With energy costs rising to record levels, no company can afford to ignore its inefficient systems. This is especially true for one ready-mix concrete company in upstate New York. Last year they spent nearly $100,000 on natural gas. While producing concrete is an inherently energy-intensive process, this company knew that by repairing and insulating their carbon steel rotary kiln, they would certainly lower the heat loss. The question was, by how much?
Besides lowering their energy costs, the company had a number of other maintenance problems. They called Maple Grove Enterprises because of the wide range of services we offer. Their bucket elevator system was no longer working, so we fabricated and installed a new belt conveyor to replace it. Our capability in metal fabrication enabled us to repair their deteriorated and corroded rotary kiln. And, of course, we also provide insulation coating services.
To fully understand the energy issues at hand and their possible solutions, we hired an energy auditor to report on the heat lost through the kiln per year and to estimate the energy and cost savings gained by insulating the kiln.
The auditor based his calculations on a wall area of 690 square feet and a chamber operating temperature of 600ºF. He determined that the heat loss per square foot is over 5,000 BTU/hr, for a total heat loss of over 3.5 million BTU/hr!
One of the restrictions for insulating the kiln was that there is only about 1″ clearance. Most high temperature insulation materials—mineral wool, ceramic fiber, etc.— must be applied in large thicknesses at least 3″ to achieve desired results. Fortunately, we discovered Aspen Aerogel’s Pyrogel© XT, an extremely effective high-temperature insulation whose required thickness is 50% to 80% of other insulation materials.
The energy auditor determined that by wrapping the kiln with just 10mm (or about 3/8″) of Pyrogel XT, the heat loss on the kiln would decrease from about 3.5 million BTU/hr to just over 27,000 BTU/hr.
To further insulate the kiln, the auditor calculated the heat loss if we then coated the Pyrogel with Envirotrol’s Ceramic Cover CC. He determined that the heat loss would be reduced another 5,000 BTU/hr by adding 40 mils of ceramic cover.
By insulating with both Pyrogel XT and Ceramic Cover CC, the surface temperature of the kiln was reduced from over 500ºF to about 200ºF—significantly increasing employee safety by reducing the risk for burns.
The upshot is that the company will realize enough savings in reduced energy bills to cover the expense in only one year. Now that’s a concrete return on investment!
