Vacuum degree micro pressure difference control method and device for flash evaporation deep heat recovery of desulfurization slurry

Abstract

The invention discloses a vacuum degree micro pressure difference control method and device for desulfurization slurry flash evaporation deep heat recovery, and belongs to the technical field of coal-fired boiler and kiln 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; an alkali liquor spraying device is arranged inside or outside the heater to absorb and remove SO2 and other components so as to reduce the partial pressure and the total amount of non-condensable gas, a micro-differential pressure vacuum pump and a conventional vacuum pump are adopted to stably maintain the vacuum degree required by each stage of flash evaporation tank, the temperature of a concentrated slurry outlet of the final stage of flash evaporation tank is greatly reduced, and the concentration effect of the final stage of flash evaporation tank is improved. 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 invention relates to a vacuum micro-pressure difference control method and device for flash evaporation deep heat recovery of desulfurized slurry, belonging to the technical field of waste heat heating of coal-fired boilers and kilns. Background Art

[0002] Coal-fired boilers, sintering machines in steel plants and industrial kilns are accompanied by a large amount of high-temperature flue gas emissions during the heat production process. Recovering the waste heat from flue gas can not only reduce boiler heat loss, but also reduce fuel consumption and greenhouse gas and other pollutant emissions, and improve the thermal efficiency of boilers. Therefore, the development of flue gas waste heat recovery technology is an important way to help achieve the "dual carbon" strategic goal. In recent years, there has been a method of using desulfurization slurry flash evaporation + absorption heat pump to recover flue gas waste heat, that is, to remove the heat in the flue gas from the desulfurization slurry through the flash tank, and send the flash steam to the heat pump for waste heat recovery, and heat the heat network return water or other process water, while the concentrated liquid returns to the desulfurization circulating water. Its advantages are: no need to modify the flue gas system, reducing the difficulty of on-site implementation; the condensate has good water quality and is easy to recycle. But the disadvantages are also very obvious: the flue gas temperature can usually only be reduced to 42-45°C, and about half of the flue gas waste heat is recovered. It does not belong to deep heat recovery and can only be regarded as a half-way project. There is still a lot of flue gas waste heat running away from the flue gas in vain. In the future, secondary transformation will be needed to achieve deep heat recovery.

[0003] The cost of unit waste heat recovery of the flash evaporation heat recovery system of desulfurization slurry is relatively high, and the investment recovery period is long. The fundamental reason why it cannot reduce the flue gas temperature to 30℃ and achieve deep heat recovery is: first, the desulfurization slurry flash evaporation equipment is a vacuum equipment, and its system integration is relatively complex and the guarantee requirements are high. The lower the flash steam temperature, the larger the specific volume, and the larger the equipment volume, the higher the cost; second, more non-condensable gases such as SO2 will escape during the flash evaporation of desulfurization slurry. The flash steam is sent to the absorption heat pump, and it is difficult to evacuate the heat during the condensation and heat release process in the horizontal evaporator of the heat pump. The absolute pressure during actual operation can only be maintained at about 7-8kPa. It is difficult to continue to increase the vacuum degree with the existing equipment and conditions, and it is impossible to further increase the vacuum degree like the usual condenser. Therefore, the saturated temperature of the flash steam can only be reduced to 38-40℃, resulting in the flue gas temperature can only be reduced to 40-45℃. Summary of the invention

[0004] The purpose and task of the present invention is to address the inherent technical limitations of the flue gas waste heat recovery system of the above-mentioned desulfurization slurry flash evaporation method, adopt micro-pressure difference control technology to achieve the deep extraction of associated non-condensable gases such as SO2 during flash steam condensation heat exchange, and construct a new technical integrated system for deep recovery of flue gas by desulfurization slurry graded flash evaporation.

[0005] The specific description of the present invention is: a vacuum micro-pressure difference control device for deep heat recovery of desulfurization slurry flash evaporation is composed of three parts: an original desulfurization tower 1, a desulfurization slurry graded flash evaporation subsystem 2 and a controllable vacuum condenser subsystem 3. The desulfurization slurry graded flash evaporation subsystem 2 includes N stages of flash tanks 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. It is characterized in that the controllable vacuum condenser subsystem 3 includes N stages of flash steam heaters, wherein N is greater than or equal to 2, wherein the first stage is a pre-heater 26, and the Nth stage is a final heater 36. The controllable vacuum condenser subsystem 3 also includes a pre-condensation pump 27, a final condensation pump 37, an alkali addition pump 30, a conventional vacuum pump 18, a micro-pressure difference vacuum The air pump 38 and connecting pipelines and components, wherein the steam inlet of the pre-heater 26 is connected to the flash steam outlet of the pre-flash tank 21 through the pre-connecting pipe 25, the low-temperature water inlet of the pre-heater 26 is communicated with the water inlet pipe of the heat network return water H1, the low-temperature water outlet of the pre-heater 26 is communicated with the return water pipe of the heat network return water H2, 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-exhaust condensate W1; the steam inlet of the final-stage heater 36 is connected to the flash steam outlet of the final-stage flash tank 31 through the final-stage connecting pipe 35, and the final-stage heater 3 The low-temperature water inlet of 6 is communicated with the water inlet pipe of the low-temperature process water C1, the low-temperature water outlet of the final-stage heater 36 is communicated with the water withdrawal pipe of the low-temperature process water withdrawal C2, the internal heat exchange element of the final-stage heater 36 and the non-condensable gas disposal space above the bottom hot well liquid level are provided, wherein an alkali solution spraying device 36a and a waterproof non-condensable gas suction device 36b are provided, and a hot well liquid level measurement and control component 36c and a condensate mixing flow regulating valve 36d are also provided 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-stage heater 36 is connected to the inlet of the final-stage condensate pump 37, and the outlet of the final-stage condensate pump 37 is connected to the outlet of the final-stage condensate pump 37. The outlet 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 stage 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 waterproof non-condensable gas suction device 36b is connected to the air inlet of the micro-pressure difference vacuum pump 38, the exhaust port of the micro-pressure difference vacuum pump 38 is communicated with the inlet of the conventional vacuum pump 18 and the outlet of the pre-condensable gas S on the condensate liquid surface of the bottom hot well of the pre-heater 26, and the exhaust port of the conventional vacuum pump 18 is communicated with the original flue gas inlet pipe 2 of the original desulfurization tower 1; the upstream of the original flue gas inlet pipe 2 is the inlet of the original flue gas Y1 from the boiler outlet, the downstream is the smoke 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.

[0006] The control method of the vacuum micro-pressure difference control device is as follows: I. When the inlet temperature of the low-temperature process water C1 is less than 30°C, the final condensate pump 37 maintains the hot well liquid level at the set value by adjusting the condensate outlet flow rate according to the liquid level signal measured by the hot well liquid level measurement and control component 36c; the alkali pump 30 is started and the condensate mixing flow regulating valve 36d adjusts the flow rate of alkaline condensate mixed with the sodium hydroxide solution Na by adjusting the flow rate of the sodium hydroxide solution Na, and the alkaline condensate returns to the alkali solution spraying device 36a for spraying and contacts with the non-condensable gas S1 containing more SO2 and reacts and absorbs SO2 to form NaSO3 and dissolve in the condensate of the lower hot well. The pH value of the condensate operates in the range of 7 to 9, and the volume flow rate and pressure of the residual non-condensable gas are greatly reduced to become the non-condensable gas S2 containing less SO2, which is then pumped out by the micro-pressure difference vacuum pump 38, and after mixing with the front non-condensable gas S, it is pumped out by the conventional vacuum pump 18 and sent to the smoke inlet of the original desulfurization tower 1; II. When the inlet temperature of the low-temperature process water C1 is greater than or equal to 30°C and less than or equal to the inlet temperature of the heat network return water H1, the final condensate pump 37 maintains the hot well liquid level at the set value by adjusting the condensate outlet flow rate according to the liquid level signal measured by the hot well liquid level measurement and control component 36c; the alkali pump 30 is turned off, the micro-pressure difference vacuum pump 38 is running, and the non-condensable gas at the outlet of the micro-pressure difference vacuum pump 38 is mixed with the front non-condensable gas S and then extracted by the conventional vacuum pump 18 and sent to the smoke inlet of the original desulfurization tower 1; III. When the inlet temperature of the low-temperature process water C1 is greater than the inlet temperature of the heat network return water H1, the final condensate pump 37 maintains the hot well liquid level at the set value by adjusting the condensate outlet flow rate according to the liquid level signal measured by the hot well liquid level measurement and control component 36c; the alkali addition pump 30 is turned off, the micro-pressure difference vacuum pump 38 is stopped, and the non-condensable gas flowing through the micro-pressure difference vacuum pump 38 is mixed with the front non-condensable gas S and then extracted by the conventional vacuum pump 18 and sent to the smoke inlet of the original desulfurization tower 1.

[0007] N-stage series flash tanks and N-stage flash steam heaters are arranged as an integrated slurry multi-stage flash evaporation waste heat recovery tank body 20, wherein the interior is divided into two parts, a flash evaporation zone 20a and a condensation heat exchange zone 20b, which are separated by a partition in the middle, wherein a front flow port 25a is provided on the partition between the flash steam outlet of the front flash tank 21 and the steam inlet of the front heater 26, and a final flow port 35a is provided on the partition between the flash steam outlet of the final flash tank 31 and the steam inlet of the final heater 36; among the components of the vacuum micro-pressure difference control device, an alkali solution spraying device 36a, a waterproof non-condensable gas suction device 36b, and a hot well liquid level measurement and control component 36c are arranged inside the tank body or on the tower body of the slurry multi-stage flash evaporation waste heat recovery tank body 20; the slurry multi-stage flash evaporation waste heat recovery tank body 20 adopts a cylindrical or square structure, and adopts a vertical or horizontal structure.

[0008] The pre-heater 26 and the final stage heater 36 respectively adopt a vertical shell-and-tube heat exchange structure or a horizontal transverse shell-and-tube heat exchange structure.

[0009] The conventional vacuum pump 18 adopts a water ring vacuum pump, a water jet vacuum pump or a Roots vacuum pump structure.

[0010] The micro-pressure differential vacuum pump 38 adopts a Roots vacuum pump structure or an ejector structure.

[0011] The alkali solution spraying device 36a adopts a nozzle type empty tower structure or a packing structure.

[0012] An alkali liquid spraying device 36a consistent with the final-stage heater 36 is arranged in the space where the pre-non-condensable gas S is located on the condensate water surface of the bottom hot well of the pre-heater 26, wherein the feed port of the alkali liquid spraying device 36a is also connected to the outlet of the alkali adding pump 30; the pre-heater 26 and the final-stage heater 36 can also be separately arranged or share an external high-vacuum desulfurization tank 39 containing the alkali liquid spraying device 36a, the air inlet of the high-vacuum desulfurization tank 39 is connected to the non-condensable gas outlet of the final-stage heater 36 and / or the pre-heater 26, the air outlet of the high-vacuum desulfurization tank 39 is connected to the inlet of the micro-pressure difference vacuum pump 38 and / or the conventional vacuum pump 18, the feed port of the alkali liquid spraying device 36a in the high-vacuum desulfurization tank 36e is connected to the outlet of the alkali adding pump 30, and the discharge port of the high-vacuum desulfurization tank 39 is connected to the outlet pipe of the final-stage external condensate W2.

[0013] The mass concentration range of sodium hydroxide in the sodium hydroxide solution Na is 0% to 60%.

[0014] The outlet pipe of the final-stage externally discharged condensed water W2 is respectively communicated with the inlet of the replenishment pipe of the heat network return water H1 and / or the outlet pipe of the front-stage externally discharged condensed water W1.

[0015] The beneficial effects of the present invention are as follows.

[0016] (1) Heat is extracted from the desulfurized slurry by staged flash evaporation, wherein the flash steam with lower pressure and temperature produced by the final flash tank is preferentially used to heat process water with lower temperature, such as demineralized water makeup water, heat network makeup water, low-temperature intermediate water for first-stage preheating of boiler inlet air, or low-temperature heat source water for absorption heat pumps, low-temperature heat source water for compression heat pumps and other low-temperature process water; the flash steam with higher temperature produced by the pre-flash tank can be used for secondary heating of the above-mentioned low-temperature process water, or for heating process water with higher temperature such as heat network return water.

[0017] (2) The preheater 26 and the final heater 36 adopt a vertical tube bundle heat exchange structure. Although the non-condensable gas contains a large amount of SO2, etc., 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.

[0018] (3) The vacuum degree of the space where the non-condensable gas is located below the final heater 36 is required to be higher, for example, the absolute pressure reaches 2 to 4 kPa. The control methods and measures to achieve such a high vacuum degree include: using sodium hydroxide alkaline solution to chemically or physically absorb SO2 and other components in the non-condensable gas, thereby greatly reducing the non-condensable gas content and significantly improving the vacuum degree; on this basis, using a micro-pressure difference vacuum pump 38 to extract the remaining non-condensable gas and send it to the inlet of the heater (26) or the inlet of the conventional vacuum pump 18, thereby greatly reducing the non-condensable gas pressure at the bottom of the final heater, greatly improving the vacuum degree of the final flash tank 31, and greatly reducing the concentrated slurry outlet temperature, thereby greatly reducing the flue gas temperature and realizing the maximum recovery of flue gas waste heat.

[0019] (4) The equipment capacity and required input power of the micro-pressure differential vacuum pump 38 are much smaller than those of conventional vacuum extraction methods, which reduces energy consumption, initial investment and operating costs.

[0020] (5) Different vacuum control strategies are adopted according to the different low-temperature water inlet temperatures of the final heater 36. When the temperature is low and the vacuum requirement is very high, the alkali solution spraying to absorb SO2 and the micro-pressure differential vacuum pump are all put into operation, and the high vacuum operation mode is adopted, which can greatly reduce the outlet temperature of the desulfurization slurry and the flue gas temperature and increase the waste heat recovery. However, if the low-temperature water inlet temperature is high, the vacuum degree does not need to be too high. At this time, the alkali solution spraying can be stopped to save resources and operating costs. If the low-temperature water inlet temperature continues to rise, there is no need to put the micro-pressure differential vacuum pump 38 into operation to save power consumption and other operation and maintenance costs.

[0021] (6) The condensate from flash steam can also be used as replenishment water for the heat network return water, which helps to significantly reduce the amount of softened water produced and its cost. At the same time, the comprehensive recycling of condensate can also significantly reduce the consumption of water resources accordingly.

[0022] (7) The vacuum degree of each flash tank-heater in this scheme can be adjusted separately and in real time according to the changes in the inlet and outlet temperatures of the heated water and the operating conditions of the entire system, so as to better realize system operation control, reduce system energy consumption, and improve comprehensive energy-saving and economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 , 2 It is a system schematic diagram of the present invention.

[0024] Figure 1 , 2 The part numbers and names are as follows.

[0025] Original desulfurization tower 1, desulfurization slurry graded flash evaporation subsystem 2, controllable vacuum condenser subsystem 3, conventional vacuum pump 18, slurry multi-stage flash evaporation waste heat recovery tank 20, flash evaporation zone 20a, condensation heat exchange zone 20b, front flash tank 21, front connecting pipe 25, front flow port 25a, front heater 26, front condensation pump 27, alkali pump 30, final flash tank 31, final connecting pipe 35, final flow port 35a, final heater 36, alkali solution spraying device 36a, waterproof non-condensable gas suction device 36b, hot well liquid level measurement and control component 36c, condensate mixed water flow regulating valve 36d, final stage condensate pump 37, micro-pressure difference vacuum pump 38, high vacuum desulfurization tank 39, low-temperature process water inlet C1, low-temperature process water return water C2, heating network return water inlet H1, heating network return water return water H2, sodium hydroxide solution Na, front non-condensable gas S, SO2-rich non-condensable gas S1, SO2-rich non-condensable gas S2, front-stage external condensate W1, final stage external condensate W2, original flue gas Y1, clean flue gas Y2. DETAILED DESCRIPTION

[0026] Figure 1 , 2 It is a system schematic diagram and embodiment of the present invention.

[0027] The specific embodiments of the present invention are as follows. The specific description of the present invention is: the vacuum micro-pressure difference control device for deep heat recovery of desulfurization slurry flash evaporation is composed of three parts: the original desulfurization tower 1, the desulfurization slurry graded flash evaporation subsystem 2 and the controllable vacuum condenser subsystem 3. The desulfurization slurry graded flash evaporation subsystem 2 includes N stages of flash tanks 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 includes N stages of flash steam heaters, wherein N is greater than or equal to 2, wherein the first stage is a pre-heater 26, and the Nth stage is a final heater 36, and the controllable vacuum condenser subsystem 3 also includes a pre-condensation pump 27, a final condensation pump 37, an alkali pump 30, a conventional vacuum pump 18, a micro-pressure difference vacuum condenser subsystem 31, and a pre-condensation pump 27, a final condensation pump 37, an alkali pump 30, a conventional vacuum pump 18, a micro-pressure difference vacuum condenser subsystem 31, and a micro-pressure difference vacuum condenser subsystem 3. The air pump 38 and connecting pipelines and components, wherein the steam inlet of the pre-heater 26 is connected to the flash steam outlet of the pre-flash tank 21 through the pre-connecting pipe 25, the low-temperature water inlet of the pre-heater 26 is communicated with the water inlet pipe of the heat network return water H1, the low-temperature water outlet of the pre-heater 26 is communicated with the return water pipe of the heat network return water H2, 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-exhaust condensate W1; the steam inlet of the final-stage heater 36 is connected to the flash steam outlet of the final-stage flash tank 31 through the final-stage connecting pipe 35, and the final-stage heater 3 The low-temperature water inlet of 6 is communicated with the water inlet pipe of the low-temperature process water C1, the low-temperature water outlet of the final-stage heater 36 is communicated with the water withdrawal pipe of the low-temperature process water withdrawal C2, the internal heat exchange element of the final-stage heater 36 and the non-condensable gas disposal space above the bottom hot well liquid level are provided, wherein an alkali solution spraying device 36a and a waterproof non-condensable gas suction device 36b are provided, and a hot well liquid level measurement and control component 36c and a condensate mixing flow regulating valve 36d are also provided 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-stage heater 36 is connected to the inlet of the final-stage condensate pump 37, and the outlet of the final-stage condensate pump 37 is connected to the outlet of the final-stage condensate pump 37. The outlet 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 stage 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 waterproof non-condensable gas suction device 36b is connected to the air inlet of the micro-pressure difference vacuum pump 38, the exhaust port of the micro-pressure difference vacuum pump 38 is communicated with the inlet of the conventional vacuum pump 18 and the outlet of the pre-condensable gas S on the condensate liquid surface of the bottom hot well of the pre-heater 26, and the exhaust port of the conventional vacuum pump 18 is communicated with the original flue gas inlet pipe 2 of the original desulfurization tower 1; the upstream of the original flue gas inlet pipe 2 is the inlet of the original flue gas Y1 from the boiler outlet, the downstream is the smoke 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.

[0028] The control method of the vacuum micro-pressure difference control device is as follows: I. When the inlet temperature of the low-temperature process water C1 is less than 30°C, the final condensate pump 37 maintains the hot well liquid level at the set value by adjusting the condensate outlet flow rate according to the liquid level signal measured by the hot well liquid level measurement and control component 36c; the alkali pump 30 is started and the condensate mixing flow regulating valve 36d adjusts the flow rate of alkaline condensate mixed with the sodium hydroxide solution Na by adjusting the flow rate of the sodium hydroxide solution Na, and the alkaline condensate returns to the alkali solution spraying device 36a for spraying and contacts with the non-condensable gas S1 containing more SO2 and reacts and absorbs SO2 to form NaSO3 and dissolve in the condensate of the lower hot well. The pH value of the condensate operates in the range of 7 to 9, and the volume flow rate and pressure of the residual non-condensable gas are greatly reduced to become the non-condensable gas S2 containing less SO2, which is then pumped out by the micro-pressure difference vacuum pump 38, and after mixing with the front non-condensable gas S, it is pumped out by the conventional vacuum pump 18 and sent to the smoke inlet of the original desulfurization tower 1; II. When the inlet temperature of the low-temperature process water C1 is greater than or equal to 30°C and less than or equal to the inlet temperature of the heat network return water H1, the final condensate pump 37 maintains the hot well liquid level at the set value by adjusting the condensate outlet flow rate according to the liquid level signal measured by the hot well liquid level measurement and control component 36c; the alkali pump 30 is turned off, the micro-pressure difference vacuum pump 38 is running, and the non-condensable gas at the outlet of the micro-pressure difference vacuum pump 38 is mixed with the front non-condensable gas S and then extracted by the conventional vacuum pump 18 and sent to the smoke inlet of the original desulfurization tower 1; III. When the inlet temperature of the low-temperature process water C1 is greater than the inlet temperature of the heat network return water H1, the final condensate pump 37 maintains the hot well liquid level at the set value by adjusting the condensate outlet flow rate according to the liquid level signal measured by the hot well liquid level measurement and control component 36c; the alkali addition pump 30 is turned off, the micro-pressure difference vacuum pump 38 is stopped, and the non-condensable gas flowing through the micro-pressure difference vacuum pump 38 is mixed with the front non-condensable gas S and then extracted by the conventional vacuum pump 18 and sent to the smoke inlet of the original desulfurization tower 1.

[0029] N-stage series flash tanks and N-stage flash steam heaters are arranged as an integrated slurry multi-stage flash evaporation waste heat recovery tank body 20, wherein the interior is divided into two parts, a flash evaporation zone 20a and a condensation heat exchange zone 20b, which are separated by a partition in the middle, wherein a front flow port 25a is provided on the partition between the flash steam outlet of the front flash tank 21 and the steam inlet of the front heater 26, and a final flow port 35a is provided on the partition between the flash steam outlet of the final flash tank 31 and the steam inlet of the final heater 36; among the components of the vacuum micro-pressure difference control device, an alkali solution spraying device 36a, a waterproof non-condensable gas suction device 36b, and a hot well liquid level measurement and control component 36c are arranged inside the tank body or on the tower body of the slurry multi-stage flash evaporation waste heat recovery tank body 20; the slurry multi-stage flash evaporation waste heat recovery tank body 20 adopts a cylindrical or square structure, and adopts a vertical or horizontal structure.

[0030] The pre-heater 26 and the final stage heater 36 respectively adopt a vertical shell-and-tube heat exchange structure or a horizontal transverse shell-and-tube heat exchange structure.

[0031] The conventional vacuum pump 18 adopts a water ring vacuum pump, a water jet vacuum pump or a Roots vacuum pump structure.

[0032] The micro-pressure differential vacuum pump 38 adopts a Roots vacuum pump structure or an ejector structure.

[0033] The alkali solution spraying device 36a adopts a nozzle type empty tower structure or a packing structure.

[0034] An alkali liquid spraying device 36a consistent with the final-stage heater 36 is arranged in the space where the pre-non-condensable gas S is located on the condensate water surface of the bottom hot well of the pre-heater 26, wherein the feed port of the alkali liquid spraying device 36a is also connected to the outlet of the alkali adding pump 30; the pre-heater 26 and the final-stage heater 36 can also be separately arranged or share an external high-vacuum desulfurization tank 39 containing the alkali liquid spraying device 36a, the air inlet of the high-vacuum desulfurization tank 39 is connected to the non-condensable gas outlet of the final-stage heater 36 and / or the pre-heater 26, the air outlet of the high-vacuum desulfurization tank 39 is connected to the inlet of the micro-pressure difference vacuum pump 38 and / or the conventional vacuum pump 18, the feed port of the alkali liquid spraying device 36a in the high-vacuum desulfurization tank 36e is connected to the outlet of the alkali adding pump 30, and the discharge port of the high-vacuum desulfurization tank 39 is connected to the outlet pipe of the final-stage external condensate W2.

[0035] The mass concentration range of sodium hydroxide in the sodium hydroxide solution Na is 0% to 60%.

[0036] The outlet pipe of the final-stage externally discharged condensed water W2 is respectively communicated with the inlet of the replenishment pipe of the heat network return water H1 and / or the outlet pipe of the front-stage externally discharged condensed water W1.

[0037] It should be noted that the present invention proposes a whole new set of integrated systems and operation strategies for deep flue gas waste heat recovery by flash evaporation of desulfurized slurry based on key technologies such as multi-stage flash evaporation of desulfurized slurry and comprehensive control of the vacuum degree inside each heater. According to this overall solution, there may be different specific implementation measures and specific implementation devices with different structures. The above specific implementation method is only one of them. Any other similar simple deformation implementation methods, such as simple deformation of flash steam and heat exchanger and simple adjustment of related pipelines, or simple change of vacuum extraction method, all fall within the protection scope of the present invention.

Claims

1. A vacuum micro-pressure difference control device for deep heat recovery of desulfurized slurry flash evaporation, comprising an original desulfurization tower (1), a desulfurized slurry graded flash evaporation subsystem (2) and a controllable vacuum condenser subsystem (3), wherein the desulfurized slurry graded 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 N stages of flash steam heaters, wherein N is greater than or equal to 2, wherein the first stage is a preheater (26), and the Nth stage is a final stage heater (36). The controllable vacuum condenser subsystem (3) further comprises a preheater (27), a final stage condenser pump (37), an alkali adding pump (30), a conventional 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 pipe of the heat network return water (H1), and the low-temperature water outlet of the preheater (26) is connected to the heat network return water (H1). The condensate outlet of the front heater (26) is connected to the inlet of the front condensate pump (27), and the outlet of the front condensate pump (27) is connected to the inlet of the washing spray layer of the front flash tank (21), the inlet of the washing spray layer 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 outlet pipe of the low-temperature process water (C2), and the internal heat exchange element of the final heater (36) is connected to the water outlet of the low-temperature process water (C1). The non-condensable gas disposal space is located above the bottom hot well liquid level, in which an alkali solution spraying device (36a) and a waterproof non-condensable gas suction device (36b) are provided. A hot well liquid level measurement and control component (36c) and a condensate mixing flow regulating valve (36d) are also provided inside and outside the hot well. 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 stage heater (36) is connected to the inlet of the final stage condensate pump (37), and the outlet of the final stage 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 connected to the final stage condensate discharge (W 2), the inlet of the alkali pump (30) is connected to the feed pipe of the sodium hydroxide solution (Na); the outlet of the waterproof non-condensable gas suction device (36b) is connected to the air 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 conventional vacuum pump (18) and the outlet of the pre-non-condensable gas (S) on the condensate liquid surface of the bottom hot well of the pre-heater (26), and the exhaust port of the conventional vacuum pump (18) is connected to the original flue gas inlet pipe (2) of the original desulfurization tower (1); the upstream of the original flue gas inlet pipe (2) 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. The vacuum micro-pressure difference control device for flash deep heat recovery of desulfurized slurry according to claim 1 is characterized in that The control method of the vacuum micro-pressure difference control device is as follows: I. When the inlet temperature of the low-temperature process water (C1) is less than 30°C, the final condensate pump (37) adjusts the condensate outlet flow rate to maintain the hot well liquid level at a set value according to the liquid level signal measured by the hot well liquid level measurement and control component (36c); the alkali pump (30) starts and adjusts the flow rate of the sodium hydroxide solution (Na), and the condensate mixing flow rate regulating valve (36d) adjusts the flow rate of the alkaline condensate mixed with the sodium hydroxide solution (Na), and the alkaline condensate returns to the alkali solution spraying device ( 36a) spraying and contacting with the non-condensable gas (S1) containing more SO2 and chemically reacting and absorbing SO2 to form NaSO3 and dissolving in the condensate of the lower hot well. The pH value of the condensate operates in the range of 7 to 9. The volume flow rate and pressure of the remaining non-condensable gas are greatly reduced to become non-condensable gas (S2) containing less SO2, which is then pumped out by a micro-pressure difference vacuum pump (38), mixed with the front non-condensable gas (S), and pumped out by a conventional vacuum pump (18) and sent to the smoke inlet of the original desulfurization tower (1); II. When the inlet temperature of the low-temperature process water (C1) is greater than or equal to 30°C and less than or equal to the inlet temperature of the heat network return water (H1), the final condensate pump (37) maintains the hot well liquid level at a set value by adjusting the condensate outlet flow rate according to the liquid level signal measured by the hot well liquid level measurement and control component (36c); the alkali pump (30) is turned off, the micro-pressure difference vacuum pump (38) is operated, and the non-condensable gas at the outlet of the micro-pressure difference vacuum pump (38) is mixed with the front non-condensable gas (S) and then extracted by the conventional vacuum pump (18) and sent to the smoke inlet of the original desulfurization tower (1); III. When the inlet temperature of the low-temperature process water (C1) is greater than the inlet temperature of the heat network return water (H1), the final condensate pump (37) maintains the hot well liquid level at a set value by adjusting the condensate outlet flow rate according to the liquid level signal measured by the hot well liquid level measurement and control component (36c); the alkali pump (30) is turned off, the micro-pressure difference vacuum pump (38) is stopped, and the non-condensable gas flowing through the micro-pressure difference vacuum pump (38) is mixed with the front non-condensable gas (S) and then extracted by the conventional vacuum pump (18) and sent to the smoke inlet of the original desulfurization tower (1).

3. The vacuum micro-pressure difference control method and device for flash deep heat recovery of desulfurized slurry according to claim 1, characterized in that The N-stage flash tanks and N-stage flash steam heaters are arranged as an integrated slurry multi-stage flash evaporation waste heat recovery tank body (20), wherein the interior is divided into two parts, namely a flash evaporation zone (20a) and a condensation heat exchange zone (20b), separated by a partition plate in the middle, wherein a front flow port (25a) is provided on the partition plate between the flash steam outlet of the front flash tank (21) and the steam inlet of the front heater (26), and a final flow port (35a) is provided on the partition plate between the flash steam outlet of the final flash tank (31) and the steam inlet of the final heater (36); in the components of the vacuum micro-pressure difference control device, an alkali liquid spraying device (36a), a waterproof non-condensable gas suction device (36b), and a hot well liquid level measurement and control component (36c) are arranged inside the tank body or on the tower body of the slurry multi-stage flash evaporation waste heat recovery tank body (20); the slurry multi-stage flash evaporation waste heat recovery tank body (20) adopts a cylindrical or square structure, and adopts a vertical or horizontal structure.

4. The vacuum micro-pressure difference control method and device for flash deep heat recovery of desulfurized slurry according to claim 1, characterized in that The front heater (26) and the final heater (36) respectively adopt a vertical shell-and-tube heat exchange structure or a horizontal transverse shell-and-tube heat exchange structure.

5. The vacuum micro-pressure difference control method and device for flash deep heat recovery of desulfurized slurry according to claim 1, characterized in that The conventional vacuum pump (18) adopts a water ring vacuum pump, a water jet steam extractor or a Roots vacuum pump structure.

6. The vacuum micro-pressure difference control method and device for flash deep heat recovery of desulfurized slurry according to claim 1, characterized in that The micro-pressure difference vacuum pump (38) adopts a Roots vacuum pump structure or an ejector structure.

7. The vacuum micro-pressure difference control method and device for flash deep heat recovery of desulfurized slurry according to claim 1, characterized in that The alkali solution spraying device (36a) adopts a nozzle-type empty tower structure or a filler structure.

8. The vacuum micro-pressure difference control method and device for flash deep heat recovery of desulfurized slurry according to claim 1, characterized in that The space where the pre-non-condensable gas (S) is located on the condensate surface of the hot well at the bottom of the pre-heater (26) is provided with an alkali solution spraying device (36a) which is consistent with the final heater (36), wherein the feed port of the alkali solution spraying device (36a) is also connected to the outlet of the alkali pump (30); the pre-heater (26) and the final heater (36) can also be provided separately or share an external high vacuum desulfurization tank (39) containing the alkali solution spraying device (36a), and the high vacuum desulfurization The air inlet of the tank (39) is connected to the non-condensable gas outlet of the final stage heater (36) and / or the pre-heater (26), the air outlet of the high vacuum desulfurization tank (39) is connected to the inlet of a micro-pressure difference vacuum pump (38) and / or a conventional vacuum pump (18), the feed inlet of the alkali solution spraying device (36a) in the high vacuum desulfurization tank (39) is connected to the outlet of the alkali adding pump (30), and the discharge port of the high vacuum desulfurization tank (39) is connected to the outlet pipe of the final stage condensate (W2).

9. The vacuum micro-pressure difference control method and device for flash deep heat recovery of desulfurized slurry according to claim 1, characterized in that The sodium hydroxide mass concentration of the sodium hydroxide solution (Na) is in the range of 0% to 60%.

10. The vacuum micro-pressure difference control method and device for flash deep heat recovery of desulfurized slurry 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).

Images