Changing the fuel mix
One of the possible ways to reduce our emissions is switching to less carbon intensive fuels sources, such as natural gas, or increase the use of biomass or waste materials. However, many factors have to be taken into account when selecting the right fuel source.
Use of gas instead of solid fossil fuels
The European lime industry currently uses natural gas for about one third of its energy needs. Switching from solid fossil fuels to natural gas would reduce the CO2 intensity of lime production although the gas network may be a concern, given the location of our plants.
Within the framework of this exercise, we assumed that all solid fuels used today would be replaced by natural gas. This can potentially reduce the average emission factor of the fuel mix by 30%.
This switch is dependent on a steady, secure and affordable supply of natural gas and will be affected by a series of external factors, such as potential price hikes caused by a switch to natural gas by the power sector or, inversely, lower gas prices, as European unconventional gas becomes available.
Use of waste as a fuel
Certain types of lime kilns are suited for the use of waste as a fuel source. The European lime industry is committed to remaining an important factor in the circular economy. The use of waste as a fuel source will continue but is conditional upon the availability of the right kind of waste and a regulatory environment that permits the use of waste as a fuel.
Use of biomass as fuel
Different forms of biomass can be used as a fuel in kilns. There are some technical restrictions, especially in the fuel efficient vertical kilns, as to the type of biomass that can be used, but ongoing innovation could ensure biomass will remain a fuel source of the European lime industry.
One of the ways to overcome the difficulties using biomass would be to convert it to syngas first. Using similar technology kilns could even be fuelled by biogas, sewage gas or landfill gas.
Use of electricity to heat kilns
Electricity could theoretically be used in the future to heat kilns. The European Commission’s Energy Roadmap plans a total decarbonisation of power, so this would result in a substantial reduction of our emissions. However, with current and foreseen power prices, this option is not economically viable. Moreover, this option is not yet technically feasible for the moment and will require further R&D.
However, the situation would be different in times of oversupply of electricity, resulting in cheap or even free electricity. Using electricity to heat the kilns might then be feasible and could help to bring supply and demand in equilibrium.
Solar heat could potentially be used, in some countries, to heat the kilns but they have to be heated to at least 900°C. In the future, high-temperature Central Receiver Systems (CRS) with pressurised air could reach temperatures up to 1000°C. However, this technology is still in an experimental phase, would require further research, and is only suitable for Southern Europe.
This is an extract from the report 'A Competitive and Efficient Lime Industry' published by the European Lime Association.
Read the article online at: https://www.worldcement.com/europe-cis/22122014/a-competitive-and-efficient-lime-industry-part-two-57/