Insoluble sulfur (Insoluble Sulfur) scientific name is the homopolymer of sulfur, also known as polymeric sulfur, referred to as IS, with an atomic weight of 32.07. Polymer modified variety, insoluble in carbon disulfide and rubber. Insoluble sulfur is an important vulcanizing agent and vulcanization accelerator in modern rubber production, which is of great significance for improving the performance and quality of rubber. With the development of the automobile industry, the demand for tire rubber is increasing day by day, thus promoting the development of the insoluble sulfur market.
However, the price of industrial sulfur products is low. If it can be further processed to increase its added value and develop insoluble sulfur products with broad prospects in the domestic market, its market price is 10 to 15 times that of ordinary sulfur. It can not only adjust the product structure of the enterprise, Extending the industrial chain and improving economic benefits, and at the same time solving the problem of environmental pollution through recycling and processing sulfur, is of great significance for the sustainable development of enterprises and the construction of environmentally friendly and resource-saving enterprises.
Development space of insoluble sulfur
Insoluble sulfur is a common additive in the rubber industry, mainly used as a vulcanizing agent in rubber production. Adding insoluble sulfur can eliminate the surface blooming of rubber products or intermediate products, and at the same time improve the adhesion, which is very beneficial for optimizing the operating environment. In addition, adding insoluble sulfur helps to increase the vulcanization speed of rubber and make the vulcanization reaction more uniform.
Based on the superior characteristics of insoluble sulfur in rubber production, it has become an important admixture in the production of tire carcass rubber, buffer rubber, white sidewall rubber and skeleton materials, and is widely used in various field. The insoluble rubber also helps improve the adhesion of the rubber to the copper-coated steel wire. In addition, the application of insoluble rubber is also very extensive and important in the production of rubber materials for rubber products such as cables, rubber rollers, oil seals, and rubber shoes.
It can effectively delay the vulcanization speed of rubber, maintain the viscosity of rubber, and prolong the service life of rubber. Due to the excellent characteristics of insoluble sulfur, although its price is more than ten times higher than ordinary orthorhombic sulfur, it is still the first choice of vulcanizing agent in the production of steel radial tires and other rubber composite products. Relevant data show that the proportion of insoluble sulfur consumption in the total sulfur consumption of foreign tire industry has reached as high as 40%, and it is still growing at a very high rate every year.
Insoluble sulfur traditional processing technology
Production method: At present, the common industrial production methods of insoluble sulfur include contact method, gasification method and melting method.
(1) Contact method
The contact method is the method with the longest history in the industrial production of insoluble sulfur. It uses hydrogen sulfide and sulfur dioxide as raw materials to produce insoluble sulfur.
The two raw materials are respectively passed into a reactor under an acidic environment for contact reaction, and the reaction products include soluble sulfur and insoluble sulfur. The product is successively washed, dried, pulverized, extracted, etc., and the insoluble sulfur and soluble sulfur are separated to finally obtain insoluble sulfur. At that time, the hydrogen sulfide and sulfur dioxide used in the contact method mainly came from by-products of the oil and gas industry.
The price of raw materials is low, and it has strong market competitiveness in terms of economy. Both sulfur dioxide and hydrogen sulfide are toxic. In order to ensure the health of surrounding personnel, the production process must be carried out in strictly sealed equipment.
As far as the technical conditions at that time were concerned, in order to ensure economic competitiveness, it was bound to be unable to meet the requirements for environmental protection and personal protection. With the deepening of the public's emphasis on environmental protection and the low utilization rate of raw materials in the contact method, the contact method is gradually replaced by the gasification method and the melting method.
(2) Gasification method
The gasification method is to use high temperature to melt solid sulfur and gasify it to produce insoluble sulfur, so it is also called high temperature method.
The molten sulfur is raised to between 500°C and 700°C by means of intermittent heating to form superheated steam. Then use the huge pressure of the high-temperature gas itself to jet into the low-temperature coolant for rapid cooling. The cooled product is a mixture of insoluble and soluble sulfur, with the former accounting for more than half of the total.
After the mixture is completely cooled into a solid, it is extracted with carbon disulfide, and then separated, washed, and dried to obtain an insoluble sulfur product with a high content. In the long-term practice, the production company has adjusted and optimized the process many times. The most important point is that hydrogen sulfide is introduced during the production process, thereby reducing the viscosity of the reactants and improving the stability of the insoluble sulfur.
Secondly, in the original gasification process, the processes of quenching, deacidification of rubber mixer to make sulfur flakes, drying and crushing were deleted, and the number of production links gradually decreased. In the end, the original complicated process was simplified into a one-step production method, which not only made the production simpler, but also greatly reduced the production cost, and the content of insoluble sulfur in the product was also increased. After years of development, the technology of gasification insoluble sulfur has been developed relatively mature, and the product yield is relatively high.
Its disadvantages are high production energy consumption, fast corrosion of system equipment, and high production safety risks. The large scale of project investment has also become an important factor limiting the promotion of gasification.
(3) Melting method
Compared with the gasification method, the melting method requires lower temperature conditions, so it is also called a low temperature method.
First, the sulfur is melted into a liquid state within the temperature range of 130°C to 150°C, then a stabilizer is added, and then the temperature is raised to 180°C to 210°C, with constant stirring to increase the conversion rate of insoluble sulfur. After that, water is used as the cooling medium for rapid cooling. After the water is taken out, the product solidifies into a block in the air. Crush it, add solvents, additives, grind, filter, and finally get insoluble sulfur powder.
Compared with the previous contact method and high-temperature method, the low-temperature melting method has a lower production temperature, the system reacts under normal pressure, less industrial waste, and has a high level of safety and economic benefits. The technical points of this method are the selection of stabilizer and how to realize the quenching effect of liquid sulfur during low-temperature polymerization. At present, the domestic low-temperature method of insoluble sulfur is still in the research stage, and there is still a long way to go before industrialized mass production.
The fully enclosed three-in-one filter vacuum dryer developed and designed by Wuxi ZhangHua Machinery aims at the advantages and disadvantages of the existing insoluble sulfur production process, solves the shortcomings of the traditional gasification method and melting method in the production of insoluble sulfur, and concentrates the operations of multiple process units on the It is automatically completed in one device to obtain high-quality, high-stability, and large-scale production of insoluble sulfur.
The core equipment of insoluble sulfur continuous production process fully enclosed filter washing and drying machine
The operation process of the fully enclosed filter washing and drying machine is simple, less transfer in the middle of the airtight, convenient material replacement, high production efficiency, and good product quality. The whole process from the feeding of the crystallization tank to the automatic discharge of the raw material from the bottom of the cone is completed in one set of equipment, which greatly reduces the total number of equipment in the raw material crystallization process, which not only reduces the investment cost, but also reduces the area of the clean workshop.
In addition, the cleaning and filtering of crystals can be repeated several times according to the production process, and the drying process can be carried out after reaching the standard. The new process uses a multi-functional filter device to reduce the material exposure time, and multiple operating procedures are carried out in a closed container to effectively prevent pollution, and it is easy to carry out in-situ cleaning and in-situ sterilization.
The production technology and product quality of my country's insoluble sulfur have basically reached the quality level of similar products of Crystex.
At the same time, there are more than 30 research institutes, universities and chemical plants in more than 20 provinces and cities across the country to develop and research insoluble sulfur, and there are dozens of different production devices. But so far, they are still fighting alone, and they are fighting independently, and they have not yet achieved economies of scale. The production scale is also relatively small, some unit equipment is relatively backward, the cost is relatively high, and it is not yet competitive in the international market.
However, with the increasing prosperity of my country's industrial economy, especially the rapid development of the automobile industry, the demand for high-quality rubber will only increase. As a high-quality vulcanizing agent and vulcanization accelerator in rubber production, insoluble sulfur has a very large market development space. Standing at this new starting point, ZhangHua people will have the courage to take responsibility and help manufacturers actively promote technological upgrading and transformation through research and development and production of more excellent equipment, speed up product research and development, improve product quality, and enhance corporate market competitiveness. While realizing the economic and social benefits of the enterprise, it will promote the healthy and rapid development of my country's rubber industry.