High-vacuum-degree micro-differential-pressure control device for graded flash evaporation heat recovery of desulfurization slurry

Abstract

The utility model discloses a high-vacuum-degree micro-pressure-difference control device for desulfurization slurry grading flash evaporation heat recovery, and belongs to the technical field of coal-fired boiler waste heat heat supply. The system aims at solving the problems that when desulfurization slurry flash evaporation is adopted for boiler flue gas waste heat recovery, much non-condensable gas such as SO2 can escape due to heat release and condensation, the volume of a vacuum system is relatively large, and consequently the high vacuum degree is difficult to maintain by adopting a conventional vacuumizing device, a special micro-differential pressure vacuum pump is added, and the vacuum degree is reduced; extracting non-condensable gas on the liquid level of the condensed water of the last-stage heater, and sending the non-condensable gas to a front-mounted heater matched with the last-stage flash tank; when necessary, alkaline water can be sprayed to the space, where non-condensable gas is enriched, of the final-stage heater so as to comprehensively absorb SO2 and other components to reduce the partial pressure, so that the micro-differential pressure vacuum pump can stably maintain the high-vacuum state of the final-stage heater, the temperature of a concentrated slurry outlet of the final-stage flash tank is greatly reduced, and the concentration rate of the final-stage flash tank is increased. And optimal operation conditions are created for greatly reducing the exhaust gas temperature and greatly improving the waste heat recovery amount.

Description

Technical Field

[0001] The utility model relates to a high-vacuum micro-pressure difference control device for desulfurized slurry staged flash evaporation heat recovery, belonging to the technical field of waste heat heating of coal-fired boilers. Background Technique

[0002] During the heat production process of boilers, a large amount of high-temperature flue gas is discharged. Recovering the waste heat of the flue gas can not only reduce the heat loss of the boiler, but also reduce the fuel consumption and emissions of pollutants such as greenhouse gases, and improve the thermal efficiency of the boiler. In recent years, a method of using desulfurized slurry flash evaporation + absorption heat pump for waste heat recovery of flue gas has emerged, that is, the heat in the flue gas is taken out from the desulfurized slurry through a flash tank, and the flash steam is sent to the heat pump for waste heat recovery, and the return water of the heat network or other process water is heated, while the concentrated liquid returns to the desulfurized circulating water. Its advantages are: there is no need to transform the flue gas system, reducing the on-site implementation difficulty; the quality of the condensate water is good, which is convenient for recycling. However, the disadvantages are also very obvious: the flue gas temperature can usually only be reduced to 42-45°C, recovering about half of the waste heat of the flue gas, which does not belong to deep heat recovery and can only be regarded as a half-finished project. There is still a large amount of waste heat of the flue gas escaping from the flue gas in vain. Future secondary transformation is still needed to achieve deep heat recovery. The cost calculated for the unit waste heat recovery amount is relatively high, and the investment payback period is long. The fundamental reason why it cannot reduce the flue gas temperature to the 30°C level and achieve deep heat recovery is: firstly, the desulfurized slurry flash evaporation complete set of equipment is a vacuum equipment, its system integration is relatively complex, the guarantee requirements are high, and the lower the flash steam temperature, the larger the specific volume, the larger the equipment volume, and the higher the cost; secondly, a large amount of non-condensable gases such as SO2 will escape during the desulfurized slurry flash evaporation process. The flash steam is sent to the absorption heat pump, and it is difficult to evacuate during the condensation heat release process in the horizontal evaporator of the heat pump. The absolute pressure during actual operation can only be maintained at about 7-8 kPa. It is very difficult to further improve the vacuum degree with the existing equipment and conditions, and it is impossible to further improve the vacuum degree like a normal condenser. Therefore, the saturation temperature of the flash steam can only be reduced to the 38-40°C level, resulting in the flue gas temperature can only be reduced to the 40-45°C level. Content of the Utility Model

[0003] The purpose and task of the utility model are to, aiming at the current inherent technical limitations of the waste heat recovery system of the flue gas by the desulfurized slurry flash evaporation method, adopt the micro-pressure difference control technology to deeply extract non-condensable gases such as SO2 generated during the condensation heat exchange of the flash steam, and construct a brand-new technical integration system for deep recovery of flue gas by desulfurized slurry staged flash evaporation.

[0004] The specific description of the present utility model is: A high-vacuum micro-pressure difference control device for desulfurized slurry staged flash evaporation heat recovery, which consists of an original desulfurization tower 1, a desulfurized slurry staged flash evaporation subsystem 2, and a controllable vacuum condenser subsystem 3. The desulfurized slurry staged flash evaporation subsystem 2 includes N series-connected flash tanks, where N is greater than or equal to 2. The first stage is a preflash tank 21, and the Nth stage is a final flash tank 31. It is characterized in that the controllable vacuum condenser subsystem 3 includes a preheater 26, a precondensate pump 27, a final heater 36, a final condensate pump 37, an alkali addition pump 30, a vacuum pump 18, a micro-pressure difference vacuum pump 38, and connecting pipelines and components. The steam inlet of the preheater 26 is connected to the flash steam outlet of the preflash tank 21 through a preconnection pipe 25. The low-temperature water inlet of the preheater 26 is communicated with the water inlet pipe of the return water H1 from the heat network. The low-temperature water outlet of the preheater 26 is communicated with the drain pipe of the return water H2 of the heat network. The condensate outlet of the preheater 26 is connected to the inlet of the precondensate pump 27. The outlet of the precondensate pump 27 is communicated with the inlet of the washing spray layer of the preflash tank 21, the inlet of the washing spray layer of the final flash tank 31, and the outlet pipe of the pre-discharged condensate W1. The steam inlet of the final heater 36 is connected to the flash steam outlet of the final flash tank 31 through a final connection pipe 35. The low-temperature water inlet of the final heater 36 is communicated with the water inlet pipe of the low-temperature process water C1. The low-temperature water outlet of the final heater 36 is communicated with the drain pipe of the low-temperature process water C2. The internal heat exchange element of the final heater 36 and above the liquid level of the bottom hot well is a non-condensable gas disposal space, in which an alkali liquid spraying device 36a and a waterproof non-condensable gas suction device 36b are provided. A hot well liquid level measurement and control component 36c is also provided inside and outside the hot well. The upper part of the alkali liquid spraying device 36a is a region with a high content of SO2 non-condensable gas S1, and above the condensate liquid level of the hot well is a region with a low content of SO2 non-condensable gas S2. The condensate outlet of the final heater 36 is connected to the inlet of the final condensate pump 37. The outlet of the final condensate pump 37 is respectively connected to the outlet of the alkali addition pump 30 and the inlet of the alkali liquid spraying device 36a, and is communicated with the outlet pipe of the final-discharged condensate W2. The inlet of the alkali addition pump 30 is communicated with the feed pipe of the sodium hydroxide solution Na. The outlet of the waterproof non-condensable gas suction device 36b is connected to the intake port of the micro-pressure difference vacuum pump 38. The exhaust port of the micro-pressure difference vacuum pump 38 is connected to the inlet of the preconnection pipe 25 and the preheater 26 through a first switching valve 38a, and is connected to the inlet of the vacuum pump 18 and the outlet of the pre-non-condensable gas S above the condensate liquid level of the bottom hot well of the preheater 26 through a second switching valve 38b. The exhaust port of the vacuum pump 18 is connected to the original flue gas inlet pipe of the original desulfurization tower 1. Upstream of the original flue gas inlet pipe is the inlet of the original flue gas Y1 from the boiler outlet, and downstream is the inlet of the original desulfurization tower 1. The top of the original desulfurization tower 1 is the outlet of the clean flue gas Y2.

[0005] The preheater 26 and the final heater 36 respectively adopt a vertical tube heat exchange structure, with a condensate hot well provided at the bottom and a non-condensable gas discharge port provided above the liquid level of the hot well.

[0006] The vacuum pump 18 adopts a water ring vacuum pump, a water jet air ejector or a roots vacuum pump structure.

[0007] The micro differential pressure vacuum pump 38 adopts a roots vacuum pump structure or an ejector structure.

[0008] The lye spraying device 36a adopts a nozzle type empty tower structure or a packing structure.

[0009] The outlet pipes of the final stage external discharged condensate W2 are respectively communicated with the inlet of the make-up water pipe of the heat network return water H1 and / or the outlet pipe of the pre-stage external discharged condensate W1.

[0010] The beneficial effects of the present utility model are as follows.

[0011] (1) Heat is taken from the desulfurization slurry by means of staged flashing. Among them, the flash steam with lower pressure and temperature generated by the final stage flash tank is preferentially used to heat the process water at a lower temperature, such as demineralized water make-up water, heat network make-up water, low-temperature intermediate water for the first-stage preheating of the boiler inlet air, or low-temperature heat source water of an absorption heat pump, low-temperature heat source water of a compression heat pump and other low-temperature process water, etc.; the flash steam with higher temperature generated by the pre-stage flash tank can be used for the secondary heating of the above-mentioned low-temperature process water, or for heating the process water at a higher temperature such as heat network return water.

[0012] (2) The preheater 26 and the final heater 36 adopt a vertical tube bundle heat exchange structure. Although a large amount of SO2 and the like are contained in the non-condensable gas, the non-condensable gas can still be extracted by their respective vacuum pumps to maintain the required vacuum degree and the pressure of the upstream flash tank.

[0013] (3) The vacuum degree requirement for the space where the non-condensable gas is located at the lower part of the final heater 36 is higher, for example, the absolute pressure reaches the level of 2-4 kPa. The control methods and measures to achieve such a high vacuum degree include: chemically absorbing or physically absorbing components such as SO2 in the non-condensable gas by using sodium hydroxide lye solution, so as to greatly reduce the content of non-condensable gas and significantly improve the vacuum degree; on this basis, the micro differential pressure vacuum pump 38 is used to extract the remaining non-condensable gas and send it to the inlet of the heater (26) or the inlet of the vacuum pump 18, so as to greatly reduce the pressure of the non-condensable gas at the lower part of the final heater, greatly improve the vacuum degree of the final stage flash tank 31, greatly reduce the temperature of its concentrated slurry outlet, and further greatly reduce the flue gas temperature, so as to achieve the maximum recovery of flue gas waste heat.

[0014] (4) The equipment capacity and the required input power of the micro differential pressure vacuum pump 38 are much smaller than those of the conventional vacuum pumping method, reducing energy consumption, initial investment and operating costs.

[0015] (5) The condensate water of the flash steam can also be used as the make-up water for the return water of the heat network, which helps to significantly reduce the water production volume and cost of softened water. At the same time, the comprehensive recovery and utilization of the condensate water also correspondingly greatly reduces the consumption of water resources.

[0016] (6) The vacuum degrees of the flash tanks - heaters at all levels of this solution can be separately and individually adjusted in real time according to the inlet and outlet temperatures of the water to be heated for each of them and the changes in the operating conditions of the entire system, so as to better achieve system operation control, reduce system energy consumption, improve the comprehensive energy-saving benefit and economic benefit. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a schematic diagram of the system of the present utility model.

[0018] Figure 1 The numbers and names of the components in it are as follows.

[0019] Original desulfurization tower 1, desulfurization slurry staged flash subsystem 2, controllable vacuum degree condenser subsystem 3, vacuum pump 18, pre-stage flash tank 21, pre-stage connecting pipe 25, pre-stage heater 26, pre-stage condensate pump 27, alkali addition pump 30, final-stage flash tank 31, final-stage connecting pipe 35, final-stage heater 36, alkali liquid spraying device 36a, waterproof non-condensable gas suction device 36b, hot well liquid level measurement and control component 36c, final-stage condensate pump 37, micro differential pressure vacuum pump 38, first switching valve 38a, second switching valve 38b, low-temperature process water incoming water C1, low-temperature process water outgoing water C2, heat network return water incoming water H1, heat network return water outgoing water H2, pre-stage non-condensable gas S, SO2-rich non-condensable gas S1, SO2-poor non-condensable gas S2, pre-stage externally discharged condensate water W1, final-stage externally discharged condensate water W2, original flue gas Y1, clean flue gas Y2, sodium hydroxide solution Na. SPECIFIC EMBODIMENTS

[0020] Figure 1 is a schematic diagram of the system of the present utility model and an embodiment.

[0021] The specific embodiments of the present utility model are as follows. A high-vacuum micro-pressure difference control device for desulfurized slurry staged flash evaporation heat recovery consists of an original desulfurization tower 1, a desulfurized slurry staged flash evaporation subsystem 2, and a controllable vacuum condenser subsystem 3. The desulfurized slurry staged flash evaporation subsystem 2 includes N series-connected flash tanks, where N is greater than or equal to 2. The first stage is a pre-flash tank 21, and the Nth stage is a final flash tank 31. It is characterized in that the controllable vacuum condenser subsystem 3 includes a pre-heater 26, a pre-condensate pump 27, a final heater 36, a final condensate pump 37, an alkali addition pump 30, a vacuum pump 18, a micro-pressure difference vacuum pump 38, and connecting pipelines and components. The steam inlet of the pre-heater 26 is connected to the flash steam outlet of the pre-flash tank 21 through a pre-connection pipe 25. The low-temperature water inlet of the pre-heater 26 is communicated with the water inlet pipe of the return water H1 from the heat network. The low-temperature water outlet of the pre-heater 26 is communicated with the return water pipe of the return water H2 from the heat network. The condensate outlet of the pre-heater 26 is connected to the inlet of the pre-condensate pump 27. The outlet of the pre-condensate pump 27 is communicated with the washing spray layer inlet of the pre-flash tank 21, the washing spray layer inlet of the final flash tank 31, and the outlet pipe of the pre-external discharged condensate W1. The steam inlet of the final heater 36 is connected to the flash steam outlet of the final flash tank 31 through a final connection pipe 35. The low-temperature water inlet of the final heater 36 is communicated with the water inlet pipe of the low-temperature process water C1. The low-temperature water outlet of the final heater 36 is communicated with the return water pipe of the low-temperature process water C2. The internal heat exchange element of the final heater 36 and the space above the bottom hot well liquid level are for non-condensable gas disposal. An alkali liquid spraying device 36a and a waterproof non-condensable gas suction device 36b are provided therein. A hot well liquid level measurement and control component 36c is also provided inside and outside the hot well. The upper part of the alkali liquid spraying device 36a is a region with non-condensable gas S1 containing more SO2, and the region above the hot well condensate liquid level is a region with non-condensable gas S2 containing less SO2. The condensate outlet of the final heater 36 is connected to the inlet of the final condensate pump 37. The outlet of the final condensate pump 37 is respectively connected to the outlet of the alkali addition pump 30 and the inlet of the alkali liquid spraying device 36a, and is communicated with the outlet pipe of the final external discharged condensate W2. The inlet of the alkali addition pump 30 is communicated with the feed pipe of the sodium hydroxide solution Na. The outlet of the waterproof non-condensable gas suction device 36b is connected to the inlet of the micro-pressure difference vacuum pump 38. The exhaust port of the micro-pressure difference vacuum pump 38 is connected to the inlet of the pre-connection pipe 25 and the pre-heater 26 through a first switching valve 38a, and is connected to the inlet of the vacuum pump 18 and the outlet of the pre-non-condensable gas S above the bottom hot well condensate liquid level of the pre-heater 26 through a second switching valve 38b. The exhaust port of the vacuum pump 18 is connected to the original flue gas inlet pipe of the original desulfurization tower 1. The upstream of the original flue gas inlet pipe is the inlet of the original flue gas Y1 from the boiler outlet, and the downstream is the inlet of the original desulfurization tower 1. The top of the original desulfurization tower 1 is the outlet of the clean flue gas Y2.

[0022] The preheater 26 and the final heater 36 respectively adopt a vertical tube - type heat exchange structure, with a condensate hot well provided at the bottom, and a non - condensable gas discharge port provided above the liquid level of the hot well.

[0023] The vacuum pump 18 adopts a water - ring vacuum pump, a water - jet steam ejector or a Roots vacuum pump structure.

[0024] The micro - differential pressure vacuum pump 38 adopts a Roots vacuum pump structure or an ejector structure.

[0025] The lye spraying device 36a adopts a nozzle - type empty tower structure or a packing structure.

[0026] The outlet pipes of the final discharged condensate W2 are respectively communicated with the inlet of the make - up water pipe of the return water H1 of the heat network and / or the outlet pipes of the pre - discharged condensate W1.

[0027] It should be noted that based on key technologies such as multi - stage flashing of desulfurization slurry and adopting measures to comprehensively control the vacuum degree inside each heater, the present utility model proposes a complete set of new integrated systems and operation strategies for flue gas deep - heat recovery by flashing desulfurization slurry. According to this overall solution, there can be different specific implementation measures and specific implementation devices with different structures. The above - mentioned specific implementation manners are just one of them. Any other similar simple - deformation implementation manners, such as simple deformations of flash steam and heat exchangers, simple adjustments of pipelines, or simple changes in the vacuum - pumping method, etc., all fall within the protection scope of the present utility model.

Claims

1. A high vacuum micro-pressure difference control device for heat recovery of desulfurization slurry staged flash evaporation, comprising an original desulfurization tower (1), a desulfurization slurry staged flash evaporation subsystem (2) and a controllable vacuum condenser subsystem (3), wherein the desulfurization slurry staged flash evaporation subsystem (2) comprises N stages of flash tanks connected in series, wherein N is greater than or equal to 2, wherein the first stage is a pre-flash tank (21), and the Nth stage is a final flash tank (31), characterized in that: The controllable vacuum condenser subsystem (3) comprises a preheater (26), a precondensation pump (27), a final-stage heater (36), a final-stage condensation pump (37), an alkali adding pump (30), a vacuum pump (18), a micro-pressure difference vacuum pump (38) and connecting pipelines and components, wherein the steam inlet of the preheater (26) is connected to the flash steam outlet of the pre-flash tank (21) through a pre-connecting pipe (25), the low-temperature water inlet of the preheater (26) is connected to the water inlet pipe of the heat network return water (H1), the low-temperature water outlet of the preheater (26) is connected to the water return pipe of the heat network return water (H2), and the condensate outlet of the preheater (26) is connected to the inlet of the pre-condensation pump (27). The outlet of the front condensation pump (27) is connected to the washing spray layer inlet of the front flash tank (21), the washing spray layer inlet of the final flash tank (31) and the outlet pipe of the front external condensate (W1); the steam inlet of the final heater (36) is connected to the flash steam outlet of the final flash tank (31) through the final connecting pipe (35); the low-temperature water inlet of the final heater (36) is connected to the water inlet pipe of the low-temperature process water (C1); the low-temperature water outlet of the final heater (36) is connected to the water withdrawal pipe of the low-temperature process water withdrawal (C2); the internal heat exchange element of the final heater (36) and the non-condensable gas disposal space above the bottom hot well liquid level, in which an alkali solution spraying device (36a) is provided. , a waterproof non-condensable gas suction device (36b), a hot well liquid level measurement and control component (36c) is also arranged inside and outside the hot well, wherein the upper part of the alkali solution spraying device (36a) is a region containing more SO2 non-condensable gas (S1), and the region above the hot well condensate liquid level is a region containing less SO2 non-condensable gas (S2), the condensate outlet of the final heater (36) is connected to the inlet of the final condensate pump (37), the outlet of the final condensate pump (37) is respectively connected to the outlet of the alkali adding pump (30) and the inlet of the alkali solution spraying device (36a), and is communicated with the outlet pipe of the final external condensate (W2), and the inlet of the alkali adding pump (30) is communicated with the feed pipe of the sodium hydroxide solution (Na); waterproof non-condensable gas suction device (36b), a hot well liquid level measurement and control component (36c) is also arranged inside and outside the hot well, wherein the upper part of the alkali solution spraying device (36a) is a region containing more SO2 non-condensable gas (S1), and the region above the hot well condensate liquid level is a region containing less SO2 non-condensable gas (S2), the condensate outlet of the final heater (36) is connected to the inlet of the final condensate pump (37), and the outlet of the final condensate pump (37) is respectively connected to the outlet of the alkali adding pump (30) and the inlet of the alkali solution spraying device (36a), and is communicated with the outlet pipe of the final external condensate (W2), and the inlet of the alkali adding pump (30) is communicated with the feed pipe of the sodium hydroxide solution (Na); The outlet of the device (36b) is connected to the air inlet of the micro-pressure differential vacuum pump (38); the exhaust port of the micro-pressure differential vacuum pump (38) is connected to the inlet of the front connecting pipe (25) and the front heater (26) through the first switch valve (38a); and is connected to the inlet of the vacuum pump (18) and the outlet of the front non-condensable gas (S) on the condensate liquid surface of the bottom hot well of the front heater (26) through the second switch valve (38b); the exhaust port of the vacuum pump (18) is connected to the original flue gas inlet pipe of the original desulfurization tower (1); the upstream of the original flue gas inlet pipe is the inlet of the original flue gas (Y1) from the boiler outlet, the downstream is the flue gas inlet of the original desulfurization tower (1), and the top of the original desulfurization tower (1) is the outlet of the clean flue gas (Y2).

2. A high vacuum micro-pressure difference control device for desulfurization slurry graded flash heat recovery according to claim 1, characterized in that The pre-heater (26) and the final-stage heater (36) respectively adopt a vertical tube-in-tube heat exchange structure, a condensate hot well is provided at the bottom, and a non-condensable gas discharge port is provided above the hot well liquid surface.

3. A high vacuum micro-pressure difference control device for desulfurization slurry graded flash heat recovery according to claim 1, characterized in that The vacuum pump (18) adopts a water ring vacuum pump, a water jet steam extractor or a Roots vacuum pump structure.

4. A high vacuum micro-pressure difference control device for desulfurization slurry graded flash heat recovery according to claim 1, characterized in that The micro-pressure difference vacuum pump (38) adopts a Roots vacuum pump structure or an ejector structure.

5. A high vacuum micro-pressure difference control device for desulfurization slurry graded flash heat recovery according to claim 1, characterized in that The alkali solution spraying device (36a) adopts a nozzle-type empty tower structure or a filler structure.

6. A high vacuum micro-pressure difference control device for desulfurization slurry graded flash heat recovery as claimed in claim 1, characterized in that The sodium hydroxide mass concentration of the sodium hydroxide solution (Na) is in the range of 0% to 60%.

7. A high vacuum micro-pressure difference control device for desulfurization slurry graded flash heat recovery according to claim 1, characterized in that The outlet pipe of the final-stage externally discharged condensed water (W2) is respectively communicated with the inlet of the replenishment pipe of the return water (H1) of the heating network and / or the outlet pipe of the front-stage externally discharged condensed water (W1).

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