A variable speed airflow type straw fluidization carbonization method

Abstract

The present invention relates to a variable-speed airflow straw fluidized carbonization method, which primarily includes shredding and shaping, multi-channel parallel feeding, multi-channel staggered driving, gas-solid confluence, dynamic sorting, multi-channel confluence, gas-solid separation, pyrolysis gas combustion, flue gas distribution, and constant-flow pressurization. The present invention is applicable to straw feedstocks with complex compositions and varying lengths, and boasts strong adaptability, rapid heat transfer, and high production efficiency, making it suitable for large-scale straw carbonization.

Description

Technical Field

[0001] The invention belongs to the technical field of comprehensive utilization of biomass energy, and in particular relates to a variable-speed airflow type straw fluidization carbonization method. Background Art

[0002] Biomass carbonization technology is a thermochemical conversion process that converts various biomasses (such as crop straw, forestry waste, and domestic garbage) into biochar and combustible pyrolysis gas through thermal cracking under anaerobic or anoxic conditions. This technology plays a significant role in reducing environmental pollution caused by agricultural waste incineration, improving energy efficiency, increasing soil fertility, and reducing carbon emissions and sequestering carbon.

[0003] Traditional fluidized-bed carbonization technology uses upward-flowing gas to suspend biomass particles and create a fluid-like motion, forming a "gas-solid fluidized bed." This significantly increases the contact area between particles and gas, improving heat transfer efficiency. However, since fluidized-bed operation requires the biomass feedstock to have a certain particle size and fluidity, achieving uniform fluidization of all particles is difficult when faced with varying particle sizes. Consequently, high pretreatment requirements are placed on the feedstock, increasing both initial processing costs and complexity.

[0004] Obviously, the raw material processing capacity of a single fluidized carbonization method is greatly limited. To address the complex composition and varying lengths of straw raw materials, it is necessary to develop specific and stable process control methods to provide efficient and stable straw carbonization treatment and meet the needs of large-scale straw disposal applications. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a variable-speed airflow type straw fluidization carbonization method, which can realize large-scale disposal of straw.

[0006] The present invention provides a variable speed airflow type straw fluidization carbonization method, comprising the following steps:

[0007] (1) Shredding the straw to obtain straw raw materials;

[0008] (2) The straw raw materials are put into n fluidizing mechanisms in parallel, and the carbonized gas flow is introduced into the n fluidizing mechanisms from the bottom respectively, and the gas flow rates Q1, Q2, ..., Q n Implement periodic interleaving control respectively; wherein, n≥2;

[0009] (3) The straw raw material is fully mixed with the carbonized air flow in the fluidizing mechanism, and the straw raw material presents two states under the sorting action of the carbonized air flow: a fixed state and a fluidized state; operations are performed according to different fixed states and fluidized states;

[0010] (4) combining the pyrolysis gas obtained by n of the fluidizing mechanisms with the straw charcoal, separating the straw charcoal from the pyrolysis gas by gravity or centrifugal force, cooling the separated straw charcoal and packaging it, dividing the separated pyrolysis gas into two, burning the first part of the pyrolysis gas to generate high-temperature flue gas; mixing the high-temperature flue gas with the second part of the pyrolysis gas to form the above-mentioned carbonization gas flow, and utilizing the excess high-temperature flue gas for waste heat utilization;

[0011] (5) The total flow rate of the carbonized gas flow is controlled, and then pressurized to perform step (2), and this process is repeated.

[0012] Furthermore, the straw raw material in step (1) comprises short straw segments and debris formed during the shredding process.

[0013] Furthermore, the size of the short straw segment is 50 mm to 100 mm.

[0014] Furthermore, the fluidization mechanism in step (2) can be a fluidized bed, an entrained bed or other equipment that can put the raw materials into a fluidized state.

[0015] Furthermore, the periodic staggered control in step (2) refers to the gas flow rates Q1, Q2, ..., Q n Both show periodic reciprocating changes and meet .

[0016] Furthermore, the periodic reciprocating change is a sinusoidal periodic change, which takes the following form:

[0017] ;

[0018] Wherein, t is time; i ranges from 1 to n; k is period, ranging from 10 seconds to 10 minutes; S is the cross-sectional area of ​​the air inlet of the fluidization mechanism; Vmin is the wind speed when the straw raw material is in a fixed state; Vmax is the wind speed when the straw raw material is in a fluidized state.

[0019] Furthermore, the periodic staggered control can be achieved by setting a flow control valve on the air inlet pipe of the fluidizing mechanism, and the gas flow rates Q1, Q2, ..., Q can be controlled by adjusting the opening of the flow control valve. n control.

[0020] Furthermore, in step (3), the fixed state refers to the state in which the heavier straw material settles to the bottom of the fluidizing mechanism and remains relatively stationary; the fluidized state refers to the state in which the lighter straw material is suspended in the space of the fluidizing mechanism and remains in relative motion.

[0021] Furthermore, the operations in step (3) are specifically performed according to different fixed states and fluidized states:

[0022] Enhanced fixed carbonization: In the i-th fluidization mechanism, when the gas flow rate Q i During the periodic descent, most of the straw raw materials settle to the bottom of the fluidization mechanism and are transformed into a fixed state, and are then carbonized;

[0023] Fully fixed carbonization: In the i-th fluidization mechanism, when the gas flow rate Q i When the pressure reaches the minimum, all the straw materials settle to the bottom of the fluidization mechanism and are in a fixed state, and all the materials are fixedly carbonized;

[0024] Enhanced fluidized carbonization: In the i-th fluidized mechanism, when the gas flow rate Q i During the periodic rise, most of the straw materials are blown up by the airflow and transformed into a fluidized state, and fluidized carbonization is carried out;

[0025] Fully fluidized carbonization: In the i-th fluidized mechanism, when the gas flow rate Q i When the pressure reaches the maximum, all the straw materials are suspended in the fluidization mechanism and are in a fluidized state, and all the materials are subjected to fluidized carbonization;

[0026] The above i takes values ​​from 1 to n.

[0027] Furthermore, in the fixed carbonization process, the raw materials are fixed, and the carbonization gas flow flows through the gaps between the raw materials to heat and raise the temperature of the raw materials, causing pyrolysis reaction of the raw materials to form pyrolysis gas and straw char. In the fluidized carbonization process, the raw materials are fluidized and suspended in the carbonization gas flow. During the suspension process, the raw materials are heated and heated, causing pyrolysis reaction to form pyrolysis gas and straw char.

[0028] Furthermore, the total flow rate Qsum in step (5) and the carbonization air flow temperature T have the following relationship:

[0029] ;

[0030] Where n is the number of fluidizing mechanisms; S is the cross-sectional area of ​​the air inlet of the fluidizing mechanism; Vmin is the wind speed when the straw raw material is in a fixed state; Vmax is the wind speed when the straw raw material is in a fluidized state;

[0031] ;

[0032] Where, Cc is the specific heat capacity of straw charcoal; Cw is the specific heat capacity of water; Cq is the specific heat capacity of pyrolysis gas; ρ is the gas density of pyrolysis gas under standard conditions; w is the moisture content of straw raw material; J is the feed amount of straw raw material; Tc is the carbonization temperature of straw raw material.

[0033] Beneficial effects:

[0034] (1) The present invention has multiple fluidizing mechanisms, and the gas flow rate in each fluidizing mechanism is dynamically adjusted, so that the gas flow rate also changes dynamically during the entire carbonization process, providing suitable carbonization conditions for raw materials of different particle sizes and lengths, and greatly improving the adaptability of the carbonization device to raw materials.

[0035] (2) The straw raw material and the high-temperature carbonization airflow of the present invention are mixed through multi-path interlaced driving. The airflow directly wraps the surface and internal pores of the straw, realizing a more efficient and thorough direct heat exchange between the straw raw material and the high-temperature airflow. The efficient carbonization process of the straw can be completed in a shorter time, significantly improving the overall production efficiency and capacity.

[0036] (3) The present invention realizes the alternating operation of fixed carbonization and fluidized carbonization modes through periodic staggered airflow control and dynamic sorting. The two states are continuously alternating, overcoming the heat transfer blind spots (carbonization dead corners) that are easily formed in traditional methods under a single state, ensuring that the straw raw material can be fully and evenly heat treated throughout the entire carbonization cycle, significantly improving the uniformity and quality stability of the carbonized product.

[0037] (4) The present invention can be applied to straw raw materials with complex composition and different lengths. It has the advantages of strong adaptability, fast heat conduction speed and high production efficiency, and is suitable for the application scenario of large-scale straw carbonization disposal. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a process flow chart of the present invention.

[0039] Figure 2 Flow rate variation curve of the fluidization mechanism according to an embodiment of the present invention.

[0040] Figure 3 This is the wind speed variation curve of the fluidization mechanism according to the embodiment of the present invention. DETAILED DESCRIPTION

[0041] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0042] As a specific embodiment, a variable speed airflow straw fluidization carbonization method is provided, comprising the following steps:

[0043] (1) Shredding and shaping: Shredding the straw to obtain straw raw materials.

[0044] (2) Multi-channel parallel feeding: The straw raw material is fed into n fluidizing mechanisms in parallel with a feeding amount J; the feeding amount J is a set value, that is, the expected amount of straw to be processed; the straw raw material includes the short straw segments and the debris formed during the shredding and shaping process; and n ≥ 2.

[0045] (3) Multi-path staggered drive: The high-temperature carbonized air flow is introduced from the bottom into n fluidizing mechanisms respectively; the fluidizing mechanism can be a fluidized bed, an air flow bed or other equipment that can fluidize the raw materials; the carbonized air flow rates Q1, Q2, ..., Q n Implement periodic staggered control; the periodic staggered control refers to the carbonization air flow Q1, Q2, ..., Q n Both show periodic reciprocating changes and meet ;

[0046] The Qsum is the total flow rate in the n fluidizing mechanisms and is an undetermined parameter related to the feed amount J.

[0047] In some embodiments, the multi-channel staggered drive can be achieved by setting a flow control valve on the air inlet pipe of the fluidizing mechanism, and the gas flow rates Q1, Q2, ..., Q n control.

[0048] (4) Gas-solid combined flow: In the fluidizing mechanism, the straw raw material (solid) and the carbonized air flow (gaseous) are fully mixed.

[0049] (5) Dynamic sorting: In the fluidized structure, the straw raw material will present two states under the sorting action of the carbonized airflow: a fixed state and a fluidized state; the fixed state means that the heavier raw material settles to the bottom of the fluidized structure and remains relatively static; the fluidized state means that the lighter raw material is suspended in the space of the fluidized structure and remains in a relative motion state; since the gas flow Qi is not constant but presents periodic reciprocating changes, the automatic sorting is a periodic dynamic process. Including the following situations:

[0050] Enhanced fixed carbonization: In the i-th fluidizing mechanism, when the gas flow rate Qi decreases periodically, more and more raw materials in the fluidized state settle to the bottom of the fluidizing mechanism and are transformed into a fixed state, and fixed carbonization is implemented; the fixed carbonization is that the raw materials are in a fixed state, and the carbonization gas flow flows through the gaps between the raw materials to heat the raw materials, and the raw materials undergo pyrolysis reaction to form pyrolysis gas and straw charcoal; the value of i is 1~n.

[0051] Fully fixed carbonization: In the i-th fluidizing mechanism, when the gas flow rate Qi reaches the minimum and the corresponding inlet wind speed at the bottom of the fluidizing mechanism is ≤Vmin, all raw materials settle to the bottom of the fluidizing mechanism and are in a fixed state, and all raw materials are fixedly carbonized.

[0052] Enhanced fluidized carbonization: In the i-th fluidizing mechanism, when the gas flow rate Qi rises periodically, more and more raw materials in a fixed state are blown up by the airflow and transformed into a fluidized state, and fluidized carbonization is implemented; the fluidized carbonization is that the raw materials are in a fluidized state and suspended in the carbonization airflow. The raw materials are heated and heated during the suspension process, and a pyrolysis reaction occurs to form pyrolysis gas and straw charcoal.

[0053] Fully fluidized carbonization: In the i-th fluidizing mechanism, when the gas flow rate Qi reaches the maximum and the inlet wind speed at the bottom of the corresponding fluidizing mechanism is ≥ Vmax, all raw materials are suspended in the fluidizing mechanism in a fluidized state, and all raw materials are subjected to fluidized carbonization.

[0054] (6) Multi-channel merging: merging all the pyrolysis gases and straw charcoal drawn out by n fluidizing mechanisms.

[0055] (7) Gas-solid separation: Use gravity or centrifugal force to separate the straw charcoal (solid phase) from the pyrolysis gas (gas phase); cool the separated straw charcoal and package it.

[0056] (8) Pyrolysis gas combustion: The separated pyrolysis gas is divided into two parts. The first part of the pyrolysis gas is burned to produce high-temperature flue gas.

[0057] (9) Flue gas distribution: The high-temperature flue gas is mixed with the second portion of pyrolysis gas, and temperature control is implemented to form the carbonized gas flow at a temperature of T; the carbonized gas flow is oxygen-free gas; T is a parameter to be determined. The excess high-temperature flue gas is used for waste heat utilization.

[0058] (10) Constant flow pressurization: The total flow rate of the carbonized gas flow is controlled, and then pressurized to perform step (3), and so on. The total flow rate control means that the total flow rate of the carbonized gas flow is constant and maintained at Qsum. The Qsum is a parameter to be determined.

[0059] In some embodiments, the gas-solid separation step can be achieved by using a gravity settling chamber using gravity or by using a cyclone separator using centrifugal force.

[0060] As a specific embodiment, a method for determining parameters of variable-speed airflow straw fluidized carbonization is also provided, comprising the following steps:

[0061] (1) Analysis of straw characteristics: Sample the straw raw material and perform moisture content test to obtain the moisture content w of the straw raw material;

[0062] (2) Straw carbonization analysis: The straw raw material is sampled and subjected to anaerobic pyrolysis to obtain the straw carbonization temperature Tc;

[0063] (3) Analysis of straw char characteristics: Physical testing of the solid product (straw char) collected in step (2) to obtain the specific heat capacity Cc of the straw char;

[0064] (4) Analysis of cracking gas characteristics: Physical testing of the gaseous product (cracking gas) collected in step (2) to obtain the specific heat capacity Cq of the cracking gas;

[0065] (5) Flue gas characteristic analysis: The cracking gas in step (4) is burned with air, the flue gas is collected and physically analyzed to obtain the gas density ρ of the flue gas under standard conditions;

[0066] (6) Fluidization characteristics analysis: Take samples of straw raw materials and conduct fluidization tests to measure the wind speed Vmin when the straw raw materials are in a fixed state and the wind speed Vmax when they are in a fluidized state;

[0067] (7) Establishing process parameter model:

[0068] According to the fluidization characteristics of straw raw materials, a fluidization equation can be established to describe the total flow rate Qsum of carbonization airflow:

[0069] ;

[0070] Where n is the number of fluidizing mechanisms; S is the cross-sectional area of ​​the air inlet of the fluidizing mechanism; Vmin is the wind speed when the straw raw material is in a fixed state; Vmax is the wind speed when the straw raw material is in a fluidized state;

[0071] According to the principle of thermal energy conservation of heat conduction, the heat transfer equation can be established to calculate the total carbonization air flow Qsum:

[0072] ;

[0073] Where, Cc is the specific heat capacity of straw charcoal; Cw is the specific heat capacity of water; Cq is the specific heat capacity of pyrolysis gas; ρ is the gas density of pyrolysis gas under standard conditions; w is the moisture content of straw raw material; J is the feed amount of straw raw material; Tc is the carbonization temperature of straw raw material.

[0074] (8) Model solution: Solve the two models in step (7) together to obtain the process parameters: the total flow rate Qsum of the carbonization airflow and the temperature T of the carbonization airflow.

[0075] In some embodiments, the high-temperature carbonization gas flow rates Q1, Q2, ..., Q n Select sinusoidal periodic change and use the following form:

[0076] ;

[0077] Wherein, t is time; i ranges from 1 to n; k is period, ranging from 10 seconds to 10 minutes; S is the cross-sectional area of ​​the air inlet of the fluidization mechanism; Vmin is the wind speed when the straw raw material is in a fixed state; Vmax is the wind speed when the straw raw material is in a fluidized state.

[0078] Example 1

[0079] This embodiment takes the treatment of rice straw as an example and provides a method for determining parameters of variable-speed airflow straw fluidized carbonization for further details, including:

[0080] (1) Characteristic analysis and carbonization analysis of rice straw:

[0081] First, the rice straw raw material was sampled and the moisture content w of the rice straw raw material was measured using a moisture content tester, which was 30%. Then, the rice straw raw material was chemically tested and an anaerobic pyrolysis experiment was performed using a horse-boil furnace, and the dry-basis carbonization temperature Tc of the rice straw was obtained to be 350°C, and the dry-basis carbonization rate of the rice straw was 35%.

[0082] (2) Analysis of characteristics of rice straw charcoal, pyrolysis gas and flue gas:

[0083] The sampled rice straw was heated to 350°C in a horse-boil furnace for pyrolysis, and the pyrolysis gas and straw were subjected to physical tests. The specific heat capacity Cc of the rice straw was measured to be 0.36Kcal / kg·°C using a specific heat meter, and the specific heat capacity Cq of the pyrolysis gas was 0.28Kcal / kg·°C. The cracking gas was burned in air, and the flue gas was collected and physically analyzed, and the gas density ρ of the flue gas under standard conditions was obtained to be 1.19kg / m 3 ;

[0084] (3) Fluidization characteristics analysis:

[0085] A vertical fluidization pipe was built and equipped with a small fan. Straw samples were sampled for fluidization tests. The wind speed Vmin = 1.2 m / s when the straw was in a fixed state and Vmax = 4.5 m / s when it was in a fluidized state were measured.

[0086] (4) Establishing process parameter model:

[0087] In this embodiment, three parallel fluidizing mechanisms are provided, i.e., n = 3. The cross-sectional area of ​​the air inlet at the bottom of the fluidizing mechanism is measured, and the measured cross-sectional area S = 0.3 m. Finally, based on the fluidization characteristics of the straw raw material, a fluidization equation can be established to describe the total carbonization airflow rate Qsum in this embodiment:

[0088] ;

[0089] According to the principle of thermal energy conservation of heat conduction, the heat transfer equation can be established to calculate the total carbonization air flow Qsum:

[0090] ;

[0091] Where, feed rate J = 1t / h = 0.278kg / s, moisture content of rice straw w = 30%, dry basis carbonization temperature of rice straw Tc = 350℃, specific heat capacity of rice straw Cc = 0.36Kcal / kg·℃, specific heat capacity of pyrolysis gas Cq = 0.28Kcal / kg·℃, specific heat capacity of water Cw = 1Kcal / kg·℃, T is the carbonization gas flow temperature (to be quantified). The gas density ρ of pyrolysis gas under standard conditions is 1.19kg / m 3 ;

[0092] (5) Model solution:

[0093] Solve the two models in step (4) together to obtain the process parameters: total carbonization air flow Qsum = 2.565m 3 / s=9234m 3 / h and carbonization air flow temperature T=633℃.

[0094] Example 2

[0095] This embodiment takes the disposal of rice straw as an example, Figure 1 、 Figure 2 and Figure 3 A variable speed air flow straw fluidized carbonization method is further described, including:

[0096] (1) Shredding and shaping: First, the rice straw with a moisture content of 30% is sent to a vibrating screening machine via a conveyor belt to remove impurities such as stones and metals; then the rice straw is broken into uniform short segments of 50-100mm by a 110kW double-shaft shredder, and shredded and shaped to complete the particle size control of the raw material.

[0097] (2) Multi-channel parallel feeding: The straw raw material is fed into three fluidizing mechanisms in parallel at a feeding rate of J = 1 ton / hour; this is equivalent to the feeding rate of each fluidizing mechanism being one-third J, that is, 0.093 kg / s.

[0098] (3) Multi-path staggered drive: The high-temperature carbonized gas flow is introduced into the three fluidizing mechanisms from the bottom; the gas flow rates Q1, Q2, and Q3 in the three fluidizing mechanisms are respectively controlled by periodic staggered control; Figure 2 As shown in the figure, in this embodiment, Q1, Q2, and Q3 all adopt a sinusoidal variation law with a period of 20 seconds, and the minimum flow rate Qmin is 0.36m 3 / s, the maximum flow rate Qmax is 1.35m 3 / s; Q1, Q2, Q3 are 120° out of phase, and the total carbonization airflow Qsum is constant at 2.565m 3 In this embodiment, the multi-channel staggered drive can be achieved by three butterfly valves provided on the air inlet pipe of the fluidizing mechanism, and the gas flow rates Q1, Q2, and Q3 are controlled by the opening of the three butterfly valves.

[0099] Gas-solid co-flow: In the fluidizing mechanism, the incoming straw material is thoroughly mixed with the high-temperature carbonizing gas flow. In this embodiment, the high-temperature, oxygen-free carbonizing gas flow is evenly introduced into the bottom of the fluidizing furnace through a porous gas distribution plate (8mm pore size, 35% porosity), where it is thoroughly mixed with the straw material. The gas flow directly penetrates the surface and pores of the material. This gas distribution plate acts as a wind distributor, providing conditions for fluidized carbonization of the straw.

[0100] Dynamic Sorting: In this embodiment, the three fluidizing mechanisms, under the action of the high-temperature carbonized airflow, separate the straw into two states: a stationary state and a fluidized state. In this embodiment, the gas flow rates Q1, Q2, and Q3 in the three fluidizing mechanisms exhibit sinusoidal periodic variations, resulting in automatic sorting as a dynamic process with a 20-second periodicity.

[0101] Enhanced fixed carbonization: In this embodiment's three fluidizing mechanisms, when gas flow rates Q1, Q2, or Q3 periodically decrease, a large amount of straw settles to the bottom of the fluidizing mechanism, becoming fixed and carbonized. Conductive heating raises the internal bed temperature to 350°C, causing pyrolysis of the material to form pyrolysis gas and straw charcoal. This deep pyrolysis reaction increases the charcoal yield during the fixed carbonization phase to 38%.

[0102] Fully fixed carbonization: In the three fluidization mechanisms of this embodiment, when the gas flow rate Q1, Q2 or Q3 reaches Qmin = 0.36m 3 / s. Figure 3 As shown, when the inlet wind speed at the bottom of the fluidizing mechanism is ≤ Vmin (1.2 m / s), all the rice straw raw materials settle to the bottom of the fluidizing mechanism and are in a fixed state, and all the rice straw raw materials are fixedly carbonized.

[0103] Enhanced fluidized carbonization: In the three fluidized mechanisms of this embodiment, when the gas flow rate Q1, Q2 or Q3 increases periodically, more and more rice straw raw materials are transformed into a fluidized state. At this time, fluidized carbonization occurs, and the surface temperature rises from 350°C to 630°C. The rice straw raw materials are heated during the suspension process, and a pyrolysis reaction occurs to form pyrolysis gas and rice straw charcoal. The charcoal yield in the fluidized carbonization stage is stabilized at 35%.

[0104] Fully fluidized carbonization: In the three fluidized mechanisms of this embodiment, when the gas flow rate Q1, Q2 or Q3 reaches Qmax = 1.35m 3 / s. Figure 3 As shown, when the inlet wind speed at the bottom of the fluidization mechanism is ≥ Vmax (ie 4.5 m / s), all the rice straw raw materials are fluidized and carbonized.

[0105] Multi-channel confluence: The pyrolysis gas from the outlet of the three fluidizing mechanisms is combined with the straw charcoal through a high-temperature resistant stainless steel pipe and enters the gas-solid separation device.

[0106] Gas-solid separation: The gas-solid separation device in this embodiment adopts a cyclone separator with a cylinder diameter of Φ0.6m, a total height of 2.5m, and a cylinder height of 1.3m; the cyclone separator returns the gas phase (pyrolysis gas) to the carbonization system for circulation, and the solid phase (straw charcoal) is sent to the cooling and cooling system; the cooling and cooling device uses a water-cooled spiral with a length of 3m and a diameter of Φ0.5m, which is installed at the bottom of the cyclone separator to cool the carbon powder to room temperature for discharge and packaging.

[0107] Pyrolysis gas combustion: In this embodiment, the total flow rate of carbonization gas Qsum = 2.565m 3 / s=9234m 3 / h, carbonization air flow temperature T=633℃. Therefore, during the carbonization process, the control system controls the variable frequency fan and intelligent butterfly valve to adjust the air flow to about 4000m 3 / h of pyrolysis gas enters the combustion chamber, mixes with preheated air and burns to produce 1000℃ high-temperature flue gas.

[0108] Flue gas distribution: The control system controls the variable frequency fan and intelligent butterfly valve to distribute about 5000m 3 / h of pyrolysis gas enters the system for circulation and mixes with the high-temperature flue gas to control the temperature T of the high-temperature oxygen-free carbonization gas flow to around 630°C. At the same time, a waste heat boiler with a production capacity of 2t / h and a pressure of 0.5Mpa is configured to recover energy from the excess high-temperature flue gas.

[0109] Constant flow pressurization: In this embodiment, the carbonized gas flows through a variable frequency centrifugal fan (power 220kW, air volume 13000m 3 / h) pressurization, the total flow rate is constantly controlled to Qsum=2.565m 3 / s, and then pressurize to perform step (3), and repeat this process.

[0110] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A variable speed air flow straw fluidization carbonization method, characterized by: The steps include: (1) Shredding the straw to obtain straw raw materials; (2) The straw raw materials are put into n fluidizing mechanisms in parallel, and the carbonized gas flow is introduced into the n fluidizing mechanisms from the bottom respectively, and the gas flow rates Q1, Q2, ..., Q n Implement periodic interleaving control respectively; wherein, n≥2; (3) The straw raw material is fully mixed with the carbonized air flow in the fluidizing mechanism, and the straw raw material presents two states under the sorting action of the carbonized air flow: a fixed state and a fluidized state; operations are performed according to different fixed states and fluidized states; (4) combining the pyrolysis gas obtained by n of the fluidizing mechanisms with the straw charcoal, separating the straw charcoal from the pyrolysis gas by gravity or centrifugal force, cooling the separated straw charcoal and packaging it, dividing the separated pyrolysis gas into two, burning the first part of the pyrolysis gas to generate high-temperature flue gas; mixing the high-temperature flue gas with the second part of the pyrolysis gas to form the above-mentioned carbonization gas flow, and utilizing the excess high-temperature flue gas for waste heat utilization; (5) The total flow rate of the carbonized gas flow is controlled, and then pressurized to perform step (2), and this process is repeated.

2. The variable speed airflow straw fluidization carbonization method according to claim 1, characterized in that: The straw raw material in step (1) comprises short straw segments and debris formed during the shredding process.

3. The variable speed airflow straw fluidized carbonization method according to claim 2, characterized in that: The size of the short straw segment is 50 mm to 100 mm.

4. The variable speed airflow straw fluidization carbonization method according to claim 1, characterized in that: The periodic staggered control in step (2) refers to the gas flow rates Q1, Q2, ..., Q n Both show periodic reciprocating changes and meet .

5. The variable speed airflow straw fluidized carbonization method according to claim 4, characterized in that: The periodic reciprocating change is a sinusoidal periodic change, which takes the following form: ； Wherein, t is time; i ranges from 1 to n; k is period, ranging from 10 seconds to 10 minutes; S is the cross-sectional area of ​​the air inlet of the fluidization mechanism; Vmin is the wind speed when the straw raw material is in a fixed state; Vmax is the wind speed when the straw raw material is in a fluidized state.

6. The variable speed airflow straw fluidized carbonization method according to claim 1, characterized in that: In step (3), the fixed state refers to the state in which the heavier straw material settles to the bottom of the fluidizing mechanism and remains relatively still; the fluidized state refers to the state in which the lighter straw material is suspended in the space of the fluidizing mechanism and remains in relative motion.

7. The variable speed airflow straw fluidized carbonization method according to claim 1, characterized in that: The operations in step (3) are specifically performed according to different fixed states and fluidized states: Enhanced fixed carbonization: In the i-th fluidization mechanism, when the gas flow rate Q i During the periodic descent, most of the straw raw materials settle to the bottom of the fluidization mechanism and are transformed into a fixed state, and are then carbonized; Fully fixed carbonization: In the i-th fluidization mechanism, when the gas flow rate Q i When the pressure reaches the minimum, all the straw materials settle to the bottom of the fluidization mechanism and are in a fixed state, and all the materials are fixedly carbonized; Enhanced fluidized carbonization: In the i-th fluidized mechanism, when the gas flow rate Q i During the periodic rise, most of the straw materials are blown up by the airflow and transformed into a fluidized state, and fluidized carbonization is carried out; Fully fluidized carbonization: In the i-th fluidized mechanism, when the gas flow rate Q i When the pressure reaches the maximum, all the straw materials are suspended in the fluidization mechanism and are in a fluidized state, and all the materials are subjected to fluidized carbonization; The above i takes values ​​from 1 to n.

8. The variable speed airflow straw fluidized carbonization method according to claim 1, characterized in that: The total flow rate Qsum in step (5) and the carbonization air flow temperature T have the following relationship: ； Where n is the number of fluidizing mechanisms; S is the cross-sectional area of ​​the air inlet of the fluidizing mechanism; Vmin is the wind speed when the straw raw material is in a fixed state; Vmax is the wind speed when the straw raw material is in a fluidized state; ； Where, Cc is the specific heat capacity of straw charcoal; Cw is the specific heat capacity of water; Cq is the specific heat capacity of pyrolysis gas; ρ is the gas density of pyrolysis gas under standard conditions; w is the moisture content of straw raw material; J is the feed amount of straw raw material; Tc is the carbonization temperature of straw raw material.

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