US 3446609 A
Description (OCR text may contain errors)
May 27, 1969 E. F. REiN N IUTH ET AL GASIFICATION WITH WATER-CONTAINING FEED Filed May 13, 1965 HYoRobARBoN STORAGE ,REACTOR N I I I 3235? V WATER l V 3 I .L w w I- "'IVIS INVENTORS'.
LEONARD W. TER HA AR- ERNST F. REINMUTH ,mwzm
THEIR ATTORNEY United States Patent U.S. Cl. 48-215 4 Claims ABSTRACT OF THE DISCLOSURE In a process for production of H and CO containing gas mixtures by partial combustion of hydrocarbons, soot formation is suppressed by injecting small amounts (preferably 0.1-4.0% w.) of liquid water into the feed. Explosive evaporation of the liquid water into the partial oxidation burner improves atomization of the feed and has an advantageous cooling effect resulting in reduced soot formation.
This invention relates to a process for preparing gas mixtures containing hydrogen and carbon monoxide. In particular, it relates to gasification of liquid hydrocarbon feeds containing small amounts of Water.
The gasification of hydrocarbons by partial oxidation to produce H -CO mixtures is a Well-known commercial process. This process generally involves intimately mixing hydrocarbon and an oxidant, such as air, in a combustion chamber in carefully controlled proportions. The mixed gases enter a reaction zone, wherein the conversion of hydrocarbon feed to hydrogen, CO, and minor amounts of carbon, is completed. After subsequent processing which may include heat recovery, carbon removal, and water scrubbing of the gas, the carbon-free product may be used as synthesis gas or fuel gas for any of a variety of purposes. Examples of these processes are found in Oil and Gas Journal, vol. 63, No. 14, pp. 108-9 (Apr. 5, 1965).
Accordingly, it is known to obtain hydrogen-carbon monoxide mixtures by partial oxidation of hydrocarbons. Steam may also be supplied with the reactants as a moderator. As mentioned above, gas mixtures obtained by hydrocarbon gasification always contain some free carbon, hereafter referred to as soot. Although the amount of soot produced can be maintained at relatively low levels by operation under certain conditions and by using special equipment (as described in e.g. Te Nuyl, U.S. 2,904,417, issued Sept. 15, 1959), subsequent treatment of the gases for soot removal is necessary even if only very small amounts of soot are formed. It is known to recover this soot by water-quenching and washing the gases, and by aggregating soot particles to pellets by treatment of the resulting aqueous soot slurry with small amounts of oil, or by recovering the soot as a soot-in-oil suspension. Although such a soot-in-oil slurry is useful as a fuel, it usually cannot be completely consumed at or near the gasification unit and transport to other areas is costly.
According to the invention, soot formation, is reduced by feeding a fuel comprising a liquid hydrocarbon and a minor amount of water to the gasification process. Water is supplied to the liquid hydrocarbon feed in small amounts sufficient to reduce soot formation; appropriate amounts of water are less than 4%, preferably 0.1 to 4%, and more especially 0.3 to 0.7% by weight of the total fuel intake.
The advantages obtained from the presence of small amounts of water in the liquid fuel are believed to derive at least in part from an explosive evaporation of water that takes place at the burner or atomizer as a result of the large temperature increase and pressure decrease in the reactor. As improved atomization of the hydrocarbon is obtained, soot formation is reduced. In practice of the invention, it has been found that soot suppression of up to about 20% by weight can be obtained as compared with a similar process operating with a water-free feed. In addition to reducing soot formation, the presence of a small amount of water in the feed has a cooling effect on the flame because of the vaporization of the water. Since one of the limitations on oxygen dosage is the heat load on the reactor brick lining, water injection allows increased oxygen dosages which result in a still further reduction of soot formation.
Any liquid hydrocarbon or hydrocarbon mixture may be used as gasification fuel, ranging from lower parafiins and naphthas to residual oils. Even normally gaseous hydrocarbons, such as propane, could be used if they were supplied to the reactor in the liquid phase, which is the essential requirement of reactor feed for practice of the invention. Water may be injected into the fuel prior to atomization to pressurize the fuel up to feed pressure, which may be from about 60 to about 160 atmospheres. Alternatively, water may be injected into the hydrocarbon prior to preheat of the feed. Feed preheat may be anywhere from about to about 350 0, however, it is essential that the feed remain in the liquid phase until vaporization in the atomizer. Part of the explosive evaporization of the feed is caused by the decrease in pressure on atomization; feed pressures may be from 60 to atmospheres, and the reactor pressure is less than 40 atmospheres. When air is used as an oxidant, reactor pressures are from about 1 to about 6 atmospheres; when oxygen is used as an oxidant, higher pressures of 3 to about 40 atmospheres are more suitable.
In commercial tests of water addition to liquid gasification feeds, very satisfactory operating results were obtained. While normally as the hydrocarbon feed/oxygen ratio is increased, free carbon formation also increases, with water injection an unexpected increase in equipment capacity was obtained and so formation was suppressed even at higher hydrocarbon/ oxygen ratios.
Gasification reaction conditions are generally temperatures of 1000-1600 0., preferably 1100-1500 C., and pressures of 1-40 atmospheres. Both hydrocarbon and oxygen feed are advantageously preheated to temperatures not exceeding 350 C. in the practice of the invention. Oxygen is supplied in amounts suflicient to completely react to form the desired products; oxygen/hydrocarbon ratios will vary depending on desired products, hydrocarbon mol weight, etc. A moderator such as steam or CO may also be supplied to the reactor. Depending on the type of hydrocarbon used as feed, oxygen content of the oxidant, oxygen/fuel ratio, and equipment design, free carbon liberated may be from about 0.1 to about 5% w. basis hydrocarbon feed.
Gasification of liquid feeds always contain soot, which, as discussed above, must be removed from the gases by some treatment. The most effective treatment has been found to be a water wash or quench wherein the soot is recovered as an aqueous slurry. This slurry cannot be disposed of as waste because of pollution problems. For most eflicient use of the carbon, the slurry may be concentrated and the carbon either pelletized or recovered as a soot-in-oil slurry by preferential wetting of the soot with e.g. a light hydrocarbon oil which is easily separated from the aqueous phase. The resulting soot agglomerates contain about 10 to 15% w. water, and thus in an alternate aspect of the invention can be used as a source of water for atomization of the liquid feed. Accordingly, soot-containing oil may be mixed with liquid hydrocarbon feed such that the resulting mixture contains a certain 3 critical amount of water (i.e. less than 4%, preferably 0.3 to 0.7% by weight).
The invention is illustrated in the accompanying drawing which depicts a flow scheme which is part of the gasification unit operated according to the invention. Referring to the drawing, vessel 1 represents a storage tank for liquid hydrocarbon from which the liquid fuel is pumped by pump 3 through a line 2. Pump 3 is a lowpressure pump which pressurizes the liquid fuel after passing the pump to not more than about 6 atmospheres. Water is supplied to line 4 and pump 5 which is driven by a driving means 6 which may include also a dosing mechanism to line 7. At the junction of lines 7 and 2, water is injected into the fuel stream. No special mixing device is required; intimate mixing of the water with the fuel stream to the required extent takes place in the common line 8 and high-pressure pump 9 and line 11. Pump 9 pressurizes the mixture up to 60-160 atmospheres.
The mixture is preheated before entering the reactor, preferably at a point not far from the reactor, in heat exchanger 12. After preheat, the mixture is introduced through a pressure atomizer 13 into reactor 14, wherein the degree of atomization is very fine due to the circumstance that a small amount of water is present in the fuel stream. The reactor is an open vertical chamber, unobstructed by packing and the like. The water protects the brick lining of the reactor at the hottest place. As a result of its cooling effect on evaporation. Soot-containing gases produced in the reactor are drawn off through line 15 for further processing. Suitable control means 16 operating the dosing device '6 and receiving its signal from a fiowmeter present in line 2 is schematically indicated in the drawing by dotted lines 17 and 18 respectively. Auxiliary equipment, such as inlet and outlet lines, valves, other control means, etc. have been omitted.
We claim as our invention:
1. In a process for partial oxidation of a liquid hydrocarbon fecd wherein hydrocarbon is fed in the liquid phase to a reaction zone and is contacted therein with an oxygencontaining gas at elevated temperatures to produce a gaseous mixture comprising carbon monoxide and hydrogen containing small amounts of free carbon, the improvement which comprises adding liquid water to the liquid hydrocarbon feed in an amount of from 0.01 to 4% by weight of the hydrocarbon feed.
2. The process improvement of claim 1 wherein liquid water is added in an amount of from about 0.3 to 0.7% by weight of the total hydrocarbon feed.
3. A process for partial oxidation of a liquid hydrocarbon feed wherein hydrocarbon and water is fed in the liquid phase to a reaction zone andis contacted therein with an oxygen-containing gas at elevated temperatures to produce a gaseous mixture comprising carbon monoxide and hydrogen and small amounts of free carbon, recovering free carbon from the gaseous mixture by contacting the gaseous mixture with water to form an aqueous slurry of carbon particles, contacting the aqueous slurry with liquid hydrocarbon to form a slurry of carbon in hydrocarbon, and blending at least a portion of the carbon-hydrocarbon slurry with hydrocarbon feed, the liquid water content being from 0.01 to 4% by weight of the resulting reactor feed.
4. The process of claim 3 wherein the resulting reactor feed contains from 0.3 to 0.7% w. water.
References Cited UNITED STATES PATENTS 1,644,146 10/1927 Pike 48214 2,665,980 l/1954 Carkeek.
2,999,741 9/1961 Dille et al. 48215 XR 3,097,082 7/1963 Guptill 48215 3,147,093 9/1964 Dille et al. 48215 3,232,727 2/1966 Guptill et a1. 48215 MORRIS o. WOLK, Primary Examiner.
R. E. SERWIN, Assistant Examiner.
U.S. c1. X.R.