wet slag discharge device, which includes an ash discharge pipe connected to the slag outlet and the ash outlet, a screw conveyor, a water tank, and the ash discharge pipe. The bottom end leads into the screw conveyor; the screw conveyor is arranged obliquely, and its end leads into the water tank downwards. The tail ash in the gasifier and the ash collected by the dust removal device are transported to the water tank through the ash falling pipe and the screw conveyor, so as to avoid the fly ash from polluting the environment.

According to another specific embodiment of the present invention, it further includes a release device, the release device is connected to the gas pipeline through a pipeline, and includes a valve.

According to another specific embodiment of the present invention, a flue gas return inlet is provided on the side of the gasifier body, the flue gas return inlet is connected to the flue gas return pipe, and the other end of the flue gas return pipe is connected to the downstream gas unit. Flue gas output pipe. By refluxing the CO ₂ of the gas unit, the reaction of CO ₂ and Cp to generate CO is increased. At the same time, the flue gas reflux will bring back the waste heat of the heat unit, so that the carbon conversion rate and the overall thermal efficiency can be improved. At the same time, _CO2 can oxidize tar at high temperature, turning it into gaseous hydrocarbons or CO, reducing the tar content. By improving the carbon conversion efficiency and utilizing the waste heat of the hot kiln flue gas, the efficiency of the whole system is greatly improved.

Since CO ₂ is no longer scarce in the gasifier, the charcoal ash discharged from the furnace can be sent into the furnace again to participate in the reaction. Specifically, the end of the tail ash conveying device of the gasifier and the dust removal device can lead to the silo, and then enter the gasifier through the feeding device for reaction, thereby realizing the carbon ash circulation.

Compared with the prior art, the present invention has the following beneficial effects:

In the present invention, by setting a circulating gas outlet on the side of the blanking pipe, the gas located in the blanking pipe can flow out, and then the hot gas in the furnace enters through the opening at the lower end of the blanking pipe, forming the hot gas in the furnace through the falling The flow from bottom to top in the feeding pipe is used to dry the biomass particles in the feeding pipe. The moist hot gas that flows out through the circulating gas outlet passes through the gas return pipe and the return inlet, and returns to the high temperature area at the bottom of the furnace to participate in gasification. Therefore, this solution realizes the self-drying function by setting the circulating gas outlet, the gas return pipe and the return inlet; it does not need to use additional drying devices and drying means, which not only realizes the full utilization of resources, but also avoids It pollutes the environment, and at the same time makes the gasifier highly adaptable to the moisture of biomass raw materials, which breaks through the strict requirements of conventional gasifiers on moisture.

The present invention will be further described in detail below in conjunction with the accompanying drawings.

Description of drawings

Fig. 1 is the structural representation of the self-drying type biomass gasification system of embodiment 1;

Fig. 2 is the structural representation of self-drying type fixed-bed biomass gasifier in embodiment 1;

Fig. 3 is the structural representation of the two-stage feeding device in embodiment 3;

Fig. 4 is a schematic structural view of the fire grate in Embodiment 4.

detailed description

Example 1

As shown in Figures 1-2, the self-drying biomass gasification system of this embodiment includes a self-drying fixed-bed biomass gasification furnace 1, a dust removal device (such as a single-cylinder cyclone dust removal device 2), a diffuser Device 3, wet slag discharge device 4.

Wherein, the self-drying fixed-bed biomass gasification furnace 1 includes a feeding device 111 (such as a screw conveyor), a blanking pipeline 11, and a furnace body. The furnace body is built with refractory and thermal insulation materials, including a reaction section and a tail ash section 14 , and the reaction section further includes a first gas production section 12 and a second gas production section 13 . The top of the first gas production section 12 is provided with a fuel inlet.

The tail ash section 14 is cone-shaped and located at the bottom of the furnace body. The bottom of the tail ash section 14 is provided with a slag outlet 142 , and the side of the tail ash section 14 is provided with an air inlet 145 and a return inlet 141 .

The feeding pipe 11 is inserted into the fuel inlet at the top of the first gas producing section 12 . The top of the blanking pipeline 11 is blocked, and the side of the blanking pipeline 11 is provided with a feed inlet, and the end of the feeding device 111 is connected to the feed inlet; the side of the blanking pipeline 11 is also provided with a circulating gas outlet, and the circulation The gas outlet is connected to a gas return pipe 112 , the gas return pipe 112 is provided with an induced draft fan 113 , and the other end of the gas return pipe 112 is connected to the return inlet 141 of the tail ash section 14 .

The first gas production section 12 and the second gas production section 13 are both cylindrical, located above the tail ash section 14, arranged vertically and connected end to end. A fire grate 15 is provided between the tail ash section 14 and the second gas production section 13 . The upper side of the first gas production section 12 is provided with three gas outlets 121 (furnace wall exhaust ports). The three gas outlets 121 are located at the same height, and the angle between adjacent gas outlets is 120°. The outlets 121 are all connected to a gas branch pipeline 122 . The side upper end of the second gas production section 13 is provided with four gas outlets 131 (furnace wall exhaust ports), the four gas outlets 131 are located at the same height, and the angle between adjacent gas outlets is 90°, each The gas outlets 131 are all connected to a gas branch pipe 132 . A flow-adjustable valve is arranged on each gas sub-pipeline. A plurality of gas sub-pipelines are connected to a gas main pipeline 5 .

The gas main pipeline 5 leads into the dust removal device 2, and the dust removal device 2 includes an ash outlet 22 and a gas outlet 21, and the gas outlet 21 is connected to a gas pipeline 6, and the gas pipeline 6 is provided with an induced draft fan 61.

The wet slag discharge device 4 includes the ash discharge pipe 411 connected to the slag outlet 142 of the tail ash section 14, the ash discharge pipe 421 connected to the ash outlet 22 of the dust removal device 2, a screw conveyor 412, a screw conveyor 422, sink43. The bottom end of the ash-falling pipe 411 leads into the screw conveyor 412; the bottom end of the ash-falling pipe 421 leads into the screw conveyor 422; In the sink 43.

The diffuser 3 is connected to the gas pipeline 6 through a pipeline, which has a valve.

Example 2

The differences between this embodiment and Embodiment 1 are: (1) It also includes a third gas production section, which is located between the first gas production section and the second gas production section; (2) the first gas production section The gas production section, the second gas production section and the third gas production section are all in the shape of a square tube; (3) There are four gas outlets in each gas production section, and in each gas production section, the gas outlets are at the same height Evenly arranged, the angle between adjacent gas outlets is 90°; (4) There is a gas collecting pipe in each gas production section, and the gas collecting pipe includes a vertically arranged main pipe and four branch pipes connected to the main pipe, four The branch pipes are respectively inserted into the four gas outlets correspondingly.

Example 3

As shown in Figure 3, the difference between this embodiment and Embodiment 1 is that the feed device is a two-stage feed device 7, which includes a first-stage feed device 701, an intermediate feed box 702, and a final-stage feed device 703. . The primary feeding device 701 is a speed-adjustable cantilever screw conveying device. It includes an inlet at the upper front and an outlet at the end. The feeding port of the silo is connected to the feeding port above the front part of the primary feeding device 701 . The discharge opening at the end of the primary feeding device 701 is an upward slant, and a gland 704 is provided on the slant. The angle formed by the plane where the bevel is located and the axis of the cantilever screw conveying device is 45°. The gland 704 has an automatic reset mechanism (such as a spring 705). In addition, a section of blades before the outlet of the primary feeding device 701 is removed. The outlet of the primary feeding device 701 is inclined upward by 10° relative to the horizontal plane. A closed intermediate material box 702 is arranged at the end of the primary feeding device 701 . Two material level gauges are arranged in the middle material box 702 , one of which is a low level material level gauge 706 and the other is a high level material level gauge 707 . The final feeding device 703 is a cantilever screw conveying device, which includes a feed inlet located above the front and a discharge outlet located at the end. Its discharge port is inclined 15° upwards relative to the horizontal plane, and its discharge port is connected to the material inlet of the biomass gasification furnace 1 . The first-stage feeding device 201 and the final-stage feeding device 203 are arranged up and down; the outlet of the first-stage feeding device 201 is directly connected to the inlet of the last-stage feeding device 203 through the intermediate material box 202 .

Example 4

As shown in FIG. 4 , the difference between this embodiment and Embodiment 1 is that the grate is a water-cooled grate 8 , which includes an adjustable-speed drive motor 801 and a plurality of grate rods 802 arranged in parallel. The driving motor 801 is used to drive each grate bar 802 to rotate. Each grate rod 802 is a metal tube with a cavity, and the two ends of each grate rod 802 are located outside the furnace body 1 of the gasifier, and the two ends of each grate rod 802 are equipped with water cooling Rotary joint. Each grate bar 802 is equipped with a helical blade 803, which can be rotated by the grate bar as a rotation axis, and the helical blades 803 are all located in the furnace body of the gasifier.

Although the present invention is disclosed above with preferred embodiments, it is not intended to limit the scope of the present invention. Any person skilled in the art may make some improvements without departing from the scope of the present invention, that is, all equivalent improvements made according to the present invention shall be covered by the scope of the present invention.

Claims (10)

1. A self-drying type biomass gasification system, which comprises a self-drying type fixed-bed biomass gasification furnace, said self-drying type fixed-bed biomass gasification furnace comprises a furnace body arranged vertically, said The furnace body includes a cone-shaped bucket-shaped tailing ash section at the bottom and a reaction section above the tailing ash section. A fire grate is arranged between the tailing ash section and the reaction section; the bottom of the tailing ash section is arranged There is a slag outlet, and the side of the tail ash section is provided with an air inlet; the upper side or top of the reaction section is provided with a fuel inlet; Wherein, the self-drying fixed-bed biomass gasifier further includes a feeding device and a blanking pipeline; the blanking pipeline is inserted into the fuel inlet; the top of the blanking pipeline is closed, and the side of the blanking pipeline There is a feeding port at the top, and the end of the feeding device is connected to the feeding port; the side or top of the blanking pipeline is also provided with a circulating gas outlet, and the circulating gas outlet is connected to a gas return pipeline. A backflow inlet is provided on the side of the tailing ash section, and the other end of the gas return pipe is connected to the backflow inlet of the tailing ash section; the side feed port of the blanking pipe is set lower than the circulating gas outlet. 2. The self-drying biomass gasification system as claimed in claim 1, wherein the feed device is a multi-stage feed device, and the multi-stage feed device includes at least a first-stage feed device, a final stage Feeding device, each level of feeding device includes a feed inlet located above the front part and a discharge outlet located at the end; The first-stage feeding device and the final-stage feeding device are arranged up and down; the discharge port of the first-stage feeding device is directly connected to the feed port of the last-stage feeding device, or through One or more stages of intermediate feed devices between the stage feed device and the final stage feed device are indirectly connected to the feed port of the final stage feed device; The end of the primary feeding device and each of the intermediate feeding devices is provided with a closed intermediate material box, and the discharge port of the primary feeding device and each of the intermediate material conveying devices passes through the middle The material box is connected to the feed port of the next-level feed device; The discharge port of the final feed device is connected to the feed port of the biomass gasification furnace. 3. The self-drying biomass gasification system according to claim 1, wherein the reaction section comprises at least two cylindrical gas production sections, the at least two gas production sections are vertically arranged and connected end to end, A fire grate is provided between the tail ash section and the gas production section at the bottom; a gas outlet is provided on the side of each gas production section; each gas outlet is connected to a gas sub-pipeline, and a plurality of The gas sub-pipelines are connected to a gas main pipeline. 4. The self-drying biomass gasification system according to claim 3, wherein each of the gas sub-pipelines is provided with an adjustable flow valve. 5. The self-drying biomass gasification system according to claim 3, wherein each of the gas production sections is provided with a plurality of gas outlets, and the plurality of gas outlets are located at the same height. 6. The self-drying biomass gasification system as claimed in claim 5, wherein, a gas collecting pipe is arranged in each of the gas production sections, and the gas collecting pipe includes a vertically arranged main pipe and a main pipe connected to the main pipe. A plurality of branch pipes, the plurality of branch pipes are correspondingly inserted into a plurality of gas outlets. 7. The self-drying biomass gasification system as claimed in claim 1, wherein the grate is a water-cooled grate, and the water-cooled grate comprises a plurality of grate bars arranged in parallel, each of which The grate rods are tubes with a cavity made of heat-conducting material, and the water-cooled grate includes a drive motor for driving the grate rod to rotate. 8. The self-drying biomass gasification system as claimed in claim 7, wherein, each of the grate bars is equipped with blades that can be used as a rotating shaft to rotate the grate bars, and the blades are located at the The furnace body of the gasification furnace. 9. The self-drying biomass gasification system as claimed in claim 1, further comprising a wet slagging device, the wet slagging device comprising an ash falling pipe connected to the slag outlet, a screw conveyor, A water tank, the bottom end of the ash falling pipe leads into the screw conveyor; the screw conveyor is arranged obliquely, and its end leads downward into the water tank. 10. The self-drying biomass gasification system according to claim 1, the side of the gasification furnace body is provided with a flue gas return inlet, and the flue gas return inlet is connected to a flue gas return pipe, and the flue gas The other end of the return pipe is connected to the flue gas output pipe of the downstream gas unit.