Air pollution control systems from ANDRITZ span a wide range of emissions control technologies for power stations, biomass plants, energy-from-waste facilities and other industrial applications. The company's product portfolio includes wet and dry flue gas cleaning plants, deNOx/SCR systems, and combined flue gas cleaning technologies.
ANDRITZ received its first order to supply a flue gas desulphurisation (FGD) plant in 1983. This was the first FGD system for a lignite-fired boiler in Europe. Since then, the company has supplied more than 100 FGD plants, primarily for coal-fired power stations, and ranks among the leading companies in this sector in Europe and China.
When fossil fuels are burned, pollutants such as sulphur oxides (SOx), nitrogen oxides (NOx), dust, heavy metals, chlorides and fluorides are created. SOx and NOx are largely responsible for causing acid rain. The majority of FGD plants use a wet limestone process. This is preferred by large power stations because it is the most efficient method over long periods of time, providing the highest removal rates at the lowest operating costs. The process uses relatively inexpensive limestone, which is commercially available almost everywhere in sufficient quantities.
In a wet FGD system, the boiler's flue gas is washed in a spray absorber using a limestone suspension. In this way, up to 99% of pollutants can be removed before the gas is vented. The acid components in the flue gas react with the alkaline limestone and, when oxygen is added, high-grade gypsum is produced. This gypsum can be used in the cement or construction industries.
The main features and benefits of Wet FGD are:
ANDRITZ's products include a dry FGD process - a Turbo-CDS/Turbosorp system based on circulating fluidised bed technology. The Turbo CDS is used in coal-fired power stations and the Turbosorp process is used in industrial applications. It uses chemical-physical material and heat transfers in a circulating fluidised bed to remove pollutants. In the circulating fluidised bed, inside the turbo-reactor, there is constant mixing of the flue gas and the absorbent (lime hydrate), which binds the acid pollutants in the flue gas.
Any excess absorbent leaves the turbo-reactor with the flue gas, fly ash and other reaction products, and is separated in a bag filter or electrostatic filter. Most of the separated solids are returned to the reactor and reused. By adding a small amount of activated carbon or lignite in the turbo-reactor, potential pollutants such as heavy metals, mercury, dioxins and furans can also be removed.
The central advantages of Turbo-CDS/Turbosorp are:
The ANDRITZ portfolio also includes deNOx plants to prevent nitrogen oxide emissions. These can be customised for special applications and are often configured in a multistage design. The major advantages of deNOx are:
Multistage/combined flue gas cleaning system features are:
