Refuse derived fuel blending combustion system and method for peak regulation of large coal-fired boiler

Abstract

The invention belongs to the technical field of energy and chemical industry, and mainly relates to a refuse derived fuel blending combustion system and a refuse derived fuel blending combustion method for peak regulation of a large coal-fired boiler. The system controls opening and closing of a smoke exhaust port of the coal-fired boiler, when the coal-fired boiler normally operates at full load, the smoke exhaust port of the coal-fired boiler is closed, and the smoke exhaust port of the coal-fired boiler is opened and closed; superheated steam generated by boiler flue gas heating enters a steam power generation system through a steam port, and the coal-fired boiler is completely used for heating feed water to generate steam to push a turbine power generation mechanism to generate power; when electricity is used in a low ebb, flue gas generated by the coal-fired boiler is supplied to the gasification furnace and is combined with the garbage drying and separating mechanism and the coal-fired boiler system to produce fuel with high calorific value and good combustibility, boiler combustion is stabilized, and the problem that combustion is unstable in the peak shaving process of the coal-fired boiler is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of energy and chemical industry, and mainly relates to a refuse-derived fuel blending combustion system and a refuse-derived fuel blending combustion method for peak shaving of large coal-fired boilers. Background Art

[0002] Domestic waste sorting is one of the core initiatives in China's efforts to promote ecological civilization. Currently, the design calorific value of domestic waste-to-energy plants in China is generally between 6MJ / kg and 8MJ / kg. As waste sorting policies become more widespread and living standards continue to improve, the calorific value of urban domestic waste is expected to rise annually.

[0003] Coupling large-scale coal-fired power plant units with municipal solid waste (MSW) is a promising waste management method. On the one hand, it can harmlessly and minimise the amount of MSW, reducing the construction costs of new waste incineration plants. On the other hand, large-scale coal-fired units offer high fuel energy efficiency, significantly increasing the calorific value of MSW. Currently, many coal-fired power plants incinerate MSW by directly mixing it with coal. However, these existing waste incineration methods have several drawbacks, including the generation of large amounts of flue gas during boiler combustion, which creates pollution. During peak-shaving power generation, coal-fired power plants operate at low load, reducing the total coal feed, resulting in poor furnace flame fill and a drop in burner temperature, which weakens combustion stability. Summary of the Invention

[0004] One of the problems that the present invention aims to solve is the background problem.

[0005] To this end, the present invention provides a garbage-derived fuel co-combustion system for peak-shaving of large-scale coal-fired boilers, which can fully utilize the steam and high-temperature flue gas generated by the coal-fired boiler to avoid flue gas emissions polluting the environment. In addition, the classified high-calorific value garbage and recycled fuel oil and gas help to achieve stable combustion during the peak-shaving operation of the boiler. When the boiler needs to operate at a peak-shaving operation, the high-temperature flue gas is extracted to achieve the effect of energy storage and produce fuel with high calorific value and good combustibility, thereby solving the problem of unstable combustion.

[0006] The technical solution adopted by the present invention to solve its technical problem is:

[0007] A waste-derived fuel blending system for peak shaving of large coal-fired boilers, comprising:

[0008] A coal-fired boiler, wherein the coal-fired boiler is provided with a steam outlet for discharging steam and a flue gas outlet for discharging high-temperature flue gas;

[0009] a gasifier, the gasifier being connected to a smoke extraction port;

[0010] A garbage drying and separation mechanism, which is connected to both the gasifier and the coal-fired boiler. The mechanism is used to dry the garbage and separate it into low-calorific value garbage and high-calorific value garbage. The mechanism can crush the low-calorific value garbage and transport it to the gasifier, and supply the high-calorific value garbage to the coal-fired boiler.

[0011] A steam power generation system, comprising a generator and a plurality of pressure cylinder steam turbines connected in series, the steam power generation system receiving steam output from a steam port, and connected to a garbage drying and separation mechanism;

[0012] The gas-liquid separation mechanism is arranged between the gasifier and the coal-fired boiler, and is used to separate the gas-liquid mixture discharged from the gasifier into combustible gas and tar to supply the coal-fired boiler.

[0013] Furthermore, the gas-liquid separation mechanism includes a separator, a gasification gas tank and an oil tank. The separator receives the gas-liquid mixture from the gasifier. The gasification gas tank and the oil tank are both connected to the separator. The ends of the gasification gas tank and the oil tank away from the separator are both connected to the coal-fired boiler.

[0014] Furthermore, the gas-liquid separation mechanism also includes a heat exchanger and a blower. The heat exchanger is connected between the separator and the gasifier. The heat exchanger is provided with a first air inlet, a second air inlet, a first air outlet and a second air outlet. The first air inlet and the first air outlet are set as the inlet and outlet of the same gas circuit, and the second air inlet and the second air outlet are set as the inlet and outlet of the same gas circuit. The gasifier is connected to the first air inlet of the heat exchanger through a pipeline, the first air outlet is connected to the separator, the blower is connected to the second air inlet of the heat exchanger, and the second air outlet is connected to the coal-fired boiler.

[0015] Furthermore, the multiple pressure cylinder turbines connected in series in the steam power generation system include a high-pressure cylinder turbine, a medium-pressure cylinder turbine and a low-pressure cylinder turbine, the high-pressure cylinder turbine is connected to the coal-fired boiler, the low-pressure cylinder turbine is connected to the generator, and the low-pressure cylinder turbine is connected to the garbage drying and separation mechanism.

[0016] Furthermore, the garbage drying and separation mechanism includes a dryer, a wind separator, a garbage crusher and an extruder. The steam outlet of the low-pressure cylinder turbine is connected to the steam inlet of the dryer, the dryer is connected to the wind separator, the wind separator is connected to the garbage crusher and the extruder, the end of the garbage crusher away from the wind separator is connected to the gasifier, and the end of the extruder away from the wind separator supplies materials to the coal-fired boiler.

[0017] A process for the combustion of refuse-derived fuels in a refuse-derived fuel combustion system for peak load regulation of large coal-fired boilers, based on the above-described system, performs the following steps during a low electricity consumption period or when the power grid is in oversupply:

[0018] Step 1: The boiler output is reduced to below 30%, and the excess electricity from the power grid is used to power the wind power sorter, garbage crusher, extruder, and pellet fuel crusher;

[0019] In step 2, the low-calorific value waste separated by the waste drying and separation mechanism is crushed to a particle size of less than 50 microns and then fed into the gasifier. The high-calorific value waste separated by the waste drying and separation mechanism is compressed into pelletized fuel and crushed before being fed into the coal-fired boiler for combustion support.

[0020] Step 3: High-temperature flue gas at 800-900°C is drawn from the coal-fired boiler and fed into the gasifier to gasify the low-calorific value garbage. The gasifier generates a gas-liquid mixed gas at 600-700°C and outputs it to the heat exchanger.

[0021] Step 4: The gasified gas of the gas-liquid mixture is cooled to 50-90°C by a heat exchanger and separated into gas and fuel oil by a separator, and supplied to the coal-fired boiler for auxiliary combustion.

[0022] Furthermore, the air fed into the heat exchanger by the blower undergoes countercurrent heat exchange with the gas-liquid mixture in the heat exchanger, raising its temperature to 400-500°C before entering the coal-fired boiler as secondary air for auxiliary combustion. Furthermore, when the boiler is operating normally at full load, the flue gas outlet is closed, and the boiler flue gas is used entirely to heat feedwater, generating steam that drives the steam turbine generator system for power generation.

[0023] The beneficial effect of the present invention is that the present application classifies and utilizes the calorific value of garbage, integrates garbage sorting with the coal-fired boiler system, and enters different furnace entry processes according to the calorific value. The classified high-calorific value garbage, fuel oil and gas help to stabilize combustion during the peak operation of the boiler, and when the boiler needs to operate at a peak value, high-temperature flue gas is extracted to achieve the effect of energy storage. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The present invention will be further described below with reference to the accompanying drawings and examples.

[0025] Figure 1 The diagram is a structural diagram of a refuse-derived fuel blending system for peak load regulation in large coal-fired boilers according to the present invention. DETAILED DESCRIPTION

[0026] The present invention will now be described in further detail with reference to the accompanying drawings, which are simplified schematic diagrams that illustrate the basic structure of the present invention in a schematic manner.

[0027] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, features defined as "first" or "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0028] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0029] A garbage-derived fuel blending system for peak-shaving in large coal-fired boilers comprises a coal-fired boiler, a gasifier, a garbage drying and separation mechanism, a gas-liquid separation mechanism, and a steam power generation system.

[0030] Specifically, the garbage drying and separation mechanism includes a garbage crusher, a wind sorter, a dryer, an extruder, and a molded fuel crusher; the gas-liquid separation mechanism includes a heat exchanger, a blower, a gasification gas tank, and an oil tank; the steam power generation system includes multiple pressure cylinders and generators connected in series, and the multiple pressure cylinders are respectively a high-pressure cylinder turbine, a medium-pressure cylinder turbine, and a low-pressure cylinder turbine.

[0031] Specifically, the coal-fired boiler is provided with a flue gas outlet and a steam outlet. The furnace outlet of the coal-fired boiler is the steam outlet, where a superheater is provided. The steam discharged from the coal-fired boiler through the superheater passes through the high-pressure cylinder steam turbine, the medium-pressure cylinder steam turbine and the low-pressure cylinder steam turbine in sequence. The steam discharged from the low-pressure cylinder steam turbine enters the dryer to provide heat for the dryer. The water vapor discharged from the dryer can be discharged into the steam drain machine to separate the condensed water. The separated condensed water can be transported to the superheater in the coal-fired boiler for cooling. The steam discharged from the low-pressure cylinder steam turbine can also enter the generator to generate electricity.

[0032] The smoke exhaust port of the gasifier is connected to the coal-fired boiler, and the coal-fired boiler transports the high-temperature smoke inside it into the gasifier. A slag discharge port is provided at the bottom of the gasifier, which is used to discharge the residue in the gasifier. An exhaust port is provided at the top of the gasifier. The heat exchanger is provided with a first air inlet, a second air inlet, a first air outlet and a second air outlet. The first air inlet and the first air outlet are set as the inlet and outlet of the same gas path, and the second air inlet and the second air outlet are set as the inlet and outlet of the same gas path. The exhaust port of the gasifier is connected to the first air inlet of the heat exchanger through a pipeline, and the first air outlet is connected to the gasification gas tank and the oil tank through a separator. The separator separates the gas-liquid mixture discharged from the gasifier by the heat exchanger into gas and oil, which are respectively sent to the gasification gas tank and the oil tank. The oil tank and the gasification gas tank are respectively connected to the coal-fired boiler to supply energy raw materials for the coal-fired boiler.

[0033] The steam exhaust from the steam turbine also supplies heat to the dryer. A steam trap is connected to the dryer to treat the exhaust steam. The dryer, used to process domestic waste, is connected to a wind turbine separator. The wind turbine separator has two discharge ports: the first discharge port discharges low-calorific-value waste, and the second discharges high-calorific-value waste. The first discharge port is connected to a gasifier via a garbage pulverizer. The low-calorific-value waste is crushed and fed into the gasifier for discharge through the slag discharge port.

[0034] The second discharge port of the dryer is connected to the extruder, which extrude the high calorific value garbage into molded fuel. The molded fuel can be stored in a storage bin for future use, or it can be sent to a coal-fired boiler through a molded fuel crusher to provide combustion raw materials for the coal-fired boiler.

[0035] Furthermore, the second air inlet of the heat exchanger is connected to the blower, which inputs cold air into the heat exchanger to cool the gas-liquid mixture coming from the gasifier. The hotter air after heat exchange is discharged to the coal-fired boiler through the second air outlet.

[0036] The implementation principles of this application are:

[0037] When a coal-fired boiler is operating normally at full load, the boiler's flue gas outlet is closed, and the boiler flue gas enters the steam power generation system through the steam outlet. It then passes through the high-pressure, intermediate-pressure, and low-pressure turbines. The coal-fired boiler is then used entirely to heat feedwater, generating steam that drives the turbine generator. Steam from the low-pressure turbine outlet goes to a dryer to dry the domestic waste, then to a steam trap, where the condensate is recycled back to the feedwater system.

[0038] When electricity consumption is low or the grid power supply exceeds demand, the boiler needs to be operated at peak load, and the boiler output drops below 30%. At this time, in order to stabilize boiler combustion, the boiler fuel supply should be supplemented with high calorific value fuel such as oil and gas. At this time, perform the following operations:

[0039] 1. Utilize the excess electricity from the power grid when the power supply exceeds the demand to power the wind power sorter, garbage crusher, extruder, and briquette fuel crusher;

[0040] 2. The dried domestic waste is sorted by a wind-powered sorting machine to obtain low-density, high-calorific value waste (calorific value higher than 4000kcal / kg) such as paper and plastic blown out by the wind, and high-density, low-calorific value waste (calorific value lower than 4000kcal / kg) blown off by the wind, which are then stored for future use;

[0041] 3. The sorted low-calorific value waste is crushed in a garbage crusher (to a particle size of less than 50 microns to facilitate pneumatic conveying) and then fed into a gasifier. High-temperature flue gas (800-900°C, preferably 800°C) is extracted from a coal-fired boiler and fed into the gasifier to gasify the low-calorific value waste, producing gasification gas (600-700°C, preferably 700°C). The gasification gas contains combustible gases such as hydrogen, carbon monoxide, and methane, as well as tar with a relatively high molecular weight. The combustible gas components of the specific embodiment are shown in the following table:

[0042] temperature Air coefficient <![CDATA[H2]]> CO <![CDATA[CH4]]> <![CDATA[C2H6]]> <![CDATA[C2H4]]> 650 0.3 10.23 8.98 2.05 1.33 1.27 650 0.4 9.13 11.19 1.92 1.32 0.92 650 0.5 8.97 8.54 2.26 1.39 1.18 750 0.3 14.58 10.17 3.96 1.31 2.28 750 0.4 11.05 8.65 2.86 1.23 1.67 750 0.5 12.37 9.72 3.47 1.25 1.92 850 0.3 18.27 16.85 5.08 1.21 3.30 850 0.4 15.37 13.91 3.79 1.17 2.68 850 0.5 15.52 14.26 4.23 1.18 2.90

[0043] The gasified gas is cooled by the heat exchanger and countercurrently exchanges heat with the air from the blower (30°C) to cool it down to 50-90°C. Among them, components such as H2, CO, CH4, C2H6, C2H4 do not condense into combustible gases, while benzene, toluene, naphthalene, xylene, etc. are condensed into tar after cooling, and the combustible gas and tar form a gas-liquid mixture; the condensed gas-liquid mixture (50-90°C) is separated into fuel gas and fuel oil by a separator, and enters the gas tank and oil tank respectively; the outlets of the gas tank and the oil tank are connected to the coal-fired boiler, and the gas and oil assist the combustion of the coal-fired boiler; under low load, the fuel supply is reduced, the furnace temperature is reduced, the ignition point of fuel oil and gas is low, and it is easy to ignite, which is conducive to achieving low-load stable combustion in the boiler. Therefore, the above measures are conducive to low-load stable combustion;

[0044] 4. The high calorific value waste that has been sorted out is extruded to produce briquette fuel; some of the briquette fuel is stored in a warehouse for future use or for sale, while some is crushed by a briquette fuel crusher (to a particle size of less than 50 microns to facilitate pneumatic conveying) and fed into a coal-fired boiler for auxiliary combustion;

[0045] 5. Air (30°C) exchanges heat in a countercurrent with the gasified gas in the heat exchanger. After being heated to 400-500°C, preferably 500°C, it enters the coal-fired boiler furnace as secondary air to assist combustion. At low loads, fuel supply is reduced, lowering the furnace temperature. Raising the secondary air temperature facilitates stable combustion at low loads.

[0046] With the above-described preferred embodiments of the present invention as a guide, and with reference to the above description, relevant personnel are fully capable of making various changes and modifications without departing from the technical spirit of this invention. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A waste-derived fuel blending system for peak load regulation in large coal-fired boilers, characterized in that: include, A coal-fired boiler, wherein the coal-fired boiler is provided with a steam outlet for discharging steam and a flue gas outlet for discharging high-temperature flue gas; a gasifier, the gasifier being connected to a smoke extraction port; A garbage drying and separation mechanism, which is connected to both the gasifier and the coal-fired boiler. The mechanism is used to dry the garbage and separate it into low-calorific value garbage and high-calorific value garbage. The mechanism can crush the low-calorific value garbage and transport it to the gasifier, and supply the high-calorific value garbage to the coal-fired boiler. A steam power generation system, comprising a generator and a plurality of pressure cylinder steam turbines connected in series, the steam power generation system receiving steam output from a steam port, and connected to a garbage drying and separation mechanism; The gas-liquid separation mechanism is arranged between the gasifier and the coal-fired boiler, and is used to separate the gas-liquid mixture discharged from the gasifier into combustible gas and tar to supply the coal-fired boiler.

2. The refuse-derived fuel blending system for peak load shaving of large coal-fired boilers according to claim 1 is characterized in that: The gas-liquid separation mechanism includes a separator, a gasification gas tank and an oil tank. The separator receives the gas-liquid mixture from the gasifier. The gasification gas tank and the oil tank are both connected to the separator. The ends of the gasification gas tank and the oil tank away from the separator are both connected to the coal-fired boiler.

3. The refuse-derived fuel blending system for peak load shaving of large coal-fired boilers according to claim 2 is characterized in that: The gas-liquid separation mechanism also includes a heat exchanger and a blower. The heat exchanger is connected between the separator and the gasifier. The heat exchanger is provided with a first air inlet, a second air inlet, a first air outlet and a second air outlet. The first air inlet and the first air outlet are set as the inlet and outlet of the same gas circuit, and the second air inlet and the second air outlet are set as the inlet and outlet of the same gas circuit. The gasifier is connected to the first air inlet of the heat exchanger through a pipeline, the first air outlet is connected to the separator, the blower is connected to the second air inlet of the heat exchanger, and the second air outlet is connected to the coal-fired boiler.

4. The refuse-derived fuel blending system for peak load regulation of large coal-fired boilers according to claim 1 is characterized in that: The multiple pressure cylinder turbines connected in series in the steam power generation system include a high-pressure cylinder turbine, a medium-pressure cylinder turbine and a low-pressure cylinder turbine. The high-pressure cylinder turbine is connected to a coal-fired boiler, the low-pressure cylinder turbine is connected to a generator, and the low-pressure cylinder turbine is connected to a garbage drying and separation mechanism.

5. The refuse-derived fuel blending system for peak load shaving of large coal-fired boilers according to claim 1 is characterized in that: The garbage drying and separation mechanism includes a dryer, a wind separator, a garbage crusher and an extruder. The steam outlet of the low-pressure cylinder turbine is connected to the steam inlet of the dryer, the dryer is connected to the wind separator, the wind separator is connected to the garbage crusher and the extruder, the end of the garbage crusher away from the wind separator is connected to the gasifier, and the end of the extruder away from the wind separator supplies material to the coal-fired boiler.

6. A process for the co-combustion of refuse-derived fuels in a refuse-derived fuel co-combustion system for peak shaving of large coal-fired boilers according to any one of claims 1 to 5, characterized in that: When electricity consumption is low or the grid supply exceeds demand, perform the following steps: Step 1: The boiler output is reduced to below 30%, and the excess electricity from the power grid is used to power the wind power sorter, garbage crusher, extruder, and pellet fuel crusher; In step 2, the low-calorific value waste separated by the waste drying and separation mechanism is crushed to a particle size of less than 50 microns and then fed into the gasifier. The high-calorific value waste separated by the waste drying and separation mechanism is compressed into pelletized fuel and crushed before being fed into the coal-fired boiler for combustion support. Step 3: High-temperature flue gas at 800-900°C is drawn from the coal-fired boiler and fed into the gasifier to gasify the low-calorific value garbage. The gasifier generates a gas-liquid mixed gas at 600-700°C and outputs it to the heat exchanger. Step 4: The gasified gas of the gas-liquid mixture is cooled to 50-90°C by a heat exchanger and separated into gas and fuel oil by a separator, and supplied to the coal-fired boiler for auxiliary combustion.

7. The refuse-derived fuel blending system for peak load shaving of large coal-fired boilers according to claim 1 is characterized in that: The air input into the heat exchanger by the blower exchanges heat with the gas-liquid mixed gas in countercurrent in the heat exchanger, and is heated to 400-500° C. and enters the coal-fired boiler as secondary air for auxiliary combustion.

8. The process for the co-firing of refuse-derived fuel for peak load regulation of large coal-fired boilers according to claim 7, characterized in that: When the boiler is operating normally at full load, the exhaust gas outlet is closed and all the boiler flue gas is used to heat the feed water to generate steam, which drives the steam turbine to generate electricity through the steam power generation system.

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