Experimental design of fluidized bed heat treatment for industrial waste salt
[Objective]At present,China's industrial by-product salt production is large,and the composition is complex.Most of the research on industrial waste salt at home and abroad mainly focuses on single types of waste salt and laboratory-simulated waste salt.It is difficult to provide specific process conditions for the treatment of actual industrial waste salt from various sources.The fluidized heat treatment method of industrial waste salt has universal applicability,wherein the waste salt is uniformly mixed with the granular material treated by a fluidized bed,the mass transfer and heat transfer efficiency is high,and the gas-solid two-phase contact is sufficient.However,industrial waste salt is prone to ringing,agglomeration,and corrosion equipment at high temperatures.To solve the aforementioned problems of industrial waste salt heat treatment,it is critical to further explore and optimize the treatment methods of industrial waste salt.[Methods]In this paper,the fluidized bed process is used to carry out the experimental research.The physical properties of two kinds of industrial waste salts from the pesticide and coal chemical industries are analyzed.The fluidization cold model experiment is carried out to study the fluidization characteristics of two kinds of industrial waste salt by using the physical parameters of waste salt,and the heat treatment experiment is carried out.By comparing the experimental data of the fluidization heat treatment results of two kinds of industrial waste salt at different treatment temperatures and times,the process conditions of fluidization heat treatment of industrial waste salt are determined and optimized.The raw salt and the product salt were characterized using the following methods:X-ray fluorescence analysis of the raw salt of the two waste salts,X-ray diffraction analysis of the raw salt and the product salt under the best heat treatment conditions,infrared spectrum analysis,total organic carbon analysis,and comparison.[Results]The experimental results show that,first,the process conditions of fluidization heat treatment of the two industrial waste salts are as follows:the ratio of height to diameter is 3;the operating gas velocities of 1#and 2#industrial waste salts are 0.19 m·s-1 and 0.38 m·s-1,respectively;and the optimal treatment temperature and time were 450℃at 30 min and 550℃at 30 min,respectively.Second,the characterization results show that the crystal form of the product salt remains unchanged after fluidization,and the organic matter is reduced and effectively removed.Third,after dissolving,filtering,and recrystallization of the waste salt under the optimal fluidized bed heat treatment conditions,1#industrial waste salt obtained mixed crystalline salt containing inorganic substances,such as sodium sulfate and sodium chloride.The purity of NaCl in the crystalline salt obtained by 2#industrial waste salt reached 98.91%,which met the first-level standard of refined industrial dry salt and reached the index of waste salt resource utilization.[Conclusions]In this paper,the fluidized heat treatment process conditions of industrial waste salt with two specific physical parameters were determined by the cold model experiment and the fluidized heat treatment experiment.Under this process condition,the organic matter was effectively removed,and the product salt could be recycled.The findings suggest further exploration and optimization of industrial waste salt treatment methods.
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