(36a) Techno-Economic Analysis of the Effects of Biomass Co-Firing and Clc Oxygen Carriers on the Performance of Coal Based IGCC Power Plant

The global demand for energy is constantly growing due to the population and economy growth, especially in emerging market economies. Fossil fuels still produce most of global energy with coal being the most abundant fossil fuel. The use of coal has shown an increase over time, which resulted in an increase in carbon dioxide emissions. Even with the rise in the global awareness about the negative effects caused by greenhouse gases, the abundance and the low cost of coal still ensures the existence of coal-fired power plants.

This research the potential of retrofitting integrated gasification combined cycle (IGCC) power plants with biomass co-firing and chemical looping combustion (CLC) carbon capture for near zero carbon emissions. The investigated biomasses are lignin; palm coir, palm empty bunch and palm leaflets (agrowastes in UAE). The effect of different biomass co-firing and CLC oxygen carrier on the techno-economic performance of coal-based IGCC power plants was modelled and simulated using Aspen Plus software.

The results showed that the use of iron oxide as an oxygen carrier better performance than the traditional oxygen carrier of nickel oxide in terms of total plant efficiency, total plant energy output and carbon specific emissions. However, to achieve near zero carbon emissions, the flow rate of the oxygen carriers was 15 times the flow rate of the feed.

Increasing the percentage of lignin and palm coir co-firing resulted in better performance regardless of the used oxygen carrier. However, the performance has diminished when the percentage of palm empty bunch and palm leaflets co-firing increased. One of the major drawbacks of biomass co-firing is the particulate matter that remains. The presence of particulate matter results in downstream equipment fouling and hence, lowering the overall power plant efficiency. This issue has been addressed by adding cyclones to the syngas cleaning section.

The use of CLC for carbon capture has increased the cost of power production and the increase depended on the type of oxygen carrier. The cost of power production has increased by 32% when iron oxide was used, whilst the cost has increased by 45% when nickel oxide. However, there was no clear trend to indicate if increasing biomass co-firing percentage will either increase or decrease the cost of power production. Unfortunately, the lowest cost was greater than actual market trading prices. Therefore, currently no clear economic drive for developing coal biomass co-firing power plants with CLC carbon capture technology.

Despite everything, a satisfactory coal and biomass co-firing power plant with suitable decarbonisation scenario might be economically feasible, depending on a trade-off between the decarbonisation degree and CO₂ specific emissions. All that will be driven by the introduction of new national/international legislation regarding allowable carbon emissions from coal-fired power plants.