Industry News » Difficulties and Technical Analysis of Chemical Waste Salt Treatment in Fine Chemical Industrial Park


Difficulties and Technical Analysis of Chemical Waste Salt Treatment in Fine Chemical Industrial Park


The fine chemical industrial zone mainly concentrates the fine chemical industry with higher added value, wider user coverage and greater development potential. The fields involved also include fine chemical products such as biochemicals, electronic chemicals, food additives, etc. , Has brought great economic and social benefits to regional industry and economic development.


However, along with the rapid development of industrial parks, wastewater with complex components and higher concentrations of salt and pollutants was also produced. In order to promote the construction and development of China's resource-saving and environment-friendly parks, and to ensure the continuous improvement of the project construction and industrial chain during the 13th Five-Year Plan period, follow the concept of green development and carry out in-depth treatment of chemical waste salts in the park. Important topics and trends in the development of fine chemical industrial parks.


Analysis on the Necessity of Governance of Fine Industrial Park


First, the governance of the fine chemical industrial park helps protect the health of residents. The industrial waste gas and salty sewage discharged during the development of the fine chemical industrial park will cause a certain degree of pollution to the surrounding environment, and also pose a certain threat to the health of nearby residents. Therefore, the governance of the industrial park Helps protect the health of residents.


Secondly, the waste resource utilization of the fine chemical industrial park, especially for the fine chemical industry, as a major producer of waste salt, its treatment and disposal are currently the bottlenecks restricting the development of the park. If the harmful and toxic substances in the chemical wastewater can be recovered, the waste can be recycled into resources, and when pollution is treated, not only good social benefits but also good economic benefits can be achieved. Third, for the fine chemical industrial park, if it wants to achieve longer-term development, it must combine economic development with environmental development. Only by technologically treating the waste salt and wastewater in the park can the level of economic greening be promoted. .


Difficulties in the treatment of waste salt in the fine chemical industrial park


First, the technical difficulty is greater, and the input and output are disproportionate. There are greater difficulties in the treatment of industrial pollution, and it is technically less replicable, and the input and output are not proportional. As far as enterprises are concerned, if they want to expand their scale quickly, they need a model that can be quickly copied; and from the perspective of fine chemicals, even the same product adopts different processes or applies the same process. There are differences in drainage at different times, mainly due to the greater technical difficulty, which results in a larger input but a small output.


Secondly, for companies, they pay too much attention to the maximization of profits. Many chemical companies prefer to dilute the saline wastewater and let the sewage treatment plant take over, rather than spend a higher cost on treatment. Thirdly, for the management of fine chemical industrial parks, the first is to replace toxic and harmful raw materials from the source to achieve cleaner production, and the most important of these is to do a good job of salt discharge. Too much salt may cause the death of biological bacteria, and the biochemical system is difficult to operate normally. Therefore, in order to ensure the normal operation of the centralized sewage treatment plant, the salt concentration is usually required to be less than 5%. However, sewage treatment plants usually reject high-salt wastewater, so it will cause a lot of waste salt to be hoarded in the enterprise workshop, making its disposal problem difficult to control. Therefore, as far as biotechnology is concerned, the core is to treat high-salt wastewater, thereby cultivating salt-tolerant bacteria, and promoting the improvement of the salt tolerance of biological bacteria. However, as a whole, the application of biotechnology in the treatment of high-salt wastewater is still very few.


Clean production process method for recycling waste salt in fine chemical industrial park


Recovery and treatment of inorganic waste salt in fine chemical industrial park


1. Recycling treatment by recrystallization For the recovery of waste salt after quenching, the salt bath used for quenching usually consists of NaCl and KCl. The waste salt after quenching cannot be used directly, and if it is discarded, it will not only be very wasteful, but will also affect the surrounding environment to a certain extent. Therefore, the process of "dissolving → filtering → heating and evaporating crystallization → drying" can be used to realize the recrystallization and recovery of waste salt, so that the "waste" salt is not wasted and meets the standard of good salt for heat treatment and quenching.


2. Neutralization and detoxification treatment By neutralizing and detoxification treatment of waste cyanide salt, the purpose is to avoid the pollution and diffusion of waste cyanide salt, while treating waste cyanide salt and ferrous sulfate in hot state and treating it thoroughly After the reaction, the cyanide is destroyed, and non-toxic gases, carbonates, iron, sulfur and other substances are produced. After that, it can be treated in cold state or diluted by waste water, which can be consistent with the national cyanide-containing sewage discharge standards. 3. Treatment by precipitation and recrystallization In the process of titanium dioxide production, a lot of chlorinated waste residues will be generated. The treatment is mainly to dissolve the waste salts through water, and then throw it into the lye Analysis, at this time, some metals will form hydroxides and precipitate. As the main component of the aqueous solution, NaCl is separated from the slag and water, and the solution is recovered by drying salt, and the remaining harmless sediment is sent to the slag yard Be processed.


Second, the recovery and treatment method of waste salt containing organic matter in the fine chemical industrial park


1. Recycling of resources through high-temperature treatment method In the process of organic synthesis, there will be a lot of weak alkaline salts (such as Na2CO3, K2CO3, etc.) as a catalyst for chemical reactions, these chemical reactions usually produce a lot Salt slag, because salt slag has a very complex composition, it is difficult to deal with it directly. Through the use of washing and vacuum drying, the organic solvent and monoether in the etherified waste salt residue generated in the furanphenol production process can be recycled, which can not only reduce the pollution of the waste salt residue to the environment, but also go to the resource recycling Purpose of use.


2. Treatment of waste salt by graded critical carbonization method. Graded critical carbonization method, low-temperature graded carbonization technology, combined with the critical softening point and critical carbonization point of different salt residues to select different carbonization methods and temperatures, so as to carbonize at high temperature Problems such as softening of waste salt, uneven carbonation, equipment bonding, and impurity removal in the treatment of waste salt in the process of direct and high-temperature treatment of waste salt can be solved.


3. Purification of by-product salt through salt washing method and advanced oxidation technology Salt is used to clean the saturated by-product solution, and the heavy metals and organic matter in the by-product are dissolved in the cleaning solution to achieve the purpose of purifying the by-product. In addition, on the premise of washing saturated by-product salts, adding chemical oxidants such as sodium hypochlorite, hydrogen peroxide, ozone, etc., can oxidize organic pollutants, and then purify by-product salts.


4. After the soda ash method is used to make the salt residue into a saturated saline solution, ammonia gas and carbon dioxide are passed under certain conditions or solid ammonium carbonate is directly added to the solid sodium bicarbonate. Separate and wash it, and then obtain high soda ash by high temperature decomposition. The separation mother liquor mainly contains ammonium chloride. After adding salt slag to it, freeze and precipitate ammonium chloride and recycle to the alkali production process. The soda ash production method is very suitable for companies that need ammonium chloride or soda ash, and can make full use of waste residue resources to achieve the purpose of circular economy.


Clean production process method for chemical waste salt treatment in fine chemical industrial park


In order to ensure the stable operation of the desalination unit in the fine chemical industrial park, the hardness of the water needs to be removed. Based on this, the hardness of water can be removed by chemical methods, boiling methods, electrodialysis methods, chemical methods, ion exchange methods, nanofiltration / reverse osmosis membrane methods, and the like.


Among them, the chemical method is the chemical softening method, generally using lime-soda ash softening method to remove the hardness in the water. The boiling method only removes the temporary hardness of the water; the ion exchange method is for high hardness water treatment, has a higher regeneration frequency, consumes a lot of demineralized water, and generates a lot of wastewater; nanofiltration / reverse The permeable membrane method and electrodialysis method are more suitable for the treatment of low-hardness water. If the hardness is too high, it is easy to cause scaling; therefore, considering the actual water quality, the lime-soda soda softening method can be selected for hardening treatment, and also selected At present, the most widely used range of high-efficiency clarifiers is to process, mix, flocculate and settle them.


In order to ensure that the SDI of the reverse osmosis influent does not exceed 3, a multi-media filtration + ultrafiltration high-efficiency clarification process can be adopted to penalize the turbidity and suspended matter in the effluent of the treatment tank. Using the reverse osmosis process, although most of the hardness in the water has been removed based on the front-end lime softening system, the removal effect is limited, and the lower the hardness, the worse the treatment effect.


Therefore, in actual engineering projects, in order to reduce operating costs, it is necessary to strictly control the amount of lime added, which will cause the hardness of the effluent of the softened lime to be in the range of 200-300mg / L.


In order to reduce the fouling tendency of the reverse osmosis device, the secondary softening treatment is performed before the reverse osmosis system is adopted. Through the use of a sodium ion exchanger, the hardness of the reverse osmosis system is controlled to the range of 50mg / L to ensure the penetration The anti-reflection system can operate normally.


    
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