ABSTRACT
This chapter focuses on reactor configuration and conditions for the anaerobic conversion of solubilized lignite feedstock into methane. Reactor costs are likely to influence process economics significantly; thus an evaluation of reactor design for the lignite conversion process is warranted. The most common methane-producing anaerobic process, the digester, processes concentrated solids from primary and secondary waste treatment clarifiers, usually raw suspended matter and excess cell mass, respectively. Essentially a large, open reactor, the digester's simple design makes it a candidate for solubilized lignite conversion in the salt dome location. Despite its simplicity, the digester has shortcomings that make questionable its suitability for solubilized lignite conversion. Conventional digesters lack provision for retaining microorganisms in the system longer than the hydraulic residence time. While lignite hydrolysis can produce high chemical oxygen demand (COD) concentration (consistent with digester treatment), filtration and ultrafiltration tests indicate that the biodegradable COD represents mostly soluble materials.
