Multistage oil-free compressors from AERZEN are energy efficient customised solutions for the shipbuilding industry tooUsing boil-off gas safely and sensibly
AERZEN offers a wide range of solutions for the multi-stage oil-free compression of gases. For example, AERZEN packages play an important role in the handling and processing of boil-off gas (BOG) in the shipping industry.
Safe, protected and efficient shipping on clean seas”: this is the motto of the International Maritime Organization (IMO), a specialised agency of the United Nations with 175 member states worldwide. One of the aims of the IMO regulations is to reduce emissions from ships. This also applies to climate-damaging gases such as methane, which can be produced when boil-off gas is drained (see case). “We expect that boiloff gases from ships will only be allowed to be released into the atmosphere until the end of 2025,” says Bernd
Klemme, Technical Manager at RKR Gebläse und Verdichter GmbH in Rinteln. RKR Gebläse und Verdichter GmbH is a wholly owned subsidiary of Aerzener Maschinenfabrik GmbH and spe-cialises in multi-stage oil-free systems in relation to the application process. “We combine AERZEN standard products with our engineering, design and assembly expertise
to create AERZEN customised solutions,” explains Bernd Klemme. Based on the double-stage 2C screw compressor series, RKR has developed a 2C G package that fulfils the safety requirements of DIN EN 1012-3 for flammable gases and therefore also for BOG. In order to guarantee maximum process reliability, the sealings of the AERZEN compressor stages used were optimised and a special material was selected. Depending on the environmental conditions, equipment with ATEX components is also possible.
Three main processes
With the new double- and three-stage oil-free compressors for gas applications, AERZEN offers the marine industry an energy-efficient solution for the three most important processes in which BOG is produced and can be reused after treatment:
1.) In the “recovery system” for large container ships, which produce around two tonnes of BOG as exhaust gas every day, which is piped to a plant on land for further
use as heating gas, for example. The compressor is required on the one hand for conveying and on the other for compressing the BOG to a different pressure level.
2.) The “Fuel Gas Supply System”, which is used on ships to transport LNG or other gaseous fuels from the storage tanks to the internal combustion engines or other
consumers. The resulting BOG is fed back to the motor by the compressor after pressure adjustment - not only to reduce emissions, but also to lower energy costs through the resulting turbo effect. In addition, the compressor can be used as a component of the BOG’s reliquefaction system.
3.) In the “Cargo Handling System” on LNG tankers, which is responsible for the secure transport, storage and transshipment of LNG on board the ship. Here, AERZEN
packages are used for compression of the BOG and for recirculation into the LNG storage tanks as well as for pressure control of the cargo tanks. Bernd Klemme is very confident that the AERZEN Group fulfils the requirements of the international shipbuilding industry with the BOG compressors. “We do not deliver off-the-shelf solutions, but bespoke and therefore cost-optimised solutions that secure the sensible and safe handling of boil-off gas for all parties involved, such as shipbuilding companies, ship owners and operators as
well as consulting and classification companies.”
Further Information
About boil-off gas
Boil-off gas is a gaseous by-product that is generated during the storage and transport of liquefied natural gas (LNG). LNG is liquefied at very low temperatures (typically below -162°C) to reduce its volume and make it easier to transport over long distances by ship or truck. When LNG is stored or transported, the product gradually heats up and begins
to vaporise. This vaporisation process generates the boil-off gas. It consists of the original components of LNG, mainly methane (CH4), and possibly small quantities of other light hydrocarbons.
Wide spectrum
AERZEN offers multi-stage oil-free compression of gases not only for the utilisation of BOG, but for a wide range of industries and applications:
• For the extraction and processing of biogas and landfill gas
• In the chemistry and petrochemical industry for processes such as air and gas treatment, nitrogen and hydrogen recovery as well as gas purification and compression
• In the food and beverage industry for processes such as ventilation of fermenters, gas conveying and treatment as well as filling and packing
• In power plants and other energy generation plants for gas extraction, processing and compression as well as for feeding biogas into the grid
