Processing Magazine

How Argueso achieved consistent 99 percent efficiency standard for particulate emissions

August 7, 2006

M. Argüeso & Co. produces casting wax blends for the investment casting industry, wax products to stabilize parts during machining, and specialty wax blends for cosmetic, sculpture, jewelry and other uses. The company emphasizes “green” technology, and low environmental impact. One of its most important new developments (patented in the United States and patent pending in the United Kingdom and Europe) is Hydro-Fill™, a product which improves surface, decreases flow lines and eases pattern removal. Its decomposition product is water.

M. Argueso moved from Mamaroneck, New York to Muskegon, Michigan in 2005, after the company was purchased by the Specialty Materials and Alloys group of Precision Castparts Corporation. The move brought it geographically closer to its customers, but subjected the facility to Michigan’s stringent air regulations. The company’s first priority was to identify a system that would collect fugitive wax particulate with consistently high efficiency. Low utility cost and minimal maintenance were also important to the selection process.

Wet particulate collection was specified at the outset because the wax vapor carried with the airstream would quickly blind baghouse, cyclonic and other dry systems. After evaluating several wet systems, the nod went to a technology developed by Tri-Mer Corp. called Whirl/Wet. The Whirl Wet dust collector is a submerged split orifice type dust collector. It is one of 8 major air pollution control technologies developed by Owosso, Michigan-based Tri-Mer. For submicron particulate, Tri-Mer manufactures the CCS Cloud Chamber scrubber; Whirl Wets are used for collecting particulate (soluble or insoluble) 5 microns and larger. Other systems are for acid / fume scrubbing, odor control, SO2 / NOx emissions, and oil mists.

Argueso purchased two Whirl Wet systems, 5,000 and 7,500 cfm, respectively, one for each of two operations. A rental unit allowed the company to test the effectiveness and operation of the technology before making a final commitment. In the main operation, super sacks, suspended from forklifts dispense fillers and resins in powdered form into hatch-lid kettles. As these materials are added, the Whirl Wet pulls outside air through the hatch, preventing release of particulate. Base waxes are generally added as slabs, or pumped in as liquids. Components are mixed into molten base waxes.

Wax vapors from the steam-jacketed, insulated mixing kettles, approximately 200 degree F, duct to the larger Whirl Wet unit. Particle size distribution of the incoming airstream is primarily between 5 and 10 microns, although 20 percent is under 5 microns. Particulate loading is heavy, because sticky vapors are entrained in the airstream. Whirl/ Wet employs a unique process to create intensive mixing of particulate and water. To infuse dust particles with water droplets, the mixture is passed under high velocity through a fixed-position, dual opposed blade system. The mixing of the dust-laden airstream and liquid occurs and, to increase turbulence, a tangential airstream is injected through a linear slot in the lower blade assembly. Rotation is accelerated, droplets in the airstream are eliminated through a mist eliminator located downstream, and particulate is deposited on the bottom of the unit for recovery or disposal.

Notably, the Whirl Wet has no internal moving parts, and is self-cleaning, so the sticky character of the material does not present maintenance issues for the collector, or the ductwork. Finished waxes are cast into slabs, billets, flakes and pastilles. Pastilles (or “drops”) are sprayed, chilled and formed with a perforated roller, flakes are formed on rollers, and slabs and billets are cast in molds.

The other operation is reclaim. Solidified wax, returned to Argueso for reprocessing, contains high levels of entrapped water as a result of autoclaving done by the customer. The wax must be melted, the water boiled away, the chemistry adjusted, and old filler material removed. The Whirl/ Wet also facilitates this process: under negative pressure, (standard design is 20" of negative pressure) its fan pulls out the moisture-laden air, saving process time and steps. The Whirl Wet removes a substantial amount of wax from the airstream as well as the wax that comes out of suspension.

To control process odors and VOCs, a 3,000-pound active carbon bed filter was placed after the 5,000 cfm Whirl /Wets units. Sandwiched between them is a bank of DOP-type “furnace filters” that first remove the smaller (1-3 micron) particulate. This assures that the costly fluidized bed carbon filter doesn’t blind. Blinding would occur as a result of wax vapors suspended in the warm exhaust stream. The filters allow the air to cool and the wax to solidify on the media. Without the filter bank, the carbon filters have a service life of 4-5 days. With it, it’s 3 months. To compensate for the higher pressures and fan velocity, silencers were provided on both Whirl Wet units to attenuate noise to a level of 70-75 dB for the larger unit and 80-81 dB for the smaller unit.

The two Whirl Wets installed at M. Argueso are virgin-grade, UV-resistant polypropylene homopolymer, a homogeneous material with a proven service life in corrosive dust applications of 20+ years. It is also highly resistant to chemical and mechanical abrasion, and a major contributor toward simplified maintenance. Wax-laden droplets eventually accumulate on the de-misters, but their PVD construction makes removal an easy task. Energy generated inside the unit will not allow the system to clog under any operating conditions, including high particulate loading.

Utility costs are minimized due to a low power draw – despite the greater fan requirements – and the fact that water use is low. Water level is maintained automatically, and make-up water is only necessary to compensate for evaporation or sludge removal.