Pumping biofuels

Under the Kyoto Protocol, the European Union has a goal of 20 % for renewable energy’s share of total primary consumption by 2020, and a binding minimum target of 10 % for the share of biofuels. These ambitions, along with the world’s growing demand for energy, high oil and gas prices, plus instability in many […]

Under the Kyoto Protocol, the European Union has a goal of 20 % for renewable energy’s share of total primary consumption by 2020, and a binding minimum target of 10 % for the share of biofuels. These ambitions, along with the world’s growing demand for energy, high oil and gas prices, plus instability in many of the oil-producing countries, are driving strong demand for biofuels.

Many biodiesel production facilities have been built in Europe in recent years, all relying heavily on pump technology. KSB, for example, has already installed around 1,500 pumps for these applications.

Biodiesel consists of fatty acid methyl esters. The raw material – animal or vegetable oil, or fat – is mixed with methanol and a catalyst in a reactor where the triglycerides react with the methanol to form methyl esters and glycerine, a valuable by-product. The entire process, including the recovery and glycerine removal stages, generally takes place in ambient conditions.

Metal pumps with a shaft seal are used to handle the feedstock, such as soybean or rapeseed oil. Standard chemical pumps or pumps with standard hydraulic systems for water applications can be used for this purpose, selection being mostly based on the biodiesel plant operator’s background: Operators from the chemical sector are most likely to opt for a standardised chemical pump, while investors with no chemical history prefer the lower-cost system for water applications.

However, special pumps are required for the handling/recovery of methanol, as this process has to comply with regulations such as the German Clean Air Act (TA-Luft).The pumps used must feature a high level of sealing to prevent large amounts of methanol or catalyst leaking to the outside. Standard chemical pumps – if provided with a double mechanical seal – may also be used at this stage, but this involves higher costs and more maintenance.

Both can be avoided by using seal-less pumps, which are available in two different drive versions: On the one hand, pumps with canned motors are used in biodiesel plants. In this type of pump, the inner rotor and, hence, the pump, is driven by an electrical rotary field, in which case the inner rotor runs in the fluid pumped. The drive concept provides a high level of security both against leakage and efficiency. On the other hand, mag-drive pumps offer an alternative. They have the advantage of having only two static seals, which ensures a high degree of security against leakage.

High demands are placed on the pump materials in the purification columns section. Depending on the process, aggressive acids are used to separate water and glycerine from biodiesel. The pumps at this stage are partly exposed to pure hydrochloric acid. Special high-quality material must therefore be used for the pumps: plain cast iron lacks sufficient resistance to acids in the long term.

Pumps installed in the corrosive environments of the purification columns section are, therefore, made entirely from duplex steel. The material is resistant to all kinds of chloride-containing fluids and, therefore, to hydrochloric acid.

The removal of glycerine is yet another significant challenge to the pump technology. At this stage, salts included up to a concentration of 35 weight percent, and partly present even in crystalline form, are separated from the fluid. In order to resist the abrasion caused by the crystalline solids, so called non-clogging impeller pumps are used. The centrifugal pumps in close-coupled or back pull-out design are specially designed for the handling of corrosive and abrasive fluids containing slurries. If necessary, the duplex steel used for the pumps can be subjected to subsequent heat treatment to further increase their wear resistance.

Biodiesel is, however, only one of the possible alternatives to fossil fuels – particularly in Europe, as its growth rate has passed its peak, at least in terms of new production plant construction. At present, more bioethanol refinery plants are being built. The importance of this “petrol substitute” is increasing following its use as an ecological alternative for many years in South America and Scandinavia.

Bioethanol is mainly produced from the fermentation of sugar- or starch-containing foodstuff. In Europe, more and more sugar and starch manufacturers are discovering this market. Basically, the process can be divided into the actual ethanol production (fermentation) itself, the ethanol purification and the stillage treatment – a process which principally takes place in any brewery.

Europe’s main feedstocks for bioethanol production are cereals and sugar beet. They are ground and mixed with water and pumped to the mash columns where the fermentation takes place. At this stage, non-clogging impeller pumps are again used to ensure safe handling of the solids-laden fluid. Because of the fluid’s high viscosity, the pumps require large impeller passages and correspondingly robust bearings.

Standard chemical pumps are again used for the process after fermentation. They withstand the temperatures of up to 180°C encountered at this stage, whereas standardised water pumps can only be used up to about 120°C. Between 1.5 and two tonnes of water per tonne of cereals are processed on average by evaporation, which is why mainly pumps with standard hydraulic systems for water applications are used.

To provide for the large flow rates required for cooling, ‘cooling water pumps’ are also used. These pumps are normally designed for the handling of cooling water in power plants. They can deliver up to 2,800m’/hr of water, allowing for fast cooling after the distillation phase. Seal-less pumps with mag drives and/or canned motors are then used for the alcohol storage tanks as ethanol also falls under the provisions of the TA-Luft. Moreover, due to their drive concept, the seal-less pumps feature particularly low noise operation – a big advantage, given that ethanol production equipment is usually installed in the open air.

Bioethanol production plants must, at least in part, meet applicable food contact regulations, and are, therefore, made of stainless steel. Many operators install the pumps without a foundation, so they are mounted on feet made of stainless steel, allowing the floor underneath to be hosed down safely with water without affecting the pumps.

Right now, research is underway on another kind of biofuel, synthetic BTL (biomass to liquid) fuel. Its production process can accept a far wider range of biomass as feedstock than is suitable for biodiesel or bioethanol. Besides wood and wood residues, cereals, straw or whole plants can be used.

Different technologies to produce these synthetic fuels are, for the most part, still at the research or development phase. For example, the extremely aggressive pyrolysis oils produced in the process are a challenge for pump technology. The high temperatures also place special requirements on the materials used for the pumps.

World leader Argent keeps biodiesel flowing

The most sustainable biodiesel in the world is made in Scotland by Argent Energy, according to a panel of experts at the recent World Biofuels Markets expo held in Belgium.

Argent is Europe’s largest biodiesel processing plant, producing 45ktpa of biodiesel from tallow and used cooking oils. Its raw materials are always hot and aggressive, attacking rotors and seals, and there is the constant possibility of transfer pumps becoming clogged with wax and fatty deposits.

Frequent cleaning of the rotors was required with the original pumps supplied . This led to the installation of AxFlow WCB Universal II rotary positive displacement pumps. Several types of AxFlow WCB pump are now used on process liquids at Argent Energy, its smooth product flow and large cavities allowing efficient pumping of slurries and viscous liquids.

Providing flow rates of 1,000-1,500litres/hour, the WCB U45 pumps are employed on the GLP acidulation and neutralisation lines where the fluid has a particularly abrasive nature.

WCB pumps are also used to separate the different phases of heavy and light oils emerging from the distillation column. With their seals tolerating operating temperatures of up to 120°C, these pumps have also signifikcantly improved the operating efficiencies of the plant and are reported to have been running trouble-free since their installation.

On the merry-go-round

Mono Pumps has produced a solar powered pump in co-operation with Water For All, a non-governmental organisation that provides access to clean drinking water to schools and communities across Africa.

The Fun Pump, as it is termed, is a borehole pump, storage tank and tap, powered by a 160W solar panel. Depending on the depth and yield of the borehole, this can produceup to 5,000 litres of clean drinking water a day.

But the Fun Pump also has a special feature: a green, blue and yellow merry-go-round, straight from a standard UK-style children’s playground. When the children are playing on the merry-go-round, a generator driven by the rotation supplies the power to pump more water, and output increases approximately 20%.

Virgin Atlantic Airline staff recently sponsored two of these pumps for clinics in sub-Saharan villages in Kenya, and some cabin staff visited one Fun Pump that supplies a school and a clinic at Kyeleni. The next nearest water tap is some 8km away, and so the Fun Pump has eliminated the daily trek for wives and daughters to fetch water for their families. Now, adults and children alike use the merry-go-round: it was the first piece of ‘purpose-built’ playground equipment they had ever seen.

Vane pumps the answer for Peter Cremer in the US

Peter Cremer North America LP, based in Cincinnati, Ohio, is one of the largest biodiesel producers in the US with a production capacity over 30-million gallons per year. The company uses vane pump technology throughout its plant due to the pump’s consistent performance and handling capabilities for low viscosity liquids.

“Our entire operation uses NP2 or NP4 Blackmer vane pumps,” explained Mike Doll, PCNA’s plant manager, “from railcar loading/unloading to sending the product to our production building and back to storage, or loading it onto the trucks for delivery. Over the years we’ve tried different types of pump technologies, but the vane technology works the best. Some of the pumps might be geared differently in different applications, but these are perfect pumps for our needs.”

At PCNA, soybean oil feedstock is shipped into the facility by railcars, which typically hold 20,000 to 25,000 gallons of soybean oil.

“The railcars enter the plant and are top-unloaded, which is something you probably won’t see anywhere else,” said Doll. “The Blackmer vane pumps have such a tremendous suction ability that we are able to load and unload from the same point. Because of their suction lift capability and high performance characteristics, the pumps enable us to unload these railcars very efficiently.”

After the oil is unloaded, it is pumped to its production facility via a mile-long pipeline and processed into methyl ester, which is sent back to new storage tanks via a different pipeline. Once the B100 neat biodiesel is transferred into the new storage tanks, the methyl ester is blended with additives before being sent out to a third-party testing laboratory to verify that each lot meets the requisite ASTM D6751 specifications.

“The infrastructure that’s needed to produce 30 million gallons of biodiesel per year is significant. Not everyone takes into consideration all of the piping, pumps and equipment that’s needed,” said Doll. “We selected vane technology for our pumps because of their superior thin liquid handling capabilities, seal integrity and uptime performance, and have properly configured our piping and production equipment to provide optimum results.

“Having the right blend is extremely critical to the quality standards of the fuel. Because of this, for blending operations, I would strongly recommend the use of vane pumps to help ensure biodiesel blend quality standards,” concluded Doll. “By virtue of their design they have self-adjusting vanes that ensure volumetric consistency over time. In our experience, other pump types wear over time, which can result in blending inconsistency.”