Ceramic Industry

BCR: Is It Time to Retrofit Your Kiln?

August 1, 2002
By proceeding cautiously and making sure you have the right information, you can ensure that any changes you make to your kiln have a positive effect on your productivity and your bottom line.

Kiln and dryer retrofits at Henry Brick Co. in Selma, Ala., resulted in a 25% capacity increase and noticeable product quality improvements. Harrop engineers lengthened the existing Swindell Dressler dryer, created additional recirculation zones and redistributed the heat supply. Harrop also lengthened the Swindell Dressler kiln and fitted it with a new preheat combustion system and larger, redesigned cooling air systems.
We often hear success stories about companies that have upgraded their existing kiln or built a new kiln and reaped tremendous benefits. It can be tempting to want to “keep up with the Joneses.” But every plant is different, and a solution that worked for one company might not work for another. How do you know when it’s time to upgrade or replace your kiln, and how can you determine what technology is right for your plant?

Carefully evaluate your current situation, determine your goals, understand your budget and know your options. By proceeding cautiously and making sure you have the right information, you can ensure that the changes you make to your kiln have a positive effect on your productivity and your bottom line.

Figure 1. A comprehensive energy audit can tell you how much energy is being consumed and where it is being consumed. The audit results, like those shown in the above Sankey Diagram, developed by Harrop Industries, Inc., reveal where improvements can be made to reduce energy consumption.

Evaluate Your Situation

Before you make any changes to your kiln, make sure you have a good understanding of your current situation with regard to operating costs, production quality and quantity, safety and environmental issues, process control, data acquisition and production technology.

Excessive Operating Costs. Excess fuel consumption is a common problem in the ceramic industry. Causes can include excessive heat loss or cold air leakage, too much dead load in the kiln furniture or kiln insulation, insufficient kiln insulation, inefficient use of heat input to the process, insufficient control of gas use and/or temperature, obsolete hardware, a cycle time that is too long and/or an incorrect setting density. Give your process an energy audit to find out how much energy is being consumed, where it is being consumed and where improvements can be made to reduce energy consumption (see Figure 1). Working closely with a consultant or kiln builder can help you ensure that the audit is thorough and complete.

Another important factor in evaluating your current situation is the cost of labor. In some cases, automation might be needed to reduce the risk of worker injury in loading and/or unloading operations. In other cases, the plant layout may need to be changed to ensure the most efficient use of the space or of workers’ time.

Find out how your plant’s operating costs compare with other plants in the industry, but make sure you’re comparing similar situations. Know the source of any data you obtain, and make sure the data is accurate.

Poor Production Quality. If you are experiencing excessive quality spreads or low yields of premium-quality products, it may be time to reevaluate your firing operation. However, be certain that you know the source of the problem before you invest in a solution. Problems that emerge after firing can sometimes be caused in the drying or forming process or by the body formulation. Map your current product quality, including characteristics such as shrinkage, absorption, strength, color and any other important criteria, so that you can determine whether changes in the firing process can improve these characteristics.

Insufficient Production Quantity. If your kiln requires excessive cycle time to produce the amount of product you need, it could be kiln-related; however, it might also be product-related. For example, a 20% slower cycle time might be required to fire 10% of your total product line. Rather than investing in an upgrade or new equipment, you might be able to gain greater efficiencies by simply making that product in a different location or by not making it at all. Other causes of reduced production can include limited production scheduling or a bottleneck elsewhere in the manufacturing process, such as grinding. Make sure you know the source of the problem before investing in a solution.

Safety Issues. Evaluate the mechanical, electrical and operational safety of your current equipment. Make sure that the appropriate guards are in place, that the mechanical interlocks are functional, that sufficient platforms provide access to maintain the equipment, and that barriers separate personnel from mechanical activity.

Find out whether the equipment follows the appropriate electrical and combustion safety codes. Older equipment should follow the codes that were in place when the equipment was installed, while newer equipment should follow more recent codes. If you’re considering an upgrade, be aware that making major changes to an older system might require the equipment to be modified to meet the current codes.

Determine whether the equipment is operating above defined electrical limits, and make sure accurate electrical schematics are available to permit maintenance efforts. You should also examine the existing combustion safety systems—including flame safety systems, temperature limiters, pressure and flow interlocks, solenoid valves, vents, leak detection systems and alarms—to make sure they are operational.

Make sure that your kiln operators are working in safe conditions, that they have safe access to all kiln controls and functions, and that they are properly trained in safe operating techniques. Determine whether automation might be required in loading, unloading or other kiln-related operations to reduce labor safety concerns.

If your evaluation reveals that the equipment has reached the end of a reasonable “safe” operating life, changes will most likely be needed to ensure the continued safety of your employees.

Environmental Issues. Federal and state environmental agencies will probably tighten permissible effluent levels in the future. Determine whether your existing kiln can or should be adapted to meet more stringent emissions regulations. If your equipment has been “grandfathered” to operate under the current regulations, be aware that upgrading the system to improve its performance may require you to add new pollution abatement equipment.

Asbestos is another common environmental problem. Find out whether you have asbestos in your kiln, and understand your options. If you know your kiln contains asbestos but you can’t afford to remove it, an upgrade isn’t feasible, since disturbing the asbestos can create serious health risks. Instead, you’ll need to either continue operating your kiln in its current condition or build a new kiln in another location. If you decide to leave the asbestos in place, make sure you implement the necessary procedures to prevent human exposure to it. If you decide to have the asbestos removed so you can retrofit or replace your kiln, you’ll need to hire specialists to ensure safe removal.

Obsolete Process Control/Data Acquisition/Production Technology. If you have an insufficient amount of control over your process, insufficient data about your process or obsolete production technology, you might want to consider upgrading your kiln to correct the situation. However, the problem might also be due to incorrectly or inefficiently using existing data and technology. Make sure your employees know how to use the existing equipment to its maximum potential. If you decide to purchase new equipment, make sure your employees receive proper training so your investment is not wasted.

Kiln and dryer retrofits at Jenkins Brick Co. in Montgomery, Ala., increased plant capacity by 50% and reduced per-unit fuel consumption by 28%. Harrop engineers lengthened the existing Harrop dryer, installed a larger exhaust fan system and additional recirculating air zones, redistributed the heat supply and created a new heat recovery system from the kiln. The Harrop tunnel kiln received a new exhaust system, additional preheat recirculation, new combustion controls and larger cooling air systems with automatic controls.

Know Your Goals, Budget and Options

Once you have evaluated your firing process, determine whether certain areas should be improved, and find out how much money is available to perform the required modifications or to purchase new equipment. Finally, make sure you know what options are available to help you meet your goals by evaluating other plants and by talking to knowledgeable industry professionals.

Retrofitting or replacing your kiln might save you money, make you more competitive and provide you with greater peace of mind. It can help you reduce fuel usage and product losses, improve product quality and maintain better control of your firing process. However, make sure you have all of the data in hand—and that the data is accurate—before you make any changes to your firing process.

No one else can make the decision for you. Whether you retrofit or replace your kiln, or any other piece of equipment in your plant, depends entirely on the cost versus the benefit to your facility.

For More Information

For more information about kiln retrofits and rebuilds, contact Harrop Industries Inc., 3470 E. Fifth Ave., Columbus, OH 43219; (614) 231-3621; fax (614) 235-3699; e-mail sales@harropusa.com; or visit http://www.harropusa.com.