Biomass pyrolysis system with high energy utilization rate and cyclic utilization of CO2 as carrier gas

Abstract

The invention discloses a biomass pyrolysis system with high energy utilization rate and cyclic utilization of CO2 as carrier gas. The biomass pyrolysis system comprises a raw material box, a pyrolysis furnace, a heat storage pipe, a pyrolysis pipe, a flowmeter, a pressure gauge, a CO2 gas tank, a tail gas absorption device, an oxygen absorption device, a gas pump, a condensation product collection device, a water tank, a combustion chamber and an oxygen bottle, pyrolysis gas is directly combusted, an internal gas path is kept closed, continuous flowing of the internal gas path is kept through a gas pump, cyclic utilization of CO2 is achieved, meanwhile, high heat energy carried by the pyrolysis gas is utilized, and sensible heat loss caused by condensation of the pyrolysis gas is avoided; the system is simple and low in investment; the smoke exhaust temperature is low, and the smoke sensible heat utilization rate is high.

Description

Technical Field

[0001] The present invention belongs to the technical field of biomass pyrolysis, and particularly relates to a biomass pyrolysis system with high energy utilization rate and recycling of CO2 as a carrier gas. Background Art

[0002] Biomass pyrolysis can efficiently utilize biomass energy through biomass energy thermal conversion technology to produce various clean energy and chemical products. At present, countries around the world, especially developed countries, are committed to developing efficient and pollution-free biomass energy utilization technologies to provide a fundamental guarantee for the sustainable development of the national economy.

[0003] Biomass pyrolysis refers to a thermochemical conversion technology method in which biomass macromolecular substances (lignin, cellulose, and hemicellulose) are decomposed into smaller molecules through thermochemical reactions under the condition of no oxygen or only limited oxygen. At present, the pyrolysis gas generated by the biomass carbonization system is first condensed and purified to obtain combustible gas. Part of the combustible gas is burned for its own use, and part of it is burned and discharged, bringing the following problems: a large amount of heat energy is wasted during the condensation process of the pyrolysis gas, and the energy utilization rate is low; the pyrolysis carrier gas only ensures an oxygen-free pyrolysis environment but cannot be recycled, resulting in high investment and large maintenance workload. Summary of the Invention

[0004] In view of the deficiencies of the prior art, the present invention provides a biomass pyrolysis system with high energy utilization rate and recycling of CO2 as a carrier gas, which makes full use of the heat generated during the pyrolysis process to realize the recycling of flue gas and heat.

[0005] The technical solution of the present invention is as follows:

[0006] A biomass pyrolysis system with high energy utilization rate and recycling of CO2 as a carrier gas includes a raw material tank, a pyrolysis carbonization furnace, heat storage pipes, pyrolysis pipes, flow meters, pressure gauges, CO2 gas cylinders, tail gas absorption devices, oxygen absorption devices, air pumps, condensate collection devices, water tanks, combustion chambers, and oxygen cylinders;

[0007] The raw material tank is connected to the pyrolysis pipe through a conveyor;

[0008] The pyrolysis pipe is arranged in the pyrolysis carbonization furnace. A combustion chamber and heat storage pipes are also arranged in the pyrolysis carbonization furnace. The heat storage pipes are arranged outside the pyrolysis pipe. Two combustion chambers are arranged at both ends of the pyrolysis carbonization furnace, and both ends of the heat storage pipes enter the interior of the combustion chambers;

[0009] The bottom of the combustion chamber is respectively connected to an oxygen cylinder and a pyrolysis tube. The top of the combustion chamber is connected to an outlet pipe. The other end of the outlet pipe enters the inside of the water tank and penetrates through the water tank, and then is successively connected to an air pump, an oxygen absorption device, a tail gas absorption device, a pressure gauge, a flow meter, and a pyrolysis tube. A CO2 gas cylinder is also connected to the pipeline between the tail gas absorption device and the pressure gauge.

[0010] A heating resistor is also arranged outside the pyrolysis tube.

[0011] The part of the outlet pipe that enters the inside of the water tank is a spiral structure; the bottom of the spiral structure is connected to a condensate collection device.

[0012] A heating tube is sleeved outside the raw material box. The bottom of the heating tube is connected to the top of the water tank. The side of the water tank is connected to a condensation tank. A water pump is arranged inside the condensation tank. The water pump is connected to the inside of the heating tube through a pipeline, and can continuously provide low-temperature water for flue gas condensation while keeping the water body flowing.

[0013] A temperature sensor is arranged inside the pyrolysis tube.

[0014] The oxygen absorption device is filled with an oxygen absorbent, and the oxygen absorbent is a sulfite deoxidizer or ferrous chloride, etc.; the tail gas absorption device is filled with an alkaline substance such as sodium hydroxide solution, calcium hydroxide solution, etc.

[0015] The heat storage tube is filled with silicone oil or synthetic hydrocarbons and esters, etc.

[0016] The conveyor connecting the raw material box and the pyrolysis tube is a scraper conveyor, a belt conveyor, a screw conveyor or a bucket elevator, etc.

[0017] The flow meter is a direct mass flow meter or an indirect mass flow meter.

[0018] The air pump is a turbine pump, a vane pump, a piston pump or a peristaltic pump.

[0019] In the present invention, the high-temperature pyrolysis gas coming out of the pyrolysis tube is transported into the combustion chamber. An igniter in the combustion chamber generates an open flame to ignite the flue gas. The heat energy generated by the combustion is directly transferred to the heat storage tube, making full use of the high-temperature flue gas, reducing the heat loss of the flue gas, and utilizing the heat energy; at the same time, a temperature sensor is arranged inside the pyrolysis tube to detect the temperature change during the pyrolysis process at any time. When the temperature sensor indicates that the temperature is not sufficient for pyrolysis to proceed, the heating resistor is turned on for heating supplement; when the temperature reaches the experimental requirements, the heating resistor is turned off to save energy.

[0020] In the present invention, after the flue gas in the combustion chamber is ignited by an open flame, only CO2 and water vapor remain in the flue gas. Then the flue gas will enter the water tank, and after the heat of the flue gas is absorbed and utilized, it will flow back into the pyrolysis carbonization furnace as a pyrolysis carrier gas to continue pyrolyzing biomass.

[0021] After the biomass of the present invention is dried to reach the set moisture content, it is pyrolytically carbonized using CO2 as the carrier gas. After the pyrolysis gas containing CH4, CO, and H2 is combusted, high-temperature flue gas containing only CO2, water vapor, and oxygen is obtained. The high-temperature flue gas is introduced into the hydrothermal system to utilize the heat of the high-temperature flue gas, and at the same time, impurities other than CO2 in the flue gas are removed and recycled as the carrier gas back into the pyrolysis tube for continuous pyrolysis.

[0022] Aiming at the problem of heat loss caused by the condensation of pyrolysis gas in the biomass carbonization system, in the present invention, the pyrolysis gas at the outlet of the pyrolysis furnace is directly combusted in its entirety, and the heat generated by the combustion is stored. The flue gas at the outlet of the combustion chamber can provide heat for the drying of the raw materials, and the heat is fully utilized.

[0023] Aiming at the problem that the pyrolysis carrier gas cannot be recycled, in the present invention, the pyrolysis gas is directly combusted, and after condensation and purification, it is recycled into the pyrolysis tube as the pyrolysis carrier gas for reuse. Description of the Drawings

[0024] Figure 1 It is a schematic structural diagram of the biomass pyrolysis system of the present invention with high energy utilization rate and recycling of CO2 as the carrier gas;

[0025] In the figure: 1, raw material tank; 2, pyrolytic carbonization furnace; 3, heat storage pipe; 4, pyrolysis tube; 5, flow meter; 6, pressure gauge; 7, CO2 gas tank; 8, tail gas absorption device; 9, oxygen absorption device; 10, air pump; 11, condensate collection device; 12, water tank; 13, condensation tank; 14, combustion chamber; 15, oxygen cylinder. Detailed Embodiments

[0026] The present invention will be further described below in conjunction with specific embodiments. It should be noted that the following embodiments are all illustrative and are intended to provide further description of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0027] Embodiment 1

[0028] A biomass pyrolysis system with high energy utilization rate and recycling of CO2 as the carrier gas, as Figure 1 shown, includes a raw material tank 1, a pyrolytic carbonization furnace 2, a heat storage pipe 3, a pyrolysis tube 4, a flow meter 5, a pressure gauge 6, a CO2 gas tank 7, a tail gas absorption device 8, an oxygen absorption device 9, an air pump 10, a condensate collection device 11, a water tank 12, a condensation tank 13, a combustion chamber 14, and an oxygen cylinder 15;

[0029] The raw material tank 1 is connected to the pyrolysis tube 4 through a conveyor;

[0030] The pyrolysis tube 4 is arranged inside the pyrolysis carbonization furnace 2. Two combustion chambers 14 and heat storage tubes 3 are also arranged inside the pyrolysis carbonization furnace 2. The heat storage tubes 3 are arranged around the periphery of the pyrolysis tube 4. The two combustion chambers 14 are arranged at both ends of the pyrolysis carbonization furnace 2. Both ends of the heat storage tubes 3 enter the inside of the combustion chambers 14. The heat generated by the combustion chambers 14 can heat the heat storage tubes 3. A heating resistor is also arranged outside the pyrolysis tube 4. A temperature sensor is arranged inside the pyrolysis tube 4 for monitoring the internal temperature;

[0031] The bottoms of the combustion chambers 14 are respectively connected to the oxygen cylinder 15 and the pyrolysis tube 4. The tops of the combustion chambers 14 are connected to an outlet pipe. The other end of the outlet pipe enters the inside of the water tank 12 and passes through the water tank 12 and then is successively connected to the air pump 10, the oxygen absorption device 9, the tail gas absorption device 8, the pressure gauge 6, the flowmeter 5, and the pyrolysis tube 4. A CO2 gas cylinder 7 is also connected to the pipeline between the tail gas absorption device 8 and the pressure gauge 6. The part of the outlet pipe entering the inside of the water tank 12 is a spiral structure. The bottom of the spiral structure is connected to the condensate collection device 11; A heating pipe is sleeved outside the raw material box 1. The bottom of the heating pipe is connected to the top of the water tank 12. The side of the water tank 12 is connected to the condensation tank 13. A water pump is arranged inside the condensation tank 13. The water pump is connected to the inside of the heating pipe through a pipeline, which can continuously provide low-temperature water for flue gas condensation while keeping the water body flowing. The condensation tank 13 can be connected to an external water pipe to ensure the internal water temperature; Valves are arranged between every two of the above components.

[0032] In this embodiment, the biomass in the raw material box 1 can be first broken and loaded, or a crusher can be arranged in the raw material box 1 to realize the crushing of the biomass in the raw material box 1.

[0033] The tail gas absorption device 8 of the present invention is filled with alkaline substances such as sodium hydroxide solution, calcium hydroxide solution, etc., for absorbing the remaining tail gas in the final system. In this embodiment, sodium hydroxide solution is used as the absorption liquid to absorb the tail gas; The oxygen absorption device 9 is filled with an oxygen absorbent. The oxygen absorbent is a sulfite deoxidizer or ferrous chloride, etc., for absorbing the oxygen in the combustion gas. The oxygen absorbent used in this embodiment is ferrous chloride; The heat storage tubes 3 are filled with silicone oil or synthetic hydrocarbons and esters for storing heat. In this embodiment, the heat storage tubes 3 are filled with silicone oil; The conveyor connecting the raw material box 1 and the pyrolysis carbonization furnace 2 is a scraper conveyor, a belt conveyor, a screw conveyor or a bucket elevator, etc. In this embodiment, a belt conveyor is adopted; The flowmeter 5 is a direct mass flowmeter or an indirect mass flowmeter. In this embodiment, a direct mass flowmeter is adopted; The air pump 10 is a turbine pump, a vane pump, a piston pump or a peristaltic pump, etc. In this embodiment, a turbine pump is adopted.

[0034] In this embodiment, the heating resistor, the temperature sensor, the pressure gauge 6, and the flowmeter 5 can be connected to the controller. The controller receives the detected data and gives timely feedback to realize automatic control.

[0035] When the biomass pyrolysis system with high energy utilization rate and CO2 as the recycled carrier gas in this embodiment is in use, the specific steps are as follows:

[0036] (1) Place the biomass in the raw material box 1, and convey the crushed biomass in the raw material box 1 to the pyrolysis tube 4 through a conveyor. After the biomass is placed in the pyrolysis tube 4, before the experiment starts, open the CO2 gas cylinder 7, and flush the air in the gas path with CO2 to ensure that the pyrolysis atmosphere is CO2. At the same time, a stop valve is provided on the CO2 gas cylinder 7, and the stop valve can be closed to block the intake of CO2 after ensuring that the gas path is all CO2;

[0037] (2) Start the heating resistor to heat the inside of the pyrolysis tube 4. The program built into the controller controls the temperature to ensure accurate and controllable temperature. At the same time, turn on the air pump 10. The opening of the air pump 10 can ensure the flow of gas in the closed gas path. It should be noted that the power of the air pump 10 should not be too high, as long as it can drive the overall gas path to flow. The overall gas flow rate of the gas path is controlled by the flow meter 5. The flow meter 5 can adjust the gas flow rate to meet different experimental requirements. The internal pressure of the entire closed gas path is displayed by the pressure gauge 6. The pressure should not exceed 0.3 Mpa as much as possible to avoid damaging the mass flow meter; The pyrolysis gas will flow into the combustion chamber 14 due to the suction of the air pump 10. The igniter in the combustion chamber 14 will fully burn methane, CO, and H2 in the flue gas to form CO2 and water vapor. At the same time, the heat generated by combustion will be transferred to the heat storage tube 3. The controller will monitor the temperature in the pyrolysis carbonization furnace 2 in real time. When the heat stored in the heat storage tube 3 is not enough to meet the pyrolysis needs, the controller will turn on the heating resistor to supplement the heat energy; When the temperature is sufficient, the controller will turn off the heating resistor to save energy. After the pyrolysis is completed, adjust the three-way valve at the front end of the tail gas absorption device 8 to introduce the tail gas into the tail gas absorption device 8 to treat the last remaining tail gas in the system;

[0038] Since oxygen is introduced into the combustion chamber 14 to ensure full combustion, an oxygen absorption device 9 is provided to absorb the oxygen mixed in the pyrolysis gas after passing through the combustion chamber 14. Then the pyrolysis gas will enter the water tank 12. The low-temperature water in the water tank 12 is provided by the condensation tank 13. The water vapor and condensable volatiles in the pyrolysis gas will condense and precipitate in the water tank 12 due to the low-temperature water. After the pyrolysis gas exits the water tank 12, it is basically only CO2, which can be used for pyrolysis experiments. At the same time, the low-temperature water in the water tank will be heated to a certain temperature by the high-temperature flue gas, and then the high-temperature water will be pumped into the sample outlet end of the raw material box 1 to heat-treat the crushed biomass raw material, thus achieving the purpose of carrier gas recycling and heat energy reuse.

[0039] The specific implementation manners of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above implementation manners. Various changes can be made without departing from the spirit of the present invention within the knowledge scope of those of ordinary skill in the art.

Claims

1. A biomass pyrolysis system with high energy utilization and recycling of CO2 as carrier gas, characterized in that: It includes a raw material box, a pyrolysis carbonization furnace, a heat storage tube, a pyrolysis tube, a flow meter, a pressure gauge, a CO2 gas tank, a tail gas absorption device, an oxygen absorption device, an air pump, a condensation product collection device, a water tank, a combustion chamber, and an oxygen cylinder; The raw material box and the pyrolysis tube are connected through a conveyor; The pyrolysis tube is arranged in the pyrolysis carbonization furnace, and a combustion chamber and a heat storage tube are also arranged in the pyrolysis carbonization furnace. The heat storage tube is arranged outside the pyrolysis tube, and two combustion chambers are arranged at both ends of the pyrolysis carbonization furnace, and both ends of the heat storage tube enter the combustion chamber. The bottom of the combustion chamber is connected to the oxygen cylinder and the pyrolysis tube respectively, and the top of the combustion chamber is connected to the gas outlet pipe. The other end of the gas outlet pipe enters the water tank and passes through the water tank, and then is connected to the air pump, oxygen absorption device, tail gas absorption device, pressure gauge, flow meter, pyrolysis tube in turn. The pipe between the tail gas absorption device and the pressure gauge is also connected to the CO2 gas tank; A heating resistor is also arranged outside the pyrolysis tube.

2. The biomass pyrolysis system with high energy utilization and recycling of CO2 as carrier gas according to claim 1 is characterized in that: The portion of the air outlet pipe entering the water tank is a spiral structure.

3. The biomass pyrolysis system with high energy utilization and recycling of CO2 as carrier gas according to claim 2 is characterized in that: The bottom of the spiral structure is connected to a condensate collecting device.

4. The biomass pyrolysis system with high energy utilization and recycling of CO2 as carrier gas according to claim 1 is characterized in that: A heating pipe is sleeved outside the raw material box, the bottom of the heating pipe is connected to the top of the water tank, the side of the water tank is connected to the condensation tank, the condensation tank has a built-in water pump, and the water pump is connected to the inside of the heating pipe through a pipeline.

5. The biomass pyrolysis system with high energy utilization and recycling of CO2 as carrier gas according to claim 1 is characterized in that: A temperature sensor is arranged in the pyrolysis tube.

6. The biomass pyrolysis system with high energy utilization and recycling of CO2 as carrier gas according to claim 1 is characterized in that: The oxygen absorption device is filled with an oxygen absorber, which is a sulfite deoxidizer or ferrous chloride; the tail gas absorption device is filled with an alkaline substance.

7. The biomass pyrolysis system with high energy utilization and recycling of CO2 as carrier gas according to claim 1 is characterized in that: The heat storage tube is filled with silicone oil or synthetic hydrocarbons and esters.

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