Hydrocarbon Emissions from Cement Kilns Burning Hazardous Waste

Abstract

As a result of the Boiler and Industrial Furnace Regulations (BIF) many cement manufacturers must address the issue of carbon monoxide (CO) and hydrocarbon (HC) emissions that are greater than the regulatory levels of 100 ppm and 20 ppm respectively (corrected to 7% oxygen). EPA's intent of limiting these emissions at the above levels was to provide an indication of the combustion efficiency of the BIF unit when burning hazardous waste.[1] The cement manufacturing process has the potential, however, to produce CO and, in some cases, HC byproducts during the normal chemical reactions that occur as the raw materials are processed into clinker. The purpose of the study described in this paper is as follows: 1) to demonstrate that the source of elevated CO and HC emissions from a wet process cement kiln is the raw materials, and 2) to determine a relationship between operating parameters and the emission rate of CO and HC which is capable of being used to either control the emissions or to determine their source at any given time from poor combustion. Observations have indicated the presence of unique combustion conditions in the kiln related to the natural organic constituents in the raw materials. The trends exhibited by test results indicate the existence of two modes of combustion in the kiln; one related to fuel and one related to the raw materials. The characteristics of the HC, CO and operating parameters relationships, rather than the emission rates themselves, have the potential to identify the existence of poor combustion conditions.