Brian Sowerby

Determination of moisture in black coal using pulsed nuclear magnetic resonance spectrometry

Abstract Pulsed nuclear magnetic resonance (n.m.r.) spectrometry was investigated as a technique for moisture determination in fine product coal from eight Australian coal washeries. Measurements were made on samples of diameter 8 and 12 mm and length 10 and 120 mm at frequencies from 6.5 to 60 MHz. The ratio of intensities of the water and coal components in the free-induction decay signal can be used to determine moisture to within ≈ 0.4–0.7 wt% over the range 0–26 wt% moisture, independent of sample density. This accuracy is independent of particle size (up to 1 mm) and little affected by coal rank, sample length or n.m.r. frequency.

On-line measurement of particle size in mineral slurries

Abstract CSIRO Minerals has developed a particle size analyser based on ultrasonic attenuation and velocity spectrometry combined with gamma-ray transmission. The analyser now incorporates a gamma-ray transmission gauge utilising an ultra-low activity radioisotope source that is exempt from licensing regulations. The particle size analyser is applicable to the measurement of 0.1– 1000 μm diameter particles directly in highly concentrated slurries without dilution. The technique has been optimised for use in mineral processing slurries such as those found in grinding circuits. These slurries often have high solids loadings, broad particle size distributions and multiple components of the solid phase. The technique is particularly useful for applications where excess fines may be present. The analyser has been extensively tested on a range of industrial slurries and has been demonstrated in a number of laboratory and plant trials on iron ore, silver/lead/zinc ore and titanium dioxide pigment slurries. CSIRO is currently developing particle size analysis systems for permanent installation in two mineral plants in late 2001 or early 2002.

An on-belt elemental analyser for the cement industry

On-line control of raw mill feed composition is a key factor in the improved control of cement plants. A new and improved on-conveyor belt elemental analyser for cement raw mill feed based on neutron inelastic scatter and capture techniques has been developed and tested successfully in Adelaide Brightons Birkenhead cement plant on highly segregated material with a depth range of 100 to 180 mm. Dynamic tests in the plant have shown analyser RMS total errors of 0.49, 0.52, 0.38 and 0.23 wt% (on a loss free basis) for CaO, SiO2, Al2O3 and Fe2O3 respectively, when 10-minute counting periods are used.

Nuclear techniques for the on-line bulk analysis of carbon in coal-fired power stations

Carbon trading schemes usually require large emitters of CO(2), such as coal-fired power stations, to monitor, report and be audited on their CO(2) emissions. The emission price provides a significant additional incentive for power stations to improve efficiency. In the present paper, previous work on the bulk determination of carbon in coal is reviewed and assessed. The most favourable method is that based on neutron inelastic scattering. The potential role of on-line carbon analysers in improving boiler efficiency and in carbon accounting is discussed.

Plant tests of an on-line multiple-pipe pulverised coal mass flow measuring system

The CSIRO Division of Minerals has developed and successfully plant-tested a commercial prototype pulverised fuel (PF) mass flow measurement system on all four boiler feed lines from a single pulverising mill at Bayswater power station, in the Hunter Valley, NSW, Australia. The CSIRO PF mass flow measurement system utilises measurements of the attenuation and velocity of pulsed beams of 60 kHz ultrasound transmitted across the boiler pipes to determine the PF mass flow in each pipe. The system is used to detect non-uniform distribution of PF between boiler feed pipes. Using this information to balance the burners would lead to improved uniformity of combustion with the benefits of improved combustion efficiency, improved control of NOx emissions, reduced boiler tube erosion and reduced fouling and slagging. During calibration of the mass flow measurement system, PF was measured in the range 3.4–5.9% relative in individual pipes when compared with a beta-ray transmission gauge. A comparison of the mill gravimetric coal feed weighers with the cumulative PF flow measured by the PF mass flow measurement system showed agreement to within 1.8% relative over the primary air range 40–90%.

Fast-neutron/gamma-ray radiography scanner for the detection of contraband in air cargo containers

There is a worldwide need for efficient inspection of cargo containers at airports, seaports and road border crossings. The main objectives are the detection of contraband such as illicit drugs, explosives and weapons. Due to the large volume of cargo passing through Australias airports every day, it is critical that any scanning system should be capable of working on unpacked or consolidated cargo, taking at most 1-2 minutes per container. CSIRO has developed a fast-neutron/gamma-ray radiography (FNGR) method for the rapid screening of air freight. By combining radiographs obtained using 14 MeV neutrons and 60Co gamma-rays, high resolution images showing both density and material composition are obtained. A near full-scale prototype scanner has been successfully tested in the laboratory. With the support of the Australian Customs Service, a full-scale scanner has recently been installed and commissioned at Brisbane International Airport.

Plant trial of an ultrasonic gauge for the on-line measurement of pulverised coal mass flow

The CSIRO Division of Minerals has developed and successfully plant tested an ultrasonic gauge for the on-line measurement of the mass flow rate of pulverised coal in a power station. In its simplest form, the CSIRO ultrasonic mass flow gauge comprises one pair of ultrasonic transducers mounted on opposite sides of a burner feed pipe such that the ultrasonic beam is at about 60/spl deg/ to the coal flow direction, thus enabling coal density and flow velocity (and hence coal mass flow) to be determined using a single pair of transducers. The ultrasonic gauge has been tested on a boiler feed line at Bayswater Power station, NSW, Australia. The results obtained have shown that the ultrasonic technique can measure coal loading to within 3.9% relative error and velocity to within 1.3 m/s over a wide range of plant conditions The main incentive for developing a pulverised coal mass flow gauge is to detect non-uniform distribution of pulverised coal and air to burners served by a common pulveriser. Once detected on-line correction techniques could be developed which could result in improved combustion efficiency, reduced tube erosion and reduced fouling and slagging.

On-line determination of pulverised coal mass flow using an ultrasonic technique

The performance of pulverized coal-fired boilers in power stations can be improved by adjusting combustion conditions to minimize losses due to incomplete combustion and excess air. This can be achieved by balancing the burners and then adjusting excess air to minimize losses. Balancing burners under a range of boiler conditions requires on-line measurement of pulverized coal mass flow to individual burners. An ultrasonic technique to meet this need is described. The technique is noninvasive and has no moving parts. It was used to determine air velocity to within 0.35 m/s over the range 10 to 30 m/s. Calibration against beta-ray transmission using glass microspheres in a large-scale laboratory recirculating rig showed that mass loading could be determined to within 5% relative over the range 0.1 to 1.0 mg/cm/sup 3/ at constant velocity and 8% relative over a wide range of velocities.<<ETX>>

On‐Line Measurement of Mass Flow of Pneumatically Conveyed Solids

CSIRO has developed an ultrasonic attenuation and transit time technique and a microwave transmission technique for on-line determination of the mass flow of pneumatically conveyed solids. In a comparative plant trial on a single burner line at Bayswater power station. the ultrasonic technique determined the coal density and velocity with rms errors of 3.9 and 5.9% relative respectively; the microwave technique successfully determined the coal density with an rms error of 6.2% relative, but was unable to accurately determine solids flow velocity at the low coal densities typical of the trial. In a plant trial at a direct smelter. the microwave technique successfully determined the mass flow of pneumatically conveyed iron ore lines feeding the smelter with an rms error of 10.2% relative.

On-Belt Analysis of Ash in Coal

A new neutron and gamma-ray analysis system has been developed for the direct on-conveyor belt analysis of ash in coal. This analysis system incorporates a method for ash measurements that is relatively independent of changes in segregation, belt loading, and ash composition. Consequently, the analysis system provides greater accuracy than on-belt dual energy gamma-ray transmission (DUET) gauges but at a much lower cost than by-line prompt gamma-ray neutron activation analysis (PGNAA) analyzers and samplers. The NITA (Neutron Inelastic scatter and Thermal capture Analysis) method simultaneously measures prompt neutron inelastic scatter and thermal neutron capture gamma rays from bulk coal samples using a 241 Am-Be fast neutron source and bismuth germanate (BGO) detectors in transmission and backscatter geometries. The NITA method has been tested in both laboratory feasibility studies and, more recently, under simulated industrial conditions using a prototype analyzer. Measurements have been carried out on coal samples of ash contents from 6.7 to 49.4 wt% (dry basis (d.b.)) with variable ash composition and at thicknesses between 100 and 300 mm. The results show that accuracies of ∼0.5 wt% ash are achievable over a wide range of ash values, compositions, and thicknesses.