Applied measurement methods
Continuous measurement of ash content in coal is conducted using the innovative radiometric scattering and absorption method developed by WILPO in 2009. The method is based on irradiating a layer of coal (from above) with low-energy gamma rays and on recording the intensity of gamma radiation reaching a set of detectors arranged under the conveyor belt. Instead of one detector, a system of two appropriately positioned detectors has been introduced: one to measure scattered radiation, the other to measure absorbed radiation.
This enabled the gathering of data on ash content variability and on surface density of the coal analyzed using one radiation source. The applied configuration provided measurement advantages which were unattainable until now, while retaining the valuable features of radiometric ash meters used before.
Continuous measurement of moisture content in coal is carried out with use of the technology that consists in absorption of microwaves. The technology is constantly improved and it has perfectly proved itself in many past developments of measuring equipment offered by WILPO.
Unparalleled advantages of the innovative scattering and absorption method of ash content determination in coal
- Measurement covers 35% to 50% of the coal stream (unattainable with other radiometric measurement methods).
- Maximum representativeness of measurement results (unattainable with other radiometric measurement methods).
- Continuous measurement of ash content in coal on conveyors with any type of belts (including those with steel cords – absolute novelty).
- Continuous measurement of ash content in coal layers higher than 300 mm (important novelty).
- Continuous measurement of ash content in nonhomogeneous coal (coal blends).
- Continuous measurement of ash content in coal stacked in layers on belt.
- Completely safe in use – one optimum source of soft gamma radiation (60 keV).
- No need of scanning.
- No contact between measurement units and coal.
Application opportunities for new generation equipment
Basic applications of the new generation devices (WILPO C 5XX) include such cases of location and installation conditions, where continuous measurement of ash content in coal was until now not possible (e.g. conveyors using belts with steel cord) or difficult (e.g. conveyors using belts that strongly absorb gamma radiation, thick layers of nonhomogeneous coal on conveyor belt).
New generation devices are highly versatile: in almost every location, where until now ash meters of various design were used, these new devices will generally provide much more representative measurement results.
WILPO C 532hc – coal quality parameters measurement system
The WILPO C 532hc measuring system consists of two major units: the measuring unit and the data processing and display unit. The measuring unit comprises two key modules: the ash content measurement module and the moisture content measurement module. Each of these modules is installed on a suspension frame and provided with relevant measuring heads. There is one control unit common for both modules. The control unit incorporates a programmable controller, power supplies and data transmission systems.
Schematic diagram of the measuring unit of the WILPO C 532hc system
- 1 – gamma-ray head with isotopic radiation source,
- 2 – gamma-ray detection head (scattered radiation),
- 2’ – gamma-ray detection head (absorbed radiation),
- 3 – material layer thickness sensor,
- 4 and 8 – suspension frames (of the ash content and moisture content measuring systems),
- 5 – control unit,
- 6 – microwave detector head,
- 7 – microwave generator head.
The key component of the data processing and display unit is a computer furnished with dedicated software. This unit can be installed anywhere as required by the user, for instance at the Coal Quality Control Department, central control room, etc.
Example screen shot of the WILPO C 532hc system display
Measuring unit of the WILPO C 532hc system.
Services provided when delivering equipment
At every stage of the process of deciding which measuring device will be optimal, we provide technical consultancy at no extra cost (including a site visit).
In the case of specific on-site conditions (e.g. non-standard belts, belts with steel cord, coal layer height on belt above 300 mm, etc.) our standard solutions may be customized according to individual needs, including adjustment or redesigning of suspension frames, use of isotopic source of adequate activity or other modifications.
WILPO provides delivery of the device, field installation, adjustment and personnel training. We also offer assistance in acquiring permits for the use of devices containing radioactive isotopes.
Warranty, maintenance and repair services
During the warranty period WILPO provides free maintenance and repair services. The scope of services and duration of the warranty period is detailed in the warranty certificate.
Based on a separate service contract we can also provide maintenance and repair services after expiration of the warranty period. These services include verification of the tightness of the radiation source, general inspection of equipment and, when necessary, repairs and adjustments.
|Coal particle size range||0 – 70 mm|
|Minimum thickness of coal layer||50 mm|
|Maximum thickness of coal layer|
|simultaneous ash and moisture determination||250 mm|
|ash determination only||500 mm|
|Ash determination method||radiometric, scattering and absorption|
|Moisture determination method||absorption of microwave radiation|
|Source of gamma radiation||Am-241 isotope|
|design||encapsulated source, special form|
|activity||3.7 to 18.5 GBq|
|Gamma radiation detector||scintillation probe (x2)|
|Accuracy of ash determination||0,7% ≤ σ ≤ 2%|
|Accuracy of moisture determination||0,5% ≤ σ ≤ 1%|
|Accuracy of calorific value determination||200 kJ/kg ≤ σ ≤ 600 kJ/kg|
|Rated supply voltage, UN||230VAC, 50 Hz,|
|Power consumption||300 VA (incl. heaters)|
The new design of the measuring system, most importantly that of the ash meter which includes a single and low-energy (60 keV) Am-241 radiation source, is perfectly safe. The device has been approved for manufacturing by WILPO by the Polish National Atomic Energy Agency (PAA) in Warsaw (permit No. D-17222 of 24 June 2009).
WILPO also holds a permit issued by PAA for the turnover, installation and transportation of equipment comprising sources of radiation (permit No. D-15512 of 14 January 2005, annex No.1 of 26 May 2008).Back to top