Abstract

The calcination principle of composite firing shaft kiln is: mix the solid fuel (coke or anthracite) with qualified stone evenly, use rotary discharging device equipped on kiln roof to discharge the mixture into the kiln, then under its own gravity the mixture proceeds through preheating area, calcining area, cooling area, and finally calcined into qualified finished lime product. In calcining area, the heat produced by the coke and anthracite of the preheated mixture and the kiln bottom blasted secondary air which has been used to preheat the cold lime has made the temperature to reach up to 950 ~ 1200 °C, thus to complete lime calcination. Due to the add of auxiliary combustion-supporting duct, the temperature at each point is uniform, which ensures the even temperature of the kiln body.

Vertical Shaft Lime Kiln is a Thermal Equipment which is used for heating materials, like cement, copper Metallurgy, ferrous metallurgy, refractory material, chemical materials, paper making etc. 

Introduction

Lime is the high temperature product of the calcinations of limestone. Lime is manufacture in various types of kiln by one of the following reactions;

CaCO3 + heat CO2 + CaO ( high calcium lime)

CaCO3.MgCO3 + heat 2CO2 + CaO.MgO ( dolomite)

The heart of a lime plant is the kiln. There are various types of kiln. The two main types that are commonly employed are the vertical shaft and rotary kilns. Limestone is one of the oldest industrial materials produced by man. Quicklime was produced in U.S. as

early as 1635 in Rhode Island. Today lime continues to be one of the basic supporting materials in the world economy. The fields of water treatment; construction industry, steel production paper manufacture,

fertilizer manufacture, etc, all have in common the usage of lime.

The world economy as a whole and that of each and every country progressing normally will need more and more lime produced it possible at lower cost and higher quality .

Basically lime is produced by two methods, namely; vertical shaft kilns and rotary kilns. Each method has its merits and demerits. The merits of vertical shaft kiln include:

(a) Simplicity of construction and operation

(b) Low initial cost

(c) High thermal efficiency

(d) High volumetric efficiency

(e) Minimum decrepitation of solid products and minimum erosion of refractory linings due to slight movement of particles relative to each other.

Careful consideration of these factors indicates that vertical shaft kilns can be installed for about one-half the cost of operated at about two-thirds of the cost of rotary kiln equipment. The major demerits of vertical shaft kiln are higher labour costs and low capacities.