Research On Erosion Corrosion Of Heterogeneous Liquid-Solid Two-Phase Flow In Coal Gasification Unit

As a result of coupling effects of scouring and corrosion,erosion restricts the long-term safe operation of coal gasification units.It causes thinning,perforation,cracking of equipment&pipeline,resulting in leakage and even casualties.The erosion undoubtedly has become a difficult problem that the engineering field has to face.For a coal gasification unit,the coupling effects of particle scouring and alkaline acid water corrosion is generally the dominant factor.On the other hand,the non-uniform liquid-solid flow also influences the erosion features.Therefore,in view of the erosion problem in coal gasification unit,this paper design an experimental setup to study the coupling effect of erosion and corrosion,measure the erosion/corrosion rates,correct the erosion model and establish a simulation method to quantify the non-uniform liquid-solid two-phase flow erosion and corrosion.In particular,study the erosion features of dilute phase and dense phase heterogeneous liquid-solid two-phase flow in the black water of industrial coal gasification unit and the feeding pipe of slag breaker,propose a more accurate prediction to judge the easy-erosion locations,and then guide the safe operation and the maintenance of equipments.First,this paper design a liquid-solid two-phase flow erosion/corrosion weight loss experimental setup,the weight loss method was used to measure the erosion/erosion rate of the sample in water,NH₄HS aqueous solution and sands+water systems,respectively.The measured erosion rates are used to obtain a multivariate correlation.The experimental results show that the particle erosion and the alkaline acid water corrosion are the main factors.Under the joint action of these two mechanisms,the erosion rate increases significantly.Second,for the black water of the industrial coal gasification unit and the feeding pipeline of the slag breaker,the effects of the different erosion models,the drag models,the turbulence models,the rebound coefficients,the impact angle functions,the particle concentrations and other factors on the erosion rate were simulated and compared.The model suitable for coal gasification black water and slag water pipelines is determined.It is also found that the DDPM+EMMS method has better prediction accuracy for the erosion corrosion simulation of heterogeneous dense phase liquid-solid two-phase flow.By coupling the multivariate erosion rate correlations fitted by the experimental data into the CFD erosion simulation,the coupling action feature of the erosion and corrosion for five industrial pipelines is investigated.It shows that the erosion rate calculated by coupling the multivariable erosion rate correlation is agree well with the actual thinning rate of the pipeline.Finally,based on the non-uniform dense phase liquid-solid two-phase flow simulation method,the particle concentration erosion rate in a typical 90°elbow in commercial unit under different flow rates,particle concentrations,and spatial positions（the horizontal,the ascending and the descending）is studied.The results show that,under the action of the gravity,the erosion rate and erosion locations in the horizontal,the ascending and the descending elbows are slightly different;but the features with the variations with the flow velocity and the particle concentration are almost the same.When the flow velocity increases,the erosion rates in different locations of the inner wall of the elbow all increase to different degrees.With an increasing of particle concentration,the erosion rate of the liquid-solid two-phase flow in the elbow increase consequentially;and the erosion rate occurs a step as it increases to a certain value.