CN118546703A - Biomass entrained-flow bed gasification system and method - Google Patents

Abstract

The invention relates to the field of biomass gasification, in particular to a biomass entrained flow gasification method and system. The method comprises the following steps: (S1) crushing a biomass raw material for the first time to obtain a crushed material for the first time; (S2) modifying the primary crushed material to obtain a granule; (S3) carrying out secondary crushing on the granular material to obtain biomass powder; (S4) mixing the biomass powder with an oxygen-containing oxidant to obtain a mixture; (S5) carrying out gasification reaction on the mixture to obtain high-temperature synthesis gas and molten slag; and (S6) chilling the high-temperature synthesis gas and the molten slag to obtain the low-temperature synthesis gas and the slag. The system comprises a pulverizing, dense-phase conveying and gasifying unit; the pulverizing unit comprises a first crushing device, a modifying device and a second crushing device; the dense-phase conveying unit comprises a biomass powder bin and a lock hopper; the gasification unit comprises a burner, a gasification furnace and a chilling area. The invention has the advantages of low powder making and conveying energy consumption, high effective gas content, long equipment operation period and the like.

Description

A biomass entrained-flow gasification system and method

Technical Field

The present invention relates to the technical field of biomass gasification, and in particular to a biomass fluidized bed gasification system and method.

Background Art

Biomass is organic matter converted by green plants using solar energy to absorb _CO2 through photosynthesis, including agricultural and forestry waste and domestic garbage. It is a carbon-neutral renewable energy source.

Biomass gasification to produce syngas is the leading technology and core technology for biomass preparation of chemicals. According to different biomass gasification methods, it can be divided into fixed bed gasification, fluidized bed gasification and entrained bed gasification. Biomass entrained bed gasification technology has the characteristics of high reaction rate, large production capacity and easy pressurization, which is particularly suitable for large-scale biomass preparation of green chemicals projects.

However, entrained-bed gasification technology has the following problems:

1. The particle size of the feed particles is required to be in the micron level. However, biomass raw materials generally contain components such as cellulose, hemicellulose and lignin, and have a complex cell wall structure. They generally have low compressive strength and long fibers. Lignin, which is a high molecular polymer, also has a cross-linking effect, making it difficult to directly grind the biomass raw materials into powder, or the grinding requires high energy consumption.

Second, biomass is loose and has low density. The bulk density of biomass powder after direct grinding is only 100-200 kg/m ³ . Therefore, a large amount of gas is required for dense phase gas transportation, resulting in high transportation energy consumption and reducing the effective gas content in the gasification reaction product.

3. Hemicellulose in biomass has poor thermal stability, fast reaction rate after heating, and mainly volatile matter; cellulose has slightly stronger thermal stability, lignin has the strongest thermal stability, and slower reaction rate after heating. Moreover, cellulose and lignin produce carbonized substances after pyrolysis, and the reaction time required for gasification is longer. The uneven distribution of hemicellulose, cellulose, and lignin in the powder after direct grinding of biomass may lead to insufficient gasification reaction of part of the powder, resulting in reduced carbon conversion rate.

4. Trace components in biomass have a great impact on the gasification process, such as causing ash accumulation and slag blockage in the waste boiler and corrosion in the gasifier area, which will affect the long-term safe operation of the gasification equipment.

Summary of the invention

The purpose of the present invention is to solve the problems raised in the background technology and to provide a biomass fluidized bed gasification system and method.

In order to achieve the above-mentioned object of the invention, the first aspect of the present invention provides a biomass entrained flow gasification method, the method comprising the following steps:

(S1) crushing the biomass raw material to obtain a primary crushed material;

(S2) modifying the primary crushed material to obtain a granular material;

(S3) crushing the pellets for a second time to obtain biomass powder;

(S4) mixing the biomass powder with an oxygen-containing gasifying agent to obtain a mixed material;

(S5) subjecting the mixed material to a gasification reaction to obtain high-temperature synthesis gas and molten slag;

(S6) The high-temperature synthesis gas and molten slag are quenched to obtain low-temperature synthesis gas and ash.

The second aspect of the present invention provides a system for the above method, the system comprising a pulverizing unit, a dense phase conveying unit and a gasification unit connected in sequence; wherein:

The milling unit comprises a first crushing device, a modifying device and a second crushing device which are connected in sequence;

The dense phase conveying unit comprises a biomass powder bin and a lock bucket connected in sequence; the biomass powder bin is connected to the second crushing device;

The gasification unit includes a burner, a gasification furnace and a quenching area; the burner is arranged on the top of the gasification furnace, and the burner is connected to the lock bucket of the dense phase conveying unit; the quenching area is below the gasification furnace; the bottom of the gasification unit is an ash discharge port;

Preferably, the inner lining of the gasifier is provided with a cooling water outlet and a cooling water inlet; the quenching area is provided with a quenching water inlet and a black water outlet, and a flushing water distribution pipe is provided in the quenching area.

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

(1) In the milling unit of the present invention, the biomass raw material is successively crushed, modified and crushed twice. During this period, the relaxed density and bulk density of the biomass are greatly improved by using lower energy consumption, so that dense phase transportation can be achieved by using less gas transportation medium in the subsequent dense phase transportation unit, thereby reducing the transportation energy consumption and increasing the effective gas content in the gasification reaction product.

(2) In the powder making unit of the present invention, cellulose, hemicellulose and a certain amount of lignin are evenly distributed in the biomass through modification and secondary crushing, thereby ensuring the uniformity of each powder particle when the biomass powder is gasified, and preventing part of the powder from escaping from the gasifier due to excessive lignin content and not having time to react, thereby ensuring that the gasification reaction has a high carbon conversion rate.

(3) In the gasification unit of the present invention, circulating cooling water is provided in the lining of the gasifier, which reduces the lining temperature. The molten slag forms a solid slag layer on the surface of the lining, thereby preventing the molten slag containing a high content of alkali metal elements from corroding the lining under high temperature conditions, thereby extending the service life of the lining of the gasifier.

(4) In the gasification unit of the present invention, the temperature of the gasification product out of the waste boiler is increased, thereby avoiding the temperature range of alkali metal condensation and precipitation, ensuring that no alkali metal dust is deposited in the waste boiler section of the gasifier, and realizing long-term safe and stable operation of the radiation waste boiler of the gasifier.

(5) In the gasification unit of the present invention, the water temperature and water flow of the quenching water are adjusted in the quenching area so that the working temperature of the quenching area is ≤200°C; in addition, flushing water is introduced into the quenching area to flush the inner side of the shell and the internal parts of the quenching area, so that the inner side of the shell and the internal parts of the quenching area are always in a low chloride ion concentration environment, thereby extending the service life of the equipment and pipelines under high chlorine conditions, reducing the material requirements of the gasification equipment, and ensuring the adaptability of the gasification device to high-chlorine straw raw materials.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic flow diagram of a biomass entrained flow gasification method provided by the present invention;

FIG2 is a schematic diagram of a biomass entrained flow gasification system provided by the present invention;

FIG3 is a schematic diagram of another biomass entrained flow gasification system provided by the present invention;

FIG4 is a schematic diagram of another biomass fluidized bed gasification system provided by the present invention, which includes a silo pump and a filter.

DETAILED DESCRIPTION

The specific implementation of the present invention will be further described below in conjunction with the accompanying drawings.

It is easy to understand that according to the technical solution of the present invention, without changing the essential spirit of the present invention, a person skilled in the art can replace various structural modes and implementation modes with each other. Therefore, the following specific implementation modes and drawings are only exemplary descriptions of the technical solution of the present invention, and should not be regarded as the whole of the present invention or as a limitation or restriction to the technical solution of the invention.

As shown in FIG1 , the first aspect of the present invention provides a biomass entrained flow gasification method, the method comprising the following steps:

(S1) crushing the biomass raw material to obtain a primary crushed material;

(S2) modifying the primary crushed material to obtain a granular material;

(S3) crushing the pellets for a second time to obtain biomass powder;

(S4) mixing the biomass powder with an oxygen-containing gasifying agent to obtain a mixed material;

(S5) subjecting the mixed material to a gasification reaction to obtain high-temperature synthesis gas and molten slag;

(S6) The high-temperature synthesis gas and molten slag are quenched to obtain low-temperature synthesis gas and ash.

In some embodiments, in step (S1), the biomass raw material is selected from crop straw, forest trees, Salix psammophila, Phragmites australis, animal manure, etc.

The inventors have found that lignin acts as a binder during extrusion granulation. The more lignin content there is, the stronger the binding effect during granulation and the greater the particle density. In the present invention, the lignin content of the biomass raw material is 5% to 50%, preferably 10% to 40%.

Furthermore, the primary crushing is preliminary crushing, such as impact and cutting, so that the particle size of the primary crushed material is ≤5 mm;

Furthermore, screening and impurity removal can be performed before and after the primary crushing, and preferably the particle size of the primary crushed material is ≤3 mm.

In some embodiments, in step (S2), the modification is performed by physical modification, such as extrusion molding.

Furthermore, the extrusion molding can be hot pressing at high temperature or cold pressing at room temperature, which depends on the extrusion molding pressure. Preferably, the extrusion molding pressure is ≥5MPa.

The extrusion molding enables the relaxed density of the pellets to reach more than 800 kg/ ^m3 , thereby achieving densification of the biomass.

Furthermore, the specific gravity of the densified biomass increases, and the bulk density of the biomass powder obtained after secondary crushing is high. Therefore, only a small amount of gas is needed to achieve dense phase transportation of biomass powder, and the transportation density can reach more than 300kg/ ^m3 , greatly reducing the transportation energy consumption.

The inventors of the present invention unexpectedly discovered that, according to the different characteristics of different biomass raw materials, the relaxed density of biomass pellets can be changed by adjusting the particle size of the primary crushing, the applied pressure of the extrusion molding, the addition of a binder, and the mixing ratio of different biomass mixtures, thereby adjusting its grindability and the transportability characteristics such as the bulk density of the biomass powder. By designing repeated experiments, the optimal process conditions can be obtained, and the relaxed density of the pellets can even reach more than 1000kg/ ^m3 .

Furthermore, the binder is selected from starch and kaolin, and the content of the binder is 0-10%.

In some embodiments, in step (S3), the secondary crushing can be selected from crushing, grinding or a combination thereof known in the art, exemplified by ball mill, air flow mill, pressure roller mill, ring roller mill, fan mill, hammer mill, roller bowl mill, roller ring mill, roller ball mill, roller disc mill or roller mill, so that the particle size of the obtained biomass powder is ≤1 mm.

Furthermore, when the secondary crushing makes the particle size of the biomass powder less than 1 mm, the bulk density of the biomass powder is ≥500 kg/m ³ ;

Preferably, when the secondary crushing makes the particle size of the biomass powder less than 200 μm, or the extrusion pressure is increased, the bulk density of the biomass powder can reach 550 kg/m ³ .

The inventors found that the modification increased the mixing between lignin, cellulose and hemicellulose in the biomass raw materials. In addition, the secondary crushing of the pellets further increased the mixing between the different components in the biomass raw materials, and the pellets achieved pulverization and particle size refinement, which ultimately resulted in the uniform distribution of cellulose, hemicellulose and lignin in the biomass in each biomass powder. Therefore, the reaction rates of each powder particle in the biomass powder are relatively consistent, ensuring the uniformity of the biomass powder in the gasification reaction, avoiding the excessive proportion of lignin in some biomass powders and escaping from the gasifier before reacting, thereby ensuring the carbon conversion rate of the gasification reaction.

The inventors have also found that the modification causes deformation and filling between biomass particles, and the lignin has a certain fluidity when softened, which increases the bonding between fiber structures. In addition, due to the bonding effect of the softened lignin, the secondary crushing after the modification prevents the fiber structure in the material from being cut or ground due to bending, fundamentally destroying the original fiber tissue structure, making the powder sphericity better, that is, the fluidity of the biomass powder is good.

In some embodiments, the biomass powder obtained after the secondary crushing can be filtered to remove dust when the conveying gas is discharged, and then enters the powder bin for storage.

In some embodiments, in step (S4), the oxygen-containing gasifying agent is pure oxygen or a mixture containing oxygen, such as oxygen, a mixture of oxygen and carbon dioxide, a mixture of oxygen and water vapor, or a mixture of oxygen, carbon dioxide and water vapor.

Furthermore, the mixing ratio of the oxygen-containing gasifying agent and the biomass powder is such that the temperature of the gasification reaction exceeds the ash melting point of the biomass raw material by 50 to 100°C.

In some embodiments, in step (S4), the biomass powder is transported and mixed with the oxygen-containing gasification agent by dense phase transport; wherein,

In the dense phase transport process, _CO2 or _N2 is used as the transport medium for dense phase transport. Using biomass powder with a higher density can reduce the use of transport medium gas, which can make the content of transport medium in the subsequent gasification reaction product less.

There are two ways to control the conveying flow rate in the dense phase conveying process:

First, the biomass powder in the powder bin is transported to the lock hopper, and the lock hopper is pressurized so that the biomass powder in the lock hopper enters the feed tank, and the transport flow rate is controlled by controlling the pressure difference between the feed tank and the burner;

Furthermore, the pressure difference between the feed tank and the burner is 0.1-1 MPa, and the pressure difference between the feed tank and the gasifier can be controlled by controlling the pressure of the feed tank.

Secondly, the biomass powder in the powder bin is transported to two lock hoppers, which transport the materials alternately, wherein each lock hopper is equipped with a feeding valve that independently controls the feeding rate. The feeding rate is related to the specific system scale.

Furthermore, the advantage of this is that the biomass powder is in a normal pressure state when it falls from the powder bin into the lock bucket. Compared with the falling under pressurized conditions, the falling under normal pressure is smoother, avoiding the bridging problem that is easy to occur under pressurized conditions, thereby ensuring the safety and stability of the dense phase conveying unit.

In another specific embodiment, when a feeding valve is used to control the conveying flow rate, the dense phase conveying unit is equipped with more than two lock hoppers, and each lock hopper is equipped with a feeding valve that independently controls the feeding rate.

In some embodiments, in step (S5), the gasification reaction is well known to those skilled in the art; the temperature of the gasification reaction may be 1100° C. to 1500° C., and the pressure of the gasification reaction may be 0.1 to 6.5 MPa.

The gas product of the gasification reaction has an effective gas content of 45-90%, wherein the _H2 content is 20-40%, and the CO content is 25-50%.

Furthermore, in the gas product, the remaining gas except the effective gas is the transport medium and trace gases such as N ₂ , NH ₃ , H ₂ S, etc.

Furthermore, when the gasification reaction is carried out, the temperature of the inner wall of the gasification reaction device (i.e., the gasifier lining described below) is ≤400°C by setting a gasifier lining and cooling the inner wall of the gasifier, and preferably the temperature of the inner wall is ≤350°C.

In some embodiments, in step (S6), some biomass raw materials have a high content of halogen elements such as chlorine, resulting in a high concentration of chloride ions in the water in the quenching area (which contains a certain amount of ash, also called black water), which may cause corrosion to equipment and pipelines at high temperatures.

Therefore, the inventors used quenching water to quench the high-temperature synthesis gas and molten slag;

In some embodiments, in step (S6), the working temperature of the quenching zone is ≤200°C, preferably the working temperature of the quenching zone is ≤150°C.

Furthermore, the working temperature of the quenching zone is controlled by adjusting the water temperature and water flow rate of the quenching zone entering the gasifier. For example, the temperature of the quenching water is 70-250°C and the flow rate is 50-300t/h. At this time, the corrosion rate of equipment and pipelines can be ignored.

A second aspect of the present invention provides a system for the above method, the system comprising a pulverizing unit, a dense phase conveying unit and a gasification unit connected in sequence.

As shown in FIG. 2 to FIG. 4 , in some embodiments, the powder making unit includes a first crushing device, a modifying device, and a second crushing device connected in sequence.

Furthermore, the powder making unit includes a first crushing device, a modifying device and a second crushing device which are sequentially connected along the material; the biomass raw material enters from the first crushing device, and sequentially passes through the modifying device and the second crushing device to obtain biomass powder.

In some embodiments, in the powder making unit, a silo pump and a filter are provided downstream of the second crushing device along the material flow direction (as shown in FIG. 4 ).

Furthermore, the silo pump is used to transport biomass powder to the filter. The silo pump is provided with a first transport gas inlet for transporting the secondary crushed material to the filter through the first transport gas at the first transport gas inlet. The first transport gas is a commonly used transport gas in the art, such as _N2 or _CO2 .

In some embodiments, the filter is used to screen out the part of the biomass powder after secondary crushing that is suitable for dense phase transportation. The filter is a conventional gas-solid filter in the art, and an exhaust port is provided on the filter, and the separated gas is discharged into the atmosphere from the exhaust port, and the separated biomass powder enters the biomass powder bin.

The present invention finds that the arrangement of the silo pump and the filter can realize the long-distance and high-altitude transportation of biomass powder, so that the powder making unit and the dense phase conveying unit can be arranged at different positions and heights, without having to arrange the second crushing device above the biomass powder silo, thereby reducing the requirements for the frame floor space and height, thereby reducing the frame investment.

In some embodiments, the dense phase conveying unit includes a biomass powder bin and a lock hopper connected in sequence; the biomass powder bin is connected to the second crushing device; the biomass powder enters the powder bin for storage, and then enters the lock hopper for conveyance to the downstream gasification unit.

Furthermore, the dense phase conveying unit also includes a feed tank (as shown in Figure 2) or a feeding valve (as shown in Figure 3) located downstream of the lock hopper, wherein the burner and the lock hopper are connected through a pipeline equipped with the feed tank or the feeding valve, and a second conveying gas inlet is also provided on the pipeline. The biomass powder output from the lock hopper is densely transported to the burner of the following gasification unit through the second conveying gas entering the second conveying gas inlet.

In some embodiments, the gasification unit includes a burner, a gasifier, and a quenching zone;

Furthermore, the biomass powder from the lock hopper enters the burner to mix with the oxygen-containing gasifying agent, and then enters the gasifier for gasification, and the gasification product is cooled through the quenching area;

In some embodiments, the gasifier is a place where biomass powder and oxygen-containing gasifying agent undergo gasification reaction, and below the gasifier is a quenching area; the bottom of the gasification unit is an ash outlet.

Furthermore, the inner lining of the gasifier is provided with a cooling water outlet and a cooling water inlet, so as to facilitate the introduction of circulating cooling water into the inner lining of the gasifier.

The inventors have found that the content of alkali metal elements in biomass ash is relatively high, and the slag produced during the gasification process will corrode the lining of the gasifier.

Therefore, in some embodiments, the present inventors introduce cooling water into the gasifier lining to lower the lining temperature so that the slag containing a high alkali metal content solidifies into solid slag when encountering a colder lining, thereby avoiding corrosion of the gasifier lining by the slag and ultimately extending the service life of the gasifier lining.

Furthermore, the cooling water makes the temperature of the gasifier lining ≤400°C, preferably the temperature ≤350°C.

In some embodiments, the burner is used for feeding biomass powder and oxygen-containing gasifying agent, and the top of the gasifier is provided with a burner, which is connected to the lock bucket of the dense phase conveying unit.

In some embodiments, the gasification unit further comprises a waste pot located between the gasifier and the quenching zone.

The waste boiler recovers the sensible heat of the synthesis gas and produces steam as a by-product, thereby improving the heat utilization efficiency of the gasification system.

In some embodiments, the high-temperature synthesis gas and molten slag produced by the gasification reaction can enter a waste boiler to exchange heat with boiler water, and the waste boiler can be used to recover the sensible heat of the synthesis gas and produce steam as a by-product.

The inventors have found that the content of alkali metal elements in biomass molten slag is relatively high. When heat exchange is performed at a waste boiler, as the temperature of the high-temperature synthesis gas decreases, the alkali metal elements in the molten slag condense, which easily causes contamination of the heat exchange surface of the waste boiler.

Therefore, in some embodiments, the inventors design the synthesis gas temperature at the outlet of the waste boiler to be greater than 700°C to avoid the temperature range of alkali metal condensation and precipitation, which can ensure that no alkali metal dust is deposited in the waste boiler section of the gasification device, and realize the long-term safe and stable operation of the radiation waste boiler;

Furthermore, when the gasification reaction is carried out, the temperature of the synthesis gas at the outlet of the waste boiler is ≥800°C.

In some embodiments, the quenching area is used to cool the product of the gasification reaction, and the quenching area is provided with a quenching water inlet and a black water outlet, and a flushing water distribution pipe, a syngas outlet and an ash outlet are provided in the quenching area;

Furthermore, the flushing water enters the flushing water distribution pipe through the flushing water inlet, and evenly flushes the inner side of the shell and internal parts of the gasification unit.

In some embodiments, after leaving the waste boiler, the high-temperature syngas and molten slag enter a quenching area, where the syngas and molten slag are quenched by quenching water to obtain low-temperature syngas and ash. In the quenching area, the syngas and molten slag are cooled to 100° C. to 300° C. by quenching water before being discharged from the gasification unit.

Furthermore, the synthesis gas is discharged from the gasification unit through the synthesis gas outlet of the quenching area, and the ash obtained after the molten slag is quenched is discharged from the gasification unit through the ash outlet.

The inventors have found that some biomass raw materials contain high levels of halogen elements such as chlorine, resulting in high chloride ion concentrations in the water in the quenching zone (which contains a certain amount of ash, also known as black water), which can cause corrosion to equipment and pipelines at high temperatures.

Therefore, the present inventors use quenching water to quench the high-temperature synthesis gas and molten slag, so that the working temperature of the quenching zone is ≤200°C, preferably the working temperature of the quenching zone is ≤150°C, at which time the corrosion rate of equipment and pipelines can be ignored.

Furthermore, the working temperature of the quenching zone is controlled by adjusting the water temperature and water flow rate of the quenching zone entering the gasifier, for example, the temperature of the quenching water is 70-250° C., and the flow rate is 50-300 t/h.

In addition, in some embodiments, the inventors also introduce flushing water into the quenching area to evenly flush the inner side of the shell and the internal parts of the quenching area, so that they are always in a low chloride ion concentration environment. Ultimately, the service life of the equipment and pipelines under high chlorine conditions is extended, the material requirements of the gasification equipment are reduced, and the adaptability of the gasification device to high-chlorine straw raw materials is ensured.

Furthermore, the temperature of the flushing water can be room temperature.

The present invention is further described below by specific examples. The raw materials used in the following examples and comparative examples are as follows:

The biomass raw material is corn stalks, and its specific information is shown in Table 1:

Table 1: Analysis results of corn stover

The explanations of the various specialized terms mentioned in this article are as follows:

Relaxed density: The compressed density of the molded block obtained by extruding biomass particles gradually decreases after it is ejected from the mold due to elastic deformation and stress relaxation. The density of the molded block is obtained after it stabilizes for a period of time.

Bulk density: The mass per unit volume measured when biomass powder is freely filled in a container just after filling is completed.

Carbon conversion rate: The ratio of the mass of carbon in the gas product to the mass of carbon in the raw material after the raw material undergoes gasification reaction. It reflects the degree of gasification reaction. The higher the carbon conversion rate, the more thorough the gasification reaction.

Effective gas content: the sum of the contents of CO and _H2 in the gasification reaction products.

Specific biomass consumption: the mass of biomass consumed per thousand cubic meters of effective gas.

Specific oxygen consumption: the volume of oxygen consumed per thousand cubic meters of effective gas.

Carbon conversion rate: the ratio of the mass of carbon in the gas product to the mass of carbon in the raw material.

Example 1 (A1)

According to the above-mentioned system and method, as shown in FIG2 , this embodiment 1 mainly performs the following steps:

1. Preparation of biomass powder

(1) Screening and removing impurities from corn stalks, and then crushing them once using a hammer crusher to obtain a primary crushed material; wherein:

The lignin content of the corn stalks is 15.6%, and the particle size _d1 of the primary crushed material is _D90 =5 mm.

(2) Extruding the primary crushed material through a pelletizing machine to obtain corn stalk pellets; wherein:

The extrusion molding temperature is 120°C and the pressure is 8MPa;

The relaxed density of the corn stalk pellets is 950 kg/m ³ .

(3) crushing the corn stalk pellets for a second time using a roller mill to obtain corn stalk powder; wherein:

The particle size _d2 of the corn stalk powder is _D90 =1 mm, and the bulk density is 540 kg/ ^m3 .

The power consumption during the preparation of biomass powder is 110 (kW·h)/t.

2. Dense phase transportation of biomass powder

(4) The corn stalk powder is stored in a powder bin, the corn stalk powder in the powder bin is input into a lock bucket, and after the lock bucket is pressurized to 3.5 MPa, the corn stalk powder in the lock bucket enters a feed tank;

(5) _CO2 gas is used to densely transport corn stalk powder in the feeding tank to the burner of the gasification device; at the same time, oxygen is transported to the burner; wherein,

The pressure of the _CO2 gas is 4MPa, and the pressure difference between the feed tank and the burner is 0.5MPa;

The conveying density of the corn stalk powder is 350 kg/km ³ , and the CO ₂ consumption in the conveying process is 102.9 Nm ³ /t.

3. Biomass gasification reaction

(6) corn stalk powder and oxygen enter the entrained flow gasifier through a burner to undergo a gasification reaction to obtain high-temperature synthesis gas and molten slag; wherein:

The temperature of the gasification reaction is 1300°C and the pressure is 3MPa;

Circulating cooling water is introduced into the inner lining of the gasifier to make the temperature of the inner lining reach 350°C.

(7) The high-temperature synthesis gas enters the waste boiler and exchanges heat with boiler water. The waste boiler is used to recover the sensible heat of the synthesis gas and produce steam as a by-product. At this time, the synthesis gas temperature is reduced and leaves the waste boiler; wherein,

The temperature of the high-temperature synthesis gas when leaving the waste boiler is 800°C.

(8) The syngas and molten slag after heat exchange enter a quenching zone, where the syngas and molten slag are quenched by quenching water to obtain low-temperature syngas and ash; wherein:

The quenching water makes the working temperature of the quenching area 185°C, that is, the temperature of the low-temperature synthesis gas, the temperature of the ash and the temperature of the quenching water are all 185°C;

Furthermore, the temperature of the quenching water is 150°C and the flow rate is 220t/h;

Flushing water is also introduced into the quenching area to evenly flush the inside of the shell and internal parts of the quenching area. The temperature of the flushing water is 20° C. and the flow rate is 20 t/h.

The low-temperature synthesis gas is discharged through the synthesis gas outlet of the quenching area, and the ash is discharged through the ash discharge outlet at the bottom of the gasification unit.

In the gas product of the gasification reaction, the content of _H2 is 30.91%, the content of CO is 37.59%, the content of _CO2 is 30.61%, and the content of other gases ( _N2 , _NH3 , _H2S and other trace gases) is 0.89%, that is, the effective gas content in the gasification reaction product is 68.50%.

In the gaseous product of the gasification reaction, the specific biomass consumption is 1026 kg/kNm ³ , the specific oxygen consumption is 243 Nm ³ /kNm ³ , and the carbon conversion rate is 99%.

According to evaluation, the service life of the gasifier lining can reach 10 years, the cleaning cycle of the boiler heat exchange surface is 6 months, and the service life of the quenching area material can reach 5 years.

Example 2 (A2)

Refer to Example 1, as shown in Figure 3, the difference is that in the dense phase transportation of biomass powder,

In step (4), the corn stalk powder is stored in a powder bin, the corn stalk powder in the powder bin is fed into a lock hopper A, and the lock hopper A is pressurized to 3.5 MPa; at the same time, the corn stalk powder in the lock hopper B is delivered to the burner of the gasification device through the feed valve B and _CO2 gas; after the feed of the lock hopper B is completed, the lock hopper B is depressurized to normal pressure; at the same time, oxygen is delivered to the burner;

In step (5), the corn stalk powder in the powder bin is fed into the lock hopper B, and the lock hopper B is pressurized to 3.5 MPa; at the same time, the corn stalk powder in the lock hopper A is transported to the burner of the gasification device through the feed valve A and the CO2 gas; after the lock hopper A completes the feeding, the lock hopper A is depressurized to normal pressure; at the same time, oxygen is transported to the burner;

Step (4) and step (5) are repeated alternately until all the corn stalk powder is transported to the burner of the gasification unit.

In Example 2, since the corn straw powder is in a normal pressure state when it falls from the powder bin into the locking bucket, the normal pressure falling is smoother than the falling under pressurized conditions, avoiding problems such as bridging that are prone to occur under pressurized conditions, thereby ensuring the safety and stability of the biomass dense phase conveying unit.

Example 3 (A3)

Refer to Example 1, except that:

In step (1), the lignin content of the corn stalk is 10%;

In step (2), the relaxed density of the corn stalk pellets is 600 kg/m ³ ;

In step (3), the bulk density of the corn stalk powder is 200 kg/m ³ ;

The power consumption during the preparation of biomass powder is 116 (kW·h)/t;

In step (5), the transportation density of the corn stalk powder is 180 kg/km ³ , and the CO ₂ consumption during the transportation process is 185.3 Nm ³ /t.

In the gaseous product of the gasification reaction, the content of _H2 is 27.39%, the content of CO is 36.48%, the content of _CO2 is 35.39%, and the content of other gases is 0.74%, that is, the effective gas content in the gasification product is 63.87%.

In the gaseous product of the gasification reaction, the specific biomass consumption was 1051 kg/kNm ³ , the specific oxygen consumption was 366 Nm ³ /kNm ³ , and the carbon conversion rate was 96%.

It can be seen from Examples 1 and 3 that the lignin content plays a role of a binder during the extrusion granulation process. Within a certain range, the greater the lignin content, the stronger the bonding effect during the granulation process and the greater the particle density.

Comparative Example 1 (D1)

Refer to Example 1, except that:

Do not perform step (2);

In step (3), the bulk density of the corn stalk powder is 150 kg/m ³ ;

The power consumption in the preparation process of biomass powder is 120 (kW·h)/t

In step (5), the transportation density of the corn stalk powder is 100 kg/km ³ , and the CO ₂ consumption during the transportation process is 359.0 Nm ³ /t.

In the gaseous product of the gasification reaction, the content of _H2 is 21.33%, the content of CO is 33.52%, the content of _CO2 is 44.56%, and the content of other gases is 0.59%, that is, the effective gas content in the gasification product is 54.86%.

In the gaseous product of the gasification reaction, the specific biomass consumption was 1115 kg/kNm ³ , the specific oxygen consumption was 422 Nm ³ /kNm ³ , and the carbon conversion rate was 95%.

Comparative Example 2 (D2)

Refer to Example 1, except that:

In step (6), the inner lining of the gasifier is insulated with refractory bricks, and no circulating cooling water is introduced, and the working temperature of the inner lining is 1300° C.;

According to evaluation, the service life of the gasifier lining is only 3 months.

In Comparative Example 2, the working temperature of the refractory bricks is relatively high, especially the working temperature of the fire-facing bricks reaches 1300°C. When the slag of corn straw powder flows over the surface of the refractory bricks, the high-alkali metal slag corrodes the refractory bricks, causing the refractory bricks to become thinner and have a shorter service life. The refractory bricks need to be replaced every 3 months.

Comparative Example 3 (D3)

Refer to Example 1, except that:

In step (7), the temperature of the synthesis gas when leaving the waste boiler is 500°C.

In comparative example 3, although the high-temperature synthesis gas is reduced from 1300°C to 500°C in the waste boiler, more sensible heat is recovered and a large amount of by-product steam is produced. However, during the cooling process, especially after it is reduced to 700°C, the alkali metal vapor condenses from the gaseous state, which easily causes the heat exchange surface of the waste boiler to be contaminated. The waste boiler heat exchange surface needs to be shut down and cleaned every two months.

Comparative Example 4 (D4)

Refer to Example 1, except that:

In step (8), the operating temperature of the quenching zone is 220° C., that is, the temperature of the low-temperature synthesis gas, the temperature of the ash and the temperature of the quenching water are all 220° C.;

Furthermore, the temperature of the quenching water is 205° C. and the flow rate is 220 t/h.

In Comparative Example 4, the temperature of the quenching water is relatively high, so that the temperature of the low-temperature synthesis gas after quenching is relatively high, and the water vapor content in the low-temperature synthesis gas is also relatively high, which is beneficial to the subsequent shift reaction. However, because the temperature of the quenching water after quenching is also relatively high, the corrosion rate of chloride ions on equipment and pipelines is relatively fast, and the quenching area materials need to be replaced every 2 years.

Comparative Example 5 (D5)

Refer to Example 1, except that:

In step (8), no flushing water is introduced into the quenching zone.

In Comparative Example 5, due to the high chloride ion concentration near the shell and internal parts of the quenching area, the chloride ion corrosion rate on the equipment and pipelines is fast, and the quenching area materials need to be replaced every 3 years.

Claims (10)

1. A biomass entrained flow gasification method, characterized in that the method comprises the following steps: (S1) crushing the biomass raw material to obtain a primary crushed material; (S2) modifying the primary crushed material to obtain a granular material; (S3) crushing the pellets for a second time to obtain biomass powder; (S4) mixing the biomass powder with an oxygen-containing gasifying agent to obtain a mixed material; (S5) subjecting the mixed material to a gasification reaction to obtain high-temperature synthesis gas and molten slag; (S6) The high-temperature synthesis gas and molten slag are quenched to obtain low-temperature synthesis gas and ash. 2. The method according to claim 1, characterized in that in step (S1), the biomass raw material is selected from crop straw, forest trees, Salix psammophila, Phragmites australis, and animal manure; The lignin content of the biomass raw material is 5% to 50%, preferably 10% to 40%; The primary crushing makes the particle size of the primary crushed material ≤5mm. 3. The method according to claim 1 or 2, characterized in that, in step (S2), the modification method is extrusion molding; Preferably, a binder is added during the extrusion molding process; Furthermore, the extrusion molding pressure is ≥5MPa; Furthermore, the binder is selected from starch and kaolin, and the content of the binder is 0-10%. 4. The method according to any one of claims 1 to 3, characterized in that in step (S3), the secondary crushing uses a ball mill, an air flow mill, a pressure roller mill, a ring roller mill, a fan mill, a hammer mill, a roller bowl mill, a roller ring mill, a rolling ball mill, a roller disc mill or a roller mill; The secondary crushing makes the particle size of the biomass powder ≤1 mm. 5. The method according to any one of claims 1 to 4, characterized in that in step (S4), the oxygen-containing gasifying agent is oxygen, a mixture of oxygen and carbon dioxide, a mixture of oxygen and water vapor, or a mixture of oxygen, carbon dioxide and water vapor; Preferably, the mixing ratio of the oxygen-containing gasifying agent and the biomass powder is such that the temperature of the gasification reaction exceeds the ash melting point of the biomass raw material by 50 to 100°C. 6. The method according to any one of claims 1 to 5, characterized in that in step (S4), the biomass powder is transported to a receiving device containing the oxygen-containing gasification agent by dense phase transport, wherein: Control the delivery flow by controlling the pressure difference between the biomass storage and receiving device, or A flow control device, such as a feed valve, is provided in the conveying path to control the conveying flow rate. 7. The method according to any one of claims 1 to 6, characterized in that in step (S5), the temperature of the gasification reaction is 1100 to 1500°C and the pressure is 0.1 to 6.5 MPa; When the gasification reaction is carried out, the temperature of the inner wall of the gasification reaction device is made ≤400°C by arranging the gasification furnace lining and cooling the gasification furnace lining. 8. The method according to any one of claims 1 to 7, characterized in that in step (S6), the quenching is performed so that the working temperature of the quenching area is ≤ 200°C. 9. A system for the method according to any one of claims 1 to 8, characterized in that the system comprises a pulverizing unit, a dense phase conveying unit and a gasification unit connected in sequence according to a logistics sequence; wherein: The milling unit comprises a first crushing device, a modifying device and a second crushing device which are sequentially connected according to a logistic sequence; The dense phase conveying unit comprises a biomass powder bin and a lock bucket which are connected in sequence according to the logistics sequence; the biomass powder bin is connected to the second crushing device; The gasification unit comprises a burner, a gasification furnace and a quenching area; the burner is arranged on the top of the gasification furnace, and the burner is connected to the lock bucket of the dense phase conveying unit; the quenching area is below the gasification furnace, and the quenching area is provided with a synthesis gas outlet; the bottom of the gasification unit is an ash outlet; Preferably, the inner wall of the gasifier is provided with an inner lining, and the inner lining is provided with a cooling water outlet and a cooling water inlet; the quenching area is provided with a quenching water inlet and a black water outlet, and a flushing water distribution pipe is provided in the quenching area. 10. The system of claim 9, wherein the gasification unit further comprises a waste boiler located between the gasification furnace and the quenching zone.