Econo-Flow Coolers
A Multi-Stage, Fluid Bed Counterflow Cooler for the Efficient Cooling and Heat Recuperation of Free-Flowing Materials
Custom-Engineered
Specifications:
The Econo-Flow Cooler is customer designed and manufactured to meet a host of material cooling requirements. Specifically,
the Econo-Flow Cooler is designed to air-cool granules, pellets, powders, prills and other free-flowing materials
in particle sizes up to 1/4 inch diameter utilizing a high-efficiency counterflow operation. Each compact unit cools
material to within 20°F of inlet gas temperature. Gas exit temperature is within 30°F of material inlet temperature.
The Econo-Flow Cooler extracts more BTUs from material for a given quantity of air in one fifth the time of a
rotary drum cooler with installation at less than half the price. This results in less dust loss and permits the
use of compact collection equipment. Because the Buell cooler occupies less than 20% of the space required for an
equivalent rotary cooler, it is an ideal solution as an addition to congested plot plans.
Simplicity of design and lack of moving parts permits construction of the cooler shell and tray from any material
required by the process. Lack of contact between the shell and the material permits the use of protective epoxy
paints on internal surfaces to prevent corrosion. The cooler casing is vertical and can be square or round, self-supporting
or hung.
Field Proven, High Efficiency Operation:
For systems operating on ambient air, air is introduced peripherally at the bottom of the cooler and withdrawn at
the top through a gas outlet duct located above the material inlet and distribution cone. Hot exhaust gases then
pass through a collector(s), a fan and then vents to the atmosphere.
Material to be cooled is introduced into the material distribution system at the top of the cooler. The distribution
system conforms to the feeding arrangement preceding the cooler. In most instances, the spreader airlock arrangement
consists of a funnel shaped inlet piece discharging into a vertical pipe. Carefully engineered proportions assure
that the feed acts as a material curtain to block off ambient air leakage. The material falling down the pipe impinges
on a perforated distribution cone that spreads material across the cooler. The distribution system requires no adjustment
for variable feed rates or material changes.
Material retention time is obtained by the formation of dense phase fluidized beds measuring three to six inches
in depth on a series of perforated plates.
Extra Capacity:
The cooler is sized for optimum efficiency at a specified feed rate. Increasing retention time by changing trays
or the number of trays and by accelerating fan horsepower provides added cooling or higher feed rates.
Design & Performance Features:
In addition to space saving economy, the Econo-Flow Cooler offers these outstanding design and performance characteristics:
- Simple Operation - no moving parts except for a fan handling clean air
- No Product Degradation - material is cooled by being gently lowered on a cushion of air through a fluid-bed
tray, utilizing controlled velocities
- Instant Product Changeover - air action provides material retention. Dampering or turning off the fan
assures immediate and complete discharge of all material
- Dust-Free, Clean Air - controlled air flow and material distribution assure good cleaning action and
removal of particles below the air flow space rate designed for the cooler
- High-Efficiency, Counterflow Operation - product and exit gas temperatures are established by the number
of stages incorporated in the cooler
- Low Power Consumption - the Econo-Flow Cooler eliminates the need for an additional motor with speed
reducer which amounts to 20-50% of fan horsepower
- Flexible Layout - fan and collector can be connected directly or located to suit plant layout. No elaborate
or detailed foundations required. System operates on positive pressure where treated air or gases are required
by process
For more information on the operation of this unit, please review the attached technical paper:
Buell Multi-Stage Fluid Bed Cooler
I. Operating Principles
The Buell Multi-Stage Fluid Bed Cooler is designed to air cool granules, pellets, prills and other relatively
free-flowing materials up to ¼" in diameter from elevated temperatures down to as low as 30 above ambient temperature.
The simple design and operating principles are demonstrated below by the illustration and drawing.
The cooler consists of a vertical outer shell, normally square (1). Air is introduced at the bottom (2) peripherally
for systems operating on ambient air and withdrawn at the top through a gas outlet duct (3) located above the material
inlet and distribution cone (4). The hot exhaust gases are then passed through a collector or collectors (5), a
fan (6) and then released to the atmosphere.
For systems employing cooled, pretreated gases, the cooler can be operated under positive pressure. In this case,
the hopper is bolted to the cooler shell and the pretreated cooling gas is blown into the hopper under pressure.
The cooled product is withdrawn through a suitable airlock.
Material to be cooled is introduced at the top through a material distribution system built into the cooler.
The distribution system is tailored to the feeding arrangement preceding the cooler. In most instances, the spreader
airlock arrangement consists of a funnel-shaped inlet piece (7) discharging into a vertical pipe (8). The proportions
are carefully engineered to assure that the feed acts as a material curtain to block off ambient air inleakage,
since the negative pressure in the cooler is 6" to 9" W.G. at the feed inlet point. The material falling down the
pipe (8) is made to impinge on a perforated distribution cone (9) which spreads the material across the cooler.
The distribution system requires no adjustment for variable feed rates or material changes.
Material retention time is obtained by the horizontal perforated trays (10) by preventing the material from flowing
directly through the perforations due to the high gas velocity. The only way a particle can pass through the plate
apertures is to sneak by the apertures' periphery, (10) where air velocities will be low due to the contraction
of the gases by the vena contracta phenomenon. If the flow rate through a particular aperture is too low to accommodate
all the particles presenting themselves to it, the material buildup will block the air flow temporarily and divert
it to another aperture. As soon as the air flow stops, the aperture, which is large enough to accommodate great
material flow rates, releases the temporarily-retained particles and the cycle is started over again.
The material buildup above the holes is fluidized by the air passing through the hole. The material bed depth
above the perforated tray is normally between 3" to 6" dense phase and 18" turbulent phase. Everything else being
equal, the bed depth increases as the feed rate increases so that the cooler efficiency increases with the feed
rate.
Power requirements are extremely low as the floating velocities employed are low and the material never forms
a dense layer of particles through which the air is forced to channel at high speed. As each particle is enveloped
by a highly turbulent stream of air, there is maximum possible transfer of heat from the particles to the surrounding
air stream. This greatly reduces the retention time required to cool the particles while attaining high heat transfer
efficiencies.
2. Equipment Advantages
2.1 Small Space Requirement
The floor space occupied by the Buell Multi-Stage Cooler is approximately 10% to 20% of the space required for
an equivalent rotary cooler. Installed costs average 10% to 50% of comparable rotary cooler.
2.2 Simple Operation
The only moving piece of equipment is a fan handling cleaned air. There is nothing to adjust for varying feed
rates or granular process changes within the stated cooling capacity of the unit.
2.3 Instant Product Changeover
Material retention in the cooler is obtained by air action only. Dampering or turning off the fan assures
complete discharge of all material instantly - eliminates contamination between grades with cooler runout time required
by equivalent rotary units. In the event of power failure, hygroscopic material is discharged immediately, eliminating
costly down time due to material setting in the equipment.
2.4 High Efficiency Counterflow Operation
Product and exit gas temperatures are established by the number of cooling stages incorporated in the cooler.
Three cooler stages in a standard granular fertilizer application are sufficient to bringing the product outlet
temperature within 30F of ambient and the air outlet temperature to 30F of the material inlet temperature. The Buell
Multi-Stage Cooler can extract more BTUs from the material for a given quantity of air in one-fifth the time than
its rotary counterpart. This results in small collection equipment and lower dust losses.
2.5 Lower Power Consumption
The fan horsepower requirements for a conventional cooler and the Buell Multi-Stage Cooler are approximately
identical; however, the rotary cooler has an additional motor with a speed reduced to rotate the cooler shell. The
shell drive power requirement is between 20% and 50% of the fan horsepower.
2.6 Low Maintenance
The cooler shell and trays can be manufactured from any material required by the process. Lack of contact between
the shell and material permits the use of protective paints on internal surfaces to control erosion.
2.7 No Product Degradation
Particles float on air. Three is no mechanical action to break up or grind down the product.
2.8 Dust-free, Clean Product
Controlled air flow and material distribution assure good cleaning action and removal of particles below the
air flow space rate designed for the cooler.
2.9 Flexible Layout
Cooler casing can be square or round, self-supporting or hung. The fan and collector can be directly connected
or located to suit plant layout; no fancy foundations are required. Feed inlet is made to accommodate gravity chutes,
screens, pneumatic conveying lines, etc. The system can operate on positive pressure where treated air or gases
are required by the process.
2.10 Extra Capacity
The cooler is sized for optimum efficiency at a specified feed rate. Increased cooling or higher feed rates can
be accommodated by increasing retention time, by changing trays or the number of trays and increasing the fan rpm.