US2662006A - Gas manufacture - Google Patents

Description

Dec. 8, 1953 HTM afl/,4702? PES/DUHL E s. c. EAsfrwooD 2,662,006

GAS MANUFACTURE Filed Jan. 16, 1953 INVENTOR.

3 excess carbon from the HTM, according to the following reactions:

A mixture of steam and air can be introduced via line lo in place of steam alone, with the air serving to prevent too much cooling and stoppage of the water gas reaction by vburning a portion of the excess coke. the water gas reaction zone is kept between about 1200o F. and about 2500 F., and preferably 1600-2000 F.,'with a contact time of -about 0.5 to 60 seconds. Cracked products and the prod# ucts, CO and H2, of the water gas reaction are withdrawn from the reactor through line i2.

Above the water gas zone, and above line ID and inverted angles Il, is a seal zone which is maintained at essentially the saine temperature as that of the water gas zone, but which is under a pressure slightly greater than the water gas The temperature ofy zone to prevent a large portion of the steam from flowing upwardly through the reactor.

Above the seal zone is a combustion zone where.. in carbon or coke is burned off the HTM. Air is introduced into the latter zone through line i3 and is distributed across the downwardly moving HTM by inverted angles lli. The temperature within the combustion zone is maintained above about 1200 F., preferably 160Q-2000" F., such that a portion of the carbon or coke on the HTM is converted to carbon oxides. The latter are fe-- moved as a flue gas through line ia at an upper section of the reactor. A back pressure can be applied to line l5 in order to provide the necessary pressure in the aforementioned seal zone. If desired, the seal can be provided by permitting' a small portion of the steam (or steam and air) to travel upwardly from the water gas zone through the seal zone to the combustion zone. As coke is burned off the HTM in the combustion zone, the temperature of the HTM is raised to the temperatures desired in the following seal and water gas zones.

It is to be understood that only a portion of the carbon deposited upon the HTM, in its course through the cracking zone, is removed in the combustion zone. Conditions are adjusted to give a partial removal rather than a complete removal since the additional heat is not needed in the process. Then, in the water gas zone the remaining or excess coke stemming from the residual fuel, is converted in the water gas reaction. This two-stage removal of coke is much more emcacious than a one-stage removal by combustion, in that a better heat balance can be maintained in the process and a better conversion eiciency heat combustion gas product (1' e" heat combustion liquid feed can be obtained.

This invention, as described above, has many advantageous features. For example, removal of flue gas as a separate stream is desirable, particularly if the separation of hydrocarbons from carbon monoxide and hydrogen is desired in subsequent operations. This makes possible reduction in the size and :complexity of' a product recovery system.

Separation of products' and reactants within an individual reaction zone is desirable, because it prevents these materials from entering another reaction zone wherein they couldalter the chemical equilibria established in the latter zone to obtain the desired reactions. This permits closer control of operating variables, such as temperature, pressure and reaction time and results in a more favorable product distribution.

In addition, this invention makes possible a heat balanced unit wherein the heat of combustion of carbon on the HTM is utilized in the water gas reaction. The need for Waste heat boilers or any such economizers is eliminated, since direct heat exchange between cold HTM and product gases in the top of the reactor results in substantially complete heat recovery. Also, since quenching of product gas takes place in the reactor, no extraneous quencher is required.

The granular heat transfer material in the process of this invention should be a solid material having a relatively low or substantially no catalytic cracking activity, a high heat absorption capacity and it should be capable of withh standing high temperatures of the order of 20002500 F. Without severe breakage, cracking or attrition. The material can he non-porous, for example, metallic pieces or balls. Preferably, however, the solid material should be porous, for example, natural clays which havev become deactivated so as to have a very low activity as a cracking catalyst, Other materials which can be employed are pumice, mullite, fused alumina, silica, etc. A preferred heat carrying material is granular petroleum coke. The granular material can range in size from about mesh Tyler up to about one inch in diameter, preferably of the order of one-eighth to one-quarter inch in diameter. The term granular is employed herein in a broad sense as including solids in various shapes and forms such as pellets, tablets, spheres, and irreguiar shaped particles.

It is to be understood, however, that although heat transfer materials of little or no catalytic cracking activity are preferred herein, as indicated above, it is also contemplated that catalytically active materials can be used. For eX- ample, metallic catalyst compositions, such as nickel, iron, copper and others which promote the desired reactions and yet which retain stability at high temperatures, can be used.

Although the invention is illustrated above by the conversion of a residual fuel of the character shown above, it is to be understood that any hydrocarbon fraction from and including ethane to and including residual fuels can be used herein. As a note of caution, it will be recognized by those skilled in the art that higher temperatures and longer contact times are to be used in converting the lower molecular weight materials, such as ethane, than in similarly converting a residual liquid fuel. Particularly advantageous hydrocarbon charges for the process described and claimed herein, are residual type liquid fuels, and with such charges it is preferred that the following reaction conditions be maintained:

As indicated above, steam or a mixture of steam and air can be charged to the water gas zone. It is to be understood, however, that Oxy;

gen can be used in place of air, although the latter is preferred in View of its much lower cost. Similarly, oxygen can be used in place of air in the combustion zone, but air is to be preferred. The dilution effect of nitrogen upon the prime product gases, carbon monoxide, hydrogen and gaseous cracked hydrocarbons, is small and the total product gases have a satisfactorily high heating value for use directly in industrialor utility plants, or can be blended with other gases before put to such use.

I claim:

1. The process which comprises: passing a hot granular solid downwardly in series through a reactor comprising successively a combustion zone, a seal zone, a water gas reaction zone, and a cracking zone; passing a hydrocarbon in direct contact with said solid in said cracking zone under cracking conditions, whereby said oil is cracked to coke and to gaseous products which ow upwardly through said reactor countercurrent to said solid; passing steam in direct contact with said solid in said water gas reaction zone such that said steam iiows downwardly therein with said solid, at a temperature between about 1200 F. and about 2500 F. and for a contact time between about 0.5 seconds and one minute, whereby said steam and a portion of the coke deposited on said solid react to form a product predominantly comprised of carbon monoxide and hydrogen, and removing said product from an intermediate section of said reactor between said water gas zone and said cracking zone; maintaining a seal zone above said water gas zone at a temperature substantially the same as that maintained in said water gas zone; passing air into said combustion zone under conditions appropriate for converting a portion of the coke deposited on said solid in said cracking zone, to flue gas and removing said flue gas from an upper section of the reactor above the combustion zone.

2. The process defined by claim 1, wherein the hydrocarbon charge is a residual oil boiling above about 800 F.

3. vThe process denedjby claim 1, wherein a mixture of steam and air is passed into said water gas zone.

4. The process dened by claim 1, wherein said cracking conditions comprise a temperature between about 1200 F. and about 1700 F. and a contact time between about 0.1 and about 10 seconds.

5. The process defined by claim 1, wherein the temperature of said Water gas zone is maintained between about 1600 F. and about 2000 F.

SYLVANDER C. EASTWOOD.

No references cited.

Claims (1)

1. THE PROCESS WHICH COMPRISES: PASSING A HOT GRANULAR SOLID DOWNWARDLY IN SERIES THROUGH A REACTOR COMPRISING SUCCESSIVELY A COMBUTION ZONE, A SEAL ZONE, A WATER GAS REACTION ZONE, AND A CRACKING ZONE; PASSING A HYDROCARBON IN DIRECT CONTACT WITH SAID SOLID IN SAID CRACKING ZONE UNDER CRACKING CONDITIONS, WHEREBY SAID OIL IS CRACKED TO COKE AND TO GASEOUS PRODUCTS WHICH FLOW UPWARDLY THROUGH SAID REACTOR COUNTERCURRENT TO SAID SOLID; PASSING STEAM IN DIRECT CONTACT WITH SAID SOLID IN SAID WATER GAS REACTION ZONE SUCH THAT SAID STEAM FLOWS DOWNWARDLY THEREIN WITH SAID SOLID, AT A TEMPERATURE BETWEEN ABOUT 1200* F. AND ABOUT 2500* F. AND FOR A CONTACT TIME BETWEEN ABOUT 0.5 SECONDS AND ONE MINUTE, WHEREBY SAID STEAM AND A PORTION OF THE COKE DEPOSITED ON SAID SOLID REACT TO FORM A PRODUCT PREDOMINANTLY COMPRISED OF CARBON MONOXIDE AND HYDROGEN, AND REMOVING SAID PRODUCT FROM AN INTERMEDIATE SECTION OF SAID REACTOR BETWEEN SAID WATER GAS ZONE AND SAID CRACKING ZONE; MAINTAINING A SEAL ZONE ABOVE SAID WATER GAS ZONE AT A TEMPERATURE SUBSTANTIALLY THE SAME AS

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