Evaporative crystallization process for strong brine

Abstract

The invention relates to a strong brine evaporative crystallization process which comprises the following steps: strong brine is injected into an evaporation preheating tank through a strong brine inlet pipeline; secondary steam and steam condensate are injected into the evaporation preheating tank, and strong brine in the evaporation preheating tank is preheated; evaporation condensate obtained after secondary steam is condensed through the preheating tank is conveyed to a circulating water system, and steam condensate is conveyed to a condensate pipe network in a plant; after preheating is completed, the strong brine is conveyed to an evaporation tank, low-pressure steam is injected into the evaporation tank, and the strong brine in the evaporation tank is heated through a coil pipe in the evaporation tank; strong brine in the evaporation tank is heated by low-pressure steam to reach crystallization conditions and finally flows into the advection pool to be cooled and crystallized. Strong brine is treated through evaporative crystallization, so that a factory does not depend on an expensive reverse osmosis membrane any more, and salt separation is achieved in a physical evaporation and crystallization mode.

Description

Technical Field

[0001] The present invention relates to the technical field of concentrated brine treatment, and particularly relates to a concentrated brine evaporation and crystallization process. Background Art

[0002] Since the company started commissioning, the salt content of the water from the Yili River has doubled compared with the design (the designed conductivity is 200 us / cm, and the actual average conductivity of the incoming water is 450 us / cm), resulting in the concentrated brine treatment load exceeding the system design processing capacity.

[0003] Due to the new environmental impact assessment requirements, the system's concentrated brine has been changed from reduced discharge to evaporation ponds to "zero discharge". To implement the new environmental impact assessment requirements and ensure the smooth implementation of "zero discharge", part of the concentrated brine can only be recycled to the front end of the system or discharged into a rigid temporary storage pond for storage, further increasing the high-salt water treatment load and causing salt accumulation in the water system.

[0004] The concentrated brine that cannot be treated by the evaporation device returns to the system, resulting in salt accumulation in the system, continuous increase in conductivity, reduction in the recovery rate of the reverse osmosis membrane, further increase in the amount of concentrated brine in the system, and gradual increase in the return flow of concentrated brine. Such repeated cycles lead to continuous deterioration of water quality, causing scaling and fouling of the water coolers in the chemical plant, frequent cleaning, frequent corrosion and leakage, and affecting the safe operation of the system.

[0005] In traditional processes, reverse osmosis technology is usually used to remove the salt content of water. However, the reverse osmosis membrane in reverse osmosis technology is relatively expensive. Since the daily amount of concentrated brine to be treated in coal chemical plants is large, the quantity and scale of the required reverse osmosis membranes also increase accordingly, resulting in high initial investment costs. At the same time, the reverse osmosis membrane will be contaminated and worn during use and needs to be replaced and maintained regularly. For a large-scale and continuous production process such as coal chemical industry, the cost of membrane replacement and maintenance is also a significant expense, which excessively increases the maintenance cost. Summary of the Invention

[0006] The purpose of the present invention is to provide a concentrated brine evaporation and crystallization process to solve the above problems existing in the prior art.

[0007] The technical solution of the present invention to solve the above technical problems is as follows:

[0008] A concentrated brine evaporation and crystallization process includes the following steps:

[0009] Step S01: Inject concentrated brine into the interior of an evaporation preheating tank through a concentrated brine inlet pipe;

[0010] Step S02: Inject secondary steam and steam condensate into the interior of the evaporation preheating tank to preheat the concentrated brine inside the evaporation preheating tank;

[0011] Step S03: After preheating the concentrated brine to over 40 degrees, start the concentrated brine pump, transport the concentrated brine into the evaporation tank, and perform temperature-raising and concentration treatment on the concentrated brine;

[0012] Step S04: Inject low-pressure steam into the evaporation tank, and heat the concentrated brine inside the evaporation tank through the internal coil of the evaporation tank;

[0013] Step S05: When the concentrated brine is heated to the saturated crystallization state, discharge the concentrated brine into the horizontal flow tank to perform cooling crystallization treatment on the concentrated brine;

[0014] Step S06: Start the salt solution self-priming pump, send the saturated concentrated salt solution after cooling crystallization back into the evaporation preheating tank, and then discharge it into the concentrated brine water pipe.

[0015] Step S07: The condensed evaporation condensate is sent to the circulating water system, the steam condensate enters the condensate water tank, and through the condensate transfer pump, the steam condensate is transported to the in-plant condensate pipe network.

[0016] The beneficial effects of the present invention are: By evaporative crystallization to treat concentrated brine, the factory no longer relies on expensive reverse osmosis membranes, but realizes the separation of salts through physical evaporation and crystallization. At the same time, the evaporative crystallization technology can avoid the high procurement cost of reverse osmosis membranes when treating large-scale concentrated brine, reducing the cost expenditure of the factory.

[0017] On the basis of the above technical solution, the present invention can also be improved as follows.

[0018] Further, step S04 also includes: When injecting low-pressure steam into the evaporation tank, it is necessary to warm the pipe for no less than 15 minutes. Before the evaporation tank boils completely, slowly introduce the steam to avoid damage to the equipment and pipelines caused by the steam-water impact phenomenon.

[0019] The beneficial effect of adopting the above is: The pipe warming operation can ensure uniform temperature distribution in the steam pipeline, thereby avoiding local overheating or overcooling phenomena, which helps to improve the evaporation efficiency in the evaporation tank.

[0020] Further, step S04 also includes: When the concentrated brine is transported into the evaporation tank, cool the low-pressure steam in the evaporation tank and transport it to the preheating tank through the condensate pipeline, cool it again and then enter the condensate water tank, and finally enter the in-plant condensate pipe network.

[0021] The beneficial effect of adopting the above is: The reuse of low-pressure steam reduces the amount of low-pressure steam required to treat concentrated brine, helps to reduce the treatment cost, and improves the economic benefits of the enterprise.

[0022] Further, step S04 further includes: after the secondary steam is condensed, the evaporation condensate in the evaporation preheating tank is transported through a pipeline to the inside of the secondary reverse osmosis product water tank for storage, overflows to the recycled water tank, and is replenished into the circulating water system.

[0023] The beneficial effect of adopting the above is that the reuse of the evaporation condensate reduces the make-up water volume of the circulating water system, helps to reduce the treatment cost, and improves the economic benefits of the enterprise.

[0024] Further, step S05 further includes: when discharging the concentrated brine from the evaporation tank, it is necessary to first observe the inlet liquid level and the liquid level after evaporation, and only when it meets the standard can the outlet valve of the evaporation tank be opened to discharge the liquid into the horizontal flow tank.

[0025] The beneficial effect of adopting the above further solution is that observing the inlet liquid level and the liquid level after evaporation before opening the outlet valve can ensure that the liquid in the evaporation tank will not overflow the evaporation tank due to evaporation boiling, thus avoiding damage to the equipment and the environment.

[0026] Further, step S05 further includes: when discharging the concentrated brine from the evaporation tank, observe the downward trend of the liquid level in the evaporation tank. When the downward trend is relatively slow, after the discharging is completed, open the cleaning door of the evaporation tank to check the scaling condition on the outside of the heating coil inside. When the scaling is serious, clean it.

[0027] The beneficial effect of adopting the above further solution is that by observing the downward trend of the liquid level, the scaling condition on the outside of the heating coil in the evaporation tank can be detected in time and cleaned, thereby reducing the influence of the scaling phenomenon on the evaporation process of the concentrated brine. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a process flow chart of a concentrated brine evaporation and crystallization process of the present invention;

[0029] Figure 2 is a schematic diagram of the system of a concentrated brine evaporation and crystallization process of the present invention;

[0030] Figure 3 is a partial system structure schematic diagram of a concentrated brine evaporation and crystallization process of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] The principles and features of the present invention will be described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0032] Embodiment 1

[0033] As Figures 1 to 3 shown, a concentrated brine evaporation and crystallization process includes the following steps:

[0034] Step S01: Inject brine into the interior of the evaporation preheating tank through the brine inlet pipeline;

[0035] Step S02: Inject secondary steam and steam condensate into the interior of the evaporation preheating tank to preheat the brine inside the evaporation preheating tank;

[0036] Step S03: After preheating the brine to over 40 degrees, start the brine pump and transport the brine to the interior of the evaporation tank to perform a rapid temperature increase treatment on the brine;

[0037] Step S04: Inject low-pressure steam into the interior of the evaporation tank and heat the brine inside the evaporation tank through the coil inside the evaporation tank;

[0038] Step S05: When the brine is heated to the saturated crystallization state, discharge the brine into the horizontal flow tank to perform a cooling crystallization treatment on the brine;

[0039] Step S06: Start the salt solution self-priming pump, send the saturated brine solution after cooling crystallization back to the interior of the evaporation preheating tank, and then discharge it into the brine water pipe.

[0040] Step S07: The condensed evaporation condensate is sent to the circulating water system, the steam condensate enters the condensate water tank, and through the condensate water delivery pump, the steam condensate is transported to the in-plant condensate pipe network.

[0041] The brine inlet enters the evaporation preheating tank, and the brine is preheated using secondary steam and steam condensate to initially increase the temperature of the brine, so as to reduce the energy consumption in the subsequent evaporation process. At the same time, using secondary steam and steam condensate to preheat the brine realizes the recycling of energy, thereby reducing the overall energy consumption. Subsequently, the brine is transported into the evaporation tank and heated by low-pressure steam to re-increase the temperature of the brine to reach the crystallization condition. The brine is treated by evaporation crystallization, enabling the factory to no longer rely on expensive reverse osmosis membranes, but to achieve the separation of salts through physical evaporation and crystallization. At the same time, the evaporation crystallization technology can avoid the high procurement cost of reverse osmosis membranes when treating large-scale brine, reducing the cost expenditure of the factory.

[0042] In specific implementation, since a large amount of steam is easily generated during the production process of the coal chemical company, this steam can be directly used as the heat source for use inside the evaporation tank. Since the steam itself is a by-product generated during the production process, using this steam as the heat source can significantly reduce the enterprise's energy cost. Compared with using other external heat sources such as electricity or natural gas, using its own steam resources can save a large amount of energy costs and reduce the cost expenditure.

[0043] Among them, multiple evaporation tanks can be arranged in parallel. When dealing with a large amount of concentrated brine or rapid evaporation is required, the parallel evaporation tanks can share the load together to ensure the smooth progress of the evaporation process. At the same time, when one evaporation tank fails, the other parallel evaporation tanks can continue to work, thereby reducing the failure shutdown rate of the entire system.

[0044] Among them, multiple groups of coils are arranged in the evaporation tank (such as Figure 3 ). It can increase the steam heat exchange area and improve the heat exchange efficiency.

[0045] Example 2

[0046] Such as Figure 1 shown, this embodiment is a further improvement on the basis of Embodiment 1, specifically as follows:

[0047] Step S04 further includes: when injecting low-pressure steam into the evaporation tank, the pipe needs to be warmed up for no less than 15 minutes. Before the evaporation tank boils completely, the steam is introduced slowly to avoid damage to the equipment and pipelines caused by the phenomenon of steam-water shock. The pipe warming operation can ensure the uniform distribution of temperature in the steam pipeline, thus avoiding local overheating or overcooling phenomena, which helps to improve the evaporation efficiency in the evaporation tank.

[0048] Example 3

[0049] Such as Figure 2 shown, this embodiment is a further improvement on the basis of Embodiment 1, specifically as follows:

[0050] The said step S04 further includes: when the concentrated brine is transported into the evaporation tank, the low-pressure steam in the evaporation tank is cooled and then transported to the preheating tank through the condensate pipeline, and then enters the condensate water tank after further cooling, and finally enters the in-plant condensate pipeline network.

[0051] The said step S02 further includes: when the secondary steam condenses, the evaporation condensate in the evaporation preheating tank is transported through the pipeline to the inside of the secondary reverse osmosis water production tank for storage, overflows to the reused water tank, and is replenished into the circulating water system.

[0052] The reuse of evaporation condensate and low-pressure steam reduces the amount of low-pressure steam required for treating concentrated brine and the make-up water amount of the circulating water system, which helps to reduce the treatment cost and improve the economic benefits of the enterprise.

[0053] Example 4

[0054] Such as Figure 3 shown, this embodiment is a further improvement on the basis of Embodiment 1, specifically as follows:

[0055] The step S05 further includes: when discharging concentrated brine from the evaporation tank, it is necessary to first observe the water inlet level and the level after evaporation. Only after meeting the standards can the outlet valve of the evaporation tank be opened to drain the liquid into the horizontal flow tank. Observing the water inlet level and the level after evaporation before opening the outlet valve can ensure that the liquid in the evaporation tank will not overflow due to evaporation and boiling, thus avoiding damage to the equipment and the environment. At the same time, by controlling the water inlet level and the level after evaporation, the dynamic balance of the liquid volume in the evaporation tank can be maintained, ensuring the continuity and stability of the evaporation process.

[0056] Embodiment 5

[0057] As Figure 1 shown, this embodiment is a further improvement on Embodiment 1, specifically as follows:

[0058] The step S05 further includes: when discharging concentrated brine from the evaporation tank, observe the trend of the liquid level drop in the evaporation tank. When the drop trend is relatively slow, after the discharging is completed, open the cleaning door of the evaporation tank to inspect the scaling condition on the outside of the heating coil inside. When the scaling is serious, clean it. By observing the trend of the liquid level drop, the scaling condition on the outside of the heating coil in the evaporation tank can be detected in time and cleaned, thus reducing the influence of the scaling phenomenon on the evaporation process of the concentrated brine.

[0059] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A concentrated brine evaporation and crystallization process, characterized in that, It includes the following steps: Step S01: Inject the concentrated brine into the interior of the evaporation preheating tank through the concentrated brine inlet pipeline; Step S02: Inject secondary steam and steam condensate into the interior of the evaporation preheating tank to preheat the concentrated brine inside the evaporation preheating tank; Step S03: After preheating the concentrated brine by more than 40 degrees, start the concentrated brine pump and transport the concentrated brine to the interior of the evaporation tank for rapid heating of the concentrated brine; Step S04: Inject low-pressure steam into the interior of the evaporation tank and heat the concentrated brine inside the evaporation tank through the coil inside the evaporation tank; Step S05: When the concentrated brine is heated to the saturated crystallization state, discharge the concentrated brine into the horizontal flow tank for cooling crystallization treatment of the concentrated brine; Step S06: Start the salt solution self-priming pump, send the saturated concentrated salt solution after cooling crystallization back into the evaporation preheating tank, and then discharge it into the concentrated brine water pipe. Step S07: The condensed evaporation condensate is sent to the circulating water system, the steam condensate enters the condensate water tank, and through the condensate transfer pump, the steam condensate is transported to the in-plant condensate pipe network.

2. The concentrated brine evaporation and crystallization process according to claim 1, characterized in that, Step S04 further includes: When injecting low-pressure steam into the evaporation tank, it is necessary to warm the pipe for no less than 15 minutes, and slowly introduce air before the evaporation tank boils completely.

3. The concentrated brine evaporation and crystallization process according to claim 2, characterized in that, Step S04 further includes: When the concentrated brine is transported into the evaporation tank, the low-pressure steam in the evaporation tank is cooled and then transported to the preheating tank through the condensate pipeline, cooled again and then enters the condensate water tank, and finally enters the in-plant condensate pipe network.

4. The concentrated brine evaporation and crystallization process according to claim 1, characterized in that, Step S02 further includes: When the secondary steam condenses, the evaporation condensate in the evaporation preheating tank is transported to the interior of the secondary reverse osmosis water production tank through a pipeline for storage, overflows to the recycled water tank, and is replenished into the circulating water system.

5. The concentrated brine evaporation crystallization process according to claim 1, wherein, Step S05 further includes: When discharging the concentrated brine from the evaporation tank, it is necessary to observe the inlet liquid level and the liquid level after evaporation first.

6. The concentrated brine evaporation and crystallization process according to claim 1, wherein Step S05 further includes: When discharging the concentrated brine from the evaporation tank, observe the trend of the liquid level drop in the evaporation tank.

7. The evaporation and crystallization process of concentrated brine according to any one of claims 1 to 6, characterized in that, A plurality of the evaporation tanks can be arranged in parallel.

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