Pyrolysis-based fuel processing method and apparatus

Abstract

The method for generating a hydrogen-rich stream from hydrocarbon fuels, ultimately to produce hydrogen gas, involves the following two steps performed in a cyclic fashion: (1) pyrolysis of the hydrocarbon fuel to obtain a carbon-rich fraction and a hydrogen-rich fraction; and (2) oxidation of the carbon-rich fraction, or a portion of it, for heat generation. The method involves the following optional steps: (3) steam gasification of part of the carbon-rich fraction to produce additional amounts of hydrogen and carbon monoxide; (4) water-gas shift reaction to convert carbon monoxide to carbon dioxide with the simultaneous formation of additional amounts of hydrogen; and (5) steam reforming of light hydrocarbons that may be produced in step (1) to produce more hydrogen and carbon monoxide.

Description

CROSS-REFERENCE TO RELATED APPLICATION [0001] This application claims the benefit of U.S. Provisional Application No. 60 / 216,888, filed Jul. 7, 2000, in the names of the inventors designated herein and bearing the same title.STATEMENT REGARDING GOVERNMENT INTEREST [0002] The United States Government has rights in this invention under National Science Foundation grant No. DMI-9632781.BACKGROUND OF THE INVENTION [0003] Fuel cells which are currently of commercial interest operate on streams of pure or nearly pure hydrogen, which is not readily available in most vehicles. Neither is a source of pure hydrogen convenient or safe to carry on board commercial trucks, buses or other vehicles. However, liquid hydrocarbons, such as diesel fuels, are easily available and their handling, storage and distribution are well developed. Consequently, the large-scale use of fuel cells is expected to require conversion of liquid fuels into a stream of pure hydrogen or hydrogen / CO2 mixtures, with only ...

AI Technical Summary

Benefits of technology

"The present invention provides a novel method for producing hydrogen gas from hydrocarbon materials using a reaction apparatus that includes means for absorbing and releasing thermal energy. The method involves pyrolysis of the hydrocarbon material, followed by combustion of the resulting carbon-rich residue, and steam gasification of a second portion of the carbon-rich residue. The method may also include the additional steps of water-gas shift reaction and steam reforming of gaseous hydrocarbons produced in the pyrolysis step. The power system includes a fuel cell that utilizes hydrogen for power generation, and the reaction apparatus for producing hydrogen gas is operatively connected for delivering hydrogen gas produced thereby to the fuel cell. The system is self-contained and may be part of a transportation vehicle."

Problems solved by technology

Fuel cells which are currently of commercial interest operate on streams of pure or nearly pure hydrogen, which is not readily available in most vehicles.

In this bus, compressed hydrogen is used to fuel the cells, which has raised concerns about passengers' safety.

The fact that methanol is not currently a widely used fuel poses obvious limitations.

There are also concerns related to long-term viability as well as corrosiveness and toxicity of methanol.

However, partial oxidation produces relatively small amounts of gaseous hydrogen, which is diluted with nitrogen, large amounts of carbon oxides and soot, and the efficiency of fuel utilization is relatively low.

Steam reforming is a well-established large scale technology, but design, construction, and operation of compact reformers is quite a challenge.

The use of heavier feedstocks, such as naphtha, is difficult, and this problem can be only partly alleviated by the use of specially prepared catalysts (Austin, G. T., Shreve's Chemical Process Industries, Fifth edition, McGraw-Hill, New York, 1984).

The advantages of ATR include compactness, and nitrogen dilution is the main disadvantage.

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