Installation of an Exhaust Gas Scrubber - Research Paper Example

Installation of an Exhaust Gas Scrubber Introduction Emissions from the marine fuel used by vessel generally contain a Sulphur concentration of less than 10 ppm (parts per million). Marine bunkers, on the other hand, were earlier allowed to consist of up to 50,000 ppm in terms of Sulphur concentrations as per most legal frameworks around the world. However, drastic changes have been made during the recent period in connection with the permissible amounts of Sulphur content among marine fuels, especially within the European Union (EU) (John Wilson, 2008). The process of combustion of marine fuels generates gases such as Sulphur oxides and Nitrogen oxides. In addition, the frequent incomplete combustion also produces a large amount of particulate matter. These emissions, which are emitted in thousands of tons per day, damage the environment and the ecosystems in many ways including the acidification of the atmosphere and landmasses. In May 2005, the MARPOL Annex VI came into effect. The primary objectives of the annex are to contain emissions of the Sulphur and Nitrogen oxides from vessels, which have been identified as the primary contributors of ‘acid rain’, especially near the shore. When vessels are on high seas, the increased acid concentrations are constantly neutralized by the natural chemicals found in the ocean. The European Parliament adopted the directive 1999/32/EC in early 2005, which mandates the introduction of abatement methods on the vessels. Evidently, the introduction of these new regulations has had an impact on vessel owners, charterers and bunker traders (John Wilson, 2008). Information Gathering MARPOL Annex VI The Annex VI specifies that the Sulphur level on a global scale should be maintain below 4.5% (Martin Stopford, 2009). Although this does not help change much on the ground as most fuel oils have a Sulphur content at or below 3%, the Annex VI also specifies an upper limit of 1.5% for all marine fuels in areas designated as control areas for Sulphurous gases’ emissions (SECAs). This upper limit stands in all situations unless the vessel is fitted with an exhaust gas scrubber or any alternate technology that can ensure that Sulphur oxides are not emitted beyond permitted quantities under any circumstances. Additionally, while Annex VI also provides for a cap on substances that deplete the ozone layer, there is no inclusion of greenhouse gases. The MARPOL Annex VI has to be followed by all ships which have the flag of a member country that has ratified the framework and also extends to those ships which operate within the territorial waters of all such nations. While there are certain exceptions to these guidelines, almost 25 of the world’s biggest nations accounting for over two-thirds of the world’s gross tonnage have approved the implementation of the Annex VI. Besides the MARPOL regulations, the European Union has also specified new regulations that impose restrictions on the emissions from vessels. In fact, at one stage, the EU was considering the prospect of imposing lower limits in comparison to those laid out by the MARPOL Annex VI. However, the IMO reached a compromise solution with the European Parliament which ensured a uniform implementation of the EU Sulphur directive as stated under 1999/32/EC. The new regulations which came into effect in mid 2006 have imposed lower limits for Sulphur emissions on both passenger ships and ferries providing regular services to any port within the EU, thereby mirroring the guidelines laid out for SECAs as stated in the MARPOL Annex VI. Further, this low limit for Sulphur emissions will be brought down even further from 2010 (Donald Rothwell, 2006). Sulphurous Gas Emissions (SECAs) SECAs are designated areas situated along coastlines that have been identified as being particularly sensitive to deposits from acid rain. With the Annex VI coming into place, the Baltic Sea became the first area to be identified as a SECA. The English Channel and the North Sea, other areas involving high volumes of sea traffic, have also been identified as SECAs in 2007. A vessel within a SECA is not supposed to contain Sulphur content beyond 1.5% m/m. This applies to both residual fuels as well as distillate grades (Martin Stopford, 2009). Cost and Availability With the identification of new SECAs each year, more and more ships have to adhere to the MARPOL Annex VI guidelines, implying a constant increase in demand for heavy fuel oil with low Sulphur content (LSHFO). For instance, the nearest suppliers of any LSHFO grade fuels for vessels based in the EU are in Singapore. Further, the quantities available for worldwide supply are limited and there is a need for elaborate planning to obtain the required quantities of bunker fuel in advance. The use of LSHFO also comes with a cost premium at over $50 per ton and is expected to rise to $70 in the coming 2 years. Prolonged use of these fuels can also lead to accelerated wear and tear of the engine due to accumulation of residues. Overcoming this requires the use of additional lubricating oils, requiring more maintenance and hence higher costs (Martin Stopford, 2009). The time consuming task of booking fuel in advance and the overhead costs simply make using LSHFO an uneconomical option in the current case. Dual tank systems Many vessel owners are contemplating the use of two tank systems wherein one would be used to store the standard 4.5% Sulphur fuel and the other would be used to store the LSHFO. On entering a SECA, the procedure would involve shifting from high Sulphur to a low Sulphur based fuel supply. However, switching between using fuels entails considerable times in flushing prior contents that exceed the 1.5% limits. Further, there is a need to keep detailed records of when and where these changes were made during the entire schedule of the vessel (Markus Kachel, 2008). Alternatives Besides the approaches suggested above, it is possible to comply the SECA regulations without relying on the use of LSHFOs. One among them is the use of exhaust gas scrubbers, which can be installed on the vessel. Exhaust gas cleaning (EGC) is a technology whereby the systems provide for the cleaning of both Sulphur and Nitrogen based emissions. Installing an EGC system requires the identification and allocation of adequate space on the vessel apart from the installation of required equipment. While this requires initial investments, the use of such systems is a long term solution which will provide cost benefits in the coming years (Markus Kachel, 2008). The average cost of installing an EGC system on a ship is around $500,000. Setting up and approval The proposed exhaust gas scrubber (EGS) can be implemented in several ways such as a fresh water scrubber or a sea water scrubber system. Amongst the solutions available, it has been chosen to go for the technology based on seawater based scrubbing as this method involved lesser operating costs and facilitated the use of less expensive fuel. This avoids the need for tackling switching, availability and storage related issues thereby helping in reducing the impact on the environment. It has been proposed to design the scrubber to run cold although the system can operate in extreme hot temperatures of up to 450 degrees centigrade. The design of the unit helps remove up to 99% of Sulphur based oxides and more than 80% of the particulate content when the fuel being used is a 4% SHFO 380 grade fuel. This will imply proper compliance with both MARPOL Annex VI and the European Union’s in-port guidelines that stipulate a 0.1% content of Sulphur in the exhaust gases. Further, the system will be designed to contain the noise generated by the exhaust. Its natural fitting into the funnel space is possible through a lightweight system with self-supporting capabilities. In addition to this stable design it is also important to obtain several approval certificated that are mandatory in order to prove due compliance with various shipping guidelines. For all ships over 400 Gross Tonnage, it is necessary for them to obtain an international air pollution prevention certificate. This IAPP certificate was obtained from Denmark (pls change as required), which is one of the countries that ratified the MARPOL Annex VI. The IAPP certificate is valid for a period of 5 years and will end in March 2011. All preliminary surveys necessary for this purpose have been completed during the course of the processing of the application. The supplementary Record of Construction and Equipment that comes along with the IAPP certificate did not find many major defects with the existing condition of the vessel (excluding the main exhaust scrubber) and obtaining the certificate to continue operations meant that a scrubber system had to be installed. Further, it was also necessary to secure the Engine International Air Pollution Prevention Certificate (EIAPP), which essentially extends the MARPOL regulations to each engine on the vessel. Obtaining this certificate involved an elaborate process that involved contacting the manufacturer so as to obtain confirmation of compliance with the Nitrous oxides’ (NOx) technical code. The engine manufacturer provided this information for the specific engine type as well as its associated technical file (pls replace this with an engine type of ur choice). Specification The sea water based exhaust scrubber is based on an open system. This system utilized the fact that a portion of the sea water that is used for cooling the engines is then put into use for the scrubbing operation. The concept takes note from the reaction between Sulphur oxides and the calcium present in the sea water (in the form of Calcium carbonate, CaCO3). The resulting reaction produces gypsum (Calcium Sulphate) besides emitting Carbon Dioxide (CO2). Besides consuming a part of the buffering capability of the sea water, the exhaust scrubber helps neutralize the acidity present in Sulphur Oxides. The vessel will require the proposed Seawater Scrubber to have a capacity of 4 MW and require concurrent operation across two individual components namely the main and auxiliary engines and the steam boiler. Subsequent ductwork is also necessary to be installed in order to route the emissions from the auxiliary engines and the boilers into the scrubber. The approximate cost of a system can cost anywhere between $800,000 to $1 million including all labor and material costs necessary for the transport and installation of the equipment at a designated port. The vessel has two B&W engines model no. 872738 manufactured by Man Diesel SE. Each engine has a production capacity of 2500 kW and operates on diesel at 85% MCO. The vessel also uses a 750 HP boiler for steam propulsion. It is necessary to ensure that the scrubber meets the requirement of limiting SOx emissions to under 6 g for every kWh of power generated. Popular scrubber systems manufactured by reputed firms such as the Aalborg industries are capable of minimizing SOx emissions to under 0.1 g per kWh or less than 10 ppm. The concentration of the particulate matter from the emissions is also reduced to levels below 0.12 g per kWh. The scrubber system needs to include facilities for continuous monitoring of several parameters including the date and time of taking readings, instantaneous engine power, the SOx concentration into and out of the scrubber as well as the related particular concentrations before and after the emissions. All these readings along with the concentrations of NOx and CO2 are also recorded and stored in a database log for further analysis. Besides keeping a constant overview over these parameters, it is also necessary to monitor the salinity levels of the incoming seawater. The inflows should be examined for turbidity, oil concentration, pH, hydrocarbons and the quantity of dissolved oxygen. Besides the flow of liquids, a certain quantity of solid matter is also collected and needs to be automatically tested for pH, hydrocarbon content and metallic character. This is necessary to ascertain a proper method of disposing the solid waste once the vessel reaches ashore. Collecting this solid waste requires the installation of an intermediate bulk container, which can either be custom made or converted from an existing cargo tank on board. This task must have proper outlet facilities to allow multiple offloads during a year. The viability of the sea water based exhaust scrubber is strengthened by the fact that the SOx decomposition reaction takes place in a very short amount of time. The slightly alkaline sea water, which contains more basic than acidic properties, can be utilized in areas where sea water finds additional use such as in cooling engines. This makes it a perfect solution to implement as an auxiliary tool for scrubbing exhaust gases. A certain volume of water is necessary to complete the scrubbing operation (consume SOx), which essentially involves the scrubbing water to obtain a pH (a measure of acidity) of 6.5. In the current case, the sea water will be further diluted up to 0.2 units of pH with respect to ambient water. It must also be mentioned that the scrubber consumes water in volumes that is inversely proportional to the salinity and directly related to the water temperature. This makes it a good and effective solution especially when the vessel is operating in warmer seas such as in the Mediterranean and the Persian Gulf. The acidic nature of the scrubbing action and its corrosive action on the surrounding steel have also been given due consideration. To avoid any undesirable environmental effects, the used sea water (after the scrubbing operation) is mixed with additional quantities of sea water, which is directed from the engine cooling systems. Design As seen in the above diagram, the hot exhaust gases from the dust collectors are transported to the scrubber through a quencher. The Scrubber is fed constantly with seawater from the engine cooling system. The exhaust gas scrubber is essentially a tightly packed tower where the sea water comes into contact with the exhaust gas, thereby performing the countercurrent reaction. As described in the preceding section, the sea water is highly efficient in absorbing large quantities of the SO2 from the host exhaust gases. A number of resources in terms of men and material will be required for the construction and installation of the scrubber. The core element of the system is the scrubbing unit with the possibility of having a separate one for each engine. However, the primary goal of the project was to install the system with minimal cost overruns. As such, it has been decided to install a centralized scrubbing system for all engines on the vessel which will have gas separation paths for all engines. The Scrubbing unit will be purchased as a prebuilt component from the Hayworth industries based in the UK. The reasons for choosing a readymade scrubbing unit are manifold. Firstly, utilizing such a unit reduces the time to construct such a system from scratch. The installation of the scrubbing unit into an existing vessel like the current one will require about 30 personnel to transfer the unit from an onshore mobile platform, place it inside the vessel, connect the unit to the engine exhausts through standard duct pipes and provide inlets and outlets for the seawater. This entire process is estimated to take around 20 days. A quote of $500,000 has been received for the same excluding the labor and material costs for installation on the vessel. After the installation of the scrubber unit, the next step is to install a water treatment system. This unit will be integrated with the scrubber and is capable of treating all the wash water from both the main and auxiliary engines. This wash water treatment plant will be procured from OilTrap Environmental, and works on the principle of electro-coagulation to trap all oil and particulate matter. The oily sludge collected by this system will be stored in a discarded cargo tank aboard the vessel. For this purpose, the storage tank needs to be customized for avoiding any leaks and subsequent plumbing works have to be undertaken to provide effective connection and control between these two units. Estimated unit costs for this system are $50,000 and will require a team of 4 engineers over a week to install and test this system. To facilitate continuous monitoring of the exhaust gases and comply with MARPOL and other guidelines, an elaborate control and monitoring system based on the efficient cascade laser technology will be constructed. A team of engineers from Cascade Technologies, specializing in laser and infrared applications, will begin working on constructing a custom monitoring system once the core scrubber unit is in place. Besides minimizing costs, this approach will enable continuous testing of all new systems and allow steady inclusion of all segments into the monitoring framework. This segment is regarded as a long term investment and is expected to require over $100,000 for all related components. Besides the monitoring equipment, a team of IT professionals from the provider will install an in-house database system that will continuously record the various readings. Business intelligence software has also been included as part of the package that will generate reports for both the vessel operator and any regulator involved. The IT component is being derived from off-the-shelf components and will require minimal testing along few parameters as various supporting components are installed into the scrubber system. Care is also being taken to prevent tampering of any information and ensure data integrity. To comply with port state inspections, the software will store records of up to the last 10 years and will not be accessible for modification once the data has been stored. The system will also maintain a secure backup of all data at a system at the owner’s end in an automated fashion through the use of the vessel’s onboard communication systems. The estimated cost of the monitoring database is $40,000 apart from $5000 per annum for support and maintenance by the software vendor. Care is being taken to provide variable speed controls for all pumps and proper protection is being provided to both sensors and the controls of the scrubber. All pipe work will be done using glass reinforced epoxy material as it complies with the environmental regulations of MARPOL. Execution The work on the installation of the Scrubber began formally on June 3rd, 2009 after the vessel was taken out of service at the dry dock in Blomm & Voss Shipyard in Hamburg, Germany. The first 25 days were spent on preparing the space in the vessel’s funnel for accommodating the incoming gas scrubber unit apart from creating the required inlets and outlets at the required places along the exhaust lines for the connecting pipes. Meanwhile, the main scrubber unit was being pre-fabricated at a location in the United Kingdom so that it could be shipped to the dry dock to be installed inside the vessel’s funnel. The scrubber unit arrived on 15th July, 2009 and was installed into the funnel by 10th August 2009. This period also comprised the loading of additional machinery required for the operation of the scrubber system such as a high-powered water pump and a device that separated all particulates from the sea water (known as a multicyclone). Besides, all other equipment for monitoring purposes and the material for constructing the pipes was also loaded on to the vessel. Since then, a team of 15 workers have been busy cutting holes across various sections of the vessel so as to create inlets through which sea water would be pumped in through the scrubber unit. The inlets were soon connected to pipes that connected the engines to various parts of the scrubber. The various inlets and outlets that connect both these elements are as shown below. Work on building the connecting paths for the scrubber required longer than the allocated schedule and expanded to over 45 days. The delays in this phase were primarily due to additional work that had to be undertaken to devise paths without disrupting the existing pipelines that were essential for the working of existing systems including the engines and the boiler. Although these delays were anticipated, ensuring that they operated smoothly and as per requirements required extensive checks thereby pushing the deadline by 15 days. The completion of the installation of all primary components of the seawater scrubber was followed by the construction of the monitoring system through a 3-stage process. The first step involved surveying the engines, the scrubber system, connecting paths and other parts of the vessel to determine all areas where sensors and effectors had to be fixed in order to achieve effective feedback and control. This was followed by the next stage where all required electronic components (based on the cascade laser technology) were installed at the identified spots in the required configuration and connected to a central control center. The last stage was based on extensive tests of the system including demonstrations for controlling the scrubber, the wash water treatment plant, and the pipe flows through the control system and verifying all the readings that had been collected. The installation and verification process, along with the inclusion of the business intelligence component required over 2 months of extensive work and rework. This phase also provided an opportunity for personnel from Hayworth (provider of the scrubber) to work in cooperation with cascade technologies to fine tune the entire system across all parameters and facilitated the elimination of all performance defects in the system. References 1. John Wilson (2008), Carriage of goods by sea. New York: Pearson Education. 2. Donald Rothwell (2006), Navigational rights and freedoms, and the new law of the sea. University of Virginia. 3. Martin Stopford (2009), Maritime economics. London: Taylor & Francis. 4. Markus Kachel (2008), Particularly sensitive sea areas: the IMOs role in protecting vulnerable marine areas. London: Springer. Read More