- 29 March 2007 -
Developments in biofuel processing technologies
Demand for biofuels is surging worldwide, providing new and growing opportunities for manufacturers of pumps and other processing equipment. Bryan Orchard discusses the processes involved in producing biofuels, the special problems encountered and the solutions that have been developed by equipment manufacturers.
Recent advancements in distillation and blending technologies are being recognized as having an influence on the global proliferation of biofuels. Biofuels are not a new idea; in fact, Rudolf Diesel envisaged their significance back in the 19th century stating: ". the use of vegetable oils for engine fuels may seem insignificant today. But such oils may become, in the course of time, as important as petroleum and the coal tar products of the present time." Rudolf Diesel's first compression ignition engines ran on peanut oil at the World Exposition in Paris .
The current drive towards greater use of biofuels is being pushed by the diversification of energy sources using renewable products, as reliance on carbon-based fossil fuels becomes an issue, and the need to replace the MTBE (methyl tertiary butyl ether) component used in many of the world's petroleum products. The change from fuels with an MTBE component started as an environmental issue in locations such as the West Coast of the USA , New York City and Europe .
Ethanol & biodiesel
Ethanol has been recognized as the natural choice for replacing MTBE and the need to blend ethanol into petroleum products is now a global requirement. Brazil has long been the world's leader when it comes to fuel ethanol capacity, but the USA is poised to exceed this and other countries in the western hemisphere are rapidly growing their production.
The US ethanol industry is the fastest-growing energy industry in the world, with ethanol being blended in 30% of the nation's gasoline. As of May 2006 there were 97 E85 (85% ethanol and 15% gasoline fuel) plants in the USA with a total operating capacity of 4.5 billion gallons (US) per year. A further 35 are currently under construction, nine are being expanded and a further 145 each with capacities of between 7 million and 140 million gallons a year are at the planning stage.
European legislation has set substantial targets for the coming years and EU Directive 2003/30/EC promoting the use of biofuels in transport sets a target of 5.75% use by 2010. Standards for biofuels have already been established, with the undiluted base products being defined as B100 (100% biodiesel) and E100 (100% ethanol). Subsequent blending will modify this number: e.g. a blend of 80% petrol and 20% ethanol is defined as E20, or a blend of 95% diesel and 5% biodiesel as B5. Properties for unleaded fuel to be sold in the European Union are defined by EN228:2004, which allows up to 5% ethanol.
Biodiesel can be used in any concentration with petroleum-based diesel fuel, little or no modification being required for existing diesel engines. Biodiesel is a domestic renewable fuel for diesel engines and is derived from vegetable oils and animal fats, including used oils and fats. Soybean oil is the leading vegetable oil produced in the USA and the leading feedstock for biodiesel production. Biodiesel is not the same as a raw vegetable oil; rather it is produced by a chemical process that removes the glycerin and converts the oil into methyl esters.
For producers of biofuels, the massive growth signifies a greater requirement for pumps, mixers and integrated processing systems.
Blending biofuels
"Utilizing the current petroleum distribution infrastructure, blending is typically carried out at the storage or loading terminal," reports Jon Denis of Enraf Fluid Technology. "The most common locations for blending are the storage tank, the load rack headers or, most effectively, at the load arm. The most important requirement for this process is the accurate volume measurement of each product. This can be done through sequential blending or ratio blending, but most beneficially utilizing the side-stream blending technique."
Whereas petroleum products containing MTBE could be blended at the refinery and transported to the truck or tanker loading terminals via a pipeline or railcar, ethanol-blended fuel has properties that make this difficult. Ethanol, by nature, will attract any water encountered on route or found in storage tanks. If this were to happen in a 10% blend and the concentration of H2O in the blended fuel reaches 0.4%, the combined ethanol and H2O drops out of the blend, separating from the fuel and dropping to the bottom of the storage tank. The exact point of drop out depends on the ethanol percentage, make-up and temperature. The resulting blend goes out of specification and getting back to the correct specification requires sending the contaminated ethanol back to the production plant. "The solution to this problem," says Denis "is to keep the ethanol in a clean, dry environment and to blend the ethanol with the petroleum products when loading the transport trucks and tankers. Moving the blend point to the loading point minimizes the risk of fuels being contaminated by H2O."
To make this procedure possible, Enraf Fluid Technology has developed an ATEX Zone 1 certified Multi-Stream Ethanol Blender specifically for positioning at the loading rack. The blender utilizes multiple product streams, the monitored stream being referred to as the 'wild stream' and the controlled streams referred to as the 'blend streams'. The Micro-Blend controller monitors the wild stream and controls the blend stream to the programmed blend ratio.
In designing the Multi-Stream Ethanol Blender and also the recently introduced Micro-Blend system, Enraf Fluid Technology has overcome the major difficulties associated with mixing petroleum products with ethanol. "Experience has shown that, during the mixing process, the volume exhibits growth, with the amount of volumetric growth varying with multiple factors," continues Denis. "To capture this growth for fiscal purposes, it is necessary to ensure that the blend point is upstream of the custody transfer meter. With this arrangement, operators can capture whatever the actual growth turns out to be."
A further issue that Enraf Fluid Technology blenders have overcome is the slight residue that ethanol appears to deposit on the internals of the load rack piping. Although it is very slight, it can affect the accuracy of the turbine flow meter by shifting its K factor by a small amount. This mostly goes undetected until the meters are proved and then it is too late. Some terminal operators remove the meters from the line for periodic washing with H2O to avoid the K factor shift. The solution offered by these Enraf blenders is to use positive displacement (PD) flow meters as the slight film does not affect the accuracy of a PD meter.
Biodiesel processing
In general biodiesel processing, the fat or oil is degummed then reacted with an alcohol such as methanol in the presence of a catalyst to produce glycerin and methyl esters (biodiesel). Methanol is supplied in excess to assist in quick conversion and the unused portion is recovered and re-used. The catalyst employed is typically sodium or potassium hydroxide, which has already been mixed with the methanol.
Bran+Luebbe, an SPX Process Equipment company, is now offering biofuel producers customized production packages for high-efficiency and safe product blending. Whereas Enraf Fluid Technology is more focused on ethanol and biodiesel blending at the loading rack, Bran+Luebbe is targeting potential users of bio-generation systems looking to produce 5000-20 000 litres (although not necessarily limited to this volume) of biodiesel from either virgin oil or waste oil in a single batch.
The manual and fully automated systems developed by Bran+Luebbe bring together pumps and batch counters for dosing a specified volume into a tank, full PLC (programmable logic control) systems for controlling and monitoring pumps, valves and instrumentation or SCADA (supervisory control and data acquisition) based systems with data-logging capabilities for providing process traceability of the product.
"When blending biofuel with petrol or petrodiesel, the desired result is a uniformly mixed product," comments John Cousins, Bran+Luebbe systems engineer. "Using Bran+Luebbe or Plenty Mirrlees pumps combined with top-entry static mixers and filters, producers can achieve the correct blend both for batch and continuous operations."
Bran+Luebbe's systems range from simple, manually operated, single pump packages through to fully automated batching and mixing plant and are custom-built to meet the end user's requirements. The more complex biofuel systems typically feature multiples of pumps and mixers with the associated valves and instrumentation that are required in batching and continuous production plant. These essential components have been designed either for handling hazardous materials or for operation in hazardous areas where ATEX certification or US compliances will be required.
A typical plant will involve pre-filtering and then blending the raw material with methanol and possibly sodium methyl oxide using Bran+Luebbe Novados pumps (Figure 6). These components are then mixed in large tanks and left to settle. Using a Bran+Luebbe ProCam metering pump, the glycerin that settles at the bottom of the tank is removed. ProCam pumps are also used for injecting sulphuric acid or caustic for pH adjustment, methanol, a catalyst, denaturant and enzyme. The remaining methanol is subjected to a water wash to remove any further contaminants. Plenty Mirrlees triple-screw Triro pumps are employed to ensure a high throughput and high flow rate.
The Bran+Luebbe systems, whilst being larger and more likely to be used within a process plant as opposed to the loading rack, also overcome the problems of available space. All systems are skid-mounted to economize on footprint areas and height restrictions. Most importantly for the customer, the pump technology is well proven in the oil and petroleum industries where high-accuracy metering, leak-free operation and hazardous area compliance are essential issues.
Whereas fuel produced from agriculture has only had marginal use in the past, in today's climate there are political, environmental, legislative and financial benefits for using biofuels. With oil prices remaining high and very unlikely to reduce, demand for biofuels will continue to rise and provide exciting growth prospects both for investors and equipment manufacturers. Enraf and SPX have many years of experience with traditional fuel technologies and are ideally placed to meet the demands of this growing market with both existing products and new developments.
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