Introduction

Energy analysis may follow one of several paths. One path is the heat or energy balance which follows the energy conservation principles of the first law of thermodynamics, that is, the sum of the energies of all inputs equals the sum of the energies of all outputs. This path is well suited to those sections of the chemical and metallurgical process industries where the flow-sheet is effectively linear with few recyles, there are only simple energy recovery systems and there are few transformations between the different forms of energy such as chemical, heat, mechanical and electrical.

For those sections of the chemical and metallurgical process industries where the flow-sheet is complex with many recycles, there is a highly integrated network of energy recovery and/or there are transformations between chemical, heat, mechanical and electrical energy, then the energy analysis principles of the second law of thermodynamics which embodies the concept of energy quality should be followed. Appropriate situations for second law analysis include cogeneration, combined cycles, fuel cells, electrolysis and heat exchange networks. Second law energy analysis is able to quantitatively calculate the effect of the process environment on process energy efficiency, that is, the difference in process performance in different locations, in different seasons, in different weather conditions and/or at different times of day.

Austherm Pty Ltd personnel are familiar with both the above techniques of energy analysis and the situations in which they are most appropriately applied. Austherm have made it their business to have access to the physical property data required to make these energy analyses and to the computer software which can most efficiently access the data and perform the task. Austherm is one of the few organisations possessing general computer software capable of using thermochemical databanks and a choice of defined reference environments for second law energy analysis.

The following papers indicate some of Austherm's capabilities:

A.G. Turnbull and M.W. Wadsley, "Energy Analysis of Processes by the CSIRO-SGTE THERMODATA System", in Proceedings, Australian Institute of Energy National Conference, Melbourne, 27-29 Aug. 1985 (Australian Institute of Energy, Sydney, 1985), vol. 1, paper no. 22, pp. 285-296.

M.W. Wadsley "First and Second Law Analysis of Processes", Monash University, Melbourne, Victoria, Australia, Master of Engineering Science thesis in the Department of Chemical Engineering, 1984.

M. Wadsley, "Metals and Energy Options", in M. Diesendorf (Ed.), Energy and People: Social Implications of Different Energy Futures, proceedings of the National Conference on Energy and People, Canberra, 7-9 Sept. 1978 (Society for Social Responsibility in Science, Canberra, 1979), pp. 167-169.

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Greenhouse Carbon Dioxide

0. Recovery of Carbon Dioxide
Carbon dioxide is a product of complete combustion of carbonaceous material, such as many fuels, and hence is a component of their combustion flue gases. Carbon dioxide is frequently a component of fermentation and other biological process off-gases. Carbon dioxide is also a component of many naturally occuring gases, including air.
We believe that we have available the physical and chemical property information needed to evaluate and design many of the various options that may be used to recover carbon dioxide from natural and artificial gas mixtures. We are aware of much of the technology that may be used to recover carbon dioxide. We also have available the information needed to calculate other effects associated with particular options for carbon dioxide recovery.

1. Temporary Ocean Disposal
Because the oceans are a natural sink for about half of the atmospheric carbon dioxide emissions, it is believed that temporary direct ocean disposal of carbon dioxide would reduce the maximum or peak concentration that carbon dioxide might attain in the atmosphere and hence reduce the extent of climatic changes. As the residence time of carbon dioxide in the oceans is finite, the oceans cannot be considered to be a permanent sink for carbon dioxide. Sustainable energy policies must be implemented in conjunction with ocean disposal. Papers describing ocean disposal of carbon dioxide are listed below.

M.W.Wadsley, "Thermodynamics of Multi-Phase Equilibria in the CO2-Seawater System" pp.195-216 in Handa,N. and Ohsumi,T. Eds, "Direct Ocean Disposal of Carbon Dioxide" Terrapub, Tokyo, 1995.

M.W.Wadsley, "Thermodynamics of Multi-Phase Equilibria in the CO2-Seawater System" ICO-2 Second International Symposium on Interaction between CO2 and Ocean, Tsukuba, Japan, 1-2 June, 1993.

T.R.A. Davey and M.W.Wadsley "Sea Water Dissolution - An Interim Solution to Industrial Carbon Dioxide Emissions" pp.33-38 in "Mineral Fuels and the Greenhouse Effect Seminar" 25-27 July, 1989, Aus.I.M.M., Melbourne

2. Sequestration and Geosequestration of Carbon Dioxide
Carbon dioxide may react with particular natural minerals to form stable solid products, a process known as non-reductive sequestration. Carbon dioxide may react with other natural minerals to form reduced products, a process known as reductive sequestration.
We believe that Austherm Pty Ltd have available the physical and chemical property information needed to evaluate and design the various sequestration process options, including calculating the mineral volume changes involved. Austherm have used their data to study the chemical equilibria involved in sequestration and geosequestration.

3. Sustainable Recycling of Carbon Dioxide
A sustainable energy cycle could involve the use of solar- derived energy to convert carbon dioxide into fuels and petrochemicals. Austherm Pty Ltd principals have investigated the conversion of carbon dioxide into methane or into formic acid which may be considered to be an energy- rich intermediate to be used in the production of a variety of fuels and chemicals. The main strength of this approach is its ease of integration with existing industrial and domestic infrastructure. This concept was described in the paper given below.

3(a). Formfuel
Go to AUSTHERM Pty Ltd Formfuel Page

M.W. Wadsley, "The FORMFUEL Process" preprint of a paper presented at the 1980 ANZAAS Congress, University of Queensland, 1980

3(b). Sustainable Methane from Atmospheric Carbon Dioxide
Some metal carbonates react chemically with hydrogen gas to form methane plus the metal oxide or the metal hydroxide.

MCO₃ + H₂ = MO + CH₄ + H₂O
MCO₃ + H₂ = M(OH)₂ + CH₄ + H₂O

Some metal oxides and/or metal hydroxides react with carbon dioxide in the Earth's atmosphere to form metal carbonates thus providing a means of carbon capture.

MO + CO₂ = MCO₃
M(OH)₂ + CO₂ = MCO₃ + H₂O

Combination of this chemistry with the electrolysis of water using solar-derived electricity to obtain hydrogen gas leads to a sustainable process for the production of methane, that is, synthetic natural gas.

The carbon in some metal carbonates, such as nickel carbonate and cobalt carbonate, may be converted to methane by hydrogenation without the addition of catalysts but the resulting metal oxides have insufficient affinity for carbon dioxide to form metal carbonates when exposed to the atmosphere. However some of these metal carbonates, such as nickel carbonate and cobalt carbonate, have significant solid-solubility in other metal carbonates, such as magnesium carbonate and calcium carbonate, whose oxides do have a strong affinity for carbon dioxide. It is probable that intimate mixtures of metal carbonates, such as calcium carbonate plus nickel carbonate or calcium carbonate plus cobalt carbonate or magnesium carbonate plus nickel carbonate or magnesium carbonate plus cobalt carbonate, may be effective in this methane producing process and would avoid the need for expensive precious metal catalysts for hydrogenation.

The water for electrolysis could be absorbed from the Earth's atmosphere and from the product methane using concentrated aqueous solutions of lithium chloride or lithium bromide or zinc chloride.

Sulfuric acid or phosphoric acid could be used as the water electrolysis medium.

A process based on the above chemistry and engineering could be located in dry, sunny regions and would not compete with land or resources used for food production or human habitation. Some such regions also have existing methane reticulation pipelines and infrastructure.

Bibliography

Yoshida N.; Hattori T.; Komai E.1; Wada T.
"Methane formation by metal-catalyzed hydrogenation of solid calcium carbonate"
Catalysis Letters, Volume 58, Numbers 2-3, 1999 , pp. 119-122(4)

Tsuneto, Akira ; Kudo, Akihiko ; Saito, Nobuhiro ; Sakata, Tadayoshi
"Hydrogenation of Solid State Carbonates."
Chemistry Letters. 1990, S. pp.831–834

John Emsley
"Let them burn limestone . . ."
New Scientist Print Edition 05 September 1992

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Steam Systems

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Hydro-Geochemistry

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