Reusing waste-fuel gases to generate energy not only provides a viable alternative power source but also an opportunity to reduce air pollution, states industrial and speciality gas company Air Products.
The company has developed methods to save energy, reduce pollution and lower costs by using oxygen enrichment in cement kilns and cryogenics in rubber recycling processes.
Air Products bulk gases sales manager Sachin Kulkarni says the evolution of oxygen enrichment for cement kilns and cryogenics for rubber recycling is extremely beneficial to industry.
“Oxygen enrichment evolved when cement producers sought alternative fuels to expend- able and nonrenewable natural resources, such as coke, coal and rubber, for use in cement kilns.
“The fumes that resulted from heating these substances in kilns using traditional methods, were considered detrimental to the environment and humans,” he says.
In the late 1980s, oxygen enrichment was adopted as a suitable method of achieving full combustion when reusing rubber as a fuel in cement kilns.
Oxygen enrichment allows high temperatures to be reached very quickly, which greatly reduces emissions, while also producing the required amount of heat for the cement manufacturing process.
While oxygen enrichment is now commonly used in cement kilns that use recycled rubber as a fuel, Air Products’s burner system has developed to such an extent that the design allows for complete process stabilisation and increased output.
“Operational teams require a stable kiln operation, as the stability of the kiln can, over time, contribute to higher production volumes. The burner design and system provide shorter flames and better control of the burning zone, which assists in stabilising processes,” says Kulkarni.
He points out that companies that adopt the oxygen-enrichment methodology will require an oxygen burner, an oxygen flow meter and nitrogen oxide monitoring equipment, which monitors flue gases to adequately decrease or increase the oxygen flow.
The system not only reduces the carbon footprint but also increases the production of clinker by between 5% and 30%. Documented results also include a 30% to 80% increase in the use of alternative fuels.
Beyond its expertise in the field of oxygen enrichment for cement kilns, Air Products also provides products for the cryogenic recycling of rubber.
Kulkarni explains that the cryogenic recycling of rubber was one of the early technologies that was considered as a means to counter the impact the industry was having on the environment and to find alternatives for the use of nonrenewable resources.
Cryogenics refers to the science and technology of producing a low-temperature environment for applications.
As the demand for more finely ground recycled rubber had increased, the incentive to find more productive and economical ways of achieving alternative uses for nonrenewable resources gained momentum.
The application of cryogenic principles to the handling of the rubber has resulted in the form of the rubber being altered, which makes it brittle and easy to break and grind.
The first step in the process is the removal of foreign objects, such as wire and nylon, from rubber tyres and other waste rubber.
Thereafter, the rubber is chopped into manageable chunks and placed on a sealed system conveyor. Liquid nitrogen is then sprayed on the rubber until it reaches glass transition temperature levels. At this stage, the rubber can be removed for fine grinding.
The powder can then be used as an additive by tyre manufacturers and rubber parts suppliers, as well as for the manufacture of sound- absorbent rubber mats for use at airports.
Cryogenic technology, in this application, increases the use of waste products and reduces the negative impact on the environment.
Air Products is keen to invest in research and development that will enable it to offer its customers the most operationally effective solutions that will help the customer increase cost competitiveness in the industry and markets they serve.
Research on waste fuels has been done in Allentown, in the US. A Solid Fuel Laboratory has been installed to conduct tests on various fuels and associate burners.