Pumps for wet flue gas desulfurization

A cement factory in Texas was among the first in the USA  to install wet flue gas scrubbers in order to reduce the sulfur dioxide emissions. This is a demanding application for pumps because the gypsum slurry that “scrubs” the gas is highly abrasive and corrosive.

Special pumps with housings and impellers made of mineral cast prove to be a perfect solution here.

Wet Flue Gas Desulfurization Scrubber systems are a vital component in various industries due to strict environmental regulations. First applications were coal fired power plants and waste incineration plants. Today, other industries utilize wet scrubbers in their day to day operations as well to scrub flue gas emissions from burners that utilize coal as a fuel source.

Slurry “scrubs” toxins from flue gas

The scrubbers remove toxins from coal fired flue gas streams in the process. This is accomplished by spraying a mixture of limestone slurry over incoming flue gas. This creates a chemical reaction which removes or “scrubs” the toxins from the flue gas. Once the limestone slurry reacts with the incoming flue gas, it is converted to a gypsum slurry. The gypsum is then dewatered and can be sold to end users for use in various industries. Concrete manufacturers are able to utilize the dewatered gypsum in the concrete production process.

Horizontal single-stage centrifugal pump in back pullout design type MC. All components which are in contact with the liquid are made of SICcast

A unique material for pump housings

The selection of pumps for this application is a crucial task: Due to its significant corrosive and abrasive characteristics, gypsum slurry is a very difficult medium to handle. An American cement plant with a yearly capacity of about 2 mio. metric tons has found a very good solution for that issue when it installed the first of two scrubber systems in 1998.

The housings of the eight Duechting pumps from the MC series in the limestone slurry cycle are not made from metal materials, but from a special material called SICcast® that was designed specifically for extremely harsh conditions.  SICcast is a mixture of Silicon Caride (SIC) and epoxy resin that is then poured into precision molds and heat cured to form the SICcast pump components utilized in our Mineral Cast pump series.  SICcast must be machined with diamond tools due to the patented material exhibiting a hardness close to that of diamonds. SICcast is completely impervious to corrosion and exhibits extreme abrasion resistance given its metallic free composition and high hardness value.

Installed base of over 30 pumps in one plant

The MC scrubber recycle pumps in this plant are operating at a flow rate of 1310 m3/h, 21.1 m of head, and 630 rpm for nearly twenty years now, only requiring minimum attention and service. Of course, the mechanical seals had to be exchanged from time to time. But apart from that, only four impellers, one casing cover and some minor components had to be replaced. A further 24 MC pumps are installed in the second scrubber system and other applications in the plant.

Pumping under extreme conditions

This installation is a true testament to the superior performance of pumps made from SICcast in the harshest environments. It shows why pumps from the MC series are installed not only in this cement factory, but also in wet flue gas desulfurization systems in multiple power plants and other industrial facilities all across the world.

Furthermore, the applications of MC pumps are not restricted to flue gas desulfurization. They are also used in processes like, including but not limited to , ammonia phosphate and TiO2 pigment production, salt solution mining, sugar beet processing and sea water desalination.

Duechting pumps – regardless of whether their housings and impellers are manufactured from steel, stainless steel, coated and surface-treated material or SICcast – are made in Germany and designed for long-life, trouble-free operation under rough conditions. In the USA, the company operates from a sales office in Fort Smith/ AR which also offers comprehensive engineering support. Furthermore, Duechting USA has established two pump maintenance facilities that are operated in co-operation with partners.

www.duechting.com

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