Designing new wood-burning products with Condar catalysts

Inventors, manufacturers, and new product developers inquire regularly to Condar Company about catalysts for wood heating stoves, inserts, fireplaces, wood-fired cooking stoves, indoor wood-fired boilers, and outdoor furnaces.

The following information is provided to assist application engineers and managers in understanding the basic facts. Please read carefully and be sure to understand this information to the best of your ability before consulting Condar about your needs.

Catalytic technology is not "retrofit" technology.

This technology can't be successfully added to an existing wood-burning product. A product must be purpose-designed for a catalyst to work properly. For example, simply putting a combustor in an exhaust pipe won't work. It will clog up with ash and be dangerously hot.

A catalyst is not a filter.

Catalytic combustion doesn't "capture" particulate emissions. It generates heat and water vapor (released as gas in exhaust). Therefore do not plan to use a catalyst as a simple filter.

Your catalytic design must have a "bypass."

When exhaust temperature isn't high enough for a catalyst to "light-off" the wood-smoke exhaust must have an alternate route to go, until the catalyst is hot enough to perform its function. The most difficult part of designing your new catalytic product, therefore, is designing the correct "bypass" route.

Operating temperatures must be hot enough.

The catalyst and air-particulate stream must be at least 200° Celsius or 400° Fahrenheit, minimum, to initiate the reaction chemistry. Open-chamber fireplaces, woodstoves and cookstoves that aren't air-tight, and outdoor wood furnaces don't operate at temperatures hot enough to achieve the chemical reaction.

If you are designing any of these product types, be aware that no successful catalytic designs of these exist anywhere in the world. It is generally understood that theoretically the catalyst could be artificially heated "outside the system" but this is expensive, and hasn't yet been simplified from industrial-scale technologies to small-scale utility.

Pre-heating your catalyst.

Your design should incorporate the catalyst in a position where the start-up fire will heat and keep the combustor hot enough to function.

Not over-heating your catalyst.

Your design must avoid a thermal "feedback loop" where the catalyst heats air and solids to the extent it destroys itself by overheating. The path of entry air and exit air is vital. Locating refractory materials adjacent to the catalyst aren't enough to guarantee safety and longevity of the catalyst. You must understand thermal design principles!

Take advantage of the extra heat the catalyst generates.

The best catalytic designs radiate the extra heat in a positive direction. If a heating stove, this is forward toward the room, not toward the floor or behind the unit. If designed for stove-top cooking, the design directs heat upward.

Air flow rate and pressure drop.

The nature of wood fuel presents unique challenges for catalytic design. Wood fires generate ash and wood-smoke particulates are large. Exhaust streams are not fan-driven, for safety reasons, and thus require much larger cells to maintain air flow than the exhausts of many catalytic applications such as an automobile catalyst.

Avoid flame impingement!

Design so that direct flame contact with the catalyst never occurs during the burn cycle. (A strong draft may even pull flame into the combustor.) Direct contact by fire flame will quickly and permanently damage catalytic material and the substrate.

Planning for examination and replacement.

You should locate the catalyst in a position that is easy for inspection and maintenance. Eventually the catalyst will outlive its useful economic life. Performance decline begins after about 12,000 hours of active burn time in practical use with wood fuel.

Don't use a conventional gasket around a catalyst.

It is improper (and potentially dangerous) to use a conventional Fiberglass gasket such as those typically used around woodstove doors. In fact, it isn't necessary to have an airtight seal at all for the catalyst to work properly. A simple drop-in design is satisfactory.

Ceramic or steel?

Ceramic catalyst continue to be the best choice for designers of new products. They are easily manufactured in low quantity, are essentially "modular" and no custom tooling is involved. Once a product design is proven and market volume is sufficient, it then makes sense to consider design of a steel-based version. A steel catalyst should never be chosen because the product design doesn't work with a Condar ceramic catalyst. If the ceramic is overheating, plugging, etc. you have a fundamental product design problem that a steel version simply won't overcome.

Are all ceramic and steel catalysts essentially the same?

No. There are important quality differences among suppliers of ceramic and steel catalysts for wood burning. Condar has decades of experience to know what works best in these applications. We carefully control our sources and specify best materials. Much of our materials expertise is proprietary information and cannot be revealed, even to our valued clients.

How does a client determine a new design will work?

Since the first catalytic woodstoves passed American emissions-control tests decades ago, catalytic designs have improved and changed. Be aware that the many different configurations have advantages and disadvantages. Some designs operate well in tests and certification, but are difficult to maintain. Others are easy to maintain, but are more costly or sacrifice efficiency. The inventor must study and learn from the existing products currently available in the market, which are virtually all experienced USA or Canada manufacturers. Condar does not, at this time, provide engineering and consulting services to designers and marketers of new products.

Condar does not guarantee the catalyst will pass your nation's emission tests.

Each nation has different expectations and standards for efficiency and emissions. From a practical standpoint, passing the test is more a matter of product design than the catalyst design. While Condar's products have passed the strict tests of USA and are used in products in Europe, Japan and around the world, you are responsible for your own laboratory and government testing.

Condar does not provide free samples for research & development purposes.

There are no discounts to engineers, inventors, and product developers, and we don't invoice on open-account. Please use the conventional shopping cart to order catalysts. Catalysts used for R&D purposes aren't covered by warranties.

Volume discounts to the trade.

Condar supplies manufacturers and distributors around the world from its factory in North Carolina. To obtain price quotations at discounted trade prices, kindly contact Karen to obtain a trade credit application.

Standard sizes and shapes.

Best cost-efficiencies today are rectangular shapes, not round shapes. We recommend you begin your application engineering using our Condar code number CC-251, a compact standard rectangle, 6.4 cm wide x 16.8 cm long x 5.1 cm thick. Nicely wrapped in a highest-quality stainless steel metal can. This size fits compactly inside modern stoves, with plenty of capacity to accommodate exhaust flow.

Measuring temperature of the catalyst.

During your research and development, use standard thermocouples to monitor temperatures. Any digital multi-meter can be fitted to the thermocouples. Begin to think about how your customers will monitor the catalyst for most-efficient performance of the woodstove. Some wood stove brands use simple thermometers on the stove surface, outside and near the catalyst. Others use probe thermometers, the probe ending as much as 1 cm away from the catalyst (they must not actually touch). Others require more-expensive digital catalytic monitoring (remotely, by cable). Condar manufactures all these monitoring products for wood stove manufacturers, in Celsius and Fahrenheit scales. Click here to learn more about catalytic thermometers.