Global survey on lime kiln operation, energy consumption, and alternative fuel usage

In late 2008, a survey on lime kiln operation and fuel usage was conducted through questionnaires distributed to pulp mills in nine countries. Responses were received from 59 pulp mills, totaling 67 lime kilns. This paper discusses the key findings from the survey with respect to kiln design parameters, operating data, control strategies, fuel types, energy consumption, and operating issues. Where possible, comparisons were made with findings obtained from a similar survey conducted in 1991. Over the past two decades many improvements have been made in kiln design and operation. Included are a larger number of kilns equipped with product coolers and lime mud dryers, along with changes designed to deliver higher mud dry solids content to the kiln. However, ring formation and dusting/high dust load remain the major operational issues among the respondents. Although few kilns have used alternative fuels to date, there is considerable industry interest in their use in the future. About two-thirds of the kilns have plans for implementing alternative fuels within the next five years.