CN111577409A - Recovery system for recovering exhaust steam of steam turbine by adopting cascade utilization and supercharging upgrading technology - Google Patents
Recovery system for recovering exhaust steam of steam turbine by adopting cascade utilization and supercharging upgrading technology Download PDFInfo
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- 239000007789 gas Substances 0.000 description 5
- 239000002918 waste heat Substances 0.000 description 5
- 239000002826 coolant Substances 0.000 description 4
- 239000000498 cooling water Substances 0.000 description 4
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
- F01K17/00—Using steam or condensate extracted or exhausted from steam engine plant
- F01K17/02—Using steam or condensate extracted or exhausted from steam engine plant for heating purposes, e.g. industrial, domestic
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
- F01D15/00—Adaptations of machines or engines for special use; Combinations of engines with devices driven thereby
- F01D15/08—Adaptations for driving, or combinations with, pumps
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
- F01K19/00—Regenerating or otherwise treating steam exhausted from steam engine plant
- F01K19/02—Regenerating by compression
- F01K19/04—Regenerating by compression in combination with cooling or heating
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
- F01K7/00—Steam engine plants characterised by the use of specific types of engine; Plants or engines characterised by their use of special steam systems, cycles or processes; Control means specially adapted for such systems, cycles or processes; Use of withdrawn or exhaust steam for feed-water heating
- F01K7/02—Steam engine plants characterised by the use of specific types of engine; Plants or engines characterised by their use of special steam systems, cycles or processes; Control means specially adapted for such systems, cycles or processes; Use of withdrawn or exhaust steam for feed-water heating the engines being of multiple-expansion type
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
- F01K7/00—Steam engine plants characterised by the use of specific types of engine; Plants or engines characterised by their use of special steam systems, cycles or processes; Control means specially adapted for such systems, cycles or processes; Use of withdrawn or exhaust steam for feed-water heating
- F01K7/16—Steam engine plants characterised by the use of specific types of engine; Plants or engines characterised by their use of special steam systems, cycles or processes; Control means specially adapted for such systems, cycles or processes; Use of withdrawn or exhaust steam for feed-water heating the engines being only of turbine type
- F01K7/30—Steam engine plants characterised by the use of specific types of engine; Plants or engines characterised by their use of special steam systems, cycles or processes; Control means specially adapted for such systems, cycles or processes; Use of withdrawn or exhaust steam for feed-water heating the engines being only of turbine type the turbines using exhaust steam only
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24D—DOMESTIC- OR SPACE-HEATING SYSTEMS, e.g. CENTRAL HEATING SYSTEMS; DOMESTIC HOT-WATER SUPPLY SYSTEMS; ELEMENTS OR COMPONENTS THEREFOR
- F24D3/00—Hot-water central heating systems
- F24D3/10—Feed-line arrangements, e.g. providing for heat-accumulator tanks, expansion tanks ; Hydraulic components of a central heating system
- F24D3/1058—Feed-line arrangements, e.g. providing for heat-accumulator tanks, expansion tanks ; Hydraulic components of a central heating system disposition of pipes and pipe connections
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- General Engineering & Computer Science (AREA)
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Abstract
The invention provides a recovery system for recovering exhaust steam of a steam turbine by adopting a cascade utilization and supercharging upgrading technology, which is provided with two temperature rising units, wherein the first temperature rising unit comprises: the steam heating system comprises a steam compressor, a first heater and a second heater, wherein the steam compressor is used for boosting exhausted steam of a main steam turbine from a main steam turbine to a first pressure, and the first heater is used for carrying out first temperature rise on a heating object by utilizing the exhausted steam boosted by the steam compressor to enable the heating object to reach a first temperature; the vapor compressor is a centrifugal compressor having a plurality of compression stages. The second warming unit includes: and the dragging steam turbine drives steam with high quality to provide kinetic energy, the dragging compressor rotates, exhaust steam of the dragging steam turbine enters the second heater, and the heating object is subjected to second temperature rise to reach a second temperature. The system reduces the cold source loss of the steam turbine unit, improves the unit operation economy, has high operation adjustment flexibility, can effectively improve the exhaust steam utilization rate, and has COP (coefficient of performance) as high as more than 2.2.
Description
Technical Field
The invention relates to a recovery system for exhaust steam of a steam turbine, in particular to a recovery system for recovering the exhaust steam of the steam turbine by adopting a cascade utilization and pressurization upgrading technology.
Background
In addition to the use of steam turbines for power, the remaining heat can also be used as a source of energy, in particular for heating purposes. For example, in a power plant, a Combined Heat and Power (CHP) unit generates and supplies both power and heat, so that the loss of a cold source can be effectively reduced, the energy utilization efficiency is remarkably improved, the total energy system principle of 'temperature to mouth and cascade utilization' is met, and the efficient way of improving the energy utilization efficiency and reducing the pollutant emission is provided. The comprehensive utilization efficiency of energy can be improved to more than 80% theoretically by adopting the coal-fired generator set adopting the cogeneration technology.
At present, the heat supply mode of the thermal power plant generally adopts the following three modes:
(1) steam extraction and heat supply of a steam turbine intermediate pressure cylinder: as shown in fig. 7, the heating mode is a heating mode conventionally adopted by a thermal power plant, and is mainly characterized in that the steam is exhausted by a medium pressure cylinder to extract steam for heating, the heating capacity is high, the cold source loss of a steam turbine is reduced, and the heating economical efficiency is better than that of an industrial heating boiler; the defects are that the exhaust steam extraction heat supply parameters of the intermediate pressure cylinder are high, and the degraded use of steam exists; the great temperature difference exists between the steam extraction temperature and the return water of the heat supply network, which causes great temperature differenceAnd (4) loss.
(2) High back pressure heat supply of the steam turbine: through the transformation of the low-pressure cylinder through-flow part and the cold end condenser of the steam turbine, the exhaust steam pressure and the exhaust steam temperature of the steam turbine are improved, and the exhaust steam of the steam turbine is utilized to heat the heat supply network water, so that the aims of recovering the waste heat of the exhaust steam and saving high-quality heat supply steam extraction of the steam turbine are fulfilled. The main characteristics are that the loss of the cold source of the unit is greatly reduced or eliminated, the heat supply economy is the best, and the circulation efficiency of the unit can reach nearly 100 percent. The disadvantages are as follows: the circulating water heating temperature is limited by the exhaust back pressure of a steam turbine, the heating temperature is low, and the circulating water heating temperature is matched with the steam extraction of the steam turbine for heating to form a step heating system; secondly, the coupling characteristic of the steam turbine body and the cold end system is complex, the generating peak regulation capacity of the unit with the characteristic of the heating grid system is weakened, and a mode of 'fixing power by heat' is generally adopted.
(3) A vapor driven absorption heat pump: the heat pump mode is adopted for heat supply, and partial low-temperature heat energy is converted into high-temperature heat energy at the cost of consuming partial high-quality energy by utilizing the physical characteristics of the circulating working medium in the heat pump, so that the recovery of the low-quality energy is realized. The method is characterized in that part of high-quality heat energy is consumed, part of low-quality heat source is recycled, and the heat supply economy is good. The heat pump system has the defects that the quality of a driving heat source provided by a steam turbine unit for a heat pump is higher, for example, a 300MW unit is adopted, the pressure is within the range of 0.5-0.8 MPa, the temperature is within the range of 290-330 ℃, the temperature of a water supply at the side of a common heat supply and heat supply network is generally about 100 ℃, and the high-quality driving heat source in the heat pump system has the condition of degraded use, so that the larger driving heat source is causedAnd (4) loss. The conversion ratio COP (coefficient Of performance) between the energy and the heat Of the current heat pump system can generally reach 1.6-1.7.
The air cooling cogeneration technology faces huge development opportunities and theoretical requirements due to the resource endowment and the central heating development requirements of 'rich coal and poor water' in the north of China. The air-cooled cogeneration unit relates to coupling of various cooling modes and cascade utilization of waste heat, and is an effective way for adapting to complex environmental conditions, meeting large-scale load concentrated emission, further reducing coal consumption of coal-fired power generation and reducing pollutant emission. The traditional intermediate steam extraction type heat supply unit still has larger steam extraction qualityLoss, the purpose of improving the steam exhaust of the unit for heat supply through a proper means is an important subject for improving the steam heating economy of the thermal power plant.
Disclosure of Invention
Aiming at the actual conditions of the existing thermal power plant and heating system, in order to further improve the heating economy, the problem of degradation of high-quality energy needs to be solved, and the dead steam of the steam turbine is effectively recycled.
The invention provides a recovery system for recovering exhaust steam of a steam turbine by adopting a cascade utilization and supercharging upgrading technology, which can effectively improve the utilization rate of the exhaust steam, reduce the cold source loss of a steam turbine unit, improve the operation economy of the unit and has the characteristic of high operation regulation flexibility.
The recovery system for recovering the exhaust steam of the steam turbine by adopting the cascade utilization and supercharging upgrading technology in one scheme of the invention comprises a first temperature-raising unit, wherein the first temperature-raising unit comprises: a steam compressor (1) for increasing the pressure of exhaust steam from a main turbine of a main turbine to a first pressure, and a first heater (4) for increasing the temperature of a heating target to a first temperature by the exhaust steam increased by the steam compressor; the vapor compressor (1) is a centrifugal compressor having a plurality of compression stages; the first warming unit further includes an intercooler (3) connected in parallel with the first heater (4), branching the heating target before the first warming into a part to intercool the main turbine exhaust steam between predetermined two compression stages among the plurality of compression stages, and the part of the heating target joining the heating target warmed to the first temperature by the first heater after the intercooling.
According to the recovery system for recovering the exhaust steam of the steam turbine by adopting the cascade utilization and supercharging upgrading technology, the utilization rate of the exhaust steam can be effectively improved, the cold source loss of a steam turbine unit is reduced, the running economy of the unit is improved, and the recovery system has the characteristic of high running and adjusting flexibility.
Drawings
The above and other features, advantages and aspects of various embodiments of the present disclosure will become more apparent by referring to the following detailed description when taken in conjunction with the accompanying drawings. Throughout the drawings, the same or similar reference numbers refer to the same or similar elements. It should be understood that the drawings are schematic and that elements and elements are not necessarily drawn to scale.
FIG. 1 is a schematic diagram of the main equipment of the steam turbine exhaust steam recovery system of the present invention.
Fig. 2 is a calculation block diagram showing a procedure of determining design parameters of each device in the recycling system of embodiment 1.
Fig. 3 is a graph showing the relationship between the isentropic efficiency of the compressor and the system COP.
Fig. 4 is a graph showing the relationship between the isentropic efficiency of the turbine and the system COP.
Fig. 5 is a schematic view showing the main equipment of the exhaust steam recovery system of the steam turbine of embodiment 2.
Fig. 6 is a schematic diagram showing the main equipment of the exhaust steam recovery system of the steam turbine of embodiment 3.
Fig. 7 is a block diagram showing a cogeneration technology system in the prior art which employs a steam extraction and heating technology of a steam turbine intermediate pressure cylinder.
Detailed Description
The invention will be described in more detail below with reference to the accompanying drawings. While certain embodiments of the present invention are shown in the drawings, it is to be understood that the present disclosure may be embodied in various forms and should not be construed as limited to the embodiments set forth herein, but rather are provided for a more thorough and complete understanding of the present invention. It should be understood that the drawings and the embodiments of the present invention are illustrative only and are not intended to limit the scope of the present invention.
Example 1
1. Main equipment of waste steam recovery system of steam turbine
Hereinafter, a recovery system of exhaust steam from a steam turbine will be described as example 1 in the case of heating by heating return water of a heating network of a cogeneration unit, but the recovery system of the present invention is not limited to the case of heating, and can be widely applied to various fields in which a heating target is heated by exhaust steam from a steam turbine, for example, applications such as temperature rise, distillation, drying, and condensation in industrial production.
FIG. 1 is a schematic diagram of the main equipment of the steam turbine exhaust steam recovery system of the present invention. As shown in fig. 1, the recovery system includes a first warming unit and a second warming unit. The first warming unit includes: a steam compressor 1 that boosts main turbine exhaust steam from a main turbine to a first pressure; and a first heater (primary heating network heater) 4 for performing a first temperature rise on heating target heating network backwater by using the exhaust steam boosted by the steam compressor to make the temperature of the heating target heating network backwater reach a first temperature. The second warming unit includes: the dragging steam turbine 2 is driven by exhaust gas of a middle pressure cylinder of the main steam turbine, drags the steam compressor, and discharges dragging steam turbine exhaust steam which is depressurized to a second pressure; and a second heater (secondary heating network heater) 5 for carrying out second temperature rise on the heating object, namely the heating network backwater by using the dragging steam turbine exhaust steam to enable the temperature to reach a second temperature.
Further, the recycling system may further include: the steam-water separator 6 is used for inputting the dead steam from the main steam turbine and performing steam-water separation, improving the dryness of the dead steam and outputting the dead steam with high dryness to the steam compressor; the first drain pump 7 is used for conveying drain generated in the primary heat supply network heater 4 to a plant area heat recovery system; and a second drain pump 8 which delivers drain water generated in the secondary heat supply network heater 5 to the plant regenerative system. Wherein the steam-water separator 6 is used to ensure the safety of the blades of the steam compressor 1. The compressor rotates at a high speed, when the moisture content of the exhaust steam is high, the dry steam contains trace water drops which impact on the compressor blades to cause the water erosion of the blades, and the moisture content is increased to more than 0.99 by a plurality of degrees, so that the service life of the compressor is prolonged, the safety of the system is prolonged, the service life is prolonged, and the profitability is improved. The steam-water separator 6 is used for dehumidifying the exhaust steam, a mechanical separation method is adopted, the dehumidification device is arranged at the inlet of the steam compressor, and the exhaust steam enters the steam compressor 1 after the dryness of the exhaust steam passes through the steam-water separator 6 and is increased (for example, the dryness can be increased to more than 0.99). The first drain pump 7 and the second drain pump 8 pump the boosted drained water into a host hot well to realize the recovery of working media and heat.
Further, the first warming unit further includes an intercooler 3. To improve the reliability and economy of a vapor compressor and reduce the design difficulty of the compressor, a surface vapor cooler may be employed to cool the spent vapor between two of the plurality of compression stages of the compressor. For example, in a 4-stage steam compressor, the temperature and pressure of the exhaust steam are increased after 1 st and 2 nd stages of compression, but the increased temperature reduces the efficiency of the compressor for the subsequent 3 rd and 4 th stages of compression, and therefore, the intercooler 3 is disposed between the 2 nd and 3 rd stages for facilitating the subsequent 3 rd and 4 th stages of compression to increase the efficiency of the compressor. The use of an intercooler can increase the efficiency of the compressor and thus also the COP of the system. The cooling medium used in the intercooler 3, i.e., the cooling water, is derived from the return water of the heat supply network, and the cooling water having passed through the intercooler 3 is merged into the return water of the heat supply network having the first temperature on the downstream side of the first-stage heat supply network heater, that is, as shown in fig. 1, the intercooler 3 is connected in parallel to the first-stage heat supply network heater 4, and the return water of the heat supply network is branched to a part to intermediate-cool the exhaust steam of the main turbine between two predetermined compression stages among the plurality of compression stages, and the part of the return water of the heat supply network is subjected to intermediate cooling and then merged with the return water of the heat supply network heated by the first-stage heat supply network heater 4. Since the cooling medium used by the intercooler 3 is the return water of the heat supply network circulating water which is the heating object of the system, the heat energy converted from the mechanical energy in the steam compressor 1 is absorbed by the return water of the heat supply network, and is merged with the return water of the heat supply network heated by the primary heat supply network heater 4 and then sent to the heating heat supply network, so that the energy is used by the heating object without being wasted, and the COP of the system is improved.
As shown in fig. 1, an upstream end of the steam-water separator 6 is connected to the exhaust steam of the main turbine, and a downstream end thereof is connected to an upstream end of the steam compressor 1; the downstream end of the steam compressor 1 is connected to a primary heat supply network heater 4; the upstream end of the dragging turbine 2 is connected to the intermediate pressure cylinder exhaust steam of the main turbine, the downstream end is connected to the secondary heat supply network heater 4, and mechanical power is output to the steam compressor 1 to drive the steam compressor 1 to operate. The connection between the above-described devices can be realized by using existing pipes, valves, joints, connectors, and the like, and a detailed description thereof is omitted.
The steam-water separator 6, the first drain pump 7, and the second drain pump 8 may be independent of the recovery system of the present invention, and are not limited to those having the function means in the recovery system, as long as the same function can be provided to the recovery system of the present invention. Furthermore, the compression stage number of the vapor compressor 1 is determined according to the specific use environment, and the position where the intercooler 3 is disposed may also be actually selected according to the needs of the system target.
2. Technical principle of recovery system of exhaust steam of steam turbine
Hereinafter, the technical principle of the exhaust steam recovery system of a steam turbine according to the present invention will be described based on examples.
The recovery system of the steam turbine exhaust steam in embodiment 1 heats the return water of the heat supply network according to the sequence of first temperature rise and then second temperature rise. Dragging a centrifugal steam compressor 1 through a back pressure type industrial steam turbine 2, compressing and boosting the exhaust steam pressure of a steam turbine of a thermal power plant from about 8-15 kPa to about 35-45 kPa, and then entering a primary heat supply network heater 4 to heat circulating water of a heat supply network; the inlet steam of the back pressure type industrial steam turbine 2 comes from the exhaust steam of a main steam turbine intermediate pressure cylinder, the pressure is 790-810 kPa, when the boiler is in non-full load operation, the exhaust steam of the intermediate pressure cylinder can be as low as about 500kPa, the inlet temperature is 310-330 ℃, the exhaust steam pressure of the back pressure type industrial steam turbine 2 is about 82-92 kPa, and the exhaust steam enters a secondary heat supply network heater 5 to heat supply network circulating water coming out of the primary heat supply network heater. The purpose of recovering low-quality dead steam to the maximum extent by using less high-quality steam (exhausted steam of the intermediate pressure cylinder) is realized by the process.
Next, a specific example of the operation of each of the first temperature raising means and the second temperature raising means in example 1 will be described on the assumption that the return water temperature from the city heat supply network circulating water is 50 ℃ and the city heating water temperature is 95 ℃, when the feed amount of the single unit of the recovery system of the present invention is 500 t/h.
Circulating water flow: gw=500t/h;
Steam turbine exhaust steam pressure: p is a radical of0=8kPa;
Steam turbine exhaust steam dryness: x is 0.94;
return water temperature of the heat supply network: t is tw1=50℃;
Temperature of water supplied to heat supply network: t is tw5≥95℃;
Inlet steam pressure of industrial steam turbine: p is a radical ofT1=0.8MPa;
Inlet steam temperature of industrial steam turbine: t is tT1=320℃。
In the first temperature rising unit, the pressure of the exhaust steam from the main steam turbine is designed according to 8kPa, the dryness is generally within the range of 92% -95%, and after the exhaust steam passes through the steam-water separator 6, the dryness is raised to more than 0.99 and then enters the steam compressor 1. The compressor is designed according to four stages and two sections and one cylinder, the four stages are arranged in one cylinder body to simplify the structure, the first stage and the second stage are one stage, the pressure rise ratio of each stage is about 1.4-1.7, after the first stage and the second stage of compression, the exhaust steam pressure rises to about 15-23 kPa (for example, 18kPa in the embodiment), and the temperature rises to about 103-113 ℃ (for example, 108 ℃); in order to improve the reliability and the economy of the compressor and reduce the design difficulty of the compressor, a surface type steam cooler 3 is arranged in front of the third stage of the compressor, cooling water comes from circulating water return of a heat supply network, the temperature is about 50 ℃, the temperature of cooled exhaust steam is about 75-85 ℃ (about 80 ℃ in the embodiment), then the exhaust steam enters the third stage and the fourth stage of the compressor, the pressure is increased to about 35-45 kPa (about 40kPa in the embodiment) after the compression, the temperature is increased to about 165-175 ℃ (about 171 ℃ in the embodiment), and then the exhaust steam enters a first stage heat supply network heater 4.
In the second heating unit, the inlet steam of the back pressure turbine 2 comes from the steam exhaust of the intermediate pressure cylinder of the main turbine, the pressure is 800KPa (0.8MPa), the temperature is 320 ℃, the steam enters the back pressure turbine and then expands to do work, the internal energy of the steam is converted into mechanical energy to drag the steam compressor to work, the steam exhaust pressure of the back pressure turbine is designed to be about 87kPa, the energy level quality of the steam exhaust can heat the circulating water of the heat supply network to 95 ℃, and the steam exhaust can drag the exhaust steam of the steam turbine to directly enter the secondary heat supply network heater 5.
The return water temperature of the heat supply network is about 50 ℃, a small part of 13t/h is extracted from the upstream side of the first-stage heat supply network heater 4 and enters the intercooler 3 for cooling the intermediate-stage steam of the steam compressor 1, and the rest of the large part of the steam enters the first-stage heat supply network heater 4, and the temperature reaches 75 ℃ after the temperature is raised; and the heat supply network circulating water from the intercooler 3 and the heat supply network circulating water from the outlet of the primary heat supply network heater 4 are converged and then enter the secondary heat supply network heater 5, and the temperature is raised to 95 ℃ and then enters the urban heat primary network for heat supply.
The hydrophobic temperature in the primary heat supply network heater 4 is about 56 ℃, and the temperature is boosted by the primary hydrophobic pump 7 and then is pumped into a host heat well according to the principle of thermodynamic system energy level matching, so that the recovery of working media and heat is realized. The hydrophobic temperature in the secondary heat supply network heater 5 is about 81 ℃, and the hydrophobic temperature is boosted by the secondary hydrophobic pump 8 and then is pumped into a host hot well to realize the recovery of working media and heat.
3. Thermodynamic design of steam turbine exhaust steam recovery system
Fig. 2 is a calculation block diagram showing a process of determining design parameters of each device in the recycling system of embodiment 1. Hereinafter, the description will be made in detail with reference to fig. 2.
According to the exhaust steam parameters and the design and manufacturing level of the field of the current compressor, the isentropic efficiency of the compressor is initially selected to be 84 percent; according to the driving parameters of the steam turbine and the design and manufacturing level of the current steam turbine field, the isentropic efficiency of the steam turbine is initially selected to be 82%. In addition, when there is a change in the actual technical level, it is necessary to adjust the set values of the compressor isentropic efficiency and the turbine isentropic efficiency accordingly.
According to the requirement that the water supply temperature of a heat supply network is more than or equal to 95 ℃, the back pressure of an industrial steam turbine is designed according to 100kPa, the corresponding saturation temperature is 100 ℃, and the requirement that the water supply temperature is more than 95 ℃ can be met after a certain end difference of a secondary heater is considered.
The compressor outlet pressure is selected by adopting a trial calculation mode, namely, the compressor outlet pressure is assumed first, and then the whole system is calculated.
And calculating the enthalpy of the steam at the inlet and the outlet according to the selected outlet pressure of the compressor and the known parameters of the pressure and the dryness of the steam at the inlet of the compressor. The compressor isentropic efficiency (compressor design parameter) is selected. The enthalpy of the outlet steam of the compressor can be calculated by the parameters. The process from the outlet of the compressor to the inlet of the primary heater is adiabatic, so the enthalpy of the steam at the inlet of the primary heater is the enthalpy of the steam at the outlet of the compressor.
Compressor intercooler design principle: the cooling water comes from the circulating water of the heat supply network, calculated according to 50 ℃ in the embodiment 1; the outlet steam temperature of the intercooler needs to be determined by comprehensively considering the influence of the inlet steam temperature on the performance of the compressor, and is calculated according to 80 ℃ in the embodiment 1; the intercooler outlet water temperature was calculated as 70 ℃ in this example 1, considering this heat recovery pattern.
And selecting the end difference (heater design parameter) of the primary heater according to the selected outlet pressure of the compressor, and calculating the outlet water temperature and the outlet water enthalpy of the primary heater.
The hydrophobic temperature of the primary heat supply network heater is the sum of the inlet water temperature of the heater and the inlet end difference of the primary heater, the hydrophobic temperature can be calculated when the inlet end difference of the heater is given, and the hydrophobic enthalpy can be calculated according to the water vapor property function.
And performing heat balance calculation on the primary heater according to the calculated inlet steam enthalpy, outlet water enthalpy and drainage enthalpy of the primary heater to obtain the inlet steam flow.
And calculating to obtain the internal power of the compressor according to the inlet steam enthalpy, the outlet steam enthalpy and the steam flow of the compressor.
According to the internal power of the compressor, certain transmission loss is considered, and the internal power of the steam turbine can be obtained.
Assume turbine discharge pressure. And calculating to obtain the outlet steam enthalpy according to the steam property function of the steam turbine inlet steam parameter pressure and temperature. The turbine internal efficiency, i.e. isentropic efficiency (turbine design parameter) is selected. And calculating the exhaust enthalpy of the steam turbine according to the parameters.
And calculating the steam quantity of the steam turbine according to the steam enthalpy of the steam turbine inlet, the exhaust steam enthalpy and the internal power.
The steam turbine exhausts to the secondary heater in an adiabatic process, and the steam enthalpy at the inlet of the secondary heater is the exhaust steam enthalpy of the steam turbine. The hydrophobic temperature of the secondary heater is the saturation temperature corresponding to the steam pressure, and the hydrophobic enthalpy is calculated according to the water steam property function. And carrying out heat balance calculation according to the steam enthalpy, the hydrophobic enthalpy and the steam quantity of the inlet of the secondary heater to obtain the water temperature of the outlet of the secondary heater.
And selecting the end difference (heater design parameter) of the secondary heater according to the water temperature at the outlet of the secondary heater, and calculating the steam exhaust pressure of the steam turbine.
And comparing the steam turbine exhaust pressure obtained by calculation with the assumed exhaust pressure, and performing trial calculation repeatedly to approach gradually. Finally, the exhaust pressure of the steam turbine is determined. When the computer is used for calculation, an iterative solution process is adopted.
And checking whether the water temperature at the outlet of the secondary heater meets the requirement of more than 95 ℃, if so, finishing the calculation, and outputting a result. If not, resetting the outlet pressure of the compressor, repeating the steps until the requirement is met, and finishing the calculation.
The calculations in Table 1 below show the results of one of the calculations described above, assuming a compressor outlet pressure of 39.77kPa, and as a result, a secondary heater outlet water temperature of > 95 deg.C is satisfied, while the system COP is 2.32.
TABLE 1-1
Tables 1 to 2
Tables 1 to 3
4. Compressor with a compressor housing having a plurality of compressor blades | |||||
4.1 the first stage | |||||
49. | Inlet steam pressure | kPa | pC1in | =p00 | 8.00 |
50. | Inlet steam quality | *** | xC1in | It is known that | 0.99 |
51. | Enthalpy of inlet steam | kJ/kg | hC1in | =swpxah(pC1in/1000,xC1in) | 2553.08 |
52. | Inlet steam entropy | kJ/kg℃ | sC1in | =swpxas(pC1in/1000,xC1in) | 8.15 |
53. | Inlet steam flow | t/h | GC1 | =Gheater1 | 20.28 |
54. | Compressor efficiency | % | ηC1 | It is known that | 84.00 |
55. | Compressor outlet pressure | kPa | pC1out | =pC2in | 11.95 |
56. | Isentropic enthalpy of outlet | kJ/kg | h′C1out | =swpsah(pC1out/1000,sC1in) | 2612.53 |
57. | Enthalpy of outlet | kJ/kg | hC1out | =(h′C1out-hC1in×(1-ηC1/100))/ηC1×100 | 2612.15 |
58. | Outlet temperature | ℃ | tC1out | =swphat(pC1out/1000,hC1out) | 66.41 |
59. | Shaft power | kW | PC1 | =GC/3.6×(hC1out-hC1in) | 396.24 |
4.2 second stage | |||||
60 | Inlet steam pressure | kPa | pC2in | =pC2out/ε2 | 11.95 |
61. | Inlet steam temperature | ℃ | tC2in | =tC1out | 66.41 |
62. | Enthalpy of inlet steam | kJ/kg | hC2in | =hC1out | 2623.4 |
63. | Inlet steam entropy | kJ/kg℃ | sC2in | =swptas(pC2in/1000,tC2in) | 8.19 |
64. | Inlet steam flow | t/h | GC2 | =Gheater1 | 20.28 |
65. | Compressor efficiency | % | ηC2 | It is known that | 84.00 |
66. | Compressor outlet pressure | kPa | pC2out | =pC3in | 17.84 |
67. | Isentropic enthalpy of outlet | kJ/kg | h′C2out | =swpsah(pC2out/1000,sC2in) | 2689.24 |
68. | Enthalpy of outlet | kJ/kg | hC2out | =(h′C2out-hC2in×(1-ηC2/100))/ηC2×100 | 2701.78 |
69. | Outlet temperature | ℃ | tC2out | =swphat(pC2out/1000,hC2out) | 107.95 |
70. | Shaft power | kW | PC2 | =GC/3.6×(hC2out-hC2in) | 441.61 |
Tables 1 to 4
Tables 1 to 5
4. Equipment design selection of recovery system of steam turbine exhaust steam
Based on the results of the thermodynamic calculations described above, each of the devices in the recovery system of the present invention is designed and selected.
4.1. Vapor compressor
With respect to the vapor compressor, the calculation results in the above calculation process table are as follows,
entrance parameters: the flow rate is 20.28t/h, the pressure is 8kPa, and the dryness is 99 percent;
and (3) outlet parameters: 39.77kPa, 170.7 ℃.
The output of the compressor meets the requirement of boosting and upgrading dead steam, the total boosting ratio is about 4.97, the required stages are determined according to the design and manufacturing level of the compressor, and the compressor is considered according to four stages of stages in the embodiment 1. The relationship between the isentropic efficiency of the compressor and the system COP is shown in FIG. 3, the isentropic efficiency and the COP are in a monotonic relationship, and the higher the isentropic efficiency, the higher the system COP. Therefore, the structural design, the pneumatic design and the like of the compressor should meet the strength requirement and simultaneously improve the isentropic efficiency to the maximum extent, and the embodiment 1 is considered according to 84%.
4.2. Back pressure type industrial steam turbine
With respect to the back pressure type industrial steam turbine, the calculation results in the above calculation process table are as follows,
entrance parameters: the pressure is 0.8MPa, the temperature is 320 ℃, and the steam flow is 17.08 t/h.
Steam discharge parameters: 87.69 kPa.
The output of the steam turbine is matched with the output of the compressor, and the variable working condition operation characteristic is wide.
The relationship between the isentropic efficiency of the steam turbine and the system COP is shown in FIG. 4, the isentropic efficiency and the COP are in a monotonous relationship, and the higher the isentropic efficiency is, the higher the system COP is. Therefore, the structural design, the aerodynamic design and the like of the steam turbine should meet the strength requirement and simultaneously improve the isentropic efficiency to the maximum extent, and the embodiment 1 is considered according to 82%.
4.3. First-level heating network heater
A shell-and-tube heater is adopted, because the inlet steam is superheated steam, the end difference is selected according to the temperature not higher than 0 ℃, and the heat exchange area allowance is considered according to 10%; the pipe material is selected according to the requirement of the water quality of circulating water of a heat supply network, and is generally not lower than TP 316L.
4.4. Two-stage heating network heater
A shell-and-tube heater is adopted, the end difference is selected according to the temperature of not more than 1.5 ℃, and the heat exchange area allowance is considered according to 10%; in the process of certain variable working conditions of the steam turbine, the condition of overheating of the exhaust steam of the industrial steam turbine can occur, and in order to fully reduce the irreversible loss of heat exchange, the design of a drainage cooling section is considered during the structural design; the pipe material is selected according to the requirement of the water quality of circulating water of a heat supply network, and is generally not lower than TP 316L.
4.5. Exhaust steam system pipeline
In order to effectively reduce the pressure loss of the exhaust steam system, the pipe diameter is designed to be selected according to the lower limit of the recommended flow rate of the pipeline design rule.
5. Heat supply capacity and heat economy of steam turbine exhaust steam recovery system
According to the design principle and the method, the system is subjected to thermodynamic calculation analysis, and the main thermal economic indexes are shown in table 2.
TABLE 2 Main thermal economic indicators of the System
According to the design idea of the system, the heat supply capacity and the heat supply economy are calculated, when the recovery system absorbs 20.28t/h of dead steam, only 17.08t/h of high-quality intermediate pressure cylinder exhaust steam is needed, namely each ton of high-quality steam can absorb 1.19t/h of dead steam, and the COP of the recovery system can reach 2.32.
Example 2
In the above embodiment 1, it is explained that the exhaust steam recovery system of the present invention is applied to a city heating system and has the first warming unit and the second warming unit. However, the recycling of the exhaust steam of the main turbine is not limited to the simultaneous use of the first warming unit and the second warming unit in embodiment 1, and the use is not limited to heating the return water of the heat supply network to 95 ℃ or more in an urban heating system. Fig. 5 is a schematic view showing the main equipment of the exhaust steam recovery system of the steam turbine of embodiment 2. As shown in fig. 5, in example 2, the system for recovering exhaust steam from a steam turbine according to the present invention includes only the first temperature increasing means without the second temperature increasing means. The first temperature increasing means in embodiment 2 is the same as that in embodiment 1, and a description thereof will not be repeated. Further, the drive source of the steam compressor 1 in the first warming unit may employ any drive source other than the traction turbine 2, for example, the motor 2 is used to provide a drive force to the steam compressor 1. In this case, the technical parameters of the steam compressor 1, the intercooler 3, and the primary heat supply network heater 4 are appropriately designed according to the parameters of the exhaust steam of the main turbine and the heating temperature requirement of the heating target, referring to the technical principle and the thermodynamic design in embodiment 1, and the exhaust steam from the main turbine can be effectively used.
Example 3
In the above embodiment 1, it is explained that the exhaust steam from the main turbine is pressurized for the primary temperature rise and the exhaust gas from the intermediate pressure cylinder of the main turbine is depressurized for the secondary temperature rise. In example 3, in contrast to example 1, as shown in fig. 6, exhaust gas from a main turbine intermediate pressure cylinder is depressurized and used for primary temperature rise, exhaust steam from the main turbine is pressurized and used for secondary temperature rise, 800kPa intermediate pressure cylinder exhaust gas from the main turbine is used to drive a drag turbine 2, the drag turbine 2 discharges drag turbine exhaust steam of 45kPa, the drag turbine exhaust steam is introduced into a secondary heat supply network heater 5 to primarily heat supply network return water at 50 ℃ to 75 ℃, the exhaust steam from the main turbine passes through a steam-water separator 6 and then is introduced into a steam compressor 1, the exhaust steam is compressed in stages 1 and 2 in the steam compressor 1, then is cooled by an intercooler 3 and further compressed in stages 3 and 4, and after being pressurized to 87kPa, the exhaust steam is introduced into a primary heat supply network heater 4 to secondarily heat supply network return water after primary temperature rise, the temperature was raised to 95 ℃. The intercooler 3 uses a part of the heat supply network return water after the primary temperature rise as a cooling medium, and the cooling medium is joined to the heat supply network return water after the secondary temperature rise downstream of the secondary heat supply network heater 5 to supply water as a heat supply network. In this case, referring to the technical principle and the thermal design in example 1, the technical parameters of the steam compressor 1, the intercooler 3, the primary heat supply network heater 4, the traction turbine 2, the secondary heat supply network heater 5, and the like are appropriately designed, so that the exhaust steam from the main turbine can be effectively used, and the COP of the recovery system in example 3 can be 2.03 by the same calculation method as in example 1, in which the exhaust gas from the intermediate pressure cylinder of the main turbine is used as the power source for the traction turbine and the heat source for the secondary heat supply network heater.
6. Technical effect of recovery system of exhaust steam of steam turbine
When the recovery system in the embodiment 1 absorbs the exhaust steam for 20.28t/h, only 17.08t/h of the exhaust steam of the high-quality intermediate pressure cylinder is needed, namely each ton of high-quality steam can absorb 1.19t/h of the exhaust steam, and each ton of high-quality steam can absorb about 0.6-0.7 t/h of the exhaust steam of the current mainstream absorption heat pump, for example, the steam drives the absorption heat pump, the high-quality steam is used for absorbing the low-quality exhaust steam, the rated working condition is 0.7, the actual working condition can reach 0.6, the efficiency can be reduced to 0.3 or even 0.2 year by year along with the passing of the use time, the recovery system no longer has an obvious energy-saving effect, and a. The recovery system of the present invention therefore has at least 70% greater capacity to absorb the exhaust steam than the mainstream absorption heat pump.
In addition, the COP of the recovery system can reach 2.32, the COP of the current mainstream absorption heat pump is about 1.7 generally, and the COP of the recovery system is 90% higher than that of the absorption heat pump. Even if the actual parameters of the equipment during operation are considered to be possibly different from the design parameters, or an optimally designed device cannot be selected due to certain unavoidable factors, the COP of the recovery system is higher than that of the prior art, namely the COP is more than 1.7 and can reach 2.32 at the maximum, and the COP can reach 2.2 conservatively.
According to the calculation of 5 months in one heat supply season, when 33.92 ten thousand GJ are provided under the same heat supply amount, the heat supply amount of the exhaust steam is 5.5 thousand GJ more than that of the absorption heat pump, and the energy-saving effect is very obvious when the standard coal is converted into 1878 tons.
According to the recovery system for recovering the exhaust steam of the steam turbine by adopting the cascade utilization and supercharging upgrading technology, the compressor is dragged by the back pressure type steam turbine, the exhaust steam flow of the low-pressure cylinder of the main machine is reduced, the cold source loss of the main machine is reduced, and compared with an electric driving mode, the recovery system reduces the energy conversion link and improves the economy of the main machine.
In addition, the steam turbine dragging the compressor adopts a back pressure type, exhaust steam directly enters the heat supply network heater to be used for heating heat supply network circulating water, no cold source loss exists, and the circulating efficiency of the steam turbine is 100%.
In addition, the compressor is the centrifugal compressor after optimizing, is applied to the technical maturity in vapor compression field, and is efficient, compares with adopting surface formula heat transfer to retrieve the exhaust steam mode (like absorption heat pump), has reduced the heat transfer number of times, and the heat transfer end difference is little, and economic nature is good.
In addition, according to the principle of thermodynamic system energy level matching, the circulating water side of the heat supply network is designed into a step heating system: the steam compressor is a device for converting mechanical work into steam internal energy, the exhaust steam level of the main steam turbine is the lowest, the exhaust steam pressure of the main steam turbine is compressed to about 35-45 kPa through the compressor, and the capacity of heating the circulating water of the heat supply network from 50 ℃ to about 75 ℃ is achieved, so that the exhaust steam at the outlet of the compressor enters the first-stage heat supply network heater; the back pressure type industrial steam turbine exhaust is equipment for converting steam internal energy into mechanical energy, the steam level of a steam turbine inlet is high, the exhaust pressure after work is done is controlled to be 80-90 kPa, the capacity of heating heat supply network circulating water from 75 ℃ to about 95 ℃ is achieved, and therefore exhaust steam at the back pressure type steam turbine outlet enters a secondary heat supply network heater. The primary heater steam source and the secondary heater steam source respectively correspond to the compressor and the steam turbine, and the sequence is determined according to the quality of the exhausted steam of the main steam turbine after being upgraded by the compressor and the quality of the steam of the industrial steam turbine after doing work, so that the optimal matching of low-quality exhausted steam upgrading and high-quality steam degradation is realized, a step heating system distributed according to the steam energy level is formed, the entropy increase of the overall design of the system is minimum, and the economy is optimal.
In addition, the whole system does not use the technology of directly heating the circulating water of the heat supply network by high-quality steam, adopts the high-quality steam to do work in the steam turbine firstly, and then heats the circulating water of the heat supply network by exhaust steam, thereby avoiding the condition of degrading the use of the high-quality steam and effectively improving the economical efficiency of the system.
7. Use of a system for recovering exhaust steam from a steam turbine
The recovery system for recovering the exhaust steam of the steam turbine by adopting the cascade utilization and supercharging upgrading technology can be widely applied to facilities using the steam turbine in a thermal power plant and the like for recovering the waste heat of the exhaust steam of the steam turbine, the system COP can reach 2.32 after optimization, the conservation prediction can also reach more than 2.2, the economy is superior to that of the current mainstream absorption heat pump, the operation flexibility is superior to that of a high-back-pressure heat supply mode, the service life of equipment is long, the recovery system can be popularized as an important technology for recovering the waste heat of the thermal power plant or recovering the waste heat in other facilities using the steam turbine, and the recovery system can be widely applied to urban heating and other.
In addition, in the above embodiments 1 to 3, it is described that the exhaust steam is from the main turbine in the thermal power plant to heat the return water of the urban heat supply network, but the source of the exhaust steam is not limited to the boiler of the thermal power plant, the exhaust steam from any source can be used as the application target, the heating target is not limited to the return water of the heat supply network, and the ranges of the various pressures and temperatures described in the above embodiments are ranges defined for explaining the applications exemplified in the embodiments, and when the source of the exhaust steam or the heating target is changed, the ranges of the various pressures and temperatures and the ranges of the steam amount described above should be also adaptively adjusted, and are not limited to the ranges in the above embodiments.
The foregoing description is only exemplary of the preferred embodiments of the invention and is illustrative of the principles of the technology employed. It will be appreciated by those skilled in the art that the scope of the disclosure herein is not limited to the particular combination of features described above, but also encompasses other embodiments in which any combination of the features described above or their equivalents is encompassed without departing from the spirit of the disclosure. For example, the above features and (but not limited to) features having similar functions disclosed in the present invention are mutually replaced to form the technical solution.
Claims (8)
1. A recovery system for recovering the exhaust steam of a steam turbine by adopting cascade utilization and supercharging upgrading technology is characterized in that,
the temperature-raising device is provided with a first temperature-raising unit,
the first warming unit includes:
a steam compressor (1) which boosts the main turbine exhaust steam from the main turbine to a first pressure, and
a first heater (4) for first heating the heating target to a first temperature by using the exhaust steam boosted by the steam compressor;
the vapor compressor (1) is a centrifugal compressor having a plurality of compression stages;
the first warming unit further includes an intercooler (3) connected in parallel with the first heater (4), branching the heating target before the first warming into a part to intercool the main turbine exhaust steam between predetermined two compression stages among the plurality of compression stages, and the part of the heating target joining the heating target warmed to the first temperature by the first heater after the intercooling.
2. The system for recovering the exhaust steam of the steam turbine by the utilization of the cascade and the pressurizing upgrading technology according to claim 1,
a second temperature raising means is further provided,
the second warming unit includes:
a drag turbine (2) driven by the intermediate pressure cylinder exhaust from the main turbine, dragging the steam compressor, and discharging the drag turbine exhaust steam depressurized to a second pressure, and
a second heater (5) for performing a second temperature rise on the heating object to a second temperature by using the steam exhaust of the dragging steam turbine;
the first pressure is lower than the second pressure, and the first temperature is lower than the second temperature;
the second temperature raising means is provided downstream of the first temperature raising means in the conveying direction of the heating target, and performs second temperature raising of the heating target output from the first temperature raising means to the second temperature.
3. The system for recovering the exhaust steam of the steam turbine by the utilization of the cascade and the pressurizing upgrading technology according to claim 1,
a second temperature raising means is further provided,
the second warming unit includes:
a drag turbine (2) driven by the intermediate pressure cylinder exhaust from the main turbine, dragging the steam compressor, and discharging the drag turbine exhaust steam depressurized to a second pressure, and
a second heater (5) for performing a second temperature rise on the heating object to a second temperature by using the steam exhaust of the dragging steam turbine;
the first pressure is higher than the second pressure, and the first temperature is higher than the second temperature;
the first temperature raising means is provided downstream of the second temperature raising means in the conveying direction of the heating target, and first raises the temperature of the heating target output from the second temperature raising means to the first temperature.
4. The recovery system for recovering the exhaust steam of the steam turbine by adopting the cascade utilization and pressurization upgrading technology according to claim 2 or 3,
the dragging turbine (2) is a back pressure turbine.
5. The system for recovering the exhaust steam of the steam turbine by the utilization of the cascade and pressurizing upgrading technology according to claim 2,
the exhaust steam of the main steam turbine is exhaust steam of a steam turbine of a thermal power plant, and the heating object is heat supply network return water of circulating water of an urban heat supply network.
6. The system for recovering the exhaust steam of the steam turbine by the utilization of the cascade and pressurizing upgrading technology according to claim 5,
the pressure of the exhaust steam of the main steam turbine is 8 kPa-15 kPa, the temperature of the return water of the heat supply network is 45-55 ℃, the first pressure is 35-45 kPa, the first temperature is 70-80 ℃, the second temperature is 95-100 ℃, the pressure of the exhaust gas of the intermediate pressure cylinder is 790-810 kPa, and the second pressure is 80-90 kPa,
the COP of the recovery system is 1.7-2.32.
7. The system for recovering the exhaust steam of the steam turbine by the utilization of the cascade and pressurizing upgrading technology according to claim 3,
the exhaust steam of the main steam turbine is exhaust steam of a steam turbine of a thermal power plant, and the heating object is heat supply network return water of circulating water of an urban heat supply network.
8. The system for recovering the exhaust steam of the steam turbine by the cascade utilization and supercharging upgrading technology according to claim 7,
the pressure of the exhaust steam of the main steam turbine is 8 kPa-15 kPa, the temperature of the return water of the heat supply network is 45-55 ℃, the first pressure is 80-90 kPa, the first temperature is 95-100 ℃, the second temperature is 70-80 ℃, the pressure of the exhaust gas of the intermediate pressure cylinder is 40-50 kPa, and the second pressure is 80-90 kPa,
the COP of the recovery system is 1.7-2.03.
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