Adiabatic reactor to produce olefins
Processes for production of olefins from hydrocarbon feedstocks are provided. In one aspect, the processes of the present invention utilize coils passing through a pyrolysis furnace to partially convert a hydrocarbon feedstock to olefins, followed by further conversion of the hydrocarbon feedstock in an adiabatic reactor. A portion of the coils in the pyrolysis furnace carry the hydrocarbon feedstock and the remainder carry steam only. After a selected period of time, the material flowing through the coils is switched. By flowing steam through the coils that had previously contained the hydrocarbon feedstock, on-line decoking can occur. In another aspect, a high temperature reactor is used to convert methane or natural gas to olefins.
1. A process for producing olefins from a hydrocarbon feed comprising the steps of:
(a) providing a pyrolysis furnace having one or more first coils and one or more second coils;
(b) feeding the hydrocarbon feed to the one or more first coils;
(c) feeding steam alone to the one or more second coils;
(d) heating the first and second coils in the pyrolysis furnace, wherein the temperature of the steam at the outlet of the second coils is in the range from about 900° C. to about 1100° C., the temperature at the outlet of the first coils is in the range from about 700° C. to about 800° C., and the residence time in the first coils is in the range from about 100 to about 800 milliseconds;
(e) combining the outlet of the first and second coils to form a combined hydrocarbon/steam stream;
(f) feeding the combined hydrocarbon/steam stream to an adiabatic reactor; and
(g) quenching the outlet stream from the adiabatic reactor in a quenching unit.
2. The process of claim 1 further comprising the step of:
(h) after a predetermined period of time, feeding steam through the one or more first coils and feeding hydrocarbon feed through the one or more second coils.
3. The process of claim 2 , further comprising the step of adding dilution steam to the hydrocarbon feed as it is fed to the one or more first coils and the one or more second coils.
4. The process of claim 3 , wherein the ratio of dilution steam to hydrocarbon feed is from 0.1 to 1.0 by weight.
5. The process of claim 2 , wherein the number of first coils and the number of second coils is equal.
6. The process of claim 1 , wherein the hydrocarbon feed is heated to a temperature of at least 750° C. in the pyrolysis furnace.
7. The process of claim 1 , further comprising the steps of:
(i) feeding the quenching unit with preheated water; and
(j) generating steam in the quenching unit.
8. The process of claim 7 , wherein the quenching unit is a transferline exchanger.
9. A process for producing olefins from a hydrocarbon feed comprising the steps of:
(a) providing a pyrolysis furnace having one or more first coils and one or more second coils, wherein the pyrolysis furnace has a convection zone and a radiant zone;
(b) feeding the hydrocarbon feed to the one or more first coils such that the hydrocarbon feed is preheated in the convection zone;
(c) feeding steam alone to the one or more second coils;
(d) heating the first and second coils in the pyrolysis furnace, wherein the temperature of the steam at the outlet of the second coils is in the range from about 900° C. to about 1100° C., the temperature at the outlet of the first coils is in the range from about 700° C. to about 800° C., and the residence time in the radiant zone is in the range from about 100 to about 800 milliseconds;
(e) combining the outlet of the first and second coils to form a combined hydrocarbon/steam stream;
(f) feeding the combined hydrocarbon/steam stream to an adiabatic reactor; and
(g) quenching the outlet stream from the adiabatic reactor in a quenching unit.
10. The process of claim 9 further comprising the step of:
(h) after a predetermined period of time, feeding steam through the one or more first coils and feeding hydrocarbon feed through the one or more second coils such that the hydrocarbon feed is preheated in the convection zone.
11. The process of claim 10 , further comprising the step of adding dilution steam to the hydrocarbon feed as it is fed to the one or more first coils and the one or more second coils.
12. The process of claim 11 , further comprising the steps of:
(i) feeding the quenching unit with preheated water; and
(j) generating steam in the quenching unit.
13. The process of claim 11 , wherein the quenching unit is a transferline exchanger.