Capacity: 150,000 MTPY
Run Time: 100,000 hours (12 years)
Built under Kellog-USA license
DCS Process Control System Included
The feedstock for the Ethylene production is nafta. All ethane and propane are recycled to the cracking unit until their complete conversion. As an alternative, up to 8,750 kg / h propane and butane (LPG) may be used as fuel for the unit. The unit design make it possible a start up without Flare.
The cracking furnaces are designed for selective cracking of the feedstock to give the desired products with high energy efficiency. The feedstock Nafta is mixed with ethane and propane and is cracked in (6) single millisecond furnaces 101 BF - BA 101.
Nafta is heated in the heat exchanger by the hot cracking resin coming from the first separation column circulation loop. The nafta flow is split in (2) streams and go to the furnaces and partially evaporates in the convection section of furnace before mixing with the recycle stream of ethane.. The streams of recycling ethane and propane are heated in the heat exchanger by the hot cracking resin. The partially evaporated nafta with ethane and propane are mixed with stem with ratio hydrocarbons/vapor as 0.5/1. The mixture of feedstock with the steam is preheated in the convection section of the furnace up to the temperature which is slightly lower than the cracking temperature.
The preheated stream arrives in the cracking section where the feedstock is cracked to give the desired products. Every furnace has (96) tubes ((48) tubes for each stream). The gases after the furnace are quickly cooled in the primary waste heat boilers 101 BC, A to F. Each furnace has (24) primary non-polluting waste-heat boilers. The cracking gases are cooled to the temperature low enough to stop the cracking reaction and to produce high-pressure steam. The gases from each furnace after the primary heat-recovery boilers are further cooled in the secondary waste heat boilers, where the high-pressure steam is also produced . The gases coming out of the (6) secondary heat recovery boilers are mixed and fed into the primary separation column 101. The vapors from the top of the primary condenser are fed to the cracking gas compressor 201. Compression is necessary to separate hydrogen from methane and ethylene at acceptable temperatures. There is a 5-stage cooling system with interstage cooling. Gases from the 4th stage of the cracking gas compressor for are cooled to separate the hydrocarbon condensate and then warmed before it enters the column with an alkali 201 for of acid gases removal. Gases after the fifth stage of the cracking gas compressor go to the cracking gas dryer 201 OA / OB, where they are dried to a residual water content of less than 0.1 ppm. Gases from the dryer go to the separation column 301 E. Separation column separates methane and hydrogen from the C2 and heavier hydrocarbons, that come out of the bottom of the column.Gases rich with methane and a certain quantity of fluid from the reservoir comes through the heat exchangers 316, 315 C and 313 C. After that heat exchange this exhaust gas is used as fuel in furnaces.
The bottom product of the separation column is fed to the column 302 E, where C2 products are separated from C3 products. Products from the top of the column are cooled by propylene and partially condensed to provide reflux for the column. The vapors from the top of the column containing the total amount of acetylene, ethane-ethylene fraction and small amounts of propylene, acetylene go to the reactors. Products from the top of ethane separation column is mixed with hydrogen and enters the system of acetylene hydrogenation reactors. When the gas stream passes through a catalyst in the reactor all the acetylene reacts with hydrogen to form ethylene and ethane. Some unwanted reactions may accur leading to the formation of heavier products, such as "green oil" (usually about 300 ppm). After that, the flow enters the separator for the "green oil", where "green oil" is removed, and periodically served in the fractionators. To prevent the ice formation and clogging of the ethylene column special security dryers are installed after the "green oil" separator . After the dryers the vapors are sent to the ethylene tower where the polymerization quality ethylene is separated from ethane.
Liquid ethylene is extracted from the side outlet of the column. Ethylene is evaporated and superheated to 347 - 348ºC.
The bottom product from ethane column goes to the propane column 304 E, where the C3 and lighter hydrocarbons are separated from heavier products. Products from the top of the propane column go to the reactors 303 OA / OB / OS, where the remaining acetylene derivatives and be-olefins are hydrogenated to propane and propylene. Products from the reactors 303 OA / OB / OS are fed to the propylene column . 94%- purity propylene is separated from the side outlet of the column. The bottom product of the column is propane with small amounts of propylene, which is recycled to the furnaces for cracking.
The bottom product of propane column enters the butane column 306 E, where the mixed C4 fraction is separated from heavier components. The bottom products of butane columns are mixed with the bottoms of the pyrolysis gasoline stripping columns then cooled and pumped to the boundaries of the installation as a commercial product. As well as products from the top of butane column are mixed with C4 fraction is pumped to the storage tank.
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