Geo-Sequestration

Prior to geo-sequestration, the carbon dioxide has to be available in a concentrated form so that it can be compressed and liquefied prior to disposal. From the standpoint of the petrochemical industry, there are two types of emissions which we need to consider. The first type is when carbon dioxide is extracted from a process stream by typically dissolving the carbon dioxide in a solvent. Here the carbon dioxide is available as a 

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Carbon geo-sequestration where all or part of carbon dioxide is captured and stored in deep geological formations. 

For geo-sequestration of carbon dioxide in flue gas it may be necessary to first remove sulphur so as to protect the carbon dioxide solvent. The flow from the flue system has to be modified to include an additional plant prior to compression, carbon dioxide and geosequestration as illustrated by Figure 6.3. 

Some guidance to the cost of carbon geo-sequestration is obtained by consideration of the costs of using carbon dioxide in enhanced oil recovery schemes . This is in the region of 20-25/tonne of carbon dioxide after purchase of the gas for this duty. 

In order to give an informative account of the likely cost of carbon abatement of the various petrochemical operations, the carbon emissions have been estimated and a fixed variable relationship developed with carbon dioxide disposal cost as the variable. This cost can be either the cost of geo-sequestration facilities, the cost of purchasing emissions certificates or carbon tax. 

At the time of writing this about double the traded emissions cost for carbon dioxide but much less than the cost of disposal by geo-sequestration. 

As a consequence of this, there is now a major focus on the use of coal as a source for fuels and olefins. Coal has a far higher level of carbon than petroleum fuels and natural gas and this inevitably leads to higher emissions of carbon dioxide in the production of fuels and olefins. As a consequence there are research and development projects concerned with the capture of carbon dioxide from coal based operations and the geo-sequestration of the carbon dioxide. 

Hydrogen sulphide can be either passed to a Claus unit" with the duty to convert the hydrogen sulphide to sulphur or mixed with the carbon dioxide for geo-sequestration. This latter system is in operation at the Dakota Coal Gasification plant in the USA with carbon dioxide and hydrogen sulphide passed by pipeline to a geo-sequestration facility in Canada. 

Ho MT, Alhnson G and WUey DE (2006), Comparison of CO2 separation options for geo-sequestration are membranes competitive . Desalination, 192,288-295. 

Computational Models for CO2 Geo-sequestration Compressed Air Energy Storage Editors Rafid Al-Khoury Jochen Bundschuh 2014... 

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