本文選題：20#碳鋼 + 氣液平衡��； 參考：《浙江理工大學》2017年碩士論文

【摘要】：20#碳鋼是煉油行業(yè)中常用的設備及管道材料。由于原油劣質(zhì)化的影響(氋硫、高氯、含氮),煉油過程中形成的腐蝕性介質(zhì)(主要包括NH4HS和NH_4Cl)在一定流速下對設備管道造成嚴重的沖刷腐蝕,威脅裝置的本質(zhì)安全并造成重大的經(jīng)濟損失。沖刷腐蝕作為流動腐蝕的主要失效形式之一,具有明顯的風險性和局部性難以防控,特別是酸性水系統(tǒng)管道沖刷腐蝕十分嚴重。沖刷腐蝕影響因素涉及化工工藝流程、設備結構、腐蝕性介質(zhì)濃度、流速、溫度、壓力、運行工況,目前尚缺少系統(tǒng)的預測方法和研究體系,沖刷腐蝕失效事故仍頻發(fā)。本文依托某企業(yè)酸性水系統(tǒng)沖刷腐蝕失效,針對典型材料20#碳鋼開展氣液平衡條件下沖刷腐蝕規(guī)律研究。根據(jù)現(xiàn)場實際運行工況,基于化工工藝過程采用Aspen工藝計算軟件構建氣液平衡、離子平衡和化學平衡模型,獲得不同腐蝕性介質(zhì)在氣相及液相中的分布規(guī)律及溶液pH值變化趨勢;結合Computational Fluid Dynamics(CFD)軟件模擬計算多相流動特性分析沖刷腐蝕失效案例。結果表明:隨著溫度降低,腐蝕性氣體在水中摩爾分率增大,沖刷腐蝕風險增大且水相分率高的位置,沖刷腐蝕失效嚴重;通過合理注水量可以有效增大pH值,減小沖刷腐蝕風險。運用旋轉式?jīng)_刷腐蝕實驗裝置開展20#碳鋼在腐蝕性介質(zhì)NH_4Cl溶液中的腐蝕速率研究,包括:不同濃度、溫度、流速(包含靜止環(huán)境)等條件下沖刷腐蝕速率規(guī)律。同時采用掃描電子顯微鏡(SEM)技術觀察腐蝕試件表面形貌,研究沖刷腐蝕過程和腐蝕機理,進一步明確20#碳鋼在石化體系中出現(xiàn)腐蝕泄漏和穿孔失效的關鍵影響因素,為合理降低石化行業(yè)腐蝕失效提供理論依據(jù)。本文創(chuàng)新之處在于:針對酸性水管道現(xiàn)場實際運行工況,開展化工工藝過程關聯(lián)分析并采用數(shù)值模擬與沖刷腐蝕實驗相結合的研究方法構建酸性水管道腐蝕性溶液氣液平衡環(huán)境,探究沖刷腐蝕表征測試方法和臨界特性規(guī)律。研究成果可為石化行業(yè)設計優(yōu)化、設備選材和失效分析提供理論支撐。
[Abstract]:Carbon steel 20 # is a common equipment and pipeline material in oil refining industry. Due to the influence of poor quality of crude oil (sulfur, high chlorine, nitrogen-containing nitrogen, corrosive medium (mainly including NH _ 4HS and NH _ 4Cl) formed in refining process), serious erosion corrosion is caused to the equipment and pipeline at a certain flow rate. Threaten the essential safety of the device and cause significant economic losses. As one of the main failure forms of flow corrosion, scour corrosion is difficult to prevent and control with obvious risk and locality, especially the erosion corrosion of acid water system pipeline is very serious. The influencing factors of scour corrosion include chemical process, equipment structure, corrosive medium concentration, flow rate, temperature, pressure and operating condition. At present, there is still a lack of systematic prediction method and research system, and scour corrosion failure accidents still occur frequently. In this paper, based on the erosion failure of acid water system in a certain enterprise, the erosion corrosion law of typical carbon steel 20# under the condition of gas-liquid equilibrium is studied. According to the actual operating conditions of the field, the models of gas-liquid equilibrium, ion equilibrium and chemical equilibrium are constructed by using Aspen process calculation software based on the chemical process. The distribution of different corrosive media in gas phase and liquid phase and the changing trend of pH value of solution were obtained, and the failure cases of scour corrosion were analyzed and calculated by computer rational fluid dynamic CFDs software. The results show that with the decrease of temperature, the molar fraction of corrosive gas in water increases, the corrosion risk increases and the water phase fraction is high, the erosion corrosion failure is serious, and the pH value can be effectively increased by reasonable water injection. Reduce the risk of erosion corrosion. The corrosion rate of 20 # carbon steel in NH _ 4Cl solution was studied by means of rotating scour corrosion test equipment, including: the law of erosion corrosion rate under different concentration, temperature and flow rate (including static environment). At the same time, scanning electron microscopy (SEM) technique was used to observe the surface morphology of corrosion specimens, to study the erosion process and corrosion mechanism, and to further clarify the key factors affecting the corrosion leakage and perforation failure of 20 # carbon steel in petrochemical system. It provides a theoretical basis for reasonably reducing corrosion failure in petrochemical industry. The innovation of this paper lies in: according to the actual operation condition of acid water pipeline, The correlation analysis of chemical process and the combination of numerical simulation and erosion corrosion experiment were carried out to construct the gas-liquid equilibrium environment of corrosive solution of acid water pipeline and to explore the test method and critical characteristic law of erosion corrosion characterization. The research results can provide theoretical support for petrochemical industry design optimization, equipment selection and failure analysis.
【學位授予單位】：浙江理工大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TG178

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本文編號：1985938