Recycled Water for Cooling Molten Glass
Marcus N. Allhands
Tom Broderick
ABSTRACT
Using recycled water for cooling molds and vacuum pumps in a Kentucky glass factory was tried
and failed. So, municipal water was used once again as a cool heat sink at a hot price -- $10,000
a month hot. After investigating new recycle options, a new water treatment system was
installed in the fall of 2006 resulting in a full payback in just 33 days. Nearly 10% of the world’s
incandescent light bulbs are blown in this facility utilizing 1–2.5 MGD of recycled water
contributing to the conservation of valuable potable water. This manuscript tells how this was
done along with the benefits and hazards.
INTRODUCTION
It is very likely that a majority of incandescent light bulbs in your home or office came from the
Philips Lighting plant in Danville, Kentucky shown in Figure 1. In addition to bulbs for
incandescent lights, this plant make borosilicate hard glass for spotlight lenses and reflectors, and
lead glass parts used in the manufacture of fluorescent tubes. Whether incandescent or
fluorescent, glass will continue to be a major component in the lighting business in the
foreseeable future.
PROBLEM
Very hot molten materials must be cooled at very precise rates throughout the glass-making
process. Enormous amounts of water are needed to carry out this temperature control. Years
ago this facility tried to reuse cooling water from ponds in vacuum pumps, heat exchangers,
furnace jackets and instrumentation but suspended solids caused numerous problems. Material
deposited on heat transfer surfaces interfered with the control of cooling rates. Heat exchangers
and vacuum pumps would plug, cooling jackets would clog with debris and instruments used to
detect the level of molten glass within furnaces would overheat when cooling water lines choked
off. Production decreased, wastage increased and costly labor ran rampant. Even the frequency
of maintenance shut-downs increased. Since suspended solid concentrations would vary due to
climatic, environmental and seasonal changes, quality control proved impossible. The expedient
answer was to simply use potable water for one-pass cooling. Water was then held in retention
ponds shown in Figure 2 and discharged to a local stream according to the conditions of their
NPDES permit. Purchased water consumption immediately doubled. Nearly a quarter of a
million dollars a year was now being spent on total water usage. Cooling water alone was
costing $10,000 per month causing a big increase in direct operating costs.
SOLUTION
The facility maintenance manager thought there should be a practical way to reuse cooling water.
He read of a new automatic self-cleaning screen filter released in 2006 and decided to
investigate. He found that the technology was well proven but the flow capacity and
configuration were new. After site visits by the manufacturer’s vice president (a registered
engineer), a corporate decision was made to install the new filters. Two ORIVAL Model ORG060-LS filters with 6 inch inlet and outlet flanges were installed in parallel to handle the 1100
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gpm average flow rate. Figure 3 shows the actual installation. Water could now be recycled
numerous times through the plant.
DISCUSSION
Though the pump house seemed large (Figure 4), open space had to he maintained to allow
forklifts to enter and pull the two existing vertical turbine pumps for periodic maintenance.
Therefore, media tanks would take up too much room. Each filter is equipped with over 466
square inches of effective screen area. The filtration system controller uses either a signal from a
pressure differential switch reaching a threshold across the inlet and outlet piping or the
termination of an internal timer to initiate a cleaning cycle. The automation and reliability
provided by this technology has pleased the maintenance department. The entire cleaning cycle
takes about 30 seconds. Each filter has a 1½ inch rinse valve designed to conserve water by
minimizing the volume used during each cleaning cycle. The control timer is set to initiate a
cleaning cycle every three hours. The time function initiates most cleaning cycles since the
differential pressure threshold of 7 psi is seldom reached in three hours.
The initial filtration degree of the installed screens was 200 microns or about twice the diameter
of a typical human hair. Two subsequent problems occurred following the filtration system
installation. First, a chronic oil leak from a specialized piece of equipment in the glass making
process began flowing into the floor drains leading into the retention ponds. This equipment was
installed in such a way that the leak could not be accessed until a scheduled shut-down occurred.
The furnaces must be kept full of molten glass at all times as withdraws are compensated for by
new raw materials. An unscheduled shut-down would produce tons of solidified glass
throughout the furnaces, flumes and machines. This oil was emulsified in the retention ponds so
no free oil could be skimmed from the system. The second problem occurred when the
emulsified oil mixed with a fine powdery colloidal material used occasionally in the glass
making process. The oil and colloids passed through the screens and began gumming up pipes
and instrumentation within the plant. To prevent shut-down conditions, cooling water was once
more switched back to municipal supplies. The filter manufacture supplied 50-micron screens to
attempt the removal of the finer particles. Eventually the oil leak was fixed and the emulsified
oil in the retention ponds dissipated. The system went back onto filtered reuse water with no
further mishaps. Payback for the filtration system was a mere thirty-three days.
SUMMARY
By reusing water, precise product temperature control is maintained, heat exchangers and
vacuum pumps are kept free-flowing and instrumentation remains reliable without depending
upon potable water supplies. An automatic self-cleaning screen filtration system makes this
possible. Even in the resource-rich United States, water is becoming a precious commodity.
Proactive companies like Philips Glass are looking for ways to minimize potable water and are
therefore reusing water to the maximum extent possible. By reusing 1.6 million gallons of water
each day, potable water is made available for 4000 additional households in this Kentucky
community.
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APPENDIX
How the ORG Filter Works
Dirty water enters the inlet (1) shown in Figure 5, where it goes into the center of the fine screen
(2). The water then passes through the fine screen from the inside out and exits the outlet (3).
The unwanted solids accumulate on the inner surface of the fine screen, creating a pressure
differential. Once the pressure drop reaches a preset level, a rinse cycle is activated by the
factory supplied control system by opening the rinse valve (4) to an atmospheric drain. As a
result, pressure drops in the hydraulic motor chamber (5) and dirt collector assembly (6). The
pressure drop creates a backflush stream at the nozzle openings which are very close to the inner
screen surface; this low pressure area sucks the dirt off the screen, similar to a vacuum cleaner.
The backwash water is carried through the collector and ejected out of the holes in the hydraulic
motor (7). The water being ejected out of the hydraulic motor causes the collector to rotate,
similar to a lawn sprinkler. In addition, pressure released from the hydraulic piston (8) causes
the collector assembly to slowly move upward. This combination of rotational and linear
movements ensures that the entire screen area is cleaned each cycle. The cleaning cycle of the
ORG-015-LE and ORG-020-LE takes less than 10 seconds while the larger filter models take a
few seconds more to clean.
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Figure 1. Philips Glass facility in Danville, KY.
Figure 2. One of two retention ponds.
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Figure 3. Two ORIVAL Model ORG-060-LS filters.
Figure 4. Pump house.
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Figure 5. Transparent view of ORG filter.
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AUTHORS
Dr. Marcus N. Allhands, PE
Vice President of Business Development
Orival, Inc.
213 S. Van Brunt Street
Englewood, NJ 07631
(551) 206-8526 cellular
(765) 987-7843 fax
ma@orival.com
Tom Broderick
Maintenance Manager
Philips Lighting Company
320 Vaksdahl Avenue
Danville, KY 40422
(859) 238-9218 office
(859) 238-9290 fax
tom.broderick@philips.com
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