Biogas Plants (GTZ, 1988, 85 p.) (introduction...) Acknowledgements Preface 0. Biogas as appropriate technology 1. Benefits and costs of a biogas plant 2. The dgestion process 3. Biogas plants 4. Scaling of biogas plants 5. Design of biogas plants 6. Biogas utilization 7. Planning, design and construction 8. Appendix Bibliography

Fig. 53: Units of measurement

Cubic metres and cubic feet; powers of ten

Fig. 54: Cubic metres and cubic feet; powers of ten

Fundamental geometric formulae

Fig. 55: Fundamental geometric formulae

Fundamental static formulae

Fig. 56: Fundamental static formulae Static calculations are not usually necessary for small, simple biogas plants. For larger plants, a rough calculation should be carried out to determine whether the loads and stresses are likely to be high enough for an exact calculation to be necessary. Spherical and conical shells are complicated forms. They are very difficult to estimate by rough calculation. As a rule, only the edges are loaded to the permissible limit.

Water pressure and earth pressure

Fig. 57: Water pressure and earth pressure Water pressure depends directly on height. The amount of water has no effect on the pressure. The earth pressure depends on height, the angle of repose (alfa) and density (ro) of the earth. In the table, (a) is soft loam or clayey sand, (b) is pure sand and (c) is marl or murrum.

Change in volume of ideal gases under pressure and temperature

Fig. 58: Change in volume of ideal gases under pressure and temperature

Cross sections of common steels and pipes

Fig. 59: Cross sections of common steels and pipes