A steam turbine waste heat utilization system and control method thereof

Abstract

The invention discloses a steam turbine waste heat utilization system, including a steam ejector, an air inlet of the steam ejector is connected to an exhaust pipe of a low-pressure cylinder of a steam turbine, a low-temperature water inlet pipe and a high-temperature water outlet pipe are connected to the steam ejector, the low-temperature water in the low-temperature water inlet pipe absorbs heat in the steam ejector and becomes high-temperature water and is discharged from the high-temperature water outlet pipe, the air outlet of the steam ejector is connected to a low-temperature heat source inlet of an endothermic heat pump, a condensed water drain pipe of the endothermic heat pump is connected to the low-temperature water inlet pipe, the exhaust pipe of the low-pressure cylinder of the steam turbine is connected to the high-temperature heat source inlet of the endothermic heat pump, a low-temperature water inlet pipe and a medium-temperature water outlet pipe are connected to the endothermic heat pump, the low-temperature water in the low-temperature water inlet pipe absorbs heat in the endothermic heat pump and becomes medium-temperature water and is discharged from the medium-temperature water outlet pipe. The invention can improve the deficiencies of the prior art and improve the waste heat utilization rate of steam turbine units in thermal power plants.

Description

Technical Field

[0001] The invention relates to the technical field of steam turbine waste heat recovery and utilization, in particular to a steam turbine waste heat utilization system and a control method thereof. Background Art

[0002] After the steam turbine of a thermal power plant drives the generator to start, a large amount of high-temperature exhaust steam will be generated. In order to improve the overall efficiency of the coal-fired unit, it is necessary to recycle the waste heat of the high-temperature exhaust steam. In the existing waste heat recovery system, the waste heat of the high-temperature exhaust steam is usually recovered by heat exchange between the high-temperature exhaust steam and low-temperature water, but its recovery rate is only 30% to 40%. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a steam turbine waste heat utilization system and a control method thereof, which can solve the deficiencies of the prior art and improve the waste heat utilization rate of the steam turbine unit in a thermal power plant.

[0004] In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows.

[0005] A steam turbine waste heat utilization system comprises a steam ejector, wherein an air inlet of the steam ejector is connected to an exhaust pipe of a low-pressure cylinder of the steam turbine, a low-temperature water inlet pipe and a high-temperature water outlet pipe are connected to the steam ejector, low-temperature water in the low-temperature water inlet pipe absorbs heat in the steam ejector to become high-temperature water and then is discharged from the high-temperature water outlet pipe, an air outlet of the steam ejector is connected to an inlet of a low-temperature heat source of an endothermic heat pump, a condensed water drain pipe of the endothermic heat pump is connected to the low-temperature water inlet pipe, the exhaust pipe of the low-pressure cylinder of the steam turbine is connected to the inlet of a high-temperature heat source of the endothermic heat pump, a low-temperature water inlet pipe and a medium-temperature water outlet pipe are connected to the endothermic heat pump, low-temperature water in the low-temperature water inlet pipe absorbs heat in the endothermic heat pump to become medium-temperature water and then is discharged from the medium-temperature water outlet pipe.

[0006] Preferably, a heat exchange plate is installed in the steam ejector, a steam spray head is installed at the inner end of the steam ejector air inlet, a guide chamber is provided in the heat exchange plate, the liquid inlet end of the guide chamber is connected to the low-temperature water inlet pipe, a water spray head is installed at the liquid outlet end of the guide chamber, a plurality of through grooves are provided on the heat exchange plate, and a steam-water separator is installed on the air outlet of the steam ejector.

[0007] Preferably, the heat exchange plate is provided with a plurality of vertical grooves on the side facing the steam injection head, the grooves and the through grooves are arranged alternately, a plurality of fins separated from each other are installed in the grooves, and first through holes connected to the through grooves are provided on both sides of the grooves.

[0008] Preferably, a flow regulating valve is installed on the high-temperature water outlet pipe. By controlling the high-temperature water outlet flow rate, a certain amount of high-temperature water is stored at the bottom of the steam ejector. The steam ejector head is located below the high-temperature water liquid surface, and an aeration disk is installed on the steam ejector head.

[0009] Preferably, the water spray head comprises a plurality of water spray holes arranged side by side, the spray directions of adjacent water spray holes intersect each other, and the spray directions of all the water spray holes are located in the same plane.

[0010] Preferably, a spiral guide pipe is provided in the steam-water separator, the spiral guide pipe is connected to the inlet of the steam-water separator, a plurality of second through holes are evenly arranged on the spiral guide pipe, an arc-shaped baffle with a single-leaf hyperbolic shape is arranged on the outside of the spiral guide pipe, and a flared port is arranged at the outlet end of the spiral guide pipe, and the flared port is located inside the arc-shaped baffle plate.

[0011] A control method for a steam turbine waste heat utilization system comprises the following steps:

[0012] The high-temperature exhaust steam of the steam turbine is discharged from the exhaust pipe of the low-pressure cylinder of the steam turbine, enters the steam ejector for the first heat exchange with low-temperature water to produce high-temperature water, and the low-temperature exhaust steam after the first heat exchange enters the heat absorption heat pump, using the high-temperature exhaust steam as the driving heat source, and the low-temperature exhaust steam and low-temperature water undergo a second heat exchange to produce medium-temperature water. The condensed water generated by the heat absorption heat pump flows back to the low-temperature water inlet pipe for recycling.

[0013] The beneficial effect brought about by adopting the above technical scheme is that the present invention adopts a two-stage heat exchange structure to fully recover the heat in the exhaust steam. The first stage heat exchange adopts a steam jet contact heat exchange method, and the second stage heat exchange adopts a heat pump heat exchange method. For the steam ejector, the present invention has made targeted improvements. The present invention abandons the method of direct steam jet heat exchange. First, the high-temperature exhaust steam is passed into the high-temperature water for the first heat exchange. The flow rate of the high-temperature exhaust steam flowing out of the high-temperature water is reduced, and the secondary heat exchange is carried out on the surface of the heat exchange plate. Since the surface of the heat exchange plate adopts an alternating arrangement of grooves and through grooves, the high-temperature exhaust steam with a reduced flow rate can fully contact the fins in the grooves for heat exchange, and then flow through the heat exchange plate through the first through hole and the through groove, reducing the turbulence generated by the high-temperature exhaust steam in the heat exchange plate area. The high-temperature exhaust steam passing through the heat exchange plate undergoes a third heat exchange with the water flow sprayed from the water spray head. The spray of the water spray head can generate a water curtain, thereby further improving the heat exchange efficiency between the exhaust steam and the water body. After three low-temperature heat exchanges, the exhaust steam passes through the steam-water separator to separate the water and enter the heat pump. The high-temperature exhaust steam is used as the driving heat source to perform the fourth heat exchange on the low-temperature exhaust steam, thereby making full use of the exhaust steam heat. The steam-water separator is designed with an inner and outer two-layer separation structure to effectively improve the steam-water separation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a structural diagram of a specific implementation mode of the present invention.

[0015] Figure 2 It is a structural diagram of a steam ejector in a specific embodiment of the present invention.

[0016] Figure 3 It is a partial enlarged view of a heat exchange plate in a specific embodiment of the present invention.

[0017] Figure 4 It is a structural diagram of a steam-water separator in a specific embodiment of the present invention. DETAILED DESCRIPTION

[0018] Reference Figure 1-4 A specific embodiment of the present invention includes a steam ejector 2, an air inlet of the steam ejector 2 is connected to an exhaust pipe 1 of a low-pressure cylinder of a steam turbine, a low-temperature water inlet pipe 3 and a high-temperature water outlet pipe 4 are connected to the steam ejector 2, the low-temperature water in the low-temperature water inlet pipe 3 absorbs heat in the steam ejector 2 to become high-temperature water and is discharged from the high-temperature water outlet pipe 4, the air outlet of the steam ejector 2 is connected to a low-temperature heat source inlet of an endothermic heat pump 5, a condensed water drain pipe 6 of the endothermic heat pump 5 is connected to the low-temperature water inlet pipe 3, the exhaust pipe 1 of the low-pressure cylinder of the steam turbine is connected to the high-temperature heat source inlet of the endothermic heat pump 5, a low-temperature water inlet pipe 3 and a medium-temperature water outlet pipe 7 are connected to the endothermic heat pump 5, the low-temperature water in the low-temperature water inlet pipe 3 absorbs heat in the endothermic heat pump 5 to become medium-temperature water and is discharged from the medium-temperature water outlet pipe 7. A heat exchange plate 8 is installed in the steam ejector 2, a steam head 9 is installed at the inner end of the air inlet of the steam ejector 2, a guide chamber 10 is arranged in the heat exchange plate 8, the liquid inlet end of the guide chamber 10 is connected to the low-temperature water inlet pipe 3, a water head 11 is installed at the liquid outlet end of the guide chamber 10, a plurality of through grooves 12 are arranged on the heat exchange plate 8, and a steam-water separator 13 is installed on the air outlet of the steam ejector 2. A plurality of vertical grooves 14 are arranged on the side of the heat exchange plate 8 facing the steam head 9, the grooves 14 and the through grooves 12 are arranged alternately, a plurality of fins 15 separated from each other are installed in the grooves 14, and first through holes 16 connected to the through grooves 12 are arranged on both sides of the grooves 14. A flow regulating valve 17 is installed on the high-temperature water outlet pipe 4, and a certain amount of high-temperature water is stored at the bottom of the steam ejector 2 by controlling the high-temperature water outlet flow rate. The steam head 9 is located below the high-temperature water liquid surface, and an aeration plate 18 is installed on the steam head 9. The water spray head 11 includes a plurality of water spray holes 19 arranged side by side, the spray directions of adjacent water spray holes 19 intersect each other, and the spray directions of all water spray holes 19 are located in the same plane. A spiral guide pipe 20 is arranged in the steam-water separator 13, and the spiral guide pipe 20 is connected to the inlet of the steam-water separator 13. A plurality of second through holes 21 are evenly arranged on the spiral guide pipe 20. An arc baffle 22 in the shape of a single-leaf hyperboloid is arranged outside the spiral guide pipe 20. A flare 23 is arranged at the outlet end of the spiral guide pipe 20, and the flare 23 is located inside the arc baffle 22.

[0019] A control method for the above-mentioned steam turbine waste heat utilization system comprises the following steps:

[0020] The high-temperature exhaust steam of the steam turbine is discharged from the exhaust pipe 1 of the low-pressure cylinder of the steam turbine, enters the steam ejector 2, and undergoes the first heat exchange with the low-temperature water to produce high-temperature water. The low-temperature exhaust steam after the first heat exchange enters the heat absorption heat pump 5, and the high-temperature exhaust steam is used as a driving heat source. The low-temperature exhaust steam and the low-temperature water undergo a second heat exchange to produce medium-temperature water. The condensed water generated by the heat absorption heat pump 5 flows back to the low-temperature water inlet pipe 3 for recycling.

[0021] The invention can achieve a waste heat utilization rate of 45% to 47% for high-temperature exhaust steam of the steam turbine, effectively improving the waste heat utilization rate of exhaust steam of the steam turbine and saving the operating cost of the power plant.

[0022] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A steam turbine waste heat utilization system, characterized in that: The invention comprises a steam ejector (2), wherein an air inlet of the steam ejector (2) is connected to an exhaust pipe (1) of a low-pressure cylinder of a steam turbine, a low-temperature water inlet pipe (3) and a high-temperature water outlet pipe (4) are connected to the steam ejector (2), low-temperature water in the low-temperature water inlet pipe (3) absorbs heat in the steam ejector (2) and becomes high-temperature water, and then is discharged from the high-temperature water outlet pipe (4), an air outlet of the steam ejector (2) is connected to an inlet of a low-temperature heat source of an absorption heat pump (5), and a condensed water outlet of the absorption heat pump (5) is discharged from the high-temperature water outlet pipe (4). The water pipe (6) is connected to the low-temperature water inlet pipe (3), the low-pressure cylinder exhaust pipe (1) of the steam turbine is connected to the high-temperature heat source inlet of the heat absorption type heat pump (5), the heat absorption type heat pump (5) is connected to the low-temperature water inlet pipe (3) and the medium-temperature water outlet pipe (7), the low-temperature water in the low-temperature water inlet pipe (3) absorbs heat in the heat absorption type heat pump (5) and becomes medium-temperature water, and then is discharged from the medium-temperature water outlet pipe (7); a heat exchange plate (8) is installed in the steam ejector (2), and a heat exchange plate (9) is installed at the inner side end of the air inlet of the steam ejector (2) A steam injection head (9) is provided, a guide chamber (10) is arranged in the heat exchange plate (8), a liquid inlet end of the guide chamber (10) is connected to a low-temperature water inlet pipe (3), a water injection head (11) is installed at the liquid outlet end of the guide chamber (10), a plurality of through grooves (12) are provided on the heat exchange plate (8), and a steam-water separator (13) is installed at the gas outlet of the steam injector (2); a plurality of vertical grooves (14) are provided on one side of the heat exchange plate (8) facing the steam injection head (9), and the grooves (14) The grooves (14) are arranged alternately with the through grooves (12); a plurality of fins (15) separated from each other are installed in the grooves (14); first through holes (16) connected to the through grooves (12) are arranged on both sides of the grooves (14); a flow regulating valve (17) is installed on the high-temperature water outlet pipe (4); a certain amount of high-temperature water is stored at the bottom of the steam ejector (2) by controlling the high-temperature water outlet flow rate; the steam ejector head (9) is located below the high-temperature water liquid surface; an aeration disk (18) is installed on the steam ejector head (9).

2. The steam turbine waste heat utilization system according to claim 1, characterized in that: The water spray head (11) comprises a plurality of water spray holes (19) arranged side by side, the spray directions of adjacent water spray holes (19) intersect each other, and the spray directions of all the water spray holes (19) are located in the same plane.

3. The steam turbine waste heat utilization system according to claim 2, characterized in that: A spiral guide tube (20) is arranged inside the steam-water separator (13), the spiral guide tube (20) is connected to the inlet of the steam-water separator (13), a plurality of second through holes (21) are evenly arranged on the spiral guide tube (20), a single-leaf hyperboloid arc baffle (22) is arranged outside the spiral guide tube (20), and a flared opening (23) is arranged at the outlet end of the spiral guide tube (20), and the flared opening (23) is located inside the arc baffle (22).

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