Organic Waste Recycling

Biofuels production 187

Remedy Painting of the gas holder with black paint or even coal tar each year. Alternate materials like PVC, ferrocement, galvanized iron, fiberglass, etc. may be used for manufacturing the holder. 1. Should be washed or flushed regularly with clean water or should be cleaned with a pole moving up and down. 2. Replacement (as it is mostly beyond repair). Condensate should be blown out 2-3 times a week. The pipe may be kept at a slope to ease blowing off.

Possible cause Gas holders, commonly made of mild steel, remain in contact with digester slurry and with the gas containing methane and other gases, including H

S which 2

is highly corrosive. 1. Accumulation of feed or scum. 2. Rusting Presence of water vapors in the gas.

Problem 1. Corrosion of the gas holder. 1. Clogging of the inlet/outlet pipes. 2. Breakdown of central guide pipe. 1. Collection of condensate.

Gas holder Inlet and outlet and central guide pipes Gas pipe carrying gas to the utilities
Table 4.18 Problems with the digester, gas holder, and pipes (adapted from Tata Energy Research Institute 1982) (continued)