US 4,379,046 AGranted

Integrated two stage coking and steam cracking process and apparatus therefor

AssigneeExxon Research & Engineering Co.

InventorMorey E. Oldweiler

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Abstract

The invention relates to an improvement in an integrated, two stage coking and steam cracking process for the production of unsaturated light hydrocarbons. A heavy hydrocarbonaceous oil is first coked in a fluid coking zone. High temperature cracking in the presence of steam is carried out on the vaporous coker conversion product by injecting into the vapors a stream of hot coke particles at a sufficient temperature and in sufficient amount to raise the coker vapors to steam cracking temperature and supply the endothermic heat of reaction. Solids are separated from gas in a gas-solids separation zone such as one or more cyclones and sent to the fluid coking zone and the gas is quenched to stop olefin degradation reactions. According to the improvement, a portion of the separated solids is diverted from entering the fluid coking zone so that the amount of separated solids it receives is only sufficient to satisfy its heat requirement. Solids may be diverted via the cyclone dipleg. An internal standpipe connected to the cyclone dipleg and having a valve and associated riser may be used to regulate the amount of separated solids permitted to enter the fluid coking zone.

Claims14

Dependent claims

In an integrated, two stage coking and steam cracking process for the production of products including low molecular weight unsaturated hydrocarbons in which

(a) a carbonaceous material is reacted in a reactor in a first stage coking zone containing a bed of fluidized solids wherein steam is introduced to obtain a superficial fluidizing gas velocity in the range of 0.5 to 5 feet per second, maintained at fluid coking conditions including a temperature in the range of about 950.degree. F. to about 1150.degree. F. to form a vaporous coking zone conversion product and coke, said coke depositing on said fluidized solids;
(b) said vaporous coking zone conversion product is passed with entrained solids to a second stage reaction zone;
(c) hot solids at a sufficient temperature and in sufficient amount are introduced into said conversion product entering said second stage reaction zone to raise the conversion product to steam cracking temperatures within the range of 1200.degree. to 1700.degree. F. and supply the endothermic heat of reaction;
(d) solids are separated from product gas within the reactor;
(e) products are recovered comprising low molecular weight unsaturated hydrocarbons, the improvement which comprises:
(f) withdrawing from the reactor a portion of separated solids and preventing its entry into said first stage coking zone;
allowing another portion to enter said coking zone and regulating the ratio between the amount of solids withdrawn and the amount of solids allowed to enter said coking zone to maintain the coking zone within said temperature range.

4 more elements

In an integrated, two stage coking and steam cracking process for the production of products including low molecular weight unsaturated hydrocarbons in which

(a) a carbonaceous material is reacted in a reactor in a first stage coking zone containing a bed of fluidized solids wherein steam is introduced to obtain a superficial fluidizing gas velocity in the range of 0.5 to 5 feet per second, maintained at fluid coking conditions including a temperature in the range of about 950.degree. to about 1100.degree. F. to form a vaporous coking zone conversion product and coke, said coke depositing on said fluidized solids;
(b) a portion of said solids with the coke deposition thereon is introduced into a heating zone maintained at a temperature of from about 1050.degree. to about 1150.degree. F.;
(c) a portion of solids from said heating zone is introduced into a fluid bed gasification zone maintained at a temperature in the range of about 1600.degree. to about 1800.degree. F.;
(d) said vaporous coking zone conversion product is passed with entrained solids to a second stage reaction zone;
(e) a portion of hot solids is withdrawn from the gasification zone;
(f) said hot solids are brought into contact with said vaporous conversion product entering said second stage reaction zone to raise said conversion product to steam cracking temperatures within the range of about 1300.degree. to 1500.degree. F., solids are separated from product gas within the reactor, separated solids are passed to the coking zone and separated product gas comprising low molecular weight unsaturated hydrocarbons is quenched and recovered, the improvement which comprises:
(g) withdrawing a portion of said separated solids and preventing it from entering said coking zone, allowing another portion to enter said coking zone and regulating the ratio between the amount of solids withdrawn and the amount of solids allowed to enter said coking zone to maintain the coking zone within said temperature range.

4 more elements

A cocracking reactor which comprises, in combination,

a vessel for holding reactants including at least one fluidized bed of coke being a first stage coking zone;
means for introducing feed and fluidizing gas into the bed;
a duct adapted to receive vaporous coking zone conversion product being part of a second stage cracking zone;
means for introducing hot solids into said duct;
gas-solids separation means including at least one cyclone, in open communication with said duct;
an internal standpipe connected to the cyclone dipleg to receive separated solids therefrom and having an outlet for overflow of solids into the bed and an external riser for solids removal;
valve means in the standpipe for regulating the ratio of distribution of separated solids between the overflow outlet and the external riser;
and
means for removing cold coke from the vessel.

6 more elements

Dependencies are inferred from the claim text.