Valve Selection for Large Chemical Package Unit
2016-12-02
Large chemical package unit includes ethylene, synthesis ammonia,air separation etc.
1. Valves used for ethylene plant unit
Mostly used raw materials for making ethylene is atmospheric light diesel oil and decompression heavy diesel oil, and ethylene plant working conditions are extremely harsh, high temperature (900 ℃), high pressure (10.0MPa), ultra-low temperature (-196 ℃),mass flow. The valves related with ethylene package units are as follows:
(1) High pressure bellow seal valve
The construction type of this valve can be gate-valve or globe-valve type. Size range from DN15~300mm,pressure 0.6~1.0MPa,main parts material are WCB/A105,CF8/F304,CFM8/F316.
(2) High temperature flat gate valve
This kind of valve can be classified as self-seal and unfurled type. Size range from DN15~1200mm,pressure 0.05~1.6MPa.
(3) Cryogenic valves
The construction type of this valve can be gate-valve type, no-return type and globe valve type. Size range from DN50~700mm,pressure 1.6~6.4MPa,lowest operating temperature is -196℃.
2. Valves used for synthesis ammonia package unit
There are three main types of medium for synthetic ammonia plants: that are, synthetic gas–containing H2, N2, CO, CO2 and NH3 which is similar to artificial gas (H2 is a very dangerous gas with very low explosive limit and CO is toxic); urea–containing NH3, CO2, ammonium carbamate etc; liquid ammonia or ammonia. Ammonia device valve with the maximum operating temperature of about 500 ℃, the lowest temperature liquid ammonia medium at -33 ℃, the maximum working pressure of 32.0MPa. The valves related with synthesis ammonia package units are as follows:
(1) High temperature & pressure angle type globe valve
The valve nominal size scope is DN10 ~ 100mm, pressure ≤ 42.0MPa,the maximum working temperature 570 ℃.
(2)Throttle valve
The valve nominal size is DN10 ~ 100mm,nominal pressure ≤ 42.0MPa, the maximum working temperature 570 ℃.
3. Valves used for air separation package unit
As the air separation plant to produce oxygen, nitrogen gas process is carried out at -183 ℃ low temperature, so air separation plant has extremely high request for valves. The common valves used for air separation package units are as follows:
(1) Cryogenic valves
Size range from DN1.5~900mm,pressure 0.2~16.0MPa,lowest operating temperature is -183℃.
(2) One million scale synthesis ammonia plant, except for general valve like gate,check,globe ,butterfly,globe valve,also need some special valve,such as high temperature flat gate valve whose temperature is 550 ℃, nominal pressure is 1.6 ~ 40.0MPa, the nominal size is DN50 ~ 1200mm.
(3) Alkylbenzene and acrylonitrile need ultra-low carbon corrosion-resistant stainless steel valves, duplex stainless steel valves, Inconel valve and Hastelloy valve.
(4) Air separation unit using -196 ℃ low temperature valve and the oxygen globe valve or oxygen ball valve, the nominal pressure PN ≤ 16.0MPa, nominal size DN ≤ 900mm.
These valves should be absolutely no internal and external leakage, completely reliable sealed.