Shipping is struggling with choppy waters: under the International Maritime Organization (IMO) standards which have recently come into effect, the proportion of sulphur in the fuel used by ships must not exceed 0.5 percent from 2020 worldwide. Shipping companies face the challenge of efficiently combining environmental protection and economic viability. The maritime flue gas cleaning system fitted to the ocean-going tanker Aurelia is showing the way forward. Owned by Bremen-based shipping company Carl Büttner Reederei, the ship is currently being fitted with a new flue gas desulphurisation system sourced from Babcock Noell, a Bilfinger SE company. This proven industrial technology ensures that the sulphurous flue gas generated on board the ship fully meets environment protection requirements. To this end, the gas is purified in a scrubber process entailing the addition of scrubbing water. The investment will pay for itself in fewer than three years. The Aurelia will be returning to service in mid-November 2016 after a brief conversion period.
Depending on requirements, the scrubber cleans emissions from one or several sources. The sulphurous flue gases are filtered using an absorption process.
Photo by Bilfinger SE
Shipping makes a significant contribution to global air pollution. Yet, this is now to change. Under the Marpol Annex VI regulation, the proportion of sulphur in fuel in the emission control areas (ECA), the waters of the North and Baltic Seas as well as off the coast of North America, must not exceed 0.1 percent from January 2015. These restrictions are now to be extended beyond the current zones to cover all oceans from 2020. Consequently, ships not just in the ECA waters but across the entire world will only be permitted to operate with desulphurised fuel. However, a more cost-efficient response is to install a flue gas desulphurisation system. Thanks to the efficient scrubbing process, it is possible to continue using proven fuel types.
Industrial technology generating added value for shipping
Babcock Noell's desulphurisation technology has been in use in industry for 40 years. To make it viable for shipping, the process has been modified to take account of maritime conditions and the flue gas to be cleaned. Two installations are available to ensure that the system meets the user's requirements: The scrubber can be installed in a single-line arrangement in the stack to clean the source of the emissions, normally the main engine, to save space. The multi-stream version cleans several sources of emissions on board the ship, e.g. the main and ancillary engines as well as the boiler, at the same time. This means that only a single set of components as well as the expensive emission-measuring technology is required, thus permitting considerable cost savings. As a rule, it is installed as a by-pass system at the aft of the ship. In this way, it is possible to make optimum use of the available space.
In line with the Marpol requirements, Babcock Noell's scrubber system also supports two different operation modes: the open-loop process scrubs the sulphurous waste gases by making use of the natural alkalinity of the sea water, which is added to the system. The pH-stable process water is then discharged into the sea in accordance with the IMO requirements. Alternatively, the scrubber can be operated in a closed loop. In this case, a liquid additive is injected into the water to achieve the proper scrubbing effect. The spent water is stored in a tank and processed in a water purification system, making this process suitable for areas that are subject to particular protection requirements. “In both cases, users benefit from low operating costs and high system availability. In addition, the innovative process water cleaning system meets the highest environmental protection standards,” explains Andreas Breeger, head of maritime flue gas cleaning systems, Environmental Technologies at Babcock Noell, adding that “Babcock Noell's business model is based on a turn-key approach. We reduce the number of cost-intensive interfaces for our customers as we do not only supply the components but also handle the full installation.”
The multi-stream scrubber is being installed on board the Aurelia. The cold start-up will be executed in the dry dock.
Photo by Bilfinger SE
Installation and start-up completed in a few weeks.
In the case of the Aurelia project, the multi-stream scrubber is being installed in the hybrid version, thus enabling both open and closed-loop operations. The captain can select the process depending on the waters the ship is traveling through. “We have found in Babcock Noel a competent partner for flue gas cleaning. What particularly impressed us was the proven and innovative process technology,” reports Lars Bremer, managing director of Carl Büttner Shipmanagement GmbH. The project is also being completed in a particularly short time. Thanks to the large proportion of preassembled parts, all components were installed at the shipyard within a very short space time. “A further reason for our decision is the swift amortisation. This reference project is a future-proof investment for us setting new standards in the shipping industry,” Bremer adds.
Source: Bilfinger