CN117005921A - Low-temperature heat power cogeneration system driven by flue gas waste heat - Google Patents

Abstract

In order to solve the problems of limited flue gas waste heat utilization and insufficient heating capacity of coal-fired combined heat and power units, the present invention digs deep into its energy-saving space and discloses a low-temperature cogeneration system driven by flue gas waste heat. A negative pressure flash evaporation flue gas waste heat utilization method is proposed to cool down the saturated wet flue gas at the outlet of the desulfurization tower, so that the water vapor condenses and releases latent heat to indirectly recover the flue gas waste heat. Utilize R22 or other organic working fluids to evaporate into superheated steam under low pressure conditions, and then drive the turbine to generate power. A new waste heat utilization and conversion method is developed. At the same time, the circulating water of the heating network recovers the exhaust steam waste heat at the outlet of the turbine to achieve low-temperature heat and power integration. Production, adding a throttling bypass and an electric boiler improves the flexibility of system heat-to-power ratio adjustment, meets users' needs for wide load changes, and achieves an energy-saving, low-carbon, efficient and flexible waste heat recovery method.

Description

A low-temperature cogeneration system driven by flue gas waste heat

Technical field

The invention belongs to the technical field of clean energy, and in particular relates to a low-temperature cogeneration system driven by flue gas waste heat.

Background technique

With the accelerated development of urbanization in our country, the built-up area of urban residents is increasing year by year. On the other hand, in the process of advancing the dual carbon goals, various regions have gradually closed down some small combined heat and power units and coal-fired boilers to reduce the share of coal consumption. The energy structure has shifted from coal to clean energy, resulting in some growth and the original residential heating area. The heat load does not guarantee the heat source. Combined heat and power plays a vital role in ensuring clean heating in northern urban areas. It is also an important measure to achieve the dual carbon goal. We should further tap the power generation and heating potential of existing large-scale combined heat and power units and give full play to their efficient energy saving and reduction. Discharge advantage is an important technical research direction in the energy industry at this stage.

The waste heat utilization of large-scale combined heat and power units is mainly divided into two parts: flue gas waste heat utilization and cold end waste heat utilization. At this stage, cold end waste heat utilization is relatively mature, with high back pressure, heat pump, cylinder cutting and other transformation technologies, while flue gas waste heat utilization is relatively mature. There is still room for energy-saving potential utilization. The flue gas at the outlet of the desulfurization tower is basically saturated wet flue gas, which contains a large amount of latent heat of low-temperature water vapor. Due to the low temperature, direct heat exchange cannot be performed. At the same time, it contains many corrosive components, and direct extraction is limited. . How to recycle and utilize the considerable low-temperature waste heat in the flue gas at the end of the boiler is the core key technology to improve the energy utilization rate of cogeneration units and reduce carbon emissions.

Contents of the invention

The present invention solves the problems of limited flue gas waste heat utilization and insufficient heating capacity of coal-fired combined heat and power units, and deeply explores its energy-saving space. The first purpose of the invention is to establish a low-temperature cogeneration system driven by flue gas waste heat;

The second object of the present invention is to propose a negative pressure flash evaporation flue gas waste heat utilization method to cool down the saturated wet flue gas at the outlet of the desulfurization tower, so that the water vapor condenses and releases latent heat to indirectly recover the flue gas waste heat. Utilize R22 or other organic working fluids to evaporate into superheated steam under low pressure conditions, and then drive the turbine to generate power;

The third purpose of the present invention is to develop a new waste heat utilization and conversion method. At the same time, the circulating water of the heating network recovers the exhaust steam waste heat at the turbine outlet to realize low-temperature cogeneration of heat and power. Adding a throttling bypass and an electric boiler improves the flexibility of system heat-to-power ratio adjustment to satisfy users. Wide load change requirements enable energy-saving, low-carbon, efficient and flexible waste heat recovery methods.

The present invention adopts the following technical solution: a low-temperature cogeneration system driven by flue gas waste heat, including a flue gas waste heat recovery system, a waste heat power generation loop, a throttling bypass, and a heating network user loop;

The flue gas waste heat recovery system consists of a slurry spray pump, a spray nozzle, a negative pressure flash evaporation tower, a vacuum pump, a slurry dewatering pump, a condensate water pump, a return valve, a condensate water valve, and a condensate water tank; it is installed on the outlet side of the desulfurization tower. Negative pressure flash evaporation tower. The bottom of the negative pressure flash evaporation tower is equipped with a slurry water withdrawal pump. The side of the tower is equipped with a return valve. The top of the tower is connected to the evaporator pipeline. The negative pressure flash evaporation tower, evaporator, condensate water pump, return water pump, etc. The water valves are connected in series to form a loop; the return valve, condensate valve and condensate tank are connected in series through pipelines;

The waste heat power generation loop consists of an evaporator, turbine, condenser, solution tank, and working medium boost pump connected in series to form a loop. The turbine provides power to the generator, which in turn supplies power to the user and also provides power to the electric boiler;

The throttling bypass consists of a first ball valve, an electric throttle valve, a check valve, and a second ball valve connected in series through pipelines. One end of the first ball valve is connected to the pipeline between the evaporator and the turbine, and one end of the second ball valve is connected to the turbine. on the pipeline between the condenser and the condenser;

The heating network user loop consists of a condenser, a heating network circulating water pump, and an electric boiler. An electric boiler is installed at the condenser outlet.

Further, a spray nozzle is provided in the negative pressure flash evaporation tower, and a vacuum pump is provided on the negative pressure flash evaporation tower.

Further, when the system is running, the slurry spray pump sends the desulfurization slurry in the desulfurization tower to the spray nozzle in the negative pressure flash evaporation tower for spraying. The vacuum pump is used to create a vacuum environment in the tower to maintain the negative pressure in the tower, so that The desulfurization slurry flashes in the tower to form low-pressure water vapor. The cooled slurry after flashing is sent back to the desulfurization tower by the slurry return pump to continue spraying the flue gas. The low-temperature water vapor formed enters the evaporator and transfers heat to the circulating working fluid. R22, the condensate water is sent back to the flash tower through the condensate water pump. The recovered water can be sent back to the desulfurization tower for water replenishment, or it can be collected into the condensate water tank for other uses; at this time, the return valve is open and the condensate water valve is closed. , if the liquid level in the negative pressure flash evaporation tower is too high, close the return water valve, open the condensation water valve, and send the condensation water into the condensation water tank; after the circulating working fluid R22 absorbs waste heat in the evaporator and evaporates into superheated steam, It enters the turbine and expands to do work to drive the generator to generate electricity. The exhaust steam from the outlet enters the condenser to heat the hot network return water. The condensed working fluid enters the solution tank, and is then boosted by the working fluid booster pump and sent to the evaporator to complete the main cycle.

Furthermore, when it is necessary to increase the heat-to-power ratio of the system, the first ball valve and the second ball valve are opened, so that part of the main loop working fluid enters the throttling bypass and is depressurized and directly sent to the condenser to participate in heating; if the user's heat and electricity are used at this time When the load demand is too large and cannot be met even by adjusting the throttling bypass, the electric boiler is started, and the generator's power is consumed for heating to supplement the heat vacancy. The system's thermoelectric output power ratio is adjusted to respond to the user's load demand; the return water from the heating network is circulated through the heating network. After the water pump boosts the pressure, it flows through the condenser and the electric boiler in sequence, and reaches the water supply temperature requirement and is sent to the heat user.

Compared with the existing technology, the present invention has the following advantages:

(1) Based on the principle of negative pressure flash evaporation, the latent heat of water vapor contained in the flue gas is recovered to avoid corrosion and blockage of equipment by impurities in the flue gas, reducing the operation, maintenance and investment costs of waste heat recovery. In the process, some condensation with good water quality can also be recovered Water can be used to replenish the desulfurization tower or for other purposes, reducing water consumption in the entire plant;

(2) Use R22 working fluid to establish a low-temperature power generation loop, so that the recovered waste heat can be converted into higher-grade, more versatile electrical energy for factory power or other purposes, reducing the power consumption of the entire plant;

(3) The throttling bypass cooperates with the electric boiler to adjust the system heat and power ratio within a wide range. Under the real-time and changing heat and power load demands on the user side, it can quickly and flexibly meet the user load and meet the three-modification linkage conditions.

Description of the drawings

Figure 1 is a schematic structural diagram of a low-temperature cogeneration system driven by flue gas waste heat.

Explanation of reference numbers: slurry spray pump 1, spray nozzle 2, negative pressure flash evaporation tower 3, vacuum pump 4, slurry water withdrawal pump 5, condensate water pump 6, water return valve 7, condensate water valve 8, condensate water tank 9, Evaporator 10, turbine 11, generator 12, condenser 13, solution tank 14, working medium boost pump 15, first ball valve 16, electric throttle valve 17, check valve 18, second ball valve 19, heating network cycle Water pump 20, electric boiler 21.

Detailed ways

As shown in Figure 1, a low-temperature cogeneration system driven by flue gas waste heat includes a flue gas waste heat recovery system, a waste heat power generation loop, a throttling bypass, and a heating network user loop;

The flue gas waste heat recovery system consists of slurry spray pump 1, spray nozzle 2, negative pressure flash evaporation tower 3, vacuum pump 4, slurry dewatering pump 5, condensate pump 6, return valve 7, condensate valve 8, condensate tank 9; the waste heat power generation loop is composed of an evaporator 10, a turbine 11, a generator 12, a condenser 13, a solution tank 14, and a working medium boost pump 15; the throttling bypass is composed of a first ball valve 16, an electric throttle valve 17, and a check valve. It consists of a return valve 18 and a second ball valve 19; the heating network user loop is composed of a heating network circulating water pump 20 and an electric boiler 21.

A negative pressure flash evaporation tower 3 is installed on the outlet side of the desulfurization tower. When the low-temperature cogeneration system driven by flue gas waste heat is running, the desulfurization slurry in the desulfurization tower is sent to the spray in the negative pressure flash evaporation tower 3 by the slurry spray pump 1 Spray in the nozzle 2, use the vacuum pump 4 to create a vacuum environment in the tower, maintain the negative pressure in the tower, and flash the desulfurization slurry to form low-pressure water vapor in the tower. The cooled slurry after flashing is sent back to the desulfurization tower by the slurry return pump 5. The internal flue gas continues to be sprayed, and the low-temperature water vapor formed enters the evaporator 10 and transfers heat to the circulating working fluid R22. The condensed water is sent back to the flash evaporation tower 3 through the condensed water pump 6. This part of the recovered water can be sent back The desulfurization tower is used for water replenishment, and can also be collected into the condensate water tank 9 for other uses; at this time, the return water valve 7 is opened and the condensate water valve 8 is closed. If the liquid level in the negative pressure flash evaporation tower 3 is too high, the return water valve 7 is closed. , open the condensate valve 8, and send the condensate water into the condensate tank 9; after the circulating working fluid R22 absorbs waste heat in the evaporator 10 and evaporates into superheated steam, it enters the turbine 11 to expand and perform work to drive the generator 12 to generate electricity, and the exhaust steam is exported The water returns to the heating network in the condenser 13, and the condensed working fluid enters the solution tank 14, and is then boosted by the working fluid booster pump 15 and sent to the evaporator 10 to complete the main cycle.

The throttling bypass consists of a first ball valve 16, an electric throttle valve 17, a check valve 18, and a second ball valve 19. When it is necessary to increase the heat-power ratio of the system, the first ball valve 16 and the second ball valve 19 are opened to allow part of the main loop to The working fluid enters the throttling bypass and is depressurized and directly sent to the condenser 13 to participate in heating; if the user's thermal and electrical load demand is too large at this time and cannot be met by adjusting the throttling bypass, the electric boiler 21 is started and the generator 12 is consumed. The power generated for heating supplements the heat vacancy, adjusts the proportion of the system's thermoelectric output power, and responds to user load demands; the return water from the heating network is boosted by the heating network circulating water pump 20 and flows through the condenser 13 and the electric boiler 21 in sequence until it reaches the water supply temperature requirement and is sent Top users.

Through the above system, low-temperature flue gas waste heat can be efficiently recycled and converted into electricity and heat. It also has high flexibility, reduces the power supply and heating costs of the entire plant and pollutant emissions, and optimizes operating indicators.

The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed in the present invention will be considered. should be covered by the protection scope of the present invention.

Claims (4)

1. A low-temperature cogeneration system driven by flue gas waste heat, including a flue gas waste heat recovery system, a waste heat power generation loop, a throttling bypass, and a heating network user loop; The flue gas waste heat recovery system consists of a slurry spray pump (1), a spray nozzle (2), a negative pressure flash evaporation tower (3), a vacuum pump (4), a slurry water withdrawal pump (5), a condensate water pump (6), a return It consists of a water valve (7), a condensate valve (8), and a condensate tank (9); a negative pressure flash evaporation tower (3) is installed on the outlet side of the desulfurization tower, and a slurry evaporator is provided at the bottom of the negative pressure flash evaporation tower (3). Water pump (5), a return valve (7) is provided on the side of the tower, and the top of the tower is connected to the evaporator (10) pipeline, including the negative pressure flash evaporation tower (3), evaporator (10), condensate pump (6), The return water valve (7) is connected in series with pipelines to form a loop; the return water valve (7), the condensate water valve (8) and the condensate water tank (9) are connected in series through pipelines; The waste heat power generation loop consists of an evaporator (10), a turbine (11), a condenser (13), a solution tank (14), and a working medium boost pump (15) connected in series through pipelines to form a loop. The turbine (11) is a generator. (12) provides power, and the generator (12) supplies power to the user and also provides power to the electric boiler (21); The throttling bypass consists of a first ball valve (16), an electric throttle valve (17), a check valve (18), and a second ball valve (19) connected in series through pipelines. One end of the first ball valve (16) is connected to the evaporator. On the pipeline between the turbine (10) and the turbine (11), one end of the second ball valve (19) is connected on the pipeline between the turbine (11) and the condenser (13); The heating network user loop is composed of a condenser (13), a heating network circulating water pump (20), and an electric boiler (21) piped in series. An electric boiler (21) is installed at the outlet of the condenser (13). 2. The low-temperature cogeneration system driven by flue gas waste heat as claimed in claim 1, characterized in that the negative pressure flash evaporation tower (3) is equipped with a spray nozzle (2), and the negative pressure flash evaporation tower (3) A vacuum pump (4) is provided on it. 3. The low-temperature cogeneration system driven by flue gas waste heat as claimed in claim 2, characterized in that when the system is running, the desulfurization slurry in the desulfurization tower is sent to the negative pressure flash evaporation tower (1) by the slurry spray pump (1). 3) Spray in the spray nozzle (2), use the vacuum pump (4) to create a vacuum environment in the tower, maintain the negative pressure in the tower, so that the desulfurization slurry flashes in the tower to form low-pressure water vapor, and the temperature is cooled after flashing The slurry is sent back to the desulfurization tower by the slurry return pump (5) to continue spraying the flue gas. The low-temperature water vapor formed enters the evaporator (10) and transfers heat to the circulating working medium R22. The condensed water is sent through the condensate pump (6). In the flashback tower (3), the recovered water can be sent back to the desulfurization tower for water replenishment, or it can be collected into the condensate tank (9) for other uses; at this time, the return valve (7) is opened, and the condensate valve (8) is closed. If the liquid level in the negative pressure flash evaporation tower (3) is too high, close the return valve (7), open the condensate valve (8), and send the condensate water into the condensate tank (9); After the circulating working fluid R22 absorbs waste heat in the evaporator (10) and evaporates into superheated steam, it enters the turbine (11) to expand and perform work to drive the generator (12) to generate electricity. The outlet exhaust steam enters the condenser (13) to heat the return water of the heating network. , the condensed working fluid enters the solution tank (14), and is then boosted by the working fluid booster pump (15) and sent to the evaporator (10) to complete the main cycle. 4. The low-temperature cogeneration system driven by flue gas waste heat as claimed in claim 3, characterized in that when it is necessary to increase the system heat to electricity ratio, the first ball valve (16) and the second ball valve (19) are opened to partially The working fluid in the main loop enters the throttling bypass and is decompressed and directly sent to the condenser (13) to participate in heating; if the user's thermal and electrical load demand is too large at this time and cannot be met by adjusting the throttling bypass, the electric boiler (21 ), consume the power generated by the generator (12) for heating to supplement heat vacancies, adjust the system thermoelectric output power ratio, and respond to user load demands; the return water from the heating network is boosted by the heating network circulating water pump (20) and then flows through the condenser (13) in turn ) and the electric boiler (21), the water supply temperature requirements are met and sent to the heat user.