On-Belt Ash Analyzers and Scales in Open Pit Coal Mines

    BCA-5 on the excavator boom         BCA-5 on open pit belt conveyor

Benefits of using the On-line Coal Analyzers BCA in the Coal Mines

Meeting customer’s requirements

The on-line management of quality significantly improves meeting customer’s requirements for the coal quality. You shouldn’t wait for laboratory analyses to find out if the yesterday’s coal quality was or was not as required.

Improving coal/overburden ratio

On-site blending of coal during the excavation trough the BCA analyzers allows the usage (instead of throwing out) of some high-ash coal, when it is compensated by the low-ash coal excavated by other diggers.

Optimization of the mining processes

Obtaining reliable data for the work of all excavators allows the staff in charge to have a fast reaction when necessary.

In general the benefit of using BCA is reducing of the production costs.

The pay back period for BCA instruments is about one year of operation.

Construction and installing of BCA

In the Southeast part of the Thracian valley are located the biggest Bulgarian coal open pits - Maritza East Mines. There are three open pits and in all of them work Analix On-Belt Coal Analyzers – totally 17 such instruments. Each of these analyzers BCA measures on-line the ash content of the excavated coal as well as the current belt load and the total coal quantity directly at the excavators and at the outgoing belt conveyors.

The Ash Analyzers are mounted directly on the Belt-Conveyors without changing the construction of the Conveyor.

The supporting structure of the on-belt ash analyzer is a rectangular frame vertically mounted and embracing the belt. On the top crossbeam is mounted the detector unit registering irradiation cross passing the coal.

Supporting frames of Analix BCA on different conveyors in Open Pit Mines

Under the belt is mounted the shielded container with two sources of radiation. Due to а heavy lead protection covering sources no radiation could be obtained at any point around the instrument. There is only one narrow collimator letting a pencil type beam to go out vertically across the coal to the detector where this beam is totally absorbed. You can see the mechanics of this unit opening and closing the collimator. It could be made automatically, or by remote control, or locally during the service works.

In waterproof side mounted boxes are housed supplying units for low and high voltage, specialized electronics processing the detector signal, high speed spectral analyzer controlled by a local processor, and the computer. The computer controls the measurements, calculates the load and the ash content and supports the connection with the server.

Shielded container with shutter         Side mounted electronics boxes

A Coal Quality Management System (CQMS) in Maritza East Mines is based on these 17 on-belt ash analyzers, produced by Analix.

The quality control is performed by comparison between contracted with the client quality and the fluent coal ash content. Balancing the load of the extractive excavators the Dispatcher reaches desired ash content.

In 2 of the 3 Maritza East pits trains to the TPP stations carry the coal. Four on-belt ash analyzers were installed at the end of each belt conveyor line, loading coal into the trains. In the third open pit the excavated coal is transported to the TPP directly with a belt conveyor.

BCA on the outgoing conveyor loading trains to TPP

The on-belt radioisotope ash-content analyzers BCА operate fully automatically and operator service is not required, except in case of failure or damage. They are designed and built in such way that they do not require adjustments and service during normal operation. The current maintenance includes only periodical status check and empty belt normalization.

The construction of the instruments is module-based and allows service and maintenance works in almost any conditions and usually without stopping the belt.

Accuracy of BCA

The standard error for ash content:

• 0.5%  for the range   5.0 ÷ 15.0%
• 1.0%  for the range 15.0 ÷ 25.0%
• 1.5%  for the range 25.0 ÷ 35.0%
• 2.0%  for the range 35.0 ÷ 50.0%

For total weight the accuracy is about 2 % for quantities more than 500 t.

Radiation safety of BCA

Our instruments are permanently checked and licenzed by the Bulgarian Agency for Nuclear Regulation.

All measurements done by all kind of regulatory officials (Agency for Nuclear Regulation, Ministry of Health, Ministry of Internal Affairs, etc.) confirm the complete radiation safety of our radioisotope on-belt ash-analyzers.

The staff passing by, or working around as closed as possible, do not obtain any irradiation.

There is no one case the radiation for people working there or passing by to be higher then the native radioactive background for that area.