【摘要】：安全問題一直是化工行業(yè)的首要問題,實現(xiàn)安全生產(chǎn)與經(jīng)濟效益“共贏”是企業(yè)的目標。乙烯壓縮制冷系統(tǒng)由于在負壓下操作會引進空氣產(chǎn)生不凝性氣體(主要是N2和02),系統(tǒng)中乙烯與02共存易形成爆炸性混合物,為了保證生產(chǎn)安全性,系統(tǒng)必須定期排放不凝氣,富含乙烯的不凝氣直接排放造成嚴重浪費。此外,乙烯壓縮制冷系統(tǒng)開車過程需要用高純乙烯置換氮氣,目前工廠將乙烯置換氣直接排放至火炬燃燒,沒有采取回收措施,也造成乙烯資源的浪費。對排放乙烯進行合理回收,能夠提高企業(yè)的經(jīng)濟效益。負壓操作下的壓縮制冷系統(tǒng)正常工況和開車工況年總排放420噸乙烯。現(xiàn)有工藝采用冷凝法和膜法回收正常工況排放的乙烯,冷凝工藝由于氣液分離罐存在嚴重的霧沫夾帶現(xiàn)象,造成氣液分離不徹底使尾氣帶液,直接冷凝達到臨界液化溫度會導致O2被液化乙烯吸收排不出去,而在系統(tǒng)中積累,存在氧含量超標的安全隱患。通過減少尾氣的帶液量,改變冷凝起點,可提高冷凝溫度的操作彈性,降低系統(tǒng)中氧含量,提高安全系數(shù)。采用的膜分離回收工藝,由于膜滲透側(cè)為負壓,會增加滲入空氣的概率,同樣導致02在系統(tǒng)中積累。通過使用限流孔板產(chǎn)生壓降,將膜滲透側(cè)壓力提高到正壓,可有效避免空氣滲入。針對現(xiàn)有回收工藝存在的氧積累的安全隱患問題,提出使用精密過濾器減少尾氣帶液量,膜滲透側(cè)直接設置為正壓的方法,并設計了解決安全問題的改進方案。通過UniSimDesign軟件對操作參數(shù)進行模擬優(yōu)化,考察了冷凝溫度對系統(tǒng)中氧含量及經(jīng)濟效益的影響。結(jié)果表明：改進方案冷凝溫度范圍均從-44～-46℃提高到-50-55℃,提高了冷凝溫度的操作彈性,降低了系統(tǒng)中的氧含量,提高了安全性,同時還可保持較高的經(jīng)濟效益。其中膜回收法可使系統(tǒng)中氧含量降低到150 ppm,經(jīng)濟效益達到375萬元·a-1。針對開車工況尾氣間歇排放,瞬間排放量大(8500 Nm3.h-1),乙烯含量變化幅度大(C2H4 wt%：O～100%),且尾氣帶壓的特性,提出了采用透平膨脹制冷開車尾氣回收方案,并采用UniSim Design軟件進行參數(shù)優(yōu)化。結(jié)果表明,冷凝溫度為-120～-130℃時,經(jīng)濟效益最大為14.5萬元·a-1。設計的冷箱的換熱面積為450 m2,透平膨脹機輸出功為90 kW。
[Abstract]:Safety problem has always been the primary problem in chemical industry. It is the goal of enterprises to realize "win-win" between production safety and economic benefit. Ethylene compression refrigeration system can produce non-condensable gases (mainly N2 and 02) due to the introduction of air under negative pressure. The co-existence of ethylene and 02 is easy to form explosive mixture. In order to ensure the safety of production, The system must discharge non-condensable gas regularly, and direct emission of ethylene-rich non-condensing gas results in serious waste. In addition, it is necessary to replace nitrogen with high purity ethylene during the start-up process of ethylene compression refrigeration system. At present, ethylene replacement gas is directly discharged into torch combustion in the factory, and no recovery measures have been taken, which also results in the waste of ethylene resources. Reasonable recovery of ethylene emissions can improve the economic benefits of enterprises. Compression refrigeration system under negative pressure operation under normal and start-up operation of the total annual emissions of 420 tons of ethylene. The existing process uses condensation method and membrane method to recover ethylene discharged under normal working conditions. Because of the serious entrainment phenomenon in the gas-liquid separation tank, the gas-liquid separation does not completely bring the tail gas to the liquid. Direct condensation to the critical liquefaction temperature will lead to O _ 2 being absorbed and discharged by ethylene liquefaction, but accumulation in the system, there is a hidden danger that the content of oxygen exceeds the standard. By reducing the amount of liquid in tail gas and changing the starting point of condensation, the operating elasticity of condensing temperature can be increased, the oxygen content in the system can be reduced and the safety factor can be improved. The membrane separation and recovery process, because the membrane penetration side is negative pressure, will increase the probability of infiltration into the air, also lead to the accumulation of 02 in the system. Air infiltration can be effectively avoided by increasing the pressure of membrane infiltration side to positive pressure by using flow-limiting orifice plate to produce pressure drop. In view of the hidden danger of oxygen accumulation existing in the existing recovery process, the method of using precision filter to reduce the amount of liquid in tail gas and to set the membrane infiltration side directly to positive pressure is put forward, and the improvement scheme to solve the safety problem is designed. The influence of condensation temperature on the oxygen content and economic benefit of the system was investigated by simulating and optimizing the operating parameters by UniSimDesign software. The results show that the range of condensation temperature is increased from-44 鈩，

本文編號：2441989