Catalytic pyrolysis cascade combustion method for reducing carbon emission by using traditional Chinese medicine residue as alternative fuel

Abstract

The application discloses a kind of traditional Chinese medicine residue alternative fuel catalytic pyrolysis cascade combustion method for reducing carbon emission, belong to solid waste resource and energy chemical industry technical field.It includes the following steps: (1) traditional Chinese medicine residue collection and pretreatment;(2) grading and on-line detection;(3) catalytic directional pyrolysis;(4) cascade combustion and replacement;(5) intelligent closed-loop control;(6) process control and ash utilization.The application is by the complex source, difficult disposal traditional Chinese medicine residue is pretreated, directly replaces part of coal for the calcination process of cement rotary kiln, not only realizes the resource, harmlessness, energy utilization of traditional Chinese medicine residue, solves the industry common problem that traditional Chinese medicine residue is difficult to large-scale industrial application due to high humidity, unstable calorific value, also provides stable and reliable alternative fuel source for cement production, effectively reduces the dependence of cement enterprises on coal and other primary energy.

Claims

1. A catalytic pyrolysis-cascade combustion method for reducing carbon emissions by using traditional Chinese medicine residue as a substitute fuel, characterized in that: Includes the following steps: (1) Collection and pretreatment of Chinese medicine residue: The Chinese medicine residue is collected, dried, crushed and sorted to obtain alternative fuels for Chinese medicine; (2) Grading and online detection: The components of the pretreated Chinese medicine residue are detected online, the volatile matter content is calculated based on the detection results, and the residue is divided into high-quality pyrolysis raw materials and conventional alternative fuels according to the volatile matter content; (3) Catalytic directional pyrolysis: After mixing the high-quality pyrolysis raw material obtained in step (2) with the catalyst, it is sent to an external pyrolysis reactor with cement kiln tail exhaust gas as the heat source for catalytic directional pyrolysis to generate hydrogen-rich pyrolysis gas and modified pyrolysis semi-coke, and the pyrolysis products are detected. (4) Cascade combustion and substitution: The hydrogen-rich pyrolysis gas obtained in step (3) is introduced into the high-temperature zone of the cement decomposition furnace or pre-combustion chamber through an independent pipeline. The modified pyrolysis semi-coke is mixed with the conventional alternative fuel and coal obtained in step (2) and then injected into the decomposition furnace or pre-combustion chamber for co-combustion to achieve partial substitution of traditional coal. (5) Intelligent closed-loop control: Based on the online detection data of pyrolysis products and the flue gas monitoring data of the decomposition furnace or pre-combustion chamber, the pyrolysis temperature, catalyst dosage, hydrogen-rich pyrolysis gas and modified pyrolysis semi-coke distribution ratio and co-firing ratio are dynamically optimized through a preset control model. (6) Utilization of ash residue: Ash residue generated after the combustion of alternative fuels is used as cement raw material to replace clay raw material.

2. The catalytic pyrolysis-cascade combustion method for reducing carbon emissions by using traditional Chinese medicine residue as a substitute fuel, as described in claim 1, is characterized in that: In step (1), the drying conditions are: air drying at room temperature for 3-4 days, during which the residue is turned over to reduce the moisture content of the residue to below 15%, and removing metal impurities and inert components by magnetic separation and air separation to separate the residue with a particle size of less than 40 mm after crushing.

3. The catalytic pyrolysis-cascade combustion method for reducing carbon emissions by replacing traditional Chinese medicine residue with fuel according to claim 1, characterized in that: In step (2), the online component detection is performed using near-infrared spectroscopy or laser-induced breakdown spectroscopy. The standard for diversion is: the residue with a volatile content higher than 60% and a lignin content higher than 23% is diverted as high-quality pyrolysis raw material, and the rest is conventional alternative fuel.

4. The catalytic pyrolysis-cascade combustion method for reducing carbon emissions by replacing traditional Chinese medicine residue with fuel according to claim 1, characterized in that: In step (3), the catalyst is one or more of cement kiln fly ash, carbide slag, steel slag, and red mud, and the catalyst addition mass is 1% to 5% of the mass of the high-quality pyrolysis raw material; The conditions for catalytic directional pyrolysis are: under oxygen-deficient conditions, the pyrolysis temperature is 400~550℃; and the molar ratio of H2 to CO in the generated hydrogen-rich pyrolysis gas is 1.2~2.

5.

5. The catalytic pyrolysis-cascade combustion method for reducing carbon emissions by replacing traditional Chinese medicine residue with fuel according to claim 4, characterized in that: In step (4), hydrogen-rich pyrolysis gas is injected into the bottom or middle area of ​​the cement decomposition furnace or pre-combustion chamber; In the blended combustion, the amount of conventional alternative fuel is 20% to 30% of the original coal mass, and the mass ratio of modified pyrolysis semi-coke to blended coal is 1:2 to 1:

4.

6. The catalytic pyrolysis-cascade combustion method for reducing carbon emissions by replacing traditional Chinese medicine residue with fuel according to claim 5, characterized in that: In step (5), the intelligent closed-loop control specifically includes the following steps: (5.1) Real-time monitoring of the composition of hydrogen-rich pyrolysis gas, the calorific value of modified pyrolysis semi-coke, the temperature of the decomposition furnace or pre-combustion chamber, and the composition of the outlet flue gas; (5.2) When the fluctuation of H2 content in hydrogen-rich pyrolysis gas exceeds the preset threshold, the catalyst dosage is automatically increased and the pyrolysis temperature is raised. (5.3) When the temperature field fluctuation of the decomposition furnace or pre-combustion chamber is detected to exceed the preset range, the total fuel injection amount is automatically increased; (5.4) When NO is detected in the flue gas composition x When the concentration fluctuation exceeds the preset threshold, adjust the proportion of modified pyrolysis semi-coke blending. (5.5) When the fluctuation of modified pyrolysis semi-coke is detected to exceed the preset range, the proportion of pulverized coal is increased to maintain the stability of total calorific value.

7. A catalytic pyrolysis-cascade combustion method for reducing carbon emissions by using traditional Chinese medicine residue as a substitute fuel, as described in claim 6, is characterized in that: The adjustment process in step (5.2) is as follows: when the H2 content decrease rate is >5% or the H2 content fluctuation exceeds the preset threshold, the amount of catalyst added is increased to 105%~110% of the original amount, and the pyrolysis temperature is increased by 10~20°C. The adjustment process in step (5.3) is as follows: when the temperature field fluctuation of the decomposition furnace or pre-combustion chamber is monitored to be >±10 °C, the total fuel addition is 103~105% of the original addition. The total fuel is obtained by mixing modified pyrolysis semi-coke, conventional alternative fuel and coal in step (4). The adjustment process in step (5.4) is as follows: NO x When the concentration increase rate is >10% and other operating conditions are normal, the injection rate of hydrogen-rich pyrolysis gas is increased by 101%~102% of the original amount, the amount of coal used in the fuel is reduced, and the amount of conventional alternative fuel added is increased to 105~110% of the original amount.

8. The catalytic pyrolysis-cascade combustion method for reducing carbon emissions by replacing traditional Chinese medicine residue with fuel according to claim 7, characterized in that: In step (5), the model used for intelligent closed-loop control is a discrete state-space model, and the specific formula is as follows: X(k+1)=AX(k)+BU(k) Y(k)=CX(k) In the formula, X(k) = , X(k) This represents the system state vector, including the current temperature and gas concentration in the decomposer or pre-combustion chamber; This indicates the volume fraction of H2 in the hydrogen-rich pyrolysis gas. This indicates the molar ratio of H2 to CO in the hydrogen-rich pyrolysis gas; This indicates the calorific value of the modified pyrolysis semi-coke, expressed in MJ / kg. This indicates the temperature inside the decomposition furnace or pre-combustion chamber; This indicates the NO content in the flue gas exiting the decomposition furnace or pre-combustion chamber. x concentration; This indicates the O2 concentration at the outlet of the decomposition furnace or pre-combustion chamber; This represents the current control command correction vector; where, This indicates the correction amount for the pyrolysis temperature setpoint, in °C. This indicates the catalyst dosing acceleration setpoint, in kg / h. This indicates the opening degree of the distribution valve for hydrogen-rich pyrolysis gas and modified pyrolysis semi-coke; This indicates the set value for the blending ratio of modified pyrolysis semi-coke and coal, with a ratio of 1. This represents the key output vector, including H2 content, furnace temperature, and NO in the outlet flue gas. x concentration, Variables that require precise control; The coefficient matrix representing the system model is obtained through system identification methods, trained based on historical operational data. k This is the index for the current time. Set the constraints as follows: Pyrolysis temperature constraint: T 热解-min ≤ T base + ≤ T 热解-max In the formula, T min and T max T represents the minimum and maximum pyrolysis temperatures. base This is the set pyrolysis temperature reference value; Catalyst head rate constraint: 0 ≤ ≤ In the formula, This represents the maximum feed rate of the catalyst feeder; Distributor valve opening constraints: 0 ≤ ≤ 100 Constraints on the blending ratio of modified pyrolytic semi-coke and coal: r min ≤ ≤ r max In the formula, r min For the minimum blending ratio, r max This is the maximum blending ratio; Temperature constraints in the decomposition furnace or pre-combustion chamber: T 内-min ≤ ≤ T 内-max In the formula, T 内-min The minimum permissible temperature in the decomposition furnace or pre-combustion chamber, r max This refers to the maximum permissible temperature in the decomposition furnace or pre-combustion chamber. NO in exhaust gas x Concentration constraint: 0 ≤ ≤ NOx- limit In the formula, NOx- limit The preset NOx emission limit.

9. The catalytic pyrolysis-cascade combustion method for reducing carbon emissions by replacing traditional Chinese medicine residue with fuel according to claim 8, characterized in that: Based on the above model, the following objective function is used for optimization: J ( k )= + + λ·P NOx ( k ) The above objective function Used to quantify the quality of system operation; the smaller the value, the better the control effect; objective function It includes the following three parts: Part One For tracking error term, where To predict the time domain, Indicates the current moment Predicted future The output vector at time step includes the H2 content of the pyrolysis gas. Temperature of the decomposition furnace or pre-combustion chamber NO from exhaust gas x concentration , For the corresponding target value vector, The output weight matrix is ​​used to set the importance of each indicator and measure the degree to which the system output deviates from the target. Part Two To control for smooth terms, among which To control the time domain, Indicates the future The changes in control commands at any given time include pyrolysis temperature correction, catalyst injection acceleration rate, coke distribution valve opening, and blending ratio setpoint. To control the weight matrix, a smoothing term is used to limit the intensity of the control actions and prevent system oscillations. Part Three For source nitrogen suppression, among which As a penalty factor, NO based on current operating conditions x Generate a potential function so that the system can predict NO in advance. x Risk of exceeding standards and proactive adjustment of combustion strategy; By solving in each control cycle The minimum control command sequence enables dynamic optimization among pursuing the target, stable regulation, and source nitrogen suppression, thereby minimizing fossil fuel consumption and pollutant emissions while ensuring clinker quality.

10. The catalytic pyrolysis-cascade combustion method for reducing carbon emissions by replacing traditional Chinese medicine residue with fuel according to claim 1, characterized in that: In step (6), the mass substitution ratio of the ash residue for clay raw materials is 3% to 10%.

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