A biomass gas combustion system and control method for precisely controlling combustion

Abstract

The present invention discloses a biomass gas combustion system and control method for accurately controlling combustion. The system includes: a biomass gas burner, a biomass gas pipeline connected to the burner, a blower, an air supply pipeline connecting the blower and the burner, a tar collection device in the furnace of a biomass boiler, an oxygen sensor arranged on the boiler exhaust pipe, a controller based on a PLC system, and a blower frequency converter. A gas composition, flow, temperature, and pressure measuring device is arranged on the biomass gas pipeline, and a flow and temperature measuring device is arranged on the air supply pipeline. The controller calculates the amount of oxygen required for biomass gas combustion and the amount of oxygen provided by the blower according to the data fed back by the measuring device, and controls the blower frequency converter to adjust the air volume of the blower under the correction of the feedback data of the oxygen sensor on the boiler exhaust pipe, so as to achieve the purpose of accurately controlling combustion under partial load conditions of the boiler, improving combustion efficiency, and reducing pollutant emissions.

Description

Technical Field

[0001] The present invention relates to the technical field of biomass gas burners, and more particularly to a biomass gas combustion system and a control method for accurately controlling combustion. Background Art

[0002] Biomass gas is a combustible gas produced by high-temperature cracking of biomass raw materials (wood chips, bamboo, rice husks, fruit shells and other agricultural and forestry waste) in a biomass gasifier. Biomass gas is a low-calorific value combustible gas that needs to be mixed with air in a suitable ratio to achieve a full combustion effect. At present, the main way to utilize biomass gas is to supply biomass gas boilers with gas produced by biomass gasifiers for combustion and heating. The biomass gas boiler burner is equipped with a blower to send air into the burner to mix with the biomass gas produced by the biomass gasifier and then burn it.

[0003] In actual operation, the composition of biomass gas produced by biomass gasifier is unstable. At the same time, the heating system of biomass gasifier + biomass gas boiler is affected by the demand of the user side and operates at partial load for a long time. When the flow rate of biomass gas produced by biomass gasifier under partial load operation is reduced, the gas composition also changes compared with full load conditions. The air volume cannot be simply adjusted according to the proportion of the reduction in biomass gas flow rate. Therefore, the amount of air required for the complete combustion of biomass gas entering the biomass gas boiler burner needs to be precisely controlled to ensure the complete combustion of biomass gas. The existing burners control the air-fuel ratio by manual operation, and the blower air volume is adjusted based on the experience of the operator. It is impossible to ensure the optimal ratio of biomass gas to air in the burner, and it is impossible to effectively monitor the combustion of biomass gas. It often causes excessive oxygen, excessive nitrogen oxide emissions, or insufficient oxygen, and incomplete combustion and emission of some biomass gas. While reducing the utilization rate of biomass gas, it will also bring inconvenience to the operation and management of the system.

[0004] The biomass burner with patent number 201821890644 is equipped with carbon monoxide and oxygen concentration sensors on the tailpipe, and the combustion status of biomass gas is judged according to the sensor feedback data, and the biomass gas supply valve is controlled to adjust the ratio of biomass gas to air, so as to improve the combustion efficiency of biomass gas. However, this solution does not take into account the control lag and untimely response of the gas supply valve to adjust the biomass gas flow, and it is difficult to achieve the purpose of accurately controlling the complete combustion of biomass gas. Summary of the invention

[0005] In view of this, the present invention provides a biomass gas combustion system and control method for accurately controlling combustion. The system can effectively solve the problem that the existing biomass gas burner cannot accurately control combustion under partial load conditions, improve the efficiency of the burner, and collect unburned tar to return to the gasifier, further improving the efficiency of the entire gasification heating system.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] A biomass gas combustion system for precisely controlling combustion, comprising: a biomass gas burner on a biomass gas boiler body, a biomass gas pipeline connected to the biomass gas burner, a blower, an air supply pipeline connecting the blower and the biomass gas burner, a tar collection device at the bottom of the biomass gas boiler furnace, an oxygen sensor arranged on a boiler exhaust pipe, a controller based on a PLC system, and a blower frequency converter;

[0008] The controller is electrically connected to the blower inverter and the oxygen sensor respectively;

[0009] The blower inverter is electrically connected to the blower.

[0010] Preferably, the biomass gas pipeline is provided with a dust and descorch filter, a gas composition measuring device, a flow measuring device A, a pressure measuring device, and a temperature measuring device A in sequence from the inlet end to the outlet end;

[0011] The gas composition measuring device, flow measuring device A, pressure measuring device, and temperature measuring device A are electrically connected to the controller respectively.

[0012] Preferably, the pressure measuring device is an absolute pressure measuring device.

[0013] Preferably, the air intake duct is provided with a temperature measuring device B and a flow measuring device B;

[0014] The temperature measuring device B and the flow measuring device B are electrically connected to the controller respectively.

[0015] Preferably, the above system further comprises: a tar level measuring device, a tar pump, and a tar pipeline connecting the tar pump and the tar collecting device, which are arranged on the tar collecting device;

[0016] The tar level measuring device and the tar pump are electrically connected to the controller respectively.

[0017] Preferably, the tar pump is connected to an external biomass gasifier.

[0018] Another object of the present invention is to provide a control method for a biomass gas combustion system for accurately controlling combustion, comprising the following steps:

[0019] Step (1): The controller analyzes and calculates the feedback data from the gas composition measuring device, flow measuring device A, pressure measuring device and temperature measuring device A on the biomass gas pipeline to obtain the mass flow rate of oxygen required for combustion;

[0020] Step (2): the controller obtains the real-time oxygen mass flow rate provided by the blower according to the feedback data of the temperature measuring device B and the flow measuring device B on the air intake duct;

[0021] Step (3): the controller adjusts the blower to increase or decrease the blowing volume through the blower inverter according to the difference in the mass flow rate of oxygen obtained in step (1) and step (2);

[0022] Step (4): The controller corrects the blower air volume in real time through feedback data from an oxygen sensor installed on the boiler flue gas duct to ensure accurate control of complete combustion of the biomass gas;

[0023] Step (5): When the tar level sensor on the tar collection device in the furnace reaches the set value, the tar level signal is fed back to the controller, and the controller starts the tar pump to return the collected tar in the furnace to the gasifier for pyrolysis and combustion, further improving the efficiency of the entire system.

[0024] Preferably, in the controller analysis and calculation process in step (1), the excess air coefficient is used as a correction to obtain the mass flow rate of oxygen required for combustion, wherein the excess air coefficient is a constant related to the boiler equipment.

[0025] It can be seen from the above technical solution that compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. The present invention adopts a gas composition measuring device and a flow measuring device A on the biomass gas pipeline, a temperature measuring device B and a flow measuring device B on the air intake pipeline, and feeds back signals to the controller, which adjusts the blower inverter to control the blower volume of the burner, thereby achieving the purpose of automatic and precise adjustment, ensuring the combustion efficiency of the burner, and reducing the emission of nitrogen oxides in the boiler flue gas;

[0027] 2. The feedback data of the oxygen sensor on the boiler flue gas duct of the present invention eliminates the influence of the change of the excess air coefficient under partial load conditions, and corrects the blower air volume through the oxygen sensor signal, thereby achieving the purpose of accurately controlling the air-fuel ratio.

[0028] 3. The present invention also achieves the purpose of collecting the incompletely burned tar in the biomass gas and automatically returning it to the gasifier for continued use through the tar collection device in the furnace, thereby further improving the efficiency of the entire system. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0030] Figure 1 A composition diagram of a biomass gas combustion system for precisely controlling combustion according to the present invention;

[0031] Figure 2 A schematic diagram of a biomass gas combustion system control method for accurately controlling combustion according to the present invention;

[0032] Among them, in the figure:

[0033] 1-biomass gas burner; 2-flow measuring device A; 3-gas composition measuring device; 4-decoking and dust removal filter; 5-biomass gas pipeline; -6-blower inverter; 7-blower; 8-temperature measuring device B; 9-flow measuring device B; 10-air supply pipeline; 11-tar pump; 12-tar pipeline; 13-tar collecting device; 14-tar liquid level measuring device; 15-oxygen sensor; 16-boiler flue gas pipeline; 17-biomass gas boiler; 18-controller; 19-pressure measuring device; 20-temperature measuring device A. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] Example 1

[0036] This embodiment provides a biomass gas combustion system for precisely controlling combustion:

[0037] according to Figure 1 As shown, it includes a biomass gas burner (1) arranged on a biomass gas boiler (17) body, a biomass gas pipeline (5) connected to the burner, a blower (7), an air intake pipeline (10) connecting the blower (7) and the burner (1), a tar collection device (13) in the furnace of the biomass boiler, an oxygen sensor (15) arranged on the boiler exhaust pipeline (16), a controller (18) based on a PLC system, and a blower frequency converter (6);

[0038] The biomass gas pipeline (5) is provided with a dust and descorch filter (4), a gas composition measuring device (3), a flow measuring device A (2), a pressure measuring device (19), and a temperature measuring device A (20) in sequence.

[0039] The de-coking and dust removal filter (4) is used to filter tar and solid particles in the biomass gas entering the burner (1) to ensure gas cleanliness; the gas composition measuring device (3) is used to measure the volume fraction of the main combustible gases CO, H2, and CH4 in the biomass gas; the flow measuring device A (2) is used to measure the volume flow of the biomass gas entering the burner (1); the pressure measuring device (19) is an absolute pressure measuring device used to measure the gas pressure of the biomass gas; and the temperature measuring device A (20) is used to measure the temperature of the main combustible gases CO, H2, and CH4 in the biomass gas.

[0040] The air supply pipeline (10) is provided with a temperature measuring device B (8) and a flow measuring device B (9).

[0041] The temperature measuring device B (8) is used to measure the temperature of the air entering the burner (1), and the flow measuring device B (9) is used to measure the volume flow of the air entering the burner (1).

[0042] The tar collecting device (13) comprises a tar level measuring device (14) arranged on the tar collecting device, a tar pump (11), and a tar pipeline (12) connecting the tar pump and the tar collecting device.

[0043] The gas composition measuring device (3), flow measuring device A (2), pressure measuring device (19), and temperature measuring device A (20) on the biomass gas pipeline (5) are electrically connected to a controller (18) based on a PLC system, and are used to feed back the volume fractions of the main combustible gases CO, H2, and CH4 in the biomass gas, the volume flow rate of the biomass gas, and the temperature and pressure signals of the biomass gas measured by the above sensors to the controller (18). The controller (18) analyzes the above data, and the partial pressure and temperature of the main combustible gases CO, H2, and CH4 can be obtained from the temperature, pressure and volume fraction of the main combustible gases CO, H2, and CH4 of the biomass gas; the mass flow rate of each main combustible gas CO, H2, and CH4 can be obtained from the partial pressure, temperature and volume flow rate of the main combustible gases CO, H2, and CH4 of the biomass gas; the mass flow rate of oxygen required to ensure the complete combustion of the main combustible gases CO, H2, and CH4 in the biomass gas can be obtained from the chemical reaction formula; after correction of the excess air coefficient, the controller can obtain the actual mass flow rate of oxygen required to ensure the complete combustion of the main combustible gases CO, H2, and CH4 in the biomass gas.

[0044] The temperature measuring device B (8) and the flow measuring device B (9) on the air supply pipeline are electrically connected to the controller (18) based on the PLC system, and the temperature and volume flow of the air entering the burner (1) measured by the above sensors are fed back to the controller (18). The controller can obtain the mass flow of oxygen provided by the blower (7) in real time based on the above data.

[0045] The tar level measuring device (14) on the tar collecting device (13) and the tar pump (11) are electrically connected to a controller (18) based on a PLC system, and are used to feed back a level signal of unburned tar in the furnace collected by the tar collecting device (13) to the controller (18).

[0046] The oxygen sensor (15) on the boiler flue gas pipeline (16) is electrically connected to a controller (18) based on a PLC system, and is used to feed back the oxygen concentration signal in the exhaust gas after combustion to the controller (18).

[0047] The blower inverter (6) is electrically connected to a controller (18) based on a PLC system, and the blower inverter (6) is electrically connected to the blower (7). The controller (18) can control the amount of air that the blower (7) enters into the burner (1) through the blower inverter (6).

[0048] Example 2

[0049] This embodiment provides a control method for a biomass gas combustion system for accurately controlling combustion, including:

[0050] Step (1): The controller obtains the theoretical oxygen mass flow rate required for complete combustion of the biomass gas based on the feedback data from the gas composition measuring device (3), the flow measuring device A (2), the pressure measuring device (19) and the temperature measuring device A (20) on the biomass gas pipeline (5), and uses the preset excess air coefficient as a correction to obtain the oxygen mass flow rate required for combustion.

[0051] Step (2): The controller (8) obtains the real-time oxygen mass flow rate provided by the blower (7) based on the feedback data from the temperature measuring device B (8) and the flow measuring device B (9) on the air supply pipeline (10).

[0052] Step (3): the controller (18) adjusts the blower (7) to increase or decrease the blowing volume through the blower frequency converter (6) according to the difference in the oxygen mass flow rate obtained in step (1) and step (2).

[0053] Step (4): The controller (18) corrects the air volume of the blower (7) in real time based on the feedback data of the oxygen sensor (15) arranged on the boiler flue gas duct (16), so as to ensure accurate control of the complete combustion of the biomass gas.

[0054] Step (5): When the tar level sensor (14) on the tar collecting device (13) in the furnace detects that the level reaches the set value, the tar level signal is fed back to the controller (18), and the controller (18) starts the tar pump (11) to return the collected tar in the furnace to the gasifier for pyrolysis and combustion, thereby further improving the efficiency of the entire system.

[0055] The process of calculating and analyzing the feedback signals of the gas composition measuring device (3), the flow measuring device A (2), the pressure measuring device (19), and the temperature measuring device A (20) on the biomass gas pipeline (5) in step (1) in the controller (18) to obtain the oxygen mass flow required for biomass gas combustion is as follows:

[0056] The oxygen mass flow rate required for the complete combustion of the main combustible gases CO, H2, and CH4 in biomass gas:

[0057] Q O1 =λ×∑(VOL i ×P×M i ) / (R×(T a +273.15)×1000)×Q1×θ i

[0058] In the formula:

[0059] Q O1 The mass flow rate of oxygen required for complete combustion of combustible gas in biomass gas (kg / h);

[0060] VOL i The volume fraction (%) of the corresponding combustible gas measured by the gas composition measuring device;

[0061] P is the absolute pressure of biomass gas measured by the pressure measuring device on the biomass gas pipeline (Pa);

[0062] M i is the corresponding molar mass of the combustible gas (28 g / mol for CO, 2 g / mol for H2, and 16 g / mol for CH4);

[0063] R is the gas constant 8.314;

[0064] T a is the biomass gas temperature measured by the temperature measuring device A on the biomass gas pipeline (℃);

[0065] Q1 is the volume flow rate of biomass gas measured by flow measurement device A (m 3 / h);

[0066] θ iThe oxygen consumption coefficient corresponding to the combustion of combustible gas (CO is 0.57, H2 is 8, CH4 is 4);

[0067] λ is the excess air coefficient;

[0068] i is the combustible gases CO, H2, and CH4 in biomass gas;

[0069] In step (2), the feedback signals of the flow measurement device B (9) and the temperature measurement device B (8) on the air supply pipeline (10) are calculated and analyzed in the controller (18) to obtain the oxygen mass flow rate provided by the blower (7) in real time as follows:

[0070] Q O2 =(6.72×P a ) / (R×(T b +273.15)×1000)×Q2

[0071] In the formula:

[0072] Q O2 The oxygen mass flow rate (kg / h) provided in real time to the blower (7);

[0073] P a is atmospheric pressure (Pa);

[0074] R is the gas constant 8.314;

[0075] T b The air temperature (°C) measured by the temperature measuring device B (8) on the air supply pipe (10);

[0076] Q2 is the volume flow rate (m2) of air provided by the blower (7) measured by the flow measurement device B (9). 3 / h);

[0077] The control principle of the controller (8) in step (3) adjusting the blower (7) is as follows:

[0078] When Q O1 >Q O2 When Q O1 <Q O2 When Q O1 =Q O2 , the controller (18) does not operate.

[0079] In step (4), the oxygen sensor (15) on the boiler exhaust pipe (16) feeds back the oxygen concentration signal in the exhaust gas after combustion to the controller (18). The controller (18) compares the oxygen concentration in the boiler exhaust with the set oxygen concentration to determine whether the mixing ratio of biomass gas and air meets the requirements for complete combustion, and corrects the air volume of the blower (7) according to the comparison deviation, thereby ultimately achieving the purpose of accurately controlling combustion.

[0080] In step (5), the tar level measuring device (14) on the tar collecting device (13) feeds back the level signal of the unburned tar in the furnace collected by the tar collecting device to the controller (18); when the set upper limit of the tar level is reached, the tar pump (11) is started to return the collected tar in the furnace to the gasifier for pyrolysis and combustion; when the set lower limit of the tar level is reached, the tar pump (11) is stopped, and the tar collecting device (13) continues to collect the unburned tar in the furnace.

[0081] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0082] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A biomass gas combustion system with precise combustion control, characterized in that: include: A biomass gas burner on the biomass gas boiler body, a biomass gas pipeline connected to the biomass gas burner, a blower, an air supply pipeline connecting the blower and the biomass gas burner, a tar collection device at the bottom of the biomass gas boiler furnace, an oxygen sensor arranged on the boiler exhaust pipe, a controller based on a PLC system, and a blower frequency converter; The controller is electrically connected to the blower inverter and the oxygen sensor respectively; The blower inverter is electrically connected to the blower.

2. A biomass gas combustion system for precisely controlling combustion according to claim 1, characterized in that: The biomass gas pipeline is provided with a dust and descorch filter, a gas composition measuring device, a flow measuring device A, a pressure measuring device, and a temperature measuring device A in sequence from the inlet end to the outlet end; The gas composition measuring device, flow measuring device A, pressure measuring device, and temperature measuring device A are electrically connected to the controller respectively.

3. A biomass gas combustion system for precisely controlling combustion according to claim 2, characterized in that: The pressure measuring device is an absolute pressure measuring device.

4. A biomass gas combustion system for precisely controlling combustion according to claim 3, characterized in that: The air intake duct is provided with a temperature measuring device B and a flow measuring device B; The temperature measuring device B and the flow measuring device B are electrically connected to the controller respectively.

5. A biomass gas combustion system for precisely controlling combustion according to claim 4, characterized in that: Also includes: A tar level measuring device, a tar pump, and a tar pipeline connecting the tar pump and the tar collecting device are arranged on the tar collecting device; The tar level measuring device and the tar pump are electrically connected to the controller respectively.

6. The biomass gas combustion system for precisely controlling combustion according to claim 5, characterized in that: The tar pump is connected to an external biomass gasifier.

7. A control method for a biomass gas combustion system for precise combustion control as claimed in claim 6, characterized in that: The following steps are involved: Step (1): The controller analyzes and calculates the feedback data from the gas composition measuring device, flow measuring device A, pressure measuring device and temperature measuring device A on the biomass gas pipeline to obtain the mass flow rate of oxygen required for combustion; Step (2): the controller obtains the real-time oxygen mass flow rate provided by the blower according to the feedback data of the temperature measuring device B and the flow measuring device B on the air intake duct; Step (3): the controller adjusts the blower to increase or decrease the blowing volume through the blower inverter according to the difference in the mass flow rate of oxygen obtained in step (1) and step (2); Step (4): The controller corrects the blower air volume in real time through feedback data from an oxygen sensor installed on the boiler flue gas duct to ensure accurate control of complete combustion of the biomass gas; Step (5): When the tar level sensor on the tar collection device in the furnace reaches the set value, the tar level signal is fed back to the controller, and the controller starts the tar pump to return the collected tar in the furnace to the gasifier for pyrolysis and combustion, further improving the efficiency of the entire system.

8. The control method of a biomass gas combustion system for accurately controlling combustion according to claim 7, characterized in that: In the controller analysis and calculation process in step (1), the excess air coefficient is used as a correction to obtain the mass flow rate of oxygen required for combustion, wherein the excess air coefficient is a constant related to the boiler equipment.

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