Selected Chemicals and Their Properties

Transcription

1 Selected Chemicals and Their Properties This material contains information on the properties of five commonly used deicing chemicals. They are listed below, with their eutectic concentration, eutectic temperatures and freeze point as determined by the correlating concentration. Chemical Eutectic Temperature C ( F) Eutectic Concentration % Sodium chloride (NaCl) -21 (-5.8) 23.3 Magnesium chloride (MgCl2) -33 (-28) 21.6 Calcium chloride (CaCl2) -51 (-60) 29.8 Calcium magnesium acetate (CMAc) (-17.5) 32.5 Potassium acetate (KAc) -60 (-76) 49 All chemical solutions should only be applied at temperatures well above their eutectic temperature and/or actual freeze point as determined by concentration if not at eutectic concentration. What follows is more detailed information about each chemical, including a phase curve and a chart with concentrations, freeze points, eutectic temperature, and specific gravities. Sodium Chloride Sodium chloride (NaCl) has been used as an ice control chemical on roads since early in this century. Salt is produced by three processes: Rock salt is mined by conventional hard rock mining equipment and techniques Solar salt is produced by the evaporation of sea water and may contain only a small amount of impurities. Evaporated or solution or vacuum salt, a very pure form, is made by drying under vacuum the solution resulting from the injection of water into deep underground deposits. Most salt used for highway applications in North America is rock salt obtained by mining or the evaporation of sea water, Naturally occurring rock salt is the mineral halite, and usually contains between 1% and 4% impurities, mostly gypsum, shale, dolomite, and quartz.

2 ROAD SALT (NaCl) PHASE CURVE 0 30 F ) C g -10 e ( D r e tu e r a p -15 m e T Concentration (%) Pure salt concentration and corresponding specific gravity as measured by a hydrometer at 15 C (59 F). Percent Specific gravity Weight of salt Freeze Point

3 Salt at 15 C (59 F) kg/m 3 (lb/gal) C ( F) (0) 0 (32) (0.432) -3 (27) (0.523) -3.6 (26) (0.613) -4.3 (24.5) (0.706) -5.1 (23) (0.800) -6 (21) (0.895) ) (0.992) -8 (17.5) (1.000) -9 (15.8) (1.100) -10 (14) (1.291) -11 (12.2) (1.392) -12 (10.4) (1.493) -13 (8.5) (1.598) -14 (6.8) (1.705) -15 (5) (1.813) -16 (3.8) (1.920) -17 (1.4) (2.031) -18 (-0.4) (2.143) -20 (-4) (2.256) -21 (-5.8) (2.371) -17 (1.4) (2.448) (13)

4 Magnesium chloride The principal source of magnesium chloride (MgCl2) is brines from Great Salt Lake and imports. Though it is available in solid (hex hydrate flake) form, it is commonly used in liquid form for ice control. Eutectic temperature is about -33 C (-28 F) at a eutectic concentration of 21.6%. Proprietary mixtures are available, containing 25 to 30% MgCl2, with various corrosion inhibitor additives available. One commonly sold concentration is 30% and at this strength it has a freeze point of -17 C (3 F). All chemical solutions should only be applied at temperatures well above their eutectic temperature and/or actual freeze point as determined by concentration if not at eutectic concentration. This 30% brine will not work at the colder temperatures available at the eutectic concentration. However, when the lower concentration brine is used, the option to use at colder temperatures is available but at the expense of melting capacity meaning reduced performance. As the concentration goes down on any chemical, so does the amount of chemical available to work. Therefore, depending on your specific weather conditions and temperatures, the lower concentrations even with the lower eutectic point are usually not the best buy as sometimes advertised, which is why all products and their characteristics must be investigated when products are being selected for use. MAGNESIUM CHLORIDE (MgCl2) PHASE CURVE 0 F TEMPERATURE (Deg. C.) Concentration (%) Magnesium chloride concentration and corresponding specific gravity as measured by a hydrometer at 20 C (68 F).

5 Percent MgCl 2 Specific Gravity at 20 C (68 F) Freeze Point C ( F) (32) (26.4) (25.0) (23.5) (21.8) (20.0) (17.9) (15.7) (13.1) (10.3) (7.3) (4.0) (0.4) (-3.5) (-7.7) (-12.2) (-17.2) (-23.0) (-27.0) (-20.0) (-14.0) (-10.0) (-6.0) (-3.0) (-1.0) (1.0) (3.0) Calcium chloride Two methods are used to manufacture commercial calcium chloride (CaCl2): first, extraction from natural brines obtained from deep wells, principally in Michigan; and second, a chemical process, the Solvay process, in which sodium chloride is made to react with calcium carbonate to produce sodium carbonate (soda ash) and calcium chloride. Manufacturers and suppliers of calcium chloride provide handbooks about their products. One manufacturer in particular has an excellent Calcium Chloride Handbook

6 with complete information about calcium as well as general information and formulas that apply to all products. All chemical solutions should only be applied at temperatures above their eutectic temperature as determined by concentration. CALCIUM CHLORIDE (CaCl2) PHASE CURVE F TEMPERATURE (Deg C.) Concentration (%)

7 Calcium chloride concentration and corresponding specific gravity as measured by a hydrometer at 25 C (77 F). Percent CaCl2 Specific Gravity at 25 C (77 F) Freeze Point C ( F) (+32) (+27) (+25) (+24) (+23) (+21) (+20) (+18) (+16) (+14) (+12) (+10) (+8) (+5) (+2) (-1) (-4) (-8) (-12) (-16) (-20) (-25) (-31) (-38) (-46) (-53) (-60) (-52) (-34) (-17) (-4) (+10) (+20) (+30) (+39) (+48) (+55) (+61) (+65) (+69)

8 Calcium magnesium acetate CMA [CaMg2 (CH3COO)2]6 is manufactured using the reaction of acetic acid with dolomitic limestone. Acetic acid, the costly component of the compound, is manufactured from natural gas or petroleum, though small quantities have been produced by biodegradation of agricultural wastes. The compound is available as pellets or crystals. Though not as soluble in water as NaCl and CaCl2, solutions can be made for use as a prewetting agent or straight liquid chemical application. It is not a highly effective deicing chemical in solid form because of its light particle mass. Its benefit is that snow is made mealy and will not compact. The eutectic temperature is about -28 C (-18 F) at a concentration of 32.5%, though typically used at 25% concentration, which provides a stable solution. CALCIUM MAGNESIUM ACETATE (CMA) PHASE CURVE 0-5 TEMPERATURE (Deg. C.) Concentration (%)

9 Calcium magnesium acetate (CMA) concentration and corresponding specific gravity as measured by a hydrometer at 20 C (68 F). Percent CMA Specific Gravity at 20 C (68 F) Freeze Point C ( F) (32.0) (31.5) (31.0) (30.5) (30.0) (29.5) (28.9) (28.0) (27.1) (26.2) (25.3) (24.1) (23.0) (21.7) (20.5) (19.0) (17.8) (16.2) (14.5) (12.7) (11.1) (9.3) (7.5) (6.3) (3.4) (1.2) (-0.9) (-3.3) (-5.4) (-8.0) (-10.5) (-13.7) (-16.6) (-18.4)

10 Potassium acetate Potassium acetate (KC2H3O2), or KAc as it is commonly known, is produced by the reaction of acetic acid with potassium carbonate. The sources of acetic acid are the same as are used in the production of CMA. Potassium carbonate is one of the group of salts commercially known as potash. Potassium carbonate was originally obtained by running water through wood ashes and boiling the resulting solution in large iron pots. The substance that formed was called potash. Potassium carbonate is currently produced by one of several processes that use potassium chloride, another salt of the potash family. The compound potassium acetate is a white, crystalline, deliquescent powder that has a saline taste. It is soluble in water and alcohol. Solutions are alkaline under a litmus test. The dry compound is combustible but is used as a dehydrating agent, a reagent in analytical chemistry, and in the production of synthetic flavors, in addition to other uses. The eutectic temperature of a KAc and water solution is -60 C (-76 F) at a concentration of 49%. A commercial form of liquid KAc, containing a 50% concentration by weight plus corrosion inhibitors, has been used as a prewetting agent with dry salt or as a straight chemical application. Some experience has been gained with the straight liquid form during anti-icing experiments.

11 POTASSIUM ACETATE (KAc) PHASE CURVE F TEMPERATURE (Deg. C.) Concentration %

12 Pure potassium acetate concentration and corresponding specific gravity as measured by a hydrometer at 20 C (68 F) Percent KAc Specific Gravity at 20 C (68 F) Freeze Point C ( F) Percent KAc Specific Gravity at 20 C (68 F) Freeze Point C ( F) (32) (1) (32) (-1) (31) (-3) (31) (-6) (30) (-8) (30) (-11) (29) (-13) (28) (-16) (27) (-19) (26) (-22) (25) (-24) (24) (-27) (23) (-30) (22) (-33) (20) (-37) (19) (-40) (18) (-43) (16) (-47) (14) (-50) (13) (-54) (11) (-57) (9) (-61) (7) (-65) (5) (-69) (3) (-73) (1) (-77)

13 TAPER LOG Location: Service Level Goal: Start Date: End Date: Ta T Pave Air A P E R $$$$ Alternative Note$ $$$$ Column Codes Ta = Time of Application P = Product Used T = Low Temp Since Last Application E = Event A = Application Rate-Gallons/Lane Mile (GPLM) R = Results Liters per lane kilometer (LPLkm) *Taper Log content used with the permission of Dale Keep Service Level Codes-Goals A = Bare/Bare and Wet Pavement C = Bare/Bare and Wet Tracks E = Ice or Compact Snow and Ice

14 TAPER LOG DESCRIPTION In order to make any true cost of use or effectiveness comparisons, one must have accurate and complete data to work with. This is a major problem, as employees are busy trying to provide a service rather than fill out paperwork. This amplifies the need to make the data gathering process both simple and compatible with normal work operations rather than change operations to match data collecting and interfere with the real job. With this in mind, I set out to provide a form for employees to use that is quick and easy to use, and yet complete in the information provided. Additionally, this form had to be composed in such a manner as to allow for simple codes to identify level of service goals and existing conditions. This form and its codes when utilized provides for consistency in reporting, terminology, and definitions of common terminology. The result of all this is the following form called a T.A.P.E.R. log. The name T.A.P.E.R. is an acronym for the elements of data collected on the form: T. Temperature A. Application Rate P. Product(s) Applied E. Event. Used to report weather information R. Results. Used to report the results of previous actions. Another benefit of the TAPER system is to give employees clearly defined guidelines on when to start working a storm event, and more importantly, when to quit. Often it is left up to the individual to determine what to do to reach the defined level of service goal or what is acceptable in determining costs required while achieving it. This results in a wide range of opinions as to what to do, and associated costs for work conducted on a similar storm. It is intended that the use of this form in addition to collecting data will also eliminate theses differences. This will result in consistent winter operations work procedures and deicer application rates under like circumstances and has the potential to greatly reduce costs. Definitions: Event Event Duration Slack Time Winter Operations Any weather occurrence that takes us from a mode of no action (slack time in terms of winter operations) to a mode of winter operations action required. The length of time the event required winter operation actions of some kind. That period of time where weather conditions do not require plowing, sanding, or other winter operations. Or, a time to accomplish other work tasks at hand. Work that is accomplished only during winter months, and is brought about solely by winter weather. Dale Keep Ice and Snow Technologies, Inc (IST) Page 1 of 4

15 TAPER Log Elements Defined: Start Date End Date Note. Service Level or Road Condition Codes: The date in which crews are taken from slack status and mode of operation to event status and mode of operation. The date in which crews are taken from event status and mode of operation back into slack time status and mode of operation. The following Level Of Service (LOS) codes are for example only, and the actual number of LOS goals and their definitions must match your operational needs. This code is used to describe the level of service goal for a particular area. These codes are also used as a way to describe current conditions at the time of the log entry, and as a winter operations quality standard that advises employees when no more time, money or effort is required or desired. A. Bare Surface is the goal here, and work will normally consist of pretreatments and continue using a variety of methods to achieve or maintain this level of service. C. Bare Tracks is the goal here. Chemical applications and all work is done with this level of service in mind. Typically no more than one inch of buildup is allowed outside of the wheel tracks. No time, money, or effort will be expended to upgrade from this level of service once achieved. E. A plowed surface, ice or compact snow and ice with grit or sanding material on it is acceptable. No more than 2 inches of loose snow is desirable before plowing begins. Chemical Applications Codes Ta Time of application: What time was the chemical application made? Or, in the case of no application being made, the time the entry is made on the log. T Temperature: Current temperature as noted at the time of the application or log entry. Note that the log asks for both Air and Pavement Surface (Pave) temperature. Fill in both if at all possible. Surface temperature is most important, but either is better than nothing. A Application Rate. How much product was applied? Report in terms that are meaningful to you. Dale Keep Ice and Snow Technologies, Inc (IST) Page 2 of 4

16 P Product: What product is being applied? Know what you are using and write it down. This is important, as the product can change. Going from a dry solid deicer to a liquid or to a prewet solid is a good example. In this case report should include something like: 300 pounds of sold deicer applied with 8 gallons per ton of pre-wetting material. Could snow on report as 300+8, and regular workers would know what it means. E Event: What are the weather conditions observed at this time? This entry when compared with the previous entry provide a pictures of the changing or continuing weather. This provides information on what has happened in terms of moisture (i.e. snow fall) and temperature since the last time you were there. R. Results: What are the results or current conditions? This can be indicated with one of the service level/ surface condition codes as shown on the log. ALTERNATIVE NOTE$ This area is used to enter any beneficial comments. It is the intent that the use of this area when combined with other log data will allow for correct and accurate cost comparisons between LOS goals, products and different work methods. Thus, the ($) dollar signs serve as a reminder of the intended use of this area on the form. After the TAPER log has been used for a period of time it is now possible to put the data to use to further refine chemical applications and operational needs. This will result in a change from effective deicer applications to efficient applications and result in additional savings. To accomplish this, pull from the TAPER log, the information from the different storm events that resulted in the desired LOS goals or results. Be sure that the total for chemical applications, the lowest temperature observed during a storm event, the total precipitation received during a storm event and plowing conducted is used for analysis. This information can then be put into an Application Rate Chart similar to the following. With experience and the data gather by use of the T.A.P.ER. Log, one can soon match chemical applications and work methods to a given storm event saving dollars and environmental impact while delivering required level of service goals. The following example is based on a liquid application rates, and is for demonstration only and does not represent actual application rates. Dale Keep Ice and Snow Technologies, Inc (IST) Page 3 of 4

17 DEICER APPLICATION RATES PRECIPITATION TEMP- º F. 1" 2" 3" 4" **NUMBERS ARE USED TO DEMONSTRATE THE SYSTEM, AND ARE NOT ACTUAL APPLICATION RATES!** Separate T.A.P.E.R. logs and Application charts should be developed for different locations due to potential variances in surface conditions and weather patterns. This also provides better data when this log is utilized in multiple trucks and is filled out regularly. With the T.A.P.E.R. system, and some effort, winter deicer applications and work methods can be matched to a storm event based on your successful experiences. With this system, the application rates developed are for your deicer product(s), area, work methods, and are based on your experiences. For example, with this chart, if a storm were predicted to deliver 1 inch of snow at a low of 28 degrees Fahrenheit, an application of 45 GPLM would be made and combined with other normal work methods utilized to achieve success. Terms of use. The use of the TAPER log system is authorized by Dale Keep. Results are not guaranteed and the user assumes any and all risks that may be associated with its use. The log it is sent with this document. Feel free to share the log and this document with anyone that may benefit from its use. However, please send both the log and the description together. TAPER LOG sept 29, 2014.pdf Dale Keep Ice and Snow Technologies, Inc (IST) Page 4 of 4