Cement and plasmaFound this on plasma and the cement industry....
Few days ago, when I was reading the prestige Global Cement Magazine of June 2020, I found some great news that they could revolutionize the cement industry: the use of Hydrogen and Plasma energy to replace the fossil fuels!
The MPA (Mineral Products Association) secured a Euro 6.8 million, UK government grant in February 2020 to trial hydrogen and plasma technology in the production of cement and lime.
This follow a feasibility study made in 2019 that found a combination of 70% biomass, 20% hydrogen and 10% plasma energy could be used to eliminate fossil fuel-derived CO2 emissions from cement making. The trials of hydrogen and biomass respectively will take place on sites operated by Tarmac Cement & Lime (Tunstead) and Hanson Cement (Ribblesdale).
Using a mix of 50% hydrogen and 50% biomass in the Kiln and 83.3% biomass with 16.7% plasma in the Calciner, leads to total elimination of all fossil fuel CO2, leaving only process CO2 from the breakdown of raw materials and CO2 from biomass fuels.
The mentioned study indicates that the elimination of fossil fuel CO2 should be possible with no negative impact on clinker quality, kiln stability or build-up issues but some further work through trials is necessary required to verify :
- That the kiln burner could manage the Hydrogen together with the Biomass without produce damage in the refractory.
- Biomass fuel design is such that larger chips do not fall into the bed and negatively affect clinker quality.
- The location of plasma injection in relation to the hot meal and biomass inlets needs to be investigated further.
If these issues could be addressed and overcome through the demonstration project, fuel switching would become a key part of the transition to net zero cement production:
The manufacture of cement is an energy and CO2 intensive process with around 70% of total emissions arising from the chemical decomposition of limestone (process emissions) and only 30% from the combustion of fuels (combustion emissions). The split varies from plant to plant and country to country mainly based in the fuel characteristics.
Considerable progress has already been made in reducing emissions in UK cement manufacture through investment in more efficient plant and fuel switching to biomass fuels. In 2018 a wide range of waste biomass and part biomass fuels contributed 17% to the total thermal input. Higher levels of waste derived fuel use have been possible (even 100% for short periods) but significantly higher use of biomass has not yet been tested.
Hydrogen
If large volumes of hydrogen can be produced using low carbon methods (e.g. using renewable electricity) it may be an option for cement manufacturers. However, it has never been tested so it is unknown how it might impact on cement manufacturing process.
The nature of hydrogen and natural gas combustion is quite similar. The main differences are the radiation properties of a hydrogen flame and the flame size, which is smaller in hydrogen combustion. Nevertheless, the burning process and the heat formation are still different . Technically, due to its highly flammable characteristics, safety precautions must be taken to avoid dangers that may arise from hydrogen usage. (for example to the refractory)
The change of the clinker burning process into hydrogen combustion could be possible. It certainly needs further research in order to adopt the system, modify the conventional equipment and update the process parameters.
PLASMA
Thermal plasma torches are distinguished by high temperature and enthalpy and therefore offer an attractive option for introduction in the cement industry, which has never used before this technology.
The plasma power density is especially high, as much as 100 times higher than conventional furnaces.
The Plasma production cost in an electrified process is expected to be double that of today’s technology but could remain competitive when compared to other options for the radical emission reduction.
The future potential of a wider application of plasma techniques in industry depends on improvement of the characteristics of plasma torches. The biggest challenge to overcome is extension of the lifetime of the anode and cathode.
BIOMASS
Biomass based fuels have been used in the European cement industry for many years and their usage, in combination with conventional fuels or other alternative fuels, can be considered state of the art, availability and economic viability provided.
The most widely used, sewage sludge and meat and bone meal is considered almost 100% CO2-neutral. Other alternative fuels such as industrial or domestic wastes contain varying proportions of biomass (10% to 50%).
While high shares of up to 100% alternative fuels covering the thermal energy demand can be achieved during normal cement plant operation, a usage of 70% to possibly more than 80% of pure biomass fuels needs further investigation.
Key challenge for Cement Industry is that fuel switching alone will not result in full de carbonisation because process emissions will remain. CCUS (Carbon Capture, Use and Storage) is more likely the answer, but still requires tested at the industrial scale in cement production. Fuel switching is advantageous to consider now! and UK is moving up, we will waiting for the results because a lot of projects could be triggered allowing us to be closer to the Zero CO2 Emissions Goal!