Biomass and coal-fired boiler coupling power generation system and its power generation capacity calculation method

Abstract

This invention relates to a biomass-coal-fired boiler coupled power generation system and a method for calculating its power generation. The system includes a biomass furnace, a cyclone dust collector, a high-temperature flue gas measuring device, a pulverized coal furnace, and an air preheater, connected in sequence. The pulverized coal furnace includes a main burner, a high-temperature flue gas burner, and a separate burnout air burner. The high-temperature flue gas burner is arranged between the main burner and the separate burnout air burner; or the high-temperature flue gas burner is arranged in the main burner area. The biomass power generation of the coupled power generation system is P, representing the heat generated by biomass combustion. b =Q / Q b *P e ;P e Q represents the total power generation of the biomass-coal-fired boiler coupled power generation system; Q is the heat absorbed by the high-temperature flue gas after biomass combustion in the pulverized coal furnace; Q b This invention relates to a simple thermal system where biomass combustion and coal combustion occur in two separate furnaces, reducing the coupling between the two combustion processes and improving the overall system's operational flexibility.

Description

Technical Field

[0001] This invention belongs to the field of biomass coupled with coal-fired power generation, and specifically relates to a biomass coupled with a coal-fired boiler power generation system and a method for calculating its power generation. Background Technology

[0002] With increasing global focus on greenhouse gas emission control, coal-fired power plants, as the main source of CO2 emissions, need to reduce fossil fuel consumption to meet future carbon peaking and carbon neutrality goals. In the future, coal-fired power plants will face the dual pressures of carbon emission reduction and high power generation costs. Fuel substitution for coal-fired power plants will become one of the technological directions for the future transformation and development of thermal power.

[0003] Biomass, as a naturally occurring energy source that uses CO2 as a carrier and is renewable, can replace some fossil fuels. Biomass exists in three main forms of utilization: gaseous fuel, liquid fuel, and solid fuel, and has been widely used. Vigorously developing and utilizing biomass can reduce the consumption of fossil fuels and lower CO2 emissions caused by the combustion of fossil fuels.

[0004] For coal-fired power units, to reduce CO2 emissions, under the premise of the same power generation, CO2 emissions in boiler flue gas can be reduced by burning low-carbon or zero-carbon fuels. Another method is to add carbon capture devices, such as CCS / CCUS devices, at the boiler tail end to absorb all or part of the CO2 in the flue gas, and then store or utilize the captured CO2, thereby reducing the CO2 emissions from the boiler flue gas. Currently, using biomass fuel to reduce coal consumption is a technically feasible and economically reasonable solution, and various technical routes have been tested and demonstrated in the industry, achieving the expected technical results.

[0005] There are three main types of biomass-co-fired power generation technologies: The first is steam-side coupling, which couples the steam generated by the biomass boiler with the steam from the coal-fired unit. Depending on the steam parameters, the steam from the biomass boiler is mixed and connected to the corresponding steam parameter location in the coal-fired generator unit, and then generated electricity through a conventional coal-fired generator unit and thermal system. The second is flue gas-side coupling, which first gasifies the biomass fuel in a gasifier, converting it into high-temperature gas. After dust removal and cooling, the gas is then sent into the coal-fired furnace by an induced draft fan, where it is coupled with pulverized coal and burned together in the furnace. The third is fuel-side coupling, which grinds the biomass fuel into biomass powder through a pulverizing system, then sends it to a special burner and injects it into the furnace to be coupled with pulverized coal and burned together in the furnace.

[0006] Existing technologies have the following drawbacks: For the first technology, biomass boilers are limited by fuel collection capacity, generally have small capacities, and produce low-parameter steam. This means they can only couple with correspondingly low-parameter steam from the turbine side, resulting in low power generation efficiency. Furthermore, with load changes, mismatches can easily occur between the biomass boiler parameters and the corresponding steam parameters at the turbine coupling point, leading to energy loss or inoperability. Synchronizing the steam parameters of the biomass boiler with those of the coal-fired power generation unit is challenging. For the second technology, which involves pre-gasifying biomass, there are technical difficulties such as gasification heat loss, difficulty in controlling the gasification process, and poor fuel adaptability. The syngas produced after biomass gasification mainly consists of H2 and CO, posing an explosion hazard. The tar produced during gasification is difficult to handle and negatively impacts subsequent metering devices and pipeline operation, requiring special consideration and solutions. The third technology involves feeding biomass fuel into a specialized grinding system for grinding. However, due to the toughness of components such as cellulose and hemicellulose in biomass fuel, it is not easy to grind. Furthermore, biomass fuel is prone to releasing volatiles during the grinding process, which can easily lead to fires or explosions. Additionally, it can cause accumulation and heat in the silos and other parts attached to the biomass grinding system, resulting in accidents. Another challenge with this third technology is the difficulty in metering. It is impossible to measure the calorific value of the biomass fuel fed into the pulverized coal furnace during the coupling process in real time, making it impossible to accurately apply additional subsidies to the electricity generated by biomass power generation. Summary of the Invention

[0007] To address the aforementioned problems, this invention provides a biomass-coal-fired boiler coupled power generation system and its power generation calculation method. The main objective is to feed biomass fuel into an insulated biomass furnace for combustion, and then feed the resulting high-temperature flue gas into the coal-fired boiler furnace. By measuring the flue gas flow rate, temperature, and composition, the calorific value of the biomass fed into the coal-fired furnace can be calculated in real time, thereby obtaining the share of electricity generated by biomass-coupled power generation and the total power output. By feeding biomass fuel (in bulk or pellet form) into the insulated biomass furnace, high-temperature flue gas is generated after combustion. By controlling the oxygen content of the high-temperature flue gas and the combustion temperature within the furnace, the generated high-temperature flue gas is fed into the coal-fired boiler furnace for staged combustion with pulverized coal, achieving NOx reduction within the pulverized coal furnace, thereby reducing fuel consumption and NOx concentration in the pulverized coal boiler. By utilizing the composition and temperature of the high-temperature flue gas generated in the biomass insulated furnace, the enthalpy value corresponding to the high-temperature flue gas can be calculated. Using the exhaust gas temperature of the pulverized coal boiler as a calculation benchmark, the heat of biomass combustion fed into the pulverized coal furnace can be calculated in real time.

[0008] The technical solution adopted in this invention is as follows: a biomass and coal-fired boiler coupled power generation system, the system comprising a biomass furnace, a cyclone dust collector, a high-temperature flue gas measuring device, a pulverized coal furnace and an air preheater connected in sequence, the pulverized coal furnace comprising a main burner, a high-temperature flue gas burner and a separate burnout air burner; the high-temperature flue gas burner is arranged between the main burner and the separate burnout air burner; or the high-temperature flue gas burner is arranged in the area of ​​the main burner.

[0009] Furthermore, the high-temperature flue gas measuring device includes a flue gas sampling device, a flue gas pretreatment device, and a flue gas flow rate, temperature, and composition measuring device connected in sequence; the flue gas sampling device is arranged in the channel of the high-temperature flue gas outlet of the biomass boiler.

[0010] Furthermore, the cyclone dust collector is equipped with a biomass boiler fly ash outlet, a biomass boiler circulating ash outlet, a biomass boiler high-temperature dust-laden flue gas inlet, and a biomass boiler high-temperature flue gas outlet; wherein, the biomass boiler fly ash outlet and the biomass boiler circulating ash outlet are both connected to the bottom of the cyclone dust collector; the biomass boiler high-temperature dust-laden flue gas inlet is connected to the inlet of the cyclone dust collector; and the biomass boiler high-temperature flue gas outlet is connected to a high-temperature flue gas measuring device.

[0011] Furthermore, the biomass furnace is connected to the biomass silo and the air supply device, and the biomass furnace is equipped with a high-temperature dusty flue gas outlet and a biomass boiler bottom ash outlet.

[0012] Furthermore, the air supply device includes a blower, a shut-off baffle, and an adjusting baffle connected in sequence, and the air supply device is connected to the bottom of the biomass furnace.

[0013] Furthermore, the air supply device includes a hot primary air temperature measuring device, a hot primary air flow measuring device, a shut-off baffle, and an adjusting baffle connected in sequence. The outlet of the air supply device is connected to the bottom of the biomass furnace, and the inlet of the air supply device is connected to the hot primary air outlet of the coal-fired boiler. The hot primary air outlet of the coal-fired boiler is connected to the air preheater.

[0014] Furthermore, the low-temperature flue gas measuring device at the boiler outlet is arranged on the flue at the air preheater outlet.

[0015] This invention also provides a method for calculating the power generation of the above-mentioned biomass-coal-fired boiler coupled power generation system, wherein the biomass power generation of the coupled power generation system is... Where W1 represents the biomass power generation of the coupled power generation system within the time interval [t1, t2]; and P represents the power generation from the heat generated by biomass combustion. b =Q / Q b *P e ;P eQ represents the total power generation of the biomass-coal-fired boiler coupled power generation system; Q is the heat absorbed by the high-temperature flue gas after biomass combustion in the pulverized coal furnace; Q b It absorbs heat for the entire coal-fired furnace.

[0016] Furthermore, the formula for calculating the heat Q absorbed by the high-temperature flue gas after biomass combustion in the pulverized coal furnace is as follows:

[0017] Q=V*[(h(T1, N2)-h(T2, N2))*γ N2 +(h(T1, O2)-h(T2, O2))*γ O2 +(h(T1,CO2)-h(T2,CO2))*γ CO2 +(h(T1,H2O)-h(T2,H2O))*γ H2O ],

[0018] Where h(T1, N2), h(T1, O2), h(T1, CO2), and h(T1, H2O) are the enthalpy per unit volume of N2, O2, CO2, and H2O at temperature T1, respectively; h(T2, N2), h(T2, O2), h(T2, CO2), and h(T2, H2O) are the enthalpy per unit volume of N2, O2, CO2, and H2O at temperature T2, respectively; γ N2 γ O2 γ CO2 γ H2O These represent the volume percentages of N2, O2, CO2, and H2O in the high-temperature flue gas, respectively.

[0019] T1 is the temperature of the high-temperature flue gas entering the pulverized coal furnace, T2 is the temperature of the flue gas at the outlet of the air preheater, and V is the volumetric flow rate of the high-temperature flue gas.

[0020] Furthermore, the overall heat absorption Q of the coal-fired furnace b The calculation formula is:

[0021] Q b =m FW *(h ST -h FW )+m RH *(h RHO -h RHI )+m GJ *(h ST -h GJ )+m RJ *(h RHO -h RJ ),

[0022] Where, m FW h is the water flow rate. ST h is the enthalpy per unit mass of the superheated steam outlet.FW Enthalpy per unit mass of water; m RH h is the inlet flow rate of reheat steam. RHO h is the enthalpy per unit mass of the reheat steam outlet. RHI m is the enthalpy per unit mass of the reheat steam inlet. GJ The flow rate of desuperheating water for the superheater; h GJ Enthalpy per unit mass of the superheater desuperheating water; m RJ The flow rate of desuperheating water for the reheater; h RJ The enthalpy per unit mass of the desuperheating water for the reheater.

[0023] Furthermore, the coal-fired power generation capacity of the coupled power generation system is Where W2 represents the coal-fired power generation of the coupled power generation system within the time interval [t1, t2]; P c P is the power generation capacity of electricity generated by the heat produced by the combustion of pulverized coal in a coal-fired furnace. c =(1-Q / Q) b )*P e .

[0024] This invention also provides another method for calculating the power generation of the above-mentioned biomass-coal-fired boiler coupled power generation system, wherein the biomass power generation of the coupled power generation system is... P b ' represents the power generation capacity of electricity generated by the heat from biomass combustion, P b ' = Q' / Q b *P e Among them, P e Q' represents the total power generation of the biomass-coal-fired boiler coupled power generation system; Q' represents the heat absorbed by the high-temperature flue gas after biomass combustion in the pulverized coal furnace; Q b It absorbs heat for the entire coal-fired furnace.

[0025] Furthermore, the formula for calculating the heat Q' absorbed by the high-temperature flue gas after biomass combustion in the pulverized coal furnace is as follows:

[0026] Q'=V*[(h(T1, N2)-h(T2, N2))*γ N2 +(h(T1, O2)-h(T2, O2))*γ O2 +(h(T1,CO2)-h(T2,CO2))*γ CO2 +(h(T1,H2O)-h(T2,H2O))*γ H2O ]-V0*(h(T3, N2)*0.79+h(T3, O2)*0.21);

[0027] Where h(T1, N2), h(T1, O2), h(T1, CO2), and h(T1, H2O) are the enthalpy per unit volume of N2, O2, CO2, and H2O at temperature T1, respectively; h(T2, N2), h(T2, O2), h(T2, CO2), and h(T2, H2O) are the enthalpy per unit volume of N2, O2, CO2, and H2O at temperature T2, respectively; h(T3, N2) and h(T3, O2) are the enthalpy per unit volume of N2 and O2 at temperature T3, respectively; γ N2 γ O2 γ CO2 γ H2O These represent the volume percentages of N2, O2, CO2, and H2O in the high-temperature flue gas, respectively.

[0028] T1 is the temperature of the high-temperature flue gas entering the pulverized coal furnace; T2 is the flue gas temperature at the air preheater outlet; T3 is the temperature of the hot primary air; V is the volumetric flow rate of the high-temperature flue gas; V0 is the volumetric flow rate of the hot primary air diverted from the air preheater outlet to the biomass furnace.

[0029] Furthermore, the overall heat absorption Q of the coal-fired furnace b The formula for calculating Q is: b =m FW *(h ST -h FW )+m RH *(h RHO -h RHI )+m GJ *(h ST -h GJ )+m RJ *(h RHO -h RJ )

[0030] Where, m FW h is the water flow rate. ST h is the enthalpy per unit mass of the superheated steam outlet. FW Enthalpy per unit mass of water; m RH h is the inlet flow rate of reheat steam. RHO h is the enthalpy per unit mass of the reheat steam outlet. RHI m is the enthalpy per unit mass of the reheat steam inlet. GJ The flow rate of desuperheating water for the superheater; h GJ Enthalpy per unit mass of the superheater desuperheating water; m RJ The flow rate of desuperheating water for the reheater; h RJ The enthalpy per unit mass of the desuperheating water for the reheater.

[0031] Furthermore, the coal-fired power generation capacity of the coupled power generation system is Where W4 represents the coal-fired power generation of the coupled power generation system within the time interval [t1, t2]; P c ' represents the power generation capacity of electricity generated by the combustion of pulverized coal in a coal-fired furnace, P. c ' = (1 - Q' / Q) b )*P e .

[0032] Compared with existing technologies, this invention overcomes the technical difficulties of the three existing solutions, and has wider adaptability to biomass fuels. It features a simple thermal system, easy operation and control, intuitive metering, and accurate acquisition of the subsidized electricity price for coupled power generation. The biomass-coal boiler coupled power generation system and its power generation calculation method designed in this invention have the following beneficial effects:

[0033] 1) The thermal system is simple and easy to implement. It is feasible to couple it with existing coal-fired boilers for power generation. Biomass combustion and coal combustion take place in two independent furnaces, which reduces the coupling between the two combustion processes and improves the overall system operation flexibility.

[0034] 2) By detecting the flow rate, temperature and composition of the high-temperature flue gas after biomass fuel combustion, the heat sent to the pulverized coal boiler can be calculated using thermodynamic principles. The measurement is simple and accurate, and the energy input of biomass in the coupled power generation system and the corresponding power generation can be detected in real time to obtain power generation subsidies.

[0035] 3) Biomass insulated furnaces improve the adaptability of biomass fuels, enabling them to burn low-quality biomass fuels with high moisture and ash content, and are not sensitive to the low calorific value of the fuel.

[0036] 4) By using measures such as cyclone dust removal, fly ash after biomass combustion is separated, reducing the fly ash content fed into the pulverized coal furnace and mitigating the impact of alkali metals in biomass fuel on high-temperature heating surfaces.

[0037] 5) The biomass energy utilization efficiency of the coupled system is high. The medium- and high-temperature insulated furnace improves the combustion efficiency and reduces the carbon content of bottom ash and fly ash. The generated high-temperature flue gas is cooled by the multi-stage heating surface of the coal-fired boiler before being discharged from the boiler. The system's thermal efficiency is higher than that of other biomass coupled power generation technologies.

[0038] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures pointed out in the description, claims and drawings. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 A diagram of a biomass and coal-fired boiler coupled power generation system with an independent air supply system according to a first embodiment of the present invention is shown.

[0041] Figure 2 A diagram of a biomass and coal-fired boiler coupled power generation system with an independent air supply system according to a second embodiment of the present invention is shown.

[0042] Figure 3 A diagram of a biomass and coal-fired boiler coupled power generation system with a non-independent air supply system according to a third embodiment of the present invention is shown;

[0043] Figure 4 A diagram of a biomass and coal-fired boiler coupled power generation system with a non-independent air supply system according to a fourth embodiment of the present invention is shown.

[0044] Figure 5 A schematic diagram of a high-temperature flue gas measuring device is shown.

[0045] Figure reference numerals: 1. Biomass silo; 2. Biomass furnace; 3. Cyclone dust collector; 4. High-temperature flue gas measuring device; 5. Pulverized coal furnace; 6. Main burner; 7. High-temperature flue gas burner; 8. Separate burnout air burner; 9. Air preheater; 10. Low-temperature flue gas measuring device at boiler outlet; 11. Shut-off damper; 12. Adjusting damper; 13. Blower; 14. Hot primary air temperature measuring device; 15. Hot primary air flow measuring device; a1. Biomass boiler fly ash outlet; a2. Biomass boiler circulating ash outlet; a3. Biomass boiler bottom ash outlet; a4. Biomass boiler high-temperature dust-laden flue gas outlet; a5. Biomass boiler high-temperature flue gas outlet; a6. Coal-fired boiler hot primary air outlet; 4a. Flue gas sampling device; 4b. Flue gas pretreatment device; 4c. Flue gas flow, temperature, and composition measuring device. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of 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, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0047] The present invention provides a biomass and coal-fired boiler coupled power generation system. The system includes a biomass furnace 2, a cyclone dust collector 3, a high-temperature flue gas measuring device 4, a pulverized coal furnace 5 and an air preheater 9 connected in sequence. The pulverized coal furnace 5 includes a main burner 6, a high-temperature flue gas burner 7 and a separate burnout air burner 8. Figure 1 and Figure 3 In the middle, the high-temperature flue gas burner 7 is arranged between the main burner 6 and the separate burnout air burner 8; Figure 2 and Figure 4 In the middle, the high-temperature flue gas burner 7 is arranged in the area of ​​the main burner 6.

[0048] Figures 1 to 4 In this system, the biomass furnace 2 is connected to the biomass silo 1 and the air supply device, and the biomass furnace 2 is equipped with a high-temperature dust-laden flue gas outlet a4 and a biomass boiler bottom ash outlet a3. The cyclone dust collector 3 is equipped with a biomass boiler fly ash outlet a1, a biomass boiler circulating ash outlet a2, a biomass boiler high-temperature dust-laden flue gas inlet, and a biomass boiler high-temperature flue gas outlet a5; the biomass boiler fly ash outlet a1 and biomass boiler circulating ash outlet a2 are both connected to the bottom of the cyclone dust collector 3; the biomass boiler high-temperature dust-laden flue gas inlet is connected to the inlet of the cyclone dust collector 3; the biomass boiler high-temperature flue gas outlet a5 is connected to the high-temperature flue gas measuring device 4. The air preheater 9 is connected to the boiler outlet low-temperature flue gas measuring device 10, which is located on the flue at the outlet of the air preheater 9.

[0049] like Figure 5 The diagram shows a schematic of a high-temperature flue gas measuring device 4. This device consists of three parts: a flue gas sampling device 4a, a flue gas pretreatment device 4b, and a flue gas flow rate, temperature, and composition measuring device 4c, connected in sequence. The flue gas sampling device 4a is located in the channel of the high-temperature flue gas outlet a5 of the biomass boiler and is used to extract and sample the high-temperature flue gas. The flue gas pretreatment device 4b is used to pretreatment the extracted flue gas sample, further removing dust and maintaining its temperature to ensure the flue gas temperature is not lower than 100℃. The flue gas flow rate, temperature, and composition measuring device 4c is used to measure the temperature and flow rate of the flue gas sample and analyze its composition, which includes CO2, N2, O2, and H2O.

[0050] This invention discloses a biomass-coal boiler coupled power generation system. The air supply device can be configured in two different forms depending on the source of the primary air supplied to the bottom of the biomass furnace 2, such as… Figure 1 and Figure 2 As shown, the air supply device is an independent air supply system, including a blower 13, a shut-off baffle 11, and an adjusting baffle 12 connected in sequence, and the air supply device is connected to the bottom of the biomass furnace 2. Figure 3 and Figure 4 As shown, the air supply device is a non-independent air supply system, including a hot primary air temperature measuring device 14, a hot primary air flow measuring device 15, a shut-off baffle 11, and an adjusting baffle 12 connected in sequence. The outlet of the air supply device is connected to the bottom of the biomass furnace 2, and the inlet of the air supply device is connected to the hot primary air outlet a6 of the coal-fired boiler. The hot primary air outlet a6 of the coal-fired boiler is connected to the hot end of the air preheater 9.

[0051] In summary, this invention feeds biomass fuel into an insulated biomass furnace 2 for combustion. By controlling the primary air volume fed into the furnace bottom, the temperature and oxygen content of the high-temperature flue gas exiting the biomass furnace 2 are controlled. The high-temperature flue gas generated from the biomass furnace 2 is first purified by a cyclone dust collector 3, and the purified flue gas is then fed into the pulverized coal furnace 5. Depending on the nozzle position of the high-temperature flue gas burner 7, two methods are used: the first method places the high-temperature flue gas burner 7 between the main burner 6 and the separate burnout air burner 8; the second method places the high-temperature flue gas burner 7 in the middle area of ​​the main burner 6.

[0052] The primary air supplied to the bottom of the biomass furnace 2 is divided into two methods depending on its source: The first method uses an independent air supply system, where cold air is pressurized by a blower 13 and then supplied to the bottom of the biomass furnace 2. The airflow is regulated by adjusting the baffle 12 to control the combustion of biomass fuel within the furnace 2 and the temperature of the high-temperature flue gas at the outlet. The second method involves diverting a portion of the hot primary air from the air preheater 9 of the coal-fired boiler to the bottom of the biomass furnace 2 as the hot air for combustion. The advantage of the first method is that it reduces the correlation between biomass combustion and pulverized coal combustion in the furnace 5, preventing mutual interference in load regulation and facilitating independent and stable operation of the two systems. The air supply pressure and flow rate requirements of the biomass furnace 2 can be flexibly adjusted. The second method saves on the configuration of the blower 13. The air supplied to the biomass furnace 2 is heated to a higher temperature by the air preheater 9, which is beneficial for biomass combustion within the furnace 2. However, to maintain the high-temperature flue gas temperature, a larger flow rate of hot primary air is required to cool the flue gas.

[0053] The bottom of the biomass furnace 2 is equipped with a biomass boiler bottom ash outlet a3, which discharges the large ash formed after adiabatic combustion of biomass into the furnace. A cyclone dust collector 3 is installed at the upper outlet of the biomass furnace 2 to remove dust and purify the high-temperature flue gas generated after biomass combustion. After passing through the high-temperature flue gas measuring device 4, the high-temperature flue gas is sent into the coal-fired furnace 5. The fly ash captured by the cyclone dust collector 3 is processed according to its carbon content. If the carbon content of the fly ash is high (e.g., the carbon content of fly ash is greater than 1%), all or part of the fly ash is sent back to the biomass furnace 2 to continue to participate in the cycle combustion, further reducing the carbon content. When the carbon content is low (e.g., the carbon content of fly ash is less than or equal to 1%), the fly ash is directly discharged, leaving the system and sent to the fly ash collection device.

[0054] The aforementioned biomass furnace 2 is an insulated furnace lined with refractory materials and has no cooling device or system, ensuring that the biomass is fully combusted and generates high-temperature flue gas. The bottom ash after biomass combustion is discharged from the boiler through the ash discharge port at the bottom of the biomass furnace 2. Biomass fuel is fed into the biomass furnace from the biomass silo 1 via a conveying device. The combustion form of the biomass furnace 2 is grate, bubbling bed, fluidized bed, etc. The air required for combustion is supplied from the bottom of the biomass furnace 2.

[0055] The aforementioned high-temperature flue gas measuring device is used to detect the temperature, flow rate, and composition of the high-temperature flue gas. The flue gas temperature and O2 concentration in the flue gas composition are also used to monitor the combustion status and air supply volume of the biomass furnace 2. Its main principle is to adjust the air supply volume into the biomass furnace 2 by controlling the regulating baffle 12 on the air supply duct. This is used for biomass combustion and regulating the high-temperature flue gas temperature. With a certain amount of biomass fuel input, increasing the air supply volume increases the O2 concentration and decreases the flue gas temperature; conversely, decreasing the air supply volume decreases the O2 concentration and increases the flue gas temperature. During operation, the O2 concentration is used for coarse adjustment of the air supply volume, while the flue gas temperature is used for fine adjustment. A cascade control system is used to regulate the air supply volume of the biomass furnace 2.

[0056] The following explanation is based on the location of the high-temperature flue gas burner 7 and whether an independent blower 13 is installed in the biomass-coal boiler coupled power generation system. Figures 1 to 4 The working principle of the four devices.

[0057] Figure 3A diagram of a biomass and coal-fired boiler coupled power generation system with a non-independent air supply system according to a third embodiment of the present invention is shown. Its working principle is as follows: Biomass fuel stored in the biomass silo 1 is fed into the biomass furnace 2 for adiabatic combustion; high-temperature dust-laden flue gas is generated from the biomass boiler, which enters the cyclone dust collector 3 through the high-temperature dust-laden flue gas outlet a4 for high-temperature dust separation. Under the action of centrifugal force, the purified high-temperature dust-laden flue gas becomes high-temperature flue gas from the biomass boiler, which then enters the high-temperature flue gas measuring device 4 for flue gas flow rate, temperature, and composition measurement, and is subsequently fed into the pulverized coal furnace 5.

[0058] The high-temperature flue gas burner 7, located in the pulverized coal furnace 5, is positioned between the main burner 6 and the separate burnout air burner 8. The high-temperature flue gas from the biomass boiler is fed into the pulverized coal furnace 5 through the high-temperature flue gas burner 7 and combusted and mixed with the pulverized coal in the main burner 6. This process can also reduce the combustion temperature in the main burner 6 area. The temperature of the biomass high-temperature flue gas with lower oxygen content is lower than the temperature of the central flame in the pulverized coal furnace, which can effectively reduce NOx emissions generated during pulverized coal combustion.

[0059] The high-temperature fly ash separated by the cyclone separator 3 has its flow direction determined by its carbon content. When the carbon content is low, such as less than or equal to 1%, the biomass boiler fly ash leaves the system through the biomass boiler fly ash outlet a1. When the carbon content is high, such as greater than 1%, the fly ash separated by the cyclone separator enters the biomass furnace 2 through the biomass boiler circulating ash outlet a2, and is burned again to further reduce the carbon content. The biomass boiler bottom ash outlet a3 is located at the bottom of the biomass furnace 2 to discharge the large ash formed by biomass combustion in the biomass furnace 2 to the outside.

[0060] A portion of the primary hot air from the coal-fired boiler at the hot end outlet of the air preheater 9 is diverted and passes sequentially through the primary hot air temperature measuring device 14 and the primary hot air flow measuring device 15 for measuring the temperature and flow rate of the diverted primary hot air. After passing sequentially through the shut-off baffle 11 and the regulating baffle 12, the diverted primary hot air is sent to the bottom of the biomass furnace 2 for use as air for the combustion of biomass fuel in the furnace and for cooling the high-temperature flue gas.

[0061] A low-temperature flue gas measuring device 10 is installed on the cold-end flue gas passage of the air preheater 9 to detect the flue gas temperature at the boiler outlet and to serve as the calculation basis for the heat of the biomass high-temperature flue gas entering the pulverized coal furnace 5. Through thermodynamic calculation methods, the heat of biomass fed into the pulverized coal furnace 5 can be detected and measured in real time, thereby accurately measuring the electrical power and electricity generated by biomass in the coupled power generation system.

[0062] Figure 4A diagram of a biomass and coal-fired boiler coupled power generation system with a non-independent air supply system according to a fourth embodiment of the present invention is shown. Figure 3 The difference lies in the location of the high-temperature flue gas burner 7, which is situated within the main burner 6 area. It directs the high-temperature flue gas generated in the biomass furnace 2 into the middle of the main burner 6. Its advantage is that it can adapt to the combustion conditions of the pulverized coal furnace 5 under different loads. The high-temperature flue gas from the biomass boiler can effectively reduce the combustion temperature in the main burner 6 area, achieving staged combustion of pulverized coal and reducing NOx emissions during pulverized coal combustion. Other thermal system devices' connection relationships, functions, roles, and working principles are also discussed. Figure 3 The same applies, so I won't repeat myself.

[0063] Figure 1 A schematic diagram of a biomass and coal-fired boiler coupled power generation system with an independent air supply system according to a first embodiment of the present invention is shown; the device is coupled with... Figure 3 The difference lies in the establishment of an independent biomass boiler air supply system. Instead of using the hot primary air diversion method in the pulverized coal furnace 5, an independent blower 13 is installed to pressurize the cold air, which then passes through the shut-off baffle 11 and the regulating baffle 12 before being sent to the bottom of the biomass furnace 2. Furthermore, the method for calculating the biomass heat entering the pulverized coal furnace 5 differs from... Figure 3 The calculation method for the device requires the use of the high-temperature flue gas measuring device 4 and the low-temperature flue gas measuring device 10 at the boiler outlet to calculate the corresponding heat and proportion, and at the same time calculate the power generation and electricity generation of biomass in the coupled system.

[0064] Figure 2 A diagram of a biomass and coal-fired boiler coupled power generation system according to a second embodiment of the present invention is shown; the biomass heat calculation method, the power generation capacity and electricity generated by the biomass in the coupled system are described. Figure 1 The principle of the device is the same as that in the previous one, so I will not go into details.

[0065] The basic principles of heat measurement for the different types of apparatus diagrams described above are as follows:

[0066] For devices with independent air supply systems, such as Figure 1 and Figure 2 As shown, the temperature of the high-temperature flue gas entering the pulverized coal furnace 5 of the biomass boiler is T1, in °C; the volumetric flow rate of the high-temperature flue gas in the biomass boiler is V, in Nm³. 3 / s; The main components of high-temperature flue gas from biomass boilers are N2, O2, CO2, and H2O, with corresponding volume percentages of γ N2 γ O2 γ CO2 γ H2OAll temperatures were measured by the high-temperature flue gas measuring device 4. The low-temperature flue gas temperature at the outlet of the air preheater 9, T2 (in °C), was measured by the low-temperature flue gas measuring device 10 at the boiler outlet. The total enthalpy H of the high-temperature flue gas at temperature T1 is... T1 It is the sum of the total enthalpies corresponding to different components (N2, O2, CO2, H2O) in the flue gas, where the enthalpies per unit volume of N2, O2, CO2, and H2O are h(T1, N2), h(T1, O2), h(T1, CO2), and h(T1, H2O), respectively, with units of kJ / Nm³. 3 Then the total enthalpy of the high-temperature flue gas at temperature T1 is:

[0067] H T1 =V*(h(T1, N2)*γ N2 +h(T1, O2)*γ O2 +h(T1, CO2)*γ CO2 +h(T1,H2O)*γ H2O (1)

[0068] Among them, H T1 T1 represents the total enthalpy of the high-temperature flue gas at temperature T1, in kW; V represents the volumetric flow rate of the high-temperature flue gas, in Nm³. 3 / s; h(T1, N2), h(T1, O2), h(T1, CO2), and h(T1, H2O) are the enthalpy per unit volume of N2, O2, CO2, and H2O at temperature T1, respectively, in kJ / Nm³. 3 ;γ N2 γ O2 γ CO2 γ H2O These represent the volume percentages of N2, O2, CO2, and H2O in the high-temperature flue gas of a biomass boiler.

[0069] Similarly, the total enthalpy corresponding to the low-temperature flue gas at boiler exhaust temperature T2 is H. T2 ,but:

[0070] H T2 =V*(h(T2, N2)*γ N2 +h(T2, O2)*γ O2 +h(T2, CO2)*γ CO2 +h(T2,H2O)*γ H2O (2)

[0071] Among them, H T2 T2 represents the total enthalpy of the low-temperature flue gas at temperature T2, in kW; V represents the volumetric flow rate of the high-temperature flue gas, in Nm³. 3 / s; h(T2, N2), h(T2, O2), h(T2, CO2), and h(T2, H2O) are the enthalpy per unit volume of N2, O2, CO2, and H2O at temperature T2, respectively, in kJ / Nm³. 3 ;γ N2 γ O2 γ CO2 γ H2O These represent the volume percentages of N2, O2, CO2, and H2O in the high-temperature flue gas of a biomass boiler.

[0072] The heat absorbed by the high-temperature flue gas after biomass combustion in the pulverized coal furnace 5 is denoted as Q, with units of kW; its calculation formula is:

[0073] Q = H T1 -H T2 =V*[(h(T1, N2)-h(T2, N2))*γ N2 +(h(T1,O2)-h(T2,O2))*γ O2 +(h(T1,CO2)-h(T2,CO2))*γ CO2 +(h(T1,H2O)-h(T2,H2O))*γ H2O (3)

[0074] For the above formula (3), h(T2, N2), h(T2, O2), h(T2, CO2), h(T2, H2O) and h(T1, N2), h(T1, O2), h(T1, CO2), h(T1, H2O) are only related to the flue gas temperatures T2 and T1 and the flue gas composition. Therefore, as long as the high-temperature flue gas flow rate V, the high-temperature flue gas temperature T1, the low-temperature flue gas temperature T2, and the volume percentage of different flue gas components are measured, the biomass heat Q absorbed by the coal-fired furnace 5 can be calculated in real time.

[0075] For devices with non-independent air supply systems, such as Figure 3 and Figure 4 As shown, the volumetric flow rate of the hot primary air diverted from the outlet of the air preheater 9 to the biomass furnace 2 is V0, in Nm³. 3 / s, the primary air temperature is T3, in °C. The total enthalpy of the primary air at temperature T3 is H. T3 The calculation method is as follows:

[0076] H T3 =V0*(h(T3, N2)*0.79+h(T3, O2)*0.21) (4)

[0077] Where h(T3, N2) and h(T3, O2) are the enthalpy per unit volume of N2 and O2 at temperature T3, respectively, in kJ / Nm³. 3V0 is the volumetric flow rate of the hot primary air diverted from the outlet of the air preheater 9 to the biomass furnace 2, in Nm³. 3 / s; The temperature of the high-temperature flue gas entering the pulverized coal furnace 5 is T1, in °C; The flue gas volumetric flow rate is V, in Nm³. 3 / s; The main components of the high-temperature flue gas are N2, O2, CO2, and H2O, with corresponding volume percentages of γ N2 γ O2 γ CO2 γ H2O The outlet flue gas temperature of air preheater 9 is T2, in °C.

[0078] The heat absorbed by the high-temperature flue gas after biomass combustion by the pulverized coal boiler is denoted as Q', in kW.

[0079] Q' = H T1 -H T2 -H T3 =V*[(h(T1, N2)-h(T2, N2))*γ N2 +(h(T1,O2)-h(T2,O2))*γ O2 +(h(T1,CO2)-h(T2,CO2))*γ CO2 +(h(T1,H2O)-h(T2,H2O))*γ H2O ]-V0*(h(T3,N2)*0.79+h(T3,O2)*0.21) (5)

[0080] For the above formula (5), h(T2, N2), h(T2, O2), h(T2, CO2), h(T2, H2O) and h(T1, N2), h(T1, O2), h(T1, CO2), h(T1, H2O), h(T3, N2), h(T3, O2) are only related to the flue gas temperature T2, T1, T3 and the flue gas composition. Therefore, as long as the high-temperature flue gas flow rate V, the split hot primary air flow rate V0, the high-temperature flue gas temperature T1, the low-temperature flue gas temperature T2, the hot primary air temperature T3 and the volume percentage of different flue gas components are measured, the biomass heat Q' absorbed by the coal-fired furnace 5 can be calculated in real time.

[0081] Figures 1 to 4 In a biomass-coal-fired boiler coupled power generation system, the total heat absorption of the coal-fired furnace 5 is Q. b The calculation formula is as follows:

[0082] Q b =m FW *(h ST -h FW )+m RH *(h RHO -h RHI )+mGJ *(h ST -h GJ )+m RJ *(h RHO -h RJ (6)

[0083] Where, m FW The flow rate of the water supply is expressed in kg / s; h ST The enthalpy per unit mass of superheated steam outlet, expressed in kJ / kg; h FW The enthalpy per unit mass of water is expressed in kJ / kg; m RH The inlet flow rate of reheat steam is expressed in kg / s or h. RHO The enthalpy per unit mass of reheat steam outlet, expressed in kJ / kg; h RHI The unit mass enthalpy of the reheat steam inlet, expressed in kJ / kg; m GJ The flow rate of the superheater desuperheating water, expressed in kg / s; h GJ The enthalpy per unit mass of the superheater desuperheating water, expressed in kJ / kg; m RJ The flow rate of desuperheating water in the reheater, expressed in kg / s; h RJ The enthalpy per unit mass of the desuperheating water in the reheater is expressed in kJ / kg.

[0084] For large coal-fired boilers, the coal-fired furnace generally includes four major structural components: water-cooled walls, superheaters, reheaters, and economizers. After the feedwater enters the boiler, it first enters the economizer to absorb heat from the flue gas at the boiler tail. The heated feedwater then enters the steam drum, which, as a steam-water junction, separates the steam-water mixture generated in the water-cooled walls. The saturated water and the feedwater from the economizer outlet mix and continue to circulate and heat in the water-cooled walls, absorbing radiant heat from the furnace interior for evaporation. The saturated steam, after passing through the steam-water separation inside the steam drum, enters the superheater to be heated into superheated steam that meets the requirements of the turbine. It then enters the high-pressure cylinder of the turbine to expand and do work. The steam discharged from the high-pressure cylinder, with its temperature and pressure reduced, re-enters the boiler reheater to absorb heat and generate reheated steam that meets the requirements. This reheated steam then enters the intermediate-pressure and low-pressure cylinders of the turbine to expand and do work for power generation. In order to keep the temperature of superheated steam and reheated steam within limits during boiler operation, superheated desuperheating water and reheated desuperheating water are installed respectively. The desuperheating water from the feedwater and feedwater pump taps is used to spray water to desuperheat the superheated steam and reheated steam to bring them to the design temperature.

[0085] therefore, Figure 1 and Figure 2 The power generation P generated by the heat from biomass combustion in the biomass and coal-fired boiler coupled power generation system shown is... b The calculation formula is:

[0086] P b =Q / Q b *P e (7)

[0087] Among them, P e P represents the total power output of the coupled power generation system, expressed in kW. b The power generation capacity of biomass is expressed in kW.

[0088] The formula for calculating the power generation Pc generated by the heat from the combustion of pulverized coal in coal-fired furnace 5 is as follows:

[0089] P c =P e -P b =(1-Q / Q) b )*P e (8)

[0090] Figure 3 and Figure 4 The power generation P generated by the heat from biomass combustion in the biomass and coal-fired boiler coupled power generation system shown is... b The calculation formula is:

[0091] P b ' = Q' / Q b *P e (9)

[0092] Among them, P e P represents the total power output of the coupled power generation system, expressed in kW. b ' represents the power generation capacity of biomass, measured in kW;

[0093] The power generation P generated by the heat from the combustion of pulverized coal in the coal-fired furnace 5 c The formula for calculating ' is:

[0094] P c ' = P e -P b ' = (1 - Q' / Q) b )*P e (10)

[0095] By calculating formulas (1)-(10), the biomass power generation and coal-fired power generation in the coupled power generation system can be calculated in real time by integrating formulas (7), (9) or (8), (10) over time.

[0096]

[0097] Where P is P b Or P bWhen ', W represents the biomass power generation of the coupled power generation system within the time interval [t1, t2], in kWh; when P is P c Or P c At time ', W represents the amount of coal-fired power generated by the coupled power generation system within the time interval [t1, t2], in kWh.

[0098] In summary, this invention, by setting up a separate furnace for burning biomass, generates high-temperature flue gas from the biomass fuel. After dust removal, the clean, high-temperature flue gas, after metering and composition analysis, is sent to the furnace of a coal-fired boiler, where it is burned together with pulverized coal. The pulverized coal boiler, by using the high-temperature flue gas generated from biomass combustion, can reduce coal consumption. The high-temperature biomass flue gas is cooled by the various heating surfaces of the pulverized coal boiler and finally discharged from the boiler through an air preheater. By measuring the flow rate, temperature, and composition of the flue gas fed into the pulverized coal furnace, as well as the flue gas temperature at the air preheater outlet, the heat input into the pulverized coal furnace can be calculated in real time, thereby allowing for the calculation of the power generation from biomass co-firing.

[0099] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A biomass-coal boiler coupled power generation system, characterized in that, The system includes a biomass furnace (2), a cyclone dust collector (3), a high-temperature flue gas measuring device (4), a pulverized coal furnace (5), and an air preheater (9) connected in sequence. The pulverized coal furnace (5) includes a main burner (6), a high-temperature flue gas burner (7), and a separate burnout air burner (8). The biomass furnace (2) is an insulated furnace. The high-temperature flue gas burner (7) is arranged between the main burner (6) and the separate burnout air burner (8); or the high-temperature flue gas burner (7) is arranged in the area of ​​the main burner (6); The high-temperature flue gas measuring device (4) includes a flue gas sampling device (4a), a flue gas pretreatment device (4b), and a flue gas flow rate, temperature, and composition measuring device (4c) connected in sequence; the flue gas sampling device (4a) is arranged in the channel of the high-temperature flue gas outlet (a5) of the biomass boiler. The boiler outlet low-temperature flue gas measuring device (10) is arranged on the flue at the outlet of the air preheater (9); The outlet of the air supply device is connected to the bottom of the biomass furnace (2), and the inlet of the air supply device is connected to the hot primary air outlet (a6) of the coal-fired boiler; the hot primary air outlet (a6) of the coal-fired boiler is connected to the air preheater (9). The cyclone dust collector (3) is equipped with a biomass boiler fly ash outlet (a1), a biomass boiler circulating ash outlet (a2), a biomass boiler high-temperature dust-laden flue gas inlet, and a biomass boiler high-temperature flue gas outlet (a5); wherein... The fly ash outlet (a1) and circulating ash outlet (a2) of the biomass boiler are both connected to the bottom of the cyclone dust collector (3); the high-temperature dust-laden flue gas inlet of the biomass boiler is connected to the inlet of the cyclone dust collector (3); and the high-temperature flue gas outlet (a5) of the biomass boiler is connected to the high-temperature flue gas measuring device (4).

2. The system according to claim 1, characterized in that, The biomass furnace (2) is connected to the biomass silo (1) and the air supply device respectively, and the biomass furnace (2) is provided with a high-temperature dusty flue gas outlet (a4) and a biomass boiler bottom ash outlet (a3).

3. The system according to claim 2, characterized in that, The air supply device includes a hot primary air temperature measuring device (14), a hot primary air flow measuring device (15), a shut-off baffle (11), and an adjusting baffle (12) connected in sequence.

4. The method for calculating the power generation of a biomass and coal-fired boiler coupled power generation system as described in claim 1 or 3, characterized in that, Biomass power generation of coupled power generation system ;P b ' represents the power generation capacity of electricity generated by the heat from biomass combustion, P b '=Q' / Q b *P e ; Among them, P e Q' represents the total power generation of the biomass-coal boiler coupled power generation system; Q' represents the heat absorbed by the high-temperature flue gas after biomass combustion in the pulverized coal furnace (5); Q b The pulverized coal furnace (5) absorbs heat as a whole.

5. The method according to claim 4, characterized in that, The formula for calculating the heat Q' absorbed by the high-temperature flue gas after biomass combustion in the pulverized coal furnace (5) is as follows: Q'=V﹡[(h(T1,N2)-h(T2,N2))*γ N2 +(h(T1,O2)-h(T2,O2))*γ O2 +(h(T1,CO2)-h(T2,CO2))*γ CO2 +(h(T1,H2O)-h(T2,H2O))*γ H2O ]-V0*(h(T3,N2)*0.79+h(T3,O2)*0.21); Where h(T1, N2), h(T1, O2), h(T1, CO2), and h(T1, H2O) are the enthalpy per unit volume of N2, O2, CO2, and H2O at temperature T1, respectively; h(T2, N2), h(T2, O2), h(T2, CO2), and h(T2, H2O) are the enthalpy per unit volume of N2, O2, CO2, and H2O at temperature T2, respectively; h(T3, N2) and h(T3, O2) are the enthalpy per unit volume of N2 and O2 at temperature T3, respectively; γ N2 γ O2 γ CO2 γ H2O These represent the volume percentages of N2, O2, CO2, and H2O in the high-temperature flue gas, respectively. T1 is the temperature of the high-temperature flue gas entering the pulverized coal furnace (5), T2 is the flue gas temperature at the outlet of the air preheater (9), T3 is the temperature of the hot primary air, V is the volumetric flow rate of the high-temperature flue gas, and V0 is the volumetric flow rate of the hot primary air diverted from the outlet of the air preheater (9) to the biomass furnace (2).

6. The method according to claim 5, characterized in that, The overall heat absorption Q of the pulverized coal furnace (5) b The calculation formula is: Q b =m FW *(h ST -h FW )+m RH *(h RHO -h RHI )+m GJ *(h ST -h GJ )+m RJ *(h RHO -h RJ ) Where, m FW h is the water flow rate. ST h is the enthalpy per unit mass of the superheated steam outlet. FW Enthalpy per unit mass of water; m RH h is the inlet flow rate of reheat steam. RHO h is the enthalpy per unit mass of the reheat steam outlet. RHI m is the enthalpy per unit mass of the reheat steam inlet. GJ The flow rate of desuperheating water for the superheater; h GJ Enthalpy per unit mass of the superheater desuperheating water; m RJ The flow rate of desuperheating water for the reheater; h RJ The enthalpy per unit mass of the desuperheating water for the reheater.

7. The method according to claim 5, characterized in that, The coal-fired power generation capacity of the coupled power generation system is ; Where W4 represents the coal-fired power generation of the coupled power generation system within the time interval [t1, t2]; P c ' is the power generation generated by the heat from the combustion of pulverized coal in the pulverized coal furnace (5), P c ' = (1 - Q' / Q) b )*P e .

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