Back To Basics - Rto Media

Back to Basics A walk down the cereal aisle of your favorite grocery store will tell you we’ve gone way overboard on selection. What used to be a reasonable selection of good breakfast cereals has turned into one long aisle of endless selections with every package touting the best in nutrition, taste and value. The same has become true with the selection of Heat Recovery Media for the Regenerative Thermal Oxidizer (RTO). Over the years it has become increasingly difficult to wade through product names, all the rhetoric of product claims, catch phrases, monikers, etc. of available heat recovery media products today. It is a daunting task sorting through all the technical information and questionable claims being presented to sell these products. Over the years media manufacturers have produced this basic ceramic product in just about every conceivable configuration in order to claim the perfect RTO heat recovery media. Today it comes in shapes such as dog bones, snowflakes, rings, saddles, and fluted saddles, saddles with slots or holes and even structured extruded shapes. Each of these products claims to be the best overall engineered product for RTO’s. RTO’s came into full scale use during the early 1970s when energy costs skyrocketed due to the “Arab Oil Embargo” and more noticeably, the formation of the federal government’s EPA. Factories from that moment on were forced to use thermal oxidizers to abate fumes and odors from industrial exhausts as mandated by the 1970 Clean Air Act. The first RTO was sold in Pennsylvania and was manufactured by REECO (later known as Durr/REECO) to destroy fumes emanating from an Armstrong vinyl floor manufacturing plant. The Regenerative feature of the RTO utilizes two or more beds of ceramic stoneware acting as heat sinks as the multiple chambers switch the recovery beds from inlet to outlet using a number of “butterfly” or “poppet style” valves. The process exhaust gas enters a bed that is on an inlet cycle. This gas picks up the heat from the previous outlet cycle preheating the incoming air to with 95% of its combustion temperature. The first RTOs used die-pressed, Knight random packed Berl saddles, which, until that time, were typically used in distillation towers. The ceramic properties of the stoneware were well suited for the RTO application. The ceramic was thermally stable to 2100ºF, chemically stable and was not affected by small amounts of metals, chlorides or sulfides, Best of all, the thermal cycling of the RTO’s regenerative process had minimal effects on it. For ten years this was the standard for RTO heat recovery media. In 1980, for economic reasons, REECO switched to Koch/Norton Interlox® saddles which were extruded. This was the recognized staple in the industry for the next 7 years. In 1987, Huntington Energy Systems of Union, NJ entered into an exclusive agreement with Norton Industries to use their Super Saddles®. The Super Saddle® had a geometry that yielded 40% less pressure drop over regular saddles with an almost equivalent thermal efficiency. This was a significant power savings over conventional saddles. In addition, existing equipment could be retrofitted with this media enabling the system to handle 20% more volume without significant changes to the exhaust fan or motor. Because of the exclusive agreement between the two companies, other RTO suppliers were forced to seek alternative options for low pressure drop media. This option came in the form of extruded monolith blocks from Austria, typically used for catalytic oxidizers. This media

was nominally a 6”x6” block 6” tall with small square openings measured on a ‘cells per inch’ (cpi) basis. The blocks for RTO use ranged from 25 cpi to 40 cpi. Blocks were later expanded to 6” x 6” x 12” to minimize handling. The industries’ movement to monolith was not exactly a leap of faith as RTOs were already being produced in Europe using monolith. Over the years RTO manufacturers continued to source other media options to compete with existing products or in order to market the newest best media such as layered structured media. The growing sales of RTO’s over the next 20 years found equipment being installed in varied industries and applications, each with its own set of specific challenges. RTO media applications became more demanding and performance issues were constantly being uncovered such as plugging, alkali attack, thermal channeling, thermal degradation, etc. New formulations of ceramic clays needed to be developed to overcome more severe operating conditions. We now have low pressure drop, alkali resist, corrosion resist, glaze resist, thermal stress resist, high density, low density, high porosity, low porosity, etc. It has become just like the cereal aisle. How does a prospective buyer decide? End users have spent millions of dollars trying every new media that came along as each salesman proclaimed their product to be the best on the market. Over this course, many companies luckily have been able to wade through the rhetoric to find a product that solved the bulk of their specific challenges, trying to economically meet thermal efficiency demands as well as VOC destruction requirements. Many companies have decided in the end, that it is easier and less costly just to use standard saddles or low pressure random packed media and replace them every year or so rather than spend additional money on a product that was only marginally better and much more expensive. They just suck out the bad media with a Super Sucker vacuum truck, replace the media and landfill the remains and are done with it. This Back to Basics approach is what has driven Cell-Stone® (www.cell-stone.com) to promote the Ultra Saddle™ low pressure random packed RTO media as its core product. This low pressure drop saddle exhibits all the benefits of the original interlocking type saddles, but at one half the pressure drop. Gone are the thermal shock problems associated with structured media and other issues such as poor distribution, thermal stress cracking, excessive and quick plugging, etc. With many RTO’s already operating for nearly 30 years with random saddles, the flexibility, low pressure drop, high heat recovery, and exceptional value again are making this product the product of choice among RTO owners and manufacturers.