CN108706668B - A multi-mode heating steam source seawater desalination system - Google Patents

Abstract

The invention discloses a seawater desalination system of a multi-mode heating steam source, which belongs to the technical field of seawater desalination by utilizing steam turbine extraction steam. The system combines a low-temperature multi-effect distillation device with a thermal power generation system to desalinate sea water in multiple modes, and respectively utilizes the communicating pipe steam extraction of a low-pressure cylinder in a turbine with higher parameters, the steam extraction of the low-pressure cylinder with lower parameters and the exhaust steam of the low-pressure cylinder as heating steam of a sea water desalination system.

Description

A multi-mode heating steam source seawater desalination system

technical field

The invention belongs to the technical fields of steam turbine technology and seawater desalination, and in particular relates to a seawater desalination system for heating steam sources in multiple modes.

Background technique

Since the 1950s, with the emergence of the shortage of fresh water resources, seawater desalination technology has been rapidly developed and applied, and has become one of the important ways to solve the water resource crisis. Seawater desalination is a technology that uses energy to obtain fresh water resources. According to the different forms of energy in the desalination process, seawater desalination can be divided into multi-stage flash evaporation and multi-effect distillation thermal technology that mainly consumes heat energy, and technology that mainly consumes electric energy. reverse osmosis membrane technology. Among them, the low-temperature multiple-effect distillation method is one of the most energy-saving methods in seawater desalination technology. It has developed rapidly in recent years, and the scale of the device has been expanding day by day.

At present, the steam pressure used in domestic low-temperature multi-effect distillation seawater desalination devices is generally at Between, temperature at /> During this period, this part of the steam enters the seawater desalination device as a heating steam source after being reduced in temperature and pressure. However, the low-temperature multiple-effect distillation method uses high-quality steam turbine extraction as the heating steam source for seawater desalination, which will lead to high actual operating costs of seawater desalination, which greatly restricts engineering application, market promotion and market competitiveness.

The existing technology not only has the problem of high-grade energy loss in the process of reducing temperature and decompression, but also uses a single extraction steam as the sea desalination heating steam source to maximize the rational distribution of energy. There is room for energy saving, and the economic benefits of cogeneration of hydropower are not obvious enough. Patent No. CN105110400A discloses a thermal system for the comprehensive utilization of latent heat of exhaust steam of steam turbines. It uses ejectors to realize the reuse of low-pressure exhaust steam, and at the same time utilizes the latent heat resources of exhaust steam from condensers, effectively reducing the operating cost of seawater desalination systems. Moreover, there are two operating conditions of pure condensation and high back pressure in the actual operation of the generator set. Under different operating conditions, the seawater desalination system with a single extraction mode has poor energy-saving potential, while the seawater desalination system with multi-mode heating steam source and The coupling of steam turbines can achieve energy level matching and cascade utilization. This multi-mode heating steam source seawater desalination system has greater energy-saving potential and economic benefits.

In summary, the present invention selects the steam from the steam turbine with appropriate parameters as the steam source for seawater desalination, which can reduce the operating cost of seawater desalination and improve the water production efficiency of the low-temperature multi-effect distillation method; The cooperation between the heating steam source and the operation mode of the generating set can maximize the efficient use of energy quality.

Contents of the invention

The object of the present invention is to provide a seawater desalination system with multi-mode heating steam source, the system mainly includes: high-pressure cylinder, medium-pressure cylinder, low-pressure cylinder, seawater desalination TVC valve, first low-temperature multi-effect evaporator, second low-temperature multi-effect evaporator effect evaporator, the third low-temperature multi-effect evaporator, the fourth low-temperature multi-effect evaporator, the fifth low-temperature multi-effect evaporator and the desalination condenser; it is characterized in that the high-pressure cylinder 1, the medium-pressure cylinder 2, the low-pressure cylinder Cylinder 4 and generator 5 are connected sequentially; first low-temperature multiple-effect evaporator 12, second low-temperature multiple-effect evaporator 13, third low-temperature multiple-effect evaporator 14, fourth low-temperature multiple-effect evaporator 15, fifth low-temperature multiple-effect evaporator The evaporator 16 and the desalination condenser 17 are connected in sequence; the seawater outlet of the desalination condenser 17 is connected to the seawater inlet of each low-temperature multi-effect evaporator through the seawater delivery pump 18; The first control valve 8 and the first spray desuperheating device 9 communicate with the desalination TVC valve 10; the steam outlet of the second low-temperature multi-effect evaporator 13 and the outlet of the sea desalination TVC valve 10 pass through the second spray desuperheating device 11 It is connected with the first low-temperature multi-effect evaporator 12; the steam extraction port of the low-pressure cylinder 4 is connected with the first low-temperature multi-effect evaporator 12 through the second control valve 7 and the second water spray desuperheating device 11; the low vacuum exhaust of the low-pressure cylinder 4 The steam outlet is connected to the first low-temperature multiple-effect evaporator 12 through the third control valve 6 and the second water spray desuperheating device 11 .

The multi-mode heating steam source of the seawater desalination system is controlled by the first control valve 8, the second control valve 7 and the third control valve 6, and can be in the first mode, the second mode, the third mode and the fourth mode run;

In the first mode, the first control valve 8 is opened, the second control valve 7 and the third control valve 6 are closed, and the extraction steam of the medium-pressure and low-pressure cylinder communication pipe 3 is used as the heating steam of the seawater desalination system;

In the second mode, the second control valve 7 is opened, the first control valve 8 and the third control valve 6 are closed, and the extraction steam of the low-pressure cylinder 4 enters through the second control valve 7 and the second water spray desuperheating device 11 The first low-temperature multiple-effect evaporator 12 is used as a seawater desalination system to heat steam;

The third mode described is that the first control valve 8 and the second control valve 7 are opened, and the third control valve 6 is closed; The temperature device 9 enters the desalination TVC valve 10, and the extraction steam of the low-pressure cylinder 4 enters the desalination TVC valve 10 through the second control valve 7, forming a mutual cooperation between the extraction steam of the medium pressure and low pressure cylinder connecting pipe 3 and the extraction steam of the low pressure cylinder As heating steam for seawater desalination system;

The fourth mode is that the third control valve 6 is opened, the first control valve 8 and the second control valve 7 are closed, and the low-vacuum exhaust steam of the low-pressure cylinder enters the first The low-temperature multiple-effect evaporator 12 is used as a seawater desalination system to heat steam.

The steam extraction pressure of the medium-pressure and low-pressure cylinder connecting pipes (3) is greater than 0.3MPa.a.

The saturated steam temperature at the outlet of the second water spray desuperheating device (11) is The steam pressure that enters the second spray desuperheating device (11) is

When the described seawater desalination system operates in the fourth mode, the low-vacuum exhaust steam of the low-pressure cylinder 4 is used as the heating steam of the seawater desalination system, and its pressure is

The beneficial effect of the present invention is that the present invention adopts the combination of the low-temperature multi-effect distillation device and the thermal power generation system, respectively utilizes steam extraction from the communication pipe of the middle and low-pressure cylinder of the steam turbine with higher parameters, extraction steam from the low-pressure cylinder with lower parameters, and exhaust steam from the low-pressure cylinder as The seawater desalination system heats the steam, and at the same time uses the medium and low pressure cylinder connecting pipe to extract steam and the low pressure cylinder to cooperate with each other to drive the seawater desalination system. By selecting a steam turbine with appropriate parameters to drive the seawater desalination system, the combination of high and low parameter steam can be achieved, and fresh water resources can be produced at low cost while considering the operating status of the generator set. The energy saving effect and economic benefits of hydropower cogeneration are remarkable; Efficient use of quality.

Description of drawings

Fig. 1 is a schematic diagram of a seawater desalination system with multi-mode heating steam sources.

Detailed ways

The present invention provides a multi-mode heating steam source seawater desalination system, the system mainly includes: a high-pressure cylinder, a medium-pressure cylinder, a low-pressure cylinder, a desalination TVC valve, a first low-temperature multi-effect evaporator, and a second low-temperature multi-effect evaporator , the third low-temperature multi-effect evaporator, the fourth low-temperature multi-effect evaporator, the fifth low-temperature multi-effect evaporator and the desalination condenser; the present invention is controlled by the first control valve 8, the second control valve 7 and the third The control of the valve 6 can operate in the first mode, the second mode, the third mode and the fourth mode; the present invention will be explained in detail below with reference to the accompanying drawings.

Figure 1 is a schematic diagram of a seawater desalination system with multi-mode heating steam sources. In the figure, the high-pressure cylinder 1, the medium-pressure cylinder 2, the low-pressure cylinder 4 and the generator 5 are connected sequentially; the first low-temperature multiple-effect evaporator 12, the second low-temperature multiple-effect evaporator 13, the third low-temperature multiple-effect evaporator 14, The four low-temperature multi-effect evaporators 15, the fifth low-temperature multi-effect evaporator 16 and the desalination condenser 17 are sequentially connected; the seawater outlet of the desalination condenser 17 is connected to the seawater of each low-temperature multi-effect evaporator through a seawater delivery pump 18 The inlet; the steam extraction end of the medium-pressure and low-pressure cylinder communication pipe 3 communicates with the desalination TVC valve 10 through the first control valve 8 and the first water spray desuperheating device 9; the steam outlet of the second low-temperature multi-effect evaporator 13, the desalination The outlet of the TVC valve 10 is connected to the first low-temperature multi-effect evaporator 12 through the second water spray desuperheating device 11; effect evaporator 12; the low-vacuum exhaust steam outlet of the low-pressure cylinder 4 is connected to the first low-temperature multiple-effect evaporator 12 through the third control valve 6 and the second water spray desuperheating device 11 . Among them, the steam extraction pressure of the connecting pipe 3 of the medium-pressure and low-pressure cylinders is greater than 0.3MPa.a, and the temperature of the saturated steam at the outlet of the second water spray desuperheating device 11 is The steam pressure that enters the second spray desuperheating device 11 is

When the described seawater desalination system operates in the fourth mode, the low-vacuum exhaust steam of the low-pressure cylinder 4 is used as the heating steam of the seawater desalination system, and its pressure is

The seawater desalination system of the multi-mode heating steam source can operate in the first mode, the second mode, the third mode and the fourth mode through the control of the first control valve 8, the second control valve 7 and the third control valve 6 .

Taking a 630MW extraction condensing generator set as an example to extract steam to drive a 25,000-ton/day low-temperature multi-effect seawater desalination process, the working principle is as follows:

The first mode is running, the first control valve 8 is opened, the second control valve 7 and the third control valve 6 are closed, and the steam extraction flow rate of the medium-pressure and low-pressure cylinder connecting pipe 3 of the steam turbine is 70t/h, and the pressure is 0.55MPa.a , enter the desalination TVC valve 10 after passing through the first water spray desuperheating device 9, and the sea desalination TVC valve 10 draws the evaporation steam of the seawater desalination system, and its outlet steam pressure is 25kPa.a, after passing through the second water spray desuperheating device 11 The temperature is lowered to 65°C as the heating steam for the desalination system.

The second mode is running, the second control valve 7 is opened, the first control valve 8 and the third control valve 6 are closed, and the extraction steam flow rate of the low-pressure cylinder 4 is 120t/h, and the extraction steam passes through the second control valve 7 and the second injection The water desuperheating device 11 enters the first low-temperature multiple-effect evaporator 12 to heat steam as a seawater desalination system.

The third mode runs, the first control valve 8 and the second control valve 7 are opened, and the third control valve 6 is closed; The extraction steam flow rate of cylinder 4 is 20t/h, the pressure is 45kPa.a, the extraction steam enters the desalination TVC valve 10 through the first control valve 8 and the first water spray desuperheating device 9, and the extraction steam of the low-pressure cylinder 4 passes through the second The control valve 7 enters the seawater desalination TVC valve 10 to form the extraction steam of the medium pressure and low pressure cylinder communication pipe 3 and the extraction steam of the low pressure cylinder to cooperate with each other as heating steam for the seawater desalination system.

The fourth mode operates, when the generator set enters the high back pressure operation mode, the seawater desalination system operates in the fourth mode, the third control valve 6 is opened, the first control valve 8 and the second control valve 7 are closed, and the low vacuum of the low pressure cylinder The steam flow rate is 120t/h, the pressure is 35kPa.a, after being cooled by the third control valve 6 and the second water spray desuperheating device 11, it enters the first low-temperature multiple-effect evaporator 12, and is used as heating steam for the seawater desalination system.

The heating steam of the seawater desalination system releases the latent heat of vaporization in the heat exchange tube of the first low-temperature multi-effect evaporator 12 and then becomes condensed water to be discharged; The second low-temperature multiple-effect evaporator 13 steam inlet is used as the heating steam of the second low-temperature multiple-effect evaporator 13; the unevaporated seawater outside the heat exchange tube of the first low-temperature multiple-effect evaporator 12 is concentrated brine from the first low-temperature multiple-effect evaporator 12 The outlet enters the second low-temperature multiple-effect evaporator 13 concentrated brine inlet.

The heating steam of the second low-temperature multiple-effect evaporator 13 becomes distilled water after releasing the latent heat of vaporization in the second low-temperature multiple-effect evaporator 13 heat exchange tubes, and the distilled water of the second low-temperature multiple-effect evaporator 13 is obtained from the second low-temperature multiple-effect evaporator 13. The distilled water outlet enters the distilled water inlet of the third low-temperature multiple-effect evaporator 14; part of the seawater outside the second low-temperature multiple-effect evaporator 13 heat exchange tubes absorbs heat to generate secondary steam, which enters the third low-temperature multiple-effect evaporator 14 steam inlet as the second low-temperature multiple-effect evaporator. The heating steam of the third low-temperature multiple-effect evaporator 14; the unevaporated seawater outside the heat exchange tube of the second low-temperature multiple-effect evaporator 13 enters the third low-temperature multiple-effect evaporator 14 concentrated brine from the second low-temperature multiple-effect evaporator 13 concentrated brine outlet Entrance.

The heating steam of the third low-temperature multiple-effect evaporator 14 becomes distilled water after releasing the latent heat of vaporization in the third low-temperature multiple-effect evaporator 14 heat exchange tubes, and the distilled water of the third low-temperature multiple-effect evaporator 14 is obtained from the third low-temperature multiple-effect evaporator 14. The distilled water outlet enters the distilled water inlet of the fourth low-temperature multiple-effect evaporator 15; the seawater outside the heat exchange tube of the third low-temperature multiple-effect evaporator 14 absorbs heat to generate secondary steam, and enters the steam inlet of the fourth low-temperature multiple-effect evaporator 15 as the first The heating steam of four low-temperature multiple-effect evaporators 15; the unevaporated seawater outside the heat exchange tube of the third low-temperature multiple-effect evaporator 14 enters the fourth low-temperature multiple-effect evaporator 15 concentrated brine from the third low-temperature multiple-effect evaporator 14 concentrated brine outlet Entrance.

The heating steam of the fourth low-temperature multiple-effect evaporator 15 becomes distilled water after releasing the latent heat of vaporization in the heat exchange tube of the fourth low-temperature multiple-effect evaporator 15, and the distilled water of the fourth low-temperature multiple-effect evaporator 15 is obtained from the fourth low-temperature multiple-effect evaporator 15. The distilled water outlet enters the distilled water inlet of the fifth low-temperature multiple-effect evaporator 16; part of the seawater outside the heat exchange tube of the fourth low-temperature multiple-effect evaporator 15 absorbs heat to generate secondary steam, which enters the fifth low-temperature multiple-effect evaporator 16 steam inlet, as the first The heating steam of the fifth low-temperature multiple-effect evaporator 16; the unevaporated seawater outside the heat exchange tube of the fourth low-temperature multiple-effect evaporator 15 enters the fifth low-temperature multiple-effect evaporator 16 concentrated brine from the concentrated brine outlet of the fourth low-temperature multiple-effect evaporator 15 Entrance.

The heating steam of the fifth low-temperature multiple-effect evaporator 16 releases the latent heat of vaporization in the heat exchange tube of the fifth low-temperature multiple-effect evaporator 16 and becomes distilled water, and part of the seawater outside the heat exchange tube of the fifth low-temperature multiple-effect evaporator 16 absorbs heat to generate secondary steam Enter the desalination condenser 17, and enter the fifth low-temperature multi-effect evaporator 16 distilled water inlet after condensation, and the distilled water of each low-temperature multi-effect evaporator is collected to the fifth low-temperature multi-effect evaporator 16 distilled water outlet and discharged; the fifth low-temperature multi-effect evaporator 16 distilled water outlet The unevaporated seawater outside the heat exchange tubes of the evaporator 16 goes to the concentrated brine outlet of the fifth low-temperature multiple-effect evaporator 16, and the concentrated brine from each low-temperature multiple-effect evaporator is collected to the fifth low-temperature multiple-effect evaporator 16 concentrated brine outlet for discharge.

Claims (4)

1. A seawater desalination system with a multi-mode heating vapor source, the system mainly comprising: the system comprises a high-pressure cylinder (1), a medium-pressure cylinder (2), a low-pressure cylinder (4), a sea light TVC valve (10), a first low-temperature multi-effect evaporator (12), a second low-temperature multi-effect evaporator (13), a third low-temperature multi-effect evaporator (14), a fourth low-temperature multi-effect evaporator (15), a fifth low-temperature multi-effect evaporator (16) and a sea light condenser (17); the high-pressure cylinder (1), the medium-pressure cylinder (2), the low-pressure cylinder (4) and the generator (5) are sequentially connected; the first low-temperature multi-effect evaporator (12), the second low-temperature multi-effect evaporator (13), the third low-temperature multi-effect evaporator (14), the fourth low-temperature multi-effect evaporator (15), the fifth low-temperature multi-effect evaporator (16) and the sea condenser (17) are sequentially connected; the sea water outlet of the sea water condenser (17) is connected to the sea water inlet of each low-temperature multi-effect evaporator through a sea water delivery pump (18); the steam extraction end of the medium-pressure and low-pressure cylinder communicating pipe (3) is communicated with a sea water TVC valve (10) through a first control valve (8) and a first water spray temperature reducing device (9); the steam outlet of the second low-temperature multi-effect evaporator (13) and the outlet of the sea-state TVC valve (10) are connected with the first low-temperature multi-effect evaporator (12) through a second water spray attemperator (11); the steam extraction port of the low-pressure cylinder (4) is connected with a first low-temperature multi-effect evaporator (12) through a second control valve (7) and a second water spray attemperator (11); the low-vacuum exhaust steam outlet of the low-pressure cylinder (4) is connected with a first low-temperature multi-effect evaporator (12) through a third control valve (6) and a second water spraying and temperature reducing device (11); it is characterized in that the method comprises the steps of,

the multi-mode heating steam source of the sea water desalination system can operate in a first mode, a second mode, a third mode and a fourth mode by controlling a first control valve (8), a second control valve (7) and a third control valve (6);

the first mode is that a first control valve (8) is opened, a second control valve (7) and a third control valve (6) are closed, and the extracted steam of a medium-pressure and low-pressure cylinder communicating pipe (3) enters a sea water TVC valve (10) through the first control valve (8) and a first water spraying and temperature reducing device (9) to serve as heating steam of a sea water desalination system;

the second mode is that a second control valve (7) is opened, a first control valve (8) and a third control valve (6) are closed, and the extracted steam of the low-pressure cylinder (4) enters a first low-temperature multi-effect evaporator (12) through the second control valve (7) and a second water spraying and temperature reducing device (11) to serve as heating steam of a sea water desalination system;

the third mode is that a first control valve (8), a second control valve (7) is opened, and a third control valve (6) is closed; the extraction steam of the medium-pressure and low-pressure cylinder communicating pipe (3) enters the sea-water TVC valve (10) through the first control valve (8) and the first water spray attemperator (9), and the extraction steam of the low-pressure cylinder (4) enters the sea-water TVC valve (10) through the second control valve (7), so that the extraction steam of the medium-pressure and low-pressure cylinder communicating pipe (3) and the extraction steam of the low-pressure cylinder (4) are mutually matched to be used as heating steam of the sea water desalination system;

the fourth mode is that a third control valve (6) is opened, a first control valve (8) and a second control valve (7) are closed, and low-vacuum exhaust steam of the low-pressure cylinder (4) enters a first low-temperature multi-effect evaporator (12) through the third control valve (6) and a second water spraying and temperature reducing device (11) to serve as heating steam of the sea water desalination system.

2. The seawater desalination system of a multi-mode heating vapor source according to claim 1, wherein the vapor extraction pressure of the medium-pressure and low-pressure cylinder communicating pipe (3) is more than 0.3mpa.

3. A seawater desalination system with multi-mode heating gas source according to claim 1, wherein the saturated steam temperature at the outlet of the second spray attemperator (11) isThe steam pressure entering the second spray attemperator (11) is +>

4. The seawater desalination system of claim 1, wherein when the seawater desalination system is operated in the fourth mode, low vacuum exhaust steam of the low pressure cylinder (4) is used as heating steam of the seawater desalination system, and the pressure is the same as the pressure of the heating steam