A global effort

Coal-fired power plants produce half of the world’s electric power and are the most challenged with air quality and emissions issues. Due to heightened environmental concerns, many parts of the globe are likely to see an increase in emissions reduction regulations mandating a transition from traditional fossil fuels to renewable energy sources.

While a number of countries within the European Union have had stringent renewable energy source targets for several years, the Obama administration recently acknowledged that carbon dioxide (CO2), nitrogen oxide (NOx) and other industrial emissions endanger the planet. This moves the United States’ position closer to that of the EU nations that have adopted the Kyoto Protocol’s greenhouse gas limits. With this significant shift in US procedure, minimisation of carbon dioxide emissions is truly a global effort.

These emissions are produced by a variety of products and processes, but of particular concern is the amount of emissions produced in the power generation process. In order to reduce emissions and maintain optimal system performance, many power producers are looking for newer, cleaner energy resources.

The pursuit of alternative energy sources has led to the increased utilisation of biomass, which is any living or recently dead biological matter that can be used as fuel. While it does contain carbon, biomass is still a desirable energy source because it is renewable and its CO2 emissions are subsequently absorbed by its replacement crops, resulting in nearly zero net addition of CO2 to the atmosphere.

The partial or complete substitution of fossil fuels with biomass materials for powering industrial or power-generation boilers has a long history of success. However, converting a plant burning coal to biomass presents several challenges. Biomass fuels have different burning characteristics, often contain high levels of moisture and produce residual ash that can be corrosive and laden with a high percentage of unburned carbon. These factors can negatively impact efficiency, capacity and control of other emissions.

However, these challenges have created opportunities for companies experienced in combustion efficiency improvement. Nalco Mobotec, an air protection company operating as a subsidiary of Nalco Company, developed much of its core technology to meet the needs of Scandinavian countries’ early utilisation of biomass in the power generation process. The company’s patented ROTA™ (Rotating Opposed Fire Air) staged combustion system, along with its ROTAMIX™ chemical application systems, have proven effective in tackling the problems associated with biomass burning.

Boiler systems designed to burn coal or oil rely on a hot flame to complete the combustion process and transfer energy to produce steam. Unfortunately, these high temperatures promote the formation of nitrogen oxides (NOx) in the presence of sufficient oxygen. By staging the combustion process, the amount of oxygen is reduced in the burner region of a boiler and is redirected to a cooler location downstream of the burners. While this reduces NOx formation, it also creates the possibility that combustion will not be complete and not enough heat transfer will occur to generate the quantity of steam expected from the boiler. This challenge is even greater when burning biomass fuels due to lower flame temperatures and the difficulty in burning some components of the material. The ROFA system’s unique high∞energy mixing of the second layer of air with the fuel delivers more complete combustion, more efficient heat transfer and reduces NOx generation.

Nalco Mobotec currently has multiple biomass conversions in place or in development around the world, focusing on an immediately available approach of converting coal∞fired plants, rather than building brand new alternative energy facilities. In 2005, a biomass conversion including the installation of ROTA and ROTAMIX was carried out on a 240 MW, tangentially-fired boiler in Helsingborg, Sweden at Västhamnsverket Power Plant.

The conversion from coal to biomass was performed gradually by utilising a co-firing process, wherein biomass fuel and a base fuel such as coal combust concurrently. In 1998, a co-firing project was performed using only 15 percent biomass. After a positive experience, the biomass share was increased to 30 percent in 2000, 70 percent in 2004 and 100 percent as of 2006. Throughout the conversion process, various types of biomass such as wood residue, bark and straw were directly co-fired with coal. Because biomass contains high levels of alkali and chloride components, the ROTAMIX system was installed to reduce the risk of fouling and corrosion. After the plant had been fully converted to biomass, all emissions standards were met and steam production was maintained at the optimal pre-conversion levels.

Nalco Mobotec’s programmes are quickly becoming the standard for power plants and coal-burning industrial facilities seeking to reduce the environmental impact of their operations in a practical, cost-effective manner. In an effort to maintain their industry-leading status in the arena of air emission reduction, Nalco created the Nalco Air Protection Center of Innovation to focus on additional air pollution reduction solutions, including an effort to develop advanced CO2 reduction. This endeavour is a combination of the combustion modelling, design, engineering and emission management capabilities of Nalco Mobotec and its parent company’s experience in chemistry and its application – a powerful set of capabilities that may lead to the continued development of proprietary emission control programmes.

While many technologies under discussion today are too costly, years away from being commercial or not reliable for continuous, sustainable use, Nalco Mobotec has engineered solutions that require minimal modification of existing furnaces and associated systems and can be implemented for a fraction of the cost of installing new equipment. Furthermore, these offerings take advantage of a variety of lower-cost or less-polluting fuels while in many cases increasing production capacity and efficiency.

About Nalco
Nalco Company is a global leader providing essential expertise to over 70,000 customers to meet their water, energy and air quality goals in a sustainable manner—benefiting not only the customer, but the planet, the economy and society. It’s committed to sustaining its solutions with the after-sale service of its over 7,000 engineers and technicians around the globe who visit customer sites each day. This legion of highly trained people is backed by technical service resources that include experts in many technology areas and sophisticated remote monitoring capabilities that serve as a backup to the customer’s efforts to maintain efficiency and quality of their operations.
 
The company has received numerous awards including the US Presidential Green Chemistry Challenge Award for Nalco’s 3D TRASAR technology for cooling water treatment. In 2008, more than 5,000 customer locations in the United States, Canada and Europe used 3D TRASAR technology for their cooling systems, saving an estimated 63 billion gallons of water.

Nalco’s successful commitment to sustainability was recognised in 2008 with its addition to the Dow Jones Sustainability Index. This World index is based on a thorough analysis of corporate economic, environmental and social performance, assessing issues such as corporate governance, risk management, branding, climate change mitigation, supply chain standards and labour practices. That commitment is now extended to air protection with the addition of Nalco Mobotec.

Further information: www.nalco.com