CCSU - A Hopeful Carbon Dioxide Solution   

By Xia Lei, ASIACHEM   

Carbon dioxide emitted from the use of coal has been luring more and more concerns from various sectors. Such emissions can be produced either by the direct combustion for power generation or by the conversion of coal to other fuels and chemicals. To reduce the impact of carbon dioxide emissions on environment, carbon capture & storage (CCS) is becoming a highlight by both scientific and industrial experts. Presently CCS is always involved in expensive cost, the carbon dioxide utilization is expected to make benefit, at least offsetting part of the cost incurred from the emission reduction. That is the reason ASIACHEM believes in that the carbon capture, storage & utilization (CCSU) will emerge as a new business.

Captured and concentrated carbon dioxide can be used in enhanced oil recovery (EOR)

Injection of carbon dioxide into the exhausting oil field may raise the yield of remaining oil. Although a small part may enter into the air in the process, most of carbon dioxide can be sequestered in oil well. This is a quite proven process but a gap still exists between the capture cost and the price acceptable to most oil companies. In China, the cost of carbon dioxide capture is between US$60/t and US$80/t whereas the price acceptable by PetroChina Company Limited is US$20/t only for its crude oil production.
   Xinjiang region of China is rich in oil, gas and coal. A lot of crude oil production, refining, petrochemical as well as coal chemical projects are under planning or construction. The carbon dioxide captured from the petrochemical and coal chemical production can go back to improve the crude yield, which is of glorious prospect and comply with the sustainability.

Use of carbon dioxide in enhanced coal bed methane (ECBM)  

The adsorption of carbon dioxide by coal is far stronger than the adsorption of methane, which make carbon dioxide replace the adsorbed methane in coal bed, improving the yield of coal bed methane. Multiple researches on ECBM are under way worldwide. For instance, China United CBM Co., Ltd. is carrying out a small size prototype carbon dioxide-ECBM test, jointly with Canadian ARC and Sploure, in TL-003 well of Qinnan Coal Field.

Chemical use of carbon dioxide

Carbon dioxide is of weak reactivity, many researches have, however, been carried out on possible chemical conversions of the gas into many other chemicals. In August 2008 Japan based Mitsui Chemicals announced to invest US$13.6 million in constructing a carbon dioxide-to-methanol demonstration unit. The unit will be able to convert 150 - 160 t/a of carbon dioxide into 100 t/a of methanol, the latter can be used to produce ethylene, propylene and aromatics etc. Mitsui predicted it will accomplish the whole package development by March 2010.
    A trans-esterification process to produce dimethyl carbonate (DMC) and monoethylene glycol from carbon dioxide, methanol and ethylene oxide, developed by East China University of Science & Technology, has been employed in many commercial plants in China.  
    Use of carbon dioxide and epoxy compound in plastics production has been demonstrated in China at a commercial scale, and four demonstrative plants were constructed in Inner Mongolia region, Henan, Jiangsu and Hainan provinces respectively.
    To the belief of ASIACHEM, economic and large scale chemical use of carbon dioxide will remain a great challenge in a long term. CCSU will emerge as a hopeful solution for the carbon dioxide emissions from coal utilization processes.