Sodium bicarbonate producer picks ADM over Cyclones Church & Dwight, Princeton, NJ, produces many products made from sodium bicarbonate for consumer and industrial use. The company markets various consumer products under the Arm & Hammer trademark, such as the familiar Arm & Hammer Baking Soda. Sodium bicarbonate also has many industrial uses, explains project engineer Jim Dynes. "A coarse particle size (or grade) product might be sold to formulate tablet antacids and a medium-grade product could be sold as a leavening agent for commercial bakers. Animal feed producers use sodium bicarbonate as a rumen buffering agent. Soil Drillers use the product for pH control. Sodium bicarbonate gets used in all kinds of things, from pharmaceutical applications to fire extinguishers." At the company's Green River, Wyoming, plant, soda ash is purchased in bulk and stored in silos. To produce sodium bicarbonate, the soda ash is dissolved in a water solution. This solution is filtered and treated to the desired purity before being carbonated, which forms sodium bicarbonate crystal. The crystal is separated from the solution stream and dried. The product is then ground, sifted, classified into multiple grades, and packaged. The plant's original grinding system included an airswept mill and a baghouse. Dried sodium bicarbonate was fed into the mill, ground, and discharged pneumatically to the baghouse prior to being further classified.   Producer seeks method to increase output without costly restructuring A growing demand for the producer's fine sodium bicarbonate powder presented a challenge to increase output without a costly equipment expansion. Because replacing the existing mill with a higher capacity unit would have meant major and costly restructuring, the producer decided to minimize new costs by installing a pre-grinder ahead of the mill to reduce its workload, allowing a higher material throughput. "Once we made the decision to pre-grind, the next question was how to handle the increased dust load on the existing baghouse," said Dynes. "We were limited by what the department of environmental quality regulations would let us do." The producer considered installing a collector ahead of the baghouse or upgrading the bag- house. Upgrading the baghouse was ruled out because it would have required extensive modification to the existing equipment, including an increased fan capacity. Adding a pre-baghouse collector would maintain or even reduce the existing load on the bag- house. "Our environmental department accepted the pre-baghouse collector concept, so I had to decide what type of collector to install," Dynes said. "I considered an aerodynamic collector as well as a traditional cyclone." Installing a traditional cyclone before the baghouse would have meant a costly plant expansion because of limited space. "I chose the ADM because its space requirement was smaller than a cyclone's, and the available space would accommodate it."   Producer installs aerodynamic (ADM) collectors To handle particle collection for the increased sodium bicarbonate capacity, the plant installed two ADM-200 collectors before the baghouse. The compact collector uses aerodynamic forces to efficiently separate and capture particles from gas streams. The collector can be mounted horizontally, vertically, or on an incline. The Aerodynamic Modul is used like a cyclone at the sodium bicarbonate plant: It removes product from the gas stream before the gas stream reaches the baghouse. The dust stream from the collector is blended with the product stream of the baghouse. The ADMs installed easily with little downtime, staff, and ductwork. The units were mounted horizontally in parallel, with a small hopper below for product separated from gas. The setup used existing fans and conveyors.   Annual Output Rises 30 Percent With the ADMs in place, the burden on the baghouse is lighter. "The baghouse used to do all the work," said Dynes. In the past, the plant's full throughput went to the baghouse. "Now I'm running twice our old throughput," he said. "With clean ADMs, 80 percent of the product is knocked out before the gas stream reaches the baghouse." Because sodium bicarbonate adheres to the collectors, and the plant operates 24 hours per day, the collectors must be washed down regularly. "Washing takes only about 5 minutes, but overall disassembly, cleaning, and reassembly takes 4 hours," said Dynes. "As product scales the collectors, the efficiency drops from about 80 percent removal to 30 percent, so we wash them three times per week to maintain efficiency. This also ensures environmental compliance." Prior to installing the collectors, the rest of the milling system required washdown twice per week. The ADMs have reduced that requirement to only once per week. With the pre-grinder and the Aerodynamic Moduls, the grinding system output has increased 30 percent. This was accomplished without any additional labor. "The operators are happy because their instantaneous rate dramatically improved," said Dynes. (The instantaneous rate is the on-demand throughput rate and doesn't include output over a period with downtime.) "The rate has risen 100 percent. And we were able to do that without getting into environmental restrictions."