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Green production, coordinated development and efficient utilization of resources are the inevitable requirements of industrial development. As a chemical enterprise with the mission of "green chemistry creates a better life", Xin'an group has been carrying out continuous technological innovation in the field of glyphosate and organosilicon production. After more than 20 years of continuous research, Xin'an group has realized the collaborative production of glyphosate and organosilicon, solved the problem of high-value utilization of by-product dilute hydrochloric acid, and significantly increased the utilization rate of chlorine to 97%; Two key technologies have been developed, i.e. directional transformation of high salt containing organic phosphorus wastewater into phosphate products and directional transformation of by-products containing silicon chloride into organosilicon products. The comprehensive utilization of silicon element has been increased to 96% and the recycling utilization rate of phosphorus element has been increased to 94%. The three major cycles of chlorine, phosphorus and silicon in the collaborative production of organic phosphorus and organosilicon have been established in the world.
Building bridge industry with chlorine element to achieve more than 1.6 billion yuan
China has long paid attention to technological innovation in a single industry in order to reduce production costs and "three wastes". However, there is still a gap in China in developing the design and development of collaborative utilization of resources among industrial chains, integrating production technology, key equipment, environmental protection treatment and even information technology to jointly build a green and intelligent system at the district level.
In order to make a breakthrough in this field, Xin'an group uses the methods of element flow analysis, value chain analysis and life cycle evaluation to analyze the multi-scale flow characteristics of phosphorus, sulfur, chlorine, silicon and sodium and the migration and transformation rules among the multi-media, so as to establish the optimal control model of element flow in the park and provide scientific basis for pollution prevention and control and green development decision-making in the whole process. A breakthrough has been made in the internal recycling of core element chlorine for the first time.
Chlorinated compounds are commonly used in chemical production, but most of the chlorine brought in is converted into hydrochloric acid. In 2017, the amount of by-product hydrochloric acid in China has exceeded 70% of the normal output of hydrochloric acid in China, and the output has exceeded 4 million tons. Although by-product hydrochloric acid can be further used, due to the limitations of concentration, impurity composition, region and season, the digestion and utilization of a large number of by-product hydrochloric acid has become a common problem restricting the development of chlor alkali, polyurethane, pesticide, medicine and many other industries.
The conventional utilization method is to use the by-product hydrochloric acid to deeply analyze the hydrogen chloride as the feed gas of subsequent products or convert it into pure hydrochloric acid. A large amount of steam is needed for deep analysis, and the energy consumption is high, and the hydrogen chloride produced by the analysis often contains more impurities, which is difficult to meet the requirements of subsequent application. Moreover, a large number of secondary pollutants such as calcium chloride or sulfuric acid will be produced in the existing process, resulting in low comprehensive added value and poor economic performance of the technology application.
In the production of organosilicon monomer, dimethyldichlorosilane is prepared by reaction of chloromethane with metal silicon powder, and then the dimethylcyclosiloxane mixture (DMC) is obtained by hydrolysis under normal pressure, in which the chlorine element brought by chloromethane is almost completely converted into hydrogen chloride and produced in the form of by-product dilute salt acid. Chlorine only plays a role of "leading through the needle" in the production. How to effectively treat and efficiently use it has become a key link in the sustainable production of organosilicon.
Glyphosate, another industrial herbicide of Xin'an group, needs hydrochloric acid as raw material. Some chlorine elements in hydrochloric acid through hydrolysis process will be converted into by-product chloromethane. If it can be used in organosilicon production after recovery and refining, an industrial cycle can be formed. However, the hydrochloric acid used in glyphosate production has higher requirements on organosilicon impurities, especially the content of siloxane oligomer, which is easy to polymerize in the pipeline, resulting in pipeline blockage and unqualified glyphosate product quality. In addition, the synthesis of chloromethane and the production of trichlorosilane also need high purity hydrogen chloride gas.
Considering the relationship between glyphosate and organosilicon production, Xin'an group found that chlorine is the key bridging element for industry collaboration. Through the innovation of the key technology of by-product hydrochloric acid recycling, the collaborative production of the two industries can be realized. For this reason, they cooperated with Zhejiang University to redesign the technology of comprehensive utilization of organosilicon by-product monomers based on the concept of industrial collaboration and made major breakthroughs
Through the development and design of silicone Pressurized Hydrolysis Process and core equipment, the joint research team directly escaped most of the hydrogen chloride produced in the silicone hydrolysis process with gas, avoiding the generation of dilute hydrochloric acid, and solved the hydrogen chloride corrosion problem of the core hydrolysis equipment with stainless steel composite material in the process; Furthermore, the content of siloxane oligomer in hydrogen chloride gas was reduced from 0.1% to 0.005% by multi-stage purification processes such as washing, adsorption and flocculation sedimentation. The strict requirements for impurity control in hydrogen chloride gas in the production and application of trichlorosilane and chloromethane were solved. Compared with the traditional deep analysis technology, the steam consumption of the above method is reduced by 94%, and there is no secondary pollution.
By using this technology, Xin'an group has built and put into use four sets of 40000 t / a industrial units, which have realized the recycling of hydrogen chloride in the coordinated production of organophosphorus and organosilicon industry, making the recycling rate of the whole chlorine element in the industry reach 97%, significantly improving the economy of recycling the original low-grade by-product hydrochloric acid, and the converted benefit can exceed 300 yuan / T DMC; The output of diluted hydrochloric acid has been reduced by more than 3 million tons, and the disposal cost has been reduced by more than 1.6 billion yuan.
Break through the common problems in the industry and realize the directional transformation of two core technologies
On the basis of realizing the internal circulation of chlorine elements and based on the characteristics of the flow and transformation of phosphorus, sulfur, chlorine, silicon and other multi-element elements in the park, Xin'an group has gradually built an ecological industrial system with multi products and multi industry links, overcome the common technical problems in the industry, and realized the high-value recycling of phosphorus and silicon elements.
The lack of economic treatment technology of organic phosphorus wastewater, especially high concentration of salt containing organic phosphorus and low-grade by-product hydrochloric acid, has become a major problem affecting our environmental safety. Glyphosate is the largest organic phosphorus chemical product in China, with a total annual production capacity of about 1 million tons. The glyphosate mother liquor produced is a typical high concentration organic phosphorus containing wastewater, and the lack of effective treatment technology restricts the development of the industry. Organosilicon is an important strategic new material in China, with an annual production capacity of nearly 3 million tons. How to effectively use the large amount of hydrochloric acid and the dangerous by-products of chlorosilicon produced in the production has also become the bottleneck of the industry development. In view of the unbalanced utilization of phosphorus and silicon in the collaborative production, Xin'an group has successfully developed two core technologies, i.e. directional conversion and recovery of phosphate from organic phosphorus wastewater and directional conversion of organosilicon by-products containing silicon chloride, to realize the integrated recycling of phosphorus, silicon chloride and support the further development of low-carbon recycling industry.
Among them, the technology of directional conversion and recovery of phosphate from organic phosphorus wastewater solves the problem of unbalanced utilization of phosphorus in collaborative production. Its outstanding performance is that only 63% - 66% of the phosphorus brought into the raw material enters into the product glyphosate, and nearly 40% of the phosphorus element is not utilized, which mainly exists in the glyphosate mother liquor. Nearly 5 tons of wastewater (glyphosate mother liquor) with high salt and high concentration produced by 1 ton of glyphosate production. Based on the actual annual output of 450000 tons / year in China, more than 2 million tons of high salt and phosphorus containing wastewater (glyphosate mother liquor) are produced. Because of the adverse impact on the soil and other environment, it is forbidden to use the mother liquor to prepare 10% glyphosate in 2009. How to deal with this problem has become a bottleneck restricting the development of the industry. Although many domestic scientific research institutions have developed methods for the treatment of organic phosphorus wastewater, they are basically established in the primary stage such as oxidation pretreatment. Due to the harsh technical conditions and high requirements for equipment materials, there are still some problems in industrialization.
In view of the characteristics of glyphosate mother liquor, such as large output, complex composition and difficulty in direct utilization, Xin'an group has successively tried membrane separation and reuse, conversion of sodium chloride into ammonium chloride by ammonia method and collaborative disposal by cement kiln, but failed to achieve success. However, in the collaborative treatment of cement kiln, the technical personnel found that the setting time of cement after treatment was significantly prolonged, which indicated that the product of high-temperature treatment had the component of cement retarding effect. After further analysis, it was found that the main product was a certain form of phosphate. On this basis, they targeted to explore the directional transformation process of glyphosate mother liquor phosphorus resource recovery, and finally formed a universal new method of organic phosphorus wastewater resource treatment, and obtained a number of invention patents.
First of all, the new method is aimed at the complex high phosphorus organic waste liquid, using liquid chromatography, mass spectrometry, nuclear magnetic resonance and other analytical methods to determine and establish the main components and analytical methods of typical organic phosphorus waste liquid. Then, according to the properties of the main components of organic phosphorus waste liquid, the chemical catalytic oxidation method is invented to pretreat the organic phosphorus waste liquid, so as to realize the controllable composition of the waste liquid elements, which is for the follow-up Directional transformation provides the best raw materials.
Secondly, in the pretreated organic phosphorus wastewater, phosphorus exists in the form of a variety of compounds, and the physical and chemical properties are quite different, so it is difficult to recycle it by conventional separation methods. They adopt the method of integrated pyrolysis, oxidation, conversion, polymerization and other reaction units as a whole to realize the rapid and directional conversion of various forms of phosphorus compounds into a single target product. At the same time, through energy-saving technologies such as waste heat recovery, they solve the problem of harmless treatment of waste liquid and improve the economic value of waste liquid. The transformation products can be oriented and controlled according to the market demand, covering a variety of phosphate and polyphosphate products. The directional transformation patent technology has opened up the economic recovery route of phosphorus compounds in high phosphorus organic waste liquid.
Thirdly, they solved the core technical problem of high efficiency one-time conversion of low concentration complex organophosphorus compounds to target products by continuous oxidation polymerization impurity removal reverse hydrolysis flash nucleation gradient cooling crystallization complete set of phosphorus resource recovery technology. The one-time conversion rate can be as high as 96%; In addition, the key technical problem of sodium chloride high-temperature wall hanging in directional converter is solved by designing the integral zone control technology of core components of dual flow internal mixing atomization, flow field and temperature field, and the production efficiency is increased by 50% compared with the initial one.
Finally, they refined the conversion products to obtain high-grade industrial polyphosphate / phosphate products, realized the high resource utilization of organic phosphorus waste liquid, and further used hydrolysis, re decomposition, extraction, polymerization and other methods to further process the obtained industrial polyphosphate / phosphate, to obtain sodium pyrophosphate, sodium tripolyphosphate, sodium hexametaphosphate, potassium phosphate A series of industrial phosphate products, such as ammonium phosphate, enrich the types of resource-based products and improve the added value.
All of the above technologies have been industrialized. The comprehensive utilization rate of phosphorus in glyphosate industry has been increased from 63% to 66% to more than 94%. It can also be used in other industries to deal with high phosphorus organic waste liquid. It has been listed as the key support technology for environmental protection and clean production in China 's petrochemical industry, and also the support technology for the first environmental protection inspection of glyphosate industry by the Ministry of environmental protection.
From 2010 to 2014, Xin'an group built a 135000 T / A and 225000 T / a continuous catalytic oxidation device for high concentration organic phosphorus wastewater, five 10000 t / a directional conversion phosphorus recovery devices, one 15000 T / a sodium pyrophosphate production device and 40000 t / a sodium phosphate production device