A novel re-refining process uses solvent extraction and distillation to process used oil at lower cost and much smaller volumes than existing technology will allow.
Current technology typically requires minimum processing volumes of 40,000 gpd for economically viable operation. The new process, developed by Interline Resources Corp., Alpine, Utah, can operate economically on volumes as small as 5,000 gpd.
Interline started up a commercial-scale re-refinery in Draper, Utah, near Salt Lake City, in October 1993.
The new process has eliminated the need for thin-film evaporators, as well as the very expensive hydrofinishing step.
The elimination of this capital-intensive equipment is made possible by the patented Mellon Process. In this process, the water, additives, and solids are removed at ambient conditions, thus allowing the resulting oil to be handled in traditional distillation equipment.
HOW IT WORKS
As shown in Fig. 1, raw waste lube oil is mixed with the propane-based solvent.
Interline chose the solvent for its high selectivity of hydrocarbons and its rejection of metals and aromatic compounds. These metals and aromatics are retained in the asphalt residue, which passes all of the U.S. Environmental Protection Agency's test for toxicity characteristics.
After a brief settling period, the resid/water phase is pumped to the resid/,vater separator, where the water can be drained for disposal.
The solid resid is transferred to the asphalt mixing tank, where it is combined with the bottoms from the vacuum distillation column. The resulting mixture then can be sold as flux for asphalt operations, or as an asphalt modifier for paving asphalt.
The extraction process takes place at ambient conditions. Because the used oil and additives are not heated, the odors-and the coking and corrosion that accompany the traditional used oil distillation process-do not exist.
The oil/solvent mixture is pumped to the solvent stripper, where the solvent is removed from the oil, condensed, and reused. The oil is then flashed at atmospheric pressure to remove the light hydrocarbons.
The remaining oil is then distilled under a vacuum, resulting in a high-quality base oil lube stock, plus diesel and bottoms products.
Because the process is a closed-loop system, it emits no airborne pollutants, says Larry Macfarlane, Interline's director of communications. And its only by-product-a chemically benign semisolid-can be utilized as a base substance in rooting and street-paving applications, says Macfarlane.
YIELDS
In any re-refining process, it is the impurities (water and fuel) in the collected waste which have the greatest effect on yields. Interline says typical yields from the Draper plant are:
- Water-5 vol %
- Fuel-8 vol %
- Lube base oil - 75 vol %
- Asphalt flux - 12 vol %.
These yields are based on waste oil collected in and around the Salt Lake City area. These oils contained relatively small amounts of water and fuel contaminants.
Interline, however, claims the process can handle as much as 20% water in the waste oil feed.
COSTS
Total operating costs for a unit processing 14,000 gpd waste oil are 10.37cts/gal. The labor component of this cost is based on one operator, 24 hr/day, 7 days/week.
The labor cost (3-57cts/gal) is fixed; it is therefore lower for units with greater capacity and higher for units with lower capacity. Royalty payments are 7cts/gal.
Building an elementary re-refinery costs a minimum of 515 million, says Interline. But a 14,000 gpd plant based on the new technology costs only about $1.6 million, according to the company. (A 6,500 gpd plant is estimated to cost $1.1 million, and a 30,000 gpd plant, $2.5 million.)
These costs are for the processing equipment and technology fee only, and do not include the cost of tankage or the fired heater.
OPERATING EXPERIENCE
Interline has examined its operating results for the first 5 months of operation of the Draper plant. Lube oil base stock qualities are shown in Table 1.
Product quality and extraction capacity have exceeded initial projections, says the company, while operating costs meet the requirements for a 3-year payout.
Interline has sold sublicensing rights to Western India Group, New Delhi. The agreement grants Western India Group the right to use the technology in plants in the Middle and Far East.
Interline president Mike Williams says the company will receive $1 million for the rights to construct, own, and operate plants in India, Saudi Arabia, the United Arab Emirates, Oman, Kuwait, Iran, Thailand, Viet Nam, Malaysia, and Qatar.
Interline also will be compensated for engineering the plants, at $50,000 per plant, or 10% of the total installed cost of the "first perc" processing equipment, whichever is greater. ("First perc" refers to the first stage of the process, in which the solvent is percolated with the oil as part of the extraction process.)
The company also has the right to participate in as much as 50% of the ownership revenues of any re-refining plant constructed or acquired by Western India Group as a result of the agreement.
During the first year of the contract, says Williams, Western India Group will install facilities with a minimum total feed capacity of 100,000 gpd. The organization will increase the combined capacity of the plants by 100,000 gpd in each succeeding year of the contract until total capacity is 500,000 gpd.
According to Nandan Gadgill, chairman of Western India Group, the 500,000 gpd rate will likely be reached in the first year.
Interline will receive a net royalty of 1cts/gal of processed oil. And if any of the processed oil is used or sold as a base oil, Interline will receive an additional 4cts/gal.
Interline's Macfarlane says negotiations are under why with a number of U.S. companies, as well as firms in Australia, England, South Korea, Cyprus, Botswana, China, and South Africa.
Copyright 1994 Oil & Gas Journal. All Rights Reserved.
