FIELD OF THE DISCLOSURE

This disclosure relates to water treatment disinfection systems, particularly treatment systems in which calcium hypochlorite is dissolved to make an available chlorine solution, which is fed into the water system.

BACKGROUND OF THE DISCLOSURE

Calcium hypochlorite is a solid, dry chemical that when dissolved generates a hypochlorous acid solution that is then used for disinfection of water. Hypochlorous acid is commonly referred to as "available chlorine." Equipment for dissolving the calcium hypochlorite typically includes a water sprayer or erosion chamber that dissolves the calcium hypochlorite into an available chlorine solution that can then be pumped through a discharge line into a water main for disinfection. An example of such a water sprayer is described in U.S. Pat. No. 5,928,608. Such equipment is commonly called "feed equipment."

In a solution of calcium hypochlorite, material such as calcium carbonate, calcium hydroxide, and other insoluble material can rapidly precipitate out of the solution and solidify in the bottom of the feed equipment. In locations where the water chemistry is alkaline or contains silicates, a reaction with calcium in the water may cause precipitation of hard aggregate that is not easily suspended in the solution. Failure to mix the solution so as to suspend the particles of insoluble material inside the feed equipment results in plugging of the discharge line which results in failure of the equipment. SUMMARY OF THE DISCLOSURE

According to a first aspect of the disclosure, an apparatus is provided for suspending insoluble material in a chemical solution. The apparatus includes a reservoir for holding the chemical solution, a pump for circulating the chemical solution, and a discharge nozzle for mixing. The reservoir has an upper portion, a lower portion, a bottom and a sidewall. The pump has an inlet and an outlet connected to the reservoir by inlet and discharge lines. The discharge nozzle is disposed in the lower portion of the reservoir and discharges the solution toward the bottom of the reservoir; the nozzle has an inlet port connected by a nozzle inlet line to the pump discharge line through the sidewall of the reservoir. The pump inlet line is connected to the sidewall of the reservoir at a location below a normal surface level of the solution, and the pump discharge line is connected to the sidewall of the reservoir above that location. The reservoir, pump, pump inlet line, pump discharge line, nozzle inlet line and nozzle form a closed loop recirculation system effective to suspend insoluble material in the chemical solution.

According to a second aspect of the disclosure, a method is provided including the steps of forming a chemical solution in a reservoir; pumping the chemical solution from the reservoir through a pump inlet line and back to the reservoir through a pump discharge line; and discharging the solution toward a bottom of the reservoir through a discharge nozzle. The discharge nozzle has an inlet port connected by a nozzle inlet line to the pump discharge line through a sidewall of the reservoir. The chemical solution is thus recirculated in a closed loop to suspend insoluble material in the chemical solution.

The foregoing has outlined, rather broadly, the preferred features of the present disclosure so that those skilled in the art may better understand the detailed description of the disclosure that follows. Additional features of the disclosure will be described hereinafter that form the subject of the claims of the disclosure. Those skilled in the art should appreciate that they can readily use the disclosed conception and specific embodiment as a basis for designing or modifying other structures for carrying out the same purposes of the present disclosure and that such other structures do not depart from the spirit and scope of the disclosure in its broadest form. BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a mixing system for a calcium hypochlorite solution, in accordance with an embodiment of the disclosure. FIG. 2 shows details of the mixing nozzle used in the system of FIG. 1 , schematically illustrating liquid flow into and through the nozzle.

DETAILED DESCRIPTION

In accordance with an embodiment of the disclosure, a mixing system 1, shown in FIG. 1 , recirculates a solution in a closed loop on the calcium hypochlorite feed equipment. System 1 includes a pump assembly 50 with a small, high flow, low head centrifugal pump 51, in combination with a solution reservoir 10 which includes a mixing discharge nozzle 70. The centrifugal pump draws solution from the side of the reservoir near the bottom thereof, and circulates and discharges the solution back into the solution reservoir at a higher elevation.

As shown in FIG. 1, reservoir 10 has a sidewall 11 and a bottom 12. Solid chemical product (e.g. calcium hypochlorite tablets or briquettes) is dissolved in the upper portion 13 of the reservoir, and the solution is stored in the lower portion 17. The level of the solution in the lower portion is monitored and controlled using an electronic float switch 14 and a mechanical float valve 15. A grid 31 (including a handle 32) for holding the chemical product is installed in the upper portion of the reservoir. In this embodiment, water is sprayed upward onto the chemical product through the perforations in the grid from spray tree 40. The spray tree is supplied with water from supply line 41. As the chemical product dissolves, a concentrated solution drops down through the grid into a cup 42 having a spout formed therein, and thence into the bottom portion 17 of the reservoir 10.

An outlet valve 21 is installed in the sidewall 11 of the reservoir, below the normal surface level of the solution in the lower portion 17 of the reservoir. (In the cutaway view of FIG. 1, the portion of the sidewall receiving the valve is not shown.) As shown in FIG. 1, valve 21 is typically a ball valve normally in the open position. A line 22 leading from valve 21 connects to the inlet 53 of pump 51. In this embodiment, pump 51 is driven by an electric motor having a power supply 52. Pump 51 has a discharge outlet 54; a line 60 leads from outlet 54 back to reservoir 10. A bleed valve 55 is located at the pump discharge; valve 55 is typically a ball valve normally in the closed position.

Pump discharge line 60, returning to the reservoir, connects to inlet valve 61 (partially shown in FIG. 1), installed in the sidewall 11 of the reservoir above the normal surface level of the solution. Valve 61 is typically a ball valve normally in the open position. A nozzle inlet line 62 in the interior of the reservoir leads from valve 61 through the sidewall to approximately the vertical centerline of the reservoir. Line 62 connects with vertically oriented mixing discharge nozzle 70 (e.g. a "Tank Mixing Eductor" from Spraying Systems Co., Wheaton, Illinois).

Discharge nozzle 70 discharges the pumped solution toward the bottom surface 12 of the reservoir. The solution is agitated by discharge from the nozzle and reflection of the discharge from the bottom surface; the agitation generally has cylindrical symmetry due to the shape of the reservoir and location of the nozzle. FIG. 2 shows an isolated view of nozzle 70. Solution 81 (schematically illustrated in FIG. 2) flowing from line 62 enters the valve at inlet port 75; discharge solution flow 82 is directed downward from nozzle outlet port 76. The nozzle has ports 77 that create a venturi effect and thereby draw the solution back into the nozzle, as shown schematically by arrows 83.

In this embodiment, reservoir 10, line 22, pump 51, lines 60 and 62, and nozzle 70 form a closed loop recirculation system effective to turn over (that is, fully recirculate) the volume of solution in the reservoir approximately every 2.5 minutes. This ensures that insoluble particles remain suspended in the solution. In localities with harsh water chemistry (that is, water that has greater than 150 ppm alkalinity and greater than 5 ppm silicates), the system is also effective to suspend particles of aggregate produced by reaction with calcium.

The solution is drawn out of the reservoir through an outlet valve 71 installed in the sidewall 11, as shown in FIG. 1. A line 72 leads to a chemical feed pump (not shown) that injects the solution into the water flow where treatment is desired. In an embodiment, the chemical solution is an available chlorine solution with a concentration of available chlorine generally in the range of 0.1% to 25%, preferably 0.1% to 20%, or more preferably 0.1% to 12%. In two specific embodiments, the chemical solution is a solution of calcium hypochlorite having a concentration of available chlorine in the ranges of 0.1 % to 12% and 0.1 % to 0.9% respectively.

It is noteworthy that system 1 in the above-described embodiment is external to the chemical feed pump and is easily accessible for maintenance and repair. The centrifugal pump 51 and the mixing nozzle 70 do not require any critical tolerances for operation. In particular, mixing of the solution and suspension of insoluble particles is accomplished in reservoir 10 without any moving parts. The system is therefore suitable for continuous operation.

While the disclosure has been described in terms of a specific embodiment, it is evident in view of the foregoing description that numerous alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, the disclosure is intended to encompass all such alternatives, modifications and variations which fall within the scope and spirit of the disclosure and the following claims.