Continuous flue gas emission monitoring for cement kiln control

Like many other established industries, cement manufacture has undergone many changes in recent years. Since the 1940´s the main emphasis has been on product throughput with fuel considerations being secondary and emission control being solely based on particulates. This mode of operation continued until fuel prices soared in the 1970´s. Increased running costs, with a more competitive market for cement, led to operational changes in the way in which cement kilns were run with a greater use of dry processes. Expensive oil fired kilns were modified to run on coal. Petcoke was introduced and blended with coal, this having the advantage of being of a similar calorific value to coal but significantly cheaper. This coal/petcoke mixture has been the dominant fuel used to fire cement kilns ever since. More recently, however, the industry has been compelled to include another operating constraint, the gaseous emissions from the cement making process. The control of gaseous emissions is a field very much in its infancy; indeed the reliable measurement of prescribed emissions, vital for any control scheme, is presently far from ideal. The Environmental Protection Act 1990 demands the monitoring of all emissions from cement processes, however this paper concentrates on one of these problems, that is the monitoring of flue gas emissions, in particular oxides of nitrogen and oxides of sulphur