Claims
- 1. A coking process wherein a sludge material is passed into a coking zone and a heavy hydrocarbon feed comprising residual oil is also passed into a coking zone at coking conditions, to effect production of solid coke and lighter hydrocarbon products derived from the feed which comprises: (1) contacting feed, liquid derived from the feed, or vapor derived from the feed with oxygen at oxidation conditions to effect oxidation of a portion of the feed, liquid derived from the feed, or vapor derived from the feed, (2) contacting the sludge with oxygen to form a mixture, and (3) passing the mixture into the coking zone during the coke production cycle at thermal treatment conditions to contact at least a portion of the feed, liquid derived from the feed, or vapor derived from the feed.
- 2. The process of claim 1 further characterized in that feed contacts oxygen and effects oxidation of the feed.
- 3. The process of claim 1 further characterized in that liquid derived from the feed contacts oxygen and effects oxidation of the liquid derived from the feed.
- 4. The process of claim 1 further characterized in that vapor derived from the feed contacts oxygen and effects oxidation of said vapors.
- 5. The process of claim 1 further characterized in that the feed is passed through a furnace to be heated, thereafter passed through a transfer line and into the coking zone and oxygen contacts the feed passing through the transfer line to effect oxidation of a portion of the feed in the transfer line.
- 6. The process of claim 1 further characterized in that the mixture is added to the coking zone as a stream separate from the feed and contacts the vapor in the coking zone.
- 7. The process of claim 1 further characterized in that the mixture is added to the coking zone as a stream separate from the feed and contacts the liquid derived from the feed in the coking zone.
- 8. The process of claim 1 further characterized in that oxygen contacts feed to effect oxidation of a portion of the feed and said mixture of sludge and oxygen thereafter contacts feed.
- 9. The process of claim 1 further characterized in that at least a portion of said feed boils in the range of from about 850.degree. F. up to about 1250.degree. F. or higher; said coking conditions include a feed temperature of from about 850.degree. F. to about 970.degree. F., a coking zone pressure of from about atmospheric to about 250 psig, and a coking zone vapor residence time of from about a few seconds up to ten or more minutes; and a sludge addition rate of from about 0.01 to about 10 percent by weight, based on the feed addition rate to the coking zone.
- 10. The process of claim 1 further characterized in that said process is a delayed coking process having an elongated vertically positioned coke drum containing an upper section and a lower section, the feed is a residual feed which is passed through a furnace to be heated, the heated feed is thereafter passed through a transfer line comprising a conduit and into a lower section of the coke drum, solid coke is contained in the lower section and vapor is contained in the upper section, and wherein vapor is removed from the coke drum through a vapor outlet connected to said upper section, oxygen is introduced into feed passing through the transfer line at oxidation conditions, and the mixture of sludge and oxygen is passed into the transfer line to contact the feed at thermal treatment conditions.
- 11. The process of claim 1 further characterized in that said process is a delayed coking process having an elongated vertically positioned coke drum containing an upper section and a lower section, the feed is a residual feed which is passed through a furnace to be heated, the heated feed is thereafter passed through a transfer line comprising a conduit and into a lower section of the coke drum, a solid coke is contained in the lower section and vapor is contained in the upper section, and wherein vapor is removed from the coke drum through a vapor outlet connected to said upper section, oxygen is introduced into feed passing through the transfer line at oxidation conditions, and the mixture of sludge and oxygen is passed into the lower section of the drum to contact liquid derived from the feed at thermal treatment conditions.
- 12. The process of claim 1 further characterized in that said process is a delayed coking process having an elongated vertically positioned coke drum containing an upper section and a lower section, the feed is a residual feed which is passed through a furnace to be heated, the heated feed is thereafter passed through a transfer line comprising a conduit and into a lower section of the coke drum, solid coke is contained in the lower section and vapor is contained in the upper section, and wherein vapor is removed from the coke drum through a vapor outlet connected to said upper section, oxygen is introduced into feed passing through the transfer line at oxidation conditions, and the mixture of sludge and oxygen is passed into the upper section of the drum to contact vapor derived from the feed at thermal treatment conditions.
- 13. The process of claim 1 further characterized in that thermal treatment conditions include vaporization of at least a portion of the sludge and combustion of at least a portion of hydrocarbon contained in the sludge by the oxygen contacted with the sludge.
- 14. The process of claim 13 further characterized in that oxygen contacted with the sludge is substantially consumed by said combustion of hydrocarbon contained in the sludge.
- 15. A coking process wherein a heavy hydrocarbon feed comprising residual oil is passed into a coking zone at coking conditions, to effect production of solid coke and lighter hydrocarbon products derived from said feed which comprises: (1) introducing into the feed prior to passage into the coking zone a gaseous stream comprising oxygen at conditions to effect oxidation of a portion of the feed, (2) contacting sludge with oxygen to form a mixture, and (3) passing said mixture into the coking zone during the coke production cycle at thermal treatment or vapor derived from the feed.
- 16. The process of claim 15 further characterized in that the mixture is added to the coking zone as a stream separate from the feed and contacts the vapor in the coking zone.
- 17. The process of claim 15 further characterized in that the mixture is added to the coking zone as a stream separate from the feed and contacts the liquid derived from the feed in the coking zone.
- 18. The process of claim 15 further characterized in that the mixture contacts feed.
- 19. The process of claim 15 further characterized in that said sludge is contacted with oxygen at thermal treatment conditions to effect oxidation of a portion of the sludge and thereafter passed into the coking zone.
- 20. The process of claim 15 further characterized in that said process is a delayed coking process having an elongated vertically positioned coke drum containing an upper section and a lower section, the feed is a residual feed which is passed through a furnace to be heated, the heated feed is thereafter passed through a transfer line comprising a conduit and into a lower section of the coke drum, solid coke is contained in the lower section and vapor is contained in the upper section, and wherein vapor is removed from the coke drum through a vapor outlet connected to said upper section, oxygen is introduced into feed passing through the transfer line at oxidation conditions, and the mixture of sludge and oxygen is passed into the transfer line to contact the feed at thermal treatment conditions.
- 21. The process of claim 15 further characterized in that said process is a delayed coking process having an elongated vertically positioned coke drum containing an upper section and a lower section, the feed is a residual feed which is passed through a furnace to be heated, the heated feed is thereafter passed through a transfer line comprising a conduit and into a lower section of the coke drum, solid coke is contained in the lower section and vapor is contained in the upper section, and wherein vapor is removed from the coke drum through a vapor outlet connected to said upper section, oxygen is introduced into feed passing the transfer line at oxidation conditions, and the mixture of sludge and oxygen is passed into the lower section of the drum to contact liquid derived from the feed at thermal treatment conditions.
- 22. The process of claim 15 further characterized in that said process is a delayed coking process having an elongated vertically positioned coke drum containing an upper section and a lower section, the feed is a residual feed which is passed through a furnace to be heated, the heated feed is thereafter passed through a transfer line comprising a conduit and into a lower section of the coke drum, solid coke is contained in the lower section and vapor is contained in the upper section, and wherein vapor is removed from the coke drum through a vapor outlet connected to said upper section, oxygen is introduced into feed passing through the transfer line at oxidation conditions, and the mixture of sludge and oxygen is passed into the upper section of the drum to contact vapor derived from the feed at thermal treatment conditions.
- 23. The process of claim 15 further characterized in that thermal treatment conditions include vaporization of at least a portion of the sludge and combustion of at least a portion of hydrocarbon contained in the sludge by the oxygen contacted with the sludge.
- 24. The process of claim 23 further characterized in that oxygen contacted with the sludge is substantially consumed by said combustion of hydrocarbon contained in the sludge.
- 25. A coking process wherein a heavy hydrocarbon feed comprising residual oil is passed into a coking zone at coking conditions, to effect production of solid coke and lighter hydrocarbon products from said feed which comprises: (1) contacting at least a portion of the liquid derived from the feed with oxygen at conditions to effect combustion in the coking zone of a portion of said liquid derived from the feed, (2) contacting sludge with oxygen to form a mixture, and (3) passing said mixture to the coking zone during the coke production cycle at thermal treatment conditions to contact at least a portion of the feed, liquid derived from the feed, or vapor derived from the feed.
- 26. The process of claim 25 further characterized in that the mixture is added to the coking zone as a stream separate from the feed and contacts the vapor in the coking zone.
- 27. The process of claim 25 further characterized in that the mixture is added to the coking zone as a stream separate from the feed and contacts the liquid derived from the feed in the coking zone.
- 28. The process of claim 25 further characterized in that said mixture thereafter contacts feed.
- 29. The process of claim 25 further characterized in that said sludge is contacted with oxygen at thermal treatment conditions to effect oxidation of a portion of the sludge and thereafter passed into the coking zone.
- 30. The process of claim 25 further characterized in that said process is a delayed coking process having an elongated vertically positioned coke drum containing an upper section and a lower section, the feed is a residual feed which is passed through a furnace to be heated, the heated feed is thereafter passed through a transfer line comprising a conduit and into a lower section of the coke drum, solid coke is contained in the lower section and vapor is contained in the upper section, and wherein vapor is removed from the coke drum through a vapor outlet connected to said upper section, oxygen is introduced into the lower section of the coke drum to contact liquid derived from the feed at oxidation conditions to effect oxidation of at least a portion of the liquid derived from the feed, and the mixture of sludge and oxygen is passed into the transfer line to contact the feed at thermal treatment conditions.
- 31. The process of claim 25 further characterized in that said process is a delayed coking process having an elongated vertically positioned coke drum containing an upper section and a lower section, the feed is a residual feed which is passed through a furnace to be heated, the heated feed is thereafter passed through a transfer line comprising a conduit and into a lower section of the coke drum, solid coke is contained in the lower section and vapor is contained in the upper section, and wherein vapor is removed from the coke drum through a vapor outlet connected to said upper section, oxygen is introduced into the lower section of the coke drum to contact liquid derived from the feed at oxidation conditions to effect oxidation of at least a portion of the liquid derived from the feed, and the mixture of sludge and oxygen is passed into the lower section of the coke drum to contact liquid derived from the feed at thermal treatment conditions.
- 32. The process of claim 25 further characterized in that said process is a delayed coking process having an elongated vertically positioned coke drum containing an upper section and a lower section, the feed is a residual feed which is passed through a furnace to be heated, the heated feed is thereafter passed through a transfer line comprising a conduit and into a lower section of the coke drum, solid coke is contained in the lower section and vapor is contained in the upper section, and wherein vapor is removed from the coke drum through a vapor outlet connected to said upper section, oxygen is introduced into the lower section of the coke drum to contact liquid derived from the feed at oxidation conditions to effect oxidation of at least a portion of the liquid derived from the feed, and the mixture of sludge and oxygen is passed into the upper section of the coke drum to contact vapor derived from the feed at thermal treatment conditions.
- 33. The process of claim 25 further characterized in that thermal treatment conditions include vaporization of at least portion of the sludge and combustion of at least portion of hydrocarbon contained in the sludge by the oxygen contacted with the sludge.
- 34. The process of claim 33 further characterized in that oxygen contacted with the sludge is substantially consumed by said combustion of hydrocarbon contained in the sludge.
- 35. A coking process wherein a heavy hydrocarbon feed comprising residual oil is passed into a coking zone at coking conditions, to effect production of solid coke and lighter hydrocarbon products comprising liquid and vapor derived from derived from said feed which comprises: (1) contacting at least a portion of the vapor derived from the feed with oxygen at conditions to effect combustion in the coking zone of a portion of said liquid derived from the feed, (2) contact the sludge with oxygen to form a mixture, and (3) passing the mixture into the coking zone during the coke production cycle at thermal treatment conditions to contact at least a portion of the feed, liquid derived from the feed, or vapor derived from the feed.
- 36. The process of claim 35 further characterized in that the mixture is added to the coking zone as a stream separate from the feed and contacts the vapor in the coking zone.
- 37. The process of claim 35 further characterized in that the mixture is added to the coking zone as a stream separate from the feed and contacts the liquid derived from the feed in the coking zone.
- 38. The process of claim 35 further characterized in that the mixture thereafter contacts feed.
- 39. The process of claim 35 further characterized in that said process is a delayed coking process having an elongated vertically positioned coke drum containing an upper section and a lower section, the feed is a residual feed which is passed through a furnace to be heated, the heated feed is thereafter passed through a transfer line comprising a conduit and into a lower section of the coke drum, solid coke is contained in the lower section and vapor is contained in the upper section, and wherein vapor is removed from the coke drum through a vapor outlet connected to said upper section, oxygen is introduced into the upper section of the coke drum to contact vapor derived from the feed at oxidation conditions to effect oxidation of at least a portion of the vapor derived from the feed, and the mixture of sludge and oxygen is passed into the transfer line to contact the feed at thermal treatment conditions.
- 40. The process of claim 35 further characterized in that said process is a delayed coking process having an elongated vertically positioned coke drum containing an upper section and a lower section, the feed is a residual feed which is passed through a furnace to be heated, the heated feed is thereafter passed through a transfer line comprising a conduit and into a lower section of the coke drum, solid coke is contained in the lower section and vapor is contained in the upper section, and wherein vapor is removed from the coke drum through a vapor outlet connected to said upper section, oxygen is introduced into the upper section of the coke drum to contact vapor derived from the feed at oxidation conditions to effect oxidation of at least a portion of the vapor derived from the feed, and the mixture of sludge and oxygen is passed into the lower section of the coke drum to contact liquid derived from the feed at thermal treatment conditions.
- 41. The process of claim 35 further characterized in that said process is a delayed coking process having an elongated vertically positioned coke drum containing an upper section and a lower section, the feed is a residual feed which is passed through a furnace to be heated, the heated feed is thereafter passed through a transfer line comprising a conduit and into a lower section of the coke drum, solid coke is contained in the lower section and vapor is contained in the upper section, and wherein vapor is removed from the coke drum through a vapor outlet connected to said upper section, oxygen is introduced into the upper section of the coke drum to contact vapor derived from the feed at oxidation conditions to effect oxidation of at least a portion of the vapor derived from the feed, and the mixture of sludge and oxygen is passed into the upper section of the coke to contact vapor derived from the feed at thermal treatment conditions.
- 42. The process of claim 35 further characterized in that thermal treatment conditions include vaporization of at least portion of the sludge and combustion of at least a portion of hydrocarbon contained in the sludge by the oxygen contact with the sludge.
- 43. The process of claim 42 further characterized in that oxygen contact with the sludge is substantially consumed by said combustion of hydrocarbon contained in the sludge.
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a continuation-in-part application based on copending application U.S. Ser. No. 285,110, filed Dec. 15, 1988, which is a continuation in part of application U.S. Ser. No. 937,990, filed Dec. 4, 1986, the latter abandoned, all the contents of which are incorporated into this application by specific reference thereto.
1. Field of the Invention
The field of art to which this invention pertains is hydrocarbon coking operations in which feed, a liquid derived from the feed, or a vapor derived from the feed is contacted with oxygen at oxidation conditions to effect oxidation of a portion of the contacted material, and a mixture of sludge and oxygen is contacted with oxygen. The mixture of sludge and oxygen is contacted with at least a portion of the feed, liquid derived from the feed, or vapor derived from the feed in the coking zone.
2. General Background
Waste water sludge is produced in many industrial operations. Sludge production from a typical refinery or petrochemical plant can come from many sources including API separator bottoms, slop oil, emulsions, storage tank bottoms, sludge from heat exchangers, oily waste, MEA reclaimer sludges, and other waste materials produced in the refinery. The typical sludge will contain solids, which may be organic, inorganic or combinations of both, oil, and aqueous materials.
This sludge often contains hazardous materials which makes its disposal difficult and expensive. In most refinery or petrochemical operations the sludge-containing streams are sent to an API separator for gross removal of water and hydrocarbons after which the water and concentrated hydrocarbons and solids can be individually treated by land farming or other known waste treatment materials. At the present, however, there are regulations which prevent or severely restrict the use of land farming as a means of disposing of industrial sludges.
One of the problems associated with sludge addition to a cooking zone is temperature reduction which accompanies the addition of a relatively cool sludge to the zone. Temperature reduction contributes to increased coke yields which most refiners try to avoid since the liquid products from a typical refinery coker are more valuable than the solid coke produced.
One way to overcome temperature reduction attendant with sludge addition is to oxidize the sludge by contacting it with oxygen at conditions which will effect oxidation of certain components of the sludge, liberating heat as a result of heat of oxidation. If the oxidation conditions are suitably regulated, hydrocarbons contained in the sludge can be combusted to contributed substantial heat to the coking process. An additional advantage is that the sludge can be maintained at a higher temperature in the coking process which helps thermally convert hydrocarbons in the sludge and any toxic materials which may be present.
When oxygen addition to the sludge is coupled with oxygen addition to the feed, or liquid or vapor derived from the feed, the coking process can function at a higher overall temperature, thus increasing the production of valuable liquids and vapors from the coker feed while reducing the yield of solid coke.
In operating a coking process, the refiner generally aims to minimize coke production and maximize liquid products, since the liquid is more easily converted into gasoline or other materials having higher values than the solid coke material.
Higher temperatures in the coking zone reduce the solid coke yield and increase the more valuable liquid product yield; however, higher coking temperatures require increased feed furnace temperatures which may cause rapid coking in the furnace tubes and shortened on-stream time for the process. Lower temperatures produce soft coke, higher coke yield, and lower liquid yield, but permit longer on-stream time for the process.
The coke formation reactions are essentially endothermic with the temperature dropping in the coke zone. In an effort to maintain highest possible temperatures in the coke zone, the feed is preheated to a maximum temperature consistent with heater tube life. Adding sludge to the coking zone adds to the problem of maintaining high reaction temperatures in the coking zone since the sludge must be heated. Also by coking of the sludge added to the coker reduces coker temperature because of the endothermic nature of the coking reaction.
The process of this invention improves the ability of the coker operator to maintain reaction temperatures by contacting the sludge added to the coker during the coke production cycle with a gaseous stream comprising oxygen at conditions to effect oxidation of a portion of the sludge. This adds heat to the system and is done in connection with oxygen addition to the feed, liquid derived from the feed, or vapor derived from the feed to cause combustion of a portion of the feed.
Addition of the sludge and oxygen mixture to the coking zone may take place at any convenient location in the coke drum. The preferred locations, however, are in the feed or in the vapor section of the coke drum. In the latter case, sludge and oxygen mixture is generally added as a separate stream at oxidation conditions to effect contact of the sludge with the vapor products within the coke drum, oxidation of a portion of the sludge, and vaporization of at least a portion of the sludge.
By adding oxygen to the sludge and passing the mixture to the coking zone at conditions including a temperature sufficiently high to cause combustion of at least a portion of the organics in the sludge, a sufficiently high temperature results. This helps convert any combustible toxic materials in the sludge to harmless products. Additionally, some or all of the hydrocarbons in the sludge can be converted to more valuable liquid or vapor products with some production of coke. This also eliminates the need for land farms or other waste disposal methods which can add considerable expense to refinery operations.
To maximize coking zone temperatures, various methods have been used to increase the coker feed temperatures while reducing or minimizing any adverse effects accompanying these higher temperatures. Adding hot coke particles to the delayed coker feed has been disclosed. Adding oxygen-containing solids to the feed to increase temperature through oxidation of the feed passed into the coking zone is known. Additional methods for increasing coking zone temperatures include combustion of part of the feed or coke produced in the coker in a separate combustor which is heat exchanged with the coker feed.
U.S. Pat. No. 2,412,879 discloses a process in which a cellulosic material such as sawdust is added to delayed coker feed to reduce the amount of solid coke produced from the feedstock and to produce an easily-crushable and porous solid coke material. The cellulosic material is converted at least partially to charcoal.
U.S. Pat. No. 4,096,097 similarly teaches a process of producing high quality coke in a delayed coking process by adding an effective amount of an oxygen-containing carbonaceous material to the feed which decomposes at the high temperatures of the feed passing into the delayed coking drum. As disclosed in this patent, the oxygen content of the carbonaceous additive should be within the range from about 5 to 50 weight percent and usually no higher than 60 weight percent of the oxygen-containing material added to the feed. The carbonaceous materials which are taught to be effective include coal, lignite, and other materials such as sugar beet waste, sawdust, and other cellulosic wastes.
U.S. Pat. No. 4,302,324 also relates to an improved delayed coking process in which hot coke particles are added to the heated coker feedstock to raise its temperature by at least 50.degree. F. The coke produced in this process is lower in volatiles and has improved mechanical strength, and the yield of liquid product is increased.
Another process involves coking hydrocarbon oils by contacting a feed with free oxygen in the presence of an aqueous liquid to product high quality coke and increase yields of liquid products from the coking reaction. This process is exemplified in U.S. Pat. Nos. 4,370,223 and 4,428,828. Sometimes the entire heat requirements for the process can be provided by the oxidation of the heavy hydrocarbon feed in the aqueous system with free oxygen.
Another process in which oxygen reacts with a residual feed is asphalt blowing. This process is exemplified in U.S. Pat. No. 3,960,704 in which isotropic petroleum coke is produced from a residual feedstock by blowing the feedstock with air until it has a desired softening temperature and subjecting the blown residuum to a delayed coking process.
The fluid bed coking art is replete with patents in which air or oxygen is added to a fluidized coking process to enhance fluid coke properties and decrease the need for external heat addition to the process. In particular, U.S. Pat. Nos. 2,537,153, 3,264,210, 3,347,781, 3,443,908, and 3,522,170 discuss various methods for using oxygen either directly injected into a fluid bed of coke or combusting a part of the fluid coke with the oxygen to supply additional heat to the bed process.
U.S. Pat. No. 2,347,805 (U.S. Class 190/65) is generally concerned with converting heavy oils to more valuable products and discloses the addition of oxygen or air to the feed passing into a coking still at conditions which inhibit formation of CO, CO.sub.2 and other oxygenated bodies to assist in the upgrading of the feed to lighter products and coke.
U.S. Pat. No. 4,534,851 (U.S. Class 208/131) relates to the use of a plurality of injection nozzles to effect introduction of steam into transfer line reaction zones so as to reduce coking on the walls of the transfer lines.
U.S. Pat. No. 3,702,816 (U.S. Class 208/50) relates to a process for reducing sulfur content of coke obtained from high sulfur resids by hydrogenation of the residual feedstock followed by contacting the partially desulfurized residual feedstock in a liquid phase with an oxidizing agent and thereafter passing oxidized charged stock free of extraneous oxidizing agent to a coking zone.
U.S. Pat. No. 4,332,671 (U.S. Class 208/92) relates to a coking process in which the coke is treated by a high temperature calcination with oxygen to reduce its sulfur content.
U.S. Pat. No. 4,051,014 (U.S. Class 208/88) relates to a process for producing coke from sulfur-containing residual feedstocks which involves contacting the feedstock with a peroxy oxidant in the presence of a metal-containing catalyst to oxidize a portion of the hydrocarbon feedstock and subjecting the feedstock to coking conditions to form coke and recover coke product.
In coking processes, sludges have been disposed of in various manners.
In U.S. Pat. No. 4,552,649 (U.S. Class 208/127), an improved fluid coking process is described where an aqueous sludge which comprises organic waste material is added to a quench elutriator to cool the coke in the elutriator and convert at least a portion of the organic waste to vaporous compounds which can be recycled to the fluid coking heating zone to increase the temperature of the fluid coke particles therein.
In U.S. Pat. No. 3,917,564 (U.S. Class 208/131), sludges or other organic by-products are added to a delayed coking drum during a water quenching step after feed to the coke drum has been stopped and the coke drum has been steamed to remove hydrocarbon vapors. The quenching step cools the hot coke within the coke drum to a temperature that allows the coke to be safely removed from the coking drum when it is opened to the atmosphere.
The sludge is added along with the quench water and contacts the solid coke in the coke drum at conditions causing the vaporization of the water contained in the sludge. The organic and solid component of the sludge is left behind through deposition on the coke and removed from the coke drum as part of the solid coke product.
U.S. Pat. No. 4,666,585 (U.S. Class 208/131) relates to the disposal of sludge in a delayed coking process by adding sludge to the coker feedstock and subjecting the feedstock and sludge mixture to delayed coking conditions.
U.S. Pat. No. 2,043,646 (U.S. Class 202/16) discloses a process for the conversion of acid sludge into sulfur dioxide, hydrocarbons and coke in a two-step procedure comprising passing sludge into a kiln to produce semi-coke and then passing the semi-coke into a coke drum for conversion into coke product.
U.S. Pat. No. 4,874,505, Bartilucci et al. relates to a sludge addition to a delayed coking process in which the sludge is segregated into high oil content sludge and high water content sludge. These sludges are introduced into the delayed coking unit during different operating cycles of the coker.
West German Offenlegungsschrift, DE 3726206 A1, relates to a coking process in which sludge is added to the process at different locations in the coke drum.
U.S. Pat. No. 3,917,564 (U.S. Class 208/131) discloses a process in which sludges or other organic by-products are added to a delayed coking drum during a water quenching step after the feed coke drum has been stopped and the coke drum has been steamed to remove hydrocarbon vapors. The quenching step cools hot coke with the coke drum through a temperature that allows coke to be safely removed from the coking drum when it is open to the atmosphere.
U.S. Pat. No. 1,973,913 (U.S. Class 202/37) discloses a process wherein coke which has been removed from a coking oven or drum is quenched with polluted wastewater which contains tar acids. After quenching, the tar acids can remain on the coke, and the aqueous materials associated with these acids is vaporized.
U.S. Pat. No. 2,093,588 (U.S. Class 196/61) discloses a process of delayed coking in which liquid materials such as hydrocarbons or water are passed into the vapor portion of the delayed coking zone.
U.S. Pat. No. 4,501,654 (U.S. Class 208/131) teaches injection of a residual feedstock into the top of a coking drum.
In U.S. Pat. No. 4,552,649 (U.S. Class 208/127) an improved fluid coking process is described where an aqueous sludge which comprises organic waste material is added to a quench elutriator to cool the coke in the elutriator and convert at least a portion of the organic waste to vapor compounds which can be recycled to the fluid coking heating zone to increase the temperature of the fluid particles in that zone.
In U.S. Pat. No. 1,973,913 (U.S. Class 202/37), coke which has been removed from a coking oven or coking drum is quenched with polluted wastewater which contains tar acids. After quenching, the tar acids remain on the coke and the aqueous materials associated with these acids is vaporized.
U.S. Pat. No. 4,404,092 (U.S. Class 208/131) discloses a process for increasing the liquid yield of a delayed coking process by controlling the temperature of the vapor space above the mass of coke in the coke drum by injecting a quenching liquid, instead of sludge, into the vapor phase within the delayed coking drum. The patent teaches that large amounts of liquid should be added to the vapor space within a delayed coking drum (about 9 percent by weight of the feed).
The invention disclosed herein can be summarized as a coking process in which oxygen is added to a sludge stream which contacts feed, or liquid or vapor derived from the feed, and in which the feed, or liquid or vapor derived from the feed also contacts oxygen to effect oxidation of a portion of the feed, or vapor or liquid derived from the feed.
It is an object of the present invention to provide an improved coking process in which the operating temperature in the coking zone can be increased without reducing the operating factor for the coker feed furnace. It is another object of a present invention to provide increased liquid yields and decreased solid coke yields by maintaining high operating temperatures in the coking zone.
It is another object of this invention to dispose of sludge materials which may contain environmentally harmful materials by contacting a mixture of oxygen and sludge at high temperatures in a coking zone to convert the sludge to valuable and non-harmful materials.
The present invention of adding oxygen to the sludge for eventual oxidation of a portion of the sludge and adding oxygen to feed or converted liquids or vapors in a delayed coking zone overcomes one of the main problems associated with current commercially operated delayed coking processes. Even though delayed coker drums are well insulated, the coke drum vapor outlet temperature is usually 60.degree. to 120.degree. F. lower than the temperature in the transfer line connecting the coke drum and the feed furnace, since the coking reactions occurring in the coke drum are endothermic. Higher transfer line temperatures increased the profitability of the delayed coker operation by reducing the solid coke yield. Additionally, to produce an acceptable grade anode coke from residual feedstocks, higher transfer line temperatures are also required to meet anode coke density specifications.
The common practice in the industry to increase the transfer line temperatures is to increase feed furnace temperature. However, the higher furnace tube temperature which result are also accompanied by increased furnace tube fouling rates and the need for frequent decoking of the tubes.
It is, therefore, desirable to increase the coke drum temperature without raising the furnace temperatures. Accordingly, one aspect of the invention claimed herein meets a commercial need by increasing the transfer line temperature by adding oxygen to the transfer line causing oxidation of a portion of the feed passing through the transfer line. The oxidation reaction is exothermic and raises the temperature in the transfer line without increasing the feed furnace temperature which would be accompanied by increased furnace fouling rates. Oxygen can also be added to liquid or vapor derived from the feed or to the coke produced in the process.
Another aspect of the invention helps maintain coker operating temperatures by adding oxygen to sludge which is injected into the coker to contact feed or converted liquid or vapor or, in some cases, solid coke. The oxygen in the sludge causes a portion of the sludge to be oxidized in the coke drum, increasing its temperature and adding heat to the coker process.
Injection of the mixture of oxygen and sludge into the coking process, whether it be a delayed-coking coke drum or a fluid bed coker, allows the sludge to contact vapor or solid coke materials in the coke drum at high process temperatures which can enhance the conversion of hydrocarbons in the sludge to coke, liquid or vapor. In most cases, the toxic materials in the sludge can be converted to more environmentally acceptable materials at the high temperatures which are prevalent in a delayed coking drum as a result of oxygen addition to the sludge. Also, contacting an additional oxygen stream with feed, or vapor or liquid derived from the feed, adds more heat to the coking zone to help maintain high temperatures in the coking zone by oxidizing or combusting hydrocarbon materials in these materials.
US Referenced Citations (7)
Continuation in Parts (2)
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Number |
Date |
Country |
| Parent |
285110 |
Dec 1988 |
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| Parent |
937990 |
Dec 1986 |
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Patent Grant
5110449
