James H. Edwards

Potential sources of CO2 and the options for its large-scale utilisation now and in the future

Abstract The current emissions of CO2 to the atmosphere through man-made activities are outlined and the options for recycling CO2 for some useful purpose, as distinct from simply storing or disposing it in an environmentally-benign manner, are discussed. It is shown that for CO2 recycling to have any significant impact on reducing emissions of this gas, it must form part of some large-scale energy conversion process which is based on a non-fossil-fuel energy source such as solar or nuclear energy. Since the quantities of undiluted CO2 available for recycling are relatively small, the cost of recovering CO2 from sources such as power station flue gas must be taken into account in the overall CO2 recycling/energy conversion scheme.

Flash pyrolysis of coals: behaviour of three coals in a 20 kg h−1 fluidized-bed pyrolyser

Abstract Flash pyrolysis of Loy Yang brown coal, and Liddell and Millmerran bituminous coals has been studied using a fluidized-bed reactor with a nominal throughput of 20 kg h−1. The apparatus and its performance are described. The yields of tar and hydrocarbon gases are reported for each coal in relation to pyrolysis temperature, as also are analytical data on the pyrolysis products. The peak tar yields for the dry, ash-free Loy Yang and Millmerran coals were respectively 23% wt/wt (at ≈ 580 °C) and 35% wt/wt (at

13C n.m.r. aromaticity balance on the products from flash pyrolysis of five Australian coals

600 °C). The tar yield from Liddell coal was 31% wt/wt at ≈ 580 °C. Hydro-carbon gases were produced in notable quantities during flash pyrolysis; e.g. Millmerran coal at 810 °C gave 6% wt/wt (daf) methane, 0.9% wt/wt ethane, 6% wt/wt ethylene, and 2.5% wt/wt propylene. The atomic H C ratios and the absolute levels of hydrogen in product tars and chars decreased steadily with increasing pyrolysis temperature.

Upgrading of flash pyrolysis tars to synthetic crude oil: 1. First stage hydrotreatment using a disposable catalyst

The carbon aromaticity of five Australian coals and their flash pyrolysis products was measured by 13C solidstate n.m.r. In all cases, the products contained the same or more aromatic carbon than the coals. The amount of aliphatic carbon converted to aromatic carbon varied from ≈ 0–32%. The variability in the extent of aliphatic carbon aromatization may be due to the different amounts of hydroaromatic or long-chain aliphatic carbon in these coals. For some flash pyrolysis tars, direct measurements of aromaticity by crosspolarization, solid-state 13C n.m.r. are erroneous. This is due to mobile CH2 material in the tar, which has a TCH longer than the T1ϱH of the rest of the tar, so that accurate measurements of aromaticity must be made by Bloch decay methods.

Reaction engineering studies of methane coupling in fluidised-bed reactors

Abstract The hydrotreatment of tars produced by flash pyrolysis of Millmerran (subbituminous), Loy Yang and Yallourn (both brown) Australian coals was investigated in a continuous reactor containing a packed bed of sulphided steelwool. Reactor performance and product yields are reported for each tar. Overall mass balances of 96.7–100.3% and carbon balances of 96.0–100.2% were achieved. Recovered yields of product oil were 82.7–86.8%, 62.1% and 75.5% wt/wt dry, char-free tar for Millmerran, Loy Yang and Yallourn tars respectively. The steelwool reactor was found to decrease the coking propensity, specific gravity, viscosity and heteroatom levels and to increase the hydrogen content of the tars. It also acted as a filter to remove the char fines present in the tar. The operating life of the reactor was limited by the build up of carbonaceous deposits within the steelwool.

Flash pyrolysis of coals: comparison of results from 1 g h−1 and 20 kg h−1 reactors

Abstract The oxidative coupling of methane has been conducted in 30 and 60mm dia. fluidised-bed reactors. Methane conversions as high as 40% were achieved at isothermal conditions using methane/oxygen mixtures without diluents. At the same contact time the two reactors had similar selectivities to hydrocarbons. At 850°C the hydrocarbon selectivity decreased dramatically with increasing contact time but this effect was much less severe at lower temperatures. Axial gas concentration profiles through the catalyst bed in the 60mm reactor indicated that at 850°C there was a rapid consumption of oxygen and formation of products in the bottom section of the bed followed by a net loss of hydrocarbon in the oxygen-free zone. This loss was due to carbon formation on the catalyst which was circulated back to the oxygen-containing zone of the bed where the carbon was combusted.

Upgrading of flash pyrolysis tars to synthetic crude oil: 2. Second-stage hydrotreatment using nickel/molybdenum catalysts

The performances of 1 g h−1 and 20 kg h−1 flash pyrolysers are compared for three Australian coals: Loy Yang brown coal (Victoria), Liddell bituminous coal (New South Wales), and Millmerran sub-bituminous coal (Queensland). The two reactors gave comparable yields of tar, char and C1–C3 hydrocarbon gases over a range of operating conditions for each particular coal. The yield of total volatile matter from Millmerran coal was similar from both reactors, as were the compositions of chars from Loy Yang coal and tars from the Liddell and Millmerran coals. For Millmerran coal, the yields of tar, C1–C3 gases and volatiles from the large reactor below 650 °C, were slightly lower than for the small reactor, possibly owing to a shorter retention time of Millmerran coal particles in the large-scale reactor. At a temperature near 600 °C tar yields were independent of tar concentration in the effluent gas, over a range 0.0025–0.1 kg m−3 for Liddell coal, 0.005–0.26 kg m−3 for Millmerran coal and 0.0045–0.09 kg m−3 for Loy Yang coal. The tar yields from Millmerran and Liddell coals at 600 °C in the large reactor, correlate directly with the atomic HC ratio of the parent coal, in the same manner as that found for a wider range of bituminous coals in the small-scale reactor.

Upgrading of flash pyrolysis tars to synthetic crude oil: 3. Overall performance of the two-stage hydrotreating process and characterization of the synthetic crude oil

Abstract Flash pyrolysis tar, produced from Millmerran coal and pretreated over a packed-bed of steelwool to reduce coking propensity, was hydrotreated in a trickle-bed reactor containing conventional nickel/molybdenum catalyst. The effect of reaction temperature on reactor performance and on the yield and nature of the products was investigated within the range 367–420°C. Increasing temperature resulted in substantial reductions in heteroatom content and coking propensity of the product oil and increased yields of

The reforming of methane with carbon dioxide - current status and future applications.

Abstract Overall performance data are presented for the hydrotreatment of Millmerran flash pyrolysis tar in a twostage reactor incorporating sulphided steelwool and commercially available hydrotreating catalysts. Recovered yields of product oil ranged from 70–82 wt% of the tar input, which are equivalent to 25–29 wt% of the dry, ash-free coal fed to the pyrolyser. Analytical data for the product oils show that they have similar properties to crude oil. Consequently it should be technically feasible to produce transport fuels from these materials using available petroleum-refining technology. The major operational problem encountered in this work was the build up of carbonaceous deposits in the catalyst beds, which seriously limited the operating life of both reactors.

The OXCO Process: The Direct Conversion of Natural Gas to Olefins and Liquid Fuels Using Fluidized-Bed Technology

Publisher Summary The reforming of CH 4 with CO 2 to produce synthesis gas with a H 2 /CO ratio of around 1 has to date had no commercial application by itself. It has, however, been used in conjunction with the widely applied stedCH 4 reforming process when the H 2 CO ratio of the product gas is required to be less than that generated by steam reforming alone. In certain potential applications (e.g. energy storage and transmission) CO 2 /CH 4 reforming has a number of advantages over steam reforming, and is likely to become an increasingly important industrial reaction in the future. This chapter reviews the current status of research on the development of catalysts and reactor technology for CO 2 /CH 4 reforming. It also outlines the current and future applications for CO 2 /CH 4 reforming with particular emphasis on its impact on future energy conversion technologies and implications for achieving reductions in Greenhouse Gas emissions.