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Magnetic Water Treatment is rapidly gaining broad acceptance as
a viable alternative to chemical treatment. Recent scientific studies
have identified the way magnetic fields influence the minerals in
the water and provide a firm basis for the optimal design and operation
of magnetic water treatment equipment. Case studies are cited to
provide specific instances of successful magnetic treatment.
Mr. Ernest J. Florestano is President of Descal-A-Matic Corp., Norfolk,
Virginia, Mr. Joseph M. Marchello is associated with Old Dominion
University, Norfolk, Virginia and Mr. Sanjay M. Bhat is associated
with Ing-Tech Engineering Company, Navi Mumbai.
INTRODUCTION
The water treatment industry is a multi-billion dollar business.
It is growing rapidly in the industrial countries and nearly exponentially
in developing countries. In conjunction with the growth of water
handling systems, there is the corresponding concern for the environmental
consequences of the use of chemical treatment. These factors present
a compelling case for the more extensive use of magnetic water treatment.
Historically, the control of scale and corrosion has been handled
by chemical treatment. However, chemical additives must be administered
in precise quantities that depend on the make-up of the system water.
These methods are costly and give rise to growing environmental
issues. Alternatives to chemical water treatment have been explored
for many years. A number of the proposed alternatives to chemical
water treatment have not stood up to scientific and technical analyses.
An exception is magnetic water treatment for which researchers have
recently identified the scientific explanation. Consequently, increased
attention is being focused on applications for magnetic water treatment
(1).
For both chemical and magnetic water treatment, water economy is
achieved by increasing the cycles of concentration. This entails
reducing the amount of water bleed-off which correspondingly reduce
make-up. The consequences of high-water recycle with chemical additive
treatment are a build-up of chemicals and minerals in the circulating
water. With magnetic treatment, there is only the mineral content,
i.e., TDS (Total Dissolved Solids) that builds up in the water.
Therefore, magnetic water treatment permits much higher cycles of
concentration.
MAGNETIC WATER TECHNOLOGY
A number of magnetic water treatment devices are available. Most
of the devices are "in-line" units, wherein the system
water flows directly through the magnetic force fields. Other devices
are "clamped-on" to the outside of pipes. Figure 1 presents
schematics of the various designs of devices that are used for magnetic
water treatment. Manufacturers maintain proprietary control over
their equipment design, however some patent information is available
(2). Case studies on the use of magnetic water treatment are presented
later to provide information about magnetic treatment applications.
The scientific explanation of magnetic water treatment has been
the subject of investigation by British, Russian and American researchers
(3). These studies involved the formation of scale and the methods
for its prevention. The immediate cause of scale formation is the
deposition of a precipitate from a super-saturated solution. The
main factors that give rise to supersaturation are concentration
of the solution, temperature, pressure and pH. When these parameters
reach limiting values, or combination of values, the dissolved minerals
nucleate and form crystals, which can occur as water suspended particles
or as surface scale (4). Magnetic fields have been found to change
particle size and crystallinity type (5).
Preventing mineral scale formation entails controlling solubility,
nucleation and crystal growth. This can be achieved with chemical
or physical changes. For example, as temperature increases, dissolved
CaCO3 precipitates as calcite, on heat transfer surfaces. Chemical
water treatment adds chemicals that serve to increase CaCO3 solubility
and thereby retard its precipitation as calcite scale. Magnetic
Water Treatment alters the CaCO3 crystalline form from calcite to
aragonite, a small soft crystal. The aragonite precipitates as suspended
particles in the water rather than on the heat transfer surfaces.
In magnetic water treatment, the suspended solids are removed by
filtration. In addition, the continuous magnetic treatment maintains
the CaCO3 in suspension.
The aragonite is a meta-stable crystalline form of CaCO3(4),(5).
It transforms into the more stable calcite with a half life of about
24 hours. When the pH exceeds 9, the crystalline transformation
occurs more rapidly and may be complete within one hour. For boilers
with operating pressure in excess of 200 psi and temperatures of
382oF, the magnetic treatment has not been successful. This is probably
because the aragonite is either not formed or decomposes rapidly
under those conditions. This is an area where more research is needed.
Other water minerals also are affected by the magnetic treatment.
CaSO4 shows similar crystal nucleation behaviour to CaCO3. The magnetic
field increases the solubility of other minerals, notably phosphates
(6). The presence of iron inhibits the crystallization of calcite
and favors the formation of aragonite (7).
Laboratory studies report that magnetic treatment reduces oxygen
saturation levels in water which correspondingly reduces corrosion
(8). The National Aeronautics and Space Administration (NASA) tested
magnetically treated water against chemically treated water for
corrosion rates of steel. Four mils per year is considered acceptable
by the industry. NASA found one to fifty mils per year using chemical
inhibitors. Rates were below the measureable level, 0.1 mils per
year with magnetic treatment (9).
A complete magnetic water management system often includes other
non-chemical components to complete the water treatment process.
Typically, these include biocide controls, such as Copper-Silver
devices and solids separation devices, of which a Spin-Down Sediment
Filter is a low cost example. Magnetic water treatment has found
successful applications in cooling tower systems, boiler feedwater
treatment and in the textile and pharmaceutical manufacturing industries
(10). Some investigators have even reported beneficial uses for
magnetic water treatment in agricultural applications (11).
SYSTEM DESIGN AND OPERATION
The interaction of the minerals in the water is complex and requires
a careful analysis of each water management system. Vendors of magnetic
water treatment have developed experience based information to guide
in the tailoring of the application of their equipment.
The first step in properly designing a Magnetic Water Treatment
System is obtaining the following information from a prospective
user:
1) Water system flow schematic.
2) Water analysis of supply water.
a) Total hardness as CaCO3 (in grains, ppm or mg/l)
b) pH
c) Iron content (in ppm or mg/l)
d) Silica content (SiO2)
e) TDS (Total Dissolved Solids).
3) Is the system recirculating or straight-through? If straight-through,
what is the maximum flow rate in gpm (gallons per minute)?
4) For a cooling system:
a) What is the total volume of water in the system in gallons?
b) What is the circulating rate of the system water in gpm (gallons
per minute)?
c) What is the rated tonnage of the cooling system?
d) Is there an existing algae or micro-organism condition in the
system?
5) For a boiler system:
a) What is the maximum output of the boiler feedwater pump in gpm?
b) What is the maximum boiler operating pressure in psi (pounds
per square inch)?
c) What is the horsepower rating of the boiler or the pounds per
hour evaporated
d) Is it a "fire-tube" or a "water-tube" boiler?
e) What is the certified internal condition of the boiler before
the installation of the magnetic water treatment device? A photograph
of the boiler tubes on their water side is the best record of the
condition.
Magnetic treatment of water required that the equipment be designed
to achieve optimal flow residency, time and turbulence. The magnetic
pole orientation and field strength are critical factors in accomplishing
satisfactory performance. Design should provide for the close proximity
of the water to the magnetic influence. A typical flow pattern through
the magnetic fields is shown in Fig. 2. An additional equipment
design concern is containment of the magnetic force fields within
the equipment. This is accomplished by the use of a carbon steel
housing.
Cooling water systems are either re-circulating or straight-through.
For the once-through system, 100% of the flow rate must be treated.
With re-circulating systems, the opportunity to increase cycles
of concentration via magnetic water treatment offers cost savings.
Descal-A-Matic design guidelines provide for treating the total
volume of the recirculating system's water every 60 minutes.
Suppliers of magnetic water treatment equipment take several approaches
to the method of installing and operating their systems. For example,
with cooling tower system, some use 100% in-line treatment of circulating
water. Descal-A-Matic uses the flow-by-pass arrangement, which treats
only a portion of the system water, thereby reducing the size of
the Magnetic Treatment equipment.
Boilers and steam generator equipment can also be re-circulating
or straight-through systems. Equipment sizing for once-through systems
is for 100% of the boiler feedwater pump capacity. For closed-loop
re-circulating systems, only a portion of the system re-circulating
water needs to be treated.
The American Boiler Manufacturers' Association recommends that for
chemical water treatment in boilers, the pH should be adjusted to
between 9 and 11. With magnetic treatment, the pH adjusts automatically
to within this range. The half-life of aragonite is reduced when
the pH exceeds 9. For this reason, special operating procedures
are utilized for boiler water treatment.
Maintenance and inspection practices of magnetic equipment vary
with the different suppliers. Some claim that no maintenance is
required. Other manufacturers specify that semi-annual inspection
and cleaning of the magnetic equipment is required. Experiences
with Descal-A-Matic equipment have been that their systems are very
forgiving and can go for extended periods of operation without attention.
Even so, Descal-A-Matic recommends semi-annual inspections of their
equipment.
CASE STUDIES
Applications of magnetic water treatment is growing rapidly worldwide.
The information provided in the following case studies serves to
illustrate the range of applicability and the experience being gained
by users of Descal-A-Matic systems.
CASE 1 : WEST COAST FERTILIZER PLANT
J.R. Simplot Company is a fertilizer manufacturer in the Central
Valley of California. In July of 1992 the plant chemical engineer
ordered a Descal-A-Matic system for the 400 ton cooling tower on
his ammonia production process. The engineer also presented a challenge
that he would do everything possible to confront the equipment with
a variety of extreme conditions in order to prove or disprove its
effectiveness. After over seven months of running a zero bleed-off
and reaching over 38 cycles of concentration with high temperature
heaters immersed in the tower water, the condenser was opened to
reveal no scale build-up on the heat transfer surfaces.
CASE 2 : MANUFACTURER OF STERILIZER EQUIPMENT
The following summarizes the field test results on the Descal-A-Matic
Magnetic Water conditioner.
Test Site: Platte Community Hospital - Platte, SD
Generator: 75KW Chromalox 208V, S/N 13953, W/Auto Flush & Drain
Duty Cycle: On 6am to 6pm, 7 days per week
Flush Cycle: Daily upon start up - 3 minutes
Water pH - 8.04
Analysis akl - 160 ppm
hardness - 310 ppm
total solids - 392 ppm.
Platte Community Hospital site was chosen because of the high number
of heater failure replacements due to scale build-up. Their maintenance
department had determined this generator could run for a maximum
time of only three weeks before it was necessary to shut down and
perform a complete strip down and descaling maintenance procedure.
The initial base line test was started on 10/11/93 and the generator
was run for three weeks. Scale built up on the heaters and bridged
across the elements at the flange. The magnetic treatment was installed
and a series of tests were run to determine the maximum time needed
for the same scale build-up as in the three week base line test.
On 9/20/94 the final test was concluded and results using the magnetic
treatment indicated 16 weeks were needed to accumulate the same
amount of scale. The magnetic treatment was then disassembled after
approximately one year in operation. There was minor scale film
on the inlet and outlet side walls of the pipe and to scale on the
internal magnetic tube assembly.
Based upon the great reduction in scale deposition found in the
field test, Platte Community Hospital was able to decrease the maintenance
costs on the generator. Savings were realized in labor and materials.
They also were able to reduce the environmental impact by using
and disposing of less acid descaler. In high TDs areas, it is important
that daily flush or blow down be used on any steam generator to
remove dissolved solids (scale).
CASE 3 : U.S. CATHOLIC CONFERENCE CENTER - WASHINGTON, D.C.
The Descal-A-Matic system, installed since May 1991, has preformed
very well. U.S. Catholic Conference Center installed a unit on its
cooling tower and one installed on its hot water loop. In the first
year they noticed a drop in water usage by about one-third. The
maintenance required is minimal, with only annual cleaning of the
magnetic unit needed. Their corrosion analyst reports show that
corrosion is less than one mil per year. They have an Ice Thermal
Storage System which required the chillers to run extremely hard.
The approach temperature cannot be more than 3 degrees off or else
the chillers will surge. The magnetic unit has done an excellent
job in keeping scale off the tubes. The copper-silver unit has preformed
well with water tests showing no bacteria growth.
REFERENCES
1) Geary, David, TC 3.6, ASHRAE '95 Winter Meeting, Pages 18 &
36, ASHRAE Journal, April 1995.
2) Lindler, Carl, Inventor, Descal-A-Matic Corporation, Assignee;
U.S. Patent No. 4366053, Dec. 28, 1982 and U.S. Patent No. 4505815,
Mar. 19, 1985.
3) Grutsch, J.F., McClintock, J.W., 1984 International Corrosion
Forum, NACE, Paper No. 330, New Orleans, April 1984.
4) Donaldson, J.D., Tube International, Pages 39-49, Jan. 1988.
5) Grimes, S.M., Tube International, Pages 111-118, March 1988.
6) Boichenko, V.A. and Sapogin, L.G., Inzhenerno-Fizicheskii Journal,
Vol. 33, No. 2, Page 350, 1977.
7) Katz, J.L. Reich, Herzog, R.E. & Paarsiegla, K.I., Langmuir,
Vol. 9, No. 5, Pages 1423-1430, 1993.
8) Reimers, R.S., Anderson, A.C. & White, L.E., Applied Fields.
9) Kuivenen, David E., "Comparing corrosion rates of steel
corrosion coupons in magnetically treated water and in a water system
utilizing corrosion inhibitors," National Aeronautics and Space
Administration, Lewis Research Center, Cleveland, 1975.
10) MacGarva, C.J., Coast Guard Engineers' Digest, Pages 29-36
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