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Several years ago, a brick manufacturer had a problem with heavy, wet clay. The company needed a material that would open up its brick body and reduce its significant bat losses, but it could not find a suitable product among the typical brick grogs and additives anywhere near the plant. In its efforts to find a solution, the company contacted Oil-Dri Corp. of America, a Chicago, Ill.-based firm that supplies absorbent clay minerals. While Oil-Dri's products had been used in a range of industries, from pet litter and food processing to agricultural to automotive, brick was a completely new field. Could the firm provide a material that would improve the porosity of a brick body at a cost that would be feasible for most brick producers?
After more than three years of testing and numerous plant trials, the company found its answer-and more. Today, the new additive* is helping brick manufacturers produce lighter, stronger brick, with increased throughput and associated reductions in fuel consumption, transportation costs and bat losses.
A Network of MicroporesThe key to the additive's performance is in its porosity and composition. The additive is composed of a network of small (<1 micron), interconnected micropores that maintain their integrity at temperatures up to 2200§F and reduce the weight of the finished brick. According to Tom Rutherford, vice president and general manager of Oil-Dri products, numerous plant trials have shown that a weight savings of between 4.0 and 9.1% can be achieved with a 5.5% inclusion of the product by weight (see Table 1).
"The additive weighs just 35 pounds per cubic foot [lbs/ft3] and is typically two to three times lighter than the additives it replaces, such as grog, fly ash and granite, which often weigh somewhere between 85 to 112 lbs/ft3," Rutherford explains. The additive can also be used to replace some base body materials, particularly heavy clays.
While many factors-including material cost, its role in the mix, etc.-affect which ingredient the additive should replace, weight is usually the key driver. "So many benefits are derived from weight savings that it usually pays to substitute the additive for heavier materials," Rutherford says.
The weight reduction also reduces transportation costs. With a 4-9% weight savings per brick, plants can often get another thousand brick equivalent (MBE) per load on a truck and still stay within weight restrictions. This, in turn, can enable them to cost-effectively expand their sales territories to other regional markets.
Lighter brick might also permit brick manufacturers to increase their throughput while remaining under the 10-ton emission limit required under state and federal Maximum Achievable Control Technology (MACT) standards. "Since less material (by weight) is going through the kiln, plants that are already under the limit might be able to produce more brick while remaining under that limit," Rutherford explains.
Making Better Brick, FasterIn addition to weight savings, the new additive also provides several other important advantages. For example, its absorbent nature enables manufacturers with heavy, wet clay to extrude a stiffer column.
"Just about every manufacturer has experienced some bat loss on the bottom of their kiln cars due to inadequate green strength. These losses can be quite high because of the enormous weight of the load," says Rutherford. "The additive acts as a moisture manager in wet clays, firming up the extruded column and improving green strength. Plant tests have shown increases in green strength between 10-21%. As a result, reductions in bat losses range from 2-5%-particularly in the lower portions of the car-both because of the increased green strength, and because the load is composed of lighter brick."
Additionally, unlike many byproduct additives, the new additive is consistent from load to load. As a result, "brick manufacturers won't have to compensate for material variability," Rutherford notes.
New OpportunitiesNumerous trials at brick plants have proven the benefits of the new additive, and in the fall of 2004, the product began seeing commercial acceptance. Like any new product, the additive isn't cost-effective in every situation. According to Rutherford, the product is ideally suited for plants with heavy plastic raw materials; throughput or carbon burnout issues; excess water in their base clays; dense, heavy grog additives (>100 lbs/ft3); service to a wide geographical area; and natural gas-fired kilns. But even these aren't necessarily a given.
"Each situation really needs to be evaluated on a case-by-case basis," Rutherford explains. "For example, this isn't a magic bullet to reduce energy consumption. Plants that are already using a lightweight body material and are firing with fuels other than natural gas probably won't see enough energy savings to justify the additional cost of using the additive."
Likewise, plants that are primarily looking for higher throughput might find other solutions that meet their needs. Oil-Dri Corp. has partnered with Mission Clay Products in Kansas City, Mo., to carefully evaluate each potential application and determine the suitability of the product based on a plant's individual goals. However, for many plants, Rutherford believes the combination of weight reduction, reduced bat losses and increased throughput provided by the new additive will be more than enough to justiify using it in production.
"A number of today's plants are using heavy raw materials and are looking for ways to save on fuel and transportation costs. With this new additive, companies can realize substantial savings in these areas while also improving their overall brick quality," he says.
For more information about the new additive, contact Oil-Dri Corp. of America, 410 N. Michigan Ave., Ste. 400, Chicago, IL 60611; (800) 851-2399; e-mail email@example.com ; or visit http://www.oil-dri.com .
*BA-1000, patented and supplied by Oil-Dri Corp., Chicago, IL.