An internal pressure regulation system and method for a biomass gasifier

Abstract

The present invention discloses an internal pressure regulation system for a biomass gasifier, which relates to the technical field of biomass gasifiers. It includes a biomass feeding device and a gasifier. The gasifier is provided with a biomass feeding port. The biomass feeding device includes a silo, a primary feeding screw, a feeding pipe, a rotary air lock, and a secondary feeding screw. The primary feeding screw is connected to the silo and the feeding pipe, and the secondary feeding screw is connected to the feeding pipe and the biomass feeding port. The rotary air lock is installed on the feeding pipe. A feeding rate adjustment mechanism is correspondingly arranged for the primary feeding screw, and a blowing / induced draft adjustment mechanism is correspondingly arranged for the gasifier. The gasifier is correspondingly provided with an infrared temperature measurement module and a control module. The infrared temperature measurement module is provided with a temperature limit value and a heating time limit value. The control module is connected to the feeding rate adjustment mechanism and the blowing / induced draft adjustment mechanism for control, and monitors the change of the internal pressure by monitoring the change of the temperature of the gasifier, and then regulates the pressure and the feeding amount.

Description

Technical Field

[0001] The present invention relates to the technical field of biomass gasifiers, and more specifically, it relates to an internal pressure regulation system for a biomass gasifier. Background Art

[0002] Biomass gasification refers to the process of feeding biomass raw materials (such as firewood, sawdust, wheat straw, rice straw, etc.) into a gasifier after being pressed into shape or simply crushed and processed, and performing gasification cracking under oxygen-deficient conditions to obtain combustible gas. The principle of biomass gasification is that under certain thermodynamic conditions, with the help of a gasification medium (such as air, oxygen, or steam), biomass undergoes pyrolysis, oxidation, reduction, and reforming reactions. The tar produced during pyrolysis is further thermally cracked or catalytically cracked into small-molecule hydrocarbons, obtaining a combustible gas rich in CO, H2, and CH4, etc.

[0003] For a continuously produced biomass gasifier, the stability of its feeding process is crucial, and even related to the safety of the operation of the gasification system. According to the different pressures at the biomass feeding port, gasifiers can be divided into positive-pressure type and negative-pressure type. In a negative-pressure biomass gasifier, the biomass material is "sucked" into the gasifier. Relatively speaking, the feeding process is more stable. However, in actual use, due to reasons such as fluctuations in the furnace pressure and a sudden increase in pressure caused by coking in the fluidized bed in the furnace, the feeding port may be under positive pressure at a certain moment, that is, the combustible gas in the furnace rushes back to the silo through the feeding port. At this time, even if the relevant blower plays a certain role in blocking the backflow of high-temperature gas, if no timely measures are taken, it will cause coking and blockage at the feeding port at least, and in severe cases, it will cause the silo to catch fire or even lead to major safety accidents. Therefore, it is a difficult problem that must be solved during the biomass gasification process.

[0004] Currently, the methods for solving this problem in industry mainly include: 1) installing a differential pressure sensor in the gasifier to monitor the pressure change in the furnace; 2) installing a cooling water jacket outside the biomass feeding port. However, in the actual operation of the gasifier, it is found that both of these solutions have some problems: First, whether it is a differential pressure sensor for monitoring the pressure change in the fluidized bed or a pressure sensor for monitoring the pressure change in the pipeline, in addition to having a certain detection delay problem, in a fluidized bed type gasifier, after being used for a period of time, the sensors are prone to blockage, which in turn affects the judgment of pressure changes. Second, the cooling water jacket outside the biomass feeding port can only extend the time when coking occurs at the biomass feeding port, but cannot prevent the occurrence of coking and cannot fundamentally solve this problem. Therefore, there is room for improvement. Summary of the Invention

[0005] Aiming at the deficiencies existing in the prior art, the object of the present invention is to propose an internal pressure regulation system for a biomass gasifier, which discovers the internal pressure change of the gasifier by monitoring the change of the gasifier temperature, and then regulates the pressure and the feeding amount. The specific scheme is as follows:

[0006] An internal pressure regulation system for a biomass gasifier includes a biomass feeding device and a gasifier. The gasifier is provided with a biomass feeding port. The biomass feeding device includes a silo, a primary feeding screw, a feeding pipe, a rotary air lock, and a secondary feeding screw. The feeding end and the discharging end of the primary feeding screw are respectively communicated with the discharging end of the silo and the feeding end of the feeding pipe. The feeding end and the discharging end of the secondary feeding screw are respectively communicated with the discharging end of the feeding pipe and the biomass feeding port. The rotary air lock is installed on the feeding pipe;

[0007] The primary feeding screw is correspondingly provided with a feeding rate regulating mechanism. The gasifier is correspondingly provided with a blowing / induced draft regulating mechanism. The gasifier is correspondingly provided with an infrared temperature measuring module and a control module. The infrared temperature measuring module is used to measure the temperature change at the biomass feeding port. The infrared temperature measuring module is provided with a temperature limit value and a heating time limit value. The control module is connected to the feeding rate regulating mechanism and the blowing / induced draft regulating mechanism for control.

[0008] Further, the temperature limit value is set to 100 °C.

[0009] Further, the heating time limit value is set to 3 s.

[0010] Further, the blowing / induced draft regulating mechanism includes a blower, an induced draft fan, a blower opening regulating member, and an induced draft fan opening regulating member.

[0011] Further, the blower opening regulating member and the induced draft fan opening regulating member are set as variable frequency motors.

[0012] Further, the feeding rate regulating mechanism is set as a variable frequency motor.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0014] (1) When the temperature measured by the infrared temperature measurement module exceeds the temperature limit within the heating-up time limit, it indicates that the outer wall temperature of the gasifier at the biomass feed inlet is abnormal, meaning that there is a positive pressure at the biomass feed inlet, and the gasification gas in the gasifier is flushing back into the silo. At the same time, the infrared temperature measurement module emits an electrical signal and feeds it back to the control module, providing a basis for the regulation of the air blower / induced draft regulating mechanism and the feeding rate regulating mechanism. Furthermore, the gasifier is induced to maintain a slightly negative pressure state inside the gasifier, and then the primary feeding screw is controlled to adjust the biomass feeding amount, realizing the stable transportation of biomass and the stable and safe operation of the gasifier. In summary, there is no need to set a differential pressure sensor inside the gasifier to avoid problems such as detection delay and blockage of the pressure sensor, nor is it necessary to install a cooling water jacket outside the biomass feed inlet to avoid the disadvantage that it can only extend the coking time of the biomass feed inlet but cannot prevent coking;

[0015] (2) By setting an air blower, an induced draft fan, etc., when the pressure inside the gasifier is abnormal, controlling the opening regulating parts of the air blower and the induced draft fan can achieve the regulation of the opening degrees of the air blower and the induced draft fan, which is convenient to operate and has stable operation. Description of the Drawings

[0016] Figure 1 It is a schematic diagram of the whole of the embodiment of the present invention.

[0017] Reference numerals: 1. Gasifier; 2. Silo; 3. Primary feeding screw; 4. Feeding pipe; 5. Air lock; 6. Secondary feeding screw; 7. Biomass feed inlet; 8. Infrared temperature measurement module. Detailed Embodiment

[0018] The present invention will be further described in detail below in conjunction with the embodiments and the drawings, but the embodiments of the present invention are not limited thereto.

[0019] As Figure 1 shown, a pressure regulation system inside a biomass gasifier includes a biomass feeding device and a gasifier 1. The gasifier 1 is provided with a biomass feed inlet 7. The biomass feeding device includes a silo 2, a primary feeding screw 3, a feeding pipe 4, an air lock 5, and a secondary feeding screw 6. The feeding end and the discharging end of the primary feeding screw 3 are respectively communicated with the discharging end of the silo 2 and the feeding end of the feeding pipe 4. The feeding end and the discharging end of the secondary feeding screw 6 are respectively communicated with the discharging end of the feeding pipe 4 and the biomass feed inlet 7. The air lock 5 is installed on the feeding pipe 4.

[0020] The primary feeding screw 3 and the secondary feeding screw 6 have the same structure, and when installed, the height of the primary feeding screw 3 is higher than the height of the secondary feeding screw 6, so that the feeding pipe 4 is vertically arranged in the height direction.

[0021] The biomass is placed in the silo 2 and fed into the blanking pipe 4 through the primary feeding screw 3. The biomass on the primary feeding screw 3 falls under the action of gravity and passes through the air-lock fan. The air-lock valve 5 rotates at a certain speed, causing the biomass material to fall into the secondary feeding screw 6. The secondary feeding screw 6 rotates at a high speed, enabling the biomass fed from the air-lock valve 5 to quickly enter the gasifier 1 through the biomass feeding port 7.

[0022] The gasifier 1 is correspondingly provided with an infrared temperature measurement module 8 and a control module. The infrared temperature measurement module 8 is used to measure the temperature change at the biomass feeding port 7. An external infrared thermometer is adopted, and its position is set at a certain distance from the biomass feeding port 7 of the gasifier 1 by the secondary feeding screw 6. This distance is determined comprehensively according to the actual position, angle, and multiple test results.

[0023] The infrared temperature measurement module 8 is provided with a temperature limit value and a heating-up time limit value. For a long time, based on the experience summary of the operation of the biomass gasifier 1, it is found that when there is a short-term positive pressure in the gasifier 1, the outer wall of the biomass feeding port 7 will quickly rise to above 100 °C within a short time (generally less than 3 s). Therefore, in this embodiment, the temperature limit value is set to 100 °C, and the heating-up time limit value is set to 3 s. When the infrared temperature measurement module 8 monitors that the outer wall temperature at the biomass feeding port 7 quickly rises to above 100 °C within 3 s, at this time, it represents that the pressure in the gasifier 1 is abnormal, meaning that there is a positive pressure at the biomass feeding port 7, and the gasified gas in the gasifier 1 is flushing back into the silo 2.

[0024] To facilitate the operator to adjust the parameters, the control module is signal-connected to the infrared temperature measurement module 8. The control module receives and processes the electrical signal sent by the infrared temperature measurement module 8. The control module can adopt a PLC controller, and the infrared temperature measurement module 8 is electrically connected to the input end of the control module. The primary feeding screw 3 is correspondingly provided with a feeding rate adjustment mechanism, and the gasifier 1 is correspondingly provided with a blast / induced draft adjustment mechanism. The control module is control-connected to the feeding rate adjustment mechanism and the blast / induced draft adjustment mechanism. When there is a positive pressure at the biomass feeding port 7, the feeding rate and the pressure in the gasifier 1 are adjusted by controlling the feeding rate adjustment mechanism and the blast / induced draft adjustment mechanism.

[0025] Specifically, the blast / induced draft adjustment mechanism includes a blower, an induced draft fan, a blower opening adjustment part, and an induced draft fan opening adjustment part. The blower opening adjustment part and the induced draft fan opening adjustment part are set as variable-frequency motors, and the feeding rate adjustment mechanism is set as a variable-frequency motor. The output end of the above control module is electrically connected to the variable-frequency motor. In fact, when there is a positive pressure in the gasifier 1, by changing the frequency of the feeding rate adjustment mechanism, the control of the biomass feeding amount can be achieved. By changing the frequencies of the blower opening adjustment part and the induced draft fan opening adjustment part, the pressure in the gasifier 1 can be balanced to maintain it in a slightly negative pressure state, ensuring that the biomass is "sucked" into the gasifier 1.

[0026] Specifically, the regulation methods of the infrared temperature measurement module 8 for the blower, induced draft fan and the first-stage feeding screw 3 of the gasifier 1 are as follows:

[0027] (1) During normal operation, the temperature displayed by the infrared temperature measurement module 8 should be slightly higher than the atmospheric temperature and lower than 60°C. When the temperature detected by the infrared temperature measurement module 8 is abnormal, that is, higher than 60°C, or even rapidly rises above 100°C within 3 seconds, the infrared temperature measurement module 8 sends electrical signals to the blower, induced draft fan and the first-stage feeding screw 3 respectively. After receiving the electrical signals, the variable-frequency motor operates, the opening degree of the blower is adjusted to 90% of the normal operation value through frequency conversion, the opening degree of the induced draft fan is adjusted to 110% of the normal operation value through frequency conversion, and the opening degree of the first-stage feeding screw 3 is adjusted to 80% of the normal operation value through frequency conversion. Continue to operate and wait for the temperature at the biomass feeding port 7 detected by the infrared temperature measurement module 8 to return to normal, until it is lower than 60°C, and after 10 minutes, the blower and the first-stage feeding screw 3 are slowly restored to the normal operation state through the variable-frequency motor, and after 10 minutes, the induced draft fan is slowly restored to the normal operation state through the variable-frequency motor.

[0028] (2) If the interval between two abnormal infrared temperature measurements is less than 24 hours, manually adjust the opening degree of the induced draft fan, and set the normal operation value of the opening degree of the induced draft fan to 105% of the initial setting.

[0029] (3) When the setting of the opening degree of the induced draft fan reaches the maximum value, and the interval between two abnormal infrared temperature measurements is still less than 24 hours, it indicates that the pipeline of the gasifier 1 is blocked, and the furnace needs to be shut down for maintenance to clean the blockage point.

[0030] The above are only the preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions falling within the idea of the present invention belong to the protection scope of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A pressure regulation system inside a biomass gasifier, comprising a biomass feeding device and a gasifier (1), wherein the gasifier (1) is provided with a biomass feeding port (7), and is characterized in that, The biomass feeding device includes a silo (2), a primary feeding screw (3), a feeding pipe (4), a rotary air lock (5), and a secondary feeding screw (6). The feeding end and the discharging end of the primary feeding screw (3) are respectively communicated with the discharging end of the silo (2) and the feeding end of the feeding pipe (4). The feeding end and the discharging end of the secondary feeding screw (6) are respectively communicated with the discharging end of the feeding pipe (4) and the biomass feeding port (7). The rotary air lock (5) is installed on the feeding pipe (4). A feeding rate adjusting mechanism is correspondingly arranged for the primary feeding screw (3). A blast / induced draft adjusting mechanism is correspondingly arranged for the gasifier (1). The gasifier (1) is correspondingly provided with an infrared temperature measuring module (8) and a control module electrically connected to the infrared temperature measuring module (8). The infrared temperature measuring module (8) is used for measuring the temperature change at the biomass feeding port (7). The infrared temperature measuring module (8) is provided with a temperature limit value and a heating time limit value. The control module is control-connected to the feeding rate adjusting mechanism and the blast / induced draft adjusting mechanism. The primary feeding screw (3) and the secondary feeding screw (6) have the same structure. When installed, the height of the primary feeding screw (3) is higher than that of the secondary feeding screw (6). Thus, the feeding pipe (4) is vertically arranged in the height direction.

2. The internal pressure regulation system of the biomass gasifier according to claim 1, characterized in that, The temperature limit value is set to 100 °C.

3. The internal pressure regulation system of the biomass gasifier according to claim 2, wherein The heating time limit value is set to 3 s.

4. The internal pressure regulation system of the biomass gasifier according to claim 1, wherein The blast / induced draft adjusting mechanism includes a blower, an induced draft fan, a blower opening adjusting member, and an induced draft fan opening adjusting member.

5. The internal pressure regulation system of the biomass gasifier according to claim 4, wherein The blower opening adjusting member and the induced draft fan opening adjusting member are set as variable frequency motors.

6. The internal pressure regulation system of the biomass gasifier according to claim 5, characterized in that, The feeding rate adjusting mechanism is set as a variable frequency motor.

7. The internal pressure regulation system of the biomass gasifier according to claim 6, characterized in that, The control methods for the blower, the induced draft fan, and the primary feeding screw (3) are as follows: During normal operation, the temperature displayed by the infrared temperature measuring module (8) is higher than the atmospheric temperature and lower than 60 °C. When the temperature detected by the infrared temperature measuring module (8) is abnormal, the infrared temperature measuring module (8) respectively sends electrical signals to the blower, the induced draft fan, and the primary feeding screw (3). After receiving the electrical signals, the variable frequency motor operates. The opening of the blower is adjusted to 90% of the normal operation value by frequency conversion. The opening of the induced draft fan is adjusted to 110% of the normal operation value by frequency conversion. The opening of the primary feeding screw (3) is adjusted to 80% of the normal operation value by frequency conversion. Continue to operate and wait for the infrared temperature measuring module (8) to detect that the temperature at the biomass feeding port (7) returns to normal, until it is lower than 60 °C and lasts for 10 min. Then, the blower and the primary feeding screw (3) are slowly restored to the normal operation state through the variable frequency motor and last for 10 min. Then, the induced draft fan is slowly restored to the normal operation state through the variable frequency motor. When the interval between two infrared temperature measurement abnormalities is less than 24 h, manually adjust the opening of the induced draft fan, and set the normal operation value of the opening of the induced draft fan to 105% of the initial setting. When the opening setting of the induced draft fan reaches the maximum value and the interval between two abnormal infrared temperature measurements is still less than 24 hours, the boiler shall be stopped for maintenance.

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