A control system for the differential pressure of the solid heat carrier furnace bed

Abstract

The present invention belongs to the technical field of waste pyrolysis, and particularly relates to a control system for the differential pressure of the furnace bed of a solid heat carrier furnace. The controller is connected to a flue gas induced draft fan, a return material unit, a solid heat carrier furnace, a fuel system, a slag discharge unit, and a primary blower; the flue gas induced draft fan is connected to a cyclone separator; the waste feeding unit is connected to the pyrolysis unit; the solid heat carrier furnace is connected to the cyclone separator; the solid heat carrier furnace is connected to the slag discharge unit; the solid heat carrier furnace is connected to the return material unit; the cyclone separator is connected to the pyrolysis unit; the pyrolysis unit is connected to the return material unit; both the primary blower and the fuel system are connected to the burner of the solid heat carrier furnace. Under the condition of fine-tuning the return material unit, by controlling the air supply volume of the primary blower of the burner at the bottom of the solid heat carrier furnace and the fuel quantity of the fuel system, and cooperating with the intermittent start-stop and adjustment of the operating frequency of the slag discharge unit, this control system well realizes the automatic stable control of the bed differential pressure.

Description

Technical Field

[0001] The present invention belongs to the technical field of waste pyrolysis, and particularly relates to a control system for the differential pressure of the bed layer of a solid heat carrier furnace. Background Art

[0002] The advantages of waste pyrolysis gasification technology, such as no secondary pollution emissions and waste resource utilization, have less environmental and social impact compared to large-scale landfill, incineration plant and other waste treatment facilities. It can weaken the difficulties of government transportation and site selection, and the government guidance is more efficient and convenient. It can more timely and thoroughly solve the problem of urban domestic waste treatment. Therefore, waste pyrolysis gasification technology is expected to become a new technical direction to replace waste incineration.

[0003] The main equipment in the waste pyrolysis gasification process includes a solid heat carrier furnace, a pyrolysis reaction unit, a return material unit and a slag discharge unit.

[0004] After heating the solid heat carrier using the solid heat carrier furnace, the high-temperature flue gas carries the high-temperature heat carrier into the cyclone separator. The separated high-temperature solid heat carrier is sent to the pyrolysis unit. The heat carrier serves as a heat source to pyrolyze and gasify the waste in the pyrolysis unit. After the reaction ends and the temperature drops, the heat carrier and pyrolysis residues are sent back into the solid heat carrier furnace through the return material unit for reheating. The heat carrier is reheated in the furnace and then enters the cycle for reuse. The combustible components in the pyrolysis residues are heated and burned in the furnace. The large non-combustible pyrolysis residues can be discharged through the slag discharge port of the heat carrier furnace to the slag discharge unit.

[0005] The solid heat carrier furnace among them is in the form of a circulating fluidized bed. The traditional circulating fluidized bed bed pressure control mainly adjusts the slag discharge unit to achieve stable bed pressure. The bed layer thickness is basically proportional to the bed pressure. Bottom slag discharge is a common method to adjust the bed layer pressure drop. The task of the bed pressure control system is to maintain the bed material thickness at an appropriate value by adjusting the slag discharge amount. When using regular slag discharge, the bed pressure value for starting and stopping the bottom slag discharge device is set in the control system to control the bed pressure within a certain range.

[0006] The use of the solid heat carrier furnace in the waste pyrolysis process is different from that of the traditional circulating fluidized bed. The circulating amount of the solid heat carrier in the furnace can be adjusted through the return material unit. In addition to the slag discharge process that can affect the bed pressure, external conditions such as furnace temperature, primary air volume and the return speed of the return material unit can also affect the bed layer differential pressure. Therefore, simply controlling the slag discharge speed and frequency cannot effectively control the differential pressure of the solid heat carrier furnace, and all influencing factors in the process need to be considered. Summary of the Invention

[0007] The purpose of the present invention is to provide a control system for the differential pressure of the bed layer of a solid heat carrier furnace, which not only takes into account the control function of the fluidized bed bed pressure but also is applicable to the system characteristics of the waste pyrolysis process.

[0008] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0009] A control system for the differential pressure of the bed layer of a solid heat carrier furnace, comprising a flue gas induced draft fan, a cyclone separator, a controller, a waste feeding unit, a pyrolysis unit, a return feeding unit, a primary blower, a fuel system, a slag discharging unit, and a solid heat carrier furnace; the controller is connected to the flue gas induced draft fan, the return feeding unit, the solid heat carrier furnace, the fuel system, the slag discharging unit, and the primary blower; the flue gas induced draft fan is connected to the cyclone separator; the waste feeding unit is connected to the pyrolysis unit; the solid heat carrier furnace is connected to the cyclone separator; the solid heat carrier furnace is connected to the slag discharging unit; the solid heat carrier furnace is connected to the return feeding unit; the cyclone separator is connected to the pyrolysis unit; the pyrolysis unit is connected to the return feeding unit; both the primary blower and the fuel system are connected to the burner of the solid heat carrier furnace.

[0010] The hot flue gas generated after combustion brings the solid heat carrier of the solid heat carrier furnace into the cyclone separator, the high-temperature flue gas enters the flue gas system through the flue gas induced draft fan, the separated solid heat carrier enters the pyrolysis unit, and at the same time the waste feeding unit feeds the waste into the pyrolysis unit. After pyrolysis, the solid heat carrier mixed with the pyrolysis residue enters the return feeding unit and is transported into the solid heat carrier furnace again through the return feeding unit. The combustible substances in the pyrolysis residue will burn in the solid heat carrier furnace, and the incombustible substances remain on the bed layer.

[0011] The signals of the pressure measuring point PT1 in the dense phase region, the pressure measuring point PT2 in the dilute phase region, and the furnace temperature measuring point TT1 on the solid heat carrier furnace are connected to the controller, and at the same time the controller outputs control signals to the flue gas induced draft fan, the return feeding unit, the primary blower, the fuel system, and the slag discharging unit.

[0012] The control method is as follows:

[0013] A. By adjusting the frequency of the flue gas induced draft fan, the pressure PT2 in the dilute phase region in the solid heat carrier furnace is stabilized. The frequency of the flue gas induced draft fan and the pressure form a PID regulation single loop. When the frequency increases, the pressure decreases, and when the frequency decreases, the pressure increases;

[0014] B. The operating frequency of the return feeding unit affects the amount of heat carrier and reaction residue entering the solid heat carrier furnace. The faster the frequency, the more materials, and the slower the frequency, the less materials; under the condition that other working conditions remain unchanged, the more materials enter the solid heat carrier furnace, the greater PT1 is, and the less materials enter the solid heat carrier furnace, the smaller PT1 will be; therefore, the operating frequency of the return feeding unit affects the magnitude of the pressure PT1 in the dense phase region. Under the condition that the pressure PT2 in the dilute phase region is stable, the operating frequency of the return feeding unit is an influencing factor for the bed layer differential pressure ΔP; when the system operates stably, the operating frequency of the return feeding unit is based on a fixed frequency or a manual fine-tuning state, and in this working condition, the influence of the return feeding unit on the bed layer differential pressure can be ignored;

[0015] C. During the heating process of the solid heat carrier, in order to ensure the fluidization of the heat carrier in the furnace, the minimum operating frequency of the primary blower is set to F 鼓 ; As the furnace temperature TT1 increases, with the primary blower frequency unchanged, the flue gas volume will increase accordingly, which leads to an increase in the heat carrier circulation volume. The amount of heat carrier carried away by the high-temperature flue gas within the same time interval is constantly increasing; during the automatic regulation process of the bed differential pressure ΔP, to maintain the stability of the bed differential pressure, for every T1 increase in TT1, the fuel supply Q of the bottom burner is reduced once 燃 , until TT1 returns to the temperature range required by the process system; conversely, if the furnace temperature decreases, the fuel supply Q fuel should be increased according to the temperature change until TT1 returns to the temperature range required by the process system; while the temperature is stable, if the bed pressure is too high, the primary blower frequency can be increased, and if the bed pressure is too low, the primary blower frequency can be reduced, with the minimum reduction being the minimum operating frequency F 鼓 ;

[0016] D. If the operation is carried out according to step C, the furnace temperature is constantly increasing, and at the same time, the bed pressure is also constantly rising. After increasing the primary blower frequency, there is no obvious decrease in the bed pressure, which indicates that the large-particle-size materials in the bed material increase. The drive motor of the slag discharge unit is frequency-controlled, and the slag discharge unit is started at 5Hz to discharge the large-particle-size materials from the bed layer; by adjusting the slag discharge unit to slowly discharge the residue, when the bed pressure returns to the reasonable range, the slag discharge unit is stopped.

[0017] The beneficial effects achieved by the present invention are as follows:

[0018] The control system of the present invention is composed of a flue gas induced draft fan, a return material unit, a primary fan, a fuel system, a slag discharge unit, etc. By adjusting the frequency of the flue gas induced draft fan through the control system, the stability of the furnace pressure of the solid heat carrier furnace is achieved. Under the fine adjustment of the return material unit, by controlling the air supply volume of the primary fan of the bottom burner of the solid heat carrier furnace and the fuel volume of the fuel system, and cooperating with the intermittent start-stop and adjustment of the operating frequency of the slag discharge unit, the control system well realizes the automatic stable control of the bed differential pressure. Description of the Drawings

[0019] Figure 1 It is a structural diagram of the control system for the bed differential pressure of the solid heat carrier furnace. Detailed Embodiments

[0020] The present invention will be described in detail below with reference to the drawings and specific embodiments.

[0021] Such as Figure 1As shown in the figure, the control system for the differential pressure of the solid heat carrier furnace bed layer of the present invention includes a flue gas induced draft fan, a cyclone separator, a controller, a waste feeding unit, a pyrolysis unit, a return feeding unit, a primary blower, a fuel system, a slag discharging unit, and a solid heat carrier furnace. The controller is connected to the flue gas induced draft fan, the return feeding unit, the solid heat carrier furnace, the fuel system, the slag discharging unit, and the primary blower; the flue gas induced draft fan is connected to the cyclone separator; the waste feeding unit is connected to the pyrolysis unit; the solid heat carrier furnace is connected to the cyclone separator; the solid heat carrier furnace is connected to the slag discharging unit; the solid heat carrier furnace is connected to the return feeding unit; the cyclone separator is connected to the pyrolysis unit; the pyrolysis unit is connected to the return feeding unit; both the primary blower and the fuel system are connected to the burner of the solid heat carrier furnace.

[0022] The hot flue gas generated after combustion brings the solid heat carrier on the solid heat carrier bed layer into the cyclone separator. The high-temperature flue gas enters the flue gas system through the flue gas induced draft fan. The separated solid heat carrier enters the pyrolysis unit. At the same time, the waste feeding unit sends waste into the pyrolysis unit. After pyrolysis, the solid heat carrier mixed with the pyrolysis residue enters the return feeding unit and is transported into the solid heat carrier furnace again through the return feeding unit. The combustible substances in the pyrolysis residue will burn in the solid heat carrier furnace, and the incombustible substances remain on the bed layer.

[0023] The signals of the pressure measuring point 1 (PT1) in the dense phase area, the pressure measuring point 2 (PT2) in the dilute phase area, and the furnace temperature measuring point (TT1) on the solid heat carrier furnace are connected to the controller. At the same time, the controller can output control signals to the flue gas induced draft fan, the return feeding unit, the primary blower, the fuel system, and the slag discharging unit.

[0024] The control method is as follows:

[0025] A By adjusting the frequency of the flue gas induced draft fan, the pressure PT2 in the dilute phase area in the solid heat carrier furnace is stabilized. The frequency of the induced draft fan and the pressure form a PID adjustment single loop. When the frequency increases, the pressure decreases; when the frequency decreases, the pressure increases.

[0026] B The operating frequency of the return feeding unit affects the amount of heat carrier and reaction residue entering the solid heat carrier furnace. The faster the frequency, the more materials; the slower the frequency, the less materials. Under the condition that other operating conditions remain unchanged, the more materials enter the solid heat carrier furnace, the greater PT1 is; the less materials enter the solid heat carrier furnace, the smaller PT1 is. Therefore, the operating frequency of the return feeding unit affects the magnitude of the pressure PT1 in the dense phase area. Under the condition that the pressure PT2 in the dilute phase area is stable, the operating frequency of the return feeding unit is an influencing factor for the bed layer differential pressure ΔP. When the system operates stably, the operating frequency of the return feeding unit is based on a fixed frequency or manual fine-tuning state. In this case, the influence of the return feeding unit on the bed layer differential pressure can be ignored;

[0027] During the heating process of the solid heat carrier, in order to ensure the fluidization of the heat carrier in the furnace, the minimum operating frequency of the primary blower is set to F. 鼓 . As the furnace temperature TT1 increases, with the primary blower frequency remaining unchanged, the flue gas volume will increase accordingly, which leads to an increase in the heat carrier circulation volume. The amount of heat carrier carried away by the high-temperature flue gas within the same time interval is constantly increasing. During the automatic regulation process of the bed differential pressure ΔP to maintain the stability of the bed differential pressure, for every T1 increase in TT1, the fuel supply quantity Q of the bottom burner is reduced once. 燃 , until TT1 returns to the temperature range required by the process system. Conversely, if the furnace temperature decreases, the fuel supply quantity Q fuel should be increased according to the temperature change until TT1 returns to the temperature range required by the process system; while the temperature is stable, if the bed pressure is on the high side, the primary blower frequency can be increased, and if the bed pressure is on the low side, the primary blower frequency can be reduced, with the minimum reduction being the minimum operating frequency F. 鼓 .

[0028] D If the operation is carried out according to step (C), the furnace temperature is continuously increasing, and at the same time the bed pressure is also continuously rising. After increasing the primary blower frequency, there is no obvious decrease in the bed pressure, which indicates that the large-particle-size materials in the bed material have increased. The drive motor of the slag discharge unit is frequency-controlled. The slag discharge unit is started at 5 Hz to discharge the large-particle-size materials from the bed layer. By adjusting the slag discharge unit to slowly discharge the residue, when the bed pressure returns to the reasonable range, the slag discharge unit is stopped.

[0029] The solid heat carrier is heated in the solid heat carrier furnace. The high-temperature flue gas carries the solid heat carrier into the cyclone separator. The separated high-temperature solid heat carrier enters the pyrolysis unit. The low-temperature heat carrier and reaction residues after the reaction are sent into the solid heat carrier furnace through the return material unit. The bed differential pressure is the difference between the pressure in the dense phase area of the solid heat carrier furnace and the pressure in the dilute phase area of the solid heat carrier furnace. In this technical process, the control of the bed differential pressure in the solid heat carrier furnace is crucial. For the characteristics of the system process, the following control method is adopted for the bed differential pressure in the solid heat carrier furnace:

[0030] A By adjusting the frequency of the induced draft fan, the pressure in the dilute phase area of the solid heat carrier furnace is stabilized;

[0031] B By controlling the running frequency of the return material unit, the amount of heat carrier and reaction residues entering the solid heat carrier furnace is adjusted;

[0032] C Under the condition of full-load operation of the device, the control frequency of the return material unit is in a fixed or fine-tuning state;

[0033] During the circulation of the solid heat carrier, to ensure the fluidized circulation of the heat carrier, sufficient circulating air volume and furnace temperature should be ensured. As the furnace temperature rises, the flue gas volume generated under the same air volume is continuously increasing, which will lead to an increase in the circulating volume of the heat carrier in the furnace and affect the stability of the bed pressure. The furnace temperature is stabilized by controlling the fuel quantity, and at the same time, the bed pressure is stabilized by controlling the operating frequency of the primary air fan to reduce the fluctuation of the bed pressure.

[0034] E During the adjustment process, if the pressure in the dense phase zone of the solid heat carrier furnace and the furnace temperature continue to rise, it indicates that the amount of large non-combustible particles in the bed material increases, and the large-sized substances need to be discharged from the bottom bed layer of the furnace through the slag discharge unit.

Claims

1. A method for controlling the differential pressure of a solid heat carrier furnace bed, characterized in that: The method includes a control system for the differential pressure of the solid heat carrier furnace bed, which includes a flue gas induced draft fan, a cyclone separator, a controller, a waste feeding unit, a pyrolysis unit, a return feeding unit, a primary blower, a fuel system, a slag discharging unit, and a solid heat carrier furnace; the controller is connected to the flue gas induced draft fan, the return feeding unit, the solid heat carrier furnace, the fuel system, the slag discharging unit, and the primary blower; the flue gas induced draft fan is connected to the cyclone separator; the waste feeding unit is connected to the pyrolysis unit; the solid heat carrier furnace is connected to the cyclone separator; the solid heat carrier furnace is connected to the slag discharging unit; the solid heat carrier furnace is connected to the return feeding unit; the cyclone separator is connected to the pyrolysis unit; the pyrolysis unit is connected to the return feeding unit; both the primary blower and the fuel system are connected to the burner of the solid heat carrier furnace; The control method is as follows: A. By adjusting the frequency of the flue gas induced draft fan, the pressure PT2 in the dilute phase zone of the solid heat carrier furnace is stabilized. The frequency of the flue gas induced draft fan and the pressure form a PID regulation single loop. When the frequency increases, the pressure decreases; when the frequency decreases, the pressure increases; B. By controlling the running frequency of the return feeding unit, the amount of heat carrier and reaction residues entering the solid heat carrier furnace is adjusted. Under the condition of stable system operation, the running frequency of the return feeding unit is based on a fixed frequency or manual fine-tuning state. In this working condition, the influence of the return feeding unit on the bed differential pressure is negligible; C. During the heating process of the solid heat carrier, to ensure the fluidization of the heat carrier in the furnace, the minimum operating frequency of the primary blower is set to F 鼓 ; as the furnace temperature TT1 increases, with the primary blower frequency remaining unchanged, the flue gas volume will increase accordingly, which leads to an increase in the heat carrier circulation volume. The amount of heat carrier carried away by the high-temperature flue gas within the same time interval is constantly increasing; during the automatic regulation process of the bed differential pressure ΔP, to maintain the stability of the bed differential pressure, for every increase of T1 in TT1, the fuel supply quantity Q of the bottom burner is reduced once 燃 , until TT1 returns to the temperature range required by the process system; conversely, if the furnace temperature decreases, the fuel supply quantity Q should be increased according to the temperature change 燃 , until TT1 returns to the temperature range required by the process system; while the temperature is stable, if the bed pressure is too high, the primary blower frequency is increased, and if the bed pressure is too low, the primary blower frequency is decreased, and the minimum can be reduced to the minimum operating frequency F 鼓 ; D. If the operation is carried out according to step C, the furnace temperature continuously increases, and at the same time the bed pressure also continuously rises. If the bed pressure does not significantly decrease after increasing the frequency of the primary blower, it indicates that the large particle size materials in the bed material increase. The drive motor of the slag discharging unit is frequency-controlled. The slag discharging unit is started at 5Hz to discharge the large particle size materials from the bed layer; by adjusting the slag discharging unit to slowly discharge the residues, when the bed pressure returns to a reasonable range, the slag discharging unit is stopped; The signals of the pressure measuring point PT1 in the dense phase zone, the pressure measuring point PT2 in the dilute phase zone, and the furnace temperature measuring point TT1 on the solid heat carrier furnace are connected to the controller. At the same time, the controller outputs control signals to the flue gas induced draft fan, the return feeding unit, the primary blower, the fuel system, and the slag discharging unit.

2. The control method of the differential pressure of the solid heat carrier furnace bed according to claim 1, characterized in that: The hot flue gas generated after combustion brings the solid heat carrier of the solid heat carrier furnace into the cyclone separator. The high-temperature flue gas enters the flue gas system through the flue gas induced draft fan. The separated solid heat carrier enters the pyrolysis unit. At the same time, the waste feeding unit sends waste into the pyrolysis unit. After pyrolysis, the solid heat carrier is mixed with the pyrolysis residues and enters the return feeding unit, and is then conveyed into the solid heat carrier furnace again through the return feeding unit. The combustible substances in the pyrolysis residues will burn in the solid heat carrier furnace, and the incombustible substances remain on the bed.

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