ASHRAE Journal - August 2014 - 83

2014 ASHRAE TEcHnology AwARd cASE STudiES

the production area eliminate possible contaminants due to ventilation.
During production cycles the air
temperature is controlled between
73°F and 77°F (23°C and 25°C),
creating optimal conditions for the
cheese production and workers.
The volume of new (dry) air is a real
benefit to lower the humidity during
the equipment washing cycles. The
humidity is naturally high due to
almost continuous equipment washing so in winter no humidification is
needed.
Due to heat rejection during production, the air supply temperature
even in winter is no more than 79°F
(26°C). Combined with the air distribution required by porous sanitary textile conduits, the workers'
comfort is optimal. Measured air
velocities in working areas are less
than 39.4 fpm (0.2 m/s). In addition
to thermal comfort, this air velocity
provides optimum conditions for
the cheese processing.

Innovation

Treated Fat
Whey
Process Drains
(White Water)

Buffer Tank
Two Days
Retention

~7,925 gallon/Day
(~30 m3/Day)

Buffer Tank
(Underground)

Digester
(Outside)

Dissolved Air
Flotation

Skim Organic
Effluent

Biogas

Fat

Filter
Sludge
Tank

Absorption Fields
~7,661 gallon/Day
(~29 m3/Day)
Buffer Tank
(Underground)

Aerobic
Treatment

Decanter

Fat Treatment
Tank Two
Day Retention
(Outside)
~7,925 gallon/Day
(~30 m3/Day)
Buffer Tank
(Underground)

~264 gallon/Day
(~1 m3/Day)
Periodic
Waste Collection

Figure 1 Cheese factory effluent flows.

Heat Exchanger

~158°F (70°C)
Water Tank
~300 kWh
Accumulation

Process Heating
Building Heating
Makeup Air

~181°F (83°C)
Water Tank
~300 kWh
Accumulation

~89°F (32°C)
Water Tank
~300 kWh
Accumulation

Heating
Oil

~41°F (-5°C)
Glycol Tank
1,000 Gallons

Chiller

"Free"
Heating

Water Boiler Water Boiler
"Free" Heating
Biogas

Outside Dissipation
if T>Tmax

Washing Water
Preheat, Pasteurization
Preheat Makeup Air

Electricity

Air Makeup

Cold Rooms
Brines
Cheese Aging

Figure 2 Cheese factory energy fluxes.

The digester uses a simple head
Existing Pasteurization
New Pasteurization
three-phase separator, ensuring a
Raw Milk
Raw Milk
Raw Milk
Raw Milk
Raw Milk
uniform velocity, which is essential
113°F (45°C)
39°F (4°C)
39°F (4°C)
84°F (29°C)
158°F (70°C)
for digester efficiency and prevent"Free"
Regeneration
Heating 100%
ing bacterial contamination. To
Heating 14%
Pre-Heating 86% Regeneration
have a uniform effluent distribuHot Water Minimum
Temperate
Hot Water Minimum
tion, a 10 in. (254 mm) header is
169°F (76°C)
Water 88°F to 99°F
169°F (76°C)
(31°C to 37°C)
Pasteurized Milk 165°F (74°C)
Pasteurized Milk
Pasteurized Milk
used and a control valve with an
Pasteurized Milk 91°F (33°C)
91°F (33°C)
165°F (74°C)
electromagnetic flow meter will
Figure 3 Pasteurization system before and after modification.
automatically modulate to provide
equal flow on each line.
In addition to energy savings, the modified high-temUsing two buffer tanks for hot water
perature, short-time pasteurizer heat exchanger with
permits two hot water temperatures.
Depending on the temperature of hot water needed, the
three milk passes instead of two (as in the classic solusetpoint is generated and the proper hot water tank is
tion) creates a more stable pasteurization temperature,
chosen automatically. This allows biogas to build to the
essential for cheese quality and taste. The system's connecessary high water temperature when cheese is not
trol improves energy use considerably by predicting the
being produced and hot water isn't needed (especially at
production energy needed and estimating the accumunight), which saves heating oil.
lation needs. Heating oil is used only as the last choice.
Au g ust 2014

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ASHRAE Journal - August 2014

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