Case Study: BOILER-TO-GAS INFRARED CONVERSION RESULTS IN LESS THAN ONE-YEAR PAYBACK FOR COLORADO STEEL PLANT
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PUEBLO, Colorado - When CF&I Steel Corporation looked into replacing its 30 year-old steam heating system in three auxiliary operations within its Pueblo, Colorado steel plant, a quality circle group from the boiler shop area consisting of management and bargaining unit employees had the task of determining the feasibility of either repairing or upgrading the old system, installing a new system, or installing an alternate energy system.
CF&I Steel Corporation's Pueblo Plant produces over 500,000 tons a year of rails, seamless tubes, rod bar and wire products for shipment throughout the United States. It has two 150-ton electric furnaces and two continuous casters. There are also rail, bar, rod, wire, seamless tube and other mills, a casting foundry and various auxiliary operations.
In its energy evaluation, CF&I's quality committee analyzed steam heating systems for the 25,000 sq. ft internal machine shop, a 5,035 sq. ft pipe shop and a 10,750-sq.-ft weld shop. The three buildings were erected in 1910 and consisted of uninsulated metal and brick and flat metal deck roofs.
According to Walt Walker, Combustion Engineer at CF&I in Pueblo, it was found that the cost of replacing old pipes going into these three buildings from huge boilers located within the CF&I plant complex would be tremendous.
"The boilers and pipes were found to be terribly inefficient and resulted in a heat loss of 4,000,000 Btu's in the machine shop alone," Walker noted. "It wasn't a closed loop central heating system and consisted of steam being piped into insulated radiators and fans located above the floor in the three facilities. Heating was also uneven and did not provide an adequate employee comfort level. The employees in three buildings were always cold since inside temperatures averaged only 40°F during the Fall and Winter heating season. Most of the employees had to wear layers of clothes and warm insulated jackets just to keep warm. Complaints were frequent."
After eliminating the boiler option, the quality circle looked at various natural gas systems including forced air heat, unit heaters and radiant infrared heaters.
After evaluating the various presentations, the quality circle members and Walker installed 35 RSTP17 gas-fired infrared tube heaters from the Space-Ray Division of Gas-Fired Products, Inc., Charlotte, NC, in three shop units. Each unit has a capacity of 175,000 Btu's. In addition, Walker also decided to purchase six Space-Ray RSPA5C radiant broad area heaters for the pipe shop, each with 50,000 Btu output.
According to Walker, during the first heating season, CF&I saved over $100,000, with estimated savings for the next heating season expected to be $130,000. He said payback for the system was in less than a year. "Btu savings are tremendous and heating efficiency optimum, considering the age of the three buildings," he said.
Of the 175,000 Btu Space-Ray RSTP17, gas-fired infrared tube heaters, 25 were installed in the machine shop, eight in the weld shop and two in the pipe shop. Total heat losses for different buildings were 4.85 million Btu/hr for the machine shop, 1.75 million Btu/hr for the weld shop and 650,000 Btu/hr for the pipe shop.
The machine shop consists of an uninsulated "A-Frame" type metal and brick building with a 30-foot-high center section and two parallel 18 foot high bays on either side. The building is 100 feet wide by 250 feet long. The top part of the center section and lower part of the two bays consist of numerous glass windows. Two large sliding metal doors on tracks are also located on both ends of the building for product and equipment transportation.
Most of the employees in the building work around stationary equipment such as lathes, allowing heaters to be adjusted toward the work station for optimum heating efficiency and employee comfort and welfare. Walker added that since installation of the heaters, employee complaints have been greatly reduced.
"Our heating season is from October to April with average temperatures during the winter months of about 30°F for this time period," Walker noted. "Temperatures get down to 10° below zero at times. Instead of wearing layers of clothes, employees now work in more comfortable clothing. With uniform, consistent heat, they are definitely a lot more comfortable and I feel that the heaters have also increased their morale and productivity," said Walker.
"With the temperature differential caused by the old steam heating system, the building actually sweated and caused rusting of the structure," he said. "We avoided this by venting the units."
Unlike the machine shop, the weld shop is 215 feet long by 50 feet wide and the pipe shop 47.5 feet wide and 106 long. Ceiling height in the weld shop is 30 feet and 17 feet in the pipe shop. Both buildings have glass windows on both sides.
CF&I Extremely Pleased With Heaters
Walker said that the even heat distribution of the tube heaters is a key factor in influencing CF&I's decision to install additional Space-Ray heaters in the future at other locations within the Pueblo plant complex.
Walker added that with the Space-Ray units, maintenance at CF&I has also been significantly reduced.