US3752658A - Integrated fluid coking-gasification process - Google Patents

Abstract

LOCATED IN THE UPPER PORTION OF THE SINGLE VESSEL REACTOR TO PRODUCE FUEL GAS.

A PROCESS FOR PRODUCING FUEL GAS WHEREBY COKE FROM A CONVENTIONAL FLUID COKER IS REACTED WITH AN OXYGENCONTAINING GAS IN A LOW TEMPERATURE ZONE LOCATED IN THE LOWER PORTION OF A SINGLE VESSEL REACTOR TO PRODUCE FLUE GAS, AND THEN REACTING THE FLUE GAS ALONG WITH STEAM AND AIR OR OXYGEN WITH COKE WHICH HAS BEEN TRANSFERRED FROM THE LOW TEMPERATURE ZONE TO A HIGH TEMPERATURE ZONE

Description

D. E. BLAETR Aug. 14, 1973 INTEGRATED FLUID COKING-GASIFICATION PROCESS Filed Jan, 6, 1971 INVENTOR. D E BLASER mm mm mfl WWWMWMW ATTORNEY United States Patent ()1 hoe 3,752,658 Patented Aug. 14, 1973 3,752,658 INTEGRATED FLUID COKING-GASIFICATION PRDCESS Don E. Blaser, Dover, N.J., assignor to Esso Research and Engineering Company Filed Jan. 6, 1971, Ser. No. 104,281 Int. Cl. C10g 9/28; C10j 3/00, 3/20 US. Cl. 48-206 6 Claims ABSTRACT OF THE DISCLOSURE A process for producing fuel gas whereby coke from a conventional fluid coker is reacted with an oxygencontaining gas in a low temperature zone located in the lower portion of a single vessel reactor to produce flue gas, and then reacting the flue gas along with steam and air or oxygen with coke which has been transferred from the low temperature zone to a high temperature zone located in the upper portion of the single vessel reactor to produce fuel gas.

BACKGROUND OF THE INVENTION This invention relates to producing fuel gas from coke by a novel gasifying process. More particularly, the gasifying process consists of a two stage process wherein coke is injected into a low temperature zone where it reacts with air or oxygen to produce flue gas, and said flue gas along with additional air or oxygen and steam is contacted in a high temperature zone with hot coke transferred from the low temperature zone to the high temperature zone to produce fuel gas; i.e., hydrogen and carbon monoxide.

In another embodiment this invention relates to an integrated fluid coking-gasification process. More particularly it relates to a process wherein a heavy hydrocarbon material is coked in a conventional fluid coker and the coke produced is injected into a two stage gasification reactor to produce fuel gas.

In a conventional fluid coking process a heavy hydrocarbon fraction such as vacuum residuum is fed into a fluid coking reactor to produce both a liquid and gas petroleum distillate product and coke. The coke is then fed to a separate heater reactor to heat the coke to a temperature high enough to transfer back to the coking reactor to supply the heat requirements needed.

A fluid coking process such as above has encountered several problems. First, there is generally more coke produced in a coking reactor than is needed in the heater reactor. Since this coke has very little value as a byproduct, disposal of excess coke has become a problem. Another problem arises in the burning of the coke in the heater reactor. By-products of this reaction are S and COS, along with partially combusted hydrocarbon and ammonia, which are released in the air as pollutants. In light of the new federal and state air pollution laws this sulfur and hydrocarbon emission is not acceptable.

In order to alleviate these and other problems created by a conventional fluid coking process, the petroleum industry has proposed addition of a third reactor to the other two fluid coking process reactors to convert the excess coke into fuel gas by reaction with steam. While this eased the coke disposal problem it did little to correct the unacceptable sulfur and hydrocarbon emission in the air from the heater reactor. The addition of an additional gasifier reactor also has the disadvantage that it, along with the necessary transfer lines, adds enormously to the cost of a coking process.

In a desire to overcome the disadvantages of adding a separate gasification reactor, a novel two stage, single vessel, heater-gasifier reactor was designed as described in pending application Ser. No. 880,219 entitled Improved Fluid Coking Process Incorporating Gasification of Product Coke, filed on Nov. 26, 1969, now US. Pat. 3,661,543, issued May 9, 1972. In this process design the coke produced in a conventional fluid coking reactor was injected into a high temperature gasifying zone (1800 F.) located in the lower portion of a second heater-gasifier reactor. Here the coke was contacted with steam to produce fuel gas. This hot fuel gas (-1800 F.) passed through a gas distributor apparatus and into a low temperature heating zone (-1100 F.) located in the upper portion of the second reactor. Here the hot gases were to both fluidize the heating zone coke bed and to heat this bed to the desired temperature. This design has however created new problems which this invention now overcomes. In the design of the above pending application there exists the possibility that the heating zone bed which is located above the gasifying zone bed in the heatergasifier reactor would dump into the gasifying zone bed if any of the slide valves stuck or the gas distributor grate separating the two beds was burned through. In such a situation the two stage reactor would have to shut down, and there would be the possibility of oxygen breaking through the beds and causing an explosion. A second disadvantage was the unreliability of the gas distributor to evenly distribute such hot gases in the upper heating zone bed. This results in poor fluidization of the upper bed which in turn creates hot spots within the bed, particularly around the gas distributor leading to the dumping problem described above. A further problem is the fouling of the heater overhead system by hydrocarbons distilled olf the coke in the heating zone bed. It is also possible that the gasifier products may revert to equilibrium in the heating zone resulting in the formation of soot and other undesirable sulfur compounds. A still further disadvantage is that the design of Ser. No. 880,219 cannot be attached to existing fluid coker reactors.

It is therefore an object of this invention to provide a process that economically utilizes the excess coke produced in a conventional fluid coking process, while at the same time eliminates the sulfur and hydrocarbon emission into the air which is associated with the conventional fluid coking process.

Another object of this invention is to provide a novel single vessel coke gasification process for producing fuel gas wherein the heating zone bed cannot dump into the gasifying zone bed.

A still further object of this invention is to provide a single vessel coke gasification process for producing fuel gas wherein hydrocarbons distilled off the coke in the heater bed cannot foul the gas removal system located at the top of the vessel.

It is also an object of this invention to provide a single vessel coke gasification process that can be readily adapted to existing fluid coker vessels.

In an alternate form it is an object of this invention to provide a novel integrated fluid coking-gasification process for converting heavy carbonaceous solids into liquid and gaseous petroleum distillate products and fuel gas.

Other objects and advantages of this invention will be obvious from the ensuing description of the invention.

SUMMARY OF THE INVENTION In one embodiment of this invention a carbonaceous material such as coke is gasified in a two zone single vessel reactor to produce fuel gas. More specifically coke from a conventional fluid coker is introduced into a low temperature zone situated in the lower portion of a single vessel gasifier reactor to produce flue gas and other hot gases by contact with air or oxygen, then contacting these gases along with steam and air or oxygen with coke in a high temperature zone to produce fuel gas.

In another embodiment of this invention a heavy hydrocarbon material such as vacuum residuum is converted into liquid and gaseous petroleum ditsillate products and fuel gas by an integrated fluid coking-gasification process. More specifically the vacuum residuum is fed into a conventional fluid coking reactor to produce a liquid or gaseous petroleum distillate product which is recovered from the reactor and coke which is transferred to a low temperature zone situated in the lower portion of a single vessel gasifier reactor to produce flue gas and other hot gases by contact with air or oxygen, then contacting these gases along the steam and air or oxygen with coke in a high temperature zone to produce fuel gas.

BRIEF DESCRIPTION OF THE DRAWING The figure schematically illustrates the preferred embodiments of the process of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT As seen in the figure a heavy hydrocarbon feed is introduced into a conventional fluid coking reactor 101 by means 102. This feed could include any carbon-containing material, but for economic and availability reasons vacuum or atmospheric distillation residuum (boiling point greater than about 1050 F.) is preferred. This residuum forms bed 103 which is maintained in a fluidized state by a fluidizing gas such as steam injected into bed 103 by means 104 and by the cracked hydrocarbon vapors produced in bed 103. This fluidized bed 103 is maintained at a temperature between 900 and 1100 F. in part by coke from the heating zone 111 of the single vessel gasifier reactor 110 introduced to the fluidized bed 103 by transfer line 105. If it is desired the feed could be preheated in a furnace or heat exchanger, not shown, before being injected into the fluid coking reactor 101.

Inside fluid coking reactor 101 the residuum is cracked to produce light liquid and gas distillate products which are removed from the reactor by cyclone means 106. A coke by-product is also produced by the reactors in bed 103 and is removed by transfer line 107 and transferred to the single vessel gasifier reactor 110 by a fluidizing gas such as steam introduced into transfer line 107 by line 108 and if needed by supplementary air or oxygen injected in transfer line 107 by line 109.

The coke is then injected into the heating zone 111 to form bed 112 in the lower portion of reactor 110. Bed 112 is maintained in a fluidized condition by air or oxygen from line 113. If desired small quantities of steam could also be added by line 114 to aid in maintaining the temperature of bed 112 between 1100 and 1500 F.

The temperature of bed 112 is increased principally by the exothermic reaction of carbon with oxygen:

C+O :CO 169,300 B.t.u.

and secondarily by the reaction C+%O =-CO+47,500 B.t.u.

Under the time and temperature conditions proposed, the CO/CO: ratio will be from 0.25 to 1 as set by kinetic and 1 equilibrium considerations. Therefore the more oxygen introduced in bed 112 the more heat that will be given off and absorbed in the bed, thus raising the bed temperature. Since it is not desirable to operate bed 112 above about 1500 F. the amount of oxygen that can be injected into the bed is limited.

For a typical residuum feedstock, the air to the lower bed 112 will be from 0.4 to 1.5 moles air/moles C/hour and, preferably 0.71 mole per mole of coke produced. If oxygen is fed to the lower bed 112 then a gas rate between 0.1 and 0.3 mole o /moles C/hour will be needed.

Total coke produced will be about 36% on residuum feed of which about 20% (7% on residuum feed) is consumed in bed 112.

The hot flue gas and other gases, such as H 8, S0 COS and other light hydrocarbons produced by reactions in bed 112 are passed through cyclone 116 to remove any fines or ash that may have risen with these gases. These fines and ashes are then returned to bed 112 by dipleg 117. The hot gases then pass through a gas distributor 118 into gasifier bed 115.

A portion of the hot coke in bed 112 is recycled to fluid coker reactor 101 by transfer line to maintain bed 103 at the proper temperatures. Another portion of the coke in bed 112 is transferred to gasifier bed by transfer line 120 to supply the necessary carbon needed in the gasifier bed reactions to produce hydrogen and carbon monoxide.

As stated above the hot flue gases (at temperatures between 1l00 and 1500 F., preferably between l100 and 1200 F.) along with other gases produced in heater bed 112 are distributed evenly throughout gasifier bed 115 by the gas distributor 118. Because these gases are at temperatures below 1500 F. gas distributors known in the art may be used satisfactorily to achieve excellent gas distribution. This means that the much hotter bed 115 can be maintained in a fluidized state without forming any hot spots which could have led to the destruction of the gas distributor 118. Thus under the process of this invention there is virtually no danger of the gasifier bed 115 dumping into the heater bed 112. Also contacted with the coke in gasifier bed 115 is additional steam and air or oxygen introduced by lines 121 and 122. respectfully, in order to aid in maintaining bed 115 in a fluidized state and to raise its temperature to between 1500 and 2200 F. If hydrogen and carbon monoxide are the desired products then the bed is preferably between 1700 and 1900 F., and most preferably about 1800 F.

When air is introduced by line 122 these temperatures can be achieved and bed 115 maintained in a fluidized state if the steam rate from line 121 together with any steam from bed 112 is between 0.1 and 0.4 moles H O/ moles C/hour and the air rate is introduced at a rate between 1.5 and 2.0 moles air/moles C/hour. At the preferred temperature range of 1700 to 1900 F., a steam rate between 0.25 and 0.35 H O/moles C/hour, along with an air rate between 1.7 and 1.9 moles air/ moles C/hour is preferred. For the most preferred temperature of 1800 F. a steam rate of about 0.3 moles H O/moles C/hour and air rate of about 1.8 moles air/ moles C/hour is preferred.

On the other hand if oxygen is introduced by line 122 a temperature between 1500 and 2200 F. can be maintained in bed 115 with a steam rate between 0.3 and 0.5 moles H O/moles C/hour and an oxygen rate between 0.2 and 0.4 moles O /moles C/hour, whereas the preferred temperature range is maintained with gas rates of between 0.35 and 0.41 moles H O/moles C/hour and 0.28 and 0.31 moles O /moles C/hour. At the most preferred temperature of 1800 F. gas rates of about 0.39 moles H O/moles C/hour and 0.3 moles O /moles C/ hour are preferred.

At these conditions the following reactions are predominant:

which results in a major portion of the gases exiting reactor 110 by cyclone means 123 being hydrogen and carbon monoxide.

The fines and ashes that may be swept up with the exiting gas are returned to heater bed 112 by dipleg 124. There will also be some H 8, S0 and COS in the exiting gas, but about 90% of these pollutants will now be in the form of H 8 rather than only about 70% which normally exit from a heating zone such as zone 112. This conversion to H S is highly desirable since H 8 is much easier, and thus cheaper, to separate and recover from the other exiting gases such as hydrogen and carbon monoxide.

Having described and illustrated the invention, what I claim as novel, useful and unobvious, and desire Letters Patent is:

1. A process for producing hydrogen and carbon monoxide from coke in a two-zone, single vessel reactor which comprises:

(a) introducing coke into a fluid heater bed operated at temperatures between 1100" and 1500 F. and positioned in the lower zone of said reactor;

(b) introducing an oxygen-containing gas into said fluid heater bed to maintain said fluid heater bed in a fluidized state and to react with said coke to produce hot carbon-containing gases;

(c) passing a portion of said coke from said fluid heater bed to a fluid gasifying bed operated at temperatures between 1500" and 2200 F. and positioned in the upper zone of said reactor;

(d) contacting said hot carbon-containing gas with the coke in said gasifying bed along with steam and an oxygen-containing gas which have been introduced into said gasifying bed to maintain said gasifying bed in a fluidized state and to produce hydrogen and carbon monoxide; and

(e) recovering said hydrogen and carbon monoxide from said reactor.

2. The process of claim 1, wherein the oxygen-containing gas introduced into said fluid heater bed is oxygen fed at a rate between 0.1 and 0.3 mole 0 mole C/hour.

3. The process of claim 1, wherein said oxygen-containing gas introduced into said :fluid heater bed is air fed at a rate between 0.4 and 1.5 moles air/mole C/hour.

4. The process of claim 1, wherein the oxygen-containing gas introduced into said gasifying bed is oxygen and wherein said oxygen is introduced at a rate between 0.2 and 0.4 mole O /rnole C/hour and said steam is introduced at a rate between 0.3 and 0.5 mole H O/mole C/hour.

5. The process of claim 1 wherein the oxygen-containing gas introduced into said gasifying bed is air and wherein said air is introduced at a rate between 1.5 and 2.0 moles air/rnol C/hour and said steam is introduced at a rate between 0.1 and 0.4 mole I-l O/mole C/hour.

6. The process of claim 1 wherein the gasifying bed is operated at a temperature between 1700 and 1900 F.

References Cited UNITED STATES PATENTS 3,661,543 5/1972 Saxton 48-206 2,588,075 3/1952 Barr et al. 48-206 2,591,595 4/1952 Ogorzaly 48-206 X JOSEPH SCOVRONEK, Primary Examiner US. Cl. X.R.

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