H2-CO separation cold box(HYCO cold-box, Liquid methane wash)
Carbon monoxide is an important chemical which can be used for the synthesis of a variety of high value added products, such as acetic acid, acetic anhydride, formic acid, dimethyl formamide, light gas and metal carbonyl compounds, etc.
To get high purity carbon monoxide, cryogenic separation process could be used. Cryogenic separation is to separate various components based on their different boiling points. According to the different contents in feed gas from coal gasification unit or natural gas cracking furnace, we use different combinations to realize separation and purification. From the HY-CO cold box, we get pure carbon monoxide(CO) and pure hydrogen and off-gas. This kind of cold box is utilized to realize separation process to minimize investment and provide required product gas for down stream processing.
(1) Olefin(ethylene) cold box
Olefin(ethylene) cold box is used in ethylene plant to get required streams to meet with down stream temperature requirement. Enti has the technology and capability for supply of ethylene cold box and column overhead condenser( PFV) based on different ethylene process like Lumus, SW and Linde process. Our aim is to persistently research and innovate new technology for the long-standing, safe, reliable and efficient operation of ethylene plant.
(2) Propane dehydrogenation (PDH) cold box
Propane dehydrogenation (PDH) is a strong heat absorption process, which can produce good propylene yield under high temperature and relatively low pressure. At the moment, there are several process like Oleflex process from UOP, Catofin process from Lummus and STAR process from Krupp, which have been commercialized. Often propylene and ethylene are used in the propane dehydrogenation (PDH) process to realize gradual cooling and separate olefins. In the low temperature section, we use multi-stream heat exchanger and cold box.
(3) Light hydro-carbon recovery and fractionation cold box( Recover C2+ from NG)
Light hydro-carbon or natural gas liquid(NGL) is obtained from natural gas. In the obtaining process, cold box will be needed as part of the system to separate C2+ from natural gas. NGL is the source material of down steam industry such as propane cracking device and PDH system.
(4) Liquid nitrogen wash cold box
Application of liquid nitrogen wash process: the feed gas of synthetic ammonia contains nitrogen and hydrogen, as well as impurities like carbon monoxide, argon and sulfides, which could not satisfy the requirements of subsequent process. Normally rectisol plus liquid nitrogen wash process will be used to remove these impurities. Liquid nitrogen wash process is a cryogenic purification method, using cryogenic distillation to obtain high purity hydrogen, then mix hydrogen and nitrogen by 3:1 to be used for ammonia synthesizing. Particularly the output from cryogenic liquid nitrogen wash device has carbon monoxide content less than 2 ppm, which effectively improves the efficiency of the synthetic ammonia catalyst, reduces the synthesis pressure, eliminate venting gas, so as to achieve the effect of energy saving and long period operation, low emissions. Enti has mature technology for design, manufacture, installation and commission of liquid nitrogen wash cold box.
(5) Argon and hydrogen recovery cold box from tail gas
The tail gas released from synthetic ammonia industry is recycled to produce liquefied natural gas(LNG), hydrogen-rich gas and other products such as high purity liquid argon through pre-purification, refrigeration, distillation and separation process. Among them, recycling nitrogen expending, or single mixed refrigerant cycling(SMRC) and/or liquid nitrogen throttling process is adopted for refrigeration, which has the advantage of low energy consumption, large operation flexibility, stable and easy operation. Based on different components in tail gas and different product requirement, appropriate process will be selected to suite client need.
(6) Plate-fin in Vessel（PFV）
In ethylene plant and some other chemical plant, there are a lot of columns, such as stripper columns and distillation columns. At the request of heat transfer and mass transfer, process needs to set a condenser at the top of the column to provide a return flow liquid and a reboiler at the bottom of the column to provide upward gas. In many columns we also set a condenser in the middle of the column.
Column overhead condenser uses a structure with plate-fin heat exchanger in side a stainless steel cylinder, to be called PFV (plate-fin in vessel). The gas (warm stream) enters heat exchanger through nozzle and inlet header, and transfer heat with the cold stream, to be cooled and condensed and becomes vapor-liquid two-phase, then goes out of column overhead condenser through outlet header and nozzle. The vapor-liquid two-phase stream enters into a separator to separate vapor and liquid. Liquid as a return flow goes back to the column top and vapor goes out of the top of separator to be sent to the next equipment. Refrigerant is arranged in the vessel and the plate-fin heat exchanger will be submerged wholly or partly inside the refrigerant.
PFV is a kind of built-in type thermosiphon heat exchanger, and could be placed vertically, as well as horizontally.
PFV is a typical example that plate-fin heat exchanger which replaces shell-tube heat exchanger.
