Question

Question C2: (8+ 4+ 4 = 16 marks) - Most Australian electricity is produced from coal. Victoria uses brown coal brown coal. Most other states use higher rank bituminous coals. These coal-fired power stations rely on pulverized fuel combustion in boilers to generate this electricity (via steam turbines) in a relatively inefficient way Briefly describe the major organic inputs, sedimentary processes and transformational changes that led to these coals. Also, make use of a vanKrevelen diagram to indicatively illustrate the chemical changes that have occurred over time as well as the current composition (ie, the location on the vanKrevelen diagram) of these coals (a) Identify and describe two specific technologies by which the efficiency of power generation (b) from coal could be significantly improved Identify and describe two key advantages and two key disadvantages of 'clean coal' as a fuel (c) for the future.

Answer 1

Answer:

a) Brown coal is an alternative term for lignite, which is usually a lower rank coal. It begins forming when partially decayed plant matter, which is called peat, gets accumulated. Depending on local geothermal gradient, tectonic setting and increasing pressure, burial of sediments continues which further increases temperature. By this process, water content and volatile matter gets removed from the coal and lignite forms. This coal gets transformed into bituminous in case of deeper burial, which causes more removal of liquid and volatile matter.

b) Technologies which can be used to improve the efficiency of power generation from coal in a thermal plant are:

1. Increasing the average temperature of heat addition to the thermal cycle.

2. Increasing the inlet pressure of the steam.

c) Advantages of clean coal:

1. Using clean coal is economically very sustainable and it supplies abundant energy, which, in turn, generates huge amount of power. So, significant amount of power can be generated at a low cost.

2. As it can be made low carbon with scrubbers, when turned to liquid or gas, it burns cleaner.

Disadvantages of clean coal:

1. Nonetheless, clean coal is not carbon free. And so, it too generates carbon dioxide.

2. Other hazards include pollution around mining areas and plants, radiation and other risks.