Digestion of liq. waste producing methane and dried sludge - employs steam from drying sludge to heat liq. in digester

摘要

The digestion temp. is kept above ambient by input of heat from an external source. Sludge from the digester is partially dehydrated e.g. by filter press, and then heated in a dryer which evaporates water, producing steam. The steam so produced is used to provide the heat input required in the digester vessel. The steam can be directly injected into the liq. in the digester or in a recycling circuit associated with the digester. Alternatively, the steam can be passed through an indirect heat exchanger to transfer heat to processed liq. either inside the digester vessel or in an external recycling circuit. This is an anaerobic digestion process and installation in which liq. organic waste is fermented to produce a fuel gas and a residual sludge which is dried for use as agricultural fertiliser.