Apparatus and method for recovering light hydrocarbons from hydrogen containing gases
First Claim
1. An apparatus comprising:
- elements designed, dimensioned and arranged for recovering ethylene from a cracked gas containing ethylene, methane and hydrogen, said apparatus including,(a) a rectifier tower through which the cracked gas passes;
(b) an overhead line extending from the rectifier tower;
(c) a refrigeration system in communication with the rectifier tower, said refrigeration system comprising;
indirection heat exchange means in communication with said rectifier tower for cooling and partially condensing an overhead vapor passing from said rectifier tower overhead line through the hot side of said indirect heat exchange means;
an expansion means in communication with said heat exchange means for expanding the non-condensed portion of the partially condensed overhead vapor discharged from the hot side of the heat exchange means and recirculating said non-condensed portion to the cold side of said indirect heat exchange means for refrigeration; and
(d) a reflux means in communication with the hot side of said indirect heat exchange means and said rectifier tower for directing the condensed portion of the partially condensed rectifier tower overhead vapor from the hot side of the heat exchange means to the rectifier tower for reflux, thereby producing an ethylene rich bottoms product from said rectifier tower.
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Abstract
A process and apparatus provide enhanced recovery of ethylene, hydrogen and methane from the effluent produced by cracking olefins. A cracked gas is fractionally condensed in several stages. The overhead vapor from the last stage is refluxed in a rectifier tower to enable recovery of residual light hydrocarbons such as ethylene in the cracked gas and for improving the purity and yield of hydrogen. The refrigeration for producing the reflux is obtained by expanding a portion of the overhead vapor from the rectifier tower. Preferably, the fractional condensates of the cracked gas and the ethylene rich bottoms product from the rectifier tower are directed to a demethanizer. The overhead vapor from the demethanizer can be directed to the rectifier tower for recovery of ethylene contained therein.
12 Citations
18 Claims
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1. An apparatus comprising:
- elements designed, dimensioned and arranged for recovering ethylene from a cracked gas containing ethylene, methane and hydrogen, said apparatus including,
(a) a rectifier tower through which the cracked gas passes; (b) an overhead line extending from the rectifier tower; (c) a refrigeration system in communication with the rectifier tower, said refrigeration system comprising; indirection heat exchange means in communication with said rectifier tower for cooling and partially condensing an overhead vapor passing from said rectifier tower overhead line through the hot side of said indirect heat exchange means;
an expansion means in communication with said heat exchange means for expanding the non-condensed portion of the partially condensed overhead vapor discharged from the hot side of the heat exchange means and recirculating said non-condensed portion to the cold side of said indirect heat exchange means for refrigeration; and(d) a reflux means in communication with the hot side of said indirect heat exchange means and said rectifier tower for directing the condensed portion of the partially condensed rectifier tower overhead vapor from the hot side of the heat exchange means to the rectifier tower for reflux, thereby producing an ethylene rich bottoms product from said rectifier tower. - View Dependent Claims (2, 3, 4, 5, 6, 7)
- elements designed, dimensioned and arranged for recovering ethylene from a cracked gas containing ethylene, methane and hydrogen, said apparatus including,
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8. A method for recovering ethylene from a cracked gas comprised of ethylene, methane and hydrogen comprising the steps of:
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(a) directing a stream of the cracked gas to a rectifier tower; (b) removing an overhead vapor from said rectifier tower; (c) directing the overhead vapor from said rectifier tower through the hot side of an indirect heat exchanger; (d) cooling and partially condensing said overhead vapor in the hot side of said heat exchanger; (e) expanding and recirculating the non-condensed portion of the overhead vapor to the cold side of the indirect heat exchanger; (f) refluxing the rectifier tower with the condensed portion of the overhead vapor; and (g) recovering ethylene as a bottoms product from said rectifier tower. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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Specification