MAR-APR 2017

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COVER STORY INTECH MARCH/APRIL 2017 9 FAST FORWARD l The existing wireless system had limited I/O capacity and could not handle data from new wells, some of which were more than a mile from the production plant. l To avoid hardwiring data from new wells, Natural Soda installed a wireless I/O card at its existing control system. l The new wireless network will accommodate more well pads and wireless transmitters, allowing further expansion and the addition of wireless monitoring of tank levels soon. A key element of the BLM mine plan is controlling the pres- sure of the saline aquifer (referred to as the dissolution sur- face aquifer) immedi- ately above the min- ing zone. The mine plan specifies that the pressure in this aqui- fer must stay below the pressure of the upper freshwater aquifers to eliminate the potential of cross contamination between the aquifers. Continuous monitoring and adjustment of injection and recovery flow, temperature, and pressure allow us to maintain full compliance with this requirement, and to collect the neces- sary historical data for proper record keeping and required regulatory submissions. Upgrading the system The original Natural Soda facility was built in 1990 with the capacity to produce 60,000 tons per annum (tpa) of feed-grade product to be sold domestically. Expansion in 1996 increased capacity to 125,000 tpa. In March 2013, Natural Soda completed construction of an additional production train, increasing annual production from 125,000 tpa to 250,000 tpa, making Natural Soda the second-largest producer of sodium bi carbonate in the U.S. In addition to the new train, the expansion included additional packaging and distribution infrastructure, supporting Natural Soda's move to provide sodium bicarbonate to multiple markets, such as the highly competitive food Located in Northwest Colorado in the Picean ce Creek Basin, Natural Soda operates seven pro- duction well pairs to produce saturated nahco- lite brine for manufacturing sodium bicarbon- ate (baking soda). The plant is approximately 50 miles northwest of Rifle, Colo., on property managed by the Bureau of Land Management (BLM), which is part of the U.S. Department of the Interior. Mining nahcolite requires very careful moni- toring of temperature, pressure, and flow to not only optimize production performance—but also to mine the product sustainably and pro- tect the freshwater aquifer. Wireless transmitters make it possible to monitor remote injection wells to protect the environment, increase effi- ciency, and improve productivity. Our operating permits require us to continuously monitor and record fluid temperature, pressure, and flow rate in both the recovery and injection wells. We must also keep these parameters within speci- fied ranges as detailed in our BLM-approved mine plan. The facility is located in mountainous, rugged terrain (figure 1), making it difficult and very expensive to employ wired devices. To improve overall efficiencies, we installed wireless tem- perature, pressure, and flow sensors to monitor all the parameters specified in the plan. Protecting the aquifer Natural Soda recovers sodium bicarbonate us- ing a process known as solution mining. This involves pumping heated water approximately 1,900 feet underground (figure 2) to dissolve the underlying nahcolite beds. The water, now satu- rated with sodium bicarbonate, is then returned to the surface by a submersible pump. Figure 2. Solution mining involves the injection of steam into a 2,000-foot long seam of nahco- lite to form a brine solution that is pumped up and sent to the production plant. A freshwater aquifer lies between the surface and the nah- colite seam, making control of pressure critical. Some of these wells are more than a mile away from the processing facility.

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