Defining CCS Ready: An Approach to An International Definition

Appendix B: Technology Design Options for a Capture Ready Plantconcentration of approximately 55%. 151 Some systems use an amine system to recovernearly pure CO 2 , which is sold for use in beverages or dry ice. Facilities with an aminesystem will be in a position to supply CO 2 directly for compression for transport. Otherfacilities would need to add an amine unit or other system to purify the CO 2 for transport.Since hydrogen is typically produced at large chemical facilities, the required infrastructure(e.g., steam) would likely be available, though space limitations could be a consideration.Natural Gas ProcessingNatural gas leaving the well contains a variety of impurities and contaminants that must beremoved before the gas can enter the gas pipeline system. These include water, heavierhydrocarbons, CO 2 , and H 2 S, among others. Liquids can be removed at the wellhead, butgaseous components are removed at a natural gas processing plant using a variety ofcompression and sorbent technologies. The CO 2 content of the raw gas varies according tothe geological source. In some cases it can be quite low, while other sources are very high.In most gas processing plants, the CO 2 and H 2 S are removed via amine sorbent systems andthe CO 2 is vented from the plant. In some cases, the CO 2 is transported by pipeline for usein enhanced oil recovery. In some cases, the CO 2 and H 2 S are reinjected as a means ofdisposing of the H 2 S. Depending on the make-up of the raw gas and the specific CO 2removal technology, a gas processing plant may already have very pure CO 2 , which is mostlikely being vented. In many cases this stream could be ready for transport and storage, as ishappening in some cases. One important question is the tolerance of the pipeline forcontaminants such as H 2 S. As noted above, some systems already handle mixed CO 2 andH 2 S streams; however, this might not be the case for a CCS system. In this case, the gasprocessing plant output might need additional purification.B.4.2 High Concentration SourcesThe most significant industrial source of high-concentration CO 2 streams is cement and limeproduction. Both cement and lime production involve the heating of calcium carbonate rock(CaCO 3 ) in a cement kiln at a temperature of about 1,450°C (2,400°F) to form lime (i.e.,calcium oxide or CaO) and CO 2 in a process known as calcination or calcining. In cementproduction, the lime is later combined with silica-containing materials to produce clinker (anintermediate product). The clinker is then allowed to cool, mixed with a small amount ofgypsum, and potentially other materials (e.g., slag) and used to make Portland cement. Limeis an important manufactured product with many industrial, chemical, and environmentalapplications. Its major uses are in steel making, flue gas desulfurization (FGD) systems atcoal-fired electric power plants, construction, and water purification.Cement and lime are relatively low-cost commodities. Since the raw material for cement andlime production as simply ground-up rocks, the energy input to the process is a key factor inproduction cost and profitability. Thus, lime and cement kilns have typically been fuelled withthe lowest-cost available fuels, most often coal and sometimes even hazardous waste.The cement kiln is basically an inclined tube in which the combustion products pass directlyover and through the carbonate rock to heat it. The exhaust gas contains the CO 2 from fuel151 Spath, P.L., & Mann, M.K.. (2001). Life cycle assessment of hydrogen production via natural gas steam reforming(Report no. NREL/TP-570-27637). Golden, CO: National Renewable Energy Laboratory (NREL).23 February 2010 97