Coal Swelling Research Articles

A new theoretical approach to model sorption-induced coal shrinkage or swelling

The shrinkage or swelling of coal as a result of gas desorption or adsorption is a well-accepted phenomenon. Its impact on permeability changes has also been recognized for two decades. Its importance has increased significantly because of the potential of coals that are not likely to be mined and depleted or nearly depleted coalbed methane reservoirs to serve as CO2 repositories. This article proposes a new theoretical technique to model the volumetric changes in the coal matrix during gas desorption or adsorption using the elastic properties, sorption parameters, and physical properties of coal. The proposed model is based on the theory of changes in surface energy as a result of sorption. The results show that the proposed model is in excellent agreement with the laboratory volumetric strain data presented in the literature during the last 50 yr. Furthermore, the proposed model can be extended to describe mixed-gas sorption behavior, which can be applied to enhanced coalbed methane and CO2 sequestration operations.

Injecting pure N2 and CO2 to coal for enhanced coalbed methane: Experimental observations and numerical simulation

Enhanced coalbed methane (ECBM) core flooding experiments are a direct way to observe the gas displacement process, the competitive adsorption and the effect of coal swelling and shrinkage on coal permeability. This study reports two ECBM experiments. In the first experiment, pure N2 is injected (N2-ECBM) to a coal sample saturated with CH4 while, in the second experiment, pure CO2 is injected (CO2-ECBM) to the same coal sample cleaned and resaturated with CH4. We record the volumes and composition of the effluent gas with respect to time. Then the gas rate and gas composition are history matched using a commercial reservoir simulator. The results show that the breakthrough of N2 occurs earlier than CO2 breakthrough (after approximately 0.1day of injection compared to 0.43day). The recovery factor of CH4 is 71% for the N2-ECBM and 86% for the CO2-ECBM at a 10%-molar percentage of CH4 in the produced gas stream. The N2 injection causes moderate increases in coal permeability whereas the injection of CO2 reduces coal permeability significantly. The maximum strain of CO2 injection is higher at the initial stage of CO2 injection but decreases after several days of injection. The extended Langmuir adsorption model predicts the compositional adsorption amounts of N2 and CH4 better for the N2-ECBM than for the CO2-ECBM. A co-optimisation concept is presented to analyse the coupling of ECBM with CO2 storage which shows that early times CO2 storage efficiency is higher than CH4 recovery efficiency. Later CO2 storage efficiency decreases due to CO2 production and CH4 recovery dominates the co-optimisation.

Comparison of high-pressure CO2 sorption isotherms on Central Appalachian and San Juan Basin coals

Accurate estimation of carbon dioxide (CO2) sorption capacity of coal is important for planning the CO2 sequestration efforts. In this work, we investigated the sorption and swelling behavior of several Eastern and Western US coal samples from the Central Appalachian Basin and from the San Juan Basin. The CO2 sorption isotherms have been completed at 55°C for wet and dry samples. The role of mineral components in coal, coal swelling, effects of temperature and moisture, and the error propagation have been analyzed. Changes in void volume due to dewatering and other factors such as caging of carbon dioxide molecules in coal matrix were identified among the main factors affecting accuracy of the carbon dioxide sorption isotherms. The (helium) void volume in the sample cells was measured before and after the sorption isotherm experiments and was used to build the volume-corrected data plots.

Effects of gaseous and super-critical carbon dioxide saturation on the mechanical properties of bituminous coal from the Southern Sydney Basin

A study was initiated to investigate the effects of gaseous and super-critical carbon dioxide (CO2) adsorption on bituminous coal strength. Uniaxial compressive strength (UCS) experiments were conducted on bituminous coal samples from the southern Sydney Basin saturated with gaseous CO2, super-critical CO2 and N2 at various pressures, and a temperature 33°C. According to the results, gaseous CO2 adsorption causes the UCS and Young’s modulus of the bituminous coal to be reduced by up to 53% and 36%, respectively. Super-critical CO2 adsorption causes more significant modifications to the mechanical properties of the bituminous coal, resulting in 40% greater UCS strength reduction and 100% greater Young’s modulus reduction compared to gaseous CO2 adsorption. The greater influence of super-critical CO2 on the UCS of the bituminous coal is thought to be related to the greater adsorptive potential and coal swelling produced for super-critical CO2. The more significant influence of super-critical CO2 on the Young’s modulus of the bituminous coal is thought to relate to the greater dissolution (and thus coal plasticization) potential of the super-critical CO2. N2 saturation was not observed to have any significant effect on the mechanical properties of the bituminous coal. Acoustic emission data collected during testing support of the notion that the coal mass natural cleat system largely contributes to the susceptibility of coal to mechanical weakening by CO2 adsorption. The results show that the mechanical influence of CO2 adsorption on coal is highly dependent on the phase state of the CO2.

Swelling Measurements of a Low Rank Coal in Supercritical CO<sub>2</sub>

Coal swelling in the presence of water as well as CO2 is a well-known phenomenon, and these may affect the permeability of coal. Quantifying swelling effects is becoming an important issue to verify the suitability of particular coal seams for CO2-enhanced coal bed methane recovery projects. In this report, coal swelling experiments using a visualization method in the CO2 supercritical conditions were conducted on crushed coal samples. The measurement apparatus was designed specifically for the present swelling experiment using a visualization method. Crushed coal samples were used instead of block coal samples to shorten equilibrium time and to solve the problem of limited availability of core coal samples. Dry and wet coal samples were used in the experiments because there is relatively limited information about how the swelling of coal by CO2 is affected by water saturation. Moreover, some coal seams are saturated with water in initial reservoir conditions. The maximum volumetric swelling was around 3% at 10 MPa for dry samples and almost half that at the same pressure for wet samples. The wet samples showed lower volumetric swelling than dry ones because the wet coal samples were already swollen by water. Experimental results obtained for swelling were comparable with other reports. Our visualization method using crushed samples has advantages in terms of sample preparation and experimental execution compared with the other methods used to measure coal swelling using block samples.

Quantitative Evaluation for Relationship between Development of Pore Structure and Swelling of Coal in Carbonization of Single Coal Particle

The objective of this paper are to study the formation process of coke pore structure in relation to the swelling of coke during the thermoplastic stage and the pore structure at the initial carbonization. The swelling ratio, changes in pore structure and growth behavior of pore which originally present in the coal were evaluated. Two kinds of caking coals were carbonized in nitrogen-atmosphere with an infrared furnace. The swelling ratios were measured, and the cross-sectional images of coal particles at different heating temperatures were observed with an optical microscope. Before carbonization, all pores in both coals were a diameter of less than 100 μm. When the temperature increased up to the level at which the swelling started, the pores with greater than 100 μm-diameters were formed, and they had also simultaneously coalesced. However, each coal had a different temperature for starting swelling and observing the generation and coalescence of pores with a diameter of more than 100 μm. At this point, the formation of pores were expressed with Laplace equations. The results showed the volatile matter inflow affected the change of pore structure. Furthermore, the pore structures within coal particles before and after carbonization were compared by micro-X-ray Computed Tomography. Carbonization up to the temperature for the softening stage increased pore diameters, which provided evidence that the proportion of pores existing within post-carbonized coal had grown based on the pores already existing in pre-carbonized coal.

CO2 Injectivity in a Multi-lateral Horizontal Well in a Low Permeability Coal Seam: Results from a Field Trial

Enhanced coalbed methane (ECBM) production by CO2 injection offers the potential of increasing recovery of the gas in place over primary recovery methods and at the same time storing CO2. A field ECBM trial via CO2 storage has been carried out in the east margin of the Ordos Basin, Shanxi province, China. A unique aspect of the trial was using a multi-lateral horizontal well, which was clearly beneficial for production or injection for low permeability formations. This paper described a reservoir model constructed to simulate the CO2 injection behaviour using the coal seam reservoir simulator SIMED II. The simulation work included history matching the bottomhole pressure while using injection rate as control. A complexity in the modelling was representation of the multi-lateral horizontal well as its branches were not aligned with x or y coordinates. Thus approximation was taken to represent the well in the model. The simulation result showed good match for some data but could not match well the whole range of data, suggesting possible well opening or closing to flow during injection and shut-in periods. It has been suggested that the permeability decrease due to gas adsorption induced coal swelling may play an important role in the gas flow behaviour, especially near the wellbore where the amount of CO2 adsorbed was highest. However, due to the coarse grid size applied in this finite difference model and the difficulty to refine them near the well branches while maintaining overall size of the model, the permeability loss due to adsorption induced coal swelling was diluted by the relatively large grid size. Thus this may not accurately reflect the permeability change and the quality of the history matching results are affected. A suggestion is to use refined grid blocks near wellbore to examine the impact of swelling on the overall CO2 flow behaviour for this project.

CO2 permeability of Indian bituminous coals: Implications for carbon sequestration

The permeability of coal is one of the most critical parameters in estimating the performance of coal seams as methane reservoirs or carbon dioxide sinks. The reservoir behaviour of coal offers many challenges for the long-term planning of gas production performance and the drainage of water from reservoirs. Moreover, heterogeneity in coal from basin to basin, from seam to seam and within parts of the same seam makes the process more complex. Reservoir-specific understanding is needed for the best possible estimation of its behaviour. Factors such as shrinkage/swelling of coal matrix, gas flow and slippage, geomechanical changes, cleat anisotropy and effective stresses control the flow behaviour of gases in coal. Studies of these aspects have gathered momentum in recent decades for different basins across the world. However, no research is available on swelling-induced permeability characteristics or the role of effective stresses for Gondwana coals in India. Considering the fairly high CO2 storage potential of Indian coals, bituminous coals of the Barakar Formation in Jharia basin, India were tested using gas phase CO2 under triaxial conditions. This paper presents the results of changing effective stresses, in terms of confining stresses and pore pressure, incorporating the role of coal swelling with time on the flow pattern of gaseous CO2. Corresponding to different depths of target coal seams, coal was subjected to different confining stresses in a newly-developed triaxial cell. For each confinement, CO2 was injected at different injection pressures. To minimize the effects of temperature on the characteristics of the gas phase, it was kept constant at 26°C throughout, while use of the drained method of testing maintained the downstream pressure equal to one atmosphere. The results showed that at low confinement, increase in gas injection pressures leads to an initial decrease in permeability of coal, which then becomes almost constant. However, at higher confinements, the permeability increases with increasing injection pressure. Swelling in coal contributes to reduction of permeability. The volumetric expansion in coal reduces the permeability with changing gas injection pressure during the initial confinement. As the confining pressure is increased, coal permeability reduces by one to two orders of magnitude. Finally, an empirical relation accounting for the role of effective stresses and swelling on coal permeability is proposed for Indian coals. At lower effective stresses, the logarithmic decline model is better suited, while the exponential decline relationship fits the data better at effective stresses >12MPa.

Competition between adsorption-induced swelling and elastic compression of coal at CO2 pressures up to 100 MPa

Enhanced Coalbed Methane production (ECBM) by CO2 injection frequently proves ineffective due to rapidly decreasing injectivity. Adsorption-induced swelling of the coal matrix has been identified as the principal factor controlling this reduction. To improve understanding of coal swelling in response to exposure to CO2 at high pressures, numerous laboratory studies have been performed in the past decades. These studies consistently reveal an increase in swelling with CO2 pressure. However, it remains unclear what the relative contributions are of adsorption-induced swelling versus elastic compression of the coal framework, and hence what is the true relationship between adsorption-induced swelling and CO2 uptake.Here, we report the results of dilatometry experiments conducted on unconfined, cylindrical coal matrix samples (∼4mm long and 4mm in diameter) of high volatile bituminous coal, where we aim to measure the effective volumetric effect of CO2 and to separate this into a component caused by adsorption-induced swelling and a component caused by elastic compression. The experiments were performed using a high pressure eddy current dilatometer that was used to measure one-dimensional sample expansion or contraction (resolution <50nm). The tests were conducted at a constant temperature of 40°C, and CO2 pressures up to 100MPa. Our results show that the matrix samples reveal anisotropic expansion over the full range of CO2 pressures used. Expansion perpendicular to the bedding was about 1.4 times the average expansion measured in the bedding plane. Net volumetric strains, which were computed from the net linear strain in all directions measured, reveal that the response of coal is characterised by an expansion-dominated stage below 10–20MPa of CO2 pressure and a contraction-dominated stage at higher CO2 pressures. Our data demonstrate direct competition between adsorption-induced swelling and elastic compression in the coal matrix. We propose a model for coal swelling, which expresses the net volumetric strain as the sum of the adsorption-induced swelling strain and the elastic compression with the adsorption-induced swelling being taken as linearly related to adsorbed CO2 concentration. A comparison of experimentally determined adsorption-induced swelling strain with the adsorbed concentration of CO2 (data Gensterblum et al., 2010) confirms the assumed linear dependence. We go on to compare our experimentally determined adsorption-induced swelling strains to those calculated from an adsorbed concentration model. Good agreement was found over the full range of CO2 pressures up to 100MPa. This shows that combining this thermodynamically based model for adsorbed concentration with the elastic compression of our samples, obtained from their bulk modulus, provides a good description of the measured volumetric behaviour of our samples, and suggests that the physical basis for the model is also valid.The implications of our results for ECBM operations are that compliant coals (low K), which exhibit little adsorption-induced swelling (hence low dependence C), will show relatively small reductions or even increases in permeability due to competition between swelling and compression when CO2 pressure increases during ECBM operations. These coals will tend to be more suitable for ECBM operations. Coals exhibiting high stiffness (K) and high adsorption capacity are less suitable for ECBM.

Method for Simultaneous Measure of Sorption and Swelling of the Block Coal under High Gas Pressure

Carbon dioxide sequestration in unmineable coalbeds combined with enhanced coalbed methane recovery is attracting attention as one of the possible methods for carbon capture and storage. Sorption a...

Coal Swelling Model for Pressurized High Particle Heating Rate Pyrolysis Applications

A model was previously developed to describe the decrease in swelling during coal pyrolysis at atmospheric pressure when maximum particle heating rates increase from 104 K/s to 105 K/s. That model included effects of coal type using chemical structure properties. This paper presents results of new experiments to study the effects of elevated pressure and high heating rates on coal pyrolysis. A pressurized flat-flame burner (PFFB) was designed and built to conduct these studies. The pyrolysis experiments reported in this paper were conducted at particle heating rates of ∼105 K/s and maximum gas temperatures of 1700 to 1900 K at pressures of 1 to 15 atm. Residence times of 25–85 ms were used. A new coal swelling correlation was developed that predicts the effects of heating rate, pressure, and coal rank on the swelling ratio at heating rates above ∼104 K/s. The coal rank index parameters from a previously published atmospheric swelling model were used to model the pressurized swelling data, and a new correl...

Investigation of the influence of coal swelling on permeability characteristics using natural brown coal and reconstituted brown coal specimens

Permeability has been identified as one of the foremost factors that determine the effectiveness of CO2 sequestration in deep coalbeds. Coal matrix swelling can cause a remarkable decrease in the permeability of a coalbed reservoir during the carbon dioxide injection process. The main aim of this paper is to correlate the diametrical swelling percentage with coal permeability. This experimental program further attempts to investigate the effect of gas flow properties in coal due to CO2 sorption. Furthermore, the applicability of using a laboratory-made reconstituted coal specimen for permeability testing has been comprehensively investigated.A laboratory-based experimental program has been carried out using a high pressure triaxial experimental set-up. In this study, the effect of swelling on coal permeability has been investigated using two types of specimens. An intact brown coal specimen cored from a natural coal block and a reconstituted brown coal specimen made by compacting coal dust in a mould has been subjected to testing. Tests have been carried out under different gas injection and confining pressures. CO2 and N2 gases have been used as injection media. Gas injection has been carried out with two stages of N2 injection, prior to and after CO2 injection.Diametrical swelling of the two specimens has been compared with the permeability data. A good correlation was observed between permeability and coal swelling. The coal swelling percentage increased on exposure to carbon dioxide compared to exposure to N2. This effect increased as gas injection pressure increased. Exposure of the coal specimens to CO2 has contributed to a detrimental effect on permeability. This was clearly evident during the second injection of N2 gas.

Modeling and Simulation of Moisture Effect on Gas Storage and Transport in Coal Seams

It has been observed in a series of experiments that the presence of moisture in the coal matrix has profound influences on the gas storage and transport in coal seams by reducing the gas adsorption capacity of the coal, decreasing the gas effective diffusivity through the coal matrix, and varying the coal swelling strain. A striking piece of evidence of the loss of moisture content in field is the increasing dustiness during the ventilation in coal mining, and this may definitely affect the gas production. However, the combined effect of these processes on coalbed methane production has not been studied in previous works. Therefore, an initial reservoir simulation model has been constructed to investigate the magnitude and interplay of the moisture effect on coalbed methane production. To develop the aforementioned model, approximate relationships have been built to quantify the moisture effect on the gas adsorption capacity, the gas effective diffusivity and the coal swelling strain. These relationships...

Swelling of coal in carbon dioxide, methane and their mixtures

Abstract Swelling of coal, especially in the presence of CO 2 , may reduce the permeability of coal seams thus affecting the viability of enhanced coalbed methane production or CO 2 sequestration operations. In this paper we report laboratory measurements of swelling in four Australian bituminous and sub-bituminous coals in CO 2 , methane and various mixtures of the two gases. Measurements were made on unconstrained monolithic samples at 55 °C and at pressures up to about 15 MPa. Volumetric swelling at 15 MPa ranged from about 1.9% to 5.5% in CO 2 and 1.0% to 2.5% in CH 4 depending on the rank of coal and the proportion of CO 2 in the gas mixture. Swelling measurements made at a constant pressure of 15 MPa but with varying gas composition showed that even CO 2 with a high affinity for coal could be completely displaced by helium, which does not adsorb, causing the coal sample to shrink to its original dimensions. Similarly, CH 4 was displaced by injecting CO 2 into the system which then caused the coal to swell to the same level as if it had been exposed to pure CO 2 . The results of these experiments show that there is no enhanced swelling in mixed gases above that would be observed in the pure CO 2 at the same total pressure. As well, the swelling behaviour of coal in mixed gases was determined solely by the partial pressure of the sorbing gas so that weakly or non-sorbing gases are effective at displacing strongly adsorbed gases.

Adsorption-Induced Deformation of Microporous Materials: Coal Swelling Induced by CO2–CH4 Competitive Adsorption

Carbon dioxide injection in coal seams is known to improve the methane production of the coal seam, while ensuring a safe and long-term carbon sequestration. This improvement is due to the preferential adsorption of CO(2) in coal with respect to CH(4): an injection of CO(2) thus results in a desorption of CH(4). However, this preferential adsorption is also known to cause a differential swelling of coal, which results in a significant decrease in the reservoir permeability during the injection process. Recent studies have shown that adsorption in coal micropores (few angströms in size) is the main cause of the swelling. In this work, we focus on the competitive adsorption behavior of CO(2) and CH(4) in micropores. We perform molecular simulations of adsorption with a realistic atomistic model for coal. The competitive adsorption is studied at various temperatures and pressures representative of those in geological reservoirs. With the help of a poromechanical model, we then quantify the subsequent differential swelling induced by the computed adsorption behaviors. The differential swelling is almost insensitive to the geological temperatures and pressures considered here and is proportional to the CO(2) mole fraction in the coal.

Modeling of coal swelling induced by water vapor adsorption

Gas adsorption-induced coal swelling is a well-know phenomenon. Coal swelling or shrinkage by adsorption or desorption of water vapor has not been well understood but has significant implications on gas drainage process for underground coal mining and for primary and enhanced coalbed methane production. Decreased matrix moisture content leads to coal shrinkage and thus the change of cleat porosity and permeability under reservoir conditions. Unlike gas adsorption in coal which usually forms a single layer of adsorbed molecules, water vapor adsorption in the coal micropores forms multilayer of adsorbed molecules. In this work, a model has been developed to describe the coal swelling strain with respect to the amount of moisture intake by the coal matrix. The model extended an energy balance approach for gas adsorption-induced coal swelling to water vapor adsorption-induced coal swelling, assuming that only the first layer of adsorbed molecules of the multilayer adsorption changes the surface energy, which thus causes coal to swell. The model is applied to describe the experimental swelling strain data measured on an Australian coal. The results show good agreement between the model and the experimental data.

Synergistic effects on co-pyrolysis of lignite and high-sulfur swelling coal

Co-pyrolysis of a lignite coal and a bituminous coal was carried out on a fixed-bed reactor. The lignite was enriched with calcium, and the bituminous coal featured in high sulfur and strong swelling. Experiments were also conducted for the blends using the acid-washed lignite and/or the acid washed bituminous coal to address the influences of calcium in the lignite on the synergistic behaviors. Calcium in the lignite exhibited some aspects of synergy including the catalytic cracking reactions of tar, the retention of sulfur in the char, and the catalyzed polyaromatization and gasification of char. These synergies impacted the differences in the product distribution and gas composition between the co-pyrolytic results and the additive ones. Moreover, there appeared to be a synergistic effect on the cross-linking reaction of volatile matter, resulting in an increase in the char yield irrespective of coal demineralization. The co-pyrolysis was also observed to destroy the swelling of coal. This synergistically increased the tar yield due to less resistant escaping of tar from the intra-particles of coal.

Modeling and Upscaling of Binary Gas Coal Interactions in CO2 Enhanced Coalbed Methane Recovery

Abstract When CO 2 injected into the unmineable coal seam, complicated binary gas CH 4 -CO 2 coal interactions affect coal porosity and permeability, which is one of the bottleneck scientific issues faced in enhancing production of coalbed methane and the geological sequestration of carbon dioxide. The issue is addressed through the development and application of a novel fully coupled coal deformation, gas transport and gas adsorption/desorption finite element (FE) model with COMSOL Multiphysics. The COMSOL FE model considers the combined net effects on coal permeability among the coal matrix swelling/shrinking due to gas displacement, pore pressure and in-situ stress. These combined effects are quantified through solving a set of coupled field equations which govern the coal deformation, prescribe the transport and interaction of gas flow in a similar way to poroelastic theory, and define CH 4 -CO 2 counter diffusion and flow in a coal seam. Numerical models were verified with the experiment data. The established COMSOL FE simulator was applied to simulate the CO 2 injection performance in Qinshui Basin field under in-situ size and conditions, to address in-situ spatial-temporal evolutions of coal deformation and permeability. Simulation results suggest that net change of coal permeability accompanying binary gas dispersion is controlled competitively by the influence of effective stresses and differential swelling of coal. 1.75×10 4 t CO 2 can be sequestrated in 300×300 m 2 area of Qinshui Basin within 10 years. During the simulation, coalbed methane recovery was promoted by 1.44 times.

Numerical studies on the effects of water presence in the coal matrix and coal shrinkage and swelling phenomena on CO&lt;SUB align= �right �&gt;2-enhanced coalbed methane recovery process

Conventional coalbed methane (CBM) models are developed using dual-porosity, single-permeability domain characteristics, which ignore the effects of water presence in the coal matrix. Neglecting these effects typically over-predicts gas production. Another phenomenon often disregarded in most CBM models is the coal shrinkage and swelling effects, which cause changes in coal permeability. This study illustrates how the water presence in the coal matrix and coal shrinkage and swelling phenomena affect the CO2-enhanced CBM recovery process. An in-house two-phase, fully-implicit, compositional, dual-porosity, dual-permeability CBM simulator accounting for the effects of water presence in the coal matrix and coal shrinkage and swelling, is used in this analysis. Results demonstrate the water presence in the coal matrix caused an early CO2 breakthrough. A decrease in fracture permeability caused by the dominating effects of coal swelling delays the CO2 breakthrough. Ignoring these effects could provide significant errors of production predictions of enhanced CBM recovery process.

The effect of perchloroethylene on coking properties

A two-stage study was undertaken to establish what effect, if any, perchloroethylene has on coal coking properties. Stage 1 was a kinetic study in which the Gieseler fluidity of samples of a high fluidity coal was measured over a 64-week period. Two of the samples were left untreated, with one stored in air and one immersed in water. The third sample was also stored in air, but was soaked in perchloroethylene for 2h and then air dried immediately prior to fluidity testing. In Stage 2, seven different coking coals were studied, covering three different Australian coal measures and a wide range of coking rank. For each coal, a 40kg clean coal composite was formed using laboratory water-based methods, a Reflux Classier for the 0.038–0.25mm and 0.25–2.0mm size fractions and a Mintek jig for the 2.0–16 and 16–50mm size fractions. This 40kg composite was then subdivided into four sub-samples. Samples A and B were coked immediately, whereas Samples C and D were stored in open trays at ambient conditions for a month before coking. Samples B and D were soaked in perchloroethylene for 2h and then air dried prior to coke testing, whereas Samples A and C were left untreated. Coal properties were measured prior to coking, and after coking the NSC Coke Reactivity Index (CRI) and Coke Strength after Reaction (CSR) were measured.In Stage 1 it was found that storage under water was able to maintain the sample fluidity better than refrigerated storage. The combined Stage 1 and 2 results showed that perchloroethylene had a detrimental effect on the coking properties of many coals. Hence coking tests on clean coal composites formed using heavy organic liquids may often under predict a coal’s true coking properties. This could lead to many coal deposits being undervalued. Perchloroethylene had the largest detrimental effect on the fluidity, CRI and CSR of coals that started with relatively poor properties. Perchloroethylene had a negligible effect on coals with relatively good initial coking properties. There was no clear correlation with vitrinite reflectance. The three most seriously affected coals all had relatively high inertinite content. It is speculated that the higher porosity of inertinite might allow greater access and retention of perchloroethylene in the coal particles.The laboratory water-based methods were able to produce clean coal composites that matched the proximate, petrographic and coal swelling number properties of the coal preparation plant product. The dilatometer and fluidity results were lower than those of the coal preparation plant, but this can be explained by the up to three month delay between mining of the original sample and the coking of the composite. These delays were an unavoidable part of the research nature of this project and had nothing to do with the water based methods deployed. If these water-based methods of preparing clean-coal composites were to become standardized, then there is no reason why a well equipped coal testing facility could not receive a refrigerated bore core and produce a clean coal composite within the period of a week.