polysius® pure oxyfuel
A gateway to climate neutral cement
The paradigm shift within the cement industry towards climate neutrality and more sustainable cement plants is almost palpable. Sustainability is not merely a buzzword or a trend. At this point in time, it is a necessity and one of the key challenges of our time – globally and in the cement industry.
The carbon footprint of the cement industry
During cement manufacturing large quantities of carbon dioxide (CO2) are emitted. Only one third of these CO2 emissions result from the combustion of fossil fuels, such as coal or pet coke, whereas the largest portion is released by limestone decomposition. Limestone – the most important feedstock for cement production – consists of approx. 35 % to 44 % CO2, depending on its quality.
Our experts from the thyssenkrupp Cement Technology Research Center have made it their goal to reduce the emission of greenhouse gases such as CO2 significantly. To do so, they have developed the oxyfuel technology.
How polysius® pure oxyfuel drives climate neutrality within the cement industry
The basic principle behind oxyfuel is the capturing of CO2 from the exhaust gas of cement manufacturing plants and hindering it to get into the atmosphere. Easier said than done: The contains of the offgas have to be modified in order to capture almost 100% of the cement plant’s total CO2 emissions. This is achieved by using pure oxygen instead of combustion air. This way, the exhaust gas consists mainly of CO2.
Now and then: the new and improved polysius® pure oxyfuel
Before existing plants could be converted to the oxyfuel technology, but because of the necessary exhaust gas recirculation system, plant owners faced high investment and operating costs and a reduced CO2 capture rate.
To operate a cement factory as an oxyfuel plant, pure oxygen is required in a first step. According to the state of the art, this pure oxygen can be produced in a cryogenic air separation unit. In the place of air, oxygen is used as coolant in the clinker cooler and - after heating up - it is fed to the firing system of the clinker production. As no more nitrogen - contained in the air - is supplied to the pyro-processing system, the gas volume in the plant is reduced accordingly. To avoid this, existing plants converted to oxyfuel technology are provided with an exhaust gas feedback system.
The new and improved polysius® pure oxyfuel process is based on pure oxygen as combustion gas and does not require a costly and complex exhaust gas recirculation. Here pure oxygen is fed to the foremost zone of the clinker cooler and routed to the clinkering zone burner. Other than in today's plants, the whole oxygen is fed to the clinkering zone burner. A combustion air bypass for the kiln inlet firing, the so-called tertiary air duct, is dispensed with. This approach ensures that the clinkering zone burner is supplied with an adequate gas volume and that overheating is avoided.