Graphical Analysis of Gasification Processes

Gasification processes incorporate many reactions that are fairly complex to analyse making their design difficult. In this chapter it is shown that general gasification systems are limited by consideration of mass and energy balances only. Here, a ternary Carbon-Hydrogen-Oxygen diagram is developed to represent gasification processes. The diagram incorporates basic chemistry and thermodynamics to define a region in which gasification occurs. The techniques are further validated from data obtained from pilot or laboratory experiments available in literature. In this chapter we develop graphical representation for sawdust gasification and underground coal gasification (UCG), a clean coal technology. The methods described allow for further analysis without considerations to thermodynamic equilibrium, reactor kinetics, reactor design and operation. This analysis is thus an indispensable tool for flowsheet development using gasification and an excellent tool for practitioners to rapidly understand gasification processes.

Design of the Otjikoto Gold Mill, Namibia

The Otjikoto Gold Mine in the Republic of Namibia is located approximately 300 kilometers north of the capital city of Windhoek. The project features surface mining with a modern gravity/carbon-in-pulp mill for ore treatment and recovery of gold. Initial mill design capacity was 2.5 million tonne per annum but then expanded after 9 months of operation to 3.1 million tonne per annum. The technical steps to establish the Otjikoto mill design from process selection in the due diligence stage, through flowsheet development in the feasibility study followed by detailed engineering design are reviewed in this paper along with mill performance during start-up and in 2019.