Emissions Control
Emission Control Technologies are a development of technologies to remove SO2 (sulfur dioxide), SO3 (sulfur trioxide), NOx (nitrous oxide), and other particulate matter from coal-fired power plants and other industrial sources. The research focuses on the development, demonstration, and commercialization of technologies to minimize the environmental impact of mercury and other air toxic metal pollutants on the environment worldwide. The task could be implemented by retrofitting the original devices or engines. Retrofitting refers to the installation of non-original parts or devices on a vehicle or device after the engine's manufacture.

Some of the technologies used in emission control technologies are listed below.

Diesel oxidation catalysts are devices that use a chemical process to breakdown pollutants in vehicle exhaust into less harmful components. More specifically, a DOC has a porous ceramic honeycomb-like structure that is coated with a material that catalyzes a chemical reaction to reduce harmful air pollutants. DOCs rarely require maintenance, come with a 100,000 to 150,000 mile warranty, can last for 7 to 15 years, and can be installed on a variety of diesel vehicles. When used with the ultra-low sulfur diesel (ULSD) fuel, DOCs reduce emissions of carbon monoxide by 70 percent, hydrocarbons by 60 percent, and particulate matter by 25 percent. DOCs do not require the use of Ultra-low Sulfur fuel though. Reductions will still be significant when DOCs are used with regular diesel fuel but not as high as with the use of ULSD fuel. In general a DOC cost between $1,000 and $1,600. DOCs take about 1 to 3 hours to install.

Diesel particulate filters are ceramic devices that collect particulate matter in the vehicle exhaust stream. The heat produced by the vehicle exhaust heats the ceramic filter and allows the particles to break down (or oxidize) into less harmful components. Unlike diesel oxidation catalysts (DOC), DPFs must be used in conjunction with ultra-low sulfur diesel (ULSD) fuel. DPFs work best on diesel engines built after 1995. Therefore, knowing the age and type of each engine in the fleet as well as the exhaust temperature is an important part of any retrofit project. Manufactures recommend that DPFs be cleaned about every 100,000 miles. Most DPFs come with a 100,000 to 150,000 mile warranty. A vehicle that uses ULSD fuel and has a DFP installed can reduce emissions of carbon monoxide, hydrocarbons, and particulate matter by approximately 90 to 95 percent. The filters cost from $7,000 to $8,000 per vehicle and work best on engines built after 1995. DPFs typically take about 6-8 hours to install.

Exhaust gas recirculation technology has great potential for reducing emissions of NOx from diesel engines. There are two distinctively different types of EGR available. High-Pressure EGR re-circulates exhaust between the two high pressure points - exhaust manifold and inlet manifold. The Low-Pressure EGR re-circulates exhaust between the two low pressure points - exhaust system tail pipe and turbocharger inlet.

Selective catalytic reduction of NOx means reducing it to nitrogen (N2) and oxygen (O2) over a specially formulated catalyst in the reaction with a reductant. The most commonly used reducing agent is ammonia (NH3) in the form of urea. Although high levels of NOx reductions can be achieved this technology presents several practical challenges - filling and storage of urea, limited distribution network, etc. The technical challenges include complicated urea handling and dosing system, requirement for high temp exhaust for a catalyst to be efficient, control of ammonia slip during transient conditions and large volume of catalyst required.

Certain compounds can adsorb NOx in the exhaust gases. Catalysts containing barium oxide were tested and the results showed that adsorption was most effective at temperatures close to 750 °F (approx. 400 °C). The catalysts have a limited storage capacity and needs to be regenerated in order to regain activity. The regeneration is done under stoichiometric conditions and the adsorbed NOx dissociates to nitrogen. This type of catalyst is interesting for the development of petrol lean-burn engines which run with excess air except at high loads when the engine runs stoichiometric. To obtain regeneration conditions in diesel exhaust gases is a great technical challenge which is enabled by the use of electronic fuel injection and injection of fuel to the exhaust gases. Also, the catalysts tested are sulphur sensitive.