Abstract
In this work, the environmental impact assessment is prepared for three different flue gas desulphurization (FGD) processes: (1) intra-furnace sulphur removal during coal combustion with limestone addition, (2) FGD with wet lime scrubbing, (3) regenerative copper oxide flue gas clean-up process. The evaluation and ranking of the three processes according to their environmental impacts is completed for the treatment of as much flue gas that contains 1 kg sulphur. The assessment of the environmental impacts is carried out with the Eco-indicator 99 life cycle impact assessment methodology based on life cycle inventories collected from existing coal fuelled power plants. The environmental assessment is prepared for three different scenarios according to degree of the utilization of the by-products obtained during the desulphurization: (1) zero utilization, (2) full utilization, (3) utilization according to industrial statistics. The results show that all the three investigated FGD processes have about 80% lower environmental impact than the uncontrolled release of sulphur oxides into air. Intra-furnace limestone addition and wet scrubbing processes use similar principal of physical chemistry and they have similar environmental indices. The basis of the regenerative process is a sorption/reduction/oxidation cycle that has higher SO2 removal efficiency than the two other processes. This higher efficiency results in a significantly lower environmental impact.
Highlights
Coal plays a significant role in the generation of electricity
According to Eco-indicator 99 life cycle impact assessment methodology (EI-99), the simple release of SO2 into air causes 2.32 EI-99 points/kg sulphur damage to the environment. This shows the reasonability of the flue gas treatment: at least 80% reduction in the environmental impacts can be achieved by the application of flue gas desulphurization
Total environmental impacts of the atmospheric circulating fluidized bed combustor (ACFBC) process are signed by 0.467 EI-99 points referring to the functional unit, if 0% utilization is considered
Summary
Coal plays a significant role in the generation of electricity. In 2003, about 110,000 TWh primary energy was consumed worldwide and, on a global basis, coal-fired processes provided about 26% of the net electricity generated [1]. Techniques for reducing emissions of SO2 during the combustion of fossil fuels can be distinguished as (1) precombustion, (2) intra-furnace sulphur removal, (3) and end-ofpipe abatement technologies (flue gas desulphurization). Precombustion sulphur removal includes a wide range of technologies, i.e. microbial desulphurization, halogenation, pyrolysis, electrochemical oxidation, irradiation [5], liquid phase methanol process and coal gasification [6]. Intra-furnace sulphur removal is generally done in circulating fluidized bed boilers allowing higher residence time for the sorbent particles. These processes have inherent environmental benefits over end-of-pipe flue gas desulphurization (FGD) processes, since there is no need for expensive FGD equipment; the retrofitting of an existing boiler is difficult and it might require a new apparatus
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