Solar coal-gasification reactor with pyrolysis-gas recycle. [Patent application]

Coal (or other carbonaceous matter, such as biomass) is converted into a product gas that is substantially free from hydrocarbons. The coal is fed into a solar reactor, and solar energy is directed into the reactor onto coal char, creating a gasification front and a pyrolysis front. A gasification zone is produced well above the coal level within the reactor. A pyrolysis zone is produced immediately above the coal level. Steam, injected into the reactor adjacent to the gasification zone, reacts with char to generate product gases. Solar energy supplies the energy for the endothermic steam-char reaction. The hot product gases flow from the gasification zone to the pyrolysis zone to generate hot char. Gases are withdrawn from the pyrolysis zone and reinjected into the region of the reactor adjacent the gasification zone. This eliminates hydrocarbons in the gas by steam reformation on the hot char. The product gas is withdrawn from a region of the reactor between the gasification zone and the pyrolysis zone. The product gas will be free of tar and other hydrocarbons, and thus be suitable for use in many processes