Classifications

• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10J—PRODUCTION OF PRODUCER GAS, WATER-GAS, SYNTHESIS GAS FROM SOLID CARBONACEOUS MATERIAL, OR MIXTURES CONTAINING THESE GASES; CARBURETTING AIR OR OTHER GASES
  • C10J3/00—Production of combustible gases containing carbon monoxide from solid carbonaceous fuels
  • C10J3/46—Gasification of granular or pulverulent flues in suspension
  • C10J3/54—Gasification of granular or pulverulent fuels by the Winkler technique, i.e. by fluidisation
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10J—PRODUCTION OF PRODUCER GAS, WATER-GAS, SYNTHESIS GAS FROM SOLID CARBONACEOUS MATERIAL, OR MIXTURES CONTAINING THESE GASES; CARBURETTING AIR OR OTHER GASES
  • C10J2300/00—Details of gasification processes
  • C10J2300/09—Details of the feed, e.g. feeding of spent catalyst, inert gas or halogens
  • C10J2300/0913—Carbonaceous raw material
  • C10J2300/0943—Coke
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10J—PRODUCTION OF PRODUCER GAS, WATER-GAS, SYNTHESIS GAS FROM SOLID CARBONACEOUS MATERIAL, OR MIXTURES CONTAINING THESE GASES; CARBURETTING AIR OR OTHER GASES
  • C10J2300/00—Details of gasification processes
  • C10J2300/09—Details of the feed, e.g. feeding of spent catalyst, inert gas or halogens
  • C10J2300/0983—Additives
  • C10J2300/0986—Catalysts

Definitions

• Patent 3,689,240 Aldridge et al.
• This patent discloses a method for producing a methane rich gas by steam gasifying petroleum coke in the presence of cesium carbonate at pressures in excess of 14 kg/cm 2
• Table II of this Patent it is disclosed that under certain conditions, which are not specifically stated, but which do include a pressure of 0 psig there is produced a gas containing 1.7 volume % of methane.
• the pressure is raised to 10.5 kg/cm 2 the gas thus produced from the steam gasification of petroleum coke contains 15.6 volume % methane.
• a further patent which discloses the steam gasification of a carbonaceous material is U.S. Patent ' 3,615,299.
• the patentees apparently attempted to develop a method to produce a hydrogen rich gas from the steam gasification of coke derived from coal.
• the Patentees did not succeed in. obtaining a gas containing less than about 3 volume % methane and, in order to produce a hydrogen rich gas, the patentees ' found it necessary to use a large excess of steam so that the resulting gas contained more than 60 volume % steam.
• a gas containing more than about 3 volume % methane and more than 60 volume % steam is highly undesirable if a gas containing at least 95 volume % hydrogen is desired as the end product.
• the present invention permits the production of a methane-lean synthesis gas (one containing, say, less than about 3 volume % methane) by the steam-gasification of petroleum coke in a fluidized bed in the presence of a potassium or sodium salt, utilizing low temperatures and pressures, and minimum amounts of steam with high steam conversion rates.
• a methane-lean synthesis gas one containing, say, less than about 3 volume % methane
• the process involves using a fluidized reactor (a fluidized gasification zone) within which is formed a fluidized mixture or bed of petroleum coke and a gasification catalyst which may be a potassium salt, a sodium salt, or mixtures thereof.
• a gasification catalyst which may be a potassium salt, a sodium salt, or mixtures thereof.
• the use of such catalysts allows the production of a methane lean synthesis gas when certain operating pressures and temperatures are used and when certain amounts of steam are used.
• the process also includes heating the reaction mixture of steam and carbon to the correct temperature by oxidizing a portion of the carbon in the petroleum coke using an oxygen containing gas such as air or, preferably,oxygen.
• Both temperature and pressure are critical in the present invention if the desired results are to be obtained, such results including the following: (1.) high steam conversion, generally greater than 30 and preferably 40 volume % of the steam reacts with the carbon contained in the petroleum coke, (2.) the gasification rate of the carbon contained in the petroleum coke is from 5 to 25 weight % per hour, (3.) the gas produced from the steam gasification reaction contains less than about 40 volume % steam, and preferably less than about 30 volume % steam, prior to the time when the steam is separated from the synthesis gasp (4.) the overall process converts over 90 weight % of the carbon in the petroleum coke to a synthesis gas and (5.) the synthesis gas contains less than about 3 volume % of methane and preferably less than about 2' volume percent methane on a nitrogen and steam free basis. In order to obtain the foregoing results the parameters under which the reaction takes place must be carefully controlled.
• the pressure at which the gasification reaction takes place in the present invention is sufficient to overcome the pressure drop in the fluidized gasification zone (a minimum of about 1.75 kg/cm 2 gauge, hereinafter kg/cm 2 , and preferably a minimum of about 3.5 kg/cm 2 but less than about 14 kg/cm 2 Therefore, in general, it may be said that the desired results discussed above are obtained when operating at pressures of between about 1.75 or 3.5 kg/cm 2 and 1 4 k g/cm 2 but, preferably, the pressures used will be between about 3.5 kg/cm 2 and 10.5 kg/cm 2 . We have found that excellent results occur when the preferred pressures are utilized.
• the temperature, at which the gasification reaction takes place, is also critical. In general we have found that temperatures between about 650°C and about 790°C will produce good results but it is preferable if the temperature is at least 700°C and, more preferably, at least 730°C. The preferred temperature range is between about 700°C and more preferably 7 3 0°C and 760°C.
• the amount of steam used is also critical.
• the amount of steam introduced into the gasifier will be between about 0.2 and about 1 part per weight of steam per hour per one part by weight of carbon in the fluid bed of the gasifier retort.
• the amount of steam introduced into the.gasifier is between about 0.3 and about 0.8 parts by weight of steam per hour per one part by weight of carbon.
• the temperature of the gasification reaction is maintained by introducing an oxygen containing gas into the gasification zone or retort to oxidize a portion of the carbon contained in the petroleum coke thereby raising the temperature. since it is desirable to utilize as little carbon as possible in the oxidation reaction, only that amount of oxygen is introduced to maintain the reaction temperature in the gasifier zone to between 650°C and 790°C. If it is desired to produce a substantially pure hydrogen gas or methanol then the oxygen' containing gas should be substantially pure oxygen instead of, e.g. air, since the presence of nitrogen in this situation is undesirable. On the other hand, if it is desired to produce ammonia high purity air, for example, may be used as the oxygen containing gas since, in this situation, the presence of nitrogen is not undesirable.
• the method of the present invention also includes the use of a specific type of a gasification catalyst, which may be either a potassium or sodium salt or both
• a gasification catalyst which may be either a potassium or sodium salt or both
• the particular amount of catalyst used is not very critical and may range between about 1 weight and about 50 weight % based upon the total weight of the petroleum coke and the catalyst in the gasifier. A more preferred range is between about 5 weight % and about 50 weight %.
• the catalyst may be added to the petroleum coke in any convenient manner. For example, prior to the introduction of the coke into the gasification retort or zone the catalyst may be added as a solid and a mixture of petroleum coke and catalyst formed. However, it is not necessary to mix the catalyst and the petroleum coke prior to the introduction of the two into the gasification zone or retort because fluidizing the two will form a mixture in the gasification retort itself. In addition to adding the catalyst as a solid to the coke prior to the introduction thereof into the fluidized gasification zone, the catalyst may also be added to the petroleum coke as an aqueous slurry or solution, depending upon the solubility of the particular catalyst in water. In this latter event, fluidizing the catalyst and coke in the fluidized reactor also forms a fluidized mixture of the two.
• the synthesis gas (i.e. the gas produced by the reaction between steam and carbon after removal of the excess steam) produced by the process of the present invention will in general contain about from about 40 to about 50 volume % hydrogen, from about 10 to about 25 volume % carbon monoxide, from about 30 to about 50 volume % carbon dioxide and from about 0.5 to about 1.7 volume % methane, it being understood that the foregoing percentages are on a steam, and if used, nitrogen free basis.
• Such a synthesis gas is ideal for producing methanol or a high purity product gas containing substantially only hydrogen and carbon dioxide.
• the instant method produces more carbon dioxide than would be expected based on the amount of oxygen used in the process.
• the oxygen reacts with the carbon to produce carbon dioxide. It would be expected that the carbon dioxide thus produced would be reduced by the carbon to produce carbon monoxide'. In other words, it would .be expected that there would be less carbon dioxide in the synthesis gas than the amount of oxygen used.
• This relatively high production of carbon dioxide is highly desirable since the reaction is exothermic and maximizes heat release thereby minimizing the amount of oxygen necessary to raise the temperature to 650°C to 790°C.
• the synthesis gas produced by the present invention is excellent for conversion into a product gas (i.e. a gas containing primarily hydrogen and carbon dioxide) by the well known water gas reaction wherein steam reacts with carbon monoxide, normally in the presence of an iron and/or chromium catalyst, to produce hydrogen and carbon dioxide.
• a product gas i.e. a gas containing primarily hydrogen and carbon dioxide
• the synthesis gas when subjected to the water shift reaction produces a product gas of approximately 70% hydrogen and 30% carbon dioxide with minor amounts of methane and carbon monoxide depending upon the respective amounts of hydrogen, carbon monoxide and carbon dioxide in the initial synthesis gas.
• the carbon dioxide is easily removed from the product gas by scrubbing the gas with either a chemical or a physical solvent by means well known in the art.
• the thus produced gas contains over 95 volume % hydrogen with trace amounts of carbon monoxide, carbon dioxide and a small amount of methane. Inasmuch as methane cannot be removed from the product gas in an economical manner, it is very undesirable to have methane in the initial synthesis gas.
• the gas produced by the present, invention is also excellent for conversion into methanol by the reaction of hydrogen with carbon monoxide and/or carbon dioxide in the- presence of certain catalysts such as zinc oxide.
• the particular reactor used for the gasification reaction is not critical and can be any of a well known number of reactors having differing sizes, shapes and configurations. However, in the preferred exemplary embodiment the particular type of reactor used was 10 metres long and had an internal diameter of 25 cm. In. most of the preferred exemplary embodiment fluid coke was used although as shown in Examples 13-15 delayed coke may also be used with equally good effect.
• the particular type of petroleum coke used contained approximately 0.5 weight % ash and about 2.5 weight % sulfur, although petroleum coke containing more or less ash and/or sulfur may be used to good effect. If the petroleum coke, either delayed or fluid, used herein contains relatively small amounts of sulfur then it is not necessary to remove the hydrogen sulfide from the gas produced by the gasification reaction.
• the hydrogen sulfide As is known in the art, during the gasification most of the sulfur in the coke is converted to hydrogen sulfide which is contained in the effluent gas from the reactor. After the solids which are entrained in the effluent gas are removed and after removal of steam the hydrogen sulfide, if desired, may easily be removed by conventional methods. For example, dry purification methods may be used utilizing bog iron ore which comprises ferric hydroxide or oxide. The gas is passed through the iron ore which is spread as a thin layer in large flat boxes having perforations therein. The gas passes through the iron ore and the hydrogen sulfide reacts with the ferric hydroxide to form ferrous sulfide. In addition, the gas may be desulfurized with activated carbon, the hydrogen sulfide absorbed on the carbon being oxidized by catalytic oxidation with air to form sulfur.
• the steam and oxygen may be introduced separately into the reactor or as a mixture.
• the steam and oxygen are introduced together at the bottom of the reactor through a gas distributor.
• the temperature at which the steam is injected into the reactor is not particularly critical but, in the preferred exemplary embodiment superheated steam at a temperature of 480 to 540°C was used.
• the initial amount of fluid coke and catalyst fed to the bed was about 180 kg and the bed of petroleum coke and catalyst was fluidized to a bed depth of about 5 metres and at a fluidizing velocity of about 0.3 to 0.6m per second. Under such conditions, the amount of oxygen necessary to maintain a .temperature of between about 650°C and 790°C was between about 14 kg per hour and 23 kg per hour.
• coke and catalyst were continuously fed to the fluidized reactor so that the weight concentration of the catalyst, based on the weight of the solids in the reactor was substantially constant.
• Hot gases containing entrained solid fines exit the top of the reactor and pass through an external first stage cyclone for removal of a portion of the entrained solids.
• the solids collected in this cyclone were reinjected near the bottom of the bed via an external dipleg.
• the hot gases leaving the first cyclone were then fed to a second cyclone providing a higher inlet gas velocity to effect more efficient fines removal.
• the fines from the second cyclone were withdrawn and fed back into the reactor to be further gasified. In this manner over 90 weight % of the unreacted petroleum coke is recycled into the reactor thus allowing at least 90 weight % conversion of the carbon contained in the petroleum coke.
• the hot gases leaving the cyclone which is essentially synthesis gas and steam, the amount of steam in said gas being between about 20 and 25 volume %, were conveyed to a venturi-type scrubber which contacts the hot gas with a recirculating water stream.
• a gravity separator de-entrained the water from the gas and heat was removed by a heat exchanger in the circulating water system. ' Scrubbed solids and condensed steam were purged from the scrubber system at a rate equal to the rate of production.
• the resulting synthesis gas which contained from 40 volume % to 50 .volume % hydrogen on a nitrogen free basis, with the steam and fines removed, was then used to produce a product gas by the water gas shift reaction and the carbon dioxide removed therefrom to produce a gas containing at least about 97 volume % hydrogen.
• oxygen flow is controlled based upon the temperature desired and the petroleum coke feed rate is controlled to maintain a constant bed level of approximately 5 metres.
• the amount of petroleum coke fed to the reactor, per hour was between about 14 kg and 27 kg depending on the amount of steam used and the gasification rate of the carbon.
• fluid petroleum coke was used in the method described above.
• the catalyst used was potassium carbonate and the concentration of catalyst in the reactor was about 8 weight %.
• the carbon gasification rate in each of Examples 1 through 5 was about 15 to 20 weight % per hour, the steam conversion rate was about 40% and the steam rate was about 0.45 parts by weight per hour per one part by weight of carbon in the reactor.
• the amount of hydrogen in the gas produced, on a steam and nitrogen free basis was between about 40 volume % and 50 volume %.
• the temperatures used, the pressure used, and the amount of methane formed, in volume %, is given below in Table 1 for each example:
• the same conditions were used as in the preceding examples except the steam rate was 0.32 parts by weight per hour per one part by weight of carbon'in the reactor, the steam conversion was about 38%, the carbon gasification rate was about 7 weight % per hour, and the concentration of catalyst in the reactor was about 20 weight %. Under these conditions, the volume % of methane in the thus produced gas was about 1.10 at a temperature of 680°C and a pressure of 2.2 kg/cm 2 .
• the catalyst used is potassium carbonate and its concentration in the reactor was between about 40 and 45 weight %.
• the steam space velocity is about 0.24 parts by weight of steam per one part by weight of carbon contained in the fluid coke.
• the temperatures was 700°C and the pressure was 2.95 kg/cm 2 steam conversion was approximately 55%.
• the gasification rate of the carbon is approximately 15 weight % per hour.
• the synthesis gas thus produced when unreacted steam is excluded from the gas, contains about 1.4 volume % methane which means that the hydrogen containing gas produced from such a synthesis gas will contain in excess of about 98 volume % hydrogen.
• a sufficient amount of unreacted coke is recycled to the reactor so that 95% of the carbon is converted to a synthesis gas, including the oxygen-carbon reaction.
• examples 1 through 5 the method described in examples 1 through 5 was utilized except delayed coke containing 9.1% volatile matter was used in lieu of fluid coke containing approximately 10% volatile matter.
• the catalyst used was potassium carbonate and the concentration of catalyst in the reactor was between 4.7 and 9.9 weight percent.
• the carbon gasification rates were between about 7.4 and 10.6 weight percent per hour.
• the steam conversion was between about 21 and 30 percent at steam rates of between 0.45 and 0.53 kg of steam per hour per kg of carbon.
• the amount of methane formed is comparable to the quantity of methane formed from fluid coke at essentially the same operating conditions (see examples 1 and 5).

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Combustion & Propulsion (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Organic Chemistry (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Hydrogen, Water And Hydrids (AREA)
• Catalysts (AREA)

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• 1980
  • 1980-05-27 AR AR28120780A patent/AR228573A1/es active
  • 1980-06-12 EP EP80301984A patent/EP0024792A3/fr not_active Withdrawn

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