A gasification hot blast stove dual fuel blending system and control method

Abstract

The application provides a gasification hot blast furnace dual-fuel blending system and a control method, and belongs to the technical field of energy and environmental protection. The system comprises a fuel gas buffer tank, an analysis and detection unit, a flow detection unit, a flow regulation unit and a PLC control unit. The fuel gas buffer tank inlet is connected with two gas sources of liquid nitrogen washing tail gas and natural gas, and the outlet mixed fuel gas is analyzed in real time by the analysis and detection unit. The PLC control unit receives the real-time heat value, compares it with the preset target heat value, dynamically adjusts the opening degree of the two gas source regulating valves through the built-in PID algorithm and proportional control logic, realizes closed-loop control, and ensures that the natural gas flow is not lower than the minimum guaranteed flow. The method comprises the steps of parameter presetting, pre-charging and purging, gas blending, real-time closed-loop control and safety shutdown. The application solves the problems of low heat value and large fluctuation of liquid nitrogen washing tail gas, realizes automatic and accurate blending with natural gas, outputs mixed fuel with stable heat value, and ensures the safe, stable and efficient operation of the coal grinding system.

Description

Technical Field

[0001] This invention relates to the field of energy and environmental protection technology, specifically to a dual-fuel co-firing system and control method for a gasification hot blast stove. Background Technology

[0002] In modern coal chemical production processes, raw coal needs to be ground. Specifically, the raw coal in the storage silo is metered by a vibrating hopper and a weighing feeder and then sent to a coal mill. After being ground by the mill's grinding rollers, it is dried by hot inert gas at 150℃~300℃ and blown to a rotary separator at the top of the mill for screening. Fine powder is blown to a pulverized coal bag filter, while coarse pulverized coal falls back under the grinding rollers for re-grinding. The hot inert gas is circulated among the coal mill, pulverized coal bag filter, and inert gas generator via a circulating fan. The heat for heating the pulverized coal comes from the inert gas generator. Inside the inert gas generator, fuel gas is burned with a matched ratio of combustion air (sent by a combustion air blower) and mixed with the circulating inert gas from the circulating fan. The outlet temperature is 150℃~300℃, and the temperature of the inert gas containing fine pulverized coal leaving the coal mill is controlled at around 105℃.

[0003] During the circulation process, inert gases need to be separated in a liquid nitrogen pool before re-entering the inert gas generator. Utilizing the boiling point differences of gases such as CO, CH4, and H2, they are condensed and separated from the coal gas. The tail gas after separation is called liquid nitrogen wash tail gas, which mainly consists of CO, H2, CH4, Ar, and N2. It does not contain oxygen or sulfides and is a clean combustible gas.

[0004] In existing technologies, liquid nitrogen scrubbing exhaust gas is usually used as the fuel source for inert gas generators. However, its volume and calorific value are insufficient to support the load of the inert gas generator alone. Therefore, natural gas needs to be introduced as a supplementary fuel.

[0005] Currently, common blending methods mostly employ fixed-ratio blending or simple manual adjustment. This method has significant drawbacks: First, it cannot respond to real-time changes in the flow rate and calorific value of liquid nitrogen wash tail gas, resulting in large fluctuations in the total calorific value of the mixed fuel gas; second, calorific value fluctuations are directly transmitted to the inert gas generator, making outlet temperature control difficult and affecting the coal milling drying effect and the stability of pulverized coal quality. Summary of the Invention

[0006] In view of the above situation and to overcome the defects of the prior art, the purpose of the present invention is to provide a dual-fuel co-firing system and control method for a gasification hot blast stove, so as to at least partially solve the problems mentioned in the background art.

[0007] The technical solution adopted by this invention is as follows: The first aspect proposes a dual-fuel co-firing system for a gasification hot blast stove, comprising: The fuel gas buffer tank has its inlet connected to a liquid nitrogen scrubbing tail gas source and a natural gas source via pipelines. The analysis and detection unit has its sampling port connected to the outlet pipeline of the fuel gas buffer tank, and is used to analyze and calculate the calorific value of the mixed fuel gas in real time. A flow detection unit is used to detect the flow rate of liquid nitrogen wash tail gas and the flow rate of natural gas input into the fuel gas buffer tank, respectively. The flow regulation unit includes a first regulating valve installed on the liquid nitrogen wash tail gas pipeline and a second regulating valve installed on the natural gas pipeline; The PLC control unit is connected to the analysis and detection unit, the flow detection unit, and the flow regulation unit respectively. The PLC control unit is configured to: receive the real-time calorific value of the mixed fuel gas, compare it with the preset target calorific value, and dynamically adjust the opening of the first regulating valve and the second regulating valve by outputting control signals through the built-in PID algorithm and proportional control logic, so as to maintain the real-time calorific value stable near the target calorific value.

[0008] In a preferred embodiment, the volume of the fuel gas buffer tank is designed to be 15m³ to 20m³.

[0009] In a preferred embodiment, the analysis and detection unit is an analysis cabin, which houses a gas component analyzer and a calorific value calculator; The gas component analyzer is used to detect the volume percentage of CO, CH4, and H2 in the mixed fuel gas; The calorific value calculator calculates the real-time calorific value based on the component content.

[0010] In a preferred embodiment, the flow detection unit includes a first flow meter and a second flow meter; The first flow meter is installed in the liquid nitrogen wash tail gas pipeline to detect the flow rate of the liquid nitrogen wash tail gas in the fuel gas buffer tank; The second flow meter is installed in the natural gas pipeline to detect the natural gas flow rate.

[0011] In a preferred embodiment, the adjustment logic of the PLC control unit further includes: when it is necessary to increase the real-time calorific value, while increasing the opening of the second regulating valve, ensuring that the natural gas flow rate is not lower than a preset minimum guaranteed flow rate value.

[0012] A second aspect of this invention provides a method for controlling the tail gas of a gasification hot blast stove co-firing liquid nitrogen scrubbing, based on the above-described system implementation, including the following steps: Parameter preset: Set the target calorific value of the mixed fuel gas and the minimum guaranteed flow rate of natural gas in the PLC control unit; Gas blending and regulation: Open the first and second regulating valves to allow liquid nitrogen wash tail gas and natural gas to enter the fuel gas buffer tank for blending; Real-time closed-loop control: The real-time calorific value of the mixed fuel gas is obtained through the analysis and detection unit; the PLC control unit compares the real-time calorific value with the target calorific value, and adjusts the opening of the first regulating valve and the second regulating valve in a coordinated manner based on the comparison result, so that the real-time calorific value approaches the target calorific value, and ensures that the natural gas flow rate is not lower than the minimum guaranteed flow rate when the natural gas flow rate is increased.

[0013] As a preferred embodiment, the gas mixing and regulation are further included in a pre-charge purging step: natural gas is first introduced into the system to a set pressure, the pipeline is purged, and then liquid nitrogen is introduced to wash the tail gas.

[0014] In a preferred embodiment, the target calorific value is set to 2500 kcal / Nm³, and the minimum guaranteed flow rate is set to 300 Nm³ / h.

[0015] In a preferred embodiment, the PLC control unit uses a PID control algorithm combined with proportional coefficient adjustment to generate valve adjustment commands.

[0016] As a preferred embodiment, the system also includes a shutdown procedure: first, close the first regulating valve to maintain natural gas flow and purge residual liquid nitrogen wash tail gas from the system; then, close the second regulating valve; and finally, depressurize the fuel gas buffer tank to ensure system safety.

[0017] Beneficial effects: 1. Through a closed-loop automatic control system, the low-calorific-value, volatile liquid nitrogen scrubbing tail gas, which is difficult to use directly and is often vented or treated inefficiently, is converted into stable and reliable fuel gas, and replaces part of the natural gas consumption, achieving significant energy-saving benefits.

[0018] 2. By implementing detection, intelligent calculation, and closed-loop regulation, the calorific value deviation of the output mixed fuel gas is ensured to always be within the preset range, reducing the temperature fluctuation at the outlet of the inert gas generator, thereby improving the coal drying effect and the stability of pulverized coal quality. Attached Figure Description Figure 1 This is a schematic diagram illustrating the structure and control principle of the dual-fuel co-firing system for a gasification hot blast stove provided in an embodiment of the present invention; Figure 2 A flowchart of the control method provided in an embodiment of the present invention; Figure 3 This is a logic block diagram of the PLC control unit performing closed-loop regulation in an embodiment of the present invention.

[0019] in, 101. Fuel gas buffer tank; 102. Analytical cabin; 103. First flow meter; 104. First regulating valve; 105. Second flow meter; 106. Second regulating valve; 107. PLC control unit; 108. Liquid nitrogen wash tail gas source; 109. Natural gas source; 110. Inert gas generator.

[0020] The accompanying drawings are provided to further understand the embodiments and form part of the specification. They are used together with the embodiments for explanation and do not constitute a limitation on the embodiments. Detailed Implementation

[0021] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection.

[0022] In the description of the embodiments, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. They are only for the convenience of describing the embodiments and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments.

[0023] like Figure 1 As shown, a preferred embodiment of the gasification hot blast stove dual-fuel co-firing system of the present invention mainly includes the following parts: The fuel gas buffer tank 101, serving as a buffer and mixing device, has a volume between 15-20 m³, specifically 17 m³, and an operating pressure range of 0.3-0.6 MPa. The tank's inlet flange pipes are connected to a liquid nitrogen scrubbing tail gas source 108 and a natural gas source 109, respectively. The tank's outlet main pipe is connected to an inert gas generator 110. A safety valve and a vent valve are also installed on the tank.

[0024] The analysis and testing unit is housed in an analysis cabin 102. Inside, a gas component analyzer and a calorific value calculator are installed. The analyzer is connected to the outlet pipe of the fuel gas buffer tank 101 via a sampling tube running through the cabin, and is used for online monitoring of the volume fractions of H2, CH4, CO, and O2 in the mixed fuel gas. The calorific value calculator calculates the calorific value of the mixed fuel gas based on real-time component data.

[0025] The flow detection unit includes a first flow meter 103 and a second flow meter 105. The first flow meter 103 is installed in the liquid nitrogen wash tail gas pipeline and is used to detect the flow rate of the liquid nitrogen wash tail gas entering the fuel gas buffer tank 101. The second flow meter 105 is installed in the natural gas pipeline and is used to detect the flow rate of the natural gas entering the fuel gas buffer tank 101.

[0026] The flow regulation unit includes a first regulating valve 104 and a second regulating valve 106. The first regulating valve 104 is installed on the liquid nitrogen wash tail gas pipeline to precisely control the input amount of liquid nitrogen wash tail gas. The second regulating valve 106 is located on the natural gas pipeline and works in conjunction with the first regulating valve 104 to achieve dynamic closed-loop control of dual-fuel ratio.

[0027] The PLC control unit 107 is a modular PLC control unit that is connected to the analysis and detection unit, the flow detection unit, and the flow regulation unit respectively. As the control core of the system, it receives the real-time calorific value signal transmitted by the analysis and detection unit and the two gas source flow signals detected by the flow detection unit. It compares the real-time calorific value with the preset target calorific value and, through the built-in PID algorithm and proportional control logic, outputs control signals to dynamically adjust the opening of the first regulating valve 104 and the second regulating valve 106 to maintain the real-time calorific value stable near the target calorific value. Meanwhile, the PLC control unit 107 also has built-in safety control logic to realize functions such as pre-charge purging, emergency shutdown, and minimum flow guarantee of the system, so as to ensure the safe operation of the system.

[0028] In addition, the adjustment logic of the PLC control unit 107 also includes: when it is necessary to increase the real-time calorific value, while increasing the opening of the second regulating valve 106, ensuring that the natural gas flow rate is not lower than a preset minimum guaranteed flow rate value.

[0029] The purpose of this setup is to prevent a sudden drop in calorific value due to instantaneous interruption or fluctuation of natural gas, which could lead to furnace flameout or unstable combustion. At the same time, when the composition of the liquid nitrogen wash tail gas fluctuates significantly, maintaining a minimum natural gas base flow rate provides a stable combustible baseline for the system, ensuring the continuity and safety of the co-firing process.

[0030] Through a closed-loop automatic control system, the low-calorific-value, volatile liquid nitrogen scrubbing tail gas, which is difficult to use directly and is often vented or inefficiently treated, is converted into stable and reliable fuel gas, replacing part of the natural gas consumption and achieving significant energy-saving benefits.

[0031] like Figure 2 and Figure 3 As shown, this embodiment provides a control method based on the above system, including the following steps: Parameter preset S01: The operator sets the target calorific value of the mixed fuel gas and the minimum guaranteed flow rate of natural gas in the PLC control unit 107. Specifically, the target calorific value is set to 2500 kcal / Nm³, and the minimum guaranteed flow rate is set to 300 Nm³ / h.

[0032] Gas blending and regulation S02: Open the first regulating valve 104 and the second regulating valve 106 to allow the liquid nitrogen wash tail gas and natural gas to enter the fuel gas buffer tank 101 for convection and blending according to the initial ratio. The liquid nitrogen wash tail gas and natural gas are fully mixed in the fuel gas buffer tank 101 and then enter the inert gas generator 110 for combustion through the outlet.

[0033] The PLC control unit 107 acquires data from two flow meters and component signals from the online analyzer in real time, and dynamically calculates the current calorific value deviation.

[0034] Real-time closed-loop control S04: The real-time calorific value of the mixed fuel gas is obtained by the analysis and detection unit. The PLC control unit 107 compares the real-time calorific value with the target calorific value, calculates the calorific value deviation, and adjusts the opening of the first regulating valve 104 and the second regulating valve 106 in a coordinated manner based on the comparison result, so that the real-time calorific value approaches the target calorific value, and ensures that the natural gas flow rate is not lower than the minimum guaranteed flow rate when the natural gas flow rate is increased.

[0035] Specifically: The real-time calorific value is compared with the preset target calorific value (2500 kcal / Nm³), and the calorific value deviation e (e = real-time calorific value - target calorific value) is calculated. Based on the calorific value deviation e, the control signal is output through the built-in PID control algorithm and proportional control logic to dynamically adjust the opening degree of the first regulating valve 104 and the second regulating valve 106. The specific adjustment logic is as follows: (1) When e < -50 (real-time calorific value is lower than target calorific value): This indicates that the proportion of liquid nitrogen washing tail gas is too large or the calorific value of the tail gas itself is too low, resulting in insufficient calorific value of the mixed fuel gas; at this time, the PLC control unit 107 controls the opening of the first regulating valve 104 to decrease (reduce the flow rate of liquid nitrogen washing tail gas), and at the same time controls the opening of the second regulating valve 106 to increase (increase the flow rate of natural gas); during the adjustment process, the PLC control unit 107 continuously monitors the natural gas flow rate detected by the second flow meter 105 to ensure that the natural gas flow rate is not lower than the preset minimum guaranteed flow rate (300 Nm³ / h); if the real-time calorific value is still lower than the target calorific value after the natural gas flow rate reaches the minimum guaranteed flow rate, the PLC control unit 107 issues an alarm signal to remind the operator to check the composition and flow rate of the liquid nitrogen washing tail gas, and start the emergency handling procedure if necessary; (2) When e>50 (real-time calorific value is higher than target calorific value): This indicates that the proportion of liquid nitrogen washing tail gas is too small or the calorific value of the tail gas itself is too high, resulting in the calorific value of the mixed fuel gas being too high. At this time, the PLC control unit 107 controls the opening of the first regulating valve 104 to increase (increase the flow rate of liquid nitrogen washing tail gas), and at the same time controls the opening of the second regulating valve 106 to decrease (decrease the flow rate of natural gas). During the adjustment process, the PLC control unit 107 continuously monitors the flow rate of liquid nitrogen washing tail gas detected by the first flow meter 103 to avoid the sudden increase in the flow rate of liquid nitrogen washing tail gas causing excessive fluctuations in system pressure. (3) When |e|≤50 kcal / Nm³ (the deviation between the real-time calorific value and the target calorific value is within the allowable range): it indicates that the calorific value of the mixed fuel gas meets the requirements. The PLC control unit 107 maintains the current opening of the first regulating valve 104 and the second regulating valve 106, keeps the flow of the two gas sources stable, and ensures that the calorific value of the mixed fuel gas is stable near the target value. The above adjustment process continues, forming a closed-loop control to ensure that the real-time calorific value of the mixed fuel gas remains stable near the target value (with an allowable deviation of ±50 kcal / Nm³).

[0036] Specifically, before gas mixing and regulation, a pre-charge purging S03 step is included: first, natural gas is introduced into the system to the set pressure, the pipeline is purged, and then liquid nitrogen is introduced to wash the tail gas.

[0037] Furthermore, in real-time closed-loop control, the PLC control unit 107 uses a PID control algorithm combined with proportional coefficient adjustment to generate valve adjustment commands.

[0038] Furthermore, the control method also includes a shutdown step S05: first, close the first regulating valve 104 to maintain natural gas flow and purge residual liquid nitrogen wash tail gas in the system; then close the second regulating valve 106; finally, depressurize the fuel gas buffer tank 101 to ensure system safety.

[0039] By implementing detection, intelligent calculation, and closed-loop regulation, the calorific value deviation of the output mixed fuel gas is ensured to always be within the preset range, reducing the temperature fluctuation at the outlet of the inert gas generator 110, thereby improving the coal drying effect and the stability of pulverized coal quality.

[0040] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0041] The embodiments have been described above, and such description is not restrictive. The figures shown are only one embodiment, and the actual structure is not limited to this. In short, if a person skilled in the art is inspired by this description and designs a similar structure and embodiment without departing from the inventive spirit, such design should fall within the scope of protection.

Claims

1. A dual-fuel co-firing system for a gasification hot blast stove, characterized in that, include: The fuel gas buffer tank has its inlet connected to a liquid nitrogen scrubbing tail gas source and a natural gas source via pipelines. The analysis and detection unit has its sampling port connected to the outlet pipeline of the fuel gas buffer tank for real-time detection of the calorific value of the mixed fuel gas. A flow detection unit is used to detect the flow rate of liquid nitrogen wash tail gas and the flow rate of natural gas input into the fuel gas buffer tank, respectively. The flow regulation unit includes a first regulating valve installed on the liquid nitrogen wash tail gas pipeline and a second regulating valve installed on the natural gas pipeline; The PLC control unit is connected to the analysis and detection unit, the flow detection unit, and the flow regulation unit respectively. The PLC control unit is configured to: receive the real-time calorific value of the mixed fuel gas, compare it with the preset target calorific value, and dynamically adjust the opening degree of the first regulating valve and the second regulating valve by outputting control signals through the built-in PID algorithm and proportional control logic.

2. The dual-fuel co-firing system for a gasification hot blast stove according to claim 1, characterized in that, The fuel gas buffer tank is designed to have a volume of 15m³ to 20m³.

3. The dual-fuel co-firing system for a gasification hot blast stove according to claim 1, characterized in that, The analysis and detection unit is an analysis cabin, which contains a gas component analyzer and a calorific value calculator. The gas component analyzer is used to detect the volume percentage of CO, CH4, and H2 in the mixed fuel gas; The calorific value calculator calculates the real-time calorific value based on the component content.

4. The dual-fuel co-firing system for a gasification hot blast stove according to claim 1, characterized in that, The flow detection unit includes a first flow meter and a second flow meter; The first flow meter is installed in the liquid nitrogen wash tail gas pipeline to detect the flow rate of the liquid nitrogen wash tail gas in the fuel gas buffer tank; The second flow meter is installed in the natural gas pipeline to detect the natural gas flow rate.

5. The dual-fuel co-firing system for a gasification hot blast stove according to claim 1, characterized in that, The adjustment logic of the PLC control unit also includes: when it is necessary to increase the real-time calorific value, while increasing the opening of the second regulating valve, ensuring that the natural gas flow rate is not lower than a preset minimum guaranteed flow rate value.

6. A method for controlling the tail gas from a gasification hot blast stove co-firing with liquid nitrogen, implemented based on the system described in any one of claims 1-5, characterized in that, Includes the following steps: Parameter preset: Set the target calorific value of the mixed fuel gas and the minimum guaranteed flow rate of natural gas in the PLC control unit; Gas blending and regulation: Open the first and second regulating valves to allow liquid nitrogen wash tail gas and natural gas to enter the fuel gas buffer tank for blending; Real-time closed-loop control: The real-time calorific value of the mixed fuel gas is obtained through the analysis and detection unit; the PLC control unit compares the real-time calorific value with the target calorific value, and adjusts the opening of the first regulating valve and the second regulating valve in a coordinated manner based on the comparison result, so that the real-time calorific value approaches the target calorific value, and ensures that the natural gas flow rate is not lower than the minimum guaranteed flow rate when the natural gas flow rate is increased.

7. The method for controlling the tail gas of a gasification hot blast stove co-firing with liquid nitrogen as described in claim 6, characterized in that, Before the gas mixing and regulation, a pre-charge and purging step is also included: first, natural gas is introduced into the system to the set pressure, the pipeline is purged, and then liquid nitrogen is introduced to wash the tail gas.

8. The method for controlling the tail gas of a gasification hot blast stove co-firing with liquid nitrogen as described in claim 6, characterized in that, The target calorific value is set at 2500 kcal / Nm³, and the minimum guaranteed flow rate is set at 300 Nm³ / h.

9. The method for controlling the tail gas of a gasification hot blast stove co-firing with liquid nitrogen as described in claim 6, characterized in that, In the real-time closed-loop control, the PLC control unit uses a PID control algorithm combined with proportional coefficient adjustment to generate valve adjustment commands.

10. The method for controlling the tail gas of a gasification hot blast stove co-firing with liquid nitrogen as described in claim 6, characterized in that, The shutdown procedure also includes: first, closing the first regulating valve to maintain natural gas flow and purge residual liquid nitrogen wash tail gas from the system; then closing the second regulating valve; and finally depressurizing the fuel gas buffer tank to ensure system safety.

Images