Increasing demand for selective catalytic reduction (SCR) systems for cutting NOx emissions from ships has benefited the German supplier H+H Umwelt und Industrietechnik. The company has manufactured catalytic waste gas treatment systems since 1998 and originally focused on land-based applications.
Since the first marine SCR system was commissioned in 2005 around 600 EcoMarin installations have followed on 160 ships. Success is based on four factors, H+H founders Alexander Hommen and Michael Heck citing:
• some 20 agents and service centres worldwide ensure a swift response wherever a ship is located
• fully assembled and tested turnkey systems are delivered ready for deployment and supported by a maintenance package, including catalyst replacement
• systems are designed and wholly assembled in-house and configured for the specific ship
• fast and reliable suppliers.
Among the key suppliers is Allweiler AG, whose progressing cavity pumps have been core components of the SCR systems since 2003. The pumps feed urea into the exhaust gas line, the resulting ammonia acting as a NOx reducing agent in the treatment process.
Urea is continuously circulated by the pumps in a closed loop, excessive amounts being fed back into the storage tank. A major advantage claimed is their pulsation-free pumping characteristics; even when starting, no pressure surges that could damage the system are produced.
The pumped liquids (32-40 per cent urea and 12-24 per cent ammonia water) are demanding for the pump materials but Allweiler, which manufactures its own stators, can select the best combination from 20 different materials.
Other parts that contact the pumped liquids directly, such as the joint collar, are also made from specially adapted materials to secure an extended service life. Along with casings of stainless steel, the material configurations reportedly enable the pumps to achieve continuous operating times of 8,000 hours or more.
Allweiler’s ANBP and AEB series progressing cavity pumps are used for the H+H SCR installations. Equipped with dry running protection, the pumps have capacities between 600 and 4,000 litres/h at up to 9 bar pressure. Urea is drawn from storage tanks up to 4m away. MP
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