Patent Application
20080021120
For a more complete understanding of the present invention, reference is now made to the following description taken in conjunction with the accompanying drawing, in which:
Referring to
In another embodiment, the hydrogen is fed directly to the fluidized bed reactor 24 at a point below the slurry of carbonaceous material while the feed from the steam generator is introduced at a point above the input of the slurry of carbonaceous material, i.e., downstream of the point of introduction of the carbonaceous material.
The fluidized bed reactor 18 operates as a steam hydro-gasification reactor (SHR) at a temperature of about 790° C. to about 850° C. and pressure about 132 psi to 560 psi to generate a stream of methane and carbon monoxide rich gas, which can also be called a producer gas. The chemical reactions taking place in this process are described in detail in Norbeck et al. U.S. patent application Ser. No. 10/911,348 (published as US 2005/0032920), entitled: “Steam Pyrolysis As A Process to Enhance The Hydro-Gasification of Carbonaceous Material.” The disclosure of U.S. patent application Ser. No. 10/911,348 is incorporated herein by reference.
The ash slagging temperature in the fluidized bed reactor 24 is sufficiently low and the pressure sufficiently high that a fluidized bed reaction can be use. The reducing environment of fluidized bed reactor 24 also suppresses tar formation.
Ash and char, as well as hydrogen sulfide and other inorganic components from the fluidized bed reactor 18 are disposed of through line 26 and its output is fed through line 28 into a heated cyclone 30 which separates out fine particles at 32. The output from the heated cyclone 30 is fed through line 34 to a hot gas filter 36, then through line 38 to a steam methane reactor 40.
At the steam methane reformer 40, synthesis gas is generated comprising hydrogen and carbon monoxide at a H2:CO mole ratio range of about 3 to 1. The hydrogen/carbon monoxide output of the steam methane reformer 40 can be used for a variety of purposes, one of which is as feed to a Fischer-Tropsch reactor 42 from which pure water 44 and diesel fuel and/or wax 46. Exothermic heat 48 from the Fischer-Tropsch reactor 42 can be transferred to the steam methane reformer 40 as shown by line 50.
The required H2:CO mole ratio of a Fischer-Tropsch reactor with a cobalt based catalyst is 2:1. Accordingly, there is an excess of hydrogen from the steam methane reformer 40, which can be separated and fed into the fluidized bed reactor 24 (by lines not shown) to make a self-sustainable process, i.e., without requiring an external hydrogen feed.
Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process and apparatus described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes and apparatuses, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include such processes and use of such apparatuses within their scope.
