SPECIAL SECTION/REFRACTORIES: Case Study: A Batching Solution
Coal use is expected to grow substantially in the U.S. Indeed, coal demand east of the Mississippi River is projected by the U.S. Energy Information Administration (EIA) to increase by 5.9 quadrillion Btu, or 39%, between 2005 and 2030. West of the Mississippi, coal demand is projected to increase by 6.1 quadrillion Btu, or 79%, within that period. For suppliers to coal-generating power plants, such as refractory manufacturer Spar, Inc. of Jacksonville, Ala., these projections present both challenges and opportunities.
Spar manufactures proprietary dry refractory blends made primarily from natural ceramics for power generation, incineration, hydrogen processing and petroleum refining. The company develops and tests all of its own products and does extensive testing on raw materials to assure purity and correct particle size. Its capacity is 2000 tons per month.
Avoiding a BottleneckIn 2006, with demand rising, the company sensed a looming bottleneck in its production. In June of that year, the company brought in Jim McClellan, a former textile plant owner and Spar board member. McClellan, an industrial engineer, emerged from retirement to manage operations and head off what was forecast to become a serious obstacle to growth.
“The bottleneck was our batching operation,” explains McClellan. “Raw materials were received in 3500-lb bulk bags and stored until needed. When we were ready to batch, bags were unloaded into hoppers in our production area. Formulas, which typically have 5 to 16 dry ingredients, were batched one at a time, weighed by hand, homogenized, and put in bulk bags or paper sacks for shipment. The system was forklift-intensive, and if there was a mistake in weighing it was not detected until late in the process. It took a lot of time after the fact to determine what had gone wrong and to rework the batch.”
Other issues were also troublesome. Manual bag handling created dust and less-than-ideal ergonomics. In addition, forklifts and workers generated spillage, which led to the loss of ingredients as well as housekeeping issues.
“Our goal was greater and more immediate control over quality,” says McClellan. “We also wanted a solution that would address these other issues and keep operating costs down. We looked at air transporters with weight apparatus, and we talked with companies in that business. We also considered hiring a mechanical contractor to design and build a system to our specifications.
“We knew of Ingredient Masters from their work with other refractories companies* and looked at their solutions as well. When we saw an Ingredient Masters system in operation, it was evident to us that they knew exactly what they were doing and that there was no need to reinvent this wheel. Customers who had come before us had already made the refinements, and the system was extremely reliable. There were no negative issues at all from all the users we talked to.”
*Ingredient Masters systems are used for batching at Riverside Refractory, Uniref, United Specialties and others.
System BasicsA lean alternative to traditional batching methods, the Ingredient Masters’ batching concept immediately reduces material handling within the plant, eliminates manual weighing and raw material shrinkage from spillage, and controls dust.
Typically, the system’s basis is a support structure with individual ingredient dispensers tailored to the application, a scale cart and PC/PLC controls. Many systems have provisions for the addition of minor ingredients in addition to the primary ingredients.
“In our case, we had some special considerations, including ceiling height,” says McClellan. “And we wanted to add some bells and whistles to the software. We found that the Ingredient Masters concept allowed us to design exactly what we wanted. We also saw that it would be easy for us to install the system ourselves, and to train people to run it.”
In June, 2006, 12 weeks following its initial inquiry and eight weeks after the approval of system drawings, Spar took delivery of an 18-dispenser Ingredient Masters batching system. “It arrived in two major sections,” says McClellan. “We positioned everything where we wanted it and bolted it together, bolted the rail (for the cart) to the floor, ran compressed air to the system, did the wiring, and ran dust control lines to a baghouse filter. Peter Hohorst (Ingredient Masters’ controls specialist) managed the electrical end, modified the software and documentation to our specs, and trained us in everything.”
Flexible ReliabilityThe system installed at Spar includes 18 70-cu ft polyethylene dispensers, each with a pneumatic slide gate valve with two dispensing positions, which allows the company to optimize cycle time and discharge accuracy. All of the dispensing hoppers have individual solenoids to control hopper vibration; solenoids are programmed to permit variable cycle pulsing. A scale cart for the batch bags features a power roller deck, and controls include an Allen Bradley PLC and Dell PC.
An Access database is programmed to store unlimited recipe and ingredient information, and to record batch data. The database can be linked to an AS-400 or other central computer, or it can be operated as a stand-alone system. Each recipe is date-stamped with the time of its most recent revision.
A master ingredient list is maintained in the database, along with operating parameters for each ingredient. The parameters are ingredient-specific so the system doesn’t require manual entry of parameters when an ingredient change is made at a dispensing station. “With 18 dispensers, we rarely need to remove an ingredient from a dispenser,” says McClellan. “But when needed, we put the cart in manual mode, drain the material and return it to inventory, and add the new ingredient. The process takes but 10 minutes. So even though every bin has an assigned ingredient, we can change it quickly.”
When a batch is run, the operator selects a recipe from a pull-down menu in Microsoft Access. The recipe is used to create a job order that is assigned a unique number for quality control tracking. All discharge amounts are recorded in the database under this number, along with the date and time the batch was completed. An unlimited number of job orders can be stored in the database, along with preplanned scheduling assignments.
One of the “bells and whistles” McClellan wanted was the ability to simultaneously store two job orders in the PLC, a feature that allows batches from two recipes to run without changing job orders.
At the start of a batch, the scale cart moves under the various ingredient dispensers, stopping at those specified by the program. At each stop, a valve is opened and the ingredient gravity-flows into the cart. The cart weight is indicated in real time on a screen. Ingredient discharge begins in the half-open valve position, moving to a more restrictive position as the specified weight is approached.
Settings can be modified for slower dispensing, as might be needed for coarse ingredients. Fine, lightweight ingredients are flow-assisted using air vibration and/or air puffers. If any discharge is not within the preset limits, the PLC automatically halts the batching process. Dusts are automatically collected as the scale cart moves along its route.
The Ingredient Masters system automatically maintains a deductive inventory of the material in each dispensing hopper. When a discharge is made, the PLC deducts the amount from the available weight in the hopper. When a bulk bag is discharged into a hopper, the operator enters the bulk bag weight onto the RSView screen and the PLC adds the weight to the available weight for the hopper. The system can track ingredient lot numbers and print these on the batch report, if specified.
Improved ProcessesSpar prides itself in being “highly service-driven” and delivering “the highest value in the right product for the right job,” says McClellan. “Particularly with coal-fired power plants, technology has gone far beyond the methods and standards of the past, so materials are different too. Bauxite, mulcoa, new materials and different combinations are what’s needed, along with greater precision in the material mix. That’s what gives you the added value and added refractory life.
“Modern powergen plants use recombust processing to recirculate and reignite for every last Btu of yield. That, in effect, is what we’re doing here-working smarter and more efficiently for a more cost-effective end result. Spar batches are now ± 1% variation, which is extraordinary in our industry. The typical batch size we ship is 3000-4000 lbs, and we often ship 50,000 lbs of one item. A batch of 3000 lbs means we might be ± 8 oz. Now that’s quality.”
For more information regarding batching systems, contact Ingredient Masters Inc. at 1080 Nimitzview Dr., Suite 302, Cincinnati, OH 45230; (513) 231-7432; fax (513) 231-3104; e-mail email@example.com; or visit www.ingredientmasters.com.
Spar, Inc.’s website is located at www.sparref.com.