Industrially, sulfur, hydrogen sulfide, or sulfur dioxide are the main raw materials, with sulfur being the most common. Industrially, sulfur mainly comes from two sources: extraction from sulfur mines and recovery from desulfurization units in industries such as natural gas and petroleum processing. The purity of the raw sulfur must meet requirements; otherwise, product quality will be severely affected.
According to different classification methods, insoluble sulfur has various production processes. These processes generally include raw material pretreatment, pre-melting, polymerization, quenching, solidification, extraction, and oil filling.
(1) According to the different raw materials, it can be divided into the gas contact method and the orthorhombic sulfur conversion method. The gas contact method uses hydrogen sulfide and sulfur dioxide as raw materials, reacting them in a reactor with added acidic medium to generate low-content insoluble sulfur. Subsequent washing, drying, and extraction operations yield a high-content product. This process is mainly concentrated in Eastern Europe, such as Russia. The orthorhombic sulfur conversion method uses ordinary orthorhombic sulfur as raw material, undergoing homopolymerization under certain conditions, and is currently the main industrial method.
(2) According to different polymerization processes, the orthorhombic sulfur conversion method can be further divided into the melting method and the gasification method. The melting method, also known as the low-temperature method, involves pre-melting the raw sulfur and heating it to above 200℃ for polymerization in a molten state. The resulting liquid sulfur is quenched to obtain a mixture with approximately 40% insoluble sulfur by mass. This mixture is then processed through extraction, displacement, filtration, and drying to obtain the finished product. The gasification method, also known as the high-temperature method, involves pre-melting ordinary sulfur and then heating it to 500-700℃ to obtain high-temperature, high-pressure sulfur vapor. This vapor is then rapidly passed through a cooling medium for quenching, resulting in the insoluble sulfur product.
Based on these two processes, some domestic literature categorizes the production processes of insoluble sulfur as the contact method, the melting method, and the gasification method. Industrially, the gasification method and the melting method are the main methods used to produce insoluble sulfur. The difference between these two methods lies in the form of the sulfur entering the quenching liquid: the melting method uses liquid sulfur, while the gasification method primarily uses gaseous sulfur.
(3) According to the difference in the quenching medium in the later stage, the quenching process can be divided into water-based process and non-water-based process. The water-based process mainly uses water, acidic aqueous solution and other media; the non-water-based process (solvent method) commonly uses organic solvents such as carbon disulfide, carbon tetrachloride, toluene, butane and chlorinated hydrocarbons as quenching agents, among which carbon disulfide is the most common. These quenching agents can dissolve ordinary sulfur and can also play an extraction role while quenching. This report mainly uses the quenching medium as the standard to divide the insoluble sulfur production process into three categories: high temperature water method, intermittent solvent method and continuous method. The sulfur is washed to minimize the residual soluble sulfur in the insoluble sulfur. The washing liquid enters the carbon disulfide receiving tank. The green and clean process of insoluble sulfur is a continuous gasification one-step method, which has the advantages of short process flow, low production cost, high polymerization conversion rate and low sulfur consumption.
