Quench Water Moderator
Publication Date: 2003-Sep-19
The IP.com Prior Art Database
This invention uses black water generated by the quenching of syngas in a gasification reactor as a temperature moderator in the gasification reactor. The black water is pumped up to the gasifier feed pressure and filtered to remove any particles that could damage the feed injector to the gasifier. The black water is then heated with steam, and mixed with the solid carbonaceous fuel prior to the fuel being introduced into the gasification reactor.
BACKGROUND OF THE INVENTION
High pressure, high temperature gasification systems have been used to partially oxidize solid carbonaceous fuels to recover useful by-products or energy in a gasification reactor, or gasifier. Generally, solid carbonaceous fuels will need to be liquefied with oil or water prior to being fed to the gasifier. The solid fuels can be admixed with water to form an aqueous feedstock that is fed to the reaction zone of a partial oxidation gasifier along with a oxygen containing gas, such as air, pure oxygen or enriched oxygen, and a temperature moderator, usually steam.
The partial oxidation reaction is preferably carried out in a free-flow, unpacked non-catalytic gas generator. Under high temperature and high pressure conditions, about 90% to 99%, typically 93% to 97%, of the hydrocarbonaceous feedstock can be converted to a synthesis gas containing carbon monoxide and hydrogen, also referred to as syngas. Carbon dioxide and water are also formed in small amounts. This leaves a small portion of the feed that does not get converted into syngas.
Water is further used as quench water to quench the temperature of the syngas exiting the gasifier. Because some of the feed does not get converted into syngas, the quench water also captures this unconverted feed and scrubs other particulate matter from the syngas. The quench water also cools and/or conveys the particulate waste solids, such as ash, slag and unconverted feed out of the gasifier. The water is normally continuously removed from the gasifier as an aqueous effluent, grey water, purge wastewater or blowdown stream to prevent excessive buildup of solid materials and undesired dissolved solids.
The grey water blowdown stream is discharged from the gasification system, and is treated with chemicals to precipitate and separate solid impurities from the grey water. After having the solids removed, the grey water can be subjected to ammonia stripping, biological treatment, or evaporation to produce a dry salt for commercial marketing and a distillate water. The water can then be recycled to the gasification quench process, thereby minimizing the wastewater discharge from the gasification plant.
Solid materials, such as ash, slag and/or unconverted carbon from the feed, usually accumulates in the bottom of the gasification reactor. Occasionally the solid materials will have to be removed from the gasification reactor so as to prevent an excess buildup of these solid materials in the reactor. This is usually done through a lock hopper system, wherein the solid materials can be removed from the gasification reactor without having to shut the reactor down. These solid materials are carried out of the reactor using some of the quench water. This water that contains the solid materials is called black water. After the solid materials are removed, the solids are usually sent to a filter press where the water is separated from the solid materials. The solid m...