| The composition of wastewater from coal chemical industry is complex,the treatment process is difficult,and the pipe is seriously corroded in the process of transportation and discharge.With the development of China's coal chemical industry,the pollution caused by wastewater discharge is more and more serious.Wastewater recycling has become a necessary means for coal chemical enterprises to reduce environmental pollution.The complex components of coal chemical wastewater in the flow process are easy to cause corrosion of pipelines and equipments.Due to the complex process,unstable flow form and few related researches,there are some problems to be solved in the aspects of corrosion mechanism and corrosion resistance.Based on the above problems,this paper studies the corrosion behavior of high salt wastewater in AISI 302 stainless steel sudden expansion pipeline and the corrosion behavior of AISI 302 in coal chemical wastewater by the method of numerical simulation and experiment.The systematic analysis and research have been carried out,and some research results with scientific signifcance and engineering application value have been obtained.In this paper,taking the sudden expansion pipeline with a sudden expansion ratio of aas an example,a test system of erosion and corrosion cycle is designed to carry out erosion and corrosion experiments on high salt wastewater from coal chemical industry.Through electrochemical test,weight-loss experiment and computational fluid dynamics software(CFD),the fluid flow behavior and erosion corrosion in different positions of sudden expansion pipeline were studied,and the corrosion behavior of austenitic stainless steel in high salt wastewater of coal chemical industry was studied by heat treatment.(1)Computational fluid dynamics(CFD)was used to simulate the flow state of high salt wastewater from coal chemical industry in AISI 302 stainless steel sudden expansion pipeline with a sudden expansion ratio of 2,and a circulation circuit was designed to study the erosion corrosion of high salt wastewater from coal chemical industry in different locations by means of electrochemical test and weight loss test.The results show that the corrosion rate of the sudden expansion pipeline is the highest at 2.5 a(a is the sudden expansion ratio),and the corrosion rate tends to be stable with the increase of the length of the sudden expansion pipeline.The results of CFD simulation show that the transverse velocity of the fluid is the smallest at 2.5 ?,and the transverse velocity of the fluid increases with the increase of the length of the pipeline.On the contrary,the wall shear stress decreases.(2)The corrosion behavior of AlSl 302 austenitic stainless steel in high salt wastewater of coal chemical industry after heat treatment was studied by electrochemical method.The results show that after heat treatment at 800 ? and 1000? for 0.5 h and 2 h respectively,the grains of A ISI 302 stainless steel become uniform and the grain boundary angle increases.After heat treatment,the corrosion resistance of AISI 302 stainless steel in high salt wastewater of coal chemical industry is obviously improved.The corrosion resistance of coal chemical high salt wastewater is in the order of 1000?,2h>1000?,0.5h>800?,2h>800 ?,0.5h>original sample.Combined with the experimental design of the erosion corrosion of the sudden expansion pipeline,the flow law and the erosion corrosion law of different positions of AISI 302 stainless steel sudden expansion pipeline were obtained,and the corrosion behavior of AISI 302 stainless steel in high salt wastewater after heat treatment was studied.It can provide basis for corrosion inhibition of sudden expansion equipment in coal chemical plant and for heat treatment parameters of stainless steel corrosion in high salt wastewater. |
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