Liquid purification or separation – Processes – Ion exchange or selective sorption
Reexamination Certificate
2002-01-18
2004-08-17
Cintins, Ivars C. (Department: 1724)
Liquid purification or separation
Processes
Ion exchange or selective sorption
C210S687000, C210S191000, C210S278000
Reexamination Certificate
active
06776913
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to the removal of certain salts, such as those of calcium or magnesium, from water. More particularly, the present invention is directed to a method for efficiently softening water containing certain ions in a manner which limits the volume amount of undesirable waste that is sent to municipality waste treatment systems. Additionally, the present invention includes a water softening apparatus and system useable in small domestic water softeners and existing water and drainage lines.
BACKGROUND OF THE INVENTION
“Hard” water is water which contains dissolved ions, particularly calcium or magnesium ions. These ions react with soaps, which are sodium salts of stearic acid and similar organic acids, to produce a curdy precipitate of calcium and magnesium salts. When hard water occurs in residential waterlines, residents will note that the dissolved calcium or magnesium ions form a precipitant “scum” with soap, which may be seen in residential areas as a bathtub ring, or as a scum which adheres to clothing. In addition, hard water impedes the formation of a soap lather useful in cleansing processes. Hard water can present a considerable problem in washing, reducing the efficiency of boilers, heating systems, and other apparatus, and in certain industrial process use. Accordingly, it is often desirable to provide a means for removing the unwanted calcium or magnesium salts from the hard water, thereby to provide “soft” water which does not contain such ions. This process is known as “softening” water.
The main cause of hard water is generally dissolved calcium bicarbonate (Ca(HCO
3
)
2
). In limestone or chalk regions, calcium hydrogencarbonate is formed by the action of dissolved carbon dioxide on calcium carbonate. In some areas, hardness also results from dissolved calcium sulfate (CaSO
4
).
A common method of softening water, such as in small domestic water softeners, involves the process of ion exchange. Ion exchange is a process whereby a water solution is passed through a column of a material that replaces one kind of ion in solution with another kind. Such materials are known as ion exchange resins. Home and commercial water softeners generally contain cation-exchange resins. These resins consist of insoluble macromolecular substances to which negatively charged groups are chemically bonded. The negative charges are counterbalanced by ions such as sodium ions. When hard water containing the calcium or magnesium ion passes through a column of this resin, the sodium ions in the resin are replaced by calcium or magnesium ions. The reaction may be generalized as follows for calcium:
2NaR(s)+Ca
2+
(aq)→CaR
2
(s)+2Na
+
(aq)
where R
−
is an anion of the exchange resin. The reaction for magnesium (Mg
2+
) is similar to the reaction for calcium.
Water that has passed through the column containing the ion exchange resin contains sodium ions in place of calcium or magnesium ions, and has been softened. Once the resin has been completely converted to a calcium and/or magnesium salt, it can be regenerated by flushing the column with a concentrated solution of sodium chloride to reverse the previous reaction.
To perform this process in residential and industrial use, water softeners generally consist of a resin vessel filled with softening resin, a riser tube that has a screened opening at the bottom of the resin vessel and that extends through a vessel inlet/valve outlet in the resin vessel, and a multi-port valve that directs the flow of water through different channels to and from the resin vessel. In the service cycle, when water is being softened, the hard water would flow through the multi-port valve and into the resin vessel from the outer diameter of the vessel inlet/valve outlet. The water would then go through the resin bed and become softened. The softened water then flows through the screened opening in the riser tube at the bottom of the resin vessel, through the multi-port valve and to the home water supply.
Once the resin has been completely converted to the calcium or magnesium salt, the resin must be regenerated. During regeneration, most softeners flow brine (which is formed by dissolving common rock salt in water) in the same direction as the service flow, and direct the water from the riser tube through the multi-port valve to a common drain, which is generally connected to a sewer. Some softeners may use a countercurrent flow of brine, but also direct all waste to the drain.
The regeneration process generally includes several steps, including a backwash, brine injection, a slow rinse and a fast rinse. While there may be some slight variations in different water softeners (for example, the sequence of the steps or the direction of flow may be different for some configurations), most water softeners generally utilize the same regeneration principles.
For example, in the backwash step water is directed down through the riser tube and flows upward in the resin vessel. This step lifts the resin bed and directs the waste through the outer diameter opening of the resin vessel, through the multi-port valve and to the drain.
The step of brine injection generally involves opening an inlet valve to an eductor/injector. The eductor/injector is generally a venturi valve. The inlet valve is connected to a brine tank, such as with a flexible tube. Brine in the brine tank is formed by water and rock salt that a user puts in the brine tank periodically. Water is generally provided by a step in the regeneration process which directs water through the multi-port valve to the brine tank. The brine tank generally does not require any agitation, rather it simply saturates by soaking in the salt. The brine injection step includes sending city water at full pressure past the venturi valve, thereby causing a pressure gradient and sucking brine in from the injector to mix with the city water (or water from other water sources, such as well water) used to cause the pressure drop. This mixture is directed through the resin bed, up the riser tube, and out the common drain. The cycle is timed to allow the resin exposure to a specific mass of sodium chloride, which is directly proportional to the capacity desired. Generally, the maximum salt required for achieving maximum resin regeneration capacity is exposed to the resin. After a specific amount of time has elapsed, therefore, the brine inlet valve is closed.
During the slow rinse step, city water (or water from a given water source) continues to be sent through the venturi valve. The venturi valve now acts as a flow control device and sends a slow stream of water to the resin bed, thereby rinsing the salt out. The waste is directed to the city drain. During the fast rinse step, city water is allowed to flow at full flow through the resin bed and the water is then directed to the city drain. This step packs the resin bed as well as purges any remaining salt out of the resin vessel. During this cycle, most water softeners also open the brine valve and refill the brine tank. A miniature float check valve in the brine tank shuts off flow when the brine tank has reached its capacity.
The multi-port valves for use with such water softeners consist of various types. For example, Autotrol, a division of Osmonics, located in Minnetonka, Minn., uses flapper valves; Fleck Valves, located in Brookfield, Wis., uses a moving piston with openings at different points, and Erie Valves, located in Milwaukee, Wis., uses a revolving disk with openings at different points.
Because self regenerating water softeners send the waste down the home drain to municipality waste treatment systems, excessive salt levels in the water prevent municipalities from reclaiming the waste water for irrigation and other use. There is increasing pressure from these municipalities, accordingly, to ban self regenerating water softeners. For example, some major areas where water is becoming scarce already do not allow these devices. For example, Irvine, San Diego, San Bernardino and Riversi
Cintins Ivars C.
Gegick Rebecca A.
Henson Michael R.
Martin Timothy J.
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