**2.1.3 Oxy-combustion**

In theory the oxy-combustion process involves burning a fuel using O2 instead of air as the oxidant. In this process, the N2 is separated in advance, eliminating the presence of nitrous oxide (N2O) in the exhaust gas. Since the sulfur removal units are already obligatorily included in industrial processes that burn fossil fuels, except for particulates and other impurities the exhaust gas contains a high concentration of CO2. However, all oxycombustion systems in practice work with a mixture of O2 with recirculated exhaust gas. Therefore, the oxy-combustion only increases the CO2 concentration in the exhaust gas,

Carbon Capture and Storage – Technologies and Risk Management 247

As indicated above, there are four ways of transporting CO2 between the emission source

Of these four transport means, only pipelines are viable for EOR projects, where the distances can run into the hundreds of kilometers and the volumes of CO2 are in the millions of tonnes per year. This high carrying capacity compensates for the high costs of

Because of the high initial investments and operating expenses of a carbon pipeline and the large damages that could be caused by a rupture, as well as the fact it may cross land held by many owners, special attention must be given to the commercial, legal and insurance aspects to minimize the economic risks. Suppliers and consumers of the CO2 carried by pipeline along with the line operator must participate in detailed multilateral agreements with well-defined rights and obligations. The other types of transport are feasible for industrial processes that use CO2 as an input, in cases where the quantity is small and does not compensate the cost of building and operating a pipeline and/or when the production

In this step, the CO2 is injected through injection wells, basically into three types of

The option for injection in oilfields where production is waning serves another function besides carbon sequestration: it maximizes oil recovery. This process is called enhanced oil recovery (EOR). The standard production process always involves injection of water to maintain the producing pressure. The EOR process, shown in Figure 10, involves injection of water and CO2 in alternation. The CO2 injection increases the oil's fluidity, releasing the oil stuck in the rock pores, while the water, which is by nature not compressible, pushes the oil

An example of the injection of CO2 in EOR projects is the Weyburn project, located on the border between Canada and the United States. It has been in operation since 2000. The CO2, with 95% purity, captured in a coal gasification plant in Beaulah, North Dakota, is carried by a pipeline to an oil production field in Weyburn, Saskatchewan, where it is injected (Zouh et al., 2004). Figure 11 shows the pipeline in yellow that connects Beulah and Weyburn. The red dots show possible derivations for use of the CO2 in new EOR projects in the region.

Pipelines, which in the case of CO2 are called carbon pipelines.

building, maintaining and operating a carbon pipeline.

**2.4 Transport** 

Tank trucks;

**2.5 Injection** 

Coal beds.

geological formations:

Saline aquifers; and

toward the producing well.

Tanker ships; and

and the underground injection site:

Trains made up of tank cars;

and consumption sites are very close.

Exhausted or declining oil reservoirs;

**2.5.1 Injection in exhausted or declining oil reservoirs** 

making its separation more feasible. As a result, the oxy-combustion process must be associated with at least one of the other separation processes. The Figure 9 shows a diagram of oxy-combustion system in a pulverized coal power plant.

The Carbon Capture and Low Emission Coal Research program mandated by the American Recovery and Reinvestment Act (ARRA), signed into law by President Obama in February 2009, calls for investment of US\$ 3.4 billion for research aimed to make burning or gasification of coal an activity with low GHG emissions. One of the simplest ways to modernize a coal power plant is to introduce O2 separation units to feed the burners of the boilers.

Source: Alstom Power (2011)

Fig. 9. Oxy-combustion system in a pulverized coal power plant
