Water softener abstract
A method and apparatus for selecting the quantity of salt to be
used during each regeneration of a water softener system. The quantity
of salt used during each regeneration is approximately equal to
the quantity of salt needed to regenerate the resin bed to a preselected
design capacity, which is less than the maximum capacity of the
resin bed. The design exchange capacity is approximately equal to
the exchange capacity of the resin bed at a particular salt dosage,
wherein the exchange capacity of the bed at the particular salt
dosage divided by the particular salt dosage is generally equal
to or greater than 2850. The system is regenerated when at the end
of any preselected time period, the percentage of the design capacity
of the resin bed used since the last regeneration cycle exceeds
a predetermined percentage. In determining the salt dosage used
during each regeneration cycle, the exchange capacity of the resin
bed is determined for various salt dosages. The available exchange
capacity of the resin bed is determined by subtracting the exchange
capacity of the resin bed used since the last regeneration from
the selected design capacity of the resin bed. The salt dosage used
during each regeneration is approximately equal to the salt dosage
of the resin bed at the design exchange capacity less the salt dosage
of the resin bed at the available exchange capacity of the resin
bed. The apparatus of the present invention utilizes a micro-computer
to automatically make the necessary calculations to determine when
to regenerate the resin bed and to determined the proper salt dosage
fill time to the brine tank prior to each regeneration. A turbine
water meter located in the soft water outlet line measures the water
usage since the last regeneration.
Water softener claims
What is claimed is:
1. A method of regenerating the bed of exchange resin in a water
softener by selecting the proper salt dosage for each regeneration
cycle, said method comprising the steps of:
(a) determining the approximate exchange capacity of the bed of
resin as a function of a plurality of different salt dosages;
(b) selecting a predetermined design exchange capacity to which
the bed of resin is to be regenerated during the regeneration cycle;
(c) determining the approximate available exchange capacity of
the bed of resin immediately prior to regeneration;
(d) determining the salt dosage determined in step (a) at the predetermined
design exchange capacity;
(e) determining the salt dosage determined in step (a) at the approximate
available exchange capacity determined in step (c);
(f) determining the salt dosage for regenerating the bed of resin
by subtracting the salt dosage determined in step (e) from the salt
dosage determined in step (d); and
(g) passing a brine solution through the bed of resin in said water
softener, said solution having the salt dosage determined in step
(f).
2. The method as defined in claim 1 wherein the approximate exchange
capacity of a predetermined number of different salt dosages are
determined in step (a) and the salt dosage determined in step (e)
is determined by selecting the salt dosage at the closest exchange
capacity as determined in step (a) which does not exceed the approximate
available exchange capacity.
3. The method as defined in claim 1 wherein the approximate exchange
capacity of a predetermined number of different salt dosages are
determined in step (a) and the salt dosage determined in step (e)
is determined by selecting the salt dosage at the exchange capacity
as determined in step (a) which is closest to the approximate available
exchange capacity.
4. The method as defined in claim 1 wherein the exchange capacity
of the bed of resin as determined in step (a) for each of the different
salt dosages is approximately equal to the exchange capacity of
the bed of resin when the bed is exhausted to one grain hardness
and subsequently regenerated with the particular salt dosage.
5. The method as defined in claim 1 wherein the design exchange
capacity selected in step (b) is approximately equal to the exchange
capacity of the bed of resin as determined in step (a) at the level
wherein the exchange capacity divided by the salt dosage is approximately
2850.
6. The method as defined in claim 1 wherein the approximate available
exchange capacity of the bed resin in step (c) is determined by
substacting the capacity of the bed of resin used since the last
regeneration from the predetermined design capacity as selected
in step (b).
7. The method as defined in claim 6 wherein the capacity of the
bed of resin used since the last regeneration is approximately equal
to the volume of water passing through the bed of resin since the
last regeneration multiplied by the hardness of the water passing
through the bed of resin.
8. A method of regenerating a water softener having a bed of exchange
resin through which water is passed therethrough, comprising the
steps of:
(a) selecting a predetermined design exchange capacity to which
the bed of resin is to be regenerated during the regeneration cycle;
(b) determining the percentage of the design capacity of the bed
of resin used since the last regeneration;
(c) regenerating the bed of resin when the percentage as determined
in step (b) exceeds a preselected percentage by passing a brine
solution through the bed of resin having a salt dosage selected
by:
(i) determining the approximate exchange capacity of the bed of
resin as a function of a plurality of different salt dosages;
(ii) determining the approximate available exchange capacity of
the bed of resin immediately prior to regeneration;
(iii) determining the salt dosage determined in step (i) at the
predetermined design exchange capacity;
(iv) determining the salt dosage as determined in step (i) at the
approximate available exchange capacity determined in step (ii);
and
(v) substracting the salt dosage of step (iv) from the salt dosage
of step (iii).
9. The method as defined in claim 8 wherein the bed of resin is
regenerated when the percentage as determined in step (b) exceeds
the preselected percentage at the end of a preselected time period.
10. The method as defined in claim 9 wherein the preselected percentage
is approximately 30%.
Water softener description
BACKGROUND OF THE INVENTION
The present invention relates to a novel method and apparatus for
regenerating the water softening or conditioning material in an
automatic water softener.
Water softening with ion exchange material such as resin particles
or the like is well known in the art. During the softening process,
or service cycle, the ion exchange resin particles acquire hardness
inducing ions from the water in exchange for soft ions, or ions
which do not induce hardness. After prolonged contact of the resin
particles with raw water, their ion exchange capacity is diminished
considerably and periodic regeneration of the resin particles must
be accomplished, conventionally by contacting the resin particles
with a brine solution, i.e., an aqueous solution of sodium chloride
or potassium chloride or the like.
The ion exchange process and the regeneration of the ion exchange
material are accomplished in a softener or resin tank of well known
construction, while a separate brine tank is conventionally employed
to manufacture brine for use during the regeneration cycle. When
regeneration is initiated in the system, brine is drawn from the
brine tank and passed through the bed of ion exchange material in
the softener tank to reverse the exchange of ions and revitalize
the bed by removing hardness inducing ions and replacing them with
sodium ions, for example, from the brine solution.
The precise amount of brine which is required to regenerate a bed
of ion exchange materials of predetermined volume, is dependent
uon the extent to which the bed is exhausted during the service
cycle. This, in turn, is dependent upon a number of factors, including:
(1) the extent of hardness of the water being treated; and (2) the
quantity of water treated during a service cycle. In order to enhance
the economy of the system, it is desirable to precisely limit the
amount of salt utilized in each regeneration cycle and the frequency
of each regeneration cycle to the amount required.
Most water softeners are designed to regenerate on a predetermined
timed cycle determined by taking into consideration the above-mentioned
factors. Because of this, if a water softening system is subjected
to either an abnormally high or low usage during a particular period
of time, the water softening system will still regenerate itself
during the predetermined regeneration cycle. In the instance of
abnormally low usage, a waste of salt and water results, and in
the instance of abnormally high usage, the water softening system
is unable to adequately soften all of the water passing through
the system.
There have been many proposed systems to solve the above mentioned
problem. Such systems have been based upon utilizing means to detect
the state of exhaustion of the resin bed or utilizing means to measure
the quantity of water which has passed through the resin bed since
the previous regeneration.
Examples of heretofore used systems which attempt to detect the
state of exhaustion of the resin bed are disclosed in U.S. Pat.
Nos. 3246759 and 4257887. These systems have a plurality of
spaced electrode probes mounted in the resin bed to detect the condition
of the resin bed, and when the condition is such that rejuvenation
should occur, a control circuit is activated to command regeneration.
These systems rely on the difference in conductivity of exhausted
and rejuvenated resin particles. These systems have proved to be
generally unreliable in operation, relatively expensive, and the
salt usage is not always in direct proportion to the volume of soft
water produced.
One example of a system which utilizes a means to measure the quantity
of water which has passed through the bed is disclosed in U.S. Pat.
No. 3687289. This system includes a metering device associated
with the soft water line to meter a predetermined proportion of
water from the soft water line. The metered water is directed to
a chamber having an adjustable water storage capacity. The proportion
of water metered from the soft water line is directly proportional
to the storage capacity of a pump chamber. The water stored in the
chamber is periodically directed to the brine storage tank. The
brine storage tank includes means to activate a timer to signal
the need for regeneration when the water level in the brine tank
reaches a predetermined level. The proportion of water metered into
the brine tank is adjusted dependent upon the hardness of the water
being treated.
The above discussed water softener systems signal a regeneration
as usage proceeds through an allocated amount of soft water. However,
the actual time of regeneration is usually delayed to occur at night
as is the custom. Therefore, a reserve capacity in the resin bed
is required to provide soft water for the remaining portion of the
day after the signal point is reached. The reserve point is typically
selected to correspond with the point when approximately 70% of
the capacity of the resin bed is reached. This large reserve is
needed to maintain soft water service in the event that the signal
point is reached early in the day. Although such water softener
systems may be designed or adjusted to vary the reserve capacity
of the resin bed, they will repeat thereafter with a fixed reserve
capacity.
With the advent of micro-computer technology, a water softener
system was recently designed which utilizes a micro-computer to
adjust the reserve capacity from day to day in response to the usage
encountered. The system includes a water meter turbine which determines
the quantity of water passing through the resin bed. The micro-computer
calculates the percentage of the capacity of the resin bed used
since the last regeneration based upon the quantity and hardness
of the water which has passed through the resin bed. The micro-computer
employs an algorithm to make its calculations and decisions as time
and water use accumulates. The algorithm allows a large reserve
on early days following a regeneration and continues to reduce the
amount of reserve capacity as more days of significant water usage
go by since the last previous regeneration. At such time as the
reserve capacity for that day is reached, the water softener is
scheduled for regeneration that night and is regenerated with a
preselected fixed quantity of salt.
A similar system to the system described immediately hereinabove
utilizes a similar algorithm with additional criteria for reducing
the probability of overrunning the variable reserve. This system
determines and stores water usage averages for each particular day
of the week. At the end of each day the calculated remaining reserve
capacity in the resin bed is determined and compared with the stored
water usage average for the next day. If the remaining reserve capacity
is not adequate to meet the expected demands of the next day, the
water softener is scheduled for regeneration that night with a preselected
fixed quantity of salt.
The above described micro-computer systems utilize a variable reserve
capacity and are able to schedule regenerations more in proportion
to water usage and thereby reduce the reserve capacity of the resin
bed at the time of regeneration more accurately than in prior systems.
However, in both of these systems, a fixed quantity of salt is utilized
during each regeneration. The quantity of brine solution which is
directed through the resin bed is the same during each regeneration.
Accordingly, in instances when the reserve capacity of the resin
bed is relatively high at the time of regeneration, an excess quantity
of salt is passed through the bed than is necessary to fully rejuvenate
the resin particles in the bed. This results in a waste of salt.
SUMMARY OF THE INVENTION
The water softener system of the present invention employs a method
of selecting the quantity of salt to be used during each regeneration
of the system. The system employs automatic means to account for
and efficiently use the water softener's residual capacity that
results when the softener's resin bed is regenerated prior to complete
exhaustion. The method of the present invention further maximizes
the efficient use of the salt during each regeneration by selecting
the quantity of salt needed to regenerate the resin bed to a preselected
design capacity, which is less than the maximum or theoretical capacity
of the resin bed. More specifically, the method of regenerating
a water softener in accordance with the invention, includes an initial
selection of a design exchange capacity to which the resin bed is
to be regenerated during each regeneration cycle. This design exchange
capacity is preferably approximately equal to the exchange capacity
of the resin bed at a particular salt dosage wherein the exchange
capacity of the bed at the particular salt dosage divided by the
particular salt dosage is approximately 2850. It has been determined
that such a design capacity makes efficient use of the salt in the
brine solution during each regeneration cycle. The system is regenerated
when at the end of any preselected time period, the percentage of
the design capacity of the resin bed used since the last regeneration
cycle exceeds a predetermined percentage. This percentage in accordance
with the preferred embodiment of the invention is approximately
30 percent. The resin bed is regenerated with a brine solution having
a salt dosage which is approximately equal to that which is necessary
to regenerate the resin bed to its design capacity.
In determining the salt dosage used during a regeneration cycle
in accordance with the invention, the exchange capacity of the resin
bed is determined for various salt dosages. The exchange capacity
of the resin bed for each salt dosage is approximately equal to
the capacity of the resin bed when the resin bed is exhausted to
one grain hardness and subsequently regenerated with the particular
salt dosage. This procedure is repeated for different salt dosages
to determine the exhange capacity of the resin bed at the various
selected salt dosages.
The available exchange capacity of the resin bed is determined
by subtracting the exchange capacity of the resin bed used since
the last regeneration from the selected design capacity of the resin
bed. The exchange capacity of the resin bed used since the last
regeneration is determined by measuring the volume of water passing
through the resin bed since the last regeneration and multiplying
such volume by the hardness of such water. The salt dosage used
during each regeneration cycle is then determined by subtracting
the previously determined salt dosage of the resin bed at the available
exchange capacity from the previously determined salt dosage of
the resin bed at the design exchange capacity.
The apparatus in accordance with the invention utilizes a turbine
water meter located in the soft water outlet line of the water softener
to measure the water usage in gallons since the last regeneration.
A micro-computer is provided which is programmed to receive an input
from the water meter and automatically make the necessary calculations
to determine when to regenerate the resin bed and to determine the
proper salt dosage fill time to the brine tank prior to each regeneration.
The micro-computer is programmed to receive and store the water
hardness of the water being treated and to base its calculations
thereon.
The regeneration of the resin bed of the water softener in accordance
with the above method and apparatus restores the resin bed fully
to its design capacity upon completion of each regeneration cycle
of the water softener. The amount of salt dissolved in the brine
tank prior to each regeneration is just enough to restore the resin
bed to its design capacity. The water softener will always have
at least 70 percent of its design capacity available for use at
the beginning of each scheduled period of use.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic representation of an automatic water conditioning
system of the general type which embodies the present invention.
FIG. 2 is a graph which illustrates a curve representing the exchange
capacity of a resin bed as a function of salt dosage.
DESCRIPTION OF PREFERRED EMBODIMENTS
Referring to FIG. 1 a water conditioning system of generally conventional
construction is illustrated schematically at 10. The system 10 is
designed to soften water when it is delivered to a residence, business,
or the like, during a "service cycle" of the system. Periodically
the system 10 is "regenerated" in a generally conventional
manner by the use of a brine solution in a regeneration cycle or
cycles. As is already evident, the present invention is primarily
concerned with the control of the brine solution during the regeneration
cycle.
During the service cycle, the raw or hard water from a suitable
source is passed through a feed line 11 to a control valve 12. The
control valve 12 directs the raw water through a line 14 to a resin
tank 16 which contains a bed of the ion exchange particles. The
raw water passes through the bed of particles and is withdrawn from
the tank through a line 17. The treated water, which has been softened
by contact with the ion exchange resin particles, passes through
the line 17 to the control valve 12 once more and is directed by
the control valve 12 to a service line 18.
In a manner that will be further discussed hereinbelow, after a
quantity of raw water has passed through the resin tank 16 at a
time when the ion exchange particles have begun to lose their capacity
to effectively soften the raw water, regeneration is initiated by
a timer 20. This regeneration conventionally includes cycles wherein
the ion exchange particle bed is backwashed and rinsed. It further
includes a brine cycle wherein the ion exchange particle bed is
treated to flow through by a brine solution. The brine cycle is
initiated by the timer 20 to actuate the control valve 12 and direct
water through a bypass line 22 to an aspirator valve 23. This water
is returned to the control valve from the aspirator valve 23 through
a return line 24 but, in passing through the aspirator valve 23
it establishes a pressure reduction by Venturi effect in a brine
line 25 from the brine tank 26. Brine is drawn by the partial vacuum
and flows with the water through the line 24 and the control valve
12 into the line 17 and resin tank 16. The brine flowing through
the bed of ion exchange resin particles removes the hardness inducing
ions therefrom and carries them through the line 14 and the control
valve 12 to the drain line 27. As long as there is brine available
to the brine line 25 in the brine tank 26 and while a partial vacuum
is maintaned therein, brine treatment of the ion exchange resin
bed in the resin tank 16 continues. It is desirable, of course,
to have precisely the amount of brine available which will efficiently
regenerate the bed of ion exchange resin material which has been
exhausted to a known extent. Accordingly, the present invention
is directed to an improved method and apparatus for efficiently
using the residual capacity remaining at the time of regeneration
by precisely determining the quantity of salt to be used during
each regeneration cycle.
The theoretical exchange capacity (G) of the bed of resin particles
in resin tank 16 may be approximated as follows:
where:
G=exchange capacity of the resin bed in grains
Q=quantity of resin in cu. ft.
C.sub.R =34400 grains/cu. ft. (an empirically determined limiting
capacity constant for the particular resin)
In accordance with the preferred method of the present invention,
the bed of resin particles is regenerated during each regeneration
cycle to a design capacity C.sub.100 which is less than the theoretical
capacity as determined above. The design capacity C.sub.100 is selected
at an exchange capacity of the bed where the salt efficiency (E)
is generally equal to or greater than 2850 where E is approximated
as follows:
where:
C=exchange capacity of the rein bed at a particular salt dosage
in grains
S=salt dosage in lbs.
Referring to FIG. 2 a graph is presented which illustrates for
an exemplary resin bed the exchange capacity of the bed as a function
of the salt dosage. The points along the curve generated in FIG.
2 corresponding to each salt dosage, is approximately equal to
the exchange capacity of the resin bed when the resin bed is exhausted
to one grain hardness and subsequently regenerated with that particular
salt dosage. The preferred method for determining the exchange capacity
of the resin bed for each particular salt dosage will now be described.
The resin bed is first exhausted to one grain hardness by passing
water through the bed until the effluent water exiting from the
bed has a hardness of one grain. The resin bed is then regenerated
with a regenerant brine solution having the selected pounds of salt
(salt dosage). Water of a known hardness is passed through the resin
bed until the effluent water exiting the bed reaches a hardness
of one grain. The quantity of water passing through the resin bed
is measured. The exchange capacity of the resin bed at each selected
salt dosage is then calculated as follows:
where:
C=exchange capacity of resin bed at the particular salt dosage
in grains
G=gallons of water passing through the resin bed
H=hardness of the water passing through the resin bed in grains
The procedure is repeated for various salt dosages to generate
the curve shown in FIG. 2.
As previously discussed, the design capacity of the resin bed C.sub.100
is selected in accordance with the present invention at the point
on the curve wherein the capacity of the resin bed (C) divided by
the salt dosage (S) is generally equal to or greater than 2850.
It has been determined that regenerating the resin bed to this exchange
capacity level efficiently makes use of the volume of salt water
used during each regeneration cycle of the resin bed.
By way of example, the exchange capacities (C) of a one cubic foot
bed of sodium form strong acid cation exchange resin (i.e., Diamond
Shamrock C-20) resin for various salt dosages (S) and the calculated
salt efficiencies (E) is approximated as follows:
______________________________________ S (in lbs.) C (in grains)
E ______________________________________ 1 5500 5500 2 10100
5060 3 14000 4668 4 17300 4316 5 20000 4001 6 22300 3718
7 24200 3463 8 25900 3233 9 27200 3025 10 28400 2838 11
29300 2667 12 30100 2512 13 30800 2371 14 31400 2243 15
31900 2125 16 32300 2018 17 32600 1919 18 32900 1828 19
33100 1744 20 33300 1667 ______________________________________
In accordance with the principles of the present invention, the
design exchange capacity C.sub.100 for the resin bed represented
by the data above, would be approximately 28000 grains. This is
in contrast to a theoretical capacity of the resin bed which is
generally in excess of 34400 grains. Accordingly, as will be further
discussed hereinbelow, the resin bed is regenerated during each
regeneration cycle with a brine solution which has a salt dosage
sufficient to bring the exchange capacity of the resin bed up to
approximately 28000 grains.
In accordance with the present invention the resin bed is regenerated
when, at the end of any preselected time period, i.e. the end of
a day, the percentage of the design capacity of the resin bed used
since the last regeneration cycle exceeds a predetermined percentage
(also herein referred to as the progress to exhaustion). This percentage
in accordance with a preferred embodiment of the invention is approximately
30%. Put another way, at the beginning of each preselected time
period, the available exchange capacity of the resin bed is at least
70% of the design capacity of the bed.
This progress to exhaustion percentage (P) may be determined as
follows: ##EQU1## where: G=volume of water in gallons passing through
the resin bed since the previous regeneration
H=hardness of the water passing through the resin bed in grains
C.sub.100 =design exchange capacity of the resin bed The volume
of water (G) passing through the resin bed may be determined in
many ways well known in the art. An example of such a device is
a water turbine meter 28 located in communication with the outlet
line 18 which measures the volume of water passing through the
outlet line 18. Meter 28 preferably utilizes a magnetic hall-effect
switch circuit to pick up alternative N-S flux reversals as the
turbine turns. The hardness of the water (H) passing through the
bed may be determined by techniques well known in the art. The design
exchange capacity C.sub.100 of the resin bed is determined as discussed
above.
The progress to exhaustion percentage is preferably continuously
calculated by a specifically programmed micro-computer controller
30. The design capacity C.sub.100 is pre-programmed into controller
30 the hardness of the water (H) is programmed into the controller
by the operator, and the gallons used (G) is measured by the meter
28 and continuously fed to the controller 30. At the end of each
preselected time period, the controller 30 initiates a regeneration
cycle if the progress to exhaustion percentage (P) exceeds a preselected
value, i.e. 30.
In accordance with a further feature of the invention, the quantity
of salt used during each regeneration cycle S.sub.D is selected
in accordance with the amount of salt needed to bring the resin
bed back up to its design exchange capacity. Referring to FIG. 2
the design exchange capacity is indicated at C.sub.100 and the salt
dosage to restore the resin bed to attain the C.sub.100 is indicated
at S.sub.100. The available exchange capacity of the resin bed is
indicated at C.sub.A and is determined as follows: ##EQU2## where:
P=percentage of exhaustion (as determined above)
C.sub.100 =design capacity (as determined above)
The exchange capacity of the resin bed used since the last regeneration
cycle is indicated at C.sub.u and is determined as follows:
where:
C.sub.100 =design capacity (as determined above)
C.sub.A =available exchange capacity (as determined above)
The quantity of salt, or salt dosage, used during the regeneration
cycle, as indicated at S.sub.D, is determined as follows:
where:
S.sub.100 =salt quantity to attain C.sub.100 in the resin bed starting
from a 1 grain hardness condition
S.sub.A =salt quantity to attain C.sub.A in the resin bed starting
from a 1 grain hardness condition
The selection of the quantity of salt dosage (S.sub.D) used during
the regeneration cycle, as determined in accordance with the above,
efficiently utilizes the salt to regenerate the resin bed to its
design capacit C.sub.100.
After determining the quantity of salt S.sub.D as discussed above,
the controller 30 controls the fill time of the fill water entering
the brine tank 26 to dissolve a quantity of salt substantially equal
to S.sub.D as determined. The resin bed is then regenerated in a
manner previously discussed to restore the capacity of the resin
bed to its design capacity C.sub.100.
In accordance with the teachings of the invention, as discussed
hereinabove, it is contemplated that the controller 30 may be programmed
to operate in various ways. The controller 30 may be programmed
to initiate a regeneration cycle with one of a plurality of preselected
salt dosages. For example, the control 30 may be programmed to regenerate
with salt dosages of 9 11 13 or 15 lbs of salt. In such instance
the control 30 may be programmed to select the sale dosage which
is either closest to the actual salt dosage necessary to achieve
the design capacity of the resin bed or the highest dosage which
will not exceed the actual salt dosage necessary to achieve the
design capacity of the resin bed. In either case, the salt dosage
selected will regenerate the resin bed to approximately its design
exchange capacity.
The present invention provides an automatic means to account for
and efficiently use the water softener's residual capacity, which
results when the softener is regenerated before complete exhaustion
of the resin bed. The regenerations may be scheduled to start at
24 hour intervals in the case of models intended for single unit
installation and at, for example, 8 hour intervals for models intended
for multi-unit installation. In either case, the micro-computer
controller evaluates the total water usage since the previous regeneration
and determines the quantity of salt to be used to regenerate the
resin bed to its design capacity. In the instance when the micro-computer
controller determines that less than 30 percent of the softener's
design capacity has been used, then no regeneration will occur during
that period. The main benefits of this feature is that it assures
a capacity of 70 to 100 percent at the start of each period and
results in savings of salt and regeneration water consumption.
It should be understood, of course, that the foregoing relates
to only preferred embodiments of the invention and that numerous
modifications or alterations may be made therein without departing
from the spirit and the scope of the invention as set forth in the
appended claims. |