LIME PUTTY
[EIRI/EDPR/1002] J.C.: 9640XL
INTRODUCTION
Applied processes and techniques in lime manufacturing
The lime making process consists of the burning of calcium and/or magnesium carbonates at and to obtain the derived oxide (CaCO3 ® CaO + CO2). For some processes significantly higher burning temperatures are necessary, for example dead-burned dolomite. The calcium oxide product from the kiln is generally crushed, milled and/or screened before being conveyed to silo storage. From the silo, the burned lime is either delivered to the end user for use in the form of quicklime, or transferred to a hydrating plant where it is reacted with water to produce hydrated or slaked lime.
Lime processes mainly contain the following basic steps, which are illustrated in Figure
• Winning of limestone
• Limestone storage and preparation
• Fuels storage and preparation
• Calcination of limestone
• Quicklime processing
• Quicklime hydration and slaking
• Storage, handling and transport
The Winning of limestone
The raw material for lime production is limestone or, to a lesser extent, dolomite or dolomitic limestone. Dolomite and dolomitic limestone are mixtures of calcium carbonate and up to 44% magnesium carbonate. While limestone deposits are relatively abundant in many countries, only a small proportion are suitable for commercial extraction. High purity limestone or dolomite is quarried, crushed, and in some cases washed. It is then screened and transported to the kiln. Limestone is normally obtained by surface quarrying, generally adjacent to the lime plant, but in some cases sea dredging or even underground mining are used. A typical mining process includes:
• Removal of the overburden (i.e., the soil, clay and loose rock overlying the deposit).
• Blasting of rock.
• Loading and transportation of the blasted rock to the crushing and screening plant.
Limestone preparation and storage
Limestone is crushed to the appropriate size range, which is normally 5 to 200 mm depending upon the kiln used. Primary crushers receive quarry rocks as large as one metre in diameter and reduce their size down to 100-250 mm. Crushed stone from the primary crushers is transported via conveyors to vibrating screens, where large pieces are separated and recycled while those passing through are used as kiln charge, or may be fed into the secondary crushers located further down thenprocess line.
Secondary crushers yield pebbles of 10 to 50 mm, which after screening are transported on belt conveyors and/or bucket elevators to limestone storage silos or compartments for storage prior to feeding the dryer or the lime kiln.
Depending on the nature of the rock (hardness, lamination, size etc.) various types of primary crushers are used, such as: jaw crushers, gyratory crushers and impact crushers. As the kiln charge does not have to be very fine, jaw and impact crushers are also often used as secondary crushers, as are hammer mills. Sometimes crushing plants are located at the quarry and are mobile. The particle size distribution must be compatible with the requirements of the kiln. This generally requires the stone to be positively screened to give a size distribution of, ideally 2 to 1, or at least 3 to 1.
Washing is sometimes used to remove natural impurities such as silica, clay and the very fine particles of limestone. This washing aids the burning process by leaving free space between the stones for combustion air circulation, thus reducing the amount of excess air and saving electrical energy. Techniques for piling the limestone, for better cleaning, have been developed. Screened sizes of limestone are stored in bunkers and in outdoor stockpiles. Fine grades are usually stored in sealed bunkers. In a very limited number of installations (for example, where the calcium carbonate is in the form of a sludge or filter cake), it is necessary to dry the feed material. This is generally done by using the surplus heat from kiln exhaust gases.
COST ESTIMATION
Plant Capacity 10 MT/Day
Land & Building (2000 sq.mt.) Rs. 1.46 Cr
Plant & Machinery Rs. 22.00 Lac
Working Capital for 3 Months Rs. 38.03 Lac
Total Capital Investment Rs. 2.13 Cr
Rate of Return 51%
Break Even Point 37%
CONTENTS
INTRODUCTION
APPLIED PROCESSES AND TECHNIQUES IN LIME MANUFACTURING
LIME PROCESSES MAINLY CONTAIN THE FOLLOWING BASIC STEPS, WHICH ARE ILLUSTRATED IN FIGURE
WINNING OF LIMESTONE
LIMESTONE PREPARATION AND STORAGE
FUELS
THE CHOICE OF FUEL(S) FOR A LIME-BURNING OPERATION IS IMPORTANT FOR THE FOLLOWING REASONS:
CALCINING OF LIMESTONE
THE LIME BURNING PROCESS TYPICALLY INVOLVES:
GAS SUSPENSION CALCINATION PROCESS
FIGURE 2.8: GAS SUSPENSION CALCINATION PROCESS
QUICKLIME PROCESSING
PRODUCTION OF GROUND QUICKLIME
PRODUCTION OF SLAKED LIME
PRODUCTION OF HYDRATED LIME
FIGURE
FIGURE: FLOWSHEET OF A 3-STAGE LIME HYDRATOR
PRODUCTION OF MILK OF LIME AND LIME PUTTY
STORAGE AND HANDLING
STORAGE
STORAGE OF QUICKLIME
STORAGE OF HYDRATED LIME
STORAGE OF MILK OF LIME
HANDLING
MARKET POSITION
TABLE A
CURRENT PRODUCTION OF INDUSTRIES USING HYDRATED LIMEAND PRECIPITATED CALCIUM CARBONATE
DEMAND FORECAST
REQUIREMENT OF HYDRATED LIME
TABLE B
DEMAND FORECAST FOR HYDRATED LIME IN INDIA
CHART 1
COMPOSITION OF HYDRATED LIME MARKET IN INDIA
TABLE C
DEMAND FORECAST FOR HYDRATED LIME IN WESTERN REGION
HYDRATED LIME INDUSTRY IN INDIA
TABLE F
MAJOR MANUFACTURERS OF HYDRATED LIME
TABLE G
SMALL-SCALE MANUFACTURERS OF HYDRATED LIME
PROCESS TECHNOLOGY
CONCLUSION
LIME-BASED PLASTERING MATERIAL COMPOSITIONS
EXAMPLE 1
INDUSTRIAL APPLICABILITY
ORGANIC LIME SLURRY AND METHOD OF PREPARATION
HYDRATED LIME DISPERSED IN WATER ( H 2 O-MOL SAMPLES):
METHOD AND APPARATUS FOR HYDRATING LIME
CEMENTITIOUS FORMULATIONS AND PROCESSES
LIQUID COMPOSITION ADDITIVE TO REDUCE CURING TIME OF SURFACE COATINGS
MANUFACTURE OF LIME PUTTY
SUPPLIER OF RAW MATERIAL ON LIME AND LIME PUTTY
LIME STONE
SUPPLIER OF PLANT AND MACHINERY
FURNACE
PULVERIZER
REACTION KETTLES
APPENDIX – A:
01. PLANT ECONOMICS
02. LAND & BUILDING
03. PLANT AND MACHINERY
04. OTHER FIXED ASSESTS
05. FIXED CAPITAL
06. RAW MATERIAL
07. SALARY AND WAGES
08. UTILITIES AND OVERHEADS
09. TOTAL WORKING CAPITAL
10. TOTAL CAPITAL INVESTMENT
11. COST OF PRODUCTION
12. TURN OVER/ANNUM
13. BREAK EVEN POINT
14. RESOURCES FOR FINANCE
15. INSTALMENT PAYABLE IN 5 YEARS
16. DEPRECIATION CHART FOR 5 YEARS
17. PROFIT ANALYSIS FOR 5 YEARS
18. PROJECTED BALANCE SHEET FOR (5 YEARS)