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Morris Sallick Industrial Supplies, Inc. Mechanical, Electrical, Control/Automation & Instrumentation Process Engineering
HUMIDITY & DEWPOINT CONTROL
Packaging – Avoids clogged equipment – Reduces cleaning frequency – Allows fast wrapping with
polypropylene
Pan Coating – Improves surface finish – Speeds water-based drying – Eliminates picking & sticking
Hygroscopic Material Conveying / Storage – Eliminates Clogging and Sticking – Eliminates Product Waste – Improves Product Consistency
Spray Drying/Instantizing – No clogs in product collectors – Allows smaller fluid beds – Increases throughput of towers
Low-Temperature Drying – Improves product quality – Fast drying at low temperature
Enrobers – Eliminates skirting – Eliminates condensation – Improves sanitation
Morris Sallick Industrial Supplies, Inc. Mechanical, Electrical, Control/Automation & Instrumentation Process Engineering
HUMIDITY & DEWPOINT CONTROL
Refrigerated Warehouses – Eliminates fog / condensation – Eliminates slippery floors – Improves worker safety – Prevent mold growth.
Meat Processing – Eliminates condensation dripping onto
product. – Reduces pull down time after wash
down = increased production time. – Improves worker comfort.
Loading Docks – Extends cooler defrost cycle – Reduces labor with no chipping ice
off floors, doors & racks. – Shift latent load to lower cost utility
(natural gas).
Spiral Freezers – Eliminates conveyor defrost – Eliminates floor icing – Reduce ice buildup on evaporator
coils – Improves refrigeration COP – Eliminates ice on downstream
weighing machinery
Morris Sallick Industrial Supplies, Inc. Mechanical, Electrical, Control/Automation & Instrumentation Process Engineering
HUMIDITY & DEWPOINT CONTROL
Air is circulated across a cold coil and cooled to saturation
Further cooling condenses moisture from the air stream
Dew point reduction is limited by minimum practical coil temperatures
Air is delivered at saturated conditions
Morris Sallick Industrial Supplies, Inc. Mechanical, Electrical, Control/Automation & Instrumentation Process Engineering
HUMIDITY & DEWPOINT CONTROL
70°F 56 gr/lb
25 °F 19 gr/lb
FOG FROST
Morris Sallick Industrial Supplies, Inc. Mechanical, Electrical, Control/Automation & Instrumentation Process Engineering
HUMIDITY & DEWPOINT CONTROL Hygroscopic materials don’t stick
together Products flow freely through
conveyers and hoppers Improved product quality with
finished product (no clogging) Eliminates condensation dropping
onto product - hygiene risk Prevents costly shutdowns,
production interruptions and product loss
Return to production quicker – Product clogging often results in
downtime. – DH helps dry cleaned equipment.
Morris Sallick Industrial Supplies, Inc. Mechanical, Electrical, Control/Automation & Instrumentation Process Engineering
HUMIDITY & DEWPOINT CONTROL
Silo Conveying Mixing and blending Drying- fluid bed, spray
tower Coating Cooling tunnels Freezing Storage
Morris Sallick Industrial Supplies, Inc. Mechanical, Electrical, Control/Automation & Instrumentation Process Engineering
HUMIDITY & DEWPOINT CONTROL Storage – Silo
Removes condensation
Prevents mold growth
Stops caking
Dry air
Prevention of clogging
Elimination of condensation
Prevents mold growth
Sizing
•Typically .5 AC/H for the volume of the silo (once through system)
•Once Through System
Morris Sallick Industrial Supplies, Inc. Mechanical, Electrical, Control/Automation & Instrumentation Process Engineering
HUMIDITY & DEWPOINT CONTROL
• As air is compressed and the air volume decreases
• The moisture content of the air remains the same, causing the dew point to shift and increase
• High humidity will be absorbed by product, or can stick to line especially on cold spots.
Desiccant Unit
Filter
Silo
Valve
Vacuum Pump
Mixing Vessel
Pneumatic Conveying
Morris Sallick Industrial Supplies, Inc. Mechanical, Electrical, Control/Automation & Instrumentation Process Engineering
HUMIDITY & DEWPOINT CONTROL Storage
• Reduces waste in storage
• Prevents sticking and lumpy material
• Prevents mold
• Eliminates condensation (ice)
• Prolongs shelf-life and quality
Morris Sallick Industrial Supplies, Inc. Mechanical, Electrical, Control/Automation & Instrumentation Process Engineering
HUMIDITY & DEWPOINT CONTROL 10% RH Room - Typical Schematic
Bypass only at low load
300 cfm leaves the roomthrough cracks and doors
F E
D C A
BDifferentialpressurecontrol
P
G
LocationAirflow( cfm )
Temp( ° F )
Moisture( gr/lb )
A 800 91 147B 3000 70 11C 3800 66 20D 3800 86 4E 3800 86 4F 3800 60 4G 500 70 11
H
F
F
CC
T
C
T
F
C
Room control for humidity and temperature
Face and bypass for tight humidity control
Morris Sallick Industrial Supplies, Inc. Mechanical, Electrical, Control/Automation & Instrumentation Process Engineering
HUMIDITY & DEWPOINT CONTROL Spray Tower Problems
• Production rate varies by season
• Drying time too long
• Inconsistent quality of the powder
• Production stops • Product scrap • Lack of flexibility
Morris Sallick Industrial Supplies, Inc. Mechanical, Electrical, Control/Automation & Instrumentation Process Engineering
HUMIDITY & DEWPOINT CONTROL Spray Dryers, Approach
• Using desiccant technology to dry the outside air required for the process.
• Provide a consistent low dew point.
• Desiccant wheel removes moisture while also heating the process air (energy savings)
Morris Sallick Industrial Supplies, Inc. Mechanical, Electrical, Control/Automation & Instrumentation Process Engineering
HUMIDITY & DEWPOINT CONTROL
Typical Production Losses Related to Moisture in the Air
0
10
20
30
40
50
60
70
80
90
January February March April May June July August September October November December
Hu
mid
ity
Gr/
Lb
-50
-45
-40
-35
-30
-25
-20
-15
-10
-5
0
% lo
st o
f p
rod
uct
ion
Minimum 20% of the production is lost each year
Morris Sallick Industrial Supplies, Inc. Mechanical, Electrical, Control/Automation & Instrumentation Process Engineering
HUMIDITY & DEWPOINT CONTROL
Actual Example of Drying Time Summer vs. Winter
• Batch consists of 4 cycles • Summer cycle 110 min. • Winter cycle 90 min. • Prep is down time between
cycles • Winter batch 20% faster
processing time
0
100
200
300
400
500
600
Summer Winter
DryingPrepTotal
Morris Sallick Industrial Supplies, Inc. Mechanical, Electrical, Control/Automation & Instrumentation Process Engineering
HUMIDITY & DEWPOINT CONTROL
• Production rate varies by season • Drying time to long • Consistant quality of the powder • Non predictable parameters • Production stops • Product scrap • Lack of flexibility
Fluid Bed
Morris Sallick Industrial Supplies, Inc. Mechanical, Electrical, Control/Automation & Instrumentation Process Engineering
HUMIDITY & DEWPOINT CONTROL
Morris Sallick Industrial Supplies, Inc. Mechanical, Electrical, Control/Automation & Instrumentation Process Engineering
HUMIDITY & DEWPOINT CONTROL Typical Process Freezer
(Lower Level)
Suction Side Of Freezer Product Flow
Moisture Leakage
Ice Buildup on Evaporator Coils
Packaging Area (Upper Level)
Product Flow
Packaging Area
Morris Sallick Industrial Supplies, Inc. Mechanical, Electrical, Control/Automation & Instrumentation Process Engineering
HUMIDITY & DEWPOINT CONTROL Design conditions in process freezer applications without dehumidification
Morris Sallick Industrial Supplies, Inc. Mechanical, Electrical, Control/Automation & Instrumentation Process Engineering
HUMIDITY & DEWPOINT CONTROL
Makeup Air System with Tunnels Condition air at
product entrance and exit to remove infiltration load
Morris Sallick Industrial Supplies, Inc. Mechanical, Electrical, Control/Automation & Instrumentation Process Engineering
HUMIDITY & DEWPOINT CONTROL Air System with Vestibule
Condition air at product entrance and exit to remove infiltration load
Morris Sallick Industrial Supplies, Inc. Mechanical, Electrical, Control/Automation & Instrumentation Process Engineering
HUMIDITY & DEWPOINT CONTROL
• Reduction in defrost cycles in freezer
• Reduction in ice on inlets and outlets of conveyors
• More throughput • Coils working more efficiently • Able to stay in production
Morris Sallick Industrial Supplies, Inc. Mechanical, Electrical, Control/Automation & Instrumentation Process Engineering
HUMIDITY & DEWPOINT CONTROL
Freezer Storage Issues
• Ice forms at all openings • To hold 32°F and below
temperatures, coils must supply below freezing temperatures
• Product drying is not allowed • Large infiltration load (doors)
Morris Sallick Industrial Supplies, Inc. Mechanical, Electrical, Control/Automation & Instrumentation Process Engineering
HUMIDITY & DEWPOINT CONTROL
Morris Sallick Industrial Supplies, Inc. Mechanical, Electrical, Control/Automation & Instrumentation Process Engineering
HUMIDITY & DEWPOINT CONTROL Loading Docks
Humidity Issues • Ice Build-up On Freezer Ceiling
and Around Door Frames • Fogging, Wet Floors,
Condensation and Moisture • Mold/Mildew • Energy Management and
Facility Productivity • Worker Comfort & Safety
• Loading dock doors and seals (assuming dock doors remain shut until truck is backed into place)
• Conveyers and open areas underneath loading docks
In these applications the primary source of moisture is a result of infiltration from:
Morris Sallick Industrial Supplies, Inc. Mechanical, Electrical, Control/Automation & Instrumentation Process Engineering
HUMIDITY & DEWPOINT CONTROL Dehumidification System Flow Diagram
Morris Sallick Industrial Supplies, Inc. Mechanical, Electrical, Control/Automation & Instrumentation Process Engineering
HUMIDITY & DEWPOINT CONTROL
Free Flowing Powders
Morris Sallick Industrial Supplies, Inc. Mechanical, Electrical, Control/Automation & Instrumentation Process Engineering
HUMIDITY & DEWPOINT CONTROL
Desiccant enhanced dehumidifier doesn`t need to cool to as low a temperature, so it saves significant energy over conventional systems
Desiccant enhanced dehumidifier
Cooling-Reheat dehumidifiers Require 30% to 40% additional
cooling to achieve same dew point
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