Abstract:

Significance High-temperature dust is the characteristic of air pollutants discharged by industry. Bag-type dust removal systems have been widely used in high-temperature dust treatment of waste incineration plant, steel plant, cement plant and coal-fired power plant, due to effectiveness and low cost. Filter bags are the key material of bag dust removal system. Polyphenylene sulfide (PPS) fiber is one of the most widely used thermoplastic fibers in the field of high-temperature filter bags due to the good mechanical properties, outstanding thermal stability and excellent flame retardancy. With the upgrade of flue gas emission standards, the quantity demand and replacement of PPS filter bags both greatly increases. However, most of waste PPS filter bags are disposed by incineration or landfill. A large quantity of smoke, acid or alkaline gas and carcinogens can be produced during the incineration process. Meanwhile, the dust particles, acid and alkaline substances and carcinogens contained in the waste PPS filter bags can also cause pollution of soil and groundwater through the landfill. Therefore, these two traditional treatment methods not only waste resources but also cause serious damage on the environment. Moreover, the most important thing is that PPS fibers cannot be recycled. Therefore, it is of great social significance and economic value to recycle waste PPS fibers and filter bags.
Progress In order to promote the efficient and high-value recycling of waste PPS fibers and filter bags, a detailed overview on the current research advances was carried in this study, where the methods, processes, advantages and disadvantages of recycling PPS fibers were compared, analyzed and summarized. The technical difficulties affecting the recycling use of waste PPS filter bags were also analyzed from the aspects of deashing treatment, complex fiber composition and high recycling cost. Finally, a tripartite linkage mechanism of PPS filter bags manufacturer, user and recycling enterprise was proposed to manage and recycle waste PPS filter bags in different working conditions to provide reference for the high-value recycling. Currently, the commonly used recycling methods can be roughly divided into chemical recovery method and physical recovery method. The chemical recovery method refers that the PPS macromolecular chains are dissolved or decomposed using the corresponding organic solvent, and then the high polymer solid or polymer monomer are separated and reused. The technology of chemical dissolution method is relatively mature and the recovery rate is high, and it can be used for PPS filter bags with different components. Moreover, the chemical dissolution method has a high application value if the recovery rate of organic solvent can be improved and the separation and purification process can be simplified during the process of industrialization. Physical recovery method refers that waste PPS filter bags are generated into the initial state and reused by mechanical processing. It can be divided into mechanical pulverization, melt reprocessing, fiber disassembly and direct utilization. The mechanical pulverization method has been industrialized because of its simple process and low cost. The other three methods are still in the stage of experiment due to the limitation of multiple factors.
Conclusions and Prospect Recycling use of waste PPS filter bags is an effective and imperative way to protect the environment and preserve the resources, which will benefit both the society and the economy significantly. However, the industrial scale of waste PPS filter bags recycling is small in our country, and the industrial cluster has not yet formed. Mechanical pulverization is the only recycling method that has been industrialized, but the industrial scale is still small. The chemical solution method has been studied extensively and has entered the stage of small trial. It will become the main recycling method for waste PPS filter bags on the condition of solving the high price and recycling of chemical solvent. In short, the recycling process of waste PPS filter bags is still immature and it is fraught with technical difficulties and high coasts. This paper puts forward some suggestions in the following areas. 1) A professional recycling system for waste PPS filter bags and other waste filter bags should be established. 2) Advanced and mature recycling processes and methods need to be developed to solve the technical difficulties by increasing R&D investment. 3) It is urgent to have the standards, laws and regulations for the recycling of waste PPS filter bag shall be formulated.

Key words: waste polyphenylene sulfide fiber, chemical dissolution, mechanical pulverization, fiber disassembly, melt processing, recycling