Filtration: Hydrocarbon Removal

Effective and Economical Hydrocarbon Removal with Enhanced Polymeric Absorbent
Cartridges for Higher Productivity and EPA Compliance

Shashi Parulekar
Martha Avery
Parker Hannifin Corporation
Filtration Group
Cleveland, OH

Abstract
Plant engineers are faced with the problem of effectively removing hydrocarbon contamination from their manufacturing processes. A cartridge developed by Parker Hannifin utilizing a proprietary polymer will help improve the efficiencies of manufacturing as well as environmental regulation compliance. This has been proven to remove 95% trace hydrocarbon contaminant in a single pass under recommended operating conditions. Parker TruBind™ cartridge performs an interaction on a molecular level to remove oil from a fluid. The polymer uses absorptive mechanisms to permanently contain the hydrocarbon. The breakthrough cartridge utilizes a modified polymeric absorbent that economically and effectively reduces trace hydrocarbon contamination in aqueous fluids.

Introduction
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.

Technology
Unlike other separation technologies, Parker Hannifin’s Fulflo« TruBind™ cartridges utilize a proprietary modified polymer that both absorbs and binds hydrocarbon molecules, such as tramp oil, into its interior matrices. The bound hydrocarbons are so forcefully held within the TruBind™ cartridge, it passes the TCLP (Toxic Characteristics Leachate Procedure). The TCLP simulates 20 years of exposure to the environment in a landfill. The oil absorptive cartridges are radial flow, meaning the liquid to be treated flows radially through the outer cage of the cartridge through a foundation of proprietary polymer. The treated fluid escapes through the center core.

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.

Performance
It is important to note that the TruBind™ cartridge performs best at low flow rates, pressure drops, alkalinities, and detergencies. Lab results showed lowered single pass efficiencies when these variables are increased. Many applications, such as tramp oil in machine tool coolant, do not require high efficiencies (90% +) at first pass since they are used in a recirculating type system.

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
Below is short summary of other separation technologies commonly used for hydrocarbon removal.

Activated Carbon Adsorption is the physical process in which dissolved organic components are removed from solution by either adhering to the porous carbon particle’s 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:

     < Microfiltration (filtering down to around 0.05 Ám)
     < Ultrafiltration (to around 0.005 Ám or 50 Angstroms)
     < Nanofiltration (to around 0.0008 Ám or 8 Angstoms)
     < Reverse Osmosis (to around 0.0001 Ám or 1 Angstroms)

Although these membranes have shown much potential for removing significant quantities of dissolved components from water as well as suspended particles at high efficiencies, they readily suffer from irreversible fouling due to dispersed oil. Consequently, TruBind™ oil absorptive cartridges should be considered as pretreatment solutions for many membrane applications. Extensive development efforts are underway to produce suitable membrane systems to remove oil from water. However, a common problem with such membrane filtration units has been the amount of time required to keep these systems operating with correspondingly high cost of operation.

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

Parts Cleaning
Oil absorptive cartridges used in cleaning operations will extend the working life of the bath, greatly reducing costly down time. Using Parker’s Trubind™ cartridge in the wash cycle can also prevent oil carry over to the rinse tank. TruBind™ used on parts washers will: 1) Provide consistently cleaner parts, 2) Increase washing solvent life, 3) Reduce maintenance costs, 4) Lessen downtime, 5) Save money in disposal costs.

Compressor Condensate
Oil absorption cartridges used to trap the sheen found in compressor condensate, is one of the most effective and economical means of treating the water. After being treated with oil absorptive cartridges, PPM (parts per million) levels in water are within the necessary levels to release to the drain.

Plating Bath
Oil absorption cartridges used in plating baths will extend the plating bath life. The benefits of using the cartridges in this application are identical to those in parts cleaning applications.

Waste Water
TruBind™ absorption cartridges along with filtration can be used to treat plant mop water. Utilizing this technology will greatly reduce disposal costs, allow reuse of wash water, and improve the cleaning properties of the water.

Machine Tool Coolants
As stated earlier, controlling tramp oil in machine tool coolant will extend coolant life. A very cost-effective way to manage this is by utilizing a filtration and separation recirculating system. It is very important to note that TruBind™ absorption cartridges can only be used with water based coolant. If an oil based machine tool coolant is being used, the proprietary polymer will strip the coolant and change its chemical properties.

For optimum coolant life, the following steps should be taken:
1) Start with fresh, clean coolant.
2) Install a skimmer at each machine tool sump to remove free floating tramp oil.
3) Place a filtration bag or cartridge unit at each sump, or at the central coolant tank that feeds to each machine.
4) Follow the filtration system with a cartridge vessel containing TruBind™ absorption cartridges to assist in the removal of mechanical emulsified oils.
5) Maintain system routinely, and change out media as indicated by the differential pressure indicators.
6) Implement a program to monitor coolant cleanliness on a regular basis.

Conclusion
There are many increasing challenges faced by those involved in the metalworking industry. The technology of the proprietary polymer absorbent in a simplistic cartridge design provides additional arsenal to combat these challenges. Parker Hannifin’s innovative TruBind™ cartridges are the economical and effective solution to removal of trace hydrocarbon contamination in aqueous fluids used in the metalworking industry.

References
1. Proile, Morbert T "Modern University Chemistry" Harcourt Brace Jovanovich Publishers 1997
2. Filtration Technology Handbook, Parker Hannifin Corporation, Revised Edition, 1997
3. TruBind™ Training Module, Parker Hannifin Corporation, Version 2, 1999
4. Bradley, D "The Hydrocyclone" Elmsford, NY, Paragon Press
5. Fahlstorme P.H. "Studies of Hydrocarbon as Classifier" International Mineral Processing Congress 6, 87-114
6. Stone, Kenneth R "Machine Coolants, Electroplating Operations, and Chemical Material Management at Norfolk Naval Base", Science Applications International Corporation, Cincinnati, OH
7. "Factsheet: Waste Minimization Options for Machine Coolants", Board of Public Works, HTM Office, Los Angeles, CA
8. Dr. Fritzsche, A. Keith, "Oil Absorption Cartridges", Filtration News, Mar/Apr 1999

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