Effective and Economical Hydrocarbon Removal with Enhanced Polymeric Absorbent
Cartridges for Higher Productivity and EPA Compliance
Parker Hannifin Corporation
Plant Engineers in the Metalworking industries, along with a variety of other types of manufacturing, are faced with the challenges of reducing operating costs, increasing plant efficiencies, and complying with stringent environmental regulations. A primary area of concern in machining and grinding is the management of machine coolants. Coolants deteriorate over time by use and contamination. Tramp oils encourage anaerobic activity, which greatly attributes to bacteria growth. High levels of bacteria are a leading cause of fouling coolant. All coolants eventually break down over time and must be disposed. The ultimate goal of machine tool coolant management is to: 1) Extend coolant life as long as possible, 2) Reduce machine downtime and maintenance costs, 3) Increase machine tool life, 4) Take all precautions necessary to reduce the rate of bacteria growth.
One method of addressing these goals is through the use of filtration and separation technologies. Utilizing a filtration system is ideal for removing metal fines and other particulate in the coolant sump. Bag and cartridge style filters are a common, cost effective method of extending coolant and machine tool life. Along with filtration, separation technologies should be used to reduce the tramp oil accumulation in the sump. An oil skimmer should be used to capture the free floating tramp oil that is present. Additional separation measures must be take to insure optimum tramp oil removal.
As the hydrocarbon contaminant permeates the cartridge, swelling will occur. The differential pressure required maintaining the flow rate will progressively increase. This unique characteristic is a perfect indication of when it is time to replace cartridges. The oil absorptive cartridge is classified as non-hazardous and incinerable, however disposal must be dictated by local regulations pertaining to the absorbed contaminant.
The hydrocarbon density also affects the performance of the oil absorption cartridge. The lower the density of the oil, the higher the capacity of the cartridge. For example, the cartridge will hold more Kerosene than it will 10W30 Motor Oil.
Other Separation Technologies
Activated Carbon Adsorption is the physical process in which dissolved organic components are removed from solution by either adhering to the porous carbon particles surface or entrapment within its pores. Activated carbon has a very high surface area per unit mass (e.g. 400-1600 m▓/g) in order to maximize its adsorption capacity. Dispersed oil is a concern due to its propensity to block/foul the activated carbon beds. Therefore, opportunities may exist to use TruBind cartridges to treat incoming feed to protect the activated carbon system and extend its life.
Centrifugation is the process of using centrifugal force to separate substances of different densities. Centrifuges can handle high concentration of oil and grease at the inlet, and often treat down to 10-12mg/l. Removing 99% of 5....m size oil droplets and up to 98% of the 2 Ám size oil droplets. Most other treatment processes, such as coalescence, flotation, or the hydrocyclone can not match this level of performance. Many in the automotive industry often use centrifugation since the performance is assumed regardless of fluctuating flow rates and varying concentration of incoming flow. One negative aspect of centrifuges is that they are "rotating" equipment and by their very nature require routine maintenance. Moreover, they tend to be more expensive than gas flotation units and most hydrocyclones. TruBind cartridges will readily polish the aqueous product streams from those units.
Coalescence is the process of bringing together two or more dispersed particles to larger particles. The most common coalescers pass the phases through some type of solid bed, metal screen, fiber mesh, or membrane. The packing holds the hydraulic or lubrication oil mixed in coolant until large particles are formed and leave the packing surface. These systems are usually designed to remove the 100....m size and larger oil droplets. TruBind can be used following this device to insure conformance of regulatory requirements.
Hydrocyclone Separation is another process utilizing high centrifugal forces to separate substances of different densities. The mechanical design increases the velocity of the feed. This high velocity and corresponding centrifugal force increase as the feed spirals through conical section. Typically, hydrocyclones can remove 10-20 Ám oil droplets effectively. Furthermore, hydrocyclones contain no moving parts and can be mounted horizontally or vertically to provide greater flexibility in footprint design. However, hydrocyclones are neither practical nor will perform satisfactorily in certain applications, such as when the inlet pressure is insufficient, when unstable flow rates prevail, or when the water chemistry is unfavorable, e.g. severe emulsions.
Ion Exchange is a reversible chemical reaction in which a charged ion from a solution is exchanged for a similarly charged ion attached to an immobile resin bed. The adsorbed ions can be removed from a spent bed by contacting the resin with regenerant solutions. This results in a by-product stream, which contains a high concentration of the adsorbed ions. For the removal of heavy metal ions, a chelating cationic resin would typically be used in a packed bed or column. These resin beds are easily fouled and/or blocked by dispersed oils and solids. Consequently, upstream pretreatment using media filters are normally necessary to remove particulate solids and deoiling is also required. The TruBind oil absorptive cartridge would serve either to protect the ion exchange columns from low levels of oil contamination or as a final polishing treatment for technologies that efficiently treat much heavier oil loads, such as hydrocyclones, etc.
Membrane Filtration is widely used
for the treatment of aqueous solutions for a spectrum of applications. Membranes for water
treatment can be divided into four main classes:
Polymer Adsorption is a common technique used to clean oil spills as well as to effect oil/water separations. In this case, socks, pads and even bag filters are packed with fine denier fibers to provide a large surface area. The fibers are primarily polyolefins, such as polypropylene. The surface energy of these materials closely approximates the surface tension of the oil droplets to be removed from aqueous solution. As a result, the oil droplets adhere to the surfaces of the fibers reminiscent of grease to a Teflon« coated frying pan after the detergent is spent. Therefore, the oil is held to the polymer fibers by physical means and can subsequently be removed. In fact, one of the selling points of the oil adsorptive pads is that passing the pad through a wringer can reclaim the oil. Consequently, the trapped oil can be released as saturation is approached, and leaching of oil from discarded items is always a problem.
Typical Applications for the Metalworking Industry
Machine Tool Coolants
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