CN201567310U - A biomass spiral pyrolysis device - Google Patents

Abstract

The utility model relates to a biomass pyrolysis device. The device consists of a feeding system, a pyrolysis reactor with an external heating system and a heat preservation system, and a pyrolysis product collection system. Shaped cylinder, through the middle holes of the two covers, a rotating shaft that can rotate relative to the cylinder is installed. A helical blade as a screw propeller is arranged on the rotating shaft in the cavity of the cylinder. The gap between the top of the blade and the inner wall of the cylinder is Cooperate, the extension end of the rotating shaft outside the cylinder is connected with a frequency conversion motor; the side wall of the circular cylinder is respectively provided with a biomass feed pipe and a pyrolysis product outlet pipe, the feed pipe is connected to the feed bin, and the outlet pipe is connected to the into the coke collection tank, and the collection tank is connected to the condenser, the bio-oil collection tank, and the exhaust gas discharge pipe in sequence through the gas outlet pipeline. The utility model can precisely control the residence time of the biomass, control the temperature of the pyrolysis process in different regions, make the components of the bio-oil controllable, and easily refine and extract chemicals.

Description

A biomass spiral pyrolysis device

technical field

The utility model relates to a biomass pyrolysis device.

Background technique

At present, all countries in the world, especially developed countries, are devoting themselves to the development of highly efficient and non-polluting biomass energy utilization technologies to protect their own mineral energy resources in order to provide a fundamental guarantee for the sustainable development of the national economy. Biomass pyrolysis means that biomass is heated to more than 500°C in the absence of oxidants (air, oxygen, water vapor, etc.) or only limited oxygen is provided, and biomass macromolecules (lignin, Cellulose and hemicellulose) are decomposed into smaller molecular fuel substances (solid carbon, combustible gas, bio-oil) thermochemical conversion technology method. The fuel energy conversion rate of biomass pyrolysis can reach 95.5%, which can maximize the conversion of biomass energy into energy products and make the best use of it. Pyrolysis is also an essential initial stage of combustion and gasification

Analyzing it from the perspective of chemical reaction, biomass undergoes complex thermochemical reactions during the pyrolysis process, including reactions such as molecular bond breaking, isomerization, and small molecule polymerization. The main components of wood, forestry residues and agricultural crop residues are cellulose, hemicellulose and lignin. The results of thermogravimetric analysis showed that cellulose began to pyrolyze at 52°C, and as the temperature increased, the pyrolysis reaction speed increased, and at 350-370°C, it decomposed into low-molecular products. According to the temperature change and product formation during the pyrolysis process, it can be divided into drying stage, pre-pyrolysis stage, solid decomposition stage and calcination stage. In the drying stage (temperature is 120-150°C), the moisture in the biomass is evaporated, and the chemical composition of the material is almost unchanged. In the pre-pyrolysis stage (temperature is 150-275°C), the thermal reaction of the material is relatively obvious, the chemical composition begins to change, and the unstable components in the biomass such as hemicellulose decompose into carbon dioxide, carbon monoxide and a small amount of acetic acid and other substances. The above two stages are all endothermic reaction stages. In the solid decomposition stage (temperature is 275-475°C), the main stage of pyrolysis, various complex physical and chemical reactions occur in the material, and a large number of decomposition products are produced. The generated liquid products contain acetic acid, wood tar and methanol (precipitated during cooling); the gas products include CO2, CO, CH4, H2, etc., and the content of combustible components increases. This stage releases a lot of heat. In the calcination stage (the temperature is 450-500°C), the biomass relies on the heat supplied from the outside to burn the charcoal, which reduces the volatile matter in the charcoal and increases the fixed carbon content, which is the exothermic stage. In fact, it is difficult to clearly define the boundaries of the above four stages, and the reaction processes of each stage will cross each other.

From the perspective of the heating rate of the biomass and the time taken to complete the reaction, the biomass pyrolysis process can basically be divided into two types: one is slow pyrolysis, and the other is fast pyrolysis. In fast pyrolysis, when the reaction time is very short (<0.5s), it is also called flash pyrolysis. According to the process operating conditions, the biomass pyrolysis process can be divided into three types: slow, fast and reactive pyrolysis. In the slow pyrolysis process, it can be divided into carbonization and conventional pyrolysis.

Slow pyrolysis (also known as dry distillation process, traditional pyrolysis) process has a history of thousands of years. It is a carbonization process for the purpose of producing charcoal. ~750°C, and the temperature of high-temperature dry distillation is 900-1100°C. Put the wood in the kiln and heat it in the absence of air, and you can get a charcoal output accounting for 30% to 35% of the raw material mass.

Fast pyrolysis is to place finely ground biomass raw materials in a fast pyrolysis device, and strictly control the heating rate (generally approximately 10-200°C/s) and reaction temperature (controlled at about 500°C). In the case of oxygen, it is rapidly heated to a higher temperature, thereby initiating the decomposition of macromolecules, producing small molecule gases and condensable volatiles and a small amount of coke products. The condensable volatile matter is rapidly cooled into a flowable liquid and becomes bio-oil or tar, and its proportion can generally reach 40% to 60% of the raw material mass.

Compared with slow pyrolysis, the heat transfer reaction process of fast pyrolysis occurs in a very short time, and the strong thermal effect directly produces pyrolysis products, which are then rapidly quenched, usually to below 350°C within 0.5s, the maximum Liquid product (oil) is increased to a minimum.

Generally speaking, the main factors affecting pyrolysis include chemical and physical aspects. Chemical factors include a series of complex primary reactions and secondary reactions; physical factors are mainly heat transfer, mass transfer and physical properties of raw materials during the reaction process. The specific operating conditions are: temperature, material characteristics, catalyst, residence time, pressure and heating rate.

In the process of biomass pyrolysis, temperature is a very important factor, which has a great influence on the distribution, composition, yield and calorific value of pyrolysis products. The proportion of gas, oil and charcoal in the final product of biomass pyrolysis varies greatly with the reaction temperature and heating speed. Generally speaking, low-temperature, long-term retention slow pyrolysis is mainly used to maximize the yield of char, and its mass yield and energy yield reach 30% and 50% (mass fraction), respectively. For conventional pyrolysis at a temperature lower than 600°C, medium reaction rate is adopted, and the yields of bio-oil, non-condensable gas and charcoal are basically equal; flash pyrolysis temperature is in the range of 500-650°C, which is mainly used to increase the yield of bio-oil , the bio-oil yield can reach 80% (mass fraction); the same flash pyrolysis, if the temperature is higher than 700 ° C, is mainly used to produce gaseous products at a very high reaction rate and a very short gas phase residence period. Its yield can reach 80% (mass fraction). When the heating rate is extremely fast, hemicellulose and cellulose hardly generate char.

Residence time In biomass pyrolysis reaction, there are solid phase residence time and gas phase residence time. The shorter the solid phase residence time, the smaller the proportion of pyrolyzed solid products, the larger the total product amount, and the more complete the pyrolysis. Under the conditions of a given temperature and heating rate, the shorter the solid phase residence time, the less solid phase products and the greater the amount of gas phase products in the converted products of the reaction. The gas phase residence time generally does not affect the process of the primary cracking reaction of biomass, but only affects the process of the secondary cracking reaction of the bio-oil in the liquid product. When the primary products of biomass pyrolysis products enter the gas phase surrounding biomass particles, the bio-oil will undergo further cracking reactions. In the hot reactor, the longer the gas phase residence time, the secondary cracking of bio-oil will occur. The more serious, the more secondary cracking reactions, releasing H2, CH4, CO, etc., resulting in a rapid decrease in liquid products and an increase in gas products. Therefore, in order to obtain the maximum yield of bio-oil, the gas phase residence period should be shortened so that the volatile products can leave the reactor quickly and the time for the secondary cracking of tar should be reduced.

The conventional pyrolysis method in the prior art is to place the biomass raw material in an existing pyrolysis device, such as fluidized bed pyrolysis. This kind of pyrolysis is usually under the conditions of moderate temperature below 600°C and moderate reaction rate (0.1-1°C/s), after several hours of pyrolysis, biomass accounting for 20%-25% of the raw material mass is obtained Charcoal and 30% to 40% bio-oil. In the fluidized bed reactor, after the biomass particles are heated to a suitable temperature, the solid particles are in a fluidized state under the drive of nitrogen, and the biomass completes the pyrolysis process within a residence time of 1-3 seconds, and then the pyrolysis process is completed. The organic matter and coke enter the cyclone separator, the coke is separated and collected for reuse, and the gas enters the condenser, and the bio-oil with complex composition is obtained after condensation. Since the residence time of biomass particles in the fluidized bed reactor cannot be accurately controlled during the pyrolysis process, and the pyrolysis temperature is also difficult to control, the composition of the obtained pyrolysis product is complex, and the controllable composition of the pyrolysis product, namely bio-oil, cannot be realized , not easily refined to extract chemicals. That is to say, the bio-oil composition and concentration obtained by the existing pyrolysis technology are random. Therefore, the obtained bio-oil can only be used as a low-grade fuel, and the added value is relatively low, which limits the promotion of pyrolysis technology.

Contents of the invention

The purpose of the utility model is to provide a spiral pyrolysis device that can accurately control the pyrolysis time and temperature of biomass particles, thereby effectively controlling the composition and concentration of bio-oil, so that the biomass pyrolysis technology can be further promoted.

The biomass spiral pyrolysis device of the utility model is composed of a feeding system, a pyrolysis reactor and a pyrolysis product collection system. The pyrolysis reactor is equipped with an external heating system and a heat preservation system. It is characterized in that the pyrolysis reaction The device is a spiral pyrolysis reactor, which includes a circular cylinder with both ends sealed by covers, and a rotating shaft that can rotate relative to the circular cylinder is installed through the middle holes of the two covers. The rotating shaft is provided with a helical blade as a screw propeller, and the top of the helical blade is in clearance with the inner wall of the circular cylinder, and the extension end of the rotating shaft outside the circular cylinder is connected with a frequency conversion motor; The feed pipe for biomass and the outlet pipe for pyrolysis products are respectively provided. The feed pipe is connected with the feed bin, and the outlet pipe is vertically connected to the coke collection tank of the pyrolysis product collection system. In the coke collection tank A gas outlet pipe is arranged on the side wall, and the gas outlet pipe communicates with the condenser, the bio-oil collection tank and the tail gas discharge pipe in sequence. The pitch l of the screw propeller installed on the rotating shaft satisfies the formula $t=\frac{L}{l\&CenterDot;\frac{\mathrm{no}}{60}},$ Among them, L is the axial length of the screw propeller, t is the residence time of the set biomass in the screw reactor, usually t=1-3 seconds, n is the rotation speed of the rotating shaft, usually 100-400 rpm.

In the above device, the external heating system of the pyrolysis reactor is an integral or separated electric heating plate with adjustable power, and each electric heating plate is provided with a thermocouple for temperature measurement.

In the above device, the helical blade as the helical propeller, the inner wall of the circular cylinder and the surface of the rotating shaft are all made of corrosion-resistant materials to prevent the quality of the bio-oil from being affected by corrosion.

The process of using the spiral pyrolysis device of the present invention to pyrolyze biomass includes first starting the external heating system to stabilize the temperature of the reaction zone in the spiral pyrolysis reactor at 500-550°C; It is transported into the spiral pyrolysis reactor through the inlet pipe, which is characterized in that the variable frequency motor is started at the same time, and according to the set residence time t of the biomass in the spiral pyrolysis reactor, as well as the axial length L and pitch of the screw propeller l, using the formula $t=\frac{L}{l\&CenterDot;\frac{\mathrm{no}}{60}},$ Determine the rotational speed n of the variable frequency motor, usually in the range of 100-400 rpm; then start the pyrolysis product collection system to obtain liquid bio-oil and other pyrolysis products. The biomass particle raw material is pulverized biomass particles with a particle size of 20-200 mesh.

In actual operation, according to the quality analysis of the obtained bio-oil, the speed of the variable frequency motor can be adjusted appropriately, that is, the residence time of the biomass in the screw reactor can be adjusted to obtain the appropriate quality and yield of bio-oil.

The "starting the external heating system to stabilize the temperature of the reaction zone in the spiral pyrolysis reactor at 500-550°C" can be divided into different temperature zones in the length direction of the spiral reactor by controlling different electric heating plates, from 500°C is gradually raised to 550°C along the direction of biomass movement, which is more beneficial to improve the yield and oil quality of bio-oil.

Using the spiral pyrolysis device of the utility model to pyrolyze biomass has two main advantages compared with the prior art:

(1) The residence time of biomass in the reactor can be precisely controlled:

The residence time of biomass in the fluidized bed reactor is generally related to the amount of feed and the effective volume of the fluidized bed reactor. It is an average residence time. Due to the complex movement state of the mixed material in the fluidized bed, there is often a short circuit , back-mixing and dead angle phenomena, and due to the continuous weight loss of biomass particles during the pyrolysis process, the residence time of biomass individuals varies greatly. Therefore, the average residence time cannot accurately reflect the individual residence time. This spiral pyrolysis reactor is completely different. As long as the screw pitch is designed reasonably to avoid material slipping and back spraying, the individual residence time of biomass is also the average residence time.

Theoretically speaking, the residence time of biomass particles in the reactor is different, that is, the reaction time is different, and the composition of the pyrolysis products will be different, that is, the composition and concentration of bio-oil will change. In the spiral pyrolysis device of the present utility model, since the rotational speed of the rotating shaft can be adjusted by the frequency conversion motor, the advancing speed of the biomass particles, that is, the residence time of the biomass particles in the reactor can be precisely controlled (accurate to 0.1 second) ), so the composition and concentration of the bio-oil obtained by pyrolysis are relatively consistent, which has great advantages for further optimization of the product.

(2) The temperature of the pyrolysis process can be controlled in different regions:

According to the principle of pyrolysis, pyrolysis of biomass in different temperature zones can improve the yield and oil quality of bio-oil. Because in the process of biomass pyrolysis, temperature is a very important factor, which has a great influence on the distribution, composition, yield and calorific value of pyrolysis products. The proportion of gas, oil and charcoal in the final product of biomass pyrolysis varies greatly with the reaction temperature and heating speed. Generally speaking, low-temperature, long-term retention slow pyrolysis is mainly used to maximize the yield of char, and its mass yield and energy yield reach 30% and 50% (mass fraction), respectively. If the conventional pyrolysis temperature is less than 600°C and the medium reaction rate is adopted, the yields of bio-oil, non-condensable gas and charcoal are basically equal; if the flash pyrolysis temperature is in the range of 500-650°C, the biological The yield of oil, the bio-oil yield can be as high as 80% (mass fraction); the same flash pyrolysis, if the temperature is higher than 700 ° C, at a very high reaction rate and a very short gas phase residence period, the gas product will increase Output, its productive rate can reach 80% (mass fraction).

Although the fluidized bed pyrolysis reactor can be heated by electricity, it can also be controlled by thermocouple partitions, but because the material in the fluidized bed is in a fluidized state, back-mixing often occurs, and the heat is convectively transferred, making the temperature in the reactor More uniform distribution, it is difficult to control the temperature partition by thermocouple. There is no fluidization and back-mixing phenomenon in the spiral pyrolysis reactor, and the heat transfer is entirely by heat conduction, so the heat transfer rate is small, which is convenient for temperature control, which is conducive to product optimization.

The utility model directly pyrolyzes biomass to generate bio-oil through a spiral pyrolysis device, which is not only convenient for storage and transportation, but also has controllable components of bio-oil, and is easy to refine and extract chemicals.

Below by embodiment and accompanying drawing, the utility model will be further described.

Description of drawings

Fig. 1 is a schematic diagram of an embodiment of a spiral pyrolysis device of the present invention.

Detailed ways

Example 1

Referring to Fig. 1, one end of the cylinder body 5 of the cylindrical reactor is flange-shaped, and the two ends of the outer sleeve 6, which plays a role in heat preservation, are also flange-shaped, and the cylinder body 5 and the outer sleeve 6 are sheathed on each other. Together, plus the left and right end covers 4, 11 and the threaded connector structure or a whole, there is a large enough gap between the inner wall of the outer sleeve 6 and the outer wall of the cylinder 5, and four electric heating plates 8 are arranged in this gap , and surround the outer wall of the cylinder 5. The electric heating plate is a 4×1KW electric heating plate with adjustable power, which is controlled by four thermocouples 9 respectively. After reaching the set temperature, the heating power is automatically reduced, so the reaction temperature in the reactor can be effectively controlled at a certain temperature. range (500-550°C). Four thermocouples independently control four heating plates, so that there are four different temperature zones in the spiral reactor, so as to meet the needs of different temperatures in the length direction of the circular cylinder. One end of the thermocouple 9 is in contact with the outer wall of the cylinder 5, and the other end passes through the outer sleeve to reach the outer space, and is connected to a meter for convenient observation. The biomass feed pipe 7 is arranged above the left end, its axis is perpendicular to the cylinder 5 , and the outlet pipe 12 is arranged below the right end, its axis is also perpendicular to the cylinder 5 . In the axis holes of the left and right end covers 4, 11, a rotating shaft 3 is supported by a bearing, and a high temperature resistant sealing ring 1 is arranged for sealing. The variable frequency motor 2 is connected with the left end of the rotating shaft 3, so that the rotating shaft 3 can rotate together with the motor main shaft, and the rotating speed of the variable frequency motor is adjustable in the range of 100-400 rpm. A helical blade 10 as a screw propeller is installed on the part of the rotating shaft that is contained in the inner cavity of the cylinder, and the tip of the helical blade is in clearance fit with the inner wall surface of the cylinder. In this embodiment, the internal diameter of the cylinder is selected to be 52 millimeters, the outer diameter of the blade is 50 millimeters, and the diameter of the rotating shaft is 30 millimeters; the length of the screw propulsion part is 240 millimeters, and the residence time of biomass is set within 1-3 seconds, calculated according to the above-mentioned relevant formula Obtaining pitch is 16-48 millimeter, and present embodiment selects pitch to be 30 millimeters, and has selected the common helix angle of screw propeller 15 ° for use. The outlet pipe 12 leads into the coke collection tank 13 below, and then is connected as a whole with the condenser 15, the bio-oil collection tank 16 and the tail gas discharge pipe 17 by the gas outlet pipe 14.

In this embodiment, the helical blades as the helical propulsion device, the cylindrical reactor and the rotating shaft are all made of stainless steel. The frequency conversion motor is purchased from the market, the model is CHF100-1R5G-4 (INVT ELECTRIC CO.LTD)

Next, use the above-mentioned device for practical application and test relevant data.

The biomass raw material is sawdust, and the particle size after crushing is about 40-80 mesh. First, heat the electric heating plate to the set temperature: the four thermocouples are respectively set to 500°C, 520°C, 530°C, and 550°C from left to right, and the actual temperature in the reactor will vary slightly. Then feed the biomass raw material from the feeder to the feed port of the spiral pyrolysis reactor, start the frequency conversion motor at the same time, and open the condenser and tail gas discharge system. Adjust the rotating shaft to rotate at a rotational speed of 300 rpm, that is, the residence time of the biomass raw material in the reactor is 1.6 seconds. Biomass pyrolyzes rapidly in the reactor, and its products are organic molecular gas and solid coke. The screw propulsion device pushes the coke out through the outlet pipe into the coke collection tank, and the gas passes through the outlet pipe and is released from the coke collection tank. The gas outlet enters the condenser, and the bio-oil obtained after condensation enters the bio-oil collection tank, and the rest of the tail gas is discharged from the tail gas discharge pipe 5 .

Concrete reaction conditions and relevant detection data are as follows:

The incoming flow rate of the biomass feedstock was 18 kg/h, resulting in a bio-oil production of 8.6 kg/h.

Preliminary detection and analysis show that the water content of the obtained bio-oil is less than 30%, and the high calorific value is 21MJ/kg.

Compared with the bio-oil obtained by fluidized bed pyrolysis in the prior art, the content of phenols in the bio-oil obtained by spiral pyrolysis is about 40% higher than that of fluidized bed pyrolysis, and the organic matter with a content greater than 1% reaches 22 kinds, There are only 10-15 kinds of common fluidized beds.

Claims (3)

1. biomass screw pyrolysis installation, by charging system, pyrolysis reactor and pyrolysis product gathering system constitute, this pyrolysis reactor has outer heating system and heat-insulation system, it is characterized in that, described pyrolysis reactor is a spiral pyrolysis reactor, it comprises the circular cylinder body of two ends by the lid sealing, mesopore by two lids supports a rotation axis that can rotate with respect to circular cylinder body is installed, be provided with screw-blade on the rotation axis in cylinder chamber as spiral propeller, this screw-blade top and circular cylinder body inner-wall surface running fit, the external part of rotation axis outside circular cylinder body is connected with variable-frequency motor; On the circular cylinder body sidewall, be respectively equipped with the outlet pipe of biomass feed-pipe and pyrolysis product, its feed-pipe is communicated with feeding warehouse, its outlet pipe vertically is passed in the coke holding tank of pyrolysis product gathering system, be provided with an outlet pipe on coke holding tank sidewall, this outlet pipe is communicated with condenser, bio oil holding tank, tail gas discharging pipe successively.

2. biomass screw pyrolysis installation as claimed in claim 1 is characterized in that, described outer heating system is an electric heating panel whole or isolating power-adjustable, and every electric heating panel is provided with thermometric thermopair.

3. biomass screw pyrolysis installation as claimed in claim 1 is characterized in that, the described pitch 1 that is installed in the spiral propeller on the rotation axis satisfies formula

Wherein, L is the axial length of spiral propeller, and biomass the residence time helical reactors in of t for setting, n is the velocity of rotation of rotation axis.

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