CN112980513A

CN112980513A - Constant-density biomass gasification furnace

Info

Publication number: CN112980513A
Application number: CN202110244538.7A
Authority: CN
Inventors: 管继富; 张因富; 李雪庆
Original assignee: Beijing Institute of Technology BIT
Current assignee: Beijing Institute of Technology BIT
Priority date: 2021-03-05
Filing date: 2021-03-05
Publication date: 2021-06-18
Anticipated expiration: 2041-03-05
Also published as: CN112980513B

Abstract

The invention provides a constant-density biomass gasification furnace, which comprises a furnace body, a movable furnace cover and a self-rotating nozzle, wherein a material pressing mechanism is arranged on the movable furnace cover, the material pressing mechanism comprises a driving device and a material pressing disc, and the material pressing disc is used for providing downward constant pressure for biomass fuel in the furnace body under the driving of the driving device; therefore, the biomass fuel feeding device has the advantages that the material pressing mechanism arranged on the movable furnace cover can provide continuous top-down pressure or intermittent impact striking action for the biomass fuel in the material storage area in the furnace, so that the fuel layer can stably descend, the compactness of the material layer is improved, and the material layer bridging phenomenon is eliminated; meanwhile, the self-rotating nozzle enables the gasification agent to uniformly enter the reaction zone from the central direction, so that the oxidation layer and the reduction layer are stable and balanced, and the burn-through phenomenon is eliminated; in addition, the invention is easy to realize automatic control of other operation processes except for filling biomass raw materials and discharging the biochar, thereby greatly reducing the operation cost and having better economic applicability.

Description

Constant-density biomass gasification furnace

Technical Field

The invention belongs to the technical field of biomass gasification furnaces, and particularly relates to a constant-density biomass gasification furnace.

Background

As is known, biomass is a sustainable green resource, and is a resource acquisition channel on which energy structure transformation, atmospheric pollution treatment and CO2 emission reduction in China can depend. However, biomass resources are dispersed, the bulk density is low, the collection and transportation are difficult, and most of the biomass is not properly used. At present, in China, the straw is randomly burned or discarded in agriculture, and the excessive and inefficient use of chemical fertilizers causes serious environmental pollution and consumes great energy of local governments. In order to thoroughly solve the problems, a biomass high-value processing technology, namely a biomass gasification technology, which can be popularized in a large scale is urgently needed.

Biomass gasification is a process of converting combustible substances in biomass into combustible gas through thermochemical reaction under high temperature conditions by using biomass as a raw material and using oxygen (air, oxygen-rich gas or pure oxygen, and the like), water vapor or hydrogen and other gases as gasifying agents. The most fundamental difference between gasification technology and direct combustion technology is that the gasification process requires a limited supply of several gasifying agents. The main combustible components of biomass gasification to produce combustible gas are CO, H2, CH4, and also a very small amount of CnHm (n > 1). In addition to the production of combustible gases, biomass gasification also produces a certain amount of by-products, such as biochar, tar, and the like. The biomass energy-saving furnace can convert low-grade solid biomass into high-grade combustible gas, thereby being widely applied to various fields of industrial and agricultural production, and being particularly suitable for heating in winter in rural areas and heat energy for small and medium enterprises.

The biomass gas can be directly sent into energy-consuming equipment such as a boiler and the like for combustion and utilization, or sent into an internal combustion generator set for power generation after being cooled and purified.

The biochar is rich in a large number of micropores and mesopores, and is prepared into a carbon-based fertilizer together with nitrogen, phosphorus and potassium, so that fertilizer slow release, soil water retention and contaminated soil remediation can be realized.

The biomass gasification utilization can comprise a gasification gas supply technology, a gasification heat supply technology, a gasification power generation technology, a gasification hydrogen production technology and the like. At present, the biomass gasification technology develops rapidly, and the gasification gas supply and heat supply are mainly used for developing towards large biomass gasification devices such as gasification power generation, combined cooling heating and power generation and the like. The development of medium and small biomass gasification devices is slow.

Although biomass gasification and utilization are wide, biomass gasification cannot be popularized in a large quantity, and factors mainly influencing biomass gasification development include:

(one) Fuel factor:

the biomass raw materials are various and comprise wood, herbs, urban organic garbage, animal wastes and the like. Although the biomass resources available in China are abundant, the fuel distribution is wide and uneven, a large biomass gasification device needs to spend higher biomass storage and transportation cost, the fuel cost in the biomass gasification process is greatly increased, and meanwhile, the development of large biomass gasification is restricted due to insufficient fuel supply caused by low profit and low enthusiasm of farmers. Although the existing small and medium-sized biomass gasification devices can be obtained from local materials, a gasification furnace type which has strong raw material adaptability and stable and reliable operation is not available; the existing biomass gasification furnace mostly uses fuels with high energy density such as formed fuels as raw materials, the processing process of the formed fuels also has high energy consumption and higher storage and transportation cost, and finally, the fuel cost is greatly increased, thereby limiting the large popularization of small and medium-sized household gasification devices.

(II) combustible gas purification factors:

at present, gasification gas production of a large biomass gasification device needs purification process treatment, and purification of a biomass gasification technology is divided into a dry type and a wet type, wherein the dry type is mainly used for removing dust and particles in the gas, and the wet type is mainly used for removing tar and a small amount of fine particles. At present, the gas purification technology is not mature, the gasification effect is not obvious, the tar removal difficulty is high, secondary pollution is easy to cause, and the purification cost is relatively high. The middle-size and small-size biomass gasification devices have high purification treatment cost and poor economical and practical properties; some furnace types adopt simple purification treatment, the secondary pollution of tar is serious, and the practicability is poor.

The downdraft gasification furnace is the currently most promising biomass gasification device, and the structure of the downdraft gasification furnace ensures that combustible gas must pass through a high-temperature oxidation area, thereby being beneficial to further cracking tar and obviously reducing the content of the tar in the fuel gas compared with the updraft gasification furnace. One type of downdraft gasification is an air draft mode, a gasification furnace operates under negative pressure, high-temperature fuel gas generated by gasification contains acidic substances, so that a fan is strongly corroded, and the fuel gas contains tar to easily cause pipeline blockage. One is to adopt a blast mode, the gasification furnace is operated under positive pressure, and a feed inlet needs to be sealed. The air blast type gasification furnace has simple structure and low investment without selecting a high-temperature fan; combustible gas has high calorific value and low tar content, and is more selected.

The downdraft fixed bed gasification process is mainly divided into 4 reaction zones from top to bottom: a drying zone, a pyrolysis zone, an oxidation zone, and a reduction zone.

(1) And a drying area: and (3) evaporating free water and combined water in the biomass, reducing the water content from 5-35% to below 5%, and controlling the temperature of a drying area to be 30-200 ℃.

(2) And a pyrolysis zone: the biomass is cracked under the condition of oxygen deficiency to generate a large amount of non-condensable combustible gases (CO and H)₂、CH₄Etc.) and condensable tar, the temperature range is 200-600 ℃.

(3) And an oxidation area: the gasifying agent is fed into the gasifying furnace at the part, and the biomass charcoal and the supplied oxygen are combusted to generate CO₂Partial cleavage of the resulting H₂And also reacts with oxygen to form water, both of which generate a large amount of heat if the oxygen is not supplied in sufficient quantities to completely convert the char to CO₂Then the carbon can also generate CO due to partial oxidation, and the temperature is 800-1200 ℃. Because the tar moves downward with the combustible gas and must pass through the high-temperature oxidation zone, secondary cracking of the tar occurs.

(4) And a reduction zone: under the environment of 800-1000 ℃ and oxygen deficiency, a plurality of endothermic reduction reactions can occur, and CO and H in combustible gas are increased₂、CH₄The content of (b) improves the gas-producing calorific value.

The raw material form of biomass gasification, including raw material shape and size (particle size), has an important influence on the biomass pyrolysis gasification process and product distribution. Researches find that the heat value of combustible gas is increased by times along with the increase of the bulk density of materials; the combustible gas production is also increased.

When the downdraft biomass gasifier operates, the material layer of the biomass moves downwards slowly along with the reaction so as to maintain the stable operation of the lower oxidation layer and the lower reduction layer. However, the material layer of the biomass in the actual operation of the existing downdraft gasifier does not have proper downward driving force, and the gasification agent air distribution ports are arranged in an oriented manner, so that the shapes of an oxidation layer and a reduction layer on the cross section of the furnace body are irregular, and the material layer moves downward inconsistently. The fuel accumulation is bound by the accumulation angle, so that the fuel in the furnace body is easy to generate bridging and burnthrough phenomena, the efficiency of the thermochemical reaction in the furnace is influenced, and the bed layer is easy to be locally overheated (temperature runaway), so that the fuel suitable for the existing gasification furnace is limited to large accumulation density, small granularity and small accumulation angle, the selection of raw materials is severely limited, and the operation cost of biomass gasification is increased.

In order to meet the requirements of users in different areas, expand the types of raw materials of the biomass gasification furnace and reduce the operation cost, the problems need to be solved seriously.

Disclosure of Invention

In order to solve the problems, the invention provides a constant-density biomass gasification furnace which can enable a fuel bed to stably descend and improve the compactness of a material bed, further eliminate the bridging phenomenon of the material bed and enable the reaction to be balanced.

The utility model provides a constant density biomass gasification stove, includes furnace body 1, and the top of furnace body 1 is equipped with movable bell 2, and inside is equipped with the grate 6 that divides furnace body 1 into fuel room and biochar room 3, simultaneously, the inner space in fuel room is from last to dividing into storage area 11 and reaction area 12 down, be provided with swager structure on the movable bell 2, wherein, swager structure includes drive arrangement 5 and material pressing disc 21, material pressing disc 21 is used for providing decurrent constant pressure to the biomass fuel in the storage area 11 under drive arrangement 5's drive.

Further, when the biomass fuel is a mixture formed by particles with different sizes, different types and different hardness, the material pressing disc 21 is used for providing constant pressure to the biomass fuel in a continuous pressurizing manner under the continuous driving of the driving device 5; when the biomass fuel is a single-variety granular material with uniform granules, the material pressing disc 21 is used for providing constant pressure for the biomass fuel in an intermittent beating mode under the intermittent driving of the driving device 5.

Further, the constant pressure is determined according to the current temperature and the expected temperature of the top of the gasification furnace.

Further, the driving device 5 is a pneumatic cylinder or a hydraulic cylinder.

Further, the constant-density biomass gasification furnace also comprises a nozzle 13 which penetrates through the grate 6 from the charcoal chamber 3 at the lower part of the gasification furnace and enters the reaction zone 12, wherein the nozzle 13 comprises an air inlet pipe 7, a self-rotating spray head 8, a baffle plate 9 and a nozzle shaft 10;

one end of the air inlet pipe 7 extends out of the charcoal chamber 3 to be connected with a gasifying agent, and the other end of the air inlet pipe is sleeved with the self-rotating spray head 8 and then penetrates through the grate 6 to enter the reaction zone 12; a nozzle shaft 10 is arranged inside the self-rotating nozzle 8, the self-rotating nozzle 8 and the nozzle shaft 10 are in radial non-contact sealing clearance fit, meanwhile, one end of the nozzle shaft 10 is embedded in the air inlet pipe 7, and the other end of the nozzle shaft is provided with a material baffle plate 9 for blocking the biomass fuel falling under pressure;

more than three spray pipes extend outwards in the circumferential direction of the outer side wall of the self-rotating spray head 8, wherein the spray pipes are distributed at equal intervals, and meanwhile, included angles between the air injection direction of each spray pipe and the axial direction of the self-rotating spray head 8 are the same and are smaller than 90 degrees, so that the self-rotating spray head 8 can spin under the lateral thrust of gasification agent jet flow sprayed by each spray pipe.

Further, the constant-density biomass gasification furnace also comprises an air inlet pipeline 4;

one end of the air inlet pipeline 4 is connected with the blower 43, and the other end is connected with the air inlet pipe 7, so that the gasification agent is input into the reaction zone 12.

Further, an electric igniter 41 and a pressure gauge 42 are arranged on the air inlet pipeline 4;

the pressure gauge 42 is used for measuring the pressure of a gasifying agent in the air inlet pipeline 4;

the electric igniter 41 is used for electrifying in the ignition stage of the gasification furnace, so that the gasification agent passing through the electric igniter 41 is heated, and then the heated gasification agent is sent into the reaction zone 12 through the nozzle 13.

Further, the rotation speed of the blower 43 is determined according to the deviation of the current temperature in the gasification furnace and the desired temperature.

Further, the bottom of the charcoal chamber 3 is provided with a charcoal discharging port 31, and the side wall is provided with a gas discharging pipeline 32.

Has the advantages that:

1. the invention provides a constant-density biomass gasification furnace, which has the advantages that a material pressing mechanism arranged on a movable furnace cover is used for providing a continuous top-down pressure or intermittent impact striking action for biomass fuel in a material storage area in the furnace, so that a fuel layer is stably descended, and the phenomenon of material layer bridging is eliminated; meanwhile, the material pressing mechanism can also improve the compactness of a material layer, balance the reaction and improve the tar cracking efficiency; in addition, the invention can easily realize automatic control of other operation processes except for filling biomass raw materials and discharging biochar, greatly reduce the operation cost, have better economic applicability and overcome the biggest obstacle of influencing the long-period stable operation of biomass gasification.

2. The invention provides a constant-density biomass gasification furnace, wherein a self-rotating nozzle is arranged in a reaction zone and communicated with an air inlet pipeline, so that a gasification agent uniformly enters the reaction zone from the center direction, an oxidation layer and a reduction layer are stable and balanced, the burn-through phenomenon is eliminated, and the gasification time period, the gasification efficiency and the tar cracking efficiency are improved; in addition, the invention can ensure that the material has enough detention time in the furnace by properly increasing the height of the furnace body, thereby ensuring that the gas and the material have longer contact time.

3. The invention provides a constant-density biomass gasification furnace, wherein the supply of a gasification agent is realized by the blast of an air blower connected with an air inlet pipeline, the downward movement of a biomass raw material is consistent with the flowing direction of fuel gas, dry distillation products of the raw material completely pass through an oxidation layer, most of the produced tar can be decomposed at high temperature, the content of the tar in the gas is relatively low, and water also reacts to generate combustible gas; therefore, the gasification furnace of the invention has the advantages of full combustion, no black smoke generation, no need of a dust removal device, flexible and convenient use, and achieves the purposes of reducing environmental pollution and protecting the health and ecological environment of people; meanwhile, the invention has the advantages of ingenious structure, small height change of the reaction layer and good working stability, can be used as a second addition point of the gasifying agent even if the cylinder is sealed and leaked in the working process, does not influence the reaction of the gasification furnace, and has lower requirements on the humidity and the granularity of the raw materials.

Drawings

FIG. 1 is a front view of a constant density biomass gasifier configuration of the present invention;

FIG. 2 is a side view of a constant density biomass gasifier configuration of the present invention;

FIG. 3 is an exploded isometric view of a nozzle of the present invention;

FIG. 4 is a cross-sectional view of a nozzle of the present invention;

FIG. 5 is a top view of a self-rotating showerhead of the present invention;

FIG. 6 is a schematic view of the connection of the nozzle to the air inlet duct in accordance with the present invention;

1-furnace body, 2-movable furnace cover, 3-biochar chamber, 4-air inlet pipeline, 5-driving device, 6-furnace grid, 7-air inlet pipe, 8-self-rotating spray head, 9-baffle plate, 10-nozzle shaft, 11-material storage area, 12-reaction area, 13-nozzle, 21-material pressing disk, 22-thermometer, 31-carbon discharge port, 32-gas discharge pipeline, 33-valve, 34-combustible gas burner, 35-water heater, 41-electric igniter, 42-pressure gauge and 43-blower.

Detailed Description

In order to make the technical solutions better understood by those skilled in the art, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application.

The invention aims to provide a constant-density biomass gasification furnace with a fuel layer moving downwards at constant density, a gasification agent automatically rotating a nozzle to feed air from the center of a furnace body, uniform gas distribution, continuous and stable reaction of each reaction layer and high gas production efficiency. The invention relates to a biomass gasification device, in particular to a small and medium-sized household biomass gasification device, wherein fuel factors and combustible gas purification factors are key factors for limiting the development of a biomass gasification technology. Firstly, the biomass filled in the gasification furnace is kept at constant density all the time and continuously participates in the reaction in the gasification reaction process through a certain mechanism in the gasification furnace, the density of the biomass in the gasification furnace is compressed to a proper range between the formed fuel and the loose fuel, and a uniform gasifying agent air distribution system is matched, so that long-period gasification reaction can be realized, large fuel cost does not need to be increased, and the biomass can be utilized nearby on site; secondly, the combustible gas produced by gasification is directly combusted, tar in the produced combustible gas is combusted in the gaseous state, the possibility of secondary pollution is avoided, and the combustible gas does not need cooling and purifying treatment, so that the overall thermal efficiency is high, and the device is a practical and feasible application mode of small and medium-sized household biomass gasification devices.

Specifically, as shown in fig. 1 and 2, a constant-density biomass gasification furnace includes a furnace body 1, a movable furnace cover 2 is arranged at the top of the furnace body 1, a furnace grate 6 is arranged inside the furnace body 1 and divides the furnace body 1 into a fuel chamber and a biochar chamber 3, meanwhile, the internal space of the fuel chamber is divided into a storage area 11 and a reaction area 12 from top to bottom, a material pressing mechanism is arranged on the movable furnace cover 2, wherein the material pressing mechanism includes a driving device 5 and a material pressing disc 21 for pressing biomass fuel in the gasification furnace, and the material pressing disc 21 is used for providing downward constant pressure to the biomass fuel in the storage area 11 under the driving of the driving device 5, so that the biomass keeps constant density.

It should be noted that biomass gasification is an incomplete controlled combustion. The combustible material is a biomass fuel, the combustion supporter is a biomass gasifying agent, the combustion supporter comprises oxygen (air, oxygen-enriched gas or pure oxygen and the like), steam or hydrogen and the like, the ignition temperature refers to the lowest temperature required by the oxidation reaction of different biomass fuels, and three elements (the combustible material, the combustion supporter and the ignition temperature) must exist simultaneously for the biomass gasification reaction to occur.

That is, from the perspective of a biomass gasifier system, in order to meet three necessary conditions of biomass gasification reaction, namely combustible substances, combustion-supporting substances and ignition temperature, firstly, the biomass fuel is passively moved downwards from natural accumulation to be driven to move downwards, the change is a brand new design concept of biomass gasification, and the aim of increasing the fuel accumulation density is changed into the aim of increasing the fuel accumulation density in the gasifier by pressurizing from the aim of extrusion or packaging pretreatment of the biomass fuel so as to ensure that the fuel accumulation density reaches a proper density range, and the heat value of the gas produced by the gasification reaction is also proper. Secondly, the material pressing mechanism in the gasification furnace not only increases the fuel stacking density, but also ensures the constant fuel distribution density in the gasification furnace, eliminates the phenomenon of uneven distribution such as aerial distribution in natural stacking, and can well realize the consistency of the biomass gasification process, thereby greatly expanding the types of biomass fuels, greatly reducing the operation cost, having better economic applicability, and overcoming the biggest obstacle of influencing the long-period stable operation of biomass gasification.

It should be noted that, for the material pressing mechanism of the gasification furnace of the present invention, the pressure of the material pressing mechanism can be determined according to different fuel types, so as to achieve economically suitable biomass fuel stacking density or ensure uniform fuel stacking. According to the design concept of the invention, for loose or soft and hard mixed fuels with different sizes and various varieties, a continuous pressurization mode is adopted to ensure that the density of the fuel is constant and the fuel uniformly moves downwards, so that reaction layers such as an oxidation layer and the like are uniformly distributed and well-arranged, and the gasification reaction is continuous and stable; for the granular materials with large stacking density and single variety and uniform particles, the intermittent striking mode is adopted, the bridging and burning-through phenomena in the gasification process are eliminated, and the continuous and stable gasification reaction is ensured.

In addition, the air cylinder or the hydraulic cylinder of the material pressing mechanism is specially designed, and a hard sealing structure is skillfully adopted to resist the influence of the high temperature of the gasification furnace on the sealing of the cylinder body. The reasonable leakage amount to the furnace is utilized to play the effects of lubrication and cooling, and the leaked air or water can also be used as a gasifying agent to participate in biomass gasification, thereby achieving two purposes. More importantly, the static seal is arranged between the material pressing mechanism and the movable furnace cover, the sealing performance is good, the combustible gas is not leaked, and the safety of the gasification furnace is high.

Furthermore, in order to meet the second necessary condition of biomass gasification, the air inlet mode of the gasification agent is a brand-new mode, and an automatic rotating nozzle is adopted. For medium and small biomass gasifiers, gasifying agents mainly comprise air, air and water vapor, two or more fixed nozzles are symmetrically arranged in the air blowing and air inlet mode of the existing downdraft biomass gasifier, and the existing downdraft biomass gasifier has the inherent defects that the gas is unevenly distributed, an oxidation layer is irregular, and each reaction layer is not clearly layered.

Specifically, as shown in fig. 1, the nozzle 13 passes through the grate 6 from the charcoal chamber 3 at the lower part of the gasification furnace into the middle part of the reaction zone 12; as shown in fig. 3 and 4, the nozzle 13 includes an air inlet pipe 7, a self-rotating nozzle 8, a striker plate 9, and a nozzle shaft 10.

One end of the air inlet pipe 7 extends out of the charcoal chamber 3 to be connected with a gasifying agent, and the other end of the air inlet pipe is sleeved with the self-rotating spray head 8 and then penetrates through the grate 6 to enter the reaction zone 12; a nozzle shaft 10 is arranged inside the self-rotating nozzle 8, the self-rotating nozzle 8 and the nozzle shaft 10 are in radial non-contact sealing clearance fit, meanwhile, one end of the nozzle shaft 10 is embedded in the air inlet pipe 7, and the other end of the nozzle shaft is provided with a material baffle plate 9 for blocking the biomass fuel falling under pressure; as shown in fig. 5, more than three nozzles extend outwards in the circumferential direction of the outer side wall of the self-rotating nozzle 8, wherein the nozzles are distributed at equal intervals, and the included angles between the air injection directions of the nozzles and the axial direction of the self-rotating nozzle 8 are the same and are all smaller than 90 °, so that the self-rotating nozzle 8 spins under the lateral thrust of the gasification agent jet ejected from the nozzles.

It should be noted that the basic principle of the rotation of the automatic rotating nozzle is that the nozzle automatically rotates by means of the side thrust of the air jet, that is, the recoil moment generated by the air jet overcomes the friction moment between the rotating nozzle and the shaft and then drives the nozzle to rotate, so that the nozzle sleeve has the rotation moment. The radial non-contact seal allows a very small leakage amount in the clearance, plays roles of lubricating and reducing friction resistance, and the leakage amount is mainly controlled by certain flow resistance caused by a seal gap. The flow resistance in the gap is influenced by the structural shape of the gap, the leakage and the flow state. Meanwhile, a material baffle plate is arranged above the automatic rotating nozzle and is used for preventing the fuel falling under pressure from blocking the nozzle.

That is, the gasifier body 1 of the invention includes the storage area 11 set up in its upper portion and the reaction area 12 set up below the storage area 11, the middle center of the reaction area 12 has air inlets of the self-rotating spray nozzle, and the air inlet is communicated with air inlet duct 4, make the gasifying agent enter the main body of the gasifier from the middle part of the reaction area 12, the spray nozzle rotates by oneself under the air intake drive, make the gasifying agent enter the reaction area along the circumferential direction evenly, has raised the gasification efficiency; in addition, the structure can improve the speed of air entering the gasification furnace, so that the air can reach the reaction zone as soon as possible, the reaction is balanced, and the tar cracking efficiency is improved.

It should be noted that the self-rotating nozzle of the present invention is disposed in a reaction zone of gasification of a gasification furnace, where the reaction zone generally includes an oxidation zone, a reduction zone, and a pyrolysis zone. The nozzle is positioned in an oxidation zone, a pyrolysis zone is arranged above the oxidation zone, and a reduction zone is arranged below the oxidation zone. The automatic rotary nozzle air inlet mode realizes the uniform circumferential air distribution, and under the condition that the gasification furnace barrel is fixed, the shape of the oxide layer can be changed by adjusting the air inlet pressure, so that the gasification strength can be adjusted. Because the air distribution mode is uniform, the shape of the oxidation layer is regular and clear, and the boundary between the oxidation layer and the reduction layer and the pyrolysis layer is clear, the long-period stable operation of the gasification process in the biomass gasification furnace can be ensured.

Further, as shown in fig. 6, a blower 43, a pressure gauge 42 and an electric ignition device 41 are connected in series to an air inlet duct connected to the automatic rotary nozzle, and at the stage of the ignition of the gasification furnace, the ignition device is energized, and the intake air is heated by the electric ignition device. The hot air is distributed to the biomass fuel through the automatic rotating nozzle, and the gasification reaction starts. The ignition time is generally not more than 3 minutes, after the stable oxidation reaction layer is established, the electric ignition device is powered off, and the gasification reaction of the gasification furnace enters a normal operation state. Optionally, the ignition device 41 and the air inlet duct 4 are of an integrated series structure.

In addition, the blower 43 is externally arranged, and simultaneously provides air inlet for the gasification furnace and driving gas for the cylinder; the air inlet pipeline 4 is provided with an air inlet pipe and an electric ignition device which are connected with the blower 43; the downward movement of the biomass raw material is consistent with the flowing direction of fuel gas, dry distillation products of the raw material completely pass through the oxidation layer, most of generated tar can be decomposed at high temperature, the tar content in the gas is relatively low, and water also reacts to generate combustible gas.

Furthermore, the ignition temperature is one of three requirements of combustion, and the heat preservation of the gasification furnace is also necessary. Therefore, the gasifier of the invention adopts a three-layer structure for heat preservation, the innermost fire-resistant layer and the middle perlite are coated, and a layer of heat preservation paint is coated outside the gasifier body, so that the surface temperature of the gasifier can be kept below 50 ℃.

The biomass gasification-combustion system of the constant-density biomass gasification furnace utilizes biomass fuel in a mode of direct combustion after gasification, and biomass combustible gas is used in a combustion part, so that the biomass gasification-combustion system can be fully combusted, black smoke can not be generated, a dust removal device is not needed, the load adjustment range is wide, and the biomass gasification-combustion system is flexible and convenient to use. The biomass is directly combusted by a boiler, the thermal efficiency of the fuel is only 15%, the biomass is combusted after being gasified, and the utilization efficiency of biomass resources can be improved to more than 70% because the biomass can be fully gasified. The efficient and clean combustion is completely realized, the problems of high energy consumption and high environmental pollution in rural life are fundamentally solved, and the aims of reducing the environmental pollution and protecting the health and ecological environment of people are fulfilled.

Meanwhile, the control system of the constant-density biomass gasification furnace aims at maximizing the conversion efficiency of biomass energy and improving and ensuring the quality of combustible gas. Factors influencing the conversion efficiency of the gasification furnace are many, but mainly depend on the temperature intervals of 4 treatment processes of the gasification furnace; the quality of the combustible gas generated by the gasification furnace is mainly reflected in the high and low oxygen content of the combustible gas. Therefore, the problems to be solved by biomass gasifier system control mainly lie in how to stabilize the temperature in the furnace in an optimal interval and how to reduce the oxygen content of the final combustible gas.

Therefore, in order to stabilize the temperature of the top of the gasification furnace and reduce the oxygen content of the combustible gas at the outlet, the pressure of the biomass fuel pressing mechanism and the feeding amount of the air are respectively controlled. Predicting the optimal pressure of the biomass material pressing mechanism according to the current temperature and the temperature set value of the top of the gasification furnace; the blanking speed of the material pressing mechanism is controlled in a following mode, and the purposes of accurate blanking and stable furnace temperature are achieved. The air input quantity is used as a main adjusting means, and because the air input quantity not only influences the oxygen content of the combustible gas, but also influences the temperature of the gasification furnace, the optimal rotating speed of the air blower is calculated according to the furnace temperature deviation in the furnace; and carrying out follow-up control on the speed of the blower according to the calculated optimal rotating speed to ensure the rotating speed of the blower.

In summary, in the present invention, the movable furnace cover 2 is disposed above the gasifier body, and a material pressing disk 21 is disposed in the middle of the movable furnace cover, so that the material pressing disk 21 applies downward pressure to biomass raw materials in the gasifier, thereby eliminating possible bridging phenomenon while compacting the raw materials, and keeping the biomass moving downward at constant density to participate in gasification reaction. In addition, a grate 6 is arranged between the gasification furnace body 1 and the biochar chamber 3, the biochar which is finished by reaction enters the biochar chamber 3 through the grate 6, and the unreacted biomass continues to react in the reaction zone 12. A closable charcoal discharge port 31 is provided at the lower portion of the charcoal chamber 3, and is responsible for discharging the accumulated charcoal ashes. Besides, the biochar chamber 3 is also provided with a fuel gas discharge pipeline 32 connected with the biochar chamber, and the fuel gas discharge pipeline is responsible for discharging biomass fuel gas generated by reaction.

It should be noted that the air inlet pipeline 4 and the furnace wall of the gasification furnace body 1 are of an integrated structure, so that the air tightness between the air inlet pipeline 4 and the gasification furnace body 1 is ensured while the processing is convenient. In addition, the electric igniter is arranged on the air inlet pipeline, the gasifier is heated through the electric igniter to quickly ignite the air inlet, and the reliability of ignition starting of the gasifier is guaranteed. Optionally, the air inlet duct 4 is formed by two air inlet branch ducts.

When the gasification furnace is used, firstly, materials are filled into the gasification furnace main body, and drying treatment is carried out on the materials in the material storage area 11 in the gasification furnace main body; then, the biomass after drying treatment enters the reaction zone 12 under the compression of the pressing mechanism, so that the preparation of the biomass is completed; then, the starting of the pyrolysis reaction is controlled by electrifying and heating an electric igniter in the air inlet pipeline, and the pyrolysis reaction is carried out by matching with the air entering the reaction zone 12 from the nozzle 13 to generate biomass gas; finally, the generated fuel gas is guided out of the gasifier body by the fuel gas discharge duct 32 and used. During this reaction, the char generated by the reaction of the biomass in the gasifier body can be removed periodically through the char outlet 31.

The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof, and it will be understood by those skilled in the art that various changes and modifications may be made herein without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. The utility model provides a constant density biomass gasification stove, includes furnace body (1), and the top of furnace body (1) is equipped with movable furnace lid (2), and inside is equipped with grate (6) of dividing furnace body (1) into fuel room and biochar room (3), simultaneously, the inner space in fuel room is from last to dividing into storage area (11) and reaction zone (12) down, its characterized in that, be provided with swager structure on the movable furnace lid (2), wherein, swager structure includes drive arrangement (5) and swager disc (21), swager disc (21) are used for under the drive of drive arrangement (5), provide decurrent constant pressure to the biomass fuel in storage area (11).

2. The constant-density biomass gasification furnace according to claim 1, wherein when the biomass fuel is a mixture of particles with different sizes, different types and different hardness, the material pressing disc (21) is used for providing constant pressure to the biomass fuel in a continuous pressurizing manner under the continuous driving of the driving device (5); when the biomass fuel is a single-variety granular material with uniform granules, the material pressing disc (21) is used for providing constant pressure for the biomass fuel in an intermittent beating mode under the intermittent driving of the driving device (5).

3. A constant density biomass gasifier according to claim 1, characterized in that the magnitude of said constant pressure is determined according to the current temperature and the desired temperature of the gasifier roof.

4. The gasifier for biomass of constant density according to claim 1, characterized in that the driving means (5) is a pneumatic or hydraulic cylinder.

5. A constant density biomass gasifier according to claim 1, further comprising a nozzle (13) passing through the grate (6) from the charcoal chamber (3) in the lower part of the gasifier into the reaction zone (12), wherein the nozzle (13) comprises an air inlet pipe (7), a self-rotating nozzle (8), a baffle plate (9) and a nozzle shaft (10);

one end of the air inlet pipe (7) extends out of the biochar chamber (3) to be connected with a gasifying agent, and the other end of the air inlet pipe is sleeved with the self-rotating spray head (8) and then penetrates through the grate (6) to enter the reaction zone (12); a nozzle shaft (10) is arranged in the self-rotating nozzle (8), the self-rotating nozzle (8) and the nozzle shaft (10) are in radial non-contact sealing clearance fit, meanwhile, one end of the nozzle shaft (10) is embedded in the air inlet pipe (7), and the other end of the nozzle shaft is provided with a baffle plate (9) used for blocking the biomass fuel falling under pressure;

more than three spray pipes extend outwards in the circumferential direction of the outer side wall of the self-rotating spray head (8), wherein the spray pipes are distributed at equal intervals, and meanwhile, included angles between the air injection direction of each spray pipe and the axial direction of the self-rotating spray head (8) are the same and smaller than 90 degrees, so that the self-rotating spray head (8) can spin under the lateral thrust of gasification agent jet flow sprayed by each spray pipe.

6. A gasifier for biomass with constant density according to claim 5, characterized by further comprising an air inlet duct (4);

one end of the air inlet pipeline (4) is connected with the blower (43), and the other end is connected with the air inlet pipe (7), so that the gasification agent is input into the reaction zone (12).

7. The constant-density biomass gasification furnace according to claim 6, wherein the air inlet pipe (4) is further provided with an electric igniter (41) and a pressure gauge (42);

the pressure gauge (42) is used for measuring the pressure of a gasifying agent in the air inlet pipeline (4);

the electric igniter (41) is used for electrifying in the ignition stage of the gasification furnace, so that the gasification agent passing through the electric igniter (41) is heated, and the heated gasification agent is sent into the reaction zone (12) through the nozzle (13).

8. A gasifier for biomass according to claim 6, characterized in that the speed of rotation of the blower (43) is determined according to the deviation of the current temperature in the gasifier from the desired temperature.

9. The constant-density biomass gasification furnace according to claim 1, wherein the charcoal chamber (3) is provided with a carbon discharge port (31) at the bottom and a gas discharge pipe (32) at the side wall.