Flue gas method brine purification and salt production by-product resource coupling utilization system and method thereof

Abstract

The invention belongs to the technical field of resource utilization and environmental protection, and relates to a flue gas method brine purification and salt production by-product resource coupling utilization system and method, the system comprises: a first primary reaction tank, a second primary reaction tank, a second reaction tank, a third reaction tank, a fourth reaction tank, a fifth reaction tank and a high nitrate liquid tank. According to the raw brine (sodium sulfate content), the high-nitrate liquid and the quick lime are added, so that the refined brine index is realized, and the production is stable; second-stage salty mud of the second-stage reaction tank, and / or fourth-stage salty mud of the fourth-stage reaction tank, and / or fifth-stage salty mud of the fifth-stage reaction tank are recycled and added into the third-stage reaction tank, excessive flue gas is introduced, the flue gas preferentially reacts with the salty mud powder in the process, and conditions are provided for follow-up sedimentation acceleration; in addition, a lime-flue gas method and a two-alkali continuous method-double-membrane method can be realized to promote collaborative development.

Description

Technical Field

[0001] The present invention relates to the technical field of resource utilization and environmental protection, and in particular to a system and method for coupling resource utilization of brine purification and salt production byproducts using a flue gas method. Background Art

[0002] Brine purification technology is a key process in the salt industry to improve the purity of refined salt products, reduce the impurity content in salt, and improve the whiteness of salt products. It is an important process to increase the effective working time of salt-making enterprises, extend the service life of equipment, and reduce energy consumption. It is one of the important measures to improve the comprehensive utilization rate of resources and is beneficial to salt chemical production. It is one of the important ways to reduce production costs in the salt industry.

[0003] 1.1 Vacuum salt and saltpeter production requires a large amount of steam. Its public works - thermal power plants, in addition to producing steam and electricity, also produce a large amount of flue gas. The components of flue gas are N2, O2, CO2, H2O, NOx, SOx, NH3, acid mist, heat, water vapor and smoke, etc. The main components of flue gas after flue gas-denitrification-dust removal-desulfurization-dust removal purification are N2, O2, CO2, H2O steam and heat. Directly discharged into the atmosphere pollutes the environment and is also a waste of natural resources. The salt-making industry uses the lime flue gas method brine purification process to fully utilize the CO2 in the purified flue gas to remove impurities in the brine, which not only reduces the pollution of the flue gas exhaust to the environment, but also recovers the heat of the flue gas, achieving energy conservation and emission reduction, and resource recycling. However, there are still some problems, such as:

[0004] (1) During the flue gas purification process, the salt mud particles generated by the carbonization reaction are uneven, the content of pink salt mud is high, and the sedimentation rate is slow. Regardless of whether a sedimentation aid is added or not, large and small particles settle in turn during the salt mud sedimentation process. The thickness of the pink salt mud layer in the critical area between salt mud and clear brine is high. When the clear brine level is low, the salt mud in the pink salt mud layer will float up, affecting the quality and amount of clear brine. In order to improve the amount and quality of clear brine and reduce the amount of salt mud, the production often uses a clear brine filtration device or keeps the salt mud level high, but this will affect the brine purification efficiency.

[0005] (2) The generated powdered salt mud is easy to block the outlet of the flue gas coil at the bottom of the reaction tank, the carbonization reaction time is long, the equipment maintenance is increased, and the purification efficiency is affected.

[0006] (3) Salt sludge is recovered for brine purification, which requires further cleaning and sedimentation. Although the resources are further utilized, it is not only time-consuming, but also affects the clarity and quality of the prepared refined brine. In addition, the clarity of the washing water for washing salt sludge is low. Transporting it to the return water pool will cause salt sludge to settle at the bottom. Pipeline transport of return water back to the mine for a long time will cause salt sludge to accumulate and seriously block the pipe.

[0007] (4) The endpoint of carbonization reaction is controlled by testing the pH value, calcium ion and two alkali contents of the clean brine. The online pH monitoring in production is inaccurate due to the corrosion of the brine during long-term immersion in the brine. Manual sampling and detection often encounter flue gas flow, which will generate calcium carbonate precipitation and continue to react with CO2 and H2O to generate soluble calcium bicarbonate, making the refined brine index fail to meet the standard.

[0008] 1.2 High nitrate liquid is produced in the process of salt and nitrate co-production or double membrane production. After the raw brine is purified by removing calcium and magnesium, the refined brine enters the salt and nitrate evaporation system. During the salt and nitrate production process, the multi-effect evaporation terminal discharges liquid or discharges high nitrate liquid. The main components of high nitrate liquid are NaCl: 270-292g / L, Na2SO4: 55-80g / L, CO32-: 1.0-4.6g / L, OH-: 0.2-1.5g / L, Ca2+≤10mg / L, Mg2+≤5.0mg / L. At present, high nitrate liquid has no obvious market value. Most companies use high nitrate liquid evaporation to extract nitrate or freezing + hot melting to extract nitrate, or use the process of recovering refined brine tanks and discharging back to the well to extract brine. The liquid salt produced by the nanofiltration membrane method has obvious advantages over other commonly used chemical refining methods. The sulfate content of the produced liquid salt is stable; this process has been widely promoted and applied, but there are still some problems, such as:

[0009] (1) The comprehensive utilization of the discharged minerals affects the enrichment of certain components in the original brine. At the same time, the high-nitrate water contains a large amount of sulfate ions. If it is discharged without treatment, it will cause serious environmental pollution, lead to water acidification, pH reduction, and further damage the soil structure, resulting in adverse consequences.

[0010] (2) Freezing + hot melting and other processes, which are complex, energy-intensive and expensive.

[0011] (3) Nanofiltration membranes inevitably produce high-sulfate-content high-nitrate solution during the filtration process, which currently has no obvious market value.

[0012] (4) The discharge of high-nitrate solution back to the well for brine extraction will inevitably cause changes in the composition of brine, including SO4 2- If the content increases, it will affect the brine purification, saltpeter co-production and product quality.

[0013] (5) During the brine pipeline transportation process, long-distance and long-term transportation of the brine will cause pipeline crystallization and even blockage. (6) High nitrate solution is used for lime flue gas brine purification. The process has a small output, and the raw brine SO4 2- The content is unstable, and the raw material components have changed. In the application process, the raw material parameters, reaction parameters, process parameters, operating parameters and operating procedures are unstable, and the advantages of this process cannot be fully utilized. There are many problems. How to make comprehensive use of it is a difficult problem that plagues the industry. Summary of the invention

[0014] While utilizing resources, the present invention discovered the following problems:

[0015] 1. The main component of raw halogen is Ca 2+ :0.8~1.8g / L、Mg 2+ :0.3~0.5g / L, NaCl:285~308g / L, Ph:7.0~7.8, it also contains Na2SO4, but the content of Na2SO4 is not fixed, sometimes it is high nitrate brine, sometimes it is low nitrate brine, which affects the reaction efficiency of the first-stage reactor and the index of preparing the second-stage refined brine is unstable, which will affect the carbonization reaction efficiency of the second-stage reactor (too much or insufficient carbonate is generated by calcium removal and additional raw materials need to be added for adjustment) and the index of the second-stage refined brine. If the sulfate in the second-stage refined brine exceeds 15.5g / L, it will affect the salt making system and the quality of the product. In short, the instability of the entire production brings many impacts.

[0016] 2. Most salt production processes use external high nitrate solution to control the stability of the salt production system and the quality of the product. If the external high nitrate solution (sodium sulfate) is recycled into the salt production system, sodium sulfate will be enriched, which will affect the stability of the salt system and the quality of the product, and the resources will not be well utilized.

[0017] 3. A large amount of salt mud is produced, and there is a defect that the salt mud sedimentation rate is slow.

[0018] In order to reduce the environmental burden and utilize resources as much as possible, the present invention provides a flue gas brine purification and resource coupling utilization system and method for salt production by-products.

[0019] In order to achieve the purpose of the present invention, the technical solution adopted is as follows:

[0020] A flue gas brine purification and resource coupling utilization system for salt production byproducts, comprising a first-level reaction tank, a second-level reaction tank, a second-level reaction tank, a third-level reaction tank, a fourth-level reaction tank, a fifth-level reaction tank and a high-nitrate liquid tank;

[0021] The first-stage reaction tank is provided with a first lime milk feed port, a first raw brine feed port, a first high nitrate liquid feed port, a first-stage refined brine discharge port, and a first-stage mud discharge port;

[0022] The second-level reaction tank is provided with a second lime milk feed port, a second raw brine feed port, a second high nitrate liquid feed port, a second-level refined brine discharge port, and a second-level mud discharge port;

[0023] The secondary reaction tank is provided with a second-level refined brine feed port connected to the second-level refined brine discharge port, and is also provided with a second-level refined brine discharge port, a second-level mud discharge port, and a second-level flue gas inlet port;

[0024] The three-stage reaction tank is provided with a three-stage flue gas inlet, a mud feed port, a first-stage refined brine feed port connected to the first-stage refined brine discharge port, a three-stage high nitrate liquid feed port, a three-stage mud discharge port and a three-stage refined brine discharge port. The mud feed port of the three-stage reaction tank is connected to the second-stage mud discharge port, and the three-stage high nitrate liquid feed port is connected to the high nitrate liquid outlet of the salt making system.

[0025] The four-stage reaction tank is provided with a three-stage refined brine feed port connected to the three-stage refined brine discharge port, a third-stage refined brine feed port connected to the first-stage refined brine discharge port, a four-stage mud discharge port and a four-stage refined brine discharge port, and the four-stage mud discharge port is connected to the mud feed port of the three-stage reaction tank;

[0026] The five-stage reaction tank is provided with a third raw brine feed port, a fourth-stage refined brine feed port connected to the fourth-stage refined brine discharge port, a fifth-stage mud discharge port and a fifth-stage refined brine discharge port, and the fifth-stage mud discharge port is connected to the mud feed port of the third-stage reaction tank;

[0027] When the system is working:

[0028] In the second-stage reaction tank, high nitrate solution and lime milk are added according to the sodium sulfate content in the original brine, and the second-stage refined brine components obtained after the reaction are controlled to be C(Na2SO4):18-22g / L, C(NaOH):1.2-1.6g / L, C(Ca 2+ )≤0.66g / L, C(NaCl):280-305g / L, S(suspended matter)≤1.8mg / L;

[0029] In the first stage reaction tank, high nitrate solution and lime milk are added according to the sodium sulfate content in the original brine, and the first stage refined brine composition obtained after the reaction is controlled to be C(SO4 2- )≥18.2g / L, C(NaOH)≥1.5g / L, C(Ca 2+ )≤0.32g / L, C(NaCl):275-305g / L, S(suspended matter)≤2.0mg / L;

[0030] Flue gas is introduced into the secondary reaction tank to control the C (Ca 2+ )≤12mg / L, C(Mg 2+ )≤4mg / L, C(Na2CO3)≤0.45g / L, C(NaOH)≤0.25g / L, C(SO4 2- )≤15.5g / L, C(NaCl):295-305g / L, S(suspended matter)≤0.8mg / L, at the same time, OH in the secondary refined brine - and Ca 2+ Total substance ratio n = [(nOH - / 2) / nCa2+ ], 1.12≤n≤1.24;

[0031] Add the first stage refined halogen and excess flue gas to the three-stage reaction tank to obtain HCO3 - , put the secondary mud, and / or the quaternary mud, and / or the fifth mud into the third-stage reaction tank, introduce excess flue gas, make it fully react (the salt mud content no longer changes, which is the reaction end point), then introduce high nitrate solution, take the clear liquid to test C (Ca 2+ )≤0.08g / L, stop adding high nitrate solution, and after sufficient reaction, stand and separate to obtain third-grade refined brine and third-grade mud;

[0032] The flue gas is purified flue gas after denitration, dust removal, desulfurization and deammoniation;

[0033] The third-level refined brine is transported to the fourth-level reaction tank. At the same time, the fourth-level reaction tank uses the first-level refined brine to adjust the pH value to 10.2-10.8. After sufficient reaction, the fourth-level refined brine and the fourth-level mud are obtained;

[0034] All the fourth-level refined brine is transported to the fifth-level reaction tank, and the original brine is added to the fifth-level reaction tank at the same time. After sufficient reaction, the fifth-level refined brine is obtained. The composition of the fifth-level refined brine is C(Ca 2+ )≤10mg / L, C(Mg 2+ )≤4.0mg / L, C(Na2CO3)≤0.52g / L, C(NaOH)≤0.25g / L, S(suspended matter)≤0.8mg / L.

[0035] Furthermore, it also includes a salt-making system, which is provided with a refined brine feed inlet and a high nitrate liquid outlet, the refined brine feed inlet is connected to the secondary refined brine discharge port, and the high nitrate liquid outlet of the high nitrate liquid tank is connected to the high nitrate liquid feed inlet of the high nitrate liquid tank.

[0036] Furthermore, it also includes a double membrane system for membrane separation of the fifth-level refined brine. The specific double membrane system is provided with a fifth-level refined brine feed port and a high nitrate liquid outlet. The fifth-level refined brine feed port is connected to the fifth-level refined brine discharge port, and the high nitrate liquid outlet is connected to the high nitrate liquid tank. More specifically, when Na2SO4≤23g / L in the fifth-level refined brine, the fifth-level refined brine is transported to the salt-making system. When Na2SO4>23g / L in the fifth-level refined brine, it is divided into two streams, one of which is sent to the double membrane system for membrane separation to obtain the low nitrate liquid, and then mixed with the other stream of the fifth-level refined brine to adjust Na2SO4≤23g / L, and then transported to the salt-making system to obtain salt and high nitrate liquid.

[0037] The main reaction principle in each reaction tank of the present invention is as follows:

[0038] 1. The main reactions in the first and second stage reaction tanks include:

[0039] CaO+H2O→Ca(OH)2

[0040] Ca(OH)2+Na2SO4→CaSO4↓+2NaOH

[0041] Ca 2+ +CO3 2- →2CaCO3↓

[0042] Mg 2+ +2OH - →Mg(OH)2↓

[0043] Fe 3+ +3OH - →Fe(OH)3↓

[0044] 2. The main reactions in the secondary reaction tank include:

[0045] CO2↑+2NaOH→2Na2CO3

[0046] Ca 2+ +CO3 2- →CaCO3↓

[0047] 3. The main reactions in the tertiary reaction tank include (first react with flue gas and then add high nitrate solution):

[0048] Ca(OH)2+Na2SO4→CaSO4+2NaOH

[0049] CO2 (excess) + NaOH → NaHCO3

[0050] CaCO3+CO2+H2O→Ca(HCO3)2

[0051] Ca(HCO3)2+Na2SO4→CaSO4↓+2NaHCO3

[0052] NaHCO3+NaOH→Na2CO3+H2O

[0053] Ca 2+ +CO3 2- →2CaCO3↓

[0054] 4. The main reactions in the four-stage reactor include:

[0055] HCO3 - +OH - →CO3 2- +H2O

[0056] Ca 2+ +CO3 2- →2CaCO3↓

[0057] 5. The main reactions in the five-stage reaction tank include:

[0058] Ca 2+ +CO3 2- →2CaCO3↓

[0059] +2OH - →Mg(OH)2↓Mg 2+

[0060] Fe 3+ +3OH - →Fe(OH)3↓

[0061] The present invention is based on the above system. The purpose of setting up the three-stage reaction tank is mainly to optimize the mud composition, and at the same time, unexpected technical effects are achieved: the amount of powdered salt mud in the mud is reduced, the mud sedimentation speed is accelerated, and the clarity of the refined brine is improved; the salt mud washing removes chloride ions and has a high dehydration rate. The purpose of setting up the four-stage reaction tank is to utilize the OH in the first-stage refined brine. - The excess HCO3 produced by the third-stage reaction tank - Converted to CO3 2- , thereby further promoting the precipitation of calcium ions; the purpose of setting up a five-stage reaction tank is to contain too much OH in the fourth-stage refined brine. - and CO3 2- , which is not good for salt production, so it cannot be directly sent to the salt production system. Therefore, with the help of raw brine, on the one hand, excessive OH in the fourth-level refined brine is removed. - , and at the same time can convert Ca 2+ Mg 2+ , Fe 3+ Remove.

[0062] The present invention also provides a method for coupling utilization of flue gas brine purification and salt production by-products. The method is based on the above-mentioned flue gas brine purification and salt production by-products resource coupling utilization system and comprises the following steps:

[0063] Add raw brine, lime milk and high nitrate solution into the first-stage reaction tank, adjust the sodium sulfate content in the system to ≥26.9g / L, and add lime milk in an amount of 1.2-1.8g / L expressed by the theoretical concentration of quicklime in the system. After sufficient reaction, stand and separate to obtain the first-stage mud and the first-stage refined brine;

[0064] Add raw brine, lime milk and high nitrate solution into the second-level reaction tank, adjust the sodium sulfate content in the system to 19.5-24g / L, and the amount of lime milk added is 0.95-1.22g / L expressed by the theoretical concentration of quicklime in the system. After sufficient reaction, stand and separate to obtain the second-level mud and the second-level refined brine;

[0065] The second level refined brine is transported to the second level reaction tank, where flue gas is introduced and fully reacted under stirring conditions. After the reaction is completed, the reaction is allowed to stand and separate to obtain second level mud and second level refined brine;

[0066] Add the first-stage refined brine (if the first-stage refined brine is not added, sodium bicarbonate will precipitate in the third-stage reaction tank) and excess flue gas to obtain HCO3 - , put the secondary mud, and / or the quaternary mud, and / or the fifth mud into the third-stage reaction tank, pass in excess flue gas, and then pass in high nitrate solution, take the clear liquid to test C (Ca 2+ )≤0.08g / L, stop adding high nitrate solution, stir the reaction thoroughly, and stand for separation after the reaction is completed to obtain third-grade refined brine and third-grade mud;

[0067] The third-level refined brine is transported to the fourth-level reaction tank. At the same time, the fourth-level reaction tank uses the first-level refined brine to adjust the pH value to 10.2-11.3. After sufficient stirring and reaction, it is allowed to stand and separate to obtain the fourth-level refined brine and the fourth-level mud.

[0068] All the fourth-level refined brine is transported to the fifth-level reaction tank, and the original brine is added to the fifth-level reaction tank at the same time. After sufficient stirring for reaction, the fifth-level refined brine is obtained by standing and separating.

[0069] Furthermore, the specific method of adding the raw brine, lime milk and high nitrate solution in the second primary reaction tank is:

[0070] When the sodium sulfate content in the original brine is lower than 13g / L, high nitrate solution is added to make the sodium sulfate content 19.5-24g / L. The final calculation shows that the calcium ion is no higher than 0.66g / L, the amount of lime milk is controlled at 1.05-1.22g / L, and the carbonization endpoint pH is controlled at 9.0-9.5;

[0071] When the sodium sulfate content in the original brine is 13-18 g / L, high nitrate solution is added to make the sodium sulfate content 19.5-24 g / L. The final calculation shows that the calcium ion is no higher than 0.60 g / L, the amount of lime milk is controlled at 1.0-1.18 g / L, and the carbonization endpoint pH is controlled at 8.9-9.6;

[0072] When the sodium sulfate content in the original brine is higher than 18g / L, high nitrate solution is added to make the sodium sulfate content 19.5-24g / L. The final calculation shows that the calcium ion is no higher than 0.58g / L, the feeding amount of lime milk is controlled at 0.95-1.15g / L, and the endpoint pH of the carbonization reaction is controlled at 9.0-9.6.

[0073] Furthermore, the specific method of adding the raw brine, lime milk and high nitrate solution in the second primary reaction tank is:

[0074] When the content of sodium sulfate in the original brine is 16g / L, the amount of quicklime added is 1.3 times the normal amount of quicklime added, and the control point of the pH value of the carbonization reaction is 9.0-9.6;

[0075] When the sodium sulfate content in the raw brine is 18g / L, the amount of quicklime added is 1.15 times the normal amount of quicklime added, and the control point of the pH value of the carbonization reaction is 9.0-9.6;

[0076] When the sodium sulfate content in the raw brine is 20g / L, the quicklime feeding amount is 1.0 times the normal quicklime feeding amount, and the control point of the pH value of the carbonization reaction is 9.5-10; when the sodium sulfate content in the raw brine is 22g / L, the quicklime feeding amount is 0.95 times the normal quicklime feeding amount, and the control point of the pH value of the carbonization reaction is 9.5-10.5;

[0077] The sodium sulfate content in the raw brine is 24g / L, the quicklime feed amount is 0.9 times the normal quicklime feed amount, and the control point of the carbonization reaction pH value is 9.8-10.8;

[0078] The normal feeding amount of the quicklime is 1.05-1.22 g / L.

[0079] In order to improve the reaction efficiency as much as possible, preferably, the first stage reaction tank controls the reaction temperature to be 35-45°C and the reaction time to be 4-6h;

[0080] And / or, the second primary reaction tank controls the reaction temperature to be 35-45°C and the reaction time to be 4-7h;

[0081] And / or, the reaction temperature is controlled to be 25-35°C before the high nitrate solution is introduced into the tertiary reaction tank, the reaction time is 2-5 hours, and the reaction is continued for 1.5-2 hours after the high nitrate solution is introduced;

[0082] And / or, the reaction temperature of the fourth-stage reaction tank is controlled to be 20-40° C. and the reaction time is 0.5-1.5 h;

[0083] And / or, the five-stage reaction tank controls the reaction temperature to be 30-45° C. and the reaction time to be 1.5-2 h.

[0084] Compared with the prior art, the present invention also achieves the following beneficial effects:

[0085] (1) The present invention adds high nitrate solution and quicklime according to the original brine (sodium sulfate content) to achieve the refined brine index and stable production. Production experiment results: the sodium sulfate content in the original brine is not fixed, sometimes it is high nitrate brine, sometimes it is low nitrate brine. The addition of lime milk according to the calculation standard of sodium sulfate in the original brine is also a variable, the primary reaction and the secondary reaction are affected, the reaction efficiency of lime milk is very low, and the production operation is too complicated. The original brine is added with high nitrate solution and then lime milk. The addition amount is stable within the range, which can achieve stable production of primary reaction and secondary reaction, and improve the reaction efficiency of lime milk.

[0086] (2) The present invention recycles the secondary salt mud, and / or the quaternary salt mud, and / or the fifth salt mud and adds them to the third-stage reaction tank, and introduces excess flue gas. During the process, the flue gas preferentially reacts with the powdered salt mud, providing conditions for subsequent accelerated sedimentation. In addition, the first-stage refined brine and the salt mud are mixed and introduced into the excess flue gas, and the calcium ions are removed by using a high nitrate solution. The pH of the brine is then adjusted to 10.5-11.5 using the first-stage refined brine to obtain brine for brine purification, thereby realizing comprehensive resource utilization.

[0087] The third-stage reaction tank is fed with the first-stage refined halogen and excess flue gas to produce HCO3 - , the secondary salt mud, and / or the quaternary salt mud, and / or the fifth salt mud are recycled and added to the third-stage reaction tank, and excess flue gas is introduced. The calcium carbonate, the main component of the salt mud, is partially converted into calcium bicarbonate, and the amount of salt mud is reduced, especially the powdery granular salt mud is significantly reduced. Finally, high nitrate solution is added to reduce or remove Ca 2+ The setting of the three-stage reaction tank optimizes the mud composition and achieves unexpected technical effects: the amount of powdered salt mud in the mud is reduced, the mud sedimentation speed is accelerated, and the clarity of the refined brine is improved; the salt mud washing removes chloride ions and has a high dehydration rate. The purpose of setting the four-stage reaction tank is to utilize the OH in the first-stage refined brine. - The excess HCO3 produced by the third-stage reaction tank - Converted to CO3 2- , thereby further promoting the precipitation of calcium ions; the purpose of setting up a five-stage reaction tank is to contain too much OH in the fourth-stage refined brine. - and CO3 2- , which is not good for salt production, so it cannot be directly sent to the salt production system. Therefore, with the help of raw brine, on the one hand, excessive OH in the fourth-level refined brine is removed. - , and at the same time can convert Ca 2+ Mg 2+ , Fe 3+ Remove.

[0088] The present invention can realize the lime-flue gas method and the two-alkali continuous method-double membrane method (the two-alkali method corresponds to the five-stage reactor reaction) to promote coordinated development, brine purification to obtain salt mud, salt production to obtain external high nitrate liquid and double membrane method to obtain high nitrate liquid, combined with flue gas-denitrification-dust removal-desulfurization tower-compressor purification of flue gas, which is comprehensively utilized for brine purification, solves the problem of high content of powdered salt mud affecting sedimentation and brine quality, and greatly saves costs, and can also combine theory with practice. The lime flue gas method brine purification process formulates scientific and rigorous raw material (lime, high nitrate liquid and original brine) feeding and reaction methods, so that the raw material consumption is accurate and scientific, and zero soda consumption is achieved. In addition, the processing cost of salt mud and high nitrate liquid is reduced, the enrichment of impurity components in brine is reduced, the risk of affecting pipeline transportation of brine and backwater blockage is reduced, and the brine purification effect and product quality are improved. This technical resource is effectively utilized, the by-product processing cost is reduced, and energy conservation and emission reduction and resource recycling are achieved. It can be extended to the salt industry to help solve similar problems in other salt-making enterprises and will have a good typical demonstration effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0089] Figure 1 It is a system and method for resource coupling utilization of flue gas brine purification and salt production by-products in an embodiment of the present invention. DETAILED DESCRIPTION

[0090] In order to further understand the purpose, content and advantages of the present invention, the specific embodiments of the present invention are now described in detail as follows, but it is not limited to the following examples, and it is freely matched according to actual conditions. The endpoints and any values ​​of the scope disclosed in this article are not limited to the precise scope and value. For numerical ranges, between the endpoint values ​​of each scope, between the endpoint values ​​of each scope and a separate point value, and between separate point values, one or more new numerical ranges can be combined with each other, and these numerical ranges should be considered as specifically disclosed in this article.

[0091] A flue gas brine purification and resource coupling utilization system for salt production byproducts, comprising a first-level reaction tank, a second-level reaction tank, a second-level reaction tank, a third-level reaction tank, a fourth-level reaction tank, a fifth-level reaction tank and a high-nitrate liquid tank;

[0092] The first-stage reaction tank is provided with a first lime milk feed port, a first raw brine feed port, a first high nitrate liquid feed port, a first-stage refined brine discharge port, and a first-stage mud discharge port;

[0093] The second-level reaction tank is provided with a second lime milk feed port, a second raw brine feed port, a second high nitrate liquid feed port, a second-level refined brine discharge port, and a second-level mud discharge port;

[0094] The secondary reaction tank is provided with a second-level refined brine feed port connected to the second-level refined brine discharge port, and is also provided with a second-level refined brine discharge port, a second-level mud discharge port, and a second-level flue gas inlet port;

[0095] The three-stage reaction tank is provided with a three-stage flue gas inlet, a mud feed port, a first-stage refined brine feed port connected to the first-stage refined brine discharge port, a three-stage high nitrate liquid feed port, a three-stage mud discharge port and a three-stage refined brine discharge port. The mud feed port of the three-stage reaction tank is connected to the second-stage mud discharge port, and the three-stage high nitrate liquid feed port is connected to the high nitrate liquid outlet of the salt making system.

[0096] The four-stage reaction tank is provided with a three-stage refined brine feed port connected to the three-stage refined brine discharge port, a third-stage refined brine feed port connected to the first-stage refined brine discharge port, a four-stage mud discharge port and a four-stage refined brine discharge port, and the four-stage mud discharge port is connected to the mud feed port of the three-stage reaction tank;

[0097] The five-stage reaction tank is provided with a third raw brine feed port, a fourth-stage refined brine feed port connected to the fourth-stage refined brine discharge port, a fifth-stage mud discharge port and a fifth-stage refined brine discharge port, and the fifth-stage mud discharge port is connected to the mud feed port of the third-stage reaction tank;

[0098] When the system is working:

[0099] In the second-stage reaction tank, high nitrate solution and lime milk are added according to the sodium sulfate content in the original brine, and the second-stage refined brine components obtained after the reaction are controlled to be C(Na2SO4):18-22g / L, C(NaOH):1.2-1.6g / L, C(Ca 2+ )≤0.66g / L, C(NaCl):280-305g / L, S(suspended matter)≤1.8mg / L;

[0100] In the first stage reaction tank, high nitrate solution and lime milk are added according to the sodium sulfate content in the original brine, and the first stage refined brine composition obtained after the reaction is controlled to be C(SO4 2- )≥18.2g / L, C(NaOH)≥1.5g / L, C(Ca 2+ )≤0.32g / L, C(NaCl):275-305g / L, S(suspended matter)≤2.0mg / L;

[0101] Flue gas is introduced into the secondary reaction tank to control the C (Ca 2+ )≤12mg / L, C(Mg 2+ )≤4mg / L, C(Na2CO3)≤0.45g / L, C(NaOH)≤0.25g / L, C(SO4 2-)≤15.5g / L, C(NaCl):295-305g / L, S(suspended matter)≤0.8mg / L, at the same time, OH in the secondary refined brine - and Ca 2+ Total substance ratio n = [(nOH - / 2) / nCa 2+ ], 1.12≤n≤1.24;

[0102] Add the first stage refined halogen and excess flue gas to the three-stage reaction tank to obtain HCO3 - , put the secondary mud, and / or the quaternary mud, and / or the fifth mud into the third-stage reaction tank, pass in excess flue gas, pass in high nitrate solution after sufficient reaction, take the clear liquid to test C (Ca 2+ )≤0.08g / L, stop adding high nitrate solution, and after sufficient reaction, stand and separate to obtain third-grade refined brine and third-grade mud;

[0103] The flue gas is purified flue gas after denitration, dust removal, desulfurization and deammoniation;

[0104] The third-level refined brine is transported to the fourth-level reaction tank. At the same time, the fourth-level reaction tank uses the first-level refined brine to adjust the pH value to 10.2-10.8. After sufficient reaction, the fourth-level refined brine and the fourth-level mud are obtained;

[0105] All the fourth-level refined brine is transported to the fifth-level reaction tank, and the original brine is added to the fifth-level reaction tank at the same time. After sufficient reaction, the fifth-level refined brine is obtained. The composition of the fifth-level refined brine is C(Ca 2+ )≤10mg / L, C(Mg 2+ )≤4mg / L, C(Na2CO3)≤0.52g / L, C(NaOH)≤0.25g / L, S(suspended matter)≤0.8mg / L.

[0106] Furthermore, it also includes a salt-making system, which is provided with a refined brine feed inlet and a high nitrate liquid outlet, the refined brine feed inlet is connected to the secondary refined brine discharge port, and the high nitrate liquid outlet is connected to the high nitrate liquid feed inlet of the high nitrate liquid tank.

[0107] Furthermore, it also includes a double membrane system for membrane separation of the five-level refined brine. The specific double membrane system is provided with a five-level refined brine feed inlet and a high nitrate liquid outlet. The five-level refined brine feed inlet is connected to the five-level refined brine outlet, and the high nitrate liquid outlet is connected to the high nitrate liquid tank.

[0108] The present invention is further described in detail below in conjunction with embodiments:

[0109] Example 1

[0110] The main component of raw halogen is Ca 2+ :1.0~1.8g / L、Mg 2+:0.3~0.5g / L, Na2SO4≤13g / L, NaCl:285~308g / L, Ph:7.0~7.8.

[0111] The main components of high nitrate solution are NaCl: 270 ~ 290g / L, Na2SO4: 65 ~ 80g / L, CO3 2- ≤2.6g / L, OH - ≤1.2g / L, Ca 2+ ≤7mg / L, Mg 2+ ≤5.0mg / L;

[0112] Add raw brine to the first stage reaction tank (liquid level control 65-75%, the reaction tank (height 16m*diameter 16m, the same below) liquid level control is the percentage of the height of the added raw brine to the total height of the reaction tank), add lime milk (the amount of quicklime is controlled at 1.2-1.8g / 1L raw brine), and pass the high nitrate solution into the first stage reaction tank until the liquid level is controlled 90～94％ The stirring reaction temperature of the first-stage reaction tank is controlled to be 35-45°C, and the reaction time is 4-6h. After the reaction is completed, the first-stage refined brine and the first-stage mud are obtained by static separation (the separation method of the first-stage refined brine and the first-stage mud is a conventional separation method in the art, for example, separation can be performed by membrane filtration, or static sedimentation can be performed. Static sedimentation can be performed with or without the addition of flocculants. Adding an appropriate amount of flocculants can shorten the standing time. In this embodiment, static separation is performed without adding flocculants. The standing time is 3-5h. The first-stage reaction tank obtains a solid waste liquid (first-stage mud) with a content of 30-48% (the mass percentage of the separated first-stage mud in the total amount of material before static separation. Generally, the larger the amount of salt mud generated, the higher the salt mud content, the better the sedimentation effect, and the less suspended matter in the refined brine. The lower the salt mud content, the worse the sedimentation effect, and the more suspended matter in the refined brine). The first-stage refined brine component is C(SO4 2- )≥18.2g / L, C(NaOH)≥1.5g / L, C(Ca 2+ )≤0.32g / L, C(NaCl):275-305g / L, S(suspended matter)≤2.0mg / L. The main components of the first-level mud are CaSO4, Ca(OH)2, NaCl, Na2SO4, and trace Mg(OH)2.

[0113] Add raw brine to the second-stage reaction tank (liquid level control 75-85%, the liquid level of the reaction tank (height 16m*diameter 16m) is controlled as the percentage of the height of the added raw brine to the total height of the reaction tank), add lime milk (the amount of quicklime is controlled at 1.05-1.22g / 1L raw brine), and draw high nitrate liquid from the high nitrate liquid tank into the second-stage reaction tank until the liquid level is controlled 90 ～94％The components of lime milk are Ca(OH)2, NaCl, and NaOH; the components of original brine are NaCl, Na2SO4, trace amounts of calcium and magnesium; the components of high nitrate solution are NaCl, Na2SO4, trace amounts of Na2CO3, and NaOH. After mixing, the sodium sulfate content in the system is 19.5-24 g / L.

[0114] The second-stage reaction tank is controlled to control the stirring reaction temperature to be 35-45°C, the reaction time to be 4-7h, and after the reaction is completed, the reaction is allowed to stand for separation (in this embodiment, the flocculant is not added for standing separation, and the standing time is 3-5h) to obtain a solid waste (second-stage mud) with a content of 20-45% (the mass percentage of the separated second-stage mud to the total material before standing separation). The second-stage refined brine composition is C (Na2SO4): 18-22g / L, C (NaOH): 1.2-1.6g / L, C (Ca 2+ )≤0.66g / L, C(NaCl):295-305g / L, S(suspended matter)

[0115] ≤1.8mg / L, the second-level mud components are CaSO4, Ca(OH)2, NaCl, Na2SO4, Fe(OH)3, and trace Mg(OH)2. The second-level refined brine is transported to the secondary reaction tank, and the flue gas (the main components of the flue gas are N2, O2, and CO2) is introduced, and the reaction is carried out under stirring conditions (the reaction temperature is controlled to be 30-40°C, and the reaction time is 1.5-2.5h). After the reaction is completed, the solid waste liquid (secondary mud) is obtained by static separation (the present embodiment is static separation without adding flocculants, and the static separation time is 2-3h) with a content of 30-40%. The second-level refined brine components are C(Ca 2+ )≤12ppm, C(Mg 2+ )≤4ppm, C(Na2CO3)≤0.45g / L, C(NaOH)≤0.25g / L, C(SO4 2-)≤15g / L, C(NaCl):295-305g / L, S(suspended matter)≤0.8mg / L, the secondary refined brine is transported to the salt making system for salt making, and the high nitrate solution obtained by salt making is transported to the high nitrate solution tank (the salt making system described in the patent of the present invention is applicable to conventional salt making methods in the field, such as the double membrane salt making method described in the background technology. In this embodiment, the salt making system specifically includes transporting the secondary refined brine to the salt preheating system for preheating, and mixing it with the filtrate from the salt making centrifuge and then entering the hot pressing salt evaporation tank, and the mother liquor of the salt evaporation tank is transferred to another hot pressing salt evaporation tank. The brine evaporates and crystallizes in the hot-pressed salt evaporator, and the mother liquor is transferred to the first-effect salt-making flash tank. The salt precipitated from the salt legs of the autoclave enters the salt centrifuge for dehydration. The mother liquor from the first-effect salt-making flash tank is transferred to the vacuum salt-making evaporator for concentration and step-by-step salt precipitation. The concentrated mother liquor is transferred to the nitrate evaporator for concentration and nitrate precipitation after three-stage preheating. The final-effect evaporator discharges the salt slurry into the salt-nitrate separation system. The mother liquor of salt-making is heated and evaporated in the nitrate tank for nitrate precipitation. The nitrate precipitated from the nitrate legs is washed with brine and discharged into the nitrate centrifuge for dehydration. The mother liquor in the nitrate tank is transferred to the vacuum salt-making tank for continued salt precipitation, and finally the high nitrate liquid is separated and sent to the high nitrate liquid tank for standby use). It should be noted that the salt-making industry calls brine with a higher sodium sulfate content high nitrate liquid. The high nitrate liquid in the present invention can be a high nitrate liquid obtained by conventional processes in the art, such as salt-making mother liquor, effluent mother liquor, high nitrate liquid after nanofiltration, or other liquids with a higher sodium sulfate content. The high nitrate liquid obtained in the Chinese patent document (application number 202011352999.8) can also be used.

[0116] Add the first stage refined halogen and excess flue gas to the three-stage reaction tank to obtain HCO3 -, put the secondary mud, and / or the fourth mud, and / or the fifth mud into the third-stage reaction tank, and introduce excess flue gas,,, after the full reaction is completed (stirring the reaction at 25-35°C for 2-5h), the high nitrate liquid drawn from the high nitrate liquid tank is introduced into the third-stage reaction tank, and the reaction is stirred for 1.5-2h. After the reaction is completed, the solid waste liquid (third-stage mud) is allowed to settle and separate to obtain a solid waste liquid (third-stage mud) with a content of 35-48%. The experiment found that the mud after the reaction settles faster without adding flocculants, and generally it can be left to stand within 1 hour. The components of the third-stage mud are CaSO4, CaCO3, NaCl, and Na2SO4, and the components of the third-stage refined brine are NaHCO3, NaCl, Ca(HCO3)2, and Na2SO4. The separated third-stage refined brine contains a very low amount of suspended matter, and is much lower than the secondary refined brine. The tertiary refined brine is transported to the fourth-stage reaction tank. At the same time, the fourth-stage reaction tank uses the first-stage refined brine to adjust the pH value to 10.2-10.8, and stirs the reaction at 20-40°C for 0.5-1.5 hours. After the reaction is completed, it is allowed to stand (standing time is 0.5-1 hour). The solid waste liquid (fourth-stage mud) obtained by separation has an extremely low content of about 5%. At the same time, the content of suspended matter in the obtained fourth-stage refined brine is low, almost close to the tertiary refined brine. The components of the fourth-stage refined brine are Na2CO3, NaCl, NaOH, and Na2SO4, and the components of the fourth-stage mud are CaCO3, NaCl, and Na2SO4. The fourth-level mud is collected for recycling to the third-level reaction tank, and the fourth-level refined brine is all transported to the fifth-level reaction tank. At the same time, the original brine is added to the fifth-level reaction tank, and the reaction is heated and stirred at 30-45°C for 1.5-2h. After the reaction is completed, it is allowed to stand for sedimentation (standing time is 2-3h) and separated to obtain a solid waste liquid (fifth-level mud) with a content of about 3-6 times that of the fourth-level refined brine. The composition of the fifth-level refined brine is C (Ca 2+ )≤10ppm, C(Mg 2+ )≤4ppm, C(Na2CO3)≤0.52g / L, C(NaOH)≤0.25g / L, S(suspended matter)≤0.8mg / L, the composition of the five-pole mud is CaCO3, Mg(OH)2, NaCl, Na2SO4. It should be noted that: the amount of third-level mud obtained> the amount of second-level mud obtained> the amount of fifth-level mud obtained> the amount of fourth-level mud obtained, the content of suspended matter in refined brine is third-level refined brine < fourth-level refined brine < fifth-level refined brine < second-level refined brine, and the content of suspended matter in fifth-level refined brine is much lower than that in second-level refined brine. Since the amount of the fourth-level mud and the fifth-level mud is small, in order to save time in production, they can be accumulated by sedimentation for many times. When the amount of the fourth-level mud and the fifth-level mud reaches more than 30%, they will be discharged to the third-level reaction tank. Furthermore, since the amount of mud generated in the fourth-level reaction tank is extremely low, static sedimentation does not need to be carried out after the reaction in the fourth-level reaction tank is completed. Instead, all the materials are transferred to the fifth-level reaction tank and static sedimentation is carried out after the reaction in the fifth-level reaction tank is completed.

[0117] The fifth-level mud is collected for recycling to the third-level reaction tank. The fifth-level refined brine is passed through a double membrane system to obtain high nitrate liquid and low nitrate liquid (liquid salt). The high nitrate liquid is transported to the nitrate extraction system for nitrate extraction or the first-level reaction tank, and can also be sent to the high nitrate liquid tank for standby. The double membrane system is conventional in this field. For example, it can be a new preparation process for the co-production of refined salt and anhydrous nitrate for refined liquid salt for alkali production disclosed in Chinese patent document (application number CN201911314020.5).

[0118] The fifth-grade refined brine with Na2SO4≤23g / L is used to obtain a six-stage refined brine transportation and salt-making system, in which the fifth-grade refined brine with Na2SO4≥23g / L is adjusted to Na2SO4≤23g / L with low nitrate liquid and then transported to the salt-making system to obtain salt and high nitrate liquid.

[0119] Example 2

[0120] The main component of raw halogen is Ca 2+ :0.8~1.4g / L、Mg 2+ :0.3~0.5g / L, Na2SO4:13~18g / L, NaCl:285~308g / L, Ph:7.0~7.8.

[0121] The main components of high nitrate solution are NaCl: 270 ~ 290g / L, Na2SO4: 65 ~ 80g / L, CO3 2- ≤2.6g / L, OH - ≤1.2g / L, Ca 2+ ≤7mg / L, Mg 2+ ≤5.0mg / L;

[0122] Add raw brine to the first-stage reaction tank (the liquid level is controlled at 70-80%), add lime milk (the amount of quicklime is controlled at 1.2-1.8 g / 1L raw brine), and draw high nitrate liquid from the high nitrate liquid tank into the first-stage reaction tank until the liquid level is controlled at 90-94%. The first-stage reaction tank controls the stirring reaction temperature to be 35-45°C, and the reaction time is 4-6 hours. After the reaction is completed, stand and separate to obtain the first-stage refined brine and the first-stage mud (the separation method of the first-stage refined brine and the first-stage mud is a conventional separation method in the art, for example, separation by membrane filtration, or standing and settling, and the standing and settling can be selected to add or not add a flocculant, and adding an appropriate amount of a flocculant can shorten the standing time. This embodiment is a standing separation without adding a flocculant, and the standing time is 3-5 hours. The first-stage reaction tank obtains a solid waste liquid (first-stage mud) with a content of 30-48%, and the first-stage refined brine composition is C(SO4 2- )≥18.2g / L, C(NaOH)≥1.5g / L, C(Ca 2+)≤0.32g / L, C(NaCl):275-305g / L, S(suspended matter)≤2.0mg / L. The main components of the first-level mud are CaSO4, Ca(OH)2, NaCl, Na2SO4, and trace Mg(OH)2.

[0123] Add raw brine (liquid level controlled at 75-85%) to the second primary reaction tank, add lime milk (the amount of quicklime is controlled at 1.0-1.18 g / L), and pass the high nitrate liquid drawn from the high nitrate liquid tank into the second primary reaction tank until the liquid level is controlled at 90-94%. The components of lime milk are Ca(OH)2, NaCl, and NaOH, the components of raw brine are NaCl, Na2SO4, trace amounts of calcium, magnesium, and iron ions, and the components of high nitrate liquid are NaCl, Na2SO4, trace amounts of Na2CO3, and NaOH. After mixing, the sodium sulfate content in the system is 20-24 g / L.

[0124] The second-stage reaction tank is controlled to control the stirring reaction temperature to be 35-45°C, the reaction time to be 4-7h, and after the reaction is completed, the reaction is allowed to stand for separation (in this embodiment, no flocculant is added for standing separation, and the standing time is 3-5h) to obtain a solid waste (second-stage mud) with a content of 30-45%, and the second-stage refined brine composition is C(Na2SO4): 18-22g / L, C(NaOH): 1.2-1.6g / L, C(Ca 2 + )≤0.66g / L, C(NaCl):295-305g / L, S(suspended matter)

[0125] ≤1.8mg / L, the second-level mud composition is CaSO4, Ca(OH)2, NaCl, Na2SO4, trace Mg(OH)2. The second-level refined brine is transported to the secondary reaction tank, and the rest of the process is the same as Example 1.

[0126] Example 3

[0127] The main component of raw halogen is Ca 2+ :0.6~1.2g / L、Mg 2+ :0.3~0.5g / L, Na2SO4≥18g / L, NaCl:285~308g / L, Ph:7.0~7.8.

[0128] The main components of high nitrate solution are NaCl: 270 ~ 290g / L, Na2SO4: 65 ~ 80g / L, CO3 2- ≤2.6g / L, OH - ≤1.2g / L, Ca 2+ ≤7mg / L, Mg 2+ ≤5.0mg / L;

[0129] Add raw brine (liquid level controlled at 70-80%) to the first-stage reaction tank, add lime milk (the amount of quicklime is controlled at 1.2-1.6 g / L), and introduce high nitrate solution into the first-stage reaction tank until the liquid level is controlled at 90-94%. The main components of lime milk are Ca(OH)2, NaCl, and NaOH, the main components of raw brine are NaCl, Na2SO4, trace amounts of calcium and magnesium, and the main components of high nitrate solution are NaCl, Na2SO4, trace amounts of Na2CO3, and NaOH. The first-stage reaction tank controls the stirring reaction temperature to be 35-45°C, and the reaction time is 4-6h. After the reaction is completed, the first-stage refined brine and the first-stage mud are obtained by static separation (the separation method of the first-stage refined brine and the first-stage mud is a conventional separation method in the art, for example, separation by membrane filtration, or static sedimentation, static sedimentation can be selected to add or not add flocculant, adding an appropriate amount of flocculant can shorten the static time, and the present embodiment is static separation without adding flocculant, and the static time is 3-5h. The first-stage reaction tank obtains a solid waste liquid (first-stage mud) with a content of 30-48%, and the first-stage refined brine composition is C(SO4 2- )≥18.2g / L, C(NaOH)≥1.5g / L, C(Ca 2+ )≤0.32g / L, C(NaCl):275-305g / L, S(suspended matter)≤2.0mg / L. The main components of the first-level mud are CaSO4, Ca(OH)2, NaCl, Na2SO4, and trace Mg(OH)2.

[0130] Add raw brine (liquid level controlled at 75-85%) to the second primary reaction tank, add lime milk (the amount of quicklime is controlled at 0.95-1.15 g / L), and draw high nitrate liquid from the high nitrate liquid tank into the second primary reaction tank. The components of lime milk are Ca(OH)2, NaCl, and NaOH, the components of raw brine are NaCl, Na2SO4, trace amounts of calcium, magnesium, and iron ions, and the components of high nitrate liquid are NaCl, Na2SO4, trace amounts of Na2CO3, and NaOH. After mixing, the sodium sulfate content in the system is 20-24 g / L. The second-stage reaction tank is controlled to control the stirring reaction temperature to be 35-45°C, the reaction time to be 4-7h, and after the reaction is completed, the reaction is allowed to stand for separation (in this embodiment, no flocculant is added for standing separation, and the standing time is 3-5h) to obtain a solid waste (second-stage mud) with a content of 30-45%, and the second-stage refined brine composition is C(Na2SO4): 18-22g / L, C(NaOH): 1.2-1.6g / L, C(Ca 2+)≤0.66g / L, C(NaCl):295-305g / L, S(suspended matter)≤1.8mg / L, the second-stage mud composition is CaSO4, Ca(OH)2, NaCl, Na2SO4, trace Mg(OH)2. The second-stage refined brine is transported to the secondary reaction tank, and the flue gas (the main components of the flue gas are N2, O2, CO2) is introduced, and the rest of the process is the same as in Example 1.

[0131] The above is only a preferred specific implementation of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field within the technical scope disclosed by the present invention, according to the technical solution and its concept of the present invention, shall be covered within the protection scope of the present invention. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0132] In the description of the present invention, the terms "first", "second", "primary", "secondary", "tertiary", "quaternary", "fifth", etc. are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, features defined as "first", "second", "primary", "secondary", "tertiary", "quaternary", "fifth", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0133] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection or a detachable connection, and it can be connected through a pipeline, for example, the pipeline is used to connect the reaction tanks at both ends of the pipeline, and for the purpose of use, an intermediate storage tank can be further arranged on the pipeline to serve as a temporary storage tank for the pipeline transport medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

Claims

1. A flue gas brine purification and resource coupling utilization system for salt production byproducts, characterized by: It includes a first-level reaction tank, a second-level reaction tank, a second-level reaction tank, a third-level reaction tank, a fourth-level reaction tank, a fifth-level reaction tank and a high nitrate liquid tank; The first-stage reaction tank is provided with a first lime milk feed port, a first raw brine feed port, a first high nitrate liquid feed port, a first-stage refined brine discharge port, and a first-stage mud discharge port; The second-level reaction tank is provided with a second lime milk feed port, a second raw brine feed port, a second high nitrate liquid feed port, a second-level refined brine discharge port, and a second-level mud discharge port; The secondary reaction tank is provided with a second-level refined brine feed port connected to the second-level refined brine discharge port, and is also provided with a second-level refined brine discharge port, a second-level mud discharge port, and a second-level flue gas inlet port; The high nitrate liquid tank is provided with a high nitrate liquid feed inlet and a high nitrate liquid outlet, and the high nitrate liquid outlet is connected to the first high nitrate liquid feed inlet and the second high nitrate liquid feed inlet respectively; The three-stage reaction tank is provided with a three-stage flue gas inlet, a mud feed port, a first-stage refined brine feed port connected to the first-stage refined brine discharge port, a three-stage high nitrate liquid feed port, a three-stage mud discharge port and a three-stage refined brine discharge port. The mud feed port of the three-stage reaction tank is connected to the second-stage mud discharge port, and the three-stage high nitrate liquid feed port is connected to the high nitrate liquid outlet of the salt making system. The four-stage reaction tank is provided with a three-stage refined brine feed port connected to the three-stage refined brine discharge port, a third-stage refined brine feed port connected to the first-stage refined brine discharge port, a four-stage mud discharge port and a four-stage refined brine discharge port, and the four-stage mud discharge port is connected to the mud feed port of the three-stage reaction tank; The five-stage reaction tank is provided with a third raw brine feed port, a fourth-stage refined brine feed port connected to the fourth-stage refined brine discharge port, a fifth-stage mud discharge port and a fifth-stage refined brine discharge port, and the fifth-stage mud discharge port is connected to the mud feed port of the third-stage reaction tank; When the system is working: In the second-stage reaction tank, high nitrate solution and lime milk are added according to the sodium sulfate content in the original brine, and the second-stage refined brine components obtained after the reaction are controlled to be C(Na2SO4):18-22g / L, C(NaOH):1.2-1.6g / L, C(Ca 2+ )≤0.66g / L, C(NaCl):280-305g / L, S(suspended matter)≤1.8mg / L; In the first stage reaction tank, high nitrate solution and lime milk are added according to the sodium sulfate content in the original brine, and the first stage refined brine composition obtained after the reaction is controlled to be C(SO4 2- )≥18.2g / L, C(NaOH)≥1.5g / L, C(Ca 2+ )≤0.32g / L, C(NaCl):275-305g / L, S(suspended matter)≤2.0mg / L; Flue gas is introduced into the secondary reaction tank to control the C (Ca 2+ )≤12mg / L, C(Mg 2 + )≤4mg / L, C(Na2CO3)≤0.45g / L, C(NaOH)≤0.25g / L, C(SO4 2- )≤15.5g / L, C(NaCl):295-305g / L, S(suspended matter)≤0.8mg / L, at the same time, OH in the secondary refined brine - and Ca 2+ Total substance ratio n = [(nOH - / 2) / nCa 2 + ], 1.12≤n≤1.24; Add the first stage refined halogen and excess flue gas to the three-stage reaction tank to obtain HCO3 - , put the secondary mud, and / or the quaternary mud, and / or the fifth mud into the third-stage reaction tank, introduce excess flue gas to make it fully react, then introduce high nitrate solution, take the clear liquid to test C (Ca 2+ )≤0.08g / L, stop adding high nitrate solution, and after sufficient reaction, stand and separate to obtain third-grade refined brine and third-grade mud; The flue gas is purified flue gas after denitration, dust removal, desulfurization and deammoniation; The third-level refined brine is transported to the fourth-level reaction tank. At the same time, the fourth-level reaction tank uses the first-level refined brine to adjust the pH value to 10.2-10.

8. After sufficient reaction, the fourth-level refined brine and the fourth-level mud are obtained; All the fourth-level refined brine is transported to the fifth-level reaction tank, and the original brine is added to the fifth-level reaction tank at the same time. After sufficient reaction, the fifth-level refined brine is obtained. The composition of the fifth-level refined brine is C(Ca 2+ )≤10mg / L, C(Mg 2+ )≤4.0mg / L, C(Na2CO3)≤0.52g / L, C(NaOH)≤0.25g / L, S(suspended matter)≤0.8mg / L.

2. The flue gas brine purification and resource coupling utilization system of salt production byproducts according to claim 1 is characterized by: It also includes a double membrane system for membrane separation of refined brine. When Na2SO4≤23g / L in the fifth-grade refined brine, the fifth-grade refined brine is transported to the salt-making system. When Na2SO4>23g / L in the fifth-grade refined brine, it is divided into two streams, one of which is sent to the double membrane system for membrane separation to obtain low nitrate liquid, which is then mixed with the other fifth-grade refined brine to adjust Na2SO4≤23g / L, and then transported to the salt-making system to obtain salt and high nitrate liquid.

3. The flue gas brine purification and resource coupling utilization system of salt production byproducts according to claim 1 is characterized by: It also includes a salt-making system, which is provided with a refined brine feed inlet and a high nitrate liquid outlet, wherein the refined brine feed inlet is connected to a secondary refined brine discharge port, and the high nitrate liquid outlet is connected to a high nitrate liquid feed inlet of a high nitrate liquid tank.

4. A flue gas brine purification and resource coupling utilization method of salt production byproducts, characterized by: The method is based on the flue gas brine purification and resource coupling utilization system of salt production byproducts according to claim 1 or 2, and comprises the following steps: Add raw brine, lime milk and high nitrate solution into the first-stage reaction tank, adjust the sodium sulfate content in the system to ≥26.9g / L, and add lime milk in an amount of 1.2-1.8g / L expressed by the theoretical concentration of quicklime in the system. After sufficient reaction, stand and separate to obtain the first-stage mud and the first-stage refined brine; Add raw brine, lime milk and high nitrate solution into the second-level reaction tank, adjust the sodium sulfate content in the system to 19.5-24g / L, and the amount of lime milk added is 0.95-1.22g / L expressed by the theoretical concentration of quicklime in the system. After sufficient reaction, stand and separate to obtain the second-level mud and the second-level refined brine; The second level refined brine is transported to the second level reaction tank, where flue gas is introduced and fully reacted under stirring conditions. After the reaction is completed, the reaction is allowed to stand and separate to obtain second level mud and second level refined brine; Add the first stage refined halogen and excess flue gas to the three-stage reaction tank to obtain HCO3 - , put the secondary mud, and / or the quaternary mud, and / or the fifth mud into the third-stage reaction tank, introduce excess flue gas, stir the reaction thoroughly, then introduce high nitrate solution, take the clear liquid to test C (Ca 2+ )≤0.08g / L, stop adding high nitrate solution, let stand and separate after the reaction is completed, and obtain third-grade refined brine and third-grade mud; The third-level refined brine is transported to the fourth-level reaction tank. At the same time, the fourth-level reaction tank uses the first-level refined brine to adjust the pH value to 10.2-11.

3. After sufficient stirring and reaction, it is allowed to stand and separate to obtain the fourth-level refined brine and the fourth-level mud. All the fourth-level refined brine is transported to the fifth-level reaction tank, and the original brine is added to the fifth-level reaction tank at the same time. After sufficient stirring for reaction, the fifth-level refined brine is obtained by standing and separating.

5. The method for flue gas brine purification and resource coupling utilization of salt production byproducts according to claim 4 is characterized by: The specific method of adding raw brine, lime milk and high nitrate solution in the second primary reaction tank is: When the sodium sulfate content in the original brine is lower than 13g / L, high nitrate solution is added to make the sodium sulfate content 19.5-24g / L. The final calculation shows that the calcium ion is no higher than 0.66g / L, the amount of lime milk is controlled at 1.05-1.22g / L, and the carbonization endpoint pH is controlled at 9.0-9.5; When the sodium sulfate content in the original brine is between 13 and 18 g / L, high nitrate solution is added to make the sodium sulfate content 19.5 to 24 g / L. The final calculation shows that the calcium ion is no higher than 0.60 g / L, the amount of lime milk is controlled at 1.0 to 1.18 g / L, and the carbonization endpoint pH is controlled at 8.9 to 9.

6. When the sodium sulfate content in the original brine is higher than 18g / L, high nitrate solution is added to make the sodium sulfate content 19.5-24g / L. The final calculation shows that the calcium ion is no higher than 0.58g / L, the feeding amount of lime milk is controlled at 0.95-1.15g / L, and the carbonization endpoint pH is controlled at 9.0-9.

6.

6. The method for flue gas brine purification and resource coupling utilization of salt production byproducts according to claim 4 is characterized by: The specific method of adding raw brine, lime milk and high nitrate solution in the second primary reaction tank is: When the content of sodium sulfate in the raw brine is 16g / L, the amount of quicklime added is 1.3 times the normal amount of quicklime added, and the control point of the pH value at the end of the carbonization reaction is 9.0-9.6; When the sodium sulfate content in the raw brine is 18g / L, the quicklime feeding amount is 1.15 times the normal quicklime feeding amount, and the control point of the pH value at the end point of the carbonization reaction is 9.0-9.6; When the content of sodium sulfate in the original brine is 20g / L, the amount of quicklime added is 1.0 times the normal amount of quicklime added, and the pH value is controlled at 9.5-10; When the sodium sulfate content in the original brine is 22g / L, the amount of quicklime added is 0.95 times the normal amount of quicklime added, and the pH value is controlled at 9.5-10.5; When the sodium sulfate content in the original brine is 24g / L, the amount of quicklime added is 0.9 times the normal amount of quicklime added, and the pH value is controlled at 9.8-10.8; The normal feeding amount of the quicklime is 1.05-1.22 g / L.

7. The method for flue gas brine purification and resource coupling utilization of salt production byproducts according to claim 4 is characterized by: The first primary reaction tank controls the reaction temperature to be 35-45°C and the reaction time to be 4-6h; and / or, the second primary reaction tank controls the reaction temperature to be 35-45°C and the reaction time to be 4-7h; And / or, the reaction temperature is controlled to be 25-35°C before the high nitrate solution is introduced into the tertiary reaction tank, the reaction time is 2-5 hours, and the reaction is continued for 1.5-2 hours after the high nitrate solution is introduced; And / or, the reaction temperature of the fourth-stage reaction tank is controlled to be 20-40° C. and the reaction time is 0.5-1.5 h; And / or, the five-stage reaction tank controls the reaction temperature to be 30-45° C. and the reaction time to be 1.5-2 h.

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