Biomass circulating fluidized bed gasification coupling coal-fired unit power generation system and method

Abstract

The invention relates to the technical field of biomass energy utilization, in particular to a biomass circulating fluidized bed gasification coupling coal-fired unit power generation system and method.The system comprises a circulating fluidized bed gasification furnace, a cyclone separator, a cyclone dust collector and a fuel gas cooler which are sequentially connected through pipelines; the bottom of the circulating fluidized bed gasifier is connected with a gasification fan through a pipeline, an outlet of the gas cooler is connected to an inlet of the pulverized coal boiler through a hot gas fan, and an outlet of the pulverized coal boiler is connected with a chimney through an induced draft fan. Biomass is adopted as a raw material, the problem of open-air incineration of rural waste is solved, the environment is improved, the biomass replaces part of fire coal for power generation, the emission load of CO2, SOX, NOX and smoke dust is reduced, the operation cost in the desulfurization process of a power station boiler is reduced, and the positive effect on energy conservation and emission reduction is achieved; no wastewater is produced; biomass ash obtained after dust removal can be recycled as an organic fertilizer.

Description

Technical Field

[0001] The invention relates to the technical field of biomass energy utilization, and in particular to a system and method for biomass circulating fluidized bed gasification coupled with coal-fired unit power generation. Background Art

[0002] At present, the implementation paths of the energy industry mainly include vigorously promoting the development of clean energy, vigorously promoting the development of energy efficiency, vigorously promoting the substitution of electricity on the energy consumption side, and vigorously promoting natural carbon sinks and carbon capture. Biomass energy is one of the most widely used renewable energy sources in the world and the only recyclable and renewable carbon source. The use of biomass resources such as crop straw, agricultural product processing residues, and forestry residues can directly replace coal fossil energy and achieve zero carbon emissions. Therefore, fully exploring biomass to replace traditional energy is a key measure.

[0003] At present, the domestic biomass-coal coupled power generation technology generally adopts direct coupled power generation. Direct coupling is a technology that processes biomass to a state where it can be mixed with raw coal and then burns it directly in the furnace. Generally, direct-fired coupled power plants have large investments, and power generation efficiency is less than 30%. In addition, the consumption of biomass is huge, and its economic benefits are very unstable. With the improvement of environmental protection requirements, its investment recovery will become more difficult. Summary of the invention

[0004] The object of the present invention is to provide a system and method for biomass circulating fluidized bed gasification coupled with coal-fired unit power generation, which can solve the above technical problems.

[0005] The present invention provides a biomass circulating fluidized bed gasification coupled coal-fired unit power generation system, comprising a circulating fluidized bed gasifier, a cyclone separator, a cyclone dust collector and a gas cooler which are sequentially connected through pipelines, wherein the bottom of the circulating fluidized bed gasifier is connected to a gasification fan through a pipeline, the outlet of the gas cooler is connected to the inlet of a pulverized coal boiler through a hot coal gas fan, and the outlet of the pulverized coal boiler is connected to a chimney through an induced draft fan.

[0006] Preferably, the outlet of the cyclone separator is connected to a recycler, the bottom of the recycler is connected to a fluidizing fan through a pipeline, the discharge port of the recycler is connected to the lower end of the circulating fluidized bed gasifier, and the outlet of the cyclone dust collector is connected to an ash bin.

[0007] Preferably, the gas cooler adopts a gas-thermal oil heat exchanger, and the gas-thermal oil heat exchanger cools the thermal oil through an oil-water heat exchanger.

[0008] Preferably, the cooling water in the oil-water heat exchanger comes from condensate from a power plant, and the cooling water return water is connected to the deaerator of the original unit.

[0009] Preferably, a gasifier front silo is provided on one side of the circulating fluidized bed gasifier, and the biomass is fed into the circulating fluidized bed gasifier through a screw feeder.

[0010] Preferably, a biomass silo is provided on one side of the gasifier furnace front silo, which is connected to the gasifier furnace front silo through a belt conveyor.

[0011] Preferably, a steam inlet is provided on the recycler. The injection of steam can reduce the temperature of the circulating ash and avoid over-temperature slagging inside the recycler. The injected steam will react with the biochar in the recycler to produce combustible gas, further improving the gasification efficiency.

[0012] The present invention also provides a method for power generation by coupling biomass circulating fluidized bed gasification with a coal-fired unit based on the above system, comprising the following steps:

[0013] Step 1: The biomass raw materials are cut and sent into a circulating fluidized bed gasifier. The gasification medium is air, and the gasification air is sent into the circulating fluidized bed gasifier by a gasification fan;

[0014] Step 2: The gas is generated in the circulating fluidized bed gasifier, passes through a cyclone separator, and the separated ash is sent back to the lower part of the circulating fluidized bed gasifier through a return device to continue to participate in the reaction;

[0015] Step 3: The gas passes through the cyclone dust collector, and the separated ash is sent to the ash bin, which is then transported out by tank truck;

[0016] Step 4: The gas at the outlet of the cyclone dust collector is cooled by a gas cooler and then sent to the pulverized coal boiler through a hot gas fan for combustion and power generation.

[0017] Preferably, the particle size of the biomass raw material is less than 10 mm and the water content is no more than 30%.

[0018] Preferably, the temperature of the gas generated in step 2 is 700°C, the temperature of the gas at the outlet of the cyclone dust collector in step 4 is 680°C, and the temperature of the gas after cooling by the gas cooler is 400-450°C. This can not only cool the gas, but also meet the technical requirements of equipment such as pipelines and valves, and also avoid tar precipitation caused by excessive cooling of biomass gas.

[0019] Beneficial effects:

[0020] The present invention uses biomass as raw material, which solves the problem of open-air burning of rural waste, improves the environment, and also brings economic benefits to farmers; biomass replaces part of coal-fired power generation, reducing CO2, SO X 、NO XIt reduces the emission of dust and smoke, reduces the operating cost of the desulfurization process of power station boilers, and plays a positive role in energy conservation and emission reduction; no wastewater is produced; the biomass ash obtained after dust removal can be recycled as organic fertilizer; gas cooling solves the problem of tar deposition pollution; biomass combustible gas is easier to burn than coal, and a large proportion of blending can be achieved, and the operation adjustment is flexible, which can adapt to the wide range of coal-fired units. It belongs to indirect coupling technology, which can effectively reduce costs and improve the efficiency of bioenergy power generation with the help of the high efficiency of coal-fired units. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 It is a schematic diagram of the overall structure of the system of the present invention.

[0023] Explanation of the accompanying drawings: 1-circulating fluidized bed gasifier, 101-biomass silo, 102-gasifier front silo, 201-cyclone separator, 202-cyclone dust collector, 301-gas-oil heat exchanger, 302-oil-water heat exchanger, 401-gasification fan, 402-fluidizing fan, 5-hot gas fan, 6-pulverized coal boiler, 7-induced draft fan, 8-chimney, 9-returner, 901-steam inlet, 10-ash silo, 11-deaerator, 12-steam turbine, 13-condenser, 14-water pump. DETAILED DESCRIPTION

[0024] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than 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.

[0025] 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" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0026] In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined. In addition, the terms "installed", "connected" and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0027] Example 1

[0028] A biomass circulating fluidized bed gasification coupled with a coal-fired unit power generation system, such as Figure 1 As shown, it includes a circulating fluidized bed gasifier 1, a cyclone separator 201, a cyclone dust collector 202 and a gas cooler connected in sequence through pipelines. A gasifier furnace front silo 102 is provided on one side of the circulating fluidized bed gasifier 1. Biomass is fed into the circulating fluidized bed gasifier 1 through a screw feeder. A biomass silo 101 is provided on one side of the gasifier furnace front silo 102, which is connected to the gasifier furnace front silo 102 through a belt conveyor. The bottom of the circulating fluidized bed gasifier 1 is connected to a gasification fan 401 through a pipeline, the outlet of the gas cooler is connected to the inlet of the pulverized coal boiler 6 through a hot coal gas fan 5, and the outlet of the pulverized coal boiler 6 is connected to a chimney 8 through an induced draft fan 7.

[0029] Specifically, the outlet of the cyclone separator 201 is connected to a recycler 9, the discharge port of the recycler 9 is connected to the lower end of the circulating fluidized bed gasifier 1, the bottom of the recycler 9 is connected to a fluidizing fan 402 through a pipeline, and the recycler 9 is provided with a steam inlet 901. The injection of steam can reduce the temperature of the circulating ash and avoid overheating and slagging inside the recycler 9. The injected steam will react with the biomass charcoal in the recycler 9 to produce combustible gas, further improving the gasification efficiency. The outlet of the cyclone dust collector 202 is connected to an ash bin 10, and a tank truck is used below the ash bin 10 to transport the ash for sale.

[0030] The gas cooler adopts a gas-thermal oil heat exchanger 301, which cools the thermal oil through an oil-water heat exchanger 302. The cooling water in the oil-water heat exchanger 302 comes from the condensate of the power plant, and the cooling water return is connected to the deaerator 11 of the original unit.

[0031] A method for generating electricity by coupling biomass circulating fluidized bed gasification with coal-fired units based on the above system, using air as a gasifying agent, utilizing biomass raw materials (straw, husks, waste wood, etc.) to be gasified in a circulating fluidized bed gasifier, and the generated low calorific value gas (mainly composed of CO, CH4, H2, etc.) is used as boiler fuel, which is sent into the boiler furnace to be mixed with coal for combustion, and the generated steam is used for power generation. The specific process steps include:

[0032] 1) The biomass raw materials are cut into particles with a diameter and length of less than 10 mm, and the moisture content is not more than 30% (if it is more than 30%, it needs to be dried to 30%);

[0033] 2) The biomass is sent to the gasifier silo via a belt conveyor, and then sent to the circulating fluidized bed gasifier via a screw feeder. The gasification medium is air, and the gasification air is sent to the circulating fluidized bed gasifier by a gasification fan;

[0034] 3) In order to maintain the material balance in the circulating fluidized bed gasifier, an existing bed material replenishment system is installed on the side of the circulating fluidized bed gasifier to replenish the bed material at any time as needed to keep the bed pressure of the circulating fluidized bed gasifier stable;

[0035] 4) The 700℃ fuel gas produced in the circulating fluidized bed gasifier has a calorific value of 4200-4300kJ / Nm 3 , after passing through the cyclone separator, the separated ash is sent back to the lower part of the circulating fluidized bed gasifier through the return device to continue to participate in the reaction;

[0036] 5) The gas then passes through the cyclone dust collector, and the separated ash is cooled by the ash cooler, and the ash temperature drops to 60-80℃. The cooling water comes from the condensate of the original power plant. The cooled ash is sent to the ash bin by the pneumatic conveying system, and then transported to the ash bin by tank trucks for sale;

[0037] 6) The gas temperature at the outlet of the cyclone dust collector is about 680℃, which is cooled by the gas-thermal oil heat exchanger to 400-450℃. In the gas-thermal oil heat exchanger system, the thermal oil heated by the gas transfers the heat to the condensate of the power plant;

[0038] 7) The 400-450℃ outlet gas is sent to the pulverized coal boiler through the hot gas fan (boosting fan), and then enters the coal-fired unit coupled power generation boiler for combustion;

[0039] The above biomass raw materials are a mixture of rice straw, wheat straw, forestry waste, etc. The industrial analysis of the mixed material is as follows: moisture 21.8%, ash 8.38%, volatile matter 56.83%, fixed carbon 12.99%, elemental composition hydrogen 5.22%, carbon 35.02%, sulfur 0.095%, nitrogen 0.385%, oxygen 29.09%, and lower calorific value is 13624KJ / Kg. The above mixed data is calculated based on 25% rice straw, 25% wheat straw, and 50% forestry waste.

[0040] For single-unit 10MW and large-scale circulating fluidized bed gasifiers above 10MW, the feeding system adopts two-stage feeding in front of the furnace. The fuel enters in two ways and operates independently. There are silos in front of the furnace. Each silo is equipped with more than 3 disturbance devices. There are two-stage feeders at the bottom of the silo. The first stage is a double screw feeder and the second stage is a screw feeder. Each feeder is 150% of the maximum continuous feeding amount of the gasifier; the gasification fan and fluidization fan are Roots blowers. The dust concentration of flue gas at the outlet of the cyclone dust collector is ≤15g / Nm 3 The outlet gas passes through the gas cooler and is pressurized by the booster fan, and is transported to the coal-fired power plant boiler through the gas pipeline; the gasifier is equipped with a bed material replenishment system to control the bed pressure. The bed material feeding port is located in the middle of the gasifier. The bed material is sent into the silo through the scraper bucket elevator, and then the gasifier is replenished through the spiral feeder at the bottom of the silo; the high-temperature gas is sent to the large coal-fired unit boiler and connected in the same combustion mode as the original boiler. The design and operation do not affect the normal operation of the large boiler; the high-temperature combustible gas at the outlet of the gasifier adopts gas -Thermal oil heat exchanger cooling, the gas-thermal oil heat exchanger and the oil-water heat exchanger form a cooling system. The cooling water uses the condensate produced by the turbine 12 of the original coal-fired unit through the condenser 13, and is equipped with a water pump 14 to meet the return water requirements. The cooling water return is connected to the deaerator of the original unit; the lower part of the cyclone dust collector is provided with an ash outlet. The high-temperature ash of 700-750℃ is cooled to 60-80℃ by a water-cooled heat exchanger and then discharged to the dry ash silo by pneumatic conveying. The middle silo in front of the silo pump meets the 3-hour inventory requirement. The dry ash silo is made of steel.

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A biomass circulating fluidized bed gasification coupled with a coal-fired unit power generation system, characterized in that: The invention comprises a circulating fluidized bed gasifier, a cyclone separator, a cyclone dust collector and a gas cooler which are sequentially connected through pipelines. The bottom of the circulating fluidized bed gasifier is connected to a gasification fan through a pipeline. The outlet of the gas cooler is connected to the inlet of a pulverized coal boiler through a hot gas fan. The outlet of the pulverized coal boiler is connected to a chimney through an induced draft fan.

2. The system for biomass circulating fluidized bed gasification coupled with coal-fired unit power generation according to claim 1, characterized in that: The outlet of the cyclone separator is connected to a recycler, the bottom of the recycler is connected to a fluidizing fan through a pipeline, the discharge port of the recycler is connected to the lower end of the circulating fluidized bed gasifier, and the outlet of the cyclone dust collector is connected to an ash bin.

3. The biomass circulating fluidized bed gasification coupled coal-fired unit power generation system according to claim 1, characterized in that: The gas cooler adopts a gas-thermal oil heat exchanger, and the gas-thermal oil heat exchanger cools the thermal oil through an oil-water heat exchanger.

4. The biomass circulating fluidized bed gasification coupled coal-fired unit power generation system according to claim 3 is characterized in that: The cooling water in the oil-water heat exchanger comes from the condensate of the power plant, and the cooling water return water is connected to the deaerator of the original unit.

5. The biomass circulating fluidized bed gasification coupled coal-fired unit power generation system according to claim 1, characterized in that: A gasifier front silo is provided on one side of the circulating fluidized bed gasifier, and biomass is fed into the circulating fluidized bed gasifier through a screw feeder.

6. The system for biomass circulating fluidized bed gasification coupled with coal-fired unit power generation according to claim 5, characterized in that: A biomass silo is provided on one side of the gasifier furnace front silo and is connected to the gasifier furnace front silo through a belt conveyor.

7. The biomass circulating fluidized bed gasification coupled coal-fired unit power generation system according to claim 2, characterized in that: The material return device is provided with a steam inlet.

8. A method for power generation by coupling biomass circulating fluidized bed gasification with coal-fired units based on the system of claim 2, characterized in that: The following steps are involved: Step 1: The biomass raw materials are cut and sent into a circulating fluidized bed gasifier. The gasification medium is air, and the gasification air is sent into the circulating fluidized bed gasifier by a gasification fan; Step 2: The gas is generated in the circulating fluidized bed gasifier, passes through a cyclone separator, and the separated ash is sent back to the lower part of the circulating fluidized bed gasifier through a return device to continue to participate in the reaction; Step 3: The gas passes through the cyclone dust collector, and the separated ash is sent to the ash bin, which is then transported out by tank truck; Step 4: The gas at the outlet of the cyclone dust collector is cooled by a gas cooler and then sent to the pulverized coal boiler through a hot gas fan for combustion and power generation.

9. The method according to claim 8, characterized in that The particle size of the biomass raw material is less than 10 mm, and the water content is not more than 30%.

10. The method according to claim 8, characterized in that The temperature of the gas generated in step 2 is 700°C, the temperature of the gas at the outlet of the cyclone dust collector in step 4 is 680°C, and the temperature of the gas after cooling by the gas cooler is 400-450°C.

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