Abstract:
Method for making salt brine of a desired concentration wherein tap water and recycle dilute brine is passed from a sump tank located indoors into a mixing tank located outdoors. A dilute brine flow from the mixing tank is passed into the sump tank. The concentration of the brine in the sump tank is monitored with a floatable container filled with desired concentration brine. As soon as the container floats in the brine in the sump tank, the brine in the mixing tank is passed into a brine storage tank located outdoors. The salt brine manufacturing system for implementing the method also is disclosed.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH 
     Not applicable. 
     BACKGROUND OF THE INVENTION 
     The present invention generally relates to highway snow and ice control and more particularly to the production of brine therefor. 
     Highway snow and ice control frequently is carried out by governmental authorities with the use of dump trucks, which are seasonally modified by the addition of snow-ice treatment components. Operating systems employed for these snow and ice control implements have been substantially improved over the past decade. An initial such improvement has been achieved through the utilization of microprocessor driven controls over the hydraulics employed with the seasonally modified dump trucks. See, for example, U.S. Pat. Nos. Re 33,835 and 5,318,226. This latter approach, for example, sometimes is referred to as a “zero-velocity” method for salt distribution. 
     Investigations into techniques for controlling snow-ice pavement envelopment have recognized the importance of salt in the form of salt brine in breaking the bond between ice and the underlying pavement. Without a disruption of that bond, little improvement to highway traction will be achieved. For example, the plow merely will scrape off the snow and ice to the extent possible, only to leave a slippery coating which may be more dangerous to the motorist than the pre-plowed road condition. 
     When salt has been simply broadcast over an ice-laden pavement from a typical spinner, it will have failed to form a brine of sufficient salt concentration to break the ice-pavement bond. The result usually is an ice coated pavement, in turn, coated with a highly dilute brine solution developed by too little salt, which will have melted an insufficient amount of ice for traction purposes. This condition is encountered often where granular salt material contains a substantial amount of “fines”. Fines are very small salt particles typically generated in the course of transporting, stacking, and storing road maintenance salt in dome-shaped warehouses and the like. 
     Road snow-ice control studies have revealed that the activity of ice melting serving to break the noted ice-pavement bond is one of creating a saltwater brine of adequate concentration. In general, an adequate salt concentration using conventional dispersion methods requires the distribution of unacceptable quantities of salt on the pavement. Some investigators have employed saturated brine as the normal treatment modality by simply pouring it on the ice covered highway surface from a lateral nozzle-containing spray bar mounted behind a truck. A result has been that the thus-deposited brine concentration essentially immediately dilutes to ineffectiveness at the ice surface, with a resultant dangerous liquid-coated ice highway condition. 
     Attempting to remove ice from pavement by dissolving the entire amount present over the entire expanse of pavement to be treated is considered not to be acceptable from an economical standpoint. For example, a one mile, 12 foot wide highway lane with a ¼ inch thickness of ice over it should require approximately four tons of salt material to make a 10% brine solution and create bare pavement at 20° F. Technical considerations for developing a salt brine effective to achieve adequate ice control are described, for example, by D. W. Kaufman in “Sodium Chloride: The Production and Properties of Salt and Brine”,  Monograph Series  145 (Amer. Chem. Soc. 1960). 
     The spreading of a combination of liquid salt brine and granular salt has been considered advantageous. In this regard, the granular salt may function to maintain a desired concentration of brine for attacking the ice-pavement bond and salt fines are more controlled by dissolution in the mix. The problem of excessive salt requirements remains, however, as well as difficulties in mixing highly corrosive brine with particulate salt. Typically, nozzle injection of the brine is the procedure employed. However, attempts have been made to achieve the mix by resorting to the simple expedient of adding concentrated brine over the salt load in a dump bed. This approach is effective to an extent. However, as the brine passes through the granular salt material, it dissolves the granular salt such that the salt will not remain in solution and will recrystallize, causing bridging phenomena and the like inhibiting its movement into a distribution auger. 
     A practical technique for generating a brine of sufficient concentration to break the ice-pavement bond is described in U.S. Pat. No. 5,988,535. With this technique, ejectors are employed to deposit a salt-brine mixture upon a highway as a relatively narrow, continuous and compact band of material. To achieve such narrow band material deposition at practical highway speeds of 40 mph or more, the salt-brine mixture is propelled from the treatment vehicle at a velocity commensurate with that of the vehicle itself and in a direction opposite that of the vehicle. Further, the material is downwardly directed at an acute angle with respect to the plane defined by the pavement. When the salt-brine narrow band is deposited at the super-elevated side of a highway lane, the resultant concentrated brine from the band is observed to gravitationally migrate toward the opposite or downhill side of the treated lane to provide expanded ice clearance. The result is a highly effective snow-ice treatment procedure with an efficient utilization of salt materials. Because the lanes of modem highways are super-elevated in both a right and a left sense, two spaced apart salt ejectors are employed to deposit the narrow band concentration at positions corresponding with the tire tracks of vehicles located at the higher or elevated portion of a pavement lane. A feature of the apparatus of this system is its capability for being mounted and demounted upon the dump bed of a conventional highway maintenance truck in a relatively short interval of time. As a consequence, these dump trucks are readily available for carrying out tasks not involving snow-ice control. Additionally, the apparatus is configured such that the dump beds remain in a lowered or down position throughout their use, thus improving the safety aspect of their employment during inclement winter weather. 
     Regardless of the snow/ice control technique chosen, the brine still must be manufactured. The manufacture of brine at a central station remains the practical technique of choice for most governmental highway organizations. Practical problems exist, however, in this regard since the brining forming operation should be kept indoors to prevent lines from freezing and for worker safety and comfort. Operation of a front-end loader to move the piles of salt crystals necessary for such brine forming operation, however, can be dangerous if practiced indoors. Then, too, the final brine need not be kept inside, as it needs to be loaded onto the salt-spreader trucks. It is to such operations that the present invention is addressed. 
     BRIEF SUMMARY OF THE INVENTION 
     An system for making brine for use, for example, by state highway departments to de-ice roads is disclosed. The system employs an outdoor hopper into which a front-end loader can load salt (e.g, NaCl crystals or pellets). Located indoors is a sump tank. Tap water and make-up (recycle) brine from the sump tank is pumped from indoors to the outdoor mixing tank to make fresh brine. Brine from the outdoor mixing tank flows back into the sump tank. Located inside the sump tank is a plastic jug filled with the 23.3% NaCl eutectic brine that is desired to be made from the salt in the outdoor hopper. The flows to and from the outdoors mixing tank and indoor sump tank continue until the correct concentration of brine is present in the indoor sump tank. As soon as the sump tank has the correct concentration of brine in it, the plastic jug is buoyed (match in density), which automatically activates a switch that permits the brine in the mix tank to be pumped to the brine storage tank(s) for loading into trucks for dispensing onto highways. 
     The salt brine manufacturing system for implementing the salt brine method includes a mixing tank connected to a source of tap water and to a source of dilute brine. A sump tank for supplying dilute brine to the mixing tank is fitted with a brine product sensor for determining whether the brine therein has a desired concentration of salt to make a brine product. A recirculation pump for passing the source of tap water and the dilute brine from the sump tank to the mixing tank is provided. A storage tank is provided. Finally, a pump is provided for passing a brine product from the mixing tank to the storage tank. 
     Advantages of the present invention include a worker safety manufacturing operation for the preparation of salt brine. Another advantage is a simple, yet reliable technique for the preparation of salt brine. A further advantage is the ability to make a salt brine of desired precise salt concentration. These and other advantages will be readily apparent to those skilled in the art based on the disclosure set forth herein. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a fuller understanding of the nature and advantages of the present invention, reference should be had to the following detailed description taken in connection with the accompanying drawings, in which: 
     FIG. 1 is a piping schematic of the brine forming system of the invention; 
     FIG. 2 is a side elevational view of the sump tank; 
     FIG. 3 is a sectional view taken along line  3 — 3  of FIG. 2; 
     FIG. 4 is a sectional view taken along line  4 — 4  of FIG. 2; 
     FIG. 5 is a side elevational view of the mixing tank; 
     FIG. 6 is a top view of the mixing tank with a partial cut-away at the brine outlet; 
     FIG. 7 is a side elevational view of the mixing tank of FIG. 5 in a dumping position; 
     FIG. 8 is an electrical schematic diagram for the sump and storage tanks; 
     FIG. 9 is the NaCl/H 2 O phase diagram; 
     FIG. 10 is a flow sheet for the electrical schematic diagram in FIG. 8; and 
     FIG. 11 is flow sheet showing the operating logic of the brine forming system of the invention. 
     The drawings will be described in detail below. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     While a variety of NaCl concentrations in the brine will be suitable for use in treating ice/snow covered roadways, the ideal concentration will be about 23.3% NaCl according to the NaCl/H 2 O phase diagram in FIG.  9 . Thus, the present brine forming system is designed for production of such eutectic composition. It will be recognized, however, that other NaCl concentrations also will depress the freezing point of the brine and are included within the precepts of the present invention. 
     Referring initially to FIG. 1, the major components of the brine forming system are a mixing (brine forming) tank,  10 , a sump (or accumulation) tank,  12 , and a brine storage tank,  14 . For worker safety, efficiency, and economy, mixing tank  10  and storage tank  14  are located outdoors, while sump tank  12  is located indoors. It should be recognized, however, that all of these tanks could be located indoors. 
     Mixing tank  10  has a design capacity of about 8 yd 3  and is nominally about 10 ft×4 ft×5.5 ft. Sump tank  12  is smaller, being nominally about 2 ft×2 ft×4 ft. Storage tank  14 , which may be composed of more than one tank, has design capacity of about 6,000 gallons. 
     The various lines, valves, and pumps used to transport materials (water, brine) are depicted in FIG.  1 . Under proper operating conditions, the system produces brine automatically with only oversight provided by maintenance workers. Intervention only is required at tank  10  where feed NaCl is dumped by a front-end loader or other conventional equipment. Conveyors could be used if the extra cost could be justified. The second junction for routine worker intervention is the filling of the brine trucks, such as a truck,  16 , shown in FIG.  1 . Of course routine maintenance of all of the tanks, lines, valves, pumps, etc., will be required. 
     With respect to the construction of the brine forming system, weak brine solution is withdrawn from mixing tank  10  through a ball valve,  18 , via a 3″ line,  20 , and passed into sump tank  12 . Tank  12  is fitted with an internal recirculation loop for brine housed in tank  12  and composed of a 1½″ discharge line,  22 , a recirculation pump,  24 , a 1½″ line  26 , a tee,  28 , a 1½ line,  30 , a globe valve,  32 , and an inlet ½″ line,  34 . Alternatively, weak brine can be recirculated back to mixing tank  10  from tee  28  via a line,  36 , a globe valve,  38 , a line,  40 , a check valve,  42 , a line,  44 , a tee,  46 , and an inlet line,  48 . Make-up tap water can be admitted for recirculation to tank  10  via line  48 . Such tap water is admitted to system through a line,  50 , and is passed through a globe valve,  52 , into a line,  54 , through a solenoid,  60 , into a line,  62 , through a check valve,  64 , and into a line,  66 , which is connected to tee  46  from whence the tap water can flow into line  48  for mixing with the dilute brine being recirculated from tank  12 . 
     Product brine is withdrawn from mixing tank  10  via a ball valve,  68 , and through a strainer,  70 . From there the product brine flows through a line,  72 , and into a transfer (to storage) pump,  76 . Pump  76  pumps the product brine through a line,  78 , and into a tee,  80 . From tee  80 , the product brine flows via a line,  82 , through a globe valve,  84 , a line,  86 , through a check valve,  88 , and finally into an inlet line,  90 , for admission into storage tank  14 . 
     For analysis of product brine in line  78 , a line,  116 , runs from tee  80  to a sampling valve,  118 , from which a sample of brine product can be withdrawn for analysis. A line,  120 , from sampling valve  118  returns brine product in line  116  to vessel  122  of sump tank  12 . 
     For use of the product brine by truck  16 , product brine in storage tank  14  is passed through a ball valve,  92 , into a line,  94 , through a second ball valve,  96 , and into a pump,  98 . Pump  98  pumps the brine product through a line,  100 , and through a ball valve,  102 . The line from ball valve  102  hooks to a truck inlet,  104 , for the brine product to be loaded onto truck  16 . 
     With respect to design of various tanks, reference initially is made to FIGS. 2-4, which depict sump tank  12 , which is seen to include an upper vessel,  122 , mounted atop a frame,  124 , with a lower, gravity fed brine outlet,  123 , and an inlet,  125 . Pumps  24  and  76  are seen mounted to frame  124  underneath vessel  122 . Vessel  122  is seen to carry an electrical panel,  126 , from which three switching mechanisms are disposed. The first switching mechanism,  128 , is seen to include a switch box,  130 , from which extends a lever,  132 , at its proximal end. Lever  132  carries a chain,  134 , at its distal end. The distal end of chain  132  is connected to a float assembly,  136 , which rests on a screen or foraminous plate,  138  (see FIG.  4 ). Float  136  is housed within an angle,  140 , which confines float  136  to moving up and down, rather than into the main body of vessel  122 . Float  136  is filled with the brine desired to be made (e.g., brine product containing 23.3% NaCl). When the brine solution in vessel  122  contains the same concentration of brine as is in float  136 , float  136  floats due to the density match. Before such concentration is achieved, float  136 , rests atop screen  138 . When float  136  rises (floats), lever  132 , also rises, which trips the switch in switch box  130 . Obviously, this means that the correct brine solution has been made so that the brine can be sent to storage tank  14 . 
     Vessel  122  also is seen fitted with two other switch mechanisms,  142  and  144 , carried by switch panel  126 . Each of these switch mechanisms  142  and  144 , respectively, is seen to consist of a rod,  146  and  148 , extending downwardly from switch panel  126  into vessel  122 . The lower ends of each rod  146  and  148 , respectively, are fitted with a float switch,  150  and  152 . Float switches  150  and  152  float on top of the brine housed in vessel  122  and serve as high and low brine indicators, respectively. That is, when float  150  rises with the upper surface of brine in vessel  122 , a switch is activated to stop additional brine and/or tap water from being admitted thereinto. By the same token, float  152  is an indicator of a minimum amount of brine solution being present in vessel  122 . With too little brine in vessel  122 , the recirculation (pump  24  will shut off. When a minimum level is present, the recirculation will activate. 
     Referring to FIGS. 5,  6 , and  7 , mixing tank  10  is seen to include a vessel,  154 , which sits atop a frame assembly,  156  (see FIG.  7 ), which includes a piston,  158 , for dumping the contents of vessel  154 . Such dumping may be necessary since vessel  154  is located outdoors, has not lid, and has salt dumped into it from a front-end loader. It is expected that a certain amount of debris will be dumped in with the salt and other sources, and collect in vessel  154 . Thus, extension of piston  158  enables the debris to be dumped out of vessel  154 . 
     In FIG. 5, about the outlet,  160 , a weir assembly,  162 , provides a flow path calculated to keep debris from being withdrawn along with the brine solution being made in vessel  154 . Mixing in vessel  154  is accomplished with a pair of nozzles,  164  and  166  (see FIG. 6) through which recycled weak brine, optionally with make-up water, is admitted into vessel  154 . 
     The electrical schematic for the system is shown in FIG.  8 . Referring initially to electrical panel  126 , a source of line power,  168 , and ground,  170 , pass into panel  126  with line power  168  terminating at three switches (so-called single throw switches),  172 ,  174 , and  176 , which advantageously are connected to ground fault interrupts (not shown in the drawings). When the inventive brining system initially is activated, the operator “throws” or closes all three switches  172 ,  174 , and  176 . Switch box  130  is a normally open switch. A line,  184 , connects switch  130  to pump  76 . When float  136  rises in vessel  122 , switch  130  is actuated and pump  76  commences to pump brine product from mixing tank  10  to storage tank  14 . 
     High water switch  150  (a normally closed switch) is connected to switch  174  and via a line,  178 , to float switch (normally closed),  180 , in storage tank  14 . Float switch  180  in turn is connected via a line,  186 , to solenoid  60 . If either float switch  150  or float switch  180  is actuated, then solenoid  60  is turned off, because one of float switches  150  or  180  is opened. When solenoid  60  is actuated and the flow of tap water from line  50  is ceased because either vessel  122  or storage tank  14  is at its operating capacity. 
     Low water switch  152  (a normally open switch) is connected to switch  176  and via a line,  188 , to circulation pump  24 . When switch  152  is activated by the presence of a minimum amount of water/brine in vessel  122 , circulation pump  24  is turned on to circulate weak brine between mixing tank  10  and sump tank  12 , and continues even when storage tank  14  is full. 
     Also, all pumps, solenoids, and other electrical equipment also are connected to ground, as shown in the drawings. 
     The operation of the system and a further understanding of the electrical schematic in FIG. 8 can be better understood by referring to the flow diagram in FIG.  10 . Commencing with block  194 , the operator has determined that brine needs to be produced, for example, because of a weather prediction or due to the season. At this time, block  194  calls for the operator to turn on (throw) switches  172 ,  174 , and  176 . The reader will observe that three independent operating sequences determine the operation of the brining system. 
     Referring initially to the left-hand flow path, block  196  indicates the throwing of switch  172 , which energizes the circuit (see FIG.  8 ). Next, at block  198 , float  136  in vessel  122  is polled to check for whether the correct specific gravity (s.g.) of the brine in vessel  122  is the same as the standard brine solution in float  136 . If the answer is “no”, then this step cycles until the answer is “yes”. When float  136  floats in the brine in vessel  122  and switch  130  closes, block  200  shows that a signal is sent to pump  76 , which pumps the brine product to storage tank  14  and block  202  indicates that the brine product is ready for use. 
     Referring now to the central flow path, block  204  indicates the throwing switch  176 . Next, at block  206 , float  152  is polled to determine whether a minimum amount of tap water has passed into vessel  122 . If the answer is “no”, this step cycles until the answer is “yes”. If the answer is “yes”, block  208  indicates that pump  24  is activated to pump water/weak brine from vessel  122  into spray nozzles  164  and  166  in mixing tank  10 . 
     Referring now to the right-hand flow path in FIG. 8, block  210  indicates that the throwing of switch  174 , which powers solenoid  60 . Next, block  212  indicates that float  180  in storage tank  14  is polled. If the answer is “no”, then this step cycles. If the answer is “yes”, then block  214  indicates that float  180  still is closed. Block  214  next is encountered where float  150  is polled. If the answer is “no”, then this step cycles. If the answer is “yes”, then block  216  indicates that solenoid  60  is energized to bring in tap water for pumping to eductors (slurry spray nozzles  164  and  166  of the spray bar assembly) in mixing tank  10  to make brine. If either vessel  122  (normally closed float switch  150 ) or storage tank  14  (normally closed float switch  180 ) is full (a “no” answer at block  212  or block  214 ), then solenoid  216  is not energized and no make-up tap water is brought into the brine producing system. Until ideal design operating conditions, all valves, flow rates, and the like, are set and adjusted so that the amount of tap water introduced into the system is the same as the amount of brine product withdrawn from the system. Though not critical for operation, the embodiment depicted in the drawings utilizes ½″ sample and recirculation lines. All other lines are 1½″ lines except for a 3″ balance line. 
     Now, a controller (CPU or computer) can operate the present system by operating the various valves, pumps, solenoid, and the corresponding flow rates of water and brine in the lines. The logic to accomplish this is set forth in FIG.  11 . Commencing with block  294 , the operator has determined that brine needs to be produced, for example, because of a weather prediction or due to the season. At this time, block  296  calls or the operator to turn on (throw) gfi switches  172 ,  174 , and  176 . At this point, the system at block  298  queries whether mixing tank  10  is full. If tank  10  is not full, then the system proceeds to block  300  where solenoid  60  is activated to admit tap water to flow into the system for passing into mixing tank  10 . 
     The system then proceeds to block  302  where the presence/absence of water in mixing tank  10  is queried. If water has yet to reach mixing tank  10 , then the system loops to block  302  and continues to loop until water is detected mixing tank  10 . Once water is detected in mixing tank  10 , the system proceeds to block  304 . Block  304  also is reached if mixing tank  10  is determined to be full in block  298 . 
     In block  304 , pump  24  is activated so that weak brine is pumped to eductors (spray nozzles  164  and  166  of the spray bar assembly) in mixing tank  10 . The system then proceeds to block  306  where the specific gravity (s.g.) of the brine in vessel  122  is queried. The system loops at this juncture until the correct specific gravity of the brine in vessel  122  is determined by float assembly  136 . 
     Since the brine product now is made, the system polls storage tank  14  to see if it is full. If float assembly  180  determines that storage tank  14  is full, then the system loops and continues to loop until brine product has been withdrawn and float  180  senses the lowering of the level of the brine product in storage tank  14 . Once storage tank  14  needs to be filled, the system proceeds to block  210 , where solenoid  108  and pump  76  are activated. Such activation causes tap water to blend with the brine product being pumped from mixing tank  10  into storage tank  14 . The brine product in block  312  now is ready for use and the system loops back to block  298 . All valves, pumps, flow rates, and the like, can be set and adjusted so that the amount of tap water into the system is the same as the amount of brine product withdrawn from the system, using computer control of the system. Other modes of operation can be implemented also under such computer control regimen. 
     While the invention has been described with reference to a preferred embodiment, those skilled in the art will understand that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims. In this application all units are in the American system (foot, pound, ° F.) and all amounts and percentages are by weight, unless otherwise expressly indicated. Also, all citations referred herein are expressly incorporated herein by reference.