Investigations into the Effects of Moisture Loss and Coal Blending on Hardgrove Grindability Index (HGI)
HB Vuthaluru, HM Yan, DK Zhang  Curtin University of Technology, Perth and J Brooke, Westfarmers Coal Limited, Perth
Investigations into the effects of moisture and coal blending on Hardgrove Grindability Index (HGI) were carried out on Collie coal of Western Australia. Experiments were conducted in a standard Hardgrove apparatus in two stages comprising three Premier seam coals  (namely P2, P4 and Hebe) and several      blends (namely Hebe/P2, Hebe/P4, Hebe/P2/P4) prepared at various blending ratios. Stage 1 experiments comprised of five days of air-drying followed by oven drying. Stage 2 experiments followed the procedure of overnight air drying with 2 and 4 hours oven drying at 40°C on successive days.
 
Among the coal seams tested in Stage 1, Hebe showed the highest HGI (58) whereas P4 was the lowest (46). Stage 2 experiments, however, showed much lower values of HGI with the new batch of Hebe samples collected from the same pit. HGI was found to correlate well with residual moisture in both stages of experiments, with correlation coefficients ranging from 0.5-0.9 depending on the type of coal seam or blend. In contrast, moisture measurements on HGI samples (0.6-1.8 mm fraction) showed erratic trends with HGI. Both Stage 1 and Stage 2 experimental results suggest that no relationship exist between HGI sample moisture and HGI. Blending showed the positive effect on both binary (P2/Hebe and P4/Hebe) and ternary (P2/P4/Hebe) blends with HGI values shifting towards those of Hebe seam (ranged 48-55). However, the effects of blending and blending ratio on HGI were not evident in Stage 2 experiments mainly due to closely spaced HGI values of coal seams. Measured HGI values of binary and ternary blends in Stage 1 and Stage experiments were found to correspond well with the weighted average values of HGI within + 2 HGI units.
 
Extension of the Operating Regime of Utility Boiler
B Singh Sigma  Process Solutions, Brisbane
The operating regime of a utility boiler is controlled by the number of burners in service and the turn down ratio of the burner. The number of burners is services varies, in steps, by a fixed number (4 or more) depending on the design of the pulveriser and the size of the boiler. The need to change in the number of burners to meet the varying demand is a costly operation and makes the unit inflexible during this period. This paper presents the results of trials in extending the operating range of a burner by controlling the size distribution of the pulverised fuel from almost micronised to normal range. Trials conducted at Swanbank B Power Station show that the lower operating output of a 120 MW boiler can be extended from 75 to 40 MW.

Thermochemical Recuperative Hydrogen Production from Brown Coal
C Fushimi, M Goto and A Tsutsumi University of Tokyo, Japan; J Hyashi and T Chiba University of Hokkaido, Japan
In this study, the fundamental research on the reactivity of Australian brown coal with the steam reforming gasifications was conducted at the heating rate of 100K/s by using a thermogravimetric reactor.  The pyrolysis (thermal decomposition) finished only 10-15 s and the steam gasifications reaction completed in very short time.  About 70-80% of coal energy was converted into hydrogen by the steam reforming

Co-firing of Bark and Industrial Coals on a Stoker Fired Combustion System
A Clemens, D Gong  CRL Energy Ltd New Zealand;  and J Gifford  Forrest Research New Zealand
Addition of biomass (a low sulphur and CO2 neutral fuel) to the fuel mix at coal-fired plant has potential benefits including reduced SO2 and CO2 emissions.  However before using biomass in existing coal plant an assessment of the performance of coal/biomass mixtures is needed to understand and minimise operational problems and optimise the properties of the fuel blend.
 
To evaluate the performance of coal/biomass mixtures, co-firing of mixtures (92.5/7.5, 85/15 and 77.5/22.5) by calorific value was undertaken on a laboratory scale (50 kW) combustion rig with a stoker firing system.  The biomass was a bark sourced from debarking operations at a saw-mill.  Samples of a typical New Zealand sub-bituminous industrial coal from the Waikato region were used.
 
Combustion performance of the mixtures varied considerably from that of the sub-bituminous coal samples alone.  In all cases there were reductions in SO2 emissions – in some instances greater than that expected solely on the grounds of reduced sulphur content in the biomass.  In some cases increased rates of fouling deposition and slag formation were observed – in some instances decreased fouling deposition rates were decreased. A study of the complex ash chemical changes accompanying combustion was undertaken and the key factors responsible for these behaviours was identified.

Themochemical Recuperative Coal Gasification Combined Cycle using Brown Coal
A Tsutsumi University of Tokyo, Japan; S Bhattacharya CRC for Clean Power from Lignite, Melbourne; J Hayshi and TY Chiba Hokkaido University, Japan
A thermochemical recuperative coal gasification combined cycle (TGCC) has been proposed based on a variation of the integrated gasification combined cycle (IGCC) for the power generation. The cycle uses an oxygen-blown fluidised bed for gasification and a shift-reactor to maximise the production of hydrogen and carbon dioxide.
Thermochemical recuperation can be considered to be energy recycling as a chemical heat pump which upgrades heat at low temperature (such as gas turbine exhaust from  combined cycle) by supplying heat and reactants for endothermic reactions, where subsequently the accumulated energy is released at a higher temperature level during combustion of the combustible gas. In this cycle, part of the gas turbine exhaust gas, is used to heat oxygen and produce steam, both of which are used as reactant in the gasifier, steam only in the shift reactor. Thermal energy held by the exhaust gas is effectively utilised to produce chemical energy of the reformed products, largely H2.and CO2, and to a minor extent CO and CH4. The cycle is expected to be suitable for use with low-rank coals, which have significant proportion of catalytic metallic species, Ca, Na, Mg, and Fe that enhance gasification.
 
This study is part of a collaborative project between researchers in Japan and Australia, and is funded by the New Energy Development Organisation (NEDO) of Japan. This paper briefly discusses the background of the project, and presents results of preliminary simulation of the proposed cycle using commercially available simulation packages. The paper also identifies the areas where scientific research and technical advances are required. A brief discussion is made on the relevant scientific research addressed by various sub- projects.
 
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