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10 %– 20 % saving on the 350 million tonnes of fuel the industry consumes per annum, the collective cost saving is vast.”
Fuel game-changer for European cement producers
Some cement kilns in Europe substitute 100 % of their fossil fuels with RDF, specifically during the substituting fossil fuels at the pre-calciner.
“ Examples exist where producers rely solely on alternative fuels as energy supply. This is indicative of the maturity of the mindset of the European recycling market, but also highlights the technological advancement of the cement plants.”
Cement kilns that aim to operate fully on alternative fuels need to undergo significant process conversions and systemic changes, which demand upfront capital investment.
Another legislative incentive— carbon taxes— makes it lucrative for European producers to invest this capital upfront. In South Africa, the green economy lags behind, with the carbon tax bill still in draft form.
In addition to capital outlay, a second consideration for cement producers is the metallurgical impact of RDF on clinker.
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Standard to cement production, different types of fuel applications exist between the pre-calciner and main burner processes. The main burner uses a smaller-sized waste fraction because it has a shorter residence time as a result of higher temperatures. In the pre-calciner phase, temperatures are lower, the residence time longer, and the plant uses larger fuel particles. RDF is therefore more suitable for pre-calcising, however it can be shredded to the size fraction required for use in the main burner.
Processing impacts
From a process perspective, the use of a waste-generated fuel source adds alternative challenges and opportunities to clinker production.
“ Some studies have indicated the application of RDF as a better combustible material or fuel source than coal,” says Young.
Controlling your RDF feed rate is critical for maintaining stable temperatures inside the kiln. Because RDF is a new fuel source with unpredictable combustion patterns— at least when compared to tried-and-tested coal— automated time adjustment of
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A solid recovered fuel in the form of extruded logs. |
Interwaste |