The suspended sulfur content in the sulfur recovery clear liquid is high – what are the effective solutions?

A high level of suspended sulfur in the sulfur recovery effluent is caused by poor control of the temperature and load in the sulfur melting tank.

1. As mentioned on the second floor, it is necessary to control the amount of material fed near the furnace and to regulate the temperature of the liquid exiting from the outlet; generally, the temperature of the liquid exiting from the continuous sulfur melting unit should be maintained between 90 and 95； 2. Check the regeneration status (and gas composition); if the foam quality is poor, it will also affect the suspended sulfur content in the clear liquid to a certain extent. 3. If conditions permit, the clear liquid can be filtered.

The previous filter can solve all problems related to sulfur recovery.

Using a filter is a good solution; there’s no need for a sulfur dissolution tank at all. Check out the Nitrogen Fertilizer and Methanol Technology website – there’s a product from a company called Nan Ying that works quite well

Our company uses plate and frame filter presses, which yield good results

The DS-type filter specialized for sulfur foam is used in the absorption, regeneration, and sulfur recovery processes – three essential steps in the wet oxidation method for desulfurization. In actual production, the most problems arise during sulfur recovery. In recent years, as companies have expanded their production scales, coal shortages have led to the increased use of high-sulfur coal, and the diversification of products has resulted in higher demands for precision regarding hydrogen sulfide levels in subsequent processing stages. In this context, the importance of sulfur recovery in desulfurization becomes increasingly evident. In the existing traditional sulfur recovery processes, continuous sulfur melting and batch sulfur melting are commonly used, with batch sulfur melting gradually being replaced by continuous sulfur melting. This represents a revolution in sulfur recovery during the desulfurization process, as it not only saves a great deal of labor, resources, and financial costs but also **reduces environmental pollution; it remains widely used in this industry to this day. However, over time, as the production scale of enterprises increases, the amount of hydrogen sulfide that can be processed per unit of time rises significantly, resulting in an increasing volume of residue after sulfur melting. This not only makes it more difficult to handle this residue during cooling, temperature reduction, and sedimentation processes, but it also increases the chances of HS- in the solution being converted into S2O32- during these processes. The excessive formation of these salt-rich substances **reduces the quality of the desulfurization solution; this not only affects the efficiency of desulfurization but can also cause equipment, pipes, and fillers to become clogged due to the crystallization of by-products in the solution. It seems that traditional sulfur recovery processes can no longer meet the needs of modern industrial production. Faced with this issue, what measures should we take to change this passive situation? We know that about 80% of the sulfur foam coming out of the regeneration tank (regeneration tower) consists of desulfurization liquid, with only around 20% being elemental sulfur. Moreover, due to differences in the catalysts used and variations in the quality of regeneration, the content of elemental sulfur in this sulfur foam varies greatly; in some cases, it is less than 10%. All of this sulfur foam is sent to the sulfur melting vessel for heating and melting, which not only **increases steam consumption but also makes it more difficult to handle the residual liquid. But if the sulfur foam is subjected to pressure filtration to turn it into a sulfur cake, and then the sulfur is melted (or disposed of), all those problems can be easily solved. In fact, since the advent of wet desulfurization, industry professionals have been focusing on research and development in this area. However, due to the numerous problems associated with traditional filtration techniques – such as the need for dedicated personnel to monitor the process, frequent replacement of filter media, high labor intensity for workers, poor working conditions, a large amount of residual liquid remaining in the filter cake after filtration, and high turbidity of the desulfurized liquid – this process has not been fully developed or utilized. In response to these issues, our company has developed the DS-type filter specifically designed for sulfur foam treatment, which fundamentally addresses the shortcomings of various filters used in the past. It combines the advantages of all existing and previous types of filters. Through pilot tests, scale-up trials, and industrial production experiments, highly satisfactory results have been achieved; its novelty and practicality are at the leading level in China. 2.1 Equipment schematic diagram: 2.2 Equipment overview: The DS-type vacuum filter dedicated for sulfur foam is a new type of solid-liquid separation device that combines nanometer inorganic membrane technology, ultrasound technology, and automated control features. It is efficient, energy-saving, and environmentally friendly. By taking into account the components of the desulfurization solution as well as the specific physical and chemical properties of each component, this device uses ultra-fine pores to filter out elemental sulfur from the sulfur foam without affecting the composition of the solution. The resulting filter cake can be packaged for sale or fed into a sulfur melting tank for further processing ； Due to the use of nanofiltration, the desulfurized solution after filtration contains very low levels of sulfur (the removal efficiency of elemental sulfur can exceed 99.9%). The turbidity of the filtered solution is low, making it clear and transparent (with a total solid content of <50 PPm). Moreover, since it is a physical filtration process, the physicochemical properties of the solution remain unchanged after filtration. It can be directly reused in the desulfurization system, thereby greatly saving energy consumption and reducing environmental pollution as well as damage to the system. 2, 3. Working principle: The DS desulfurization vacuum filter utilizes nanoceramic technology; under the action of vacuum pressure, the filtering medium allows only the desulfurization solution to pass through the pores of the ultra-fine ceramic membrane, while mechanical impurities, elemental sulfur, and bubbles in the solution cannot pass through. This prevents any loss of vacuum, thereby significantly reducing the energy consumption of the vacuum filter as well as the solid content in the filtered solution. 2. Equipment structure of 2 and 4; 2.5 Images of ceramic membranes; 2.6 and Working process: The DS desulfurization vacuum filter mainly consists of a filtering plate, rotor, slurry hopper, vacuum system, cleaning system, and control system. During operation, the filter plate submerged in the hopper has a layer of material adsorbed on its surface due to vacuum force and capillary action; the filtrate passes through the filter plate into the liquid discharge tank, while the filter cake in the drying zone continues to lose water under the effect of vacuum force. After the filter cake is dried, it is discharged using a scraper; following this discharge, it enters the backwashing area where the filter plates are cleaned with circulating water, thus completing one working cycle. After 7 hours of operation, the filter is cleaned using ultrasound and alkaline water to maintain its efficient performance. The resulting filter cake is bagged for processing or taken to a desulfurization tank for desulfurization. 2. Features of equipment 2,7: 2.7.1 A clean working environment with no pollution. 2, 7, 2 have high vacuum levels, resulting in a filter cake with lower moisture content compared to traditional filters. The filtration efficiency can reach over 70%. 2, 7, and 3 have a compact structure, occupy little space, and are easy to install and maintain. 2, 7, and 4 have low energy consumption, saving over 90% more energy compared to other filtration devices. 2, 7, 5: The filtrate is clear and transparent; the solid content is 15%, ranging from 0.8 to 1.2, with a concentration of 30–35%

This is obviously an advertisement, haha. But sulfur foam filtration seems to be the trend of the future – due to increasing environmental pressures, many manufacturers are forced to recycle all their liquid waste, including our company. . . However, the clear liquid has a high temperature as well as a high content of solids and by-products. The method currently used by our company is to extend the precipitation and cooling times, with the two underground tanks being used alternately

Use an upper internal fractionation type sulfur melting tank; in the sulfur melting tank at Taiyuan Gasification Plant No. 2, the suspended sulfur content in the liquid is 0.06–0.6 g/L

Currently, the filtration method is widely used, as it helps to save on steam costs, reduces the amount of by-products, and allows for efficient recovery of the solution

Operation of sulfur melting tank: Lower the temperature at the clear liquid outlet. Operation of filter press: Replace the filter cloth