Cleaner and Clearer
In a challenging economic environment, producing a top quality product is one way to maintain a competitive edge. For biodiesel producers, that means finding the most economical way to wash and polish their crude biodiesel to the highest possible standard. Schroeder Industries says its system can produce clean biodiesel quickly and inexpensively.
A key step in producing quality biodiesel is washing to remove impurities such as excess caustic catalyst, methanol, soaps and free glycerin. Along with filter clogging, unwashed biodiesel can cause seal failures, clogged fuel injectors, damaged fuel pumps and other problems in diesel engines. In the United States, the most common method of removing these impurities is wet washing. Wet washing uses water as a solvent to carry away the impurities, leaving the pure biodiesel behind. But wet washing has disadvantages. It's a time-consuming step requiring many hours for the biodiesel and water to completely separate. Wet washing can also leave residual traces of water in the fuel. "In drier areas you may have water restrictions," Benzies says. "You may need some treatment if you have really hard water. But the real problem comes with the high levels of soaps and emulsions that form if the wet wash isn't performed properly. You then have a risk of having a very poor separation of the fuel and the water and an extended separation time. The final problem is the disposal of the hazardous effluent waste which is the byproduct of the wet wash. It may be that you have to wash seven or eight times in order to achieve clarity."
Dry washing is an alternative. In dry washing, an adsorbent is added that attracts and combines with impurities, separating them from the biodiesel. Some systems use ion exchange resins as the adsorbent (see "Waterless Washing Machine" in the May 2007 issue), while others use a mineral called magnesium silicate, one type of which is marketed under the name Magnesol by the Dallas Group of America Inc. Recently, lubricant purification specialist Schroeder Industries became the exclusive distributor for a Magnesol-based dry-wash system created by Filtertechnik. "Having looked at various dry-wash systems including competitive silicates and resin systems, we decided to run with the Magnesol product based on several factors: first and foremost, it's one of the few products that had independent verification put on it," Benzies says. "It's one of the few products that published performance data, which is absolutely vital."
Schroeder's system works in a similar fashion to other dry-wash systems (see "Adsorbing It All" in the March 2005 issue). After crude glycerine is separated and removed, and excess methanol is vented, Magnesol powder is added to a tank of biodiesel and agitated with a mixer for about 25 minutes. The process uses 0.5 percent to 1 percent Magnesol by weight, depending on the level of contaminants in the batch of biodiesel. So, 2,000 pounds of biodiesel, which is about 265 gallons, would require 20 pounds of Magnesol. The powder attracts polar molecules and separates them from the nonpolar biodiesel. Methanol, water, glycerin and catalysts are all polar molecules. "That's effectively what happens when the Magnesol comes in contact with the crude methyl ester," Benzies says. "It adsorbs all the impurities."
After agitation, the biodiesel is circulated through Schroeder's wash columns to filter out the Magnesol and its cargo of contaminants. "Moving across to the wash stage, it is at this time when we start to see things improving in terms of visual clarity," Benzies says. "The advantage of using our systems in conjunction with Magnesol is that the towers enhance the clean-up process. At this point we see a rise in clarity for the first time. The milkiness and cloudiness that you see in your crude methyl ester is now replaced by a bright, golden crisp color."
After the biodiesel reaches the desired level of clarity, it is transferred to a final polish tank. Schoeder recommends that all biodiesel go through a polishing step to maintain stringent quality standards, irrespective of the washing method. They also encourage biodiesel producers to be rigorous with their own quality testing. "We are the only producer of filter and purification systems that actually encourage producers to do these tests simply because they don't lie to you, and will tell you exactly how good your purification method is," Benzies says.
Schroeder's polishing filter units can handle from 500 liters per hour (132 gallons per hour) to 2,500 liters per hour (661 gallons per hour) and remove residual particulates and water. An innovative part of the units is the built-in monitoring systems that include particulate counters and water monitors. The monitors display the level of contamination on liquid crystal display screens and can be downloaded to a computer for real-time monitoring and batch tracking. The system can also send e-mail alerts and even download alerts to cell phones. "Archiving traceability, building up records, having control of your production process is absolutely important," Benzies says. "If someone has problems with their vehicle they instinctively blame the fuel. That's one of the things producers have to keep in mind, they need to have some sort of in-house traceability that says that that particular batch was a good batch."
Magnesol was compared with wet washing by researchers at Iowa State University, Benzies says. The results showed significant results after just 20 minutes of processing. "The performance data showed a massive decrease in glycerin and the moisture removal capability and methanol reduction," he says. "More importantly, if you look at the soap reduction capability, it's just staggering in a short space of time to get from a high level to an acceptable level. That is one of reasons we have embraced this dry-wash medium."
The dry-wash systems have other benefits. The cost of operating a dry-wash system is lower than a wet-wash system. Disposal and water treatment costs are also lower with a dry-wash system. Lower cost is not the biggest selling point, according to Benzies. "In our opinion, producers change from wet to dry for two reasons, speed and fuel quality" he says.
Filtertecknik compared biodiesel produced by its system with other commercially available fuels, with surprising results, Benzies says. "When we did particle counts on standard petrodiesel, it was shocking how dirty it turned out to be," he says. "Now we are under no illusions that it didn't leave the refinery at this cleanliness level, but with so many underground storage facilities and dirty nozzles, this is the cleanliness level that is being used in a lot of the motor vehicles today." Wet-washed biodiesel was cleaner than the petrodiesel. The dry-washed biodiesel was cleaner still, with a lower moisture level than the wet-washed biodiesel.
Since 2004, biodiesel producers in the United Kingdom have adopted dry-wash systems. That year, 70 percent of producers used wet washing and 20 percent didn't wash their biodiesel at all. By 2006, 43 percent of producers surveyed were dry washing their biodiesel and 47 percent were still using wet-washing systems. "It wouldn't surprise me if the dry systems were to surpass the wet systems [in 2007]," Benzies says. The reasons for this shift were because wet-wash producers were experiencing problems, dry-wash systems have now come into their own and are available on the market, and industry standards have become more stringent, he says.
U.S. biodiesel producers are also interested in this new technology, says Jonathan Dugan, a product specialist with Schroeder Industries. However, with the current financial challenges facing the industry, producers are being cautious with capital investments. He says they talked to a couple of producers about developing the technology. "There has been some frustration with folks on the capital equipment side asking 'Why isn't anybody buying anything?'" Dugan says. "Until the government puts on a tax credit or we figure out a cheaper feedstock, it's a little bit of a waiting game. But if crude goes up another $20 or $30 we could see a swing where biodiesel is profitable again. At this time, people aren't interested in retrofits. They are more interested in paying for the technology they've already purchased."
In addition, many producers are hesitant to change from a well-established process. "Some of it has been slow going," Dugan says. "The acceptance has been good. But it has been confusing for some about how they would apply it. Water washing has been the de facto standard for quite some time. Adsorbent technology is new to folks so we are trying to explain to them how it works and why it works and how it can save them money. But it's coming along."
Tightening water supplies, plus the cost of treating effluent in many areas of the United States will be a factor in biodiesel production, Dugan says. He described a visit to a biodiesel producer who used wet washing largely because he had a favorable agreement with the municipal water and sewer service providers. "They said if the local municipality hadn't been so gracious in helping to get the business started, they would have had to go to Magnesol and a dry-wash process," he says. "When they build their next plant, it may be a different story. It has everything to do with the local rules and government."
Despite the current challenges in the biodiesel industry, there are still a lot people interested in building new plants. These companies are taking a good hard look at using dry washing, Dugan says. "We have spoken to a lot of folks," he says. "We have our systems specified into a lot of medium-sized plants and we're talking to some of the larger plants. I think that as soon as it makes sense to build up the industry capacity, we will see an influx of business that we can't even imagine. That's really exciting for us."
Jerry W. Kram is a Biodiesel Magazine staff writer. Reach him at firstname.lastname@example.org or (701) 738-4962.