CN1279145C - Device for preparing coal gas by using fluffy biomass raw material - Google Patents

Abstract

The invention discloses a process and a device for preparing gas by using fluffy biomass raw materials. The process includes the steps of raw material pretreatment, raw material gasification, separation and slag removal, gas purification, and gas transportation; the device includes a raw material pretreatment system, a gas generation system, a gas purification system, and a gas transportation and storage system. The built-in fast fluidized bed gasification furnace adopted in the invention has the characteristics of high production intensity, high gasification efficiency, low gas tar content, good operation stability and the like. The gasification reaction is completed at the speed of pneumatic conveying. The built-in separator realizes the rapid circulation of biomass raw materials in the gasifier. The gas purification adopts the method of combining water washing and organic solvent washing, which has a high tar removal rate and a low tar content in the gas. Small fluctuations and other characteristics. The process and equipment of the present invention can continuously gasify fluffy biomass raw materials, and the gas produced by the gasification can be used as a gas source for a gas generator, and can also be used to supply gas to surrounding residential users through a pipeline network.

Description

A device for preparing gas from fluffy biomass raw materials

technical field

The invention relates to a process and equipment for preparing gas from biomass raw materials, in particular to a process for preparing gas from fluffy biomass raw materials, and also relates to a device for the process.

Background technique

Biomass in a broad sense refers to hydrocarbons produced by photosynthesis. According to the texture of biomass raw materials, biomass raw materials can be divided into two types: dense type and fluffy type: dense type biomass raw materials mainly include forest logging residues, sorghum, corn, cotton and other crop straws, and fluffy type biomass raw materials It mainly includes agricultural straw such as rice straw, wheat straw, and rice husk. my country is a large agricultural country, and the crops are mainly wheat and rice, so the fluffy biomass raw materials account for a considerable proportion of my country's biomass resources.

How to efficiently and rationally develop and utilize fluffy biomass resources (straw, wheat straw, rice husk, sawdust, etc.) is a major issue we are facing. Domestic biomass gasification generally adopts a downdraft gasifier, which is more effective for the gasification of dense biomass raw materials, but not ideal for fluffy biomass raw materials. For powdery materials such as sawdust and wood powder, there are reports of using an external circulating fluidized bed gasifier, but there are defects such as complex furnace structure and poor stability. Gas purification generally adopts wet process, and the purification process produces a large amount of tar-containing sewage, causing secondary pollution to the environment.

Contents of the invention

The purpose of the present invention is to provide a process for preparing coal gas by continuously gasifying fluffy biomass raw materials with high efficiency, low cost and less pollution.

Another object of the present invention is to provide a dedicated device for the above process.

The object of the present invention is achieved by the following measures:

A process for preparing coal gas by utilizing fluffy biomass raw materials, comprising the following steps:

(1) Pretreatment of raw materials: fluffy biomass raw materials are crushed or chopped into 3-10mm pieces;

(2) Gasification of raw materials: The pretreated biomass raw material fragments are sent to the gasification furnace, and the biomass raw materials undergo partial oxidation-reduction reactions with the gasification medium in the gasification furnace to generate coal gas. The gasification reaction is at 600 ° C ~ It is carried out within the temperature range of 1000 ° C, and the tar is fully cracked. The temperature control is realized by adjusting the amount of gasification medium and the amount of raw materials added;

(3) Separation and slag removal: the high-temperature coal gas containing ash and a small amount of tar drawn from the gasifier enters the separation device. The gas after slag enters the purification system;

(4) Gas purification: the separated gas is cooled by water washing, and the ash and part of the tar in the gas can be removed at the same time; a small amount of tar remaining in the gas after water washing and purification is removed by organic solvent washing; the solvent used in the purification system recycled after recycling;

(5) Gas transmission and distribution: The gas output from the purification system is sent to the gas cabinet for storage or as a gas source for gas generators, and can also be used to supply gas to surrounding residents through the pipeline network.

The process for preparing coal gas by using fluffy biomass raw materials, wherein the gasification medium is air, and the volume-to-weight ratio of the amount of gasification air in ^Nm3 to the amount of raw material added in kg is controlled at 1.05 to 1.15: 1. The fluidization gas velocity is 1.4-2.5m/s.

In the process for preparing gas from fluffy biomass raw materials, the organic solvent used for gas purification can be heavy oil or heavy fuel oil, and the solvent circulation is 3-5 m ³ /h.

A device for preparing gas by using fluffy biomass raw materials, including a raw material pretreatment system, a gas generation system, a gas purification system, and a gas delivery and storage system.

The device for preparing gas by using fluffy biomass raw materials, wherein the gas generation system adopts a built-in fast fluidized bed gasifier.

The device for preparing gas by using fluffy biomass raw materials, wherein the built-in fast fluidized bed gasifier is equipped with a built-in separator, and the material leg of the built-in separator adopts a Wing valve sealing structure, the sealing structure only allows solid materials to flow down and does not allow gas to enter. The movable wings of the wing valve can be automatically opened and closed according to the accumulation of material in the material leg.

The device for preparing gas by using fluffy biomass raw materials, wherein the built-in separator is connected with a gas outlet pipe of sufficient length in the gasifier, and the gas outlet pipe is led out of the gasifier after passing through the high temperature zone of the gasifier.

In the device for preparing gas by using fluffy biomass raw materials, the gas purification system is composed of a water washing device and an organic solvent washing device.

In the device for preparing gas by using fluffy biomass raw materials, the water washing device is composed of a bubble tower and one or several washing towers.

In the device for preparing gas by using fluffy biomass raw materials, the organic solvent washing device is composed of a venturi tube.

The key process steps of the present invention are the gasification of biomass raw materials and the purification of coal gas, and the key equipment of the gasification is a built-in fast fluidized bed gasifier.

Advantages of the present invention:

(1) The built-in fast fluidized bed gasification furnace adopted in the present invention has a simple structure, low overall cost of the furnace body, convenient construction, and long service life of the furnace body; the gas purification in the process adopts a closed cycle multi-stage purification process, and the gas after washing The trace amount of tar in the gas is removed by the solvent method, and the solvent is recycled after being recycled, so the purification efficiency is high and the production cost is low.

(2) The built-in separator realizes the rapid circulation of fluffy biomass raw materials in the gasifier, and the biomass gasification reaction is completed at a high gas velocity of 1.4-2.5m/s (greater than the sedimentation velocity of raw material particles). Internal heat transfer and mass transfer speed are fast, the production intensity per unit gasification space is high, and the operation stability of the gasification furnace is good; the material leg of the built-in separator adopts a single-wing or multi-wing valve sealing structure, and the sealing structure only allows solid materials Downflow does not allow gas to enter, and the valve wing can automatically open and close according to the material accumulation in the material leg to ensure the separation effect of the built-in separator; the ungasified solid material collected by the built-in separator is returned to gasification by the material leg The lower part of the furnace continues to participate in the reaction, reducing the amount of fly carbon in the gasifier, and the carbon conversion rate of the biomass raw material is greater than 95%, which improves the utilization rate of the biomass. The production intensity of the built-in fast fluidized bed gasifier adopted in the present invention is 5-10 times that of the ordinary fluidized bed gasifier, the carbon content in the ash is less than 20%, the raw material carbon conversion rate is greater than 95%, and the generated gas heat The value is greater than 5800 kJ/Nm ³ .

(3) Because the temperature is too high, it is easy to slagging, and the temperature is too low, it is not easy to react effectively, and the quality of the prepared gas is poor. On the one hand, the present invention controls the gasification reaction temperature by adjusting the gasification air amount and the feed rate of raw materials. On the other hand, The main body of the gasification furnace adopts a structure combining metal materials and non-metal materials, that is, the upper part is made of steel structure, and the lower part is constructed of non-metallic refractory materials, so that the gasification furnace has a wide gasification area, and the gasification reaction temperature is uniform. The heat and mass transfer speed is fast, which can effectively prevent the slagging problem caused by local overheating.

(4) The coal gas produced by the gasifier is led out of the gasifier through a certain length of outlet pipe through the high temperature zone of the gasifier. The gas has enough residence time in the outlet pipe to fully crack the tar in the gas, and the outlet of the gasifier The tar content in the gas is low, and the main combustible components in the gas are: CO, H ₂ , CH ₄ , C _m H _n , etc. Gas purification adopts the method of combining water washing and organic solvent washing, and is carried out through a four-stage purification process of bubble tower-first washing tower-second washing tower-organic solvent scrubber (venturi tube); the solvent method to remove trace tar has the advantages of It has the characteristics of low operating cost and high tar removal rate. The tar content in the purified gas is less than 30mg/Nm ³ , which can fully meet the requirements of gas generators or pipeline transportation.

(5) The coal gas produced by the gasification of the present invention can be used as the gas source of the gas-fired generator, and can also supply gas to surrounding residential users through the pipeline network, which is an effective way to solve the problem of a large amount of fluffy biomass raw materials in rural areas. The popularization and application of technology has huge social and economic benefits for promoting the rational use of rural renewable biomass resources, protecting the environment, improving rural energy supply, and improving the quality of life of farmers.

Description of drawings

Fig. 1 is a process flow diagram of the present invention.

Fig. 2 is a structural schematic diagram of a built-in fast fluidized bed gasifier with a vertical downdraft gas outlet pipe used in the present invention.

Fig. 3 is a schematic diagram of the sealing structure of the double-wing valve adopted in the present invention.

Fig. 4 is a structural schematic diagram of a built-in fast fluidized bed gasifier with a spiral downdraft gas outlet pipe used in the present invention.

Fig. 5 is a schematic diagram of the sealing structure of the monowing valve adopted in the present invention.

Detailed ways

The specific embodiment of the present invention is further described in conjunction with accompanying drawing:

Example 1

In conjunction with accompanying drawings 1, 2, and 3, the process of the present invention is: crush the fluffy biomass raw material into 8-10mm fragments with a crushing device, add them to the hopper 2 by the lifting screw 1, and then send them into the built-in pellets by the screw feeder 3. The lower part of the type fast fluidized bed gasification furnace 4; air is sent into the furnace from the air inlet 27, and the gasification reaction temperature is controlled at 800°C to 900°C by adjusting the amount of gasification air and the feeding speed of raw materials, and the gasification air is controlled The ratio of the amount (Nm3) to the amount of raw material added (kg) is 1.15. The fluidization gas velocity in the gasifier is 2.5m/s, and the biomass raw material is boiling in the gasifier and undergoes partial redox reaction with the gasification medium (air) to generate coal gas. The coal gas entrained with solid materials and ash enters the built-in cyclone separator 20, and the solid materials captured by the cyclone separator 20 are returned to the lower part of the gasifier by the double-wing valve sealing structure 22 of the material leg 21 to continue to react (the double-wing valve sealing structure 22 is formed by The fins 26 are connected to the lower end of the material leg 21 through a hinge 24. There is also a conical device 25 inside the lower end of the material leg 21. The separated ash and solid materials fall into the material leg 21. When the solid material in the material leg accumulates to a certain height, When the pressure produced by the material on the flap is greater than the restoring force of the flap itself, the flap automatically opens, and the material flows out. When there is less material in the material leg, the flap 26 returns to the sealed state under its own weight). The coal gas produced by the gasifier containing some impurities such as ash and slag is drawn out through the gas outlet pipe 23 (the gas outlet pipe 23 adopts a vertical downward introduction type, and is drawn out from the built-in cyclone separator 20 after passing through the high temperature zone of the gasifier 4, and the gas outlet The pipe 23 keeps a certain length in the gasifier so that the tar is fully cracked under high temperature), and is sent to the external cyclone separator 5, and the separated ash enters the ash box 6, and the ash in the ash box is wetted Afterwards, it is continuously discharged by the spiral slagging machine 7, and the high-temperature gas from the cyclone separator 5 first enters the bubble tower 8, uses the water in the bubble tower to remove part of the ash and tar in the gas, and then enters the first washing tower 9, the second The second washing tower 10 continues to wash and cool down, remove tar and dust, and finally enters the organic solvent scrubber (venturi tube) 12 to further remove trace tar in the gas through heavy oil. The heavy oil enters the storage tank 13 after separation, and the recovered heavy oil is sent to the washing system for recycling by the pump 11. The solvent circulation volume is 5m ³ /h, and the tar content in the purified gas is less than 30mg/Nm ³ . The purified gas is sent into the gas cabinet 16 by the Roots blower 14 through the water seal 15, and the gas in the gas cabinet can be used as the gas source for the gas generator 17, and can also be supplied to residential users 18 through the pipeline network.

Example 2

In conjunction with accompanying drawings 1, 4, and 5, the process of the present invention is: crush the fluffy biomass raw material into 3-5mm fragments with a crushing device, add them to the hopper 2 by the lifting screw 1, and then send them into the built-in material by the screw feeder 3. The lower part of the type fast fluidized bed gasification furnace 4; air is sent into the furnace from the air inlet 27, and the gasification reaction temperature is controlled at 700°C to 800°C by adjusting the amount of gasification air and the feeding speed of raw materials, and the gasification air is controlled The ratio of the amount (Nm3) to the amount of raw material added (kg) is 1.05. The fluidization gas velocity in the gasifier is 1.4m/s, and the biomass raw material is boiling in the gasifier and undergoes partial redox reaction with the gasification medium (air) to generate coal gas. The gas entrained with solid materials and ash enters the built-in cyclone separator 20, and the solid materials captured by the cyclone separator 20 are returned to the lower part of the gasifier by the single-wing valve sealing structure 22 of the material leg 21 to continue to react (single-wing valve sealing structure 22 is connected to the lower end of the material leg 21 by the wing 26 through the hinge 24. There is also a conical device 25 inside the lower end of the material leg 21. The separated ash and solid materials fall into the material leg 21. When the solid material in the material leg accumulates to a certain When the pressure generated by the material on the flap 26 is greater than the restoring force of the flap itself, the flap will automatically open, and the material will flow out from it. When there is less material in the material leg, the flap 26 will return to the sealed state under its own weight ). The coal gas produced by the gasification furnace containing some impurities such as ash and slag is drawn out through the gas outlet pipe 23 (the gas outlet pipe 23 adopts a spiral downward introduction type, and is drawn out from the built-in cyclone separator 20 after passing through the high temperature of the gasifier 4, and the gas outlet pipe 23 keep a certain length in the gasifier, so that the tar is fully cracked under the action of high temperature), send it to the external cyclone separator 5, and the separated ash enters the ash box 6, and the ash in the ash box is wetted It is discharged continuously by the screw slagging machine 7, and the high-temperature gas from the cyclone separator 5 first enters the bubble tower 8, uses the water in the bubble tower to remove part of the ash and tar in the gas, and then enters the first washing tower 9, the second The washing tower 10 continues to wash and cool down, remove tar and dust, and finally enter the organic solvent scrubber (venturi) 12 to further remove trace tar in the gas through 180# heavy fuel oil. The heavy fuel oil enters the storage tank 13 after separation, and the recovered heavy fuel oil is sent to the washing system for recycling by the pump 11. The solvent circulation volume is 3m ³ /h, and the tar content in the purified gas is less than 27mg/Nm ³ . The purified gas is sent into the gas cabinet 16 by the Roots blower 14 through the water seal 15, and the gas in the gas cabinet can be used as a gas generator 17, and can also be supplied to residential users 18 through the pipeline network.

Claims (4)

1, a kind of device that utilizes the fluff type biomass material to prepare coal gas, this device comprises raw materials pretreatment system, gas generating system, gas cleaning system, coal gas conveying storage system, wherein gas generating system adopts built-in fast fluidized bed vapourizing furnace, it is characterized in that being provided with built-in cyclonic separator in the built-in fast fluidized bed vapourizing furnace; The dipleg of built-in cyclonic separator has adopted the flutter valve sealed structure that contains one or more mobile wings, the sealing structure only allow solid materials by and do not allow gas to scurry into, the movable wing of flutter valve can be according to the buildup situation automatic open close in the dipleg.

2, the device that utilizes the fluff type biomass material to prepare coal gas according to claim 1 is characterized in that built-in cyclonic separator links to each other with the coal gas fairlead of sufficient length in the vapourizing furnace, and coal gas fairlead process vapourizing furnace is drawn vapourizing furnace behind the high-temperature zone.

3, the device that utilizes the fluff type biomass material to prepare coal gas according to claim 1 is characterized in that gas cleaning system is combined with the organic solvent washing device by the water washing device to form.

4, the device that utilizes the fluff type biomass material to prepare coal gas according to claim 3 is characterized in that the organic solvent washing device is made of Venturi meter.

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