Evaluation of Heavy Medium Circuits Using Density Tracers

2. By Christopher J. Barbee Virginia Polytechnic Institute and State University Blacksburg, Virginia Evaluation of Heavy Medium Circuits Using Density Tracers

3. This presentation will outline the testing of RFID Technology for use in density tracer testing Basics of HMC operation Problem Statement Testing Program

4. Annual US Production of 250 MM tons of clean coal from HM circuits A 2% point increase in efficiency = Additional 4.5 MM tons of saleable coal @ $30/ton the recovered tons is valued at $135 MM to the total US coal Industry $500,000 for an average preparation plant Proper operation of heavy medium circuits makes good economic sense

5. These vials demonstrate the basic concept of heavy medium separation Increasing Specific Gravity

6. The high G force cyclone speeds up the float/sink process for 50-0.5 mm coal Principle of Operation Rotating suspension of media forces lighter particles to the center and upward through the vortex finder, while heavier particles spiral outward and down through the apex. FEED MATERIAL Cap Body Vortex Finder Apex HIGH DENSITY PRODUCT LOW DENSITY PRODUCT

7. Here is an example of a partition curve Density Tracer Data Points Mathematical Curve Fit Partition to Refuse (%) Specific Gravity

8. This is a typical heavy media cyclone circuit Feed HMC Raw Coal or Deslime Screens Drain & Rinse Screen Drain & Rinse Screen To Fine Coal Circuit Clean Coal Magnetic Separator Reject Refuse Magnetite Storage Bin Bleed Raw Coal or Fine Coal Circuit Water Water Density Gauge Dilute Media Sump Heavy Media Sump Level Gauge

9. Here is an example of the potential loses resulting from not matching cutpoints Twin DMC Circuit (500 TPH Total Capacity) • Malfunctions or design flaws that give different cutpoints for a multi-unit HMC circuit adversely impacts performance. • This problem is very severe when low-ash coals are produced. • Problems may include poor feed distribution, media contamination, overloaded circuits, worn apexes, etc. Clean Coal Ash (%)

10. During an 8 plant investigation in 2001 the following improvements were made

11. Equipment used for a conventional tracer test Examples of sampling tools that were purchased or fabricated for the collection of density tracers and samples of clean coal, refuse and circulating media. Density tracers (32 mm cubes) sorted into groups of 20 each (1.32 to 2.50 SG) just prior to being introduced into the cyclone feed stream.

12. Current density tracer testing methods have problems related to personnel and accuracy Photograph showing the collection of density tracers from the clean coal drain-and-rinse screens below a bank heavy media cyclones. Approach: Use Radio Frequency Identification (RFID) technology to track density tracers as they move through a separation process.

13. Loss of tracers is common using the conventional method of tracer recovery

14. The use of RFID would solve both of the current testing problems • The electronic setup would remove the need for a large number of personnel • The radio waves will pass through the coal, therefore even tracers that are covered will be counted

16. Low Frequency (Below 500 kHz) Short to medium range Medium data rate Less orientation sensitive Reads through non-metallic Low power levels Inexpensive Noise Sensitive High Frequency (above 1 MHz) Medium to long range Fast data rate More Orientation sensitive Less able to penetrate High power levels Expensive Not noise sensitive Moisture Issues The frequency is chosen based on the application and the environment

17. There are some design factors to consider when developing the system Q Factor – Measure of antenna efficiency Where: fr is the resonant frequency, L is the inductance, and R is the resistance 15 – 50 ms Charge up time

18. The RFID system has three main components Antenna Transponder/Tag Reader/Data Acquisition

19. The tag is energized by a time-varying electromagnetic radio frequency (RF) wave that is transmitted by the antenna

20. Read Only Transponder When in the interrogation zone it continually transmits its serial number of a few bytes with a check digit attached Transponder’s unique identification number is incorporated into the chip during manufacture This number cannot be altered Simple layout allows for cheap production Each transponder is imprinted with an individual ID number

21. The Data Acquisition System tallies the tracers and generates a partition curve 10783455 10783454 10783452 10783453 WinWedge & Excel VBA

22. The orientation of the tag affects the read range

23. This is the pilot scale test setup for preliminary testing

24. Future work will involve on site testing of the system 50

25. RFID technology was investigated and integrated into the density tracers Static testing was done to understand the operation of the transponder tracers Dynamic testing has begun and results are encouraging In plant testing of the system will be the next major step in development of the program. Scale up issues will become more evident at that time. In summary, there is a need for an more accurate and automated tracer testing program

26. End of Presentation