Document GzD6XM3Z0VBjaXrNB7zp8YVqV

Reprinted from .VIRONMENTAL Science & Technology Vol .4, February 1970, 107-108 Copyright 1970 by the . ...lerican Chemical Society and reprinted by permission of the copyright owner Plant licks solvent emission problem Control system completely eliminates smoke and odor from oven exhaust gases Last October, a lady called gaf Corp.'s tates in a bath of fluid containing vinyl a catalytic oxidation system which was vinyl floor covering plant (Fullerton, monomers dissolved in mineral oil intended to convert the gases to carbon Pa.) to ask when the plant had shut solvent (its exact composition is a dioxide and water. Unfortunately, the down. She wasn't calling to sympa proprietary secret). The wet sheeting is oxidation unit could not be operated thize; she was--frankly--glad that one transported through a long oven in so as to provide complete conversion. of the Lehigh Valley's air pollution which the solvent is driven off and the The result was that the air pollution problems seemed to have been licked, monomers polymerize to yield the nuisance became greater than ever: even if it apparently meant the loss of clear, wear-resistant coating. The ex The smell coming from the plant now a local employer. The lady caller was haust gases from the ovens were the was reminiscent of burnt 3-in-one oil. astounded to be told that the plant, far from being closed, was, in fact, run ning at full production. The reason for astonishment was simple: For 10 years source of air pollution from the plant. Development of problems The plant initially was owned by the Effective system After a search in which over a dozen firms were contacted, gaf eventually the gaf plant had emitted a white Sandura Co. Sandura was bought by contracted with Clermont Engineering smoke that smelled, according to Le the Ruberoid Co. in 1965, and, in Co. (Philadelphia, Pa.) for supply of a high Valley Air Pollution District di 1967, Ruberoid was merged with gaf control system that wduld eliminate the rector R. Emmet Doherty, like 3-in- Corp. air pollution problem. one oil, and which frequently In 1948, Sandura Co. started up the Clermont's approach was to engi blanketed the area with a haze that severely reduced visibility. Citizen Whitehall plant with one, nine foot wide coating line. Then, in 1957, a neer a system that would recover as much as possible of the mineral oil complaints that the plant quite literally made them sick had not gone un second, 12 foot wide line was added in a major expansion move. The added solvent, so that it could be reused as the carrier for the vinyl monomers at heeded by gaf, but a solution to the problem was not found until 1969, production capacity of the plant, and the need to work more than one shift, the coating stage in the plant. Conse quently, combustion processes were when a new air pollution control systern was installed. Fortunately for all concerned, this system has proven a complete success. Air pollution source brought the pollution problem to the notice of the public and under the eye of the Lehigh Valley Air Pollution Dis trict. Initially, there were no controls whatsoever on emissions from the not considered. In the Clermont design at the White hall plant, exhaust gases from the ovens first are sent to a scrubber-con denser unit in which many of the less volatile components in the gases con The Whitehall plant of gaf Corp. at Fullerton produces vinyl coated floor ovens. In an attempt to control the problem, plant management installed dense out on the surface of water coils. Some of the condensate recovered ing products for a rapidly expanding market that includes offices and mobile homes as well as private homes. The process involves preparing a continu ous blank backing sheet with a coating of vinyl polymer, then printing the surface with an attractive pattern and, finally, coating the sheet with a thin, wear-resistant layer of vinyl polymer. The heart of the process, and the rea son for the product's popularity is the vinyl layer over the patterned surface. This coating may only be ten thou sandths of an inch in thickness (per haps twenty thousandths in the most expensive products) and is completely ; transparent, but it is entirely respon- J sible for the long-wearing qualities of I the flooring material. { " The coating is applied to the con- | tinuous sheet by a cylinder which ro STLCOPCB4093608 Control of coating solvent emissions is two-stage process from the scrubber-condenser is re cycled to spray heads; the spray is used to prevent condensate from coating the coils and thus causing reduced heat transfer rates. The rest of the con densate is piped to tanks where the oil and water fractions are separated. The gases leaving the scrubber con tain a fine oil droplet mist; most of the drops are less than one micron in sjze. Final removal of the mist is accom plished in a pair of towers containing Brink mist eliminator elements (Mon santo Enviro-Chem Systems, Inc., Chi cago, HI.). These fiber filters are widely used to trap particles less than three microns in size at high collection efficiencies. The liquid draining from the mist eliminators, together with condensate from the scrubber, is pumped over to a pair of settling tanks where the heavier water fraction separates out from the lighter oil fraction. The water is drained away periodically, and the oil is available for reuse. In practice, oaf has sent this oil back to its supplier of coating liquid for reprocessing be fore it is reused. Efficiencies Clermont claims that 80% of the contaminants in the oven exhaust gases are removed in the scrubber-condenser. At the stack outlets above the mist eliminators, 90-95% of the volatilized organics have been removed (and re covered), according to Clermont. (The Brink mist eliminator elements are claimed to remove 99+% of the mists and other condensate reaching them. The residual low boiling organ ics escape as vapors.) gaf agrees with these figures, but quotes no precise poundages, for competitive reasons. The 90-95% removal figures are not arrived at by measurement, but by subjective evaluation of the state of the exhaust plume rising from the stack. The plume is remarkably light, even on a cold, dry day when the pres ence of water in the gases always tends to produce a white plume. gaf claims that maintenance of the control system is both easy and inex pensive; there are few moving parts to service. The fans which draw the gases through the scrubber and force them through the mist eliminators do, of course, require servicing. Their opera tion is the prime operating expense: Together, the two blowers move 33, 000 c.f.m. of gases while requiring 175 h.p. Economics The goal--at least ideally--of every pollution control system is to pay for itself. Systems in which a raw material or byproduct is recovered for reuse obviously have a much better chance of meeting this goal than those in which wastes are burned or otherwise , converted to valueless products. In the case of the gaf vinyl sheeting plant, there seems to be some reason for opti mism. Although Don Dorfman, presi dent of Clermont Engineering, insists to J. Paul Lasley, manager of the Whitehall plant, that the system even tually will save more than it cost ($363,000), Lasley understandably is reluctant to make unequivocal state ments on the subject. After all, the plant manager says, the control system has been in operation only a few months (since October 1969), and it is too early yet to say anything with as surance. Nevertheless, Lasley is cer tainly delighted that a problem which has plagued him for years appears to have gone forever. Even though effort was continually expended, it took 10 years to arrive at a satisfactory solution to the White hall plant air pollution problem. The fact that so much time was needed brings up an important point that sel dom is appreciated fully: Eliminating air pollution is rarely just a simple matter of purchasing a piece of control equipment off the shelf and installing it on line. Especially interesting in this con nection is the Pennsylvania plant's poor experience with its catalytic oxi dation system. Such systems have regu larly been employed with success to solve difficult air pollution problems (see, for example, the description of catalytic oxidation of monomer emis sions at a wax plant in es&t, Novem ber 1969, page 1159). Yet, recurrent problems with incomplete conversion forced abandonment of catalytic oxi dation at the Whitehall plant. One is compelled to recognize that even pollution problems "which are similar in nature may not be amen able to solution in the same ways. This is a sobering thought, for it means that experience in controlling one type of air pollution may be practically worth less in controlling another. Little won der, then, that air pollution control can not be achieved overnight, even by firms such as gaf that have shown themselves to be in earnest in tackling their emissions \ 108 Environmental Science & Technology DSW 588273 STLCOPCB4093609