減頂水冷器腐蝕失效分析及材質(zhì)腐蝕規(guī)律研究
發(fā)布時間：2018-11-15 23:24
【摘要】：常減壓裝置的腐蝕問題一直是困擾煉化企業(yè)的一個重點難題,腐蝕風(fēng)險的存在直接影響煉油裝置的長周期運行,安全加工生產(chǎn)、產(chǎn)品質(zhì)量以及企業(yè)經(jīng)濟效益。探究腐蝕機理及腐蝕發(fā)生原因,有針對性的解決常減壓裝置的腐蝕問題,對于企業(yè)安全高效生產(chǎn)具有非常重要的實際意義。因此,本文做了以下幾方面研究：(1)本文通過金相顯微鏡和掃描電鏡對換熱器支撐梁和管束裂紋及孔蝕形貌進行表征,并通過電子能譜和洛氏硬度儀對支撐梁失效件、腐蝕產(chǎn)物進行了電子能譜掃描和材質(zhì)硬度檢測,分析了減頂水冷換熱器腐蝕開裂原因,確定換熱器換熱管的腐蝕失效主要以點蝕為主,而支撐梁主要腐蝕失效形式為點蝕加開裂失效。對換熱器材質(zhì)進行分析,結(jié)果表明：換熱管材質(zhì)成分基本符合304材質(zhì)特征,在HC1-H2S-H2O酸性環(huán)境下僅發(fā)生了點蝕,但是支撐梁成分檢測結(jié)果顯示Ni、Cr元素含量均偏低,趨于標(biāo)準(zhǔn)含量線以下;支撐梁材質(zhì)硬度檢測結(jié)果為32 HRC,超過設(shè)備設(shè)計要求22 HRC；金相特征觀察顯示,支撐梁裂紋呈臺階狀分布,并且沿晶開裂；腐蝕產(chǎn)物成分分析,檢測出含有Cl元素和S元素。綜合以上分析得出結(jié)論：煉油廠所煉原油復(fù)雜多變,電脫鹽設(shè)備脫鹽效果不穩(wěn)定,導(dǎo)致減壓塔頂HCl、H2S含量升高,遇到冷凝水形成HCl-H2S-H2O酸性環(huán)境,導(dǎo)致設(shè)備支撐梁出現(xiàn)“臺階狀”沿晶開裂,即典型的氫脆失效特征。支撐梁由于固溶不好或者未進行固溶處理導(dǎo)致硬度較高,高硬度的材質(zhì)在HCl-H2S-H2O環(huán)境下容易誘發(fā)氫致開裂。(2)對2205雙相不銹鋼腐蝕規(guī)律做了詳細研究,主要考慮氯離子和硫離子兩種因素對2205雙相鋼腐蝕規(guī)律的影響。通過對2205雙相鋼孔蝕溫度曲線的一系列測試,得出氯離子濃度越高,2205雙相鋼的孔蝕溫度越低,同時考察pH值影響因素,pH值越低,2205雙相鋼的孔蝕溫度也相應(yīng)越低。通過對2205雙相鋼交流阻抗曲線測試,結(jié)果表明,硫離子的存在影響了鈍化膜的自我修復(fù)生長過程,使得2205雙相不銹鋼的鈍化膜更容易受到氯離子侵蝕破壞,而且硫離子濃度越高,這種破壞作用越明顯。同時也考察了pH值和溫度的影響因素,在酸性條件下,硫離子的作用更加強烈,高溫環(huán)境下,硫離子也顯出了很高的活性,更加促進氯離子的腐蝕作用。這一系列規(guī)律對于常減壓塔頂相應(yīng)溫度下,如何控制氯離子濃度和硫離子濃度以及pH值范圍等參數(shù),降低設(shè)備腐蝕風(fēng)險具有實際的指導(dǎo)意義。以上相關(guān)腐蝕規(guī)律的研究對提高常減壓系統(tǒng)裝置的可靠性、延長設(shè)備安全運行周期、確保企業(yè)的生產(chǎn)安全及經(jīng)濟效益具有一定的指導(dǎo)意義和應(yīng)用價值。
[Abstract]:The corrosion problem of atmospheric and vacuum plant has been a key problem for refinery and chemical enterprises. The existence of corrosion risk directly affects the long period operation, safe processing and production, product quality and economic benefit of the refinery plant. It is of great practical significance to probe into the corrosion mechanism and the causes of corrosion and to solve the corrosion problem of atmospheric and vacuum equipment for the safe and efficient production of enterprises. Therefore, the following aspects have been studied in this paper: (1) the crack and pitting morphology of the support beam and tube bundle of heat exchanger are characterized by metallographic microscope and scanning electron microscope, and the failure parts of the support beam are analyzed by EDS and Rockwell hardness instrument. The corrosion products were scanned by EDS and the hardness of the material was tested. The reason of corrosion cracking in the top water cooling heat exchanger was analyzed. It was determined that the corrosion failure of heat exchanger tube was mainly pitting corrosion. The main corrosion failure form of support beam is pitting plus cracking failure. The material of heat exchanger is analyzed. The results show that the material composition of heat exchanger pipe basically accords with the material characteristic of 304, and only pitting corrosion occurs in the acidic environment of HC1-H2S-H2O, but the testing results of the component of support beam show that the content of Ni,Cr element is on the low side. Tend below the standard content line; Hardness test of support beam material is 32 HRC, exceeding design requirement of equipment 22 HRC; Metallographic observation shows that the crack of the supporting beam is a step shape and intergranular crack, and the corrosion product is found to contain Cl and S elements by analyzing the composition of the corrosion product. By synthesizing the above analysis, it is concluded that the crude oil refined in the refinery is complex and changeable, and the desalination effect of the electric desalting equipment is unstable, which leads to the increase of the HCl,H2S content at the top of the decompression tower and the formation of acidic HCl-H2S-H2O environment by condensing water. Leading to the "step" intergranular cracking of the support beam, that is, typical hydrogen embrittlement failure characteristics. The hardness of the support beam is high due to poor solution or no solution treatment, and the high hardness material can easily induce hydrogen induced cracking in HCl-H2S-H2O environment. (2) the corrosion law of 2205 duplex stainless steel is studied in detail. The influence of chloride ion and sulfur ion on corrosion law of 2205 duplex steel was considered. Through a series of tests on the pitting corrosion temperature curve of 2205 dual phase steel, it is concluded that the higher the chloride ion concentration, the lower the pitting corrosion temperature of 2205 dual phase steel. At the same time, the influence factors of pH value are investigated. The lower the pH value, the lower the pitting corrosion temperature of 2205 dual phase steel. By measuring the AC impedance curves of 2205 duplex steel, the results show that the existence of sulfur ions affects the self-repair growth process of the passivation film and makes the passivation film of 2205 duplex stainless steel more vulnerable to chloride erosion. Moreover, the higher the concentration of sulfur ion, the more obvious the destructive effect is. At the same time, the influence factors of pH value and temperature were also investigated. The effect of sulfur ion was more intense under acidic condition, and the sulfur ion also showed high activity in high temperature environment, and promoted the corrosion of chloride ion more. This series of rules has practical guiding significance for how to control the concentration of chloride ion and sulfur ion and the range of pH value at the corresponding temperature of the top of atmospheric and vacuum tower, and to reduce the corrosion risk of equipment. The above research on corrosion law has certain guiding significance and application value for improving the reliability of atmospheric and vacuum system equipment, prolonging the safe operation period of equipment and ensuring the production safety and economic benefit of the enterprise.
【學(xué)位授予單位】：大連理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2016
【分類號】：TQ051.5
本文編號：2334708
[Abstract]:The corrosion problem of atmospheric and vacuum plant has been a key problem for refinery and chemical enterprises. The existence of corrosion risk directly affects the long period operation, safe processing and production, product quality and economic benefit of the refinery plant. It is of great practical significance to probe into the corrosion mechanism and the causes of corrosion and to solve the corrosion problem of atmospheric and vacuum equipment for the safe and efficient production of enterprises. Therefore, the following aspects have been studied in this paper: (1) the crack and pitting morphology of the support beam and tube bundle of heat exchanger are characterized by metallographic microscope and scanning electron microscope, and the failure parts of the support beam are analyzed by EDS and Rockwell hardness instrument. The corrosion products were scanned by EDS and the hardness of the material was tested. The reason of corrosion cracking in the top water cooling heat exchanger was analyzed. It was determined that the corrosion failure of heat exchanger tube was mainly pitting corrosion. The main corrosion failure form of support beam is pitting plus cracking failure. The material of heat exchanger is analyzed. The results show that the material composition of heat exchanger pipe basically accords with the material characteristic of 304, and only pitting corrosion occurs in the acidic environment of HC1-H2S-H2O, but the testing results of the component of support beam show that the content of Ni,Cr element is on the low side. Tend below the standard content line; Hardness test of support beam material is 32 HRC, exceeding design requirement of equipment 22 HRC; Metallographic observation shows that the crack of the supporting beam is a step shape and intergranular crack, and the corrosion product is found to contain Cl and S elements by analyzing the composition of the corrosion product. By synthesizing the above analysis, it is concluded that the crude oil refined in the refinery is complex and changeable, and the desalination effect of the electric desalting equipment is unstable, which leads to the increase of the HCl,H2S content at the top of the decompression tower and the formation of acidic HCl-H2S-H2O environment by condensing water. Leading to the "step" intergranular cracking of the support beam, that is, typical hydrogen embrittlement failure characteristics. The hardness of the support beam is high due to poor solution or no solution treatment, and the high hardness material can easily induce hydrogen induced cracking in HCl-H2S-H2O environment. (2) the corrosion law of 2205 duplex stainless steel is studied in detail. The influence of chloride ion and sulfur ion on corrosion law of 2205 duplex steel was considered. Through a series of tests on the pitting corrosion temperature curve of 2205 dual phase steel, it is concluded that the higher the chloride ion concentration, the lower the pitting corrosion temperature of 2205 dual phase steel. At the same time, the influence factors of pH value are investigated. The lower the pH value, the lower the pitting corrosion temperature of 2205 dual phase steel. By measuring the AC impedance curves of 2205 duplex steel, the results show that the existence of sulfur ions affects the self-repair growth process of the passivation film and makes the passivation film of 2205 duplex stainless steel more vulnerable to chloride erosion. Moreover, the higher the concentration of sulfur ion, the more obvious the destructive effect is. At the same time, the influence factors of pH value and temperature were also investigated. The effect of sulfur ion was more intense under acidic condition, and the sulfur ion also showed high activity in high temperature environment, and promoted the corrosion of chloride ion more. This series of rules has practical guiding significance for how to control the concentration of chloride ion and sulfur ion and the range of pH value at the corresponding temperature of the top of atmospheric and vacuum tower, and to reduce the corrosion risk of equipment. The above research on corrosion law has certain guiding significance and application value for improving the reliability of atmospheric and vacuum system equipment, prolonging the safe operation period of equipment and ensuring the production safety and economic benefit of the enterprise.
【學(xué)位授予單位】：大連理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2016
【分類號】：TQ051.5
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