A world-class processor of titanium scrap had a wash system whose cleaning solution was becoming contaminated with both free floating unemulsified tramp oil and emulsified water soluble oil that was being washed off of titanium turnings. As the level of oil contamination increased over time in the wash solution, cleaning effectiveness diminished. The processor uses a metric, which they refer to as the 'carbon number' for measuring their cleaning efficiency. It measures the amount of oil present on the titanium turnings after they are cleaned. The carbon number of the cleaned, recovered titanium turnings exiting the wash system worsened over time and the client wanted to eliminate this problem, which was associated with the critical measure of the end product quality. Subsequent rinses were becoming contaminated from the drag out of both types of oil, thus causing the discharge of rinse water to the local sewer to approach and, in some cases, exceed discharge limits. Ultimately, dumping the spent wash solution and recharging the wash tank with a fresh wash solution was the answer to these operational problems. However, this approach for servicing the wash tank was expensive. There were labor costs associated with dumping, cleaning, and recharging the wash tank. Dumping resulted in disposal costs for the waste wash water. Recharging the wash solution resulted in added chemical costs for new detergent and reheating the wash solution resulted in higher energy costs. Additionally, production was lost due to downtime for these wash tank services.
The titanium scrap metal processor began a search for a better solution to the problems associated with the wash system. The objectives were to extend the useful bath life, reduce the wastewater volume generated, ensure the quality of the washed turnings exiting the wash system, and reduce the drag-out of oils from the turnings into the rinse water to help meet discharge regulations. They selected the AquaChemical Microfiltration System from Separation Technologists, Inc. to work in conjunction with the Suparator from Aqueous Recovery Resources, Inc. (ARR, Inc.) to accomplish these goals. The AquaChemical system employs a ceramic microfiltration membrane to filter and recycle aqueous alkaline cleaning solutions. The microfilter has a porosity of approximately 0.2 microns. The AquaChemical system removes emulsified oil from wash water, but is not designed to remove excessive quantities of free floating, unemulsified tramp oil, which is almost always present in these operations. These types of oils can reduce the AquaChemical system's throughput if not properly pretreated. A device called the Suparator, manufactured by Aqueous Recovery Resources, Inc., of Bedford Hills, NY accomplishes this objective very well by removing unemulsified tramp oil from the wash solution and enables the AquaChemical system to work at its optimum level.
Suparator's unique technology exploits Bernoulli's Principle to scalp oils from a flowing stream of wash solution. In addition to being the only system in the world to strip oil from water without utilizing media of any kind, Suparator functions at an exceptionally low cost of operation. The Suparator system also produces a dry stream of recovered oil that is currently sold by the processor to a waste oil blender for approximately $0.40 per gallon, which further lowers the total cost of ownership for the pre-treatment system. ARR, Inc. has worked with several facilities that reprocess titanium and understands the very heavy dirt and oil loads that can come in with titanium turnings and chips. The wash solution for these materials can become saturated very quickly with these soils and rapidly becomes ineffective. Poor cleaning results in contamination being dragged into subsequent rinsing, melting, and forging processes. Increased contamination means the recycler receives a lower price per pound for the recycled materials.
The AquaChemical microfiltration system employs a 'cross-flow' type of filtration device. This differs from conventional filtration, such as cartridge or bag filters. With cross-flow filtration, the contaminated fluid flows across the filter media surface in a tangential direction. The filter media, or microfiltration membrane in this case, acts as a barrier to emulsified oil and suspended solids and rejects these species. The bulk flow sweeps the membrane surface clean and keeps these rejected contaminants from gathering on the microfilter membrane surface. This keeps the membrane surface relatively clean, allowing for consistently high rates of filtration. Also, cross-flow ceramic membrane filters do not require regular replacement. Typically, the membrane is washed, regenerated, and reused for periods approaching 5-10 years before replacement is needed.
The Suparator skid includes a specially designed interface between the processor's primary wash solution tank and the Suparator skid, where the precision separation of oil and wash solution occurs. The solution is pumped from the solution holding tank to the Suparator skid, using a specially designed, non-mixing pump. At just 2 feet by 5 feet the unit was easy to install. Separation Technologists, Inc. worked closely with ARR, Inc. to develop a properly sized Suparator to handle the heavy dirt and oil load of the process. They selected the Series 84, Model 540 system, one of ARR's standard systems, that comes complete with its own pump and variable speed drive controller. By removing gross oils from the feed-stream before being pumped into the AquaChemical's process tank, the Suparator eliminates membrane fouling caused by unemulsified tramp oil. This important pretreatment step reduces degradation of the filtration rate that can cause the microfilter system to experience difficulties processing water with the level of unemulsified tramp oil contamination seen in chip washing and recycling facilities. By reducing the tramp oil loading from the wash solution before the AquaChemical microfiltration system processes it, the AquaChemical system can run longer between required membrane cleanings, thus substantially reducing the total waste volume generated by the processor. The oil-stripped wash solution from both the Suparator and AquaChemical systems is returned to the wash tank and continuously reused to clean new batches of titanium scrap. Total oil removal is critically important for the processor, as their final product is graded by carbon content. Carbon content, in this case, is due to residual oil contamination, so the lower, the better.
The AquaChemical system itself is relatively easy to operate. The system consists of a process tank, a circulation pump, and a bank of microfilter modules. With fluid level indicators and switches in the process tank and a transfer pump connected to the wash system, the AquaChemical system can run continuously, 24 hours per day, 7 days per week, with minimal operator involvement. The microfilter membrane provides consistently clear filtered product water through the entire process, since it is a mechanical separation process, as compared with chemical treatment, which relies on a phase change to occur. This treatment approach allows water and soap to pass through the AquaChemical system's microfilter elements, while removing water-soluble oil and solids from the wash solution. Thus, the wash solution is filtered and reused, while the oil contaminants are removed from the wash solution.
The result is that the processor is washing titanium turnings with a wash solution that is consistently better over the long-term than before, which has resulted in fewer interruptions and better carbon numbers for the recovered turnings from the wash system. The wash solution itself is cleaner, with regards to oil content; thus the rinse water has less oil content from drag-out than previously seen. The drying process now produces less smoke from oil residue burning; thus the working environment has improved, which was an unforeseen, but welcome improvement to the processing line. With the use of the AquaChemical and Suparator systems, the processor has significantly improved productivity, cut operating costs, reduced waste, and improved product quality from the washing operations conducted on scrap titanium turnings.
Titanium Scrap Metal Processing