Some Relevant Technical Issues on Consistent Coal Quality Asim Chowdhuri &

1. Some RelevantTechnical IssuesonConsistent Coal Quality Asim Chowdhuri & Dr Kalyan Sen, CFRI, 2003

2. Approach towards Quality Improvement & Supply of Consistent Quality • Proper QMS • Technological options for Quality enhancement • Modification of Standards • Revision of Coal Categorisation

3. Existing Quality Monitoring System • Manual sampling • Wagon top sampling • Mechanical sampling • Constraints • Handling of large sized coal

4. Quality Monitoring of Coal Problems of Wagon top sampling • Sampling sites • Inadequate facility - sampling, preparation & analysis • Insufficient time, manpower, etc. • Results sampling from top only How it affects final results • Less reliable due to higher errors • Disputes between supplier & consumer • Nation being the ultimate looser

5. Quality Monitoring of Coal Problems of Mechanical Sampling(200mm sized coal) Constraints • Higher Bias leading to disputes • High Spillage • Frequent Chute choking • Rapid wear & Tear • High Capital investment & Maintenance costs

6. Proposed Modification in SamplingProcedure • Supply of lower size coals (50 mm or below)and inclusion of AMS • Benefits • More reliable quality data • Less Capital investment • Low maintenance cost • in case of temporary failure of AMS theadvantage would be for switching over towagon top sampling with better precisionthan that for higher sized coals

7. Identified Technological Optionsfor Coal Quality Upgradation • Globally accepted Options for better economicsand less environmental pollution • Mine planning • Dry deshaling at Pit heads • Judicious blending • Wet beneficiation

8. Identified Technological Optionsfor Coal Quality Upgradation Present rider: ash level of 34% Proposed: The degree of washing should be limited to that density of cut at which the final product is free from any particle of ash higher than 50-55%. Of course, this often leads to overallash content level more or less 34%.

10. Ash% reducn M % over ROM coal Level Scheme Methodology Cleans (%) I Dry benefic. Separation of stone/shale based on differential breakage potentiality 3-4 >90 Nil II Crushing, screening & coarse coal cleaning Coarse coal (13/30mm) washed & mixed with untreated fines; dewatering screens. <10 70-90 2-3% >10 <60 3-4% III Crushing, screening and total cleaning Coarser fraction washed at optimum efficiency levels: fine coal by Spiral: dewatering Technology Routes for beneficiation

11. Proposed Modification of Standards • Adoption of ISO 13909 (Mechanical Sampling) • Adoption of ISO 9931 (for Pulverized Coal) • Reaffirmation of IS 13810 (Code for F&S) • Change in ISO 1213 -1 (a new term) • Characteristic Ash: • The ash of the particles in a closely spaced relative density fraction obtained from Float & Sink analysis

12. Revision of Coal Categorisationfor commercial purpose • Categorisation system based on GCV (as recd. Moist. basis) & weightage on the ash • A Matrix system with closely spaced GCV & ash value. • Coal quality could be assessed by maximum ash value and lowest GCV value that will • Remove anomalies of the present system • Provide incentive for better quality • Ensure consistent quality of a consignment