Intern Project Summary, Minnesota Technical Assistance Program, University of Minnesota
Company: Marathon Ashland Petroleum LLC; St. Paul Park, Minnesota
Results
Generally, larger equipment is repaired and serviced in-place at the plant. This generally involves external surface cleaning before equipment is disassembled and internal cleaning as needed for repair and reassembly. External cleaning has been done using petroleum distillate and terpene-based spray cleaners. Thirty-one drums of terpene-based cleaner were used in 1997. By the start of the intern project it was suspected that the terpene solvent could be impairing the biological portion of the refinery’s wastewater treatment plant.
Most purchases were handled through the refinery purchasing department. The intern was able to confirm early in the project that individual shops were occasionally circumventing purchasing controls by buying some products directly. This practice was stopped by educating employees on the purpose of controls and eliminating ways to circumvent them.
In order of priority, the intern’s objectives were to:
Of the 29 aerosol products in stock containing chlorinated solvents, 17 were redundant or no longer used and were eliminated without replacement. A testing program identified replacements for eight of the other aerosols. The mechanics set the criteria for each product and evaluated the effectiveness of a number of alternatives on actual jobs.
Aerosol replacements eliminated 39.5 gallons per year of chlorinated solvents from the workplace. Purchase costs increased for two products, but net savings for the eight replacements was $330 a year. No change in labor requirements was seen.
Replacements for four, little-used products were not found (these were "canned air" dust blow-off using a tetrafluoroethane propellant; nonflammable contact cleaner for use near charged circuits using HCFC 141b; adhesive using trichloroethane; and gasket remover using methylene chloride). The gasket remover is still a priority to replace because it leaves a residue that is likely to require wipes, which will be a listed hazardous waste as long as the product contains methylene chloride. If a substitute can be found, rag disposal costs are expected to decline.
The largest aerosol use (almost 1,500 cans in 1997) was a product with a very low flash point that is a blend of flammable solvents including xylene, acetone and hexane. The second most common aerosol (170 cans) uses a terpene solvent. Both are used interchangeably, except when an application requires a dry surface quickly then the flammable aerosol is used. The intern proposed that the maintenance staff use the terpene aerosol first—it evaporates more slowly so it stays on the part longer where it can function as a cleaner and is breathed in less by the workers. Then, they should follow the cleaners with the flammable aerosol—which now would function more like a rinsing and drying agent. This procedure requires training and ongoing commitment by workers and management. It may be able to save $4,500 a year and reduce aerosol disposal by 720 cans per year—35 percent.
Parts Washer
Four parts washing options were
researched as alternatives to the contract parts washer service. Two parts washer systems
with advanced solvent filtration were evaluated. Advanced filtration systems circulate
solvent through a 50 micron cartridge filter, much finer filtration than the coarse bag
filters found on typical parts washers. Also, two distillation options were reviewed: 1)
distillation augmenting the parts washers, and 2) a parts washer system with distillation
integrated into the design. All of these systems would greatly lengthen the life of the
solvent, decrease the volume of waste and lower operating costs. They require a slight
increase in labor to maintain the washer.
Best Options. The parts washer system providing the greatest return to Marathon Ashland Petroleum used both a 50 micron cartridge filter and a small treated clay filter to remove some oil from the solvent. Complete conversion to parts washers with filtration was estimated to lower operating costs from the $14,400 a year service contract to $5,200. The cost includes filter and solvent purchase as well as disposal, assuming a two year solvent life, 20 percent-per-year loss to dragout and monthly filter changes. The intern recommended purchasing eight parts washers of four different sizes, costing $13,600 including the initial charge of solvent and filters. The purchase would yield a payback of 1.5 years. The two largest washers would have a lift platform for parts which would ease loading and unloading as well as allow improved agitation and cleaning.
Since the end of the intern project, two parts washers with filtration were purchased and installed, costing $2,500. A third parts washer was retrofitted for filtrations, costing approximately $150. All functioned as well—or better—than expected. The three washers displaced service contracts for four washers, saving $7,850 annually. Operating costs are estimated at $1,400 a year. First year net savings should be $1,300 and increase to $6,400 per year there after.
Aqueous Option. Aqueous cleaning in cabinet spray washers was considered as an alternative to solvent parts washers. Purchase and maintenance cost were high compared with solvent parts washers. The refinery looked into this approach further and tested one cabinet washer which should replace the remaining large contract parts washer, costing $4,100 annually. The purchase cost of this cabinet spray washer may be as high as $15,000. In addition to the savings from eliminating service contract costs, the washer could save approximately $12,000 a year in labor, improve productivity and reduce equipment downtime if the maintenance mechanics no longer need to hand scrub parts. The refinery plans to purchase a spray cabinet washer in calendar year 2000.
Spray Cleaners
The intern tested three aqueous cleaners, two of
which look like promising substitutes for the terpene-based spray cleaners. Two of the
aqueous cleaners can be applied as a foam that adheres to vertical surfaces for several
minutes, giving enough contact time for the cleaner to work. They can then be rinsed off
with hot water from a hose or pressure washer. The refinery purchased a foam generator
costing approximately $750 for application of foaming cleaners. One product received
significant use during the fall when much of the refinery was shut down for repair and
upgrade. The refinery staff that have used this cleaner with the foamer have described the
result as "requiring less chemical, less time and less water while providing better
results" compared to the terpene-based cleaner. Savings might be as high as $28,000 a
year if 1998 purchases can be cut in half.
The third cleaner, a soybean-derived solvent emulsion, was found to be very effective in removing heavy oils and asphalt up to 1/8 inches thick. The refinery was wanting to find an acceptable substitute for the kerosene-based cleaner currently used for this purpose. The refinery has tested several different formulations of these cleaners and plans to change to an aqueous cleaner as existing inventories of the kerosene-based cleaner are depleted.
Overall Results
The changes implemented as a result of the intern project at Marathon Ashland Petroleum
will result in net operational savings of $6,700 a year. Other changes have been made or
are in progress which, if implementation goes as predicted, will result in further
operational savings of $32,500 a year.
Without the intern, Marathon would probably have worked on their project objectives over a five year period. But, the engineering intern allowed a concentrated review of alternatives, a focus on maintenance cleaning issues and faster movement toward implementation.
MnTAP has a variety of technical assistance services available to help Minnesota companies reduce and manage their industrial waste. If you would like assistance or more information about MnTAP’s Intern Program, call 612/624-1300 or 800/247-0015 from greater Minnesota.
This project was conducted in summer 1998 by MnTAP intern David Bittrich, a chemical engineering senior at the University of Minnesota.