What is “Oxygen Enrichment Technology”?

By: Nael Shabana qatar.cement@yahoo.com

It is an oxygen injection system connects to kiln burner or precalciner burner to enhance the combustion of the fuel. In general, the use of oxygen enriched combustion air in the clinker burning process allows an increase of the energy efficiency, production capacity or substitution of fossil fuels by low calorific value or (secondary) fuels and that way the specific CO2 emissions can be reduced.

By the use of additional oxygen the nitrogen fraction of the combustion gas is decreased, which has to be heated up in the case of combustion with ambient air. Therefore the adiabatic flame temperature rises and the flame becomes shorter and brighter. The measure is limited by increasing damages of the kiln refractory and higher NOX emissions due to increasing thermal NOX formation in the sintering zone. In practice the application of the oxygen enrichment is still at an early stage, meaning that the technology contains potential for further optimization with respect to NOx emission reduction. Due to reduced secondary air flow the heat recuperation in the clinker cooler might be affected for example with a higher secondary air temperature as well.

The oxygen enrichment technology is established in some cement plants in order to improve production capacity. An increase of 25% to 50% (short term experiments) kiln capacity by oxygen enrichment to 30-35 vol.% in the combustion air has been reported. Oxygen enrichment has not been applied to reduce CO2 emissions so far. But the use of enriched combustion air may result in fuel savings and thereby avoids CO2 production. The decision for a dedicated oxygen supply system (on-site/off-site) depends on the specific need of the cement plant. Oxygen production itself leads to comparatively high additional power consumption.

Surely; there are a number of plants using oxygen enrichment technique but still not commercially due to its high cost. If market demand exists with good prices for cement then oxygen enrichment can be a good option. Table-1 shows a number of kilns in the USA using oxygen enrichment of either the main burner or the precalciner.