What is the recommended size for limestone to be used in the kiln?

A narrow size range, typically between 40 mm and 80 mm, is recommended for uniform calcination and permeability (Clause 4.1.2).

What is a key consideration for fuel selection besides calorific value?

Low ash and sulphur content are critical. The ash should have a high fusion temperature to avoid clinker formation (Clause 5).

How can heat loss from the discharged lime be minimized?

By using the heat from the hot lime in the cooling zone to preheat the combustion air drawn from the bottom of the kiln (Clause 6.4.1).

What is the typical ratio of limestone to fuel?

The ratio varies based on fuel quality and limestone purity, but a typical range is 8:1 to 10:1 by mass.

IS 14860

: 2000

Guidelines on Fuel Saving in Vertical Mixed-feed Lime Shaft Kilns

CurrentSpecializedGuidelinesMaterials Science · Building Limes and Gypsum Products

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This standard provides guidelines for conserving fuel in vertical mixed-feed lime shaft kilns. It covers the selection and preparation of raw materials and fuel, optimal operational parameters, and design aspects of the kiln to maximize thermal efficiency. The primary objective is to reduce energy consumption per unit of lime produced.

Guidelines on Fuel Saving in Vertical Mixed-feed Lime Shaft Kilns

Quick Reference Values

Recommended Limestone Size40 mm to 80 mm

Desirable CaO content in Limestone> 90%

Maximum Sulphur in Fuel< 1.0 %

Ideal Calorific Value of Fuel (Coke)6500 to 7000 kcal/kg

Target Thermal Efficiency70-85 %

Typical Limestone to Fuel Ratio (by mass)8:1 to 10:1

Optimal Flue Gas Temperature150-250 °C

Key Formulas

Thermal Efficiency (%) = (Heat utilized for calcination / Total heat supplied by fuel) x 100

Practical Notes

Maintaining a uniform size ratio between limestone and fuel is critical for even heat distribution and preventing segregation in the kiln.

The ash fusion temperature of the fuel must be higher than the maximum operating temperature of the kiln to prevent the formation of clinker, which obstructs the flow of material.

Regular monitoring of flue gas composition (O2, CO, CO2) and temperature is the most effective way to control the combustion process and optimize the air-to-fuel ratio.