No Need to Splash

Biodiesel doesn't typically go straight from the processor to the fuel tank. It has to be distributed, blended and then redistributed to retailers before it's sold to consumers. Managing the transfers and tracking the blending is important to growing a viable biodiesel industry.
By Jerry W. Kram | January 17, 2008
In competitive diving, splashes are a point deduction. For producers and distributors, splashing biodiesel is the most common way of making blended diesel fuel. If Archie Hendrix has his way, splashes at the biodiesel plant will be as frowned upon as a splash in a diving competition. Hendrix is vice president of sales for Honeywell Enraf, a maker of blending and measurement products.

Accurate measurement of fuels is the basis of the biofuels economic model, according to Hendrix. Knowing what's entering and leaving the biodiesel plant is key to understanding the operating costs and revenues for a business. "The true custody transfer measurement-where it changes hands-is what we talk about in the industry as the cash register between one customer and another," he says.

Many biodiesel processors still measure their sales by a weight-differentiation method. A truck is weighed on a scale, filled, weighed again and the difference between the weights is the amount of biodiesel that's been added. To make a blend such as B5, a proportional weight of biodiesel is splash blended with petroleum diesel. "At a loading facility, you would come in and get so much of the first product, let's say soy (biodiesel). Then you disconnect and pull the truck down a few feet and then connect up to the diesel and fill up the remainder of the compartment," Hendrix says.

Ethanol and petroleum distributors have long used blending systems to manage their fuel sales and deliveries. Biodiesel producers, which are generally smaller and newer than those industries, are still learning the ropes. "The biodiesel industry is still in its infancy," Hendrix says. "Where we come into play is typically at the terminal. As they add biodiesel to diesel fuel at the terminal they are going with ratio blending rather than the splash. Back at the small mom and pop producers, if they are blending biodiesel to get the tax credit, I think that's where you are seeing splash blending."

In Europe, Hendrix says, many biodiesel producers use high-accuracy tank level gauges to measure biodiesel transfers. This hasn't been widely adopted in the United States except for inventory control. "In this country we still want the dynamic measurement through a positive displace meter or some kind of turbine meter," he says.

Another method of blending fuels is sequential blending, which is similar to splash blending, but more automated. "Normally, you set a volume into the electronic preset device that has been preprogrammed for a certain percentage," Hendrix explains. "When you depress the start button it will open an isolation valve allowing one of the products to go through. The custody transfer meter accurately measures that into the truck and once that percentage of the total batch is reached, it will shut off. It will close that isolation valve and open the isolation valve of the other product and deliver that in the system."

Problems can arise, however, when the truck being filled isn't quite empty. Sometimes when trucks make deliveries to retail stations all of their product isn't dropped. "They leave 30 or 40 gallons of their product in the bottom of the compartment," Hendrix says. "So if they have a 3,000-gallon compartment for example and were doing a 10 percent blend, the first 300 gallons would be soy (biodiesel). Then the remainder would be diesel fuel. But because there was prior product in there you didn't have a full 3,000 gallon compartment. So you wind up having to shut down before that process is complete." In that situation, Hendrix says, you wind up with a truckload of off-spec product. "That's the disadvantage of splash and sequential blending," he says.

More Control
To avoid problems such as these, most producers should consider using ratio blending. In ratio blending, the producer controls both streams of the product so they leave the dispenser already mixed to the desired blend. Blending systems can be set for most of the common blends being marketed. Hendrix says there are three levels of blends in general use. Blends of 2 percent to 20 percent are done for retail sale and fleet fueling. Blends of 99 percent are done for tax credit allocation purposes. Some biodiesel producers blend between 20 percent and 90 percent as preblends based on customer needs. "We have the capabilities and the technical know how to blend basically any percentages," Hendrix says. "We just need to know that up front, and size the equipment so that it accurately covers the range customers need."

If lower level blends, such as B2 are a company's sole product, large in-line blenders may not be necessary, Hendrix says. Honeywell Enraf has long built high-capacity injectors for blending additives and dyes to fuels. They are used in ethanol plants to add denaturant to pure ethanol. These injectors use a process called pulse blending to achieve the same goal as an in-line blender. "Standard injectors are used to put detergent into gasoline and lubricity agents into diesel," Hendrix says. "They are very small meters with little solenoids that pulse and put a squirt of so many [cubic centimeters], that's being paced by the custody transfer meter."

The injector systems are precise but can handle only limited volumes. Smaller injectors are designed to add less than a half a percent of an additive to a fuel. High-capacity injectors can blend up to 5 percent of biodiesel to a fuel mixture. However, if a distributor intends to sell a wider range of blends, these systems will be undersized. "If you want to go from 2 percent to 20 percent, which is what is typically seen in the U.S., it is better to go with the full-fledged blender," he says.

Honeywell Enraf's main product for biofuels producers is its vertical blending skid. These systems can be configured for two or five streams of different products. These blenders, which the company configures for both biodiesel and ethanol terminals, blend the fuel in the loading area just before it's loaded into trucks for transport.

Weather is one of the primary issues that must be dealt with in handling biodiesel, particularly cold weather. Hendrix says the company modified its equipment to handle biodiesel in the cold when they started installing systems in Minnesota. "If you are familiar with soy oil, at low temperatures it becomes very, very viscous," he says. "With high viscosity it is very hard to blend that into diesel fuel and get a good homogeneous mix. For this project, they put insertion heaters into their large storage tanks. They were electrically tracing the pipeline going to the blender and insulating it. They asked us to redesign the blender so it could go through a 3-foot door and they physically put it into a small heated building."

While making the modifications, Honeywell Enraf was able to create a blender that could serve six loading arms at one time. That meant the facility was able to move more trucks per blender and ship its product more efficiently. The blending equipment can also be scaled up to handle railcar loading.

Ratio blending systems can incorporate tolerance alarms, so if there is a problem and the system gets out of proportion, it can be shut down and adjusted. That prevents off-spec batches, Hendrix says. The blending systems can also be configured to add biocides, cold flow additives, performance additives, dyes and markers, and other additives to biodiesel blends in an efficient manner. "We've done a lot of work with certain major oil companies that wanted to put invisible markers into their fuels to make darn sure the local service stations that carry their brand get gasoline or diesel from their terminals," Hendrix says.

Automatic control systems make using the blending equipment fairly straightforward, Hendrix says. The blending controller is preset for various blends and volumes. Card readers can be added to the system so drivers and vehicles are identified. The system can also be configured so a specific quantity of fuel is delivered to a specified driver or vehicle. The blenders are also equipped with safety equipment to shut off the system in the case of overfills or electrical problems.

Hendrix says the company has installed systems to deliver blended fuel for tiny distributors supplying a handful of local retailers, and major companies covering entire states. In either case, the system's terminal automation system (TAS) allows the distributor to monitor and control the operation of the system. "At the end of each load [the software] prints out a bill of lading of how much fuel was delivered," Hendrix says. "There are little TAS systems for mom and pop operations. When you get to the really large major oil companies, many times the TAS is still installed on a single computer, but its memory and capability is widespread. They can tie into a network across the entire country and monitor each terminal and each load. The capability is there depending on the extent and requirements of the customer." After installation, the maintenance on the systems is minimal, Hendrix says. "Most of the companies on a six-month basis are reproving the meters on the blenders, just to verify they are within the accepted tolerances," he says. "That is because if you are blending upstream from the rack meter, then the blender is not custody transferred."

For distribution terminals to seriously consider adding biodiesel blending systems there has to be a reliable supply and demand. Hendrix says the largest concentration of the biodiesel systems his company has installed has been in Minnesota and Brazil. "Brazil has been extremely large for us this year because they mandated biodiesel into all their diesel fuel. We have done a few systems in Texas and some for some co-ops in Indiana. But it has not been big like the ethanol to this point." n

Jerry W. Kram is a Biodiesel Magazine staff writer. Reach him at jkram@bbiobiofuels.com or (701) 738-4962.
 
 
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