MXPA01007014A - Reclaiming of purge gas from hydrotreaters and hydrocrackers - Google Patents

Abstract

The invention is a process to recover a high pressure hydrogen-rich gas stream from a purge gas stream taken from a hydrotreater. This purge gas stream is admixed with synthesis gas that was the original source of the hydrogen to form a gaseous mixture. This mixed gas comprising purge gas and synthesis gas is advantageously treated to remove acid gases and possibly other impurities. The mixed gas is then treated to extract a hydrogen-rich gas and a hydrogen-depleted gas using, for example, a membrane. At least a portion of the hydrogen-rich gas is then heated and compressed as necessary and is recycled to the hydrotreater.

Description

RECOVERY OF PURGE GAS FROM HYDROPURICANTS AND HYPROTRACTORS Priority of the provisional application of E.U.A. No. 60/1 15,391, filed July 1, 1999.

BACKGROUND OF THE INVENTION The production of synthesis gas from solid or liquid carbonaceous fuels, especially carbon, coke, and liquid hydrocarbon feeds, has been used for a considerable period and has recently seen significant improvements due to the increased energy demand and the need for a clean use of other low value carbonaceous materials. The synthesis gas can be produced by heating carbonaceous fuels with reaction gases, such as air or oxygen, often in the presence of steam and / or water in a gasification reactor to obtain the synthesis gas, which is separated from the gasification reactor. The gasification and subsequent combustion of certain carbonaceous materials provide a method, which does not harm the environment, to generate fuel for energy in addition to the chemicals needed from the supply material otherwise would damage the environment. Supply materials based on coal, petroleum, including petroleum coke and other carbonaceous materials, waste hydrocarbons, waste oils and byproducts of heavy crude oil are commonly used for gasification reactions. The synthesis gas mixtures comprise carbon monoxide and hydrogen. Hydrogen is a commercially important reagent for hydrogenation reactions. The synthesis gas can also be used to generate energy from other environmentally unacceptable fuel sources, and as a source of feed gas for the synthesis of hydrocarbons, organic compounds containing oxygen or ammonia. Other materials that are often found in synthesis gas include hydrogen sulfide, carbon dioxide, ammonia, hydrocarbons, cyanides, and particulates in the form of carbon and trace metals. The degree of contaminants in the feed is determined by the type of feed and the particular gasification process used, as well as the operating conditions. In any case, the removal of these contaminants is very important to make gasification a viable process. As the product gas is discharged from the gasifier, it is usually subjected to a cooling and cleaning operation involving a cleaning technique where the gas is introduced into a scrubber and makes contact with a water spray that cools the gas and eliminates the particles and the ionic constituents of the synthesis gas. The initially cooled gas can then be treated to desulfurize the gas before using the synthesis gas. When the desired product is hydrogen, the synthesis gas from the gasifier changes using a catalyst to form hydrogen as shown below. H2O + CO = H2 + CO2 The change procedure, also called the gas change procedure with water or reforming steam, converts water and carbon monoxide to hydrogen and carbon dioxide. The process of change is described, for example, in the patent of E.U.A. No. 5,472,986, the disclosure of which is incorporated herein by reference. Hydrogen gas is often used in subsequent processes, particularly in hydro-hydration. For many applications, especially for hydrocarbon hydrocarbons, hydrogen is required at a higher purity and at pressures ranging from about 6895 kPa to about 20684 kPa. The changed synthesis gas must therefore be purified to meet the specifications of the product. The synthesis gas is processed to provide a gas stream rich in hydrogen and a gas stream rich in carbon dioxide / carbon monoxide. Other impurities in the gas generally follow the gas stream rich in carbon dioxide / carbon monoxide. One method for purifying the gas is by the pressure swing absorption method. This method has a high cost and requires a large outflow of capital.

A membrane system can also be used to modify the separation. A membrane allows small molecules, such as hydrogen, to pass through (infiltrate) while large molecules (CO2CO) do not infiltrate. The membranes are a cost-effective alternative to the oscillating pressure absorption unit. The membranes reduce the hydrogen pressure of the product so that they must be compressed before use. For example, the hydrogen pressure of product when purified using a membrane is substantially less than that required by the hydropurifiers.

BRIEF DESCRIPTION OF THE INVENTION The invention is a method for recovering hydrogen from a purge gas stream taken from a hydropurifier. The hydropurifier gas and a liquid hydrocarbon stream react in the hydropurifier. The gas flowing in the hydropurifier is divided, a fraction being mixed with hydrogen to form hydropurifier gas, which is subsequently introduced to the hydropurifier. A purge gas stream comprising hydropurifier effluent gas is mixed with synthesis gas. This mixed gas comprising purge gas and synthesis gas is usefully treated to remove acid gases and possibly other impurities. The mixed gas is then treated to extract a stream of hydrogen gas and a remaining hydrogen gas / carbon monoxide stream using, for example, a membrane. The hydrogen gas stream is recycled to the hydropurifier.

DETAILED DESCRIPTION OF THE INVENTION The invention involves the integration of oil refining and gasification, and in particular the integration of de-skimming, gasification and solvent hydropurification. In particular, the invention is a method for recovering hydrogen from a purge gas stream taken from a hydropurifier, where gasification and adjoining gas treatment facilities are also available. The process for recovering hydrogen from a purge of hydropurifier effluent gas comprises removing the hydropurifier effluent gas from the hydropurifier and separating a portion designated as purge gas with the remanent designated recirculating hydropurifier effluent gas. The purge gas stream is then admixed with a stream of synthesis gas, thereby creating a mixed gas stream. The gasification plant that produces the synthesis gas has facilities for the removal of acid gas and facilities to produce separate hydrogen gas and fuel streams. The mixed gas is subjected to this process, and the hydrogen is admixed with the recycled hydro-purifying effluent gas to form a hydropurifier gas. This hydropurifier gas is subsequently introduced to the hydropurifier.

In one embodiment of the invention, a deasphalted oil is separated from a heavy crude oil through solvent extraction. Extraction residues, asphaltenes, are low-value hydrocarbon material. Such material can be usefully gasified to generate hydrogen, energy, steam and synthesis gas for chemical production. Such a method advantageously has gas treatment facilities that can usefully be used in the process of the present invention. The deasphalted oil can be processed in a source of high-value diesel oil in a fluidized catalytic crusher unit. Deasphalted oil generally contains significant amounts of compounds that contain sulfur and nitrogen. This deasphalted oil can also contain long-chain hydrocarbons. To comply with environmental standards and product specifications, as well as to extend the life of the catalyst, the feed of the fluidized catalytic grinding unit is first hydropurified to remove the sulfur components. This invention is a method for treating and recovering a portion of the purge gas from this hydropurification process. As used herein, the terms "hydropurification", "hydrotreating" and "hydrogenation" are used interchangeably to mean the reaction of a hydrogen gas with a hydrocarbon mixture, where the hydrocarbon mixture usually contains sulfur components. and others that are not suitable.

During hydropurification, hydrogen makes contact with a hydrocarbon mixture, optionally in the presence of a catalyst. The catalyst facilitates the breakdown of carbon-carbon, carbon-sulfur, carbon-nitrogen and carbon-oxygen bonds and hydrogen bonding. The purpose of hydro-hydro is to increase the value of the hydrocarbon stream by removing the sulfur, reducing the acidity and creating smaller hydrocarbon molecules. As used herein, the term "hydrogen" means a gas comprising more than about 80 mol%, preferably more than about 90 mol% of molecular hydrogen gas. The pressure, temperature, fluid velocity and catalysts required to complete the hydrogenation reactions are already known in the art. Typical conditions for thermal hydrotritating are as follows: the reaction temperature is from about 300 ° C to about 480 ° C; the partial pressure of hydrogen is about 30 kg per cm2 to about 200 kg per cm2; the speed in liquid space from about 0.1 per hour to 2.0 per hour. Catalysts can often be added, often at about 0.01 to 0.30 weight per weight of fluid. Hydropurification is most effective when the hydrocarbon mixture makes contact with relatively pure hydrogen. Hydropurification requires a hydrogen-rich gas comprising more than about 80 mol% hydrogen gas. Hydropurification creates volatile hydrocarbons, hydrocarbons containing volatile sulfur and nitrogen, hydrogen sulfide and other gaseous pollutants. However, the gas leaving the hydropurifier is predominantly hydrogen. This gas is usefully recycled to the hydropurifier. An excess amount of hydrogen is present during the reaction. During the hydropurification process, hydrogen sulfide and short-chain hydrocarbons are formed, such as methane, ethane, propane, butane and pentane. When the gas stream leaves the reactor, it is still mainly hydrogen. The gas stream also contains vaporized hydrocarbons, gaseous hydrocarbons such as methane and ethane, hydrogen sulfide and other contaminants. This gas stream is treated to remove the condensable materials and then recycled to the hydropurifier reactor. Removal of the condensable materials requires that the hydropurifier effluent gas be cooled to between about 0 ° C near 100 ° C, preferably from about 0 ° C to about 30 ° C. However, the non-condensable byproducts of the hydropurification reaction accumulation, and the purge stream must be separated from the recycled gas stream to prevent impurities from accumulating at concentrations that inhibit the hydropurification reaction. This stream of purge gas is mixed with synthesis gas that was the original source of hydrogen. As used herein, the term "synthesis gas" refers to gases comprising both hydrogen gas and carbon monoxide gas in amounts of more than 5 mol% in each. The molar ratio of hydrogen to carbon monoxide can be, but not necessarily, about 1 to 1. There are often some inert elements in the synthesis gas, particularly nitrogen and carbon dioxide. Often there are pollutants such as hydrogen sulfide and COS. The synthesis gas is prepared by partially burning a hydrocarbon fuel and oxygen in a reactor, often in the presence of stream and / or water, in proportions that produce a mixture containing carbon monoxide and hydrogen in the reactor. The term "hydrocarbon" as used herein describes various types of supply materials and is intended to include gaseous, liquid and solid hydrocarbons, carbonaceous materials and mixtures thereof. In fact, substantially any organic material that contains combustible carbon, or suspensions thereof, may be included within the definition of the term "hydrocarbon". The solid, gaseous and liquid supply materials can be mixed and used simultaneously, and these can include paraffinic, olefinic, acetylenic, naphthenic, asphaltic and aromatic compounds in any proportion. The hydrocarbon fuels are reacted with a gas containing oxygen, such as air, or substantially pure oxygen having more than about 90 mole% oxygen or oxygen enriched air having more than about 21 mole% oxygen. Substantially pure oxygen is preferred. The partial oxidation of the hydrocarbon material is completed, optionally in the presence of a steam temperature control moderator, in a gasification zone to obtain the hot partial oxidation synthesis gas. The synthesis gas can be made by any partial oxidation method. Preferably, the gasification process uses substantially pure oxygen with about 95 mol% oxygen. Gasification processes are already known in the art. See, for example, the patent of E.U.A. No. 4,099,382, and the patent of E.U.A. No. 4,178,758, the descriptions of which are incorporated herein by reference. In the gasification reactor, the hydrocarbon fuel makes contact with a gas containing free oxygen, optionally in the presence of a temperature moderator. In the reaction zone, the content will commonly reach temperatures in a range of about 900 ° C to 1700 ° C, and typically in a range of 1 100 ° C to about 1500 ° C. typically it will be in a range of about one atmosphere (101, 325 kPa) to about 250 atmospheres (25,331 kPa), and very typically in a range of about 15 atmospheres (1519 kPa) to about 150 atmospheres (15190 kPa) , and even more commonly in a range of about 5516 kPa to about 13789 kPa. The synthesis gas is cooled and washed of contaminants, preferably with energy recovery as by steam rise and / or steam superheat. This can be followed by recoveries of lesser degree of heat, as in the production of conventional synthesis gas. The gas is typically purged, but not necessarily, admixed with the synthesis gas after some heat has been extracted from the synthesis gas. There may be other conventional gas treatment steps such as steam removal and, when appropriate, composition adjustment. In case the hydrogen gas is a desired product, it is useful to subject the synthesis gas, or the mixed gas, to a steam reforming to increase the relative production of hydrogen gas. Steam reforming is a process of adding water, or using water contained in the gas, and reacting the resulting gas mixture adiabatically on a steam reforming catalyst. The primary purpose of reforming steam is to increase the amount of hydrogen in the gas mixture. The synthesis gas contains hydrogen sulfide (H2S) and COS formed from sulfur and feed to the gasifier. The COS is changed in the steam reformer following the same reaction path as carbon monoxide to form hydrogen sulfide and carbon dioxide. The synthesis gas composition of a gasification reaction is typically hydrogen gas of 25 to 45 mole%, carbon monoxide gas of 40 to 50 mole%, carbon dioxide gas of 10 to 35 mole%, and tracer pollutants . In a reformed vapor synthesis gas a typical composition is hydrogen gas at 35 to 65 mole%, carbon monoxide gas at 0.3 to 10 mole%, carbon dioxide gas at 30 to 60 mole%, and tracer pollutants These margins are not absolute, and can change with gasified fuel as well as gasification parameters. The steam reforming catalyst is one or more of the group VIII metals in a heat-resistant support. Randomly packaged ceramic supported catalyst parts can be used, as used for example in secondary reformers, but, because this applies a drop in the significant pressure to the gas, it is often useful to use a monolithic catalyst having passages generally parallel to the flow direction of the reactants. The temperature of the gas during steam reforming is typically in a range of 398 ° C to 565 ° C. This procedure can be carried out before recovering the heat of the synthesis gas. The acid gas removal facilities for the synthesis gas, with its amine or physical solvents, remove the acid gases, particularly hydrogen sulfide, from the mixed stream of synthesis gas / purge gas. Acid gas removal facilities typically operate at lower temperatures. After the synthesis gas is cooled to below 130 ° C, preferably below 90 ° C, the contaminants in the gas, especially sulfur compounds and acid gases can be easily removed. Hydrogen sulfide, an acid gas, is easily removed from the synthesis gas. The type of fluid that reacts with the acid gas is not important. Conventional amine solvents, such as MDEA, can be used to remove hydrogen sulphide. Physical solvents such as SELEXOL (TM) and RECTIXOL (TM) can also be used. The fluids may be solvents such as minor monohydric alcohols, such as methanol, or polyhydric alcohols such as ethylene glycol and the like. The fluid may contain an amine such as diethanolamine, methanol, N-methyl-pyrrolidone, or a polyethylene glycol dimethyl ether. Physical solvents are typically used because they work best at high pressure. The synthesis gas makes contact with the solvent in an acid gas removal contactor. Said contactor may be of any type known in the art, including trays or a packed column. The operation of such an acid removal contactor is already known in the art. It is preferred that the design and operation of the acid gas removal unit result in a minimum pressure drop. The pressure of the synthesis gas is therefore preserved. It is very useful to add purge stream to the synthesis gas before running the synthesis gas through the acid gas removal unit. Utilities include, but are not limited to, the economy of having a unit running for the removal of polluting gases, especially acid gases such as hydrogen sulfide, and the enrichment of the synthesis gas in the concentration of hydrogen. In a preferred embodiment of the present invention, at least a portion of the purge gas from the hydropurifier is guided through the synthesis gas of the acid gas removal unit, and subsequently through a separation unit as a membrane, to remove contaminants and increase the concentration of hydrogen in the purge gas rich in recycled hydrogen. The pressure of the ground stream of synthesis gas / purge gas is from about 3447 kPa to about 13789 kPa, typically between about 5516 kPa and 8274 kPa. The temperature of the crushed gas is extremely variable. Synthesis gas / mixed purge gas enters the gas separation unit, like a membrane designed to allow hydrogen molecules to pass through and block larger molecules such as carbon monoxide. The membrane can be of any type which preferably is for infiltration of hydrogen gas over carbon dioxide and carbon monoxide. Various types of membrane materials are known in the art, which have a high preference for the diffusion of hydrogen as compared to nitrogen. Such membrane materials include those compounds of silicon rubber, butyl rubber, polycarbonate, poly (phenylene oxide), nylon 6,6, polystyrenes, polysulfones, polyamides, polyimides, polyetiomers, polyarylene oxides, polyurethanes, polyesters, and the like. . The membrane units can be of any conventional construction, and a hollow fiber type construction is preferred. A gas rich in hydrogen infiltrates gas through the membrane. The infiltrate experiences a significant pressure drop between about 3447 kPa and 4826 kPa as it passes through the membrane. This hydrogen-rich gas is then heated and compressed as necessary, and at least a portion is recycled to the hydropurifier. The hydrogen-rich gas usefully comprises more than about 80 mol%, most preferably more than about 90 mol%, of hydrogen gas. The non-infiltrated gas stream from the membrane contains carbon dioxide, carbon monoxide, and some hydrogen. Other compounds, in particular volatile hydrocarbons, may also be present. This non-infiltrated makes a good fuel for the combustion turbines. The pressure of the non-infiltrator is virtually unaffected by the membrane. The pressure of this infiltrate is usefully reduced before being burned in a combustion turbine. In an important embodiment of the present invention, the purge gas from a subsequent hydropurification process is combined with the synthesis gas before contacting the gas mixture with the amine solvents or physical solvents, but after reforming the vapor . In another embodiment of this invention, the gas streams are admixed before the treatment in the steam reforming unit. The COS can be changed to hydrogen sulfide and carbon monoxide. Just as carbon monoxide can, of course, be converted to hydrogen and carbon dioxide. This is not necessary for the invention, hydrocarbons and carbon monoxide can also usefully be used in the non-infiltrated fuel.

The hydrogen is mixed with recycled hydrogen from the hydropurifier that has been compressed to the proper pressure. The hydrogen sulfide of the acid gas removal unit is guided to an acid gas stream which is sent to a sulfur recovery process. In view of the above description, one skilled in the art will understand and appreciate that at least one embodiment of the present invention includes a method for recovering a hydrogen from a purge of hydropurifier effluent gas. Such an embodiment of the process of the present invention includes: a) reacting a hydrocarbon stream and hydropurifier gas in a hydropurifier, thereby forming an effluent hydropurifier gas and a liquid product; b) remove the hydropurifier effluent gas; c) separating a portion of the hydropurifier effluent gas, thereby creating a recycling hydropurifier effluent gas stream and a purge gas stream; d) mixing the purge of the hydropurifier effluent gas with a stream of synthesis gas, thus creating a mixed gas stream; e) treating said mixed gas stream to produce separate hydrogen gas and fuel streams; and f) admixing the recycle hydropurifier effluent gas with at least a portion of the hydrogen stream to form a hydropurifier gas, wherein said hydropurifier gas is introduced to the hydropurifier. It is preferred that the hydropurifier effluent gas include hydrogen gas, hydrogen sulfide and methane. In a preferred embodiment the cooling of the hydropurifier effluent gas at a temperature between about 0 ° C and about 100 ° C to remove the condensable materials before step (c) and most preferably at a temperature between about 0 ° C is preferred. about 50 ° C to remove the condensable materials before step (c). In addition, the process can include the removal of the acid gases from the mixed gas from step (e) before separating the mixed gas into hydrogen and fuel gas streams. Typically, acid gases are composed of hydrogen sulfide. It is contemplated that the acid gas removal process includes that the admixed gas makes contact with one or more of SELEXOL (TM), RECTIXOL (TM), dietalonamine, methanol, N-methyl-pyrrolidone or a dimethyl ether of polyethylene glycol. The process is preferably carried out with hydropurifier gas which is composed of more than about 80 mole% hydrogen gas, in a preferred embodiment, the synthesis gas is composed of from about 25 mole% to about 45 mole% gas of hydrogen, from about 40% molar to about 50% molar of carbon monoxide gas, and from about 10% molar to about 35% molar of carbon dioxide gas. The process may preferably include a synthesis gas which is a synthesis gas with reformed stream comprising from about 35 mol% to about 65 mol% hydrogen gas, about 0.2 mol% to about 10 mol% gas carbon monoxide, and about 30% moiate to about 60% molar of carbon dioxide gas. In another embodiment of the present invention the process is such that the separation of the mixed gas in hydrogen gas and fuel streams comprises that the mixed gas makes contact with a membrane designed to allow the hydrogen molecules to pass through, but without block the larger molecules. The membrane is preferably composed of one or more of silicon rubber, butyl rubber, polycarbonate, poly (phenylene oxide), nylon 6,6, polystyrenes, polysulfones, polyamides, polyimides, polyethers, polyarylene oxides, polyurethanes and polyesters. In addition, the process may include heating and compressing the hydrogen gas before introducing at least a portion of the gas to the hydropurifier. It is preferred that the hydrogen be composed of more than about 90 mol% hydrogen gas. The procedure, furthermore, it may include reforming steam of the mixed gas from step (e) before separating the mixed gas into hydrogen and fuel gas stream, wherein the reforming stream comprises reacting water and the gas mixture on a reforming stream. catalytic It is preferred that the catalytic reforming stream be one or more of the group VIII metals in a heat-resistant support, and wherein the gas temperature is between approximately 398 ° C and 565 ° C.

While the compositions and methods of the present invention have been described from the point of view of the preferred embodiments, it will be apparent to those skilled in the art that various variations to the process described herein can be explained without departing from the concept and scope of the invention. . All such substitutes and modifications evident to those skilled in the art are claimed to be within the scope and concept of the invention as set forth in the following claims.

Claims (16)

NOVELTY OF THE INVENTION CLAIMS

1. - A method for recovering a hydrogen from a hydropurifier effluent gas purge, said method comprising: a) reacting a stream of hydrocarbon and hydropurifier gas in a hydropurifier, thereby forming a hydropurifying effluent gas and a liquid product; b) remove the hydropurifier effluent gas; c) separating a portion of the hydropurifier effluent gas, thereby creating a recycling hydropurifier effluent gas stream, and a purge gas stream; d) mixing the purge of the hydropurifier effluent gas with a stream of synthesis gas, thereby creating a mixed gas stream; e) treating said mixed gas stream to produce separate streams of hydrogen and fuel gas; and f) admixing the recycle hydropurifier effluent gas with a portion of the hydrogen stream to form a hydropurifier gas, wherein said hydropurifier gas is introduced to the hydropurifier.

2. The process according to claim 1, further characterized in that the hydropurifier effluent gas comprises hydrogen gas, hydrogen sulfide, methane and other light hydrocarbons.

3. The process according to claim 1, further characterized in that it comprises cooling the hydropurifier effluent gas between about 0 ° C and about 100 ° C to remove the condensable materials before step (c).

4. The process according to claim 1, further characterized in that it comprises cooling the hydropurifier effluent gas between about 0 ° C and about 50 ° C to remove the condensable materials before step (c).

5. The method according to claim 1, further characterized in that it comprises the removal of the acid gases from the mixed gas from step (e) before separating the mixed gas into the hydrogen and fuel gas streams.

6. The process according to claim 5, further characterized in that the acid gases comprise hydrogen sulfide.

7. The method according to claim 5, further characterized in that the removal of acid gases comprises that the admixed gas makes contact with one or more of SELEXOL ™, RECTIXOL ™, diethanolamine, methanol, N-methylpyrrolidone, or a propylene glycol dimethyl ether.

8. The process according to claim 1, further characterized in that the hydropurifying gas comprises more than about 80 mole% hydrogen gas.

9. The process according to claim 1, further characterized in that the synthesis gas comprises from about 25 mol% to about 45 mol% hydrogen gas, about 40 mol% to about 50 mol% gas of carbon monoxide, and about 10% molar to about 35% molar of carbon dioxide gas.

10. The process according to claim 1, further characterized in that the synthesis gas is a synthesis gas reformed by steam and comprises about 35 mol% to about 65 mol% hydrogen gas, about 10 mol% to about 20% molar of carbon monoxide gas and about 30% molar to about 60% molar of carbon dioxide gas.

11. The process according to claim 1, further characterized in that the separation of the mixed gas from step (e) in hydrogen gas and fuel streams comprises that the mixed gas makes contact with the membrane designated to allow the molecules of hydrogen pass through but blocks the larger molecules.

12. The process according to claim 1, further characterized in that the membrane comprises one or more of silicon rubber, butyl rubber, polycarbonate, poly (phenylene oxide), nylon 6.6, polystyrenes, polysulfones, polyamides, polyimides, polyethers, polyarylene oxides, polyurethanes and polyesters.

13. The method according to claim 1, further characterized in that it comprises heating and compressing the hydrogen gas before introducing at least a portion of the gas to the hydropurifier.

14. - The process according to claim 1, further characterized in that the hydrogen comprises more than about 90 mol% hydrogen gas.

15. The process according to claim 1, further characterized in that it comprises reforming vapor of the mixed gas of step (e) before separating the mixed gas into hydrogen gas and fuel streams, wherein the reforming vapor comprises reacting water and the gas mixture on a catalytic reforming stream.

16. The process according to claim 15, further characterized in that the reforming current catalyst is one or more of the group VIII metals in a heat-resistant support, and wherein the temperature of the gas is between of 750 ° C and about 1050 ° C.