Biodiesel is an important energy source. Its use is promoted through national and international legislation as part of the overall global strategy to reduce carbon emissions. Produced from sustainable renewable sources, such as soybean oil, palm oil and waste vegetable oil, biodiesel can be used in diesel engines, in vehicles and non-road mobile machinery. However, to maximise efficiency and effectiveness the correct blend is necessary.
At the Plymouth Oil Terminal biodiesel is blended with diesel to create a fuel that satisfies both the requirements set down by legislation, for the minimum level of biodiesel in the mixture, and that of engine manufacturers, which insist on sufficient levels of diesel to guarantee their warranties. The equipment needed for such a precise application has to be, not only accurate,but also certified and capable of operating in hazardous areas due to the volatile nature of the products. Biofuels, which include biodiesel, are part of a growing global bio-industry, which if managed correctly will not compromise food security, but instead offer a useful tool to reduce reliance on fossil fuels, decelerate climate change, increase fuel security and broaden the range of bioproducts on offer. Biodiesels can be produced from a number of oils; the most commonly used is soybean oil. The world’s largest producer of soybeans is the United States, producing 32% of world production,followed by Brazil at 28%. The most common method of biodiesel production is a reaction of vegetable oils or animal fats with methanol or ethanol in the presence of sodium hydroxide,which acts as a catalyst. The transesterification reaction yields methyl or ethyl esters, thebiodiesel itself, with a by-product of glycerine. It can also be produced using a number of other plant materials including jatropha, mustard, sunflower and hemp, as well as animal fats and byproducts of the production of omega-3 fatty acids from fish oil. Biodiesel can be used alone, or blended with petro-diesel, namely diesel produced from petroleum, in any proportions. Blends of biodiesel can range from 1% to 99% and much of the world uses a system known as the “B” factor to quantify the amount of biodiesel in any fuel blend. For example, fuel containing 20% biodiesel is labelled B20. Pure biodiesel is referred toas B100, which has the environmental benefit of reducing ozone formation by 50%. Common blends used are B2, B5, B10 and B20. Biodiesel has the highest fossil energy balance of any transportation fuel; for every unit of fossil energy used to make biodiesel, 3.2 units of energy are produced. This takes into account the planting, harvesting, fuel production and fuel transportation to the customer when using plant material. Overall the European Union is the largest producer of biodiesel accounting for 53% of all production in 2010, which places it in a strong position to help meet international targets set by the International Energy Agency, which has a goal for biofuels, including biodiesel, to meetmore than a quarter of all global transport costs by 2050. In a move towards that goal the UK Government has introduced the Renewable Transport Fuel Obligation (RTFO), which is a requirement on transport fuel suppliers to ensure that 4.75% of all road vehicle fuel is supplied from sustainable renewable sources. A company that owns and supplies 450,000 litres or more of any transport or non-road mobile machinery (NRMM) fuel annually is required to register under the RTFO. Any company that supplies fewer than 450,000 litres a year, which includes all fossil fuels and biofuels, is not required by law to register but may wish to anyway to claim Renewable Transport Fuel Certificates (RTFCs). These can betraded or sold to companies that need them to meet their obligations under the RTFO. There are a number of reasons why the UK is aiming to increase biodiesel consumption. The most notable is the reduction in carbon emissions but it will also help to improve the UK’senergy security by making it less reliant on fossil fuels, and therefore the fossil fuel producing countries, many of which are situated in the world’s most volatile and politically unstable regions. The move will deliver environmental as well as political benefits. Blends of 20% biodiesel and lower can be used in diesel equipment with no, or only minor modifications, although certain manufacturers do not extend warranty coverage if equipment is damaged by these blends. To overcome quality issues to preserve manufacturers’ warranties agreements have been reached as to the minimum blend required. The minimum test requirements for biodiesel blends are specified in ASTM D6751 in the US and EN 14214 within Europe, which is valid for all members of the EU. Volkswagen has stated that several of its vehicles are compatible with EN 14214 standard fuel. In fact the move towards biodiesel has been made by many prominent organisations, companies and individuals. For example, Halifax, in Nova Scotia, has been running its fleet of city buses on fish-oil based biodiesel since 2004; McDonalds uses biodiesel produced from the waste oil by-product from its restaurants to run its fleet in the UK; Virgin Trains ran its first biodiesel train in 2007; and Prince Charles uses B100, 100% biodiesel, to fuel his Royal Train. To gain the correct blend to satisfy all parties it is necessary to use instrumentation with a capacity to calculate the blend accurately that is also certified to work within hazardous areas. The Plymouth Oil Terminal comprises of two main tank farm facilities called Mayflower and Cattedown Wharf, with a storage capacity of 42 million litres of fuel. At the site bioethanol, biodiesel, petrol, diesel, kerosene and gas oil are stored, which places it in the top tier category under the Control of Major Accident and Hazard (COMAH) Regulations. Established in 1999 the COMAH Regulations were updated in 2005 and they are in the process of being updated again this year. Top tier operators must prepare a safety report that satisfies the Competent Authority, which in England and Wales is the Health and Safety Executive (HSE) and the Environment Agency. The report must include a policy on how to prevent and mitigate major accidents and demonstrate the management system for implementing it. By requiring measures for both prevention and mitigation there is a recognition that all risks cannot be completely eliminated, as demonstrated at Buncefield in 2005 when two people were seriously injured following the overflow of large quantities of petrol, which resulted in the formation of a large vapour cloud that ignited causing a massive explosion and a fire that lasted for five days. However, where risks are high so are the standards to ensure risks are kept acceptably low to limit their consequences to people working at the site and working and living in its vicinity, as well as risks to the environment. As part of the safety report information must also be included on the safety precautions built into the plant and equipment. Instrumentation also has to comply with the Dangerous Substances and Explosive Atmospheres Regulations 2002 (DSEAR), and ATEX, which is the name commonly given to the two European Directives for controlling explosive atmospheres: Directive 99/92/EC, also known as ATEX 137 or the ATEX Workplace Directive, on minimum requirements for improving the health and safety protection of workers potentially at risk from explosive atmospheres; and Directive 94/9/E, also known as ATEX 95 or the ATEX Equipment Directive, on the approximation of the laws of member states concerning equipment and protective systems intended for use in potentially explosive atmospheres. The aim of Directive 94/9/EC is to allow the free trade of ATEX equipment and protective systems within the EU by removing the need for separate testing and documentation for each member state. In the UK the requirements of the directive were put into effect through BIS Equipment and Protective Systems Intended for Use in Potentially Explosive Atmospheres Regulations 1996 (SI 1996/192). The regulations apply to all equipment intended for use in explosive atmospheres, whether electrical or mechanical, and also to protective systems. On April 20th 2016 the new ATEX Directive 2014/34/EU will come into force and will immediately replace the current 94/9/EC without a transition period.
The Plymouth Oil Terminal was purchased by Greenergy in 2008. It was the first facility of its kind in the UK to meet the new regulations introduced by the Health and Safety Executive following the Buncefield Incident in 2005. Since then there has been an upgrade of the facility, which began in 2008. As with all fuel storage sites safety is of paramount importance but even more so at the Plymouth site as it is situated within the city and close to people’s homes. Greenergy is one of the UK’s largest fuel suppliers, supplying approximately one sixth of all road fuel in the UK, annually in the region of 15 billion litres, with customers ranging from oil companies to supermarkets and petrol stations to fleet users. It supplies fuel from 25 terminals throughout the UK and owns or manages stock at eight terminals across the country including the facility at Plymouth, and also at Cardiff, Thames, Teesside and Clydebank.
The blending process is a ship to shore operation. It starts with the mooring of a ship to an offloading jetty, which then connects to the jetty diesel pumping system. The system in operation at the Plymouth Oil Terminal consists of an 8” Flowquip stainless steel turbine flow meter, a 4” Brodie carbon steel bi-rotor positive displacement flow meter, a Contrec 515-CB02 secure blending flow controller and a 4” Daniels digital control valve. These instruments have been selected to ensure accurate measurement, allowing for highly accurate measurement of flow, and safety legislation compliance, meeting ATEX approvals for use in hazardous areas. Once the ship is connected to the jetty diesel pumping station the system operator slowly starts the jetty pumps to prime the pipe up to the point of an 8” diesel line isolation valve (on/off valve). Once the pipe is primed the system operator accesses the Contrec blend controller configuration menu by secure touch key. The operator then enters the desired ratio of biodieselto diesel and opens the main control valve to the on-shore storage vessel and starts the jetty pumps again. The 8” turbine flow meter detects diesel flow, which is the main flow, and sends a pulsed frequency signal to the blend controller. On detection of the diesel flow signal the blend controller automatically switches on the biodiesel pump via its pump demand output. Biodiesel, the process flow, is pumped via a separate line from an on-shore storage tank. The biodiesel pipeline connects into the main diesel pipeline. As biodiesel is pumped the bi-rotor flow meter sends a pulse frequency signal to the blend controller. During flow conditions the blend controller governs the digital control valve (DCV) in order to maintain the desired user selected blend ratio. The operator can increase or decrease the main flow rate at any time during the process and the blend controller will adjust the DCV proportionally. The 8” turbine flow meter is part of the Flowquip range of flanged FT4 industrial turbine flowmeters designed to provide a highly accurate and economical means of measuring flows of clean liquids over the range 1 to 30,000 l/min with bore sizes available from 15mm to 250mm. The all-stainless steel construction gives good corrosion resistance and is largely unaffected by changes in liquid density and temperature, offering outstanding accuracy with a bearing construction that gives an extremely reliable performance over long periods. Contrec’s 515 CB02 secure blending flow controller is designed to measure the volume flow in a main and process line using frequency flow inputs to determine the net volume flow. The operator can view the ratio of totals as well as the ratio of flow rates and the flow rate deadband and control responsiveness can be adjusted to reduce wear on valves. For security the instrument can be set to prompt for a valid ID-tag before a delivery can commence. The valid ID-tag also sets the pre-programmed target ratio percentage and is stored as a part of the logged transaction record, which can store 1,000 transactions with date and time stamp. As required by law operating in hazardous areas the flow controller has approvals for interference CE compliance, as well as ATEX, FM, CSA and SAA approved enclosures for hazardous areas. The UK, Europe and countries across the world are moving away from fossil fuels as part of a wider energy strategy to decelerate climate change and become more fuel secure by reducing their reliance on the producers of fossil fuels. Biodiesel already plays an important role in the UK’s energy strategy but with the focus on increasing the proportion of biofuels used across all transport networks, as well as for non-road mobile machinery, it will become even more prominent. To ensure biodiesel can meet the requirements set down by the government for sustainable fuels and also maintain the standards needed to fulfil engine manufacturers’ warranty criteria accurate blending is essential. Accurate instrumentation is therefore vital. And as these instruments are operating within potentially hazardous areas they also have to meet stringent health and safety requirements. The system installed at the Plymouth Oil Terminal meets all these requirements.
