The Maximum Economy Smidth/Parsons Preheater

Lime has been produced for many centuries. The simple pot kiln was one of the first devices used in this process. It was constructed of stone often on the side of a hill to reduce construction efforts and provide easy access to the top for feeding of limestone. It was fired from below with wood and coal. The pot kiln was very small and operated on the batch principle. The kiln being cooled between each batch, the fuel consumption was horrendous. The lime quality was poor with perhaps only one half of a batch being lime of suitable quality. Of the remaining half one part would be over burned and another part underburned. For centuries the lime burning technique was improved at a barely recognizable rate. One of the first major steps forward was the introduction of the continuous process vertical lime kiln. Although at first crudely constructed, the kiln had a refractory lining. It was charged with alternate layers of limestone and solid fuel usually in the form of coke. Continuous mode of operation, larger unit size and better heat distribution resulted in greatly improved fuel economy. However, quality of lime produced still left much to be desired. One problem was contamination by ashes from solid fuel.