Method for the gasification of moisture-containing hydrocarbon feedstocks

Abstract

A method for the gasification of a hydrocarbon feedstock that has a high moisture content to produce useful co-products such as high-value hydrocarbon fuels, pure H2, electricity, and / or ammonia. The method advantageously gasifies the carbon in the feedstock to carbon monoxide (CO) without producing large quantities of carbon dioxide (CO2). Supplemental hydrogen (H2) is co-produced by reacting steam (H2O) generated from the moisture in the hydrocarbon feedstock with a molten metal.

Description

CROSS REFERENCE TO RELATED APPLICATIONS [0001] This application claims priority to U.S. Provisional Patent Application No. 60 / 746,748 filed May 8, 2006, which is incorporated herein by reference in its entirety as if set forth in full. This application is also related to co-pending U.S. patent application Ser. No. 11 / 746,013 filed on May 8, 2007 and entitled “Method for the Gasification of Hydrocarbon Feedstocks”, which is also incorporated herein by reference in its entirety.BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention is directed to a method for the gasification of hydrocarbon feedstocks to produce a syngas that is useful for the production of hydrogen, hydrogen-containing materials, electricity or other energy products. The method advantageously produces such high-value products, and can reduce the formation of carbon dioxide (CO2) per unit of energy or commodity produced, as compared to other gasification methods. [0004] 2. Descriptio...

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Benefits of technology

[0029] It is also an advantage of the present invention that the solid or liquid hydrocarbons used as the feedstock can be low-value, contaminated hydrocarbons. The method can also have a lower capital cost than conventional gasification.

[0030] The syngas stream that can be produced according to the present invention advantageously has a higher CO:CO2 ratio than the syngas stream from conventional gasification. For conventional gasification, a minimum ratio of CO:CO2 must be established to extract H2 from water. Gasification according to the present invention involves oxidation of the metal (iron) as represented by Equation 5 and reduction of the just-formed oxide by carbon as illustrated by Equation 6. Addition of Equations 5 and 6 eliminates the metal and metal oxide and leaves just carbon to reduce the water, the same reaction as for conventional gasification. Therefore, based upon a superficial comparison, the same CO:CO2 ratio should be required in both cases.

[0031] However, to create the metallic iron, a source of hydrogen in the present invention, FeO must yield its oxygen to carbon. Because the FeO is in ionic solution with other oxides comprising a slag and because the cations of the other oxides in the slag also exert a binding force on the oxygen, additional energy is required to extricate the oxygen from the mixture of FeO and other oxides. The additional energy required to extricate the oxygen from the solution of mixed oxides arises from combusting additional carbon to increase the ratio of CO:CO2.

[0032] Syngas with a high ratio of CO:CO2 contains more energy than syngas with a low ratio of CO:CO2. Therefore, more useful work can be obtained from a given amount of high CO:CO2 syngas per unit of CO2 produced than from a syngas with a lower CO:CO2 ratio. This is a significant advantage of the present invention.

[0033] The syngas stream, after heat recovery and purification, is comprised of CO and H2 in a molecular ratio generally reflecting the C:H ratio in the hydrocarbon feedstock that is being reacted, and the CO content is greater than the H2 content. The method of the present invention can also co-produce electricity, nitrogen, sulfur and pozzolanic slag along with the syngas stream. The value of these salable co-products can substantially or completely off-set the cost of H2 production.

[0034] The syngas stream and co-produced electricity can be merged in various ways that utilize substantially all of the energy contained therein for subsequent conversion into H2 or H2-containing commodities and / or additional electricity and / or steam. By way of example, the commodities can be selected to include: pure hydrogen; pure hydrogen and electricity and / or steam; ammonia, electricity and / or steam; methane, electricity and / or steam; liquid fuels such as gasoline, diesel and jet fuel, electricity and / or steam; or solely electricity and / or steam. Steam is useful as a source of process heat required by many industries.

Problems solved by technology

As a result, the syngas derived from solid hydrocarbons by conventional gasification has a H2:CO ratio that is virtually always less than one, which is too low to be used for manufacturing the high-value hydrogen-containing materials that are needed for commerce.

Accordingly, while H2 production by coal gasification is an established commercial technology, it is only economically competitive with steam-methane reformation (SMR) for the production of H2 when natural gas is prohibitively expensive.

Among other factors, such coal gasification plants have a high capital cost and the gasification reactors generally have a low availability, about 75 percent, causing disruptions in the manufacture of syngas.

Such a low availability is generally unsatisfactory for downstream manufacturing processes that utilize the syngas (or syngas converted to hydrogen) for oil refining or ammonia production.

Once the oxides are formed, they cannot be effectively reduced back to the metal.

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