Method for the gasification of hydrocarbon feedstocks

Abstract

A method for the gasification of a hydrocarbon-bearing feedstock 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 also produced by reacting steam (H2O) with a metal. The method can advantageously produce two separate syngas streams, one that is CO-rich and one that is H2-rich.

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.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 while reducing the formation of carbon dioxide (CO2) as compared to other gasification methods. [0004] 2. Description of Related Art [0005] Gasification is a well-known process that converts hydrocarbon materials such as coal, petroleum coke, biomass or similar feedstocks into a syngas comprising carbon monoxide (CO) and hydrogen (H2). During gasification, pyrolysis of the hydrocarbon material releases...

AI Technical Summary

Benefits of technology

[0028] It is 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.

[0029] For the production of H2, both conventional gasification (discussed above) and the gasification method of the present invention utilize the affinity of carbon to capture O2 as the driving force to dislodge O2 from water and form H2. However, the gasification method of the present invention utilizes a unique chemical pathway as compared to conventional gasification. As is noted above, conventional gasification produces the majority of H2 by stripping the oxygen from H2O with the conversion of CO to CO2 via the water-gas shift reaction (Equation 4). In contrast, the method of the present invention produces a majority of H2 by stripping the oxygen from H2O with an intermediary, metallic iron, derived by reducing FeOx with the energy released during the transition of C to CO, and produces only a minor portion of the overall H2 by stripping oxygen from H2O with the conversion of CO to CO2.

[0030] Upon heating a given quantity of a solid hydrocarbon feedstock, the fuel-bound H2 is released and can be recovered by both conventional gasification and the gasification method of the present invention. The remaining solid carbon is gasified to CO (Equation 2), but in the present invention, this occurs by a different endothermic reaction: C+FeO→Fe+CO  (10)

[0031] Both gasification processes can burn additional carbon in O2 to produce the balancing heat that is required for the reaction (Equation 3).

[0032] The gasification method of the present invention, however, must regenerate the FeO in order to continue gasifying the incoming carbon. According to the present invention, regeneration is achieved by oxidizing the iron with steam, such as is illustrated by Equation 9.

[0033] Thus, virtually all of the H2 that is produced according to the present invention (excluding fuel bound hydrogen) derives from this source, namely the oxidation of C to CO, and the production of CO2 is therefore reduced as compared to conventional gasification.

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 an availability of less than about 75 percent causing disruptions in the manufacture of syngas.

This low availability is too disruptive to most follow-on processing, for example, the refining of crude oil or manufacture of ammonia.

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

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