The system enables the measurement of the coal calorific value directly on the belt conveyer using the combination of radiometric ash content measurement and microwave moisture measurement.
The detection system consists of two measurement frames for ash content measurement and moisture measurement installed on the belt conveyer. The frames can be installed directly on the belt or as a part of the coal sampler.
The ash content detection stage evaluates the coal non-combustible content according to differences of attenuation of two gamma beams of different energy passing through the coal. It contains two radiation sources in protecting container placed under the belt, radiation detector and intelligent mathematic unit. The measurement radiation beam is directed through the conveyer belt, while the presence of persons nearby the device is not limited in any way. The design of the detection stage is focused on maximum reliability and safety.
The moisture detection frame contains the transmission antenna under the belt, reception antenna above the belt and the evaluation unit. The unit determines the moisture based on the attenuation and phase shift of the microwaves. Depending on the type of coal, the antennas can be arranged in different position. The evaluation unit is interconnected with the control stage of the system.
The control stage provides user-friendly operational interface with displaying the data on the touchscreen panel. The control stage can be installed directly in operator workplace. Inside the control stage box, there are accessible terminals for connection of communication interfaces and other analog or digital inputs and outputs.
It is possible to connect several remote terminals to the control unit and so distribute the data to different places if needed. The terminals can handle several tasks according to the use of each operator workplace. Measured and diagnostic data are stored automatically for reverse evaluation.
With suitable calibration the system can be used for any type of coal, the only limitation is the maximum granularity. The range of usable layer height is achieved by interconnection of the measurement methods and also wide dynamic range of the microwave device.
Basic technical data
|Conveyer belt width||not limited|
|Conveyer belt speed||up to 5 m/s|
|Coal granularity*||up to 90 mm|
|Height of coal layer on the belt*||40 - 300 mm|
|Measurement range||as calibrated|
|Power supply||230 V, 50 Hz, 100 VA|
|Working temperature||-20°C to +50°C
moisture in form of ice not measurable
|Outputs*||4x analog output 4 to 20 mA, galvanic
isolated,output assigning programmable,
5x digital output, potential-free, assigning
|Inputs||4x digital passive input (max 40VDC or 24VAC),
|Radiation sources||241Am max.11,1GBq, 137Cs max. 0,37GBq|
|Microwave power output||< 1 mW|
|Dimensions (control stage)||350 x 450 x 155 mm (w x h x d)|
|Dimensions (detection stage)||Individual by belt conveyer construction|
|Weight (control stage)||15 kg|
|Weight (detection stage)||Individual, approx. 2 x 120 kg|
- Online calorific value determination
The calorific value is determined based on the combination of ash content and moisture content value online measurement.
- Ash content measurement
Ash content is available as individual value.
- Moisture measurement
Last valid moisture value is used in case that the measured layer does not conform to the suitable limits.
- Layer measurement on the conveyer belt
The value is available for the reasons of technology interconnection.
- Determination of coal quantity transported by the conveyer belt
(tons per hour) Based on the mathematical profile model of the conveyer and measured layer thickness value.
- Batch measurement in time segment
enables to calculate average calorific value and overall quantity value between START and STOP signals.
- Measurement interrupted on stopping the conveyer
The measurement is blocked if the technology is out of operation.
- Calibration data switching
The device can be calibrated for several types of coal. Calibration data switching can be handled from the control panel or by remote signal.
- Auto power-on
ensures proper operation after power drops.
LAN network connection is available for remote management, data acquisition, maintenance and diagnostics, ModBus RS485 for PLC uplink connection. Measured values converted into the analog outputs.
The detection frames can be placed in a different way depending on its use and coal parameters. In the basic configuration both of the frames are placed directly on the belt conveyer. In case that the coal layer or coal granularity is not suitable for the moisture measurement, the system should be placed near the sampler and the moisture measurement frame should be placed at the crushed coal sample transport system. Such design can be used almost for any kind of coal in case of suitable sampler setup.