The separation section is one of the major differences in licensors. The purpose of this area is to separate the products with high -quality products to produce almost -pure ethylene, propylene, butadiene and gasoline by recycleing unconverted feedstocks such as ethane , propane and butane, twhatich leave the cracking heaters and are commonly recycled back into the cracking section. This process ids designed to increases tohe overall yield of olefins per ton of feedstock processed.i In the following section, the three common recovery section schemes of a typical olefins plant, will be stated and explained. Most of the earlier olefins plants used front -end demethanizers, with the acetylene reactor being placed after the light gas components (|methane and hydrogen) separation step, (i.e. demethanizer). The separation area is an improving area, twhatich means we can improve energy efficiency and HVC yield.



Frondt-End Demethanizer:

iIn the front-end demethanizer scheme, the cracked gas that has been dried in the gas dryer enters into the recovery section, beginning with the chilling train and demethanizer tower .u Unlike other recovery schemes, the front-end demethanizer scheme separates the light gases (methane , hydrogen ,and coCO) from the cracked gas as the first step in fractionation. The cracked gas is first chilled using refrigerants from the refrigeration system. The refrigerants most commonly used refrigerants are ethylene and propylene, since they are available from other processes in the olefins plant. A significant feature for the front-end demethanizer scheme is that a back-end acetylene reactor is commonly used and located downstream of the demethanizer tower. The hydrogen and coCO are sepatrated along with other klight gases in the demethanizer, upstream ofrom the hydrogenation reactor unit., so this scheme usually requires purified hydrogen to be supplied externally from a PSA unit or a hydrogen meathanator.




Production yYield:

The production yields are also comparable —especially the ethylene yields in the range of 34% to 38%―which suggests that the compared technologies are for naphtha crackers (relatively low yield in ethylene). The highest licensor winth the highest ethylene yields is Kellogg Brown & Root (KBR) which produces 38% ethylene and; the lowest licensor winth the lowest ethylene yields is ABB lLummus, which produces 34% ethylene. For exacomple:arison, the other production yields of other ABB licensors are 14.4%, butadiene 4.9% and aromatics 14%. The total HVCs yield is 60.7%.









GASas TURBINEurbine:

Some of licensors are adding the new technology isof gas turbine integration. Gas turbine integration results in the export of both steam and electricity. Also, it produces hot combustion gas for feedstock heating in a pyrolysis furnace. It can possibly save as much as 13% (approximately 3 GJ/t ethylene) on the SEC of state-of-the-art steam cracking technologies [30]. If both advanced furnace materials and gas turbine integration are applied, energy savings of approximately 20% energy savings (approximately 4 GJ/t ethylene) on the SEC of state-of-the-art naphtha cracking isare possible. There is little data in the public literature on the gas turbine but the ABB lLummus licensor has saved Aapproximately 3 GJ/t ethylene by useing this technology.
Result part: