US 7,582,201 B2Granted

Controlling tar by quenching cracked effluent from a liquid fed gas cracker

AssigneeExxonMobil Chemical Patents Inc.

InventorsJames N. McCoy, Barrington M. Hammond, David J. Duhon, Mark A. Rooney, Robert D. Strack, John R. Messinger

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Abstract

In a system for thermal cracking gaseous feedstocks, the system including a gas cracker for producing an effluent comprising olefins, at least one transfer line exchanger for the recovery of process energy from the effluent and a water quench tower system, a process for extending the range of system feedstocks to include liquid feedstocks that yield tar is provided. The process includes the steps of injecting a first quench fluid downstream of a primary transfer line exchanger to quench the process effluent comprising olefins, separating in a first separation vessel a cracked product and a first byproduct stream comprising tar from the quenched effluent, directing the separated cracked product to a water quench tower system and quenching the separated cracked product with a second quench fluid to produce a cracked gas effluent for recovery and a second byproduct stream comprising tar. An apparatus for carrying out such process is also provided.

Claims21

Dependent claims

A process for cracking liquid hydrocarbon feed in a system for cracking gaseous hydrocarbons, the process comprising the steps of:

(a) feeding a liquid hydrocarbon feed stream to a thermal cracker to provide a vaporized hydrocarbon feed stream;
(b) cracking the vaporized hydrocarbon feed stream in the thermal cracker to produce a cracked effluent;
(c) feeding the cracked effluent from the thermal cracker to a primary transfer line heat exchanger (TLE);
(d) feeding a first quench fluid into the cracked effluent from the primary TLE to quench the cracked effluent;
(e) feeding a mixture of the cracked effluent from the primary TLE and the first quench fluid to a first separator;
(f) separating the effluent/first quench fluid mixture in the first separator to separate the mixture into a first separator bottoms stream comprising tar and a first separator product stream;
(g) feeding the first separator product stream to a second separator;
(h) feeding a second separator quench fluid to the second separator to quench the first separator product stream in the second separator;
(i) separating in the second separator, a second separator bottoms stream comprising tar and a second separator product stream comprising an olefin product;
and
(j) recovering an olefin product from the second separator product stream;
and
further comprising the step of treating the second separator bottoms stream with added light aromatic solvent in a solvation process to separate tar from at least one of water, solvent, and quench oil, wherein the step of treating the second separator bottoms stream in a solvation process comprises:
(i) treating the second separator bottoms in a quench drum;
and
(ii) recovering from the quench drum, the second quench fluid;
and the added light aromatic solvent is added to at least one of the second separator bottoms and the recovered second quench fluid.

14 more elements

In a thermal gas cracker system for cracking gaseous feedstocks, the system including (i) a thermal gas cracker for producing a process effluent comprising olefins;

(ii) a primary transfer line exchanger (TLE) for the recovery of process energy from the effluent;
and (iii) a quench tower system, a process for thermally cracking liquid feedstocks that yield tar in a cracked effluent from the thermal cracker, said process comprising the steps of:
(a) feeding the liquid hydrocarbon feed to a thermal cracker to preheat the feed;
(b) feeding the preheated feed from the thermal cracker to a flash separation apparatus to separate an overhead feed stream from a non-volatile bottoms stream;
(c) feeding the overhead feed stream to the thermal cracker for cracking to produce the process effluent;
(d) removing the non-volatile bottoms stream from the flash separation apparatus;
(e) feeding a first quench fluid into the cracked effluent downstream of the TLE to fluid quench the cracked effluent from the thermal cracker;
(f) separating the quenched effluent in a first separator into a first separator product stream comprising olefins and a first separator byproduct stream comprising tar;
(g) feeding the first separator product stream to the quench tower system;
(h) quenching the first separator product stream in the quench tower system with a second quench fluid;
(i) recovering from the quench tower system, a cracked product effluent comprising olefins and a second byproduct stream comprising tar;
(j) directing the second byproduct stream to a tar solvation system;
and
(k) separating the second byproduct stream in the tar solvation system to which is added a light aromatic solvent in an amount sufficient to keep the tar solvated, into a third byproduct stream comprising tar from at least one of water, quench oil, and solvent.

11 more elements

A process for cracking liquid hydrocarbon feed in a system for cracking gaseous hydrocarbons, the process comprising the steps of:

(a) feeding a liquid hydrocarbon feed stream to a thermal cracker to provide a vaporized hydrocarbon feed stream;
(b) cracking the vaporized hydrocarbon feed stream in the thermal cracker to produce a cracked effluent;
(c) feeding the cracked effluent from the thermal cracker to a transfer line heat exchanger (TLE) comprising a primary TLE and a bypassable secondary TLE downstream of the primary TLE;
(d) feeding a first quench fluid into the cracked effluent from the transfer line heat exchanger to quench the cracked effluent;
(e) feeding a mixture of the cracked effluent from the transfer line heat exchanger and the first quench fluid to a first separator;
(f) separating the effluent/first quench fluid mixture in the first separator to separate the mixture into a first separator bottoms stream comprising tar and a first separator product stream;
(g) feeding the first separator product stream to a second separator;
(h) feeding a second separator quench fluid to the second separator to quench the first separator product stream in the second separator;
(i) separating in the second separator, a second separator bottoms stream comprising tar and a second separator product stream comprising an olefin product;
(j) recovering an olefin product from the second separator product stream;
and
(k) treating the second separator bottoms stream in a solvation process to which is added a light aromatic solvent in an amount sufficient to keep the tar solvated, and the solvation process further comprising:
(i) treating the second separator bottoms stream in a quench drum;
and
(ii) recovering from the quench drum, the second separator quench fluid.

12 more elements

Dependencies are inferred from the claim text.