Blending liquid deicing chemicals precisely
R. Mark DeVries
Superintendent of Operations
McHenry County Division of Transportation
Member, APWA Winter Maintenance Subcommittee
The practice of blending deicing chemicals has certainly been the hot topic for discussion whenever, or wherever, snow and ice personnel gather together. Chemical blending has evolved from the needs of agencies to obtain better performance from their liquid deicing products.
New programs involve research and training. At McHenry County Division of Transportation (MCDOT), key staff members make suggestions that would improve the operational practices. Key points are selected and researched to determine viability. After the project direction and research is completed, training packages are developed with various staff members heading up selected portions. Written documentation procedures were developed for each of the following: brine production, blending methods, product agitation and product transfer. The combined efforts of all have developed an innovative, effective project.
All deicing chemicals have distinct properties and freeze points. Blending chemicals can result in a mixture with the best attributes of each product. It can also result in a catastrophe when done incorrectly. The key is learning chemical properties and how they perform. Choose chemicals that are compatible and blend them precisely. This is how MCDOT achieved this procedure and enhanced its productivity.
McHenry County is located in northern Illinois northwest of Chicago along the Wisconsin border. This region of the country certainly sees its share of snow, ice and cold temperatures. MCDOT has been using liquids in their snow and ice operations for the last eight years. The main focus was pre-wetting applications. Currently all MCDOT snow removal units are pre-wet equipped. All trucks are pre-wet in the auger rather than at the spinner. Liquids are applied whenever salt is spread.
MCDOT has also incorporated an anti-icing program into its operation utilizing 1,800-gallon and 500-gallon units.
Initially, the Division used liquid calcium chloride in pre-wet tanks on four trucks only during very low pavement temperatures. As the program progressed and as awareness grew, all trucks were fitted with systems and liquid salt brine was added to the program. Salt brine was only used in pavement temperatures above twenty degrees and no blending took place. In recent years the Division has experimented and tested different deicing chemicals, including more environmentally friendly options and blending. The Division found benefits from this blending program including the addition of De-ice 55, a sugar beet by-product, to its program.
MCDOT wanted to modify its liquid dispensing system. Chemicals could only be dispensed one at a time. Blending was the result of guesswork and not precision. Products left in the hose were incorporated into the next operator's tank. Improper mixes resulted in problems for operators and equipment. Blending liquid deicing chemicals needed to be precise.
The Division teamed up with an expert, Harvey Williams, a former Illinois Department of Transportation research and development manager and now with Dultmeier Sales, to develop a blending manifold system. Together a system was designed to blend the chemicals precisely. Many other considerations were incorporated into the design as well. The Division wanted the ability to blend all the different chemicals but also to dispense any one product individually. The ability to agitate products in the tanks was needed. A liquid anti-foaming agent also needed to be injected on the dispensing side of the system. The Division wanted to reduce the time spent dispensing products as well. In addition it was determined that a brine production system would be added to this project. Each component went into the design of this new system.
The custom-designed and installed system involved the storage, blending, brine production, and distribution of four different liquid products. Whenever multiple products are incorporated into a blend tank, agitation is a must. During project concept meetings each party in this public-private venture presented their view on system needs. Concept drawings and prototype equipment were presented to the group for final review.
The final system utilizes distribution in excess of 100 gallons per minute, product blending at 50 gallons per minute, pump backup systems, tank agitation, and a precise blending manifold. The system operator can move any of the four different liquid products to any storage vessel by a series of manifolds. The complete system is housed in a heated facility six feet by twelve feet. The two-pump system allows the Brewmaster to make all product selections and simplifies the snow removal operator's process for loading liquids into the truck onboard systems. The truck operator activates a switch located at the fill station and the product is dispensed without actuating multiple valves, working with long hoses, or slow tank fill time. The onboard 100-gallon tanks are now loaded in approximately 45 seconds. In addition, this system draws brine from the onsite brine production unit. The brine maker facility is located over 600 feet from the blending station. The two systems are designed to efficiently move brine from production to storage by more than 100 gallons per minute.
The results meet the goals originally developed. Chemicals are metered and controlled by valves as they are pumped. An example of how this works would be: 100 gallons per minute of salt brine is flowing to the tank. This is clearly indicated on the flow meter. A valve is opened and 10 gallons per minute or 10% of De-ice 55 is pumped in at the same time. Five gallons per minute or 5% of 32% calcium chloride is added. The product is completed with a static mixer. The result is a deicing mixture we call Super Mix. Super Mix is the combination of 85% salt brine, 10% De-ice 55 and 5% calcium chloride. The percentage of each chemical in the mixture can be adjusted as desired. A liquid anti-foam is injected as it is dispensed into each truck.
The resulting mix provides the Division a single product with the benefits and characteristics of all three individual products. The synergy of this mix outperforms the individual products. The eutectic point is unknown; however, effective performance has been observed at pavement temperatures at or below two degrees Fahrenheit by MCDOT. Various experts have advised a potential eutectic temperature of minus fifteen degrees Fahrenheit. We recommend and practice routine weekly product agitation. One product can be used in all MCDOT winter applications. The Division has seen favorable results and a reduction in costs.
Some of the key factors of this project have been (in no specific order):