Standardisation of Auto Sampler cum Sample Preparation Unit at Nandan Washery

1. Standardisation of Auto Sampler cum SamplePreparation Unit at Nandan Washery Dr R Dasgupta and Dr Kalyan Sen, 1999

2. Nandan Washery Designed & Commissioned by M/S Voest-Alpine of Austria, 1984 3-product Komag Jigs (Coarse & Fine Coals) Flotation Cleans to Bhilai Steel Plant for metallurgical use Sampler before the Storage cum Loading Bunker

3. Material flow diagram of Nandan washery

4. Purpose • No arrangement for sample collection during actual loading of washed coal • Quantity of samples from sampler is not adequate • Less load on clean coal belt

5. Objective • To standardise the Auto Sampler cum Sample Preparation Unit • Ultimate Aim • Joint sampling by producer & consumer without any external surveillance • To evolve & Articulate practical procedure for future use, within the broad guidelines of Stipulated Standards

6. CFRI Strategy • To evolve methodology through participation of Nandan, CCSO & CFRI officers • Stepwise study or approach • Preliminary planning - at washery site • Preliminary test experiments • Final corrective measures, data collection, collation & Statistical tests

7. Preliminary Tests Conclusion • Adjustment of double roll crusher • Change in sampler time interval • Dividing ratio (?) • Replacement of Chemical balance • Procurement of Digital balance (20 kg) for Total moisture determination

8. Test Methodology • Sample Collection and Preparation • Sampling Points identification • Sample collection & preparation • Ash • Total moisture

9. Sampling Points Belt Sample S1 (Stop belt) Flap Sample S2 * Auto Sampler S3 Bottle Sample S4 * discontinued at later stage

10. Sampler cum Sample Preparation S2 - Flap S3 S1 S4

11. Ash Sample Preparation • Gross Sample • Air dry & Crush to 12.5 mm • Air dry (if required oven dry at 35 deg but not more than 2 h at a time) • Reduce the sample to 2 kg • Divide into 4 parts • 2 parts (Reserve); 1 part (212 micron) & 1 part (212 micron) • 1 part preserve as check sample • 1 part divide using laboratory divider (2 samples) • Sample A1 Sample A2

12. Total Moisture Sample Preparation Gross Sample Record Initial wt. Air dry Record wt. Stage 1 loss% Y Size Crush to 12.5mm 12.5 mm above ? N Oven dry 35deg not exceed 2h Stage 2 loss% Record wt. Reduce 2.5kg Crush to 2.8mm Divide into 4 parts RESERVE Sample A Sample B Stage 3 Moist. 10g, 108deg, 2h

13. Statistical Analysis • Coal is heterogeneous material • Very difficult to achieve highest level of Sampling precision • In terms of variance • 80 % is from Sampling • 20 % is from preparation & analysis • Overall precision is influenced primarily due to Sampling • Utmost importance thus need to be given for Sampling

14. Statistical Analysis Testing of Bias • Paired samples • One member is the “System” under test • Other one “Reference” • An intrinsically unbiased sample • To be obtained by stopping belt method • Series of differences are subjected to Statistical analysis

15. Statistical Analysis Assumptions • A normal distribution of the variable • Independence of the errors of measurement • Statistical homogeneity of the data

16. Statistical Analysis Basic Steps • Test for flagging outliers • Estimation of number of pairs required • Assessment of Bias • Method I • Method II • Test for significant difference from zero • Test for significant difference from B (MTB)

17. Common Sample Preparation Common Bottle Sample Record Initial wt. Air dry Stage 1 loss% Record wt. Oven dry 35deg not exceed 2h Stage 2 loss% Record wt. Divide into 2 parts Divide Crush to 2.8mm Crush to 2.8mm Crush to 2.8mm Divide into 2 parts Sample A Sample B RESERVE Stage 3 Moist. 10g, 108deg, 2h Sample C Ash