Hydrogen generation processes and apparatus and control system

#This invention relates to processes for generating hydrogen involving the partial oxidation and reforming of fuel, especially to autothermal reforming processes, which can operate over a range of hydrogen production rates using a variety of fuels while still providing attractive net efficiencies of hydrogen generation. The hydrogen generators using the processes of this invention may find beneficial use in smaller-scale hydrogen plants.

#Hydrogen is used as a feedstock for many chemical processes and has been proposed as an alternative fuel especially for use in fuel cells in stationary and mobile facilities. Steam reforming of hydrocarbon-containing feedstock is a conventional source of hydrogen. Steam reforming of hydrocarbons is practiced in large-scale processes, often at a facility having refinery or chemical operations. Thus, for instance, the large-scale hydrogen plant will likely be able to draw upon the skills within the entire facility to operate sophisticated unit operations to enhance hydrogen production efficiency. An additional benefit of having a large scale hydrogen plant within a facility having refinery or chemical operations is that the steam generated in the hydrogen plant from cooling the steam reforming effluent and by heat exchange with the combustion of waste gases has value to such other refinery or chemical operations. The benefits of practicing steam reforming in large-scale plants are also apparent from the nature of the equipment and process. For instance, steam reforming generally uses very high temperatures, often in excess of 800° C., which in turn requires expensive materials of construction. Furthermore, large-scale hydrogen plants typically provide hydrogen product purity in excess of 99 volume percent with less than 10 parts per million by volume (ppmv) of carbon monoxide.

#While the economics of large-scale steam reforming make attractive the shipping of hydrogen from such a large-scale reformer to the point of use, hydrogen, nevertheless, is difficult to store and distribute and has a low volumetric energy density compared to fuels such as gasoline. Thus an interest exists in developing economically and practically viable smaller-scale hydrogen generators to provide hydrogen from a hydrocarbon-containing feedstock for use or distribution at a point proximate to the consumer.

#The drawing is schematic flow diagram of a process in accordance with this invention.

#Feed Components:

#The fuels used for reforming contain carbon and may be normally gaseous, liquid or solid, but need to be substantially gaseous under reforming conditions. The fuels may be substantially hydrocarbon such as hydrocarbon gases such as methane, ethane, propane, butane and the like; hydrocarbon liquids such as petroleum fractions containing 5 or more carbons including gasoline and kerosene fractions, or even hydrocarbon solids such as waxes that are gaseous under the reforming conditions such as cetane. Other fuel types include oxygenated hydrocarbons such as alkanols, alkane diols and alkane triols, carboxylic acids, carboxylic esters, aldehydes, ketones, and ethers such as ethanol, propanol, ethylene glycol, glycerol, acetic acid, methyl formate, methyl acetate, dimethyl ether, acetaldehyde, methylethyl ketone, and the like.

#Natural gas and liquid petroleum gas typically contain odorants such that leaks can be detected. Odorants conventionally used are one or more organosulfur compounds such as organosulfides, e.g., dimethyl sulfide, diethyl sulfide, and methyl ethyl sulfide; mercaptans, e.g., methyl mercaptan, ethyl mercaptan, and t-butyl mercaptan; thiophenes of which tetrahydrothiophene is the most common; and the like. The amount used can vary widely. For natural gas, the organosulfur component is often in the range of about 1 to 20 parts per million by volume (ppmv); and for LPG a greater amount of sulfur compounds are typically used, e.g., from about 10 to 200 ppmv. It is not unusual for commercially obtained hydrocarbon feeds to contain also other sulfur compounds that may be natural impurities such as hydrogen sulfide and carbonyl sulfide. Carbonyl sulfide concentrations in natural gas and LPG of 0.1 to 5 ppmv are not unusual.