CO2 capture from other industrial sources

CO2 from industrial processes  have yet to be tested on a large scale, apart from in natural gas sweetening. Different processes produces flue gas with widely different pressure and CO2 content. Different processes must therefore be considered individually for viability of CO2 capture.

Many of the major industrial emission sources have characteristics that make them suitable for CO2 capture, mainly in terms of average emissions pr source and CO2 partial pressure of the exhaust flue. However, technical feasibility in each case depends on the layout of the industrial plants in question. High complexity in plant architecture may make post-fitting of capture technology challenging.

Contents

1. Cement production
2. Oil and gas processing
3. Steel Production
4. Ammonia production
5. Other processes
6. See also 

Cement production 

Production of cement is the largest industrial source of CO2 emissions apart from the power sector, accounting for about 1000 MtCO2 pr year. Cement production, involving the calcination of limestone, has large process emissions of CO2. In addition, large large quantities of heat energy is needed to drive the process and this usually comes from fossil fuels.

The concentration of CO2 in the flue gases from cement production is 15-30% by volume, considerably higher than from fossil fuel power plants. Therefore, post-combustion capture technologies can be applied to cement production plants, but would require additional generation of steam for the capture process. 

Oil and gas processing

Oil refinery

Emissions from the processing of natural gas and from oil refineries account for about 850 MtCO2 pr year. The majority of these emissions come from oil refineries, with a small fraction coming from the removal of CO2 and other impurities from produced natural gas. Oil and gas processing emissions are likely to increase in the future as the production of unconventional oil and gas increases. Refining unconventional oil, such as bitumen produced from tar sand, may cause considerably higher emissions than refining conventional oil.

Emissions from refineries come from a multitude of sources. Emissions from the generation of electric energy, heat energy and steam used in the various process on the plant and emissions from the production of hydrogen from natural gas would be most viable for capture. Also, some direct process emissions may be viable.

Production of energy and steam at a refinery is very similar to the energy generation in the power sector, so in principle most capture methods suitable for power plants could feasibly be integrated into a refinery. Limits in plant area and specific needs in modes of energy delivery may limit the options, however.

Additional CO2 may be captured by collecting exhaust  gas streams from all emission sources at the refinery and transporting them to one or several capture facilities.

The processing of natural gas involves removing CO2 from the gas stream. This process produces an almost pure stream of CO2, which can be stored. There are two operating natural gas plants that capture and store CO2 from natural gas processing: the Sleipner plant in the North Sea and the In Salah plant in Algeria. Gas captured from natural gas processing is also used in several enhanced oil recovery projects in the United States.

Steel Production

The iron and steel industry is a major industrial emission sector, accounting for about 650 MtCO2 pr year. Steel production can be broadly separated into two categories. The integrated steel plants are used predominantly to produce steel from iron-ore in a blast furnace, using coal as the primary fuel. Mini-mills uses electric-arc furnaces to melt scrap metal, often adding direct-reduced iron to improve steel quality.

In many blast furnace operations, CO2 removal is already integrated in the process. The blast furnace process involves reacting iron ore with CO to remove carbon from the ore, producing CO2. The top gas in these furnaces is a mixture of CO, CO2 and H2O, where the CO can be recycled to the bottom of the furnace to improve steel production.This requires the CO2 and water to be removed. Water can then be removed from this stream, using condensation, leaving a pure CO2 stream, ready for capture, compression and storage.

In mini-mills, the direct reduction of iron ore is an opportunity for CO2 capture. This involves reacting high oxygen content iron ore with H2 and CO to forme reduced iron and H2O and CO2. 90-95% of the CO2 may be captured from this process. In addition, CO2 can be captured from the production of H2, in a process similar to pre-combustion capture in power plants.

Ammonia production

Ammonia production is one of several petrochemical processes that produces CO2. Ammonia is produced through reformation of hydrocarbons, CO2 being a byproduct. The CO2 must be removed from the reformer as part of the process. This is done using amine technology in most existing plants.

The resulting CO2 stream could be stored directly. However, in many cases ammonia plants are set up so as to use the produced CO2 in other processes, notably the production of urea. Some CO2 captured from ammonia plants is currently used in enhanced oil recovery.

Other processes

Other petrochemical processes, such as the production of ethylene, hydrogen and methanol are also viable for CO2 capture and storage. The petrochemical industry combined accounts for nearly 300 MtCO2 pr year.

CO2 can also be captured from processes involving biomass, such as the fermentation of sugar to produce bio ethanol.

See also