United States
Environmental Protection
Agency
Office of Air Quality
Planning and Standards
Research Triangle Park NC 27711
EPA-453/R-94-049
July 1994
Air
5-EPA OIL SUPPRESSION OF
PARTICULATE MATTER AT
GRAIN ELEVATORS
control
technology center
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EPA-453/R-94-049
Oil Suppression of Participate Matter
at Grain Elevators
CONTROL TECHNOLOGY CENTER
Sponsored by
Emission Standards Division
Office of Air Quality Planning and Standards
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
Air and Energy Engineering Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
July 1994
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DISCLAIMER
This report has been reviewed by the Control Technology Center (CTC) established by
the Office of Research and Development (ORD) and Office of Air Quality Planning and
Standards (OAQPS) of the U.S. Environmental Protection Agency (EPA), and has been approved
for publication. Approval does not signify that the comments necessarily reflect the views and
policies of the EPA, nor does mention of trade names, organization names, or commercial
products constitute endorsement or recommendation for use.
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TABLE OF CONTENTS
Item Page
List of Tables iv
List of Figures iv
Preface v
Executive Summary vi
Chapter 1 - Grain Elevator Operations and Emissions 1-1
Chapter 2 - Oil Suppression System 2-1
Chapter 3 - Oil Suppression System - Tests 3-1
Chapter 4 - Conventional Controls 4-1
Chapter 5 - Control Technology Costs 5-1
Chapter 6 - Conclusions 6-1
References R-l
Appendix A - Dust Reduction for Different Grains Treated with Different Oils A-l
Appendix B - Control Technology Costs Provided by Vendors B-l
111
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LIST OF TABLES
Tables Page
2-1 Recommended Application Rates of Mineral Oil & Soybean Oil
to Various Grains 2-2
3-1 Percentage Reduction in Dust Concentration 3-5
5-1 Operating Characteristics and Investment Cost of Model Elevators 5-5
5-2 Simulation Results - Conventional Dust Control 5-5
5-3 Simulation Results - Oil Application Systems 5-6
5-4 Difference in Cost for Controls 5-6
5-5 Midwest Elevator Company Cost Analysis 5-8
LIST OF FIGURES
Figures Page
1-1 Schematic of a Traditional Country Elevator 1-3
2-1 Nozzle Assembly in Receiving Pit: Alternative 1 2-3
2-2 Nozzle Assembly in Receiving Pit: Alternative 2 2-3
2-3 Nozzle Assembly in Conveyor System 2-4
2-4 Typical Oil Suppression System 2-5
3-1 Test Facilities of Grain Handling Systems for Additive Study 3-2
3-2 Liquid Additive Spraying System 3-4
IV
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PREFACE
The Control Technology Center (CTC) was established by EPA's Office of Research and
Development (ORD) and Office of Air Quality Planning and Standards (OAQPS) to provide
technical assistance to State and local air pollution control agencies. Several levels of assistance
are provided by the CTC. First, a CTC Hotline is available to provide telephone assistance on
matters relating to air pollution control technologies. Second, more in-depth engineering
assistance is provided when appropriate. Third, the CTC can provide technical guidance by
designing technical guidance documents, developing personal computer software, and presenting
workshops on control technology matters. The CTC is also the focal point of the Federal Small
Business Assistance Program (SBAP), and maintains the Reasonably Available Control
Technology/Best Available Control Technology/Lowest Achievable Emission Rate
(RACT/BACT/LAER) Clearinghouse and International Technology Transfer Center for Global
Greenhouse Gases (ll'lCGGG). Information concerning all CTC products and services can be
accessed through the CTC Bulletin Board System (BBS), which is part of the OAQPS
Technology Transfer Network (TTN) bulletin board system.
This report was prepared to evaluate the effectiveness of oil to suppress paniculate matter
(PM) emissions from grain elevators; it was not intended for use in developing AP-42 emission
factors. The CTC undertook this effort to provide technical assistance to the Nebraska
Department of Environmental Quality (NE DEQ) in its efforts to assess the viability of oil
suppression technologies. The scope of the project was limited to a presentation of findings
based on a review of existing literature concerning oil suppression technologies and conventional
controls for grain elevators. The cancellation of proposed tests to evaluate the effectiveness of
oil to suppress PM emissions prevented the inclusion of current test data demonstrating reduction
efficiencies. Based on findings obtained in literature concerning efficiency and economic and
safety factors, oil suppression appears to be a promising technology for the grain handling
industry. However, EPA has concluded that existing literature and test results do not adequately
document the performance of oil suppressant technology. The CTC, the Federal SBAP, EPA's
Technical Support Division, the Nebraska DEQ and SBAP, and the Feed and Grain Association
are exploring and planning new tests to more accurately determine the performance of oil
suppression. A CTC report on the results of these tests is expected in early 1995.
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EXECUTIVE SUMMARY
The new operating permit program developed pursuant to Title V of the Clean Air Act
Amendments (CAAA) of 1990 will require grain elevator owners to pay fees based on the
amount of paniculate matter emissions generated. Many grain elevators in Nebraska currently
are operated without controls, but the new CAAA requirement is prompting many elevator
operators to evaluate existing control technologies. The devices conventionally used to control
dust emissions from elevators are fabric filters and cyclones. The high cost of these devices,
however, has generated interest in the use of oil additives to suppress dust, especially in small
elevators. The Nebraska Department of Environmental Quality (NE DEQ) has asked the Control
Technology Center (CTC) in the Emission Standards Division of the United States Environmental
Protection Agency (U.S. EPA) to assist in the evaluation of the oil suppression technology.
Grain elevators act as intermediate storage and transfer points for grain as it is transported
from the farms to the market. The operations performed at elevators, including receiving,
handling and transfer, drying, loading and shipping, generate emissions of paniculate matter (PM)
in the form of grain dust, which is the pollutant of concern at elevators. The basic oil
suppression system applies a fine spray of edible oil (either mineral or vegetable) to the grain
stream to coat the grain surface. The dust adheres to the oil on the grain, thereby decreasing the
amount of airborne dust within the elevator.
This report evaluates oil suppression systems and compares their cost and effectiveness
to those of the existing conventional controls used by elevators, specifically fabric filters and
cyclones. This analysis demonstrated that the oil suppression system may effectively reduce
paniculate matter emissions in grain elevators and at a much lower cost than conventional
controls. The major deterrent regarding use of an oil suppression system is the response of grain
exporters and the market to oil-treated grain. Since many grain users in the industry are unsure
about the effect of oil on the quality of the grain, exporters are hesitant to purchase such grain,
even though studies have shown that the oil produces no significant effects. Despite this
attitudinal impediment, oil suppression systems appear to be an attractive and feasible alternative
to conventional control devices.
Additional testing is required to determine the actual effectiveness of oil suppression
systems. The CTC, Federal SBAP, and other EPA programs are working with the NE DEQ and
Feed and Grain Association to explore and plan new testing in the fall of 1994. A new or
revised report will be issued by the CTC once these tests are complete and the results evaluated.
VI
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CHAPTER 1
GRAIN ELEVATOR OPERATIONS AND EMISSIONS
A. INTRODUCTION
Grain elevators produce paniculate emissions (PM) in the form of dust. Conventional
methods of emissions control at grain elevators include fabric filters, cyclones, and dust
recirculation. Although such methods are usually highly effective in reducing dust emissions to
the atmosphere, they generally are expensive.
Since the initial investment for oil suppression is significantly less than for conventional
control methods, oil suppression is being considered as an alternative means of dust control.
The Nebraska Department of Environmental Quality (NE DEQ) has requested EPA's
Control Technology Center's (CTC's) assistance hi evaluating oil suppression control technology
for grain elevators. Many grain elevators are not controlled in Nebraska, but the operating permit
fee schedule (under Title 40, Code of Federal Regulations, Part 70), which is based on amount
of emissions, is prompting many operators to consider controls. The suppression system is
believed to be more cost effective and better suited for retrofit than more conventional control
systems, especially for small country elevators. The NE DEQ needs to know more about the
effectiveness of this control system.
To assist the NE DEQ, the CTC undertook a project to review available literature on this
control technology, prepare a description of the oil suppression control system (including cost
information), and prepare a report evaluating the effectiveness of the system. This report
documents the CTC's project findings. This report also was to include an evaluation of new
emission test data to be provided by others. These tests were not performed. The CTC and
Federal SBAP are pursuing additional testing so that the effectiveness of this promising
technology can be determined more accurately.
B. INDUSTRY OVERVIEW
The grain handling and processing industry transfers grain (including wheat, corn,
soybean, and rice) from farms to mills and plants where the grain is used to produce various
commodities, such as flour, starch, oil, and animal feed. Grain elevators act as intermediate
storage and transfer points for the grain between the farms and the markets [(1), p. 517].
1. Elevator Classification
Grain elevators are classified as either country elevators or terminal elevators, according
to elevator size, grain source, and final destination of the grain. Country elevators accept the
major portion of their grain from farms, while terminal elevators are often subdivided into port
terminals and inland terminals (subterminals). The subterminals accept the majority of their grain
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from country elevators and a small portion from farms directly. Grain is shipped from the
subterminals to the port terminal or directly to the processors [(1), p. 517]. Figure 1-1, a
schematic of a traditional country elevator, illustrates typical grain elevator operations.
2. Emission Sources
The pollutant of concern at grain elevators is PM in the form of grain dust. Dust is
entrained in incoming grain, and the materials-handling operations at grain elevators increase the
dust concentration level. The dust is often comprised of 60-90% organic material, while 3-20%
of the inorganic material may be free silicon. The paniculate matter typically includes grain
kernel particles, spores of smuts and molds, insect debris, pollen, and field dirt [(2), p. 2-12, 2-
14]. The size of the grain, its moisture content, the percentage of foreign matter in the grain, and
the extent of handling affect emissions and their makeup [(2), p. 2-14, 2-15, 2-16].
Not all grains are alike or have the same emissions' profile. EPA tests indicate that dust
emissions from soybeans are greater than those from corn, wheat, or milo; these excess emissions
are attributed to excess soil collected during harvesting of the low growing beans. The methods
used to unload, handle, process, and load the grain can also greatly affect emission levels. Dust
is emitted from each process within the elevator, often in the form of fugitive emissions [(2), p.
2-14].
C. ELEVATOR OPERATIONS
Each class of elevators performs the basic operations of receiving, handling and transfer,
drying, and loading and shipping, regardless of elevator size [(1), p. 517],
1. Grain Receiving
Trucks, railcars, and barges deliver the grain to the elevators, with each mode of transport
employing various methods of unloading [(1), p. 519],
a. Truck Receiving
Trucks unload the grain on a dumping platform or at a dump pit, either of which may be
open, partially contained, or completely enclosed. By raising the front end of the truck bin, the
grain falls into an underground pit from the back of the truck [(1), p. 519]. Emission levels
produced during the dumping operation depend upon the:
« truck type;
• size of the receiving hopper;
« speed at which the grain is dumped;
• grain type;
• surface moisture content of the grain;
• amount of foreign matter in the grain [(2), p. 2-19];
• drop height; and
• the wind currents [(1), p. 519].
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1. DwtCotector
2. Head Houaa* Pulley and Leg Baft
3. OMffeutorTraratora Grain from
Elevator Lao, to any Bin.
Automate Seal*, or Truck Spout
4. Cleaner
5. DMrfeuter Spouting
8. Upper Scato Hopper
7. Automatic Scale
9. LoadOutSpoU
10. Generate L»g
11. UgBalandBuolwto
12. Tmh nd Seraenlng* Bin
13. Truck Load-Out Spouts
14. AaratlonSyifem
IS. DnVaway
16. DumpOntam
17. Oumpn>
1B. EtaetrieTmcUm
19. Tunnal
20. Boot and Lowar Lag
17
Figure 1-1: Schematic of a Traditional Country Elevator [(1), p. 518]
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b. Railcar Receiving
Railroad hopper cars or boxcars may be used to transport grain. Hopper cars unload grain
from the bottom of the car into a pit similar to that used for truck unloading. To release grain
from railroad boxcars, the inside grain door is broken. After the initial burst of grain flow
ceases, power shovels or bobcats transfer the remaining grain from the car to the pit. Large
facilities may use a mechanical car dump to swivel and tilt the car to release the grain into the
pit [(1), p. 519]. Emission levels created during offloading of railroad hopper cars and railroad
boxcars depend upon the:
• grain drop pattern [(1), p. 519];
• amount of wind protection;
• grain type;
• surface moisture content of the grain; and
• amount of foreign matter in the grain [(2), p. 2-20, 2-22].
In addition to the factors listed above, the size of the receiving hopper affects the emissions from
railroad hopper cars, and the method used to unload boxcars affects emissions from them. [(2),
p. 2-20, 2-22, 2-23].
c. Barge Receiving
Barges are unloaded using either a pneumatic discharge system or a bucket elevator which
is lowered into the hold to remove the grain and dump it into the pit [(1), p. 519]. Emission
levels generated during grain transfer depend upon the:
• type of grain;
• moisture content of the grain;
• amount of foreign matter in the grain [(2), p. 2-23];
• amount of wind protection;
• conveyor transport speed and distance; and
• vertical drop heights at transfer points.
2. Grain Handling and Transfer
Grain is transferred within elevators using bucket elevators (tegs), belt conveyors, and
gravity flow. The buckets in the legs collect the grain in the boot and carry it to the head of the
leg by way of an internal pulley mechanism. Gravity feed transfers grain to belt conveyors
which horizontally transport the grain within the elevator. Grain is removed from the conveyor
belt at the dump station, or at another point along the belt by a tripper. Grain is moved to
storage and load-out areas using gravity flow through spouts [(1), p. 522].
Dust is produced as grain is discharged into the boot, as the buckets collect the grain
while moving through the boot, and as the head releases the grain from the elevator. Emissions
are also generated as the grain falls onto and from the conveyor belt. Dust particles attached to
1-4
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the conveyor are released from the belt as it moves on the underside of the system. When
expelling grain through spouts using gravity flow, dust emissions are also created [(1), p. 522].
The speed at which handling and conveying equipment is operated can greatly affect the
amount of emissions produced. Dust is produced when grain is agitated or disturbed. If handling
and conveying equipment is operated at a slower speed, dust emissions will usually be reduced.
Hoods vented to cyclones or fabric filters are needed on handling equipment at points where the
grain is being disturbed (e.g., where it enters or leaves a conveyor belt) [(3), p. 4-12, 4-14].
"Legs" (or bucket elevators) are areas where emissions can occur. Grain enters me
bottom of the leg and is carried to the top by buckets. Since positive pressure is created at the
top by this movement, the top of the leg must be vented to a control device to prevent the build
up of dust. The leg can also be operated at a slower speed to reduce the formation of dust [(3),
p. 4-14].
Scale hopper and surge bins are vented to a control device such as a cyclone or fabric
filter. Storage silos produce minimal emissions and are sometimes vented to a control device.
Grain cleaners screen the grain to remove impurities such as dirt, sticks, and other trash.
Emissions from screen cleaners and scalpers are controlled by hooding and/or enclosing the
equipment and ventilating the paniculate material to a cyclone or fabric filter. The best grain
cleaning equipment uses air-tight screening [(3), p. 4-17].
3. Drying
Dryers, specifically batch or continuous-flow dryers, reduce the moisture content of the
grain in the elevators. Batch dryers dry and cool motionless grain, while continuous-flow dryers
service grain as it moves through the dryer. The continuous-flow dryers are either cross-flow,
concurrent, or counterflow dryers, depending upon the movement of the air with respect to the
grain column. In cross-flow dryers, which are the most common, air flows across the column.
Air moves in the direction of grain flow in concurrent flow dryers, which use higher air
temperatures and produce the highest quality grain. The design of concurrent flow dryers is more
complex, however, and they are susceptible to fire. Air moves in the opposite direction of the
grain flow in counterflow dryers; these dryers achieve the most drying in the smallest space, but
are less efficient, harder to build, and generate the lowest grain quality of all dryer types [(1),
p. 523].
Column and rack dryers are two types of grain dryers most often used in the industry.
Column dryers pass grain between perforated plates. Grain is dried with a stream of heated air
that moves from the inside plate out through the grain. Rack dryers use a series of baffles
around which the grain and heated air must flow. Due to their design, uncontrolled column
dryers produce fewer emissions than rack dryers. Various types of screens are used as control
devices on grain dryers. The level of emission control can be adjusted by changing the screen
size on the dryer [(2), p. 2-29, 2-31; (3), p. 4-19].
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4. Loading and Shipping
Different techniques and control strategies are used in loading trucks, railcars, barges, and
ships. Most involve the use of some type of enclosure usually connected to a control device such
as a fabric filter or cyclone to prevent paniculate emissions. Paniculate emissions can be
reduced during loading if the free-fall distance of the grain can be minimized [(3), p. 4-22,4-26].
a. Truck Loading
Paniculate emissions from truck loading are affected by free-fall distance and wind.
Grain dust emissions can be significantly reduced by minimising the free-fall distance emissions
and providing the truck shelter from the wind while loading. [(2), p. 2-31, 2-33].
b. Railcar Loading
Hopper cars and boxcars are the two types of railcars typically used in grain loading
operations. Emissions are reduced while loading hopper cars by minimizing the free fall distance
from the spout to the top of the hopper car. Emissions from boxcar loading are reduced using
enclosures around the loading area [(2), p. 2-33, 2-34, 2-35].
c. Ship Loading
Bulk carriers, tankers, and 'tweendeckers are the three types of ships most often used for
grain transport. Tankers are more enclosed than the other two types of ships and produce fewer
paniculate emissions when loaded. Due to the large open hatches used for loading, bulk carriers
have the potential to produce more emissions than tankers. The use of a high-speed conveyor
belt to transfer grain from the loading spout to the ship gives tweendeckers the potential to
produce more emissions than bulk carriers [(2), p. 2-37, 2-38, 2-39].
d. Barge Loading
Paniculate emissions can result when grain is poured into the hatch on top of the barge.
Minimizing the free fall distance of the grain is an important step in reducing emissions.
Paniculate emissions can also result from grain movement inside the barge. This type of
emission can be minimized by using smaller openings to load and unload grain. By minimizing
the exposed surface area of the grain, wind will not have as great a chance to stir up the grain
dust [(2), p. 2-35, 2-37].
1-6
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CHAPTER!
OIL SUPPRESSION SYSTEM
A. INTRODUCTION
With the establishment of stricter dust regulations and safety standards by the Federal
government, there has been heightened interest in the use of oil for dust suppression at grain
handling facilities. Many large companies have already installed equipment and implemented
operating procedures required by the new regulations, but smaller facilities that do not use
mechanical dust control equipment may also find oil suppression to be cost effective.
B. SYSTEM DESCRIPTION
Oil suppression has been used worldwide for more than a decade, with its users ranging
from small country elevators to large export terminals. The basic oil suppression process consists
of applying a fine spray of edible oil (either mineral or vegetable) to the stream of grain entering
the grain elevator [(4), p. 11]. Use of oil has been approved for wheat, corn, soybeans, barley,
rice, rye, oats, and sorghum in the Food and Drug Administration's (FDA's) regulation 21 CFR
172.878 [(5), p. 5].
In the oil suppression system, an oil additive coats the grain surface to a depth dependent
upon the amount applied and the uniformity of coverage. Dust adheres to the oil on the grain's
surface as the grain moves throughout the handling process. Physical forces such as gravity,
inertia, and vibration can cause dust particles to detach from the grain surface by overcoming the
adhesive force between the oil and the dust. The suppression of smaller dust particles is more
prevalent because the adhesion force for smaller particles is greater relative to the acting physical
forces. A type of coagulation exists with the application of oil. Small dust particles will likely
attach themselves to other small matter, which tend to settle out more quickly than separate
particles [(6), p. 3].
1. Oils
The two types of oils used in the dust suppression system are soybean oil and mineral oil.
Quality is an important factor in the selection of the oil, since a poor quality oil may cause
deterioration of the grain [(7), p. 9].
a. Soybean
Before soybean oil is used, it needs to be fully refined, bleached, and deodorized
[(7), p. 9]. No limit has been set on the application rate for soybean oil; good manufacturing
practice governs its use, however, since overapplication is ineffective and costly. Although
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soybean oil loses viscosity in cold weather and is subject to oxidation which leads to rancidity,
these problems are reduced through the use of heaters and proper oil handling [(4), p. 13].
b.
Mineral Oil
When white food-grade mineral oil (composed primarily of liquid hydrocarbons paraffinic
and naphthenic in form extracted from petroleum) is used, it needs to be stable [(7), p. 9]. The
fractional distillation of crude oils produces either paraffine or naphthene. Since paraffine is
more abundant, mineral oils of a paraffine nature are less expensive. Naphthenic oil is used in
colder climates since it has a better pour point (the lowest temperature at which the oil flows)
[8]. Before use on grain, this mineral oil must be cleaned and approved through testing. Unlike
vegetable or grain oils, mineral oil does not have the potential for oxidation, so the problem of
rancidity does not exist. The application of white mineral oil is limited to 0.02% by weight or
200 ppm on grain used for human consumption and 600 ppm for grain consumed by animals.
The pour point and viscosity are important criteria when selecting white mineral oil [(4), p. 11;
13].
2.
Effectiveness
The optimum control efficiency for an oil suppression system is realized when uniform
coverage of each grain surface is accomplished. An application rate of 130-160 ppm (4-5
quarts/1000 bushels) has proven to be effective, though a rate of 200 ppm (6-7 quarts/1000
bushels) is allowed by the FDA [9]. Vendors predict a dust reduction of 75-99% [(10), p. 1].
Testing conducted by the U.S. Department of Agriculture (USDA) in 1982 demonstrated dust
reductions ranging from 31-96% for mineral oil applied to corn, and 63.3-77% for soybean oil
applied to wheat [11].
The amount of oil needed to control grain dust emissions depends on the type of grain
being handled and the amount of dust present. Excessive application of the oil will not
substantially increase the amount of dust suppressed by the oil. Therefore, in order to optimize
the dust retained by the grain and prevent the overuse of oil, the application rates provided in
Table 2-1 for certain grains have been recommended [12].
Table 2-1: Recommended Application Rates of Mineral Oil and Soybean Oil to Various Grains [12].
Grain
Com
Sorghum
Soybeans
Wheat
Qoarts/1,000 Bushels
6-6.8
4-6
4-6
6-6.8
PPM
175-200
120 - 175
120 - 175
175 - 200
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The amount of dust captured by the oil depends on a dust particle's physical forces
(gravity and inertia), the amount of oil on the grain's surface, and dust particle size. An oil
suppression system is very effective on smaller micron particles, which are the most volatile and
create the environment for grain dust explosions. Very effective dust control is achieved for up
to six months, or for six to eight handlings of the grain after the oil application, after which dust
control begins to decline. However, tests performed by the USDA and other operators indicate
that the effects of the oil may last for the first 8-10 grain handlings and have not diminished after
two years in storage. According to the American Soybean Association (ASA), up to 0.14% of
the grain weight is lost each time the grain is handled, but is reduced to 0.035% with the use of
an oil additive [(10), p. 2].
3. Point of Application
The success of an oil suppression system depends primarily upon the point of application,
which should be as early as possible in the gram handling process, preferably before the grain
is first elevated [(4), p. 15]. To enable thorough mixing of the oil with the grain and ensure
complete coverage, the grain should be sprayed at an active point, or when it is suspended.
Suitable mixing is achieved within 20-70 seconds, and is contingent upon an effective initial
application, the oil viscosity, and ambient temperature. Since oil viscosity varies with
temperature, both of these parameters must be monitored and controlled during application. This
can be accomplished using mechanical or electronic flow meters. The temperature can be
controlled with heat tape or heaters. The most effective location for the heater is inside the
controller directly before the nozzle [13]. Experts recommend that the oil be kept at a
temperature in the range of 4-27°C and never be heated above 49°C since this can cause the oil
to break down [4, p. 15].
The ideal point of application is at the first point of transfer, most often between the
receiving pit gate and the leg. As illustrated in Figures 2-1 and 2-2, the oil can be applied to the
grain before it enters the bucket elevator leg, either immediately before or after the pit gate [12].
Figure 2-1: Nozzle Assembly in Receiving Pit
Alternative 1. [12]
Figure 2-2: Nozzle Assembly in Receiving Fit
Alternative 2. [12]
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For better dispersion, a second nozzle may be added at a transfer point, such as a bin exit or belt-
to-belt transfer location, as shown in Figure 2-3.
Conrejror Bdt
\
Figure 2-3: Nozzle Assembly in Conveyor System. [12]
The transfer point selected should be as close to the origin of grain movement as possible. It is
desirable to use mechanical or gravitational mixing after the application to ensure complete
blending of the oil and grain. A mechanical device may need to be used in conjunction with the
oil system if the oil cannot be applied early enough in the handling process [(14), p. 12].
4. Equipment
The complexity of the oil suppression system depends on the needs of the elevator
operator [12]. The basic equipment required consists of a storage tank suitable for holding food-
grade oil, a small pump, check valves to preclude oil from draining when the pump is off, a
filter, a pressure regulator to control the flow and application rate, a pressure gauge, automatic
shut-off and limit switch to stop the oil when the grain flow ceases, tubing, and a spray nozzle
configuration [(4), p. 13]. When the system is operated at an ambient temperature less than 30°F
(-1°C), tank heaters or in-line heaters are necessary to warm the oil which is best applied at a
temperature of at least 75-80°F (24-27°C) [12]. It is desirable to automate the system with
solenoid valves or electronic eyes in the grain stream to activate the application of the oil when
the grain is in motion. An illustration of a typical system is given in Figure 2-4 [(7), p. 10].
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Pressure
^ Gauge
Tank
Electric
Shut-off
Switch
Check Valve
Plastic Tubing
Nozzle
Limit Switch
Paddle Arm
Grain Belt
Figure 2-4: Typical Oil Suppression System.
a. Main Storage Tank
The main storage tank is often made out of mild carbon steel, stainless steel, glass-lined
steel, or Fiberglass certified as "food grade" or "sanitary" by the National Sanitation Foundation.
Mild carbon steel tanks should be treated with a protective coating (which meets FDA and USDA
requirements) that helps maintain oil integrity. The outside of exterior storage tanks should be
coated with flat black paint to achieve maximum solar collection. The draw-off level of the tank
should be approximately 10 inches from the tank bottom to allow for paniculate matter
settlement, which is particularly important for uncoated tanks. The boot should be cleaned
regularly to preserve the food grade quality of the oil. In addition, water draw should be placed
at the bottom of the tank and the top vent should be protected with desiccant. A capacity of
8,000 gallons is suggested for bulk storage of 6,000 to 6,500 gallon-shipments [(IS), p. 1].
However, a storage capacity not greater than 20-30% of the annual capacity is recommended to
limit the amount of oil that could be contaminated [12].
The oil is transferred from the main storage tank to a day storage tank from which it is
pumped, preferably with a gear type pump, to the grain elevator. This operation can be regulated
automatically using a ceramic float valve inside the day tank. A heater is suggested to ease the
transfer of the oil from the main tank to the day tank [(15), p. 2]. Piping should be made from
approved steel or certain thermoplastics, such as food grade or sanitary variety. Fittings,
couplings, valves, or pipes should not be made from copper, bronze, or brass [(15), p. 1].
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b. Day Storage Tank
The day tank should be a 250-gallon insulated stainless steel tank with a thermostatically-
controlled electric heating coil which keeps the oil at a temperature of 70°F. The oil pumped
from the day tank to the elevator passes through an industrial hydraulic filter. The primary lines
carrying the oil from the day tank to the point of application should be covered with explosion-
proof, thermostatically-controlled heat tape to sustain the oil temperature and viscosity at the
point of application [(15), p. 2].
c. Other Equipment
The oil pressure needed to apply the appropriate amount of oil at the point of application
depends on the nozzle diameter and the oil temperature, and is achieved using a regulator. The
pressure can range from 30-65 psi and the type of nozzle selected depends on the grain flow rate
desired [(15), p. 2].
C. EFFECTS OF OIL
When sufficient mixing is achieved, the following short term effects are realized: clean
leg boot environment, clean leg trunk and casing environment, and no dust emissions in the leg
head, distributor, and gallery areas. The long term effects include: no dust problems when
retrieving and loading out treated grain, self cleaning of the bins and silo walls when filling and
unloading, and easier, less expensive housekeeping. However, the use of an oil additive does not
eliminate the need for safe operating procedures, including proper housekeeping measures and
routine equipment maintenance [(16), p. 47-48].
a. Mechanical Devices
The mineral oil applied to the grain does not clog the conventional dust collection
equipment and the efficiency of such controls is improved as the result of the aggregation of fine
dust. There has been no evidence of the formation of slick oil spots from the application of the
oil, though oil applied directly to older conveyor belts may shorten the belt operation life through
deterioration, which may warrant the use of oil resistant belting. Overall, the reduced dust levels
improve the safety and maintenance of the facility [9].
b. Shrinkage Reduction
Weight that would otherwise be lost as grain dust is now retained by the grain stream, and
can be sold as grain. For lots treated with mineral oil, approximately 250 pounds of dust are
retained per 1,000 bushels of grain. This translates into approximately 1-1.5 bushels per 1,000
bushels that are not lost to shrinkage [12].
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c. Grain Quality
Lab studies produced the following results on the effect of mineral oil on the quality of
the grain to which it is applied. No odor was detected on the grain from single applications of
200 ppm of oil or multiple treatments up to 600-800 ppm. No change in the grade of the grain
was observed up to 9-12 months and there was no effect on the germination. The drying
capability was actually increased with reduction in dust, and the oil did not encourage the growth
of mold. The angle of repose decreased with the application of the oil, and short term repellency
of insects was evident with the application of 200 ppm of mineral oil [9]. Directly after the oil
application, a slight decrease in test weight was observed which returned to the original value
within 6 months. This initial decline hi weight is attributed to increases hi kernel size from the
adhered dust, making the kernels bigger so they stack differently in the measurement cup [13].
d. Grain End Use
There was no change hi the amount of power needed by the milling equipment for the
treated and untreated grain. The flour color was not affected as shown in test millings and
bakings. USDA tests demonstrated no difference between the baking quality of flour from
untreated and treated wheat.
e. Grain Dust Explosions
Dust generated by the grain handling process creates a potentially hazardous environment
that could result in an explosion. Since the dust adheres to the grain and the amount of
suspended dust particles is greatly reduced, the potential for a grain dust explosion is decreased
[12].
/. Reduction in Health Hazards
The application of oil reduces the levels of inhalable and respirable dust. Inhalable dust
particles are smaller than 10 microns in diameter and can penetrate the upper respiratory system,
acting as an irritant. Respirable dust particles are smaller than 5 microns hi diameter and can
penetrate the lower respiratory system, resulting hi chronic respiratory disorders [12].
D. SYSTEM BENEFITS AND DISADVANTAGES
1. System Advantages
Several economic and safety benefits are realized from the use of an oil suppression
system.
a. Economics
The amount of shrinkage is decreased because the dust adheres to the gram and less grain
is lost as dust. This attached dust may now be sold at grain prices while reducing the costs
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associated with dust disposal and handling [13]. In addition, the labor costs associated with
housekeeping are reduced since the amount of time required for dust removal is lower because
of smaller amounts of dust present within the elevator. The decreased amount of dust present
in the elevator can also extend the life of the equipment since the moving parts are cleaner [17].
b. Equipment
With regard to installation, operation, and maintenance, the cost of the oil suppression
system is low when compared to mechanical dust controls [13]. To achieve optimum benefits,
the oil must be applied correctly. Mechanical dust controls may also be needed in addition to
the oil additive if the oil cannot be applied early enough in the grain handling system as a result
of the grain elevator design [(4), p. IS]. However, when used in conjunction with an oil
suppression system, some of the fans in a mechanical air system may be turned off, which will
reduce the electricity costs [13]. In addition, the oil system requires little or no maintenance
while pneumatic systems, or baghouses, must be inspected and serviced daily [(14), p. 10].
c. Safety
Oil additives reduce the amount of dust emitted within an elevator, thereby increasing
worker safety by decreasing the possibility of an explosion and providing a cleaner working
environment. The amount of respirable dust inhaled by the workers is decreased because the dust
is entrained in the grain [17]. Since the threat of explosion is greatly decreased with the use of
an oil additive, insurance premiums may be reduced [13].
2. System Disadvantages
a. Grain Quality Concerns
The main obstacle for the oil suppression system relates to the effect the oil has on grain
quality. Grain exporters are hesitant to buy grain treated with an oil additive since they are not
sure of the acceptance of oiled grain in the world market, especially with foreign market demands
for improved quality of exported grain, governed by new grain standards with an emphasis on
cleaning [18].
It is not known how the foreign matter attached to the grain will affect its quality and
price [14, p. 10]. Mills and distilleries are concerned about the long-term effects of oil on the
grain. Mills have stated that the oil seems to adversely affect the tempering process in wheat and
causes discoloration in flour. However, studies on oil-treated grain conducted by the American
Malting Barley Association and U.S. Grain Marketing Research Laboratory reveal no significant
effects on functional properties of oil-treated wheat.
b. Application
Because the application rate for mineral oil is limited by the FDA to 200 ppm, it is
necessary to monitor the oil flow rate, which is affected by temperature and pressure. As the
pressure increases, the temperature of the oil decreases. The best way to control the application
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rate is with a flow meter that indicates the flow rate hi gallons per minute. Automatic levers
may be installed to open and shut valves to control the flow of oil, ensuring that oil is applied
only when the elevator equipment is operating. However, several operators have experienced
problems with the oil application rate when the systems were installed hi stages. The application
rate is more accurate when using complete systems in which the rate can be easily monitored and
controlled [18].
There is currently no method for determining the amount of oil that has been applied to
the gram to judge compliance with FDA limits. Therefore, oil could conceivably be applied at
each handling facility. To prevent overapplication of oil, shipping papers that identify the
application of oil may be used to notify the subsequent recipient of the gram [18].
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2-10
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CHAPTERS
OIL SUPPRESSION SYSTEM - TESTS
A. INTRODUCTION
The results of various tests performed to determine the effectiveness of oil application
systems in suppressing dust from grain elevators are outlined in this chapter. As part of this
coordinated CTC project, such a test was to have been conducted at a grain elevator site by
others. However, because funding for the test was not obtained, the test was not performed. The
discussion of tests in this chapter, therefore, is limited to those described in the literature.
Neither the validity of the tests described hi the literature, nor the appropriateness of test
protocols used was evaluated, for these tasks were beyond the scope of this project. Rather, the
results of the tests were analyzed to ascertain if they demonstrated the effectiveness of oil
application systems in suppressing dust. However, EPA's Emission Inventory Branch of the
Office of Air Quality Planning and Standards, has concluded that tests described in the literature
and cited here are inadequate for the purpose of establishing emission factors for grain elevators
using oil suppression technology.
B. OIL SUPPRESSION TESTS
1. U.S. Grain Marketing Research Laboratory
The U.S. Department of Agriculture performed a large scale study at the U.S. Grain
Marketing Research Laboratory in Manhattan, Kansas based on thirty-eight tests performed in
December 1980 at the Ohio Farmers' Gram Elevator hi Fostoria, Ohio. The study was designed
to determine the effectiveness of water, deodorized soybean oil, and carnation mineral oil in
suppressing dust emissions from corn, wheat and soybeans [11].
a. Elevator Configuration
The configuration of the grain elevator used in this test is illustrated hi Figure 3-1. An
enclosed 36-inch-wide conveyor belt transferred grain from a storage bin at 400 ft/min. At Site
A the grain was moved from the first conveyor belt to the second. Site B marks the end of the
second conveyor belt (100 feet from Site A) where the grain entered 25 feet of spouting and
subsequently fell into the boot on the descending side of the bucket elevator. At a rate of 10,000
bushels/hour, the grain ascended 240 feet and was released into spouting, from which it fell into
a 2,500-bushel garner and subsequently a 2,500-bushel scale. The gram then was directed to a
distributor and sent to Site C, the start of the gallery belt. The vertical distance travelled by the
grain from the head of the leg to the gallery belt was 100 feet. From Site C the gram travelled
85 feet to Site D, the first tripper, and then to the house belt. Grain travelled on the house belt
to the second tripper, Site E, which was located at the entrance to one of the three similar test
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control
OJ
spouting
A - ADDITIVE SAMPLING SITO
R - FIRST SAMPLE SITE
C - SECOND SAMPLE SITE
D - BELT TRANSFER POINT
B - TEST BIN SITE
gnrner
scale
control
2nd (ripper
control
distributor
control
A spouting
OIL ADDED HERB
bucket elevator
boot
i Tot FitOHlM of Gnbi Hmflhig Sjttrm for A
-------
bins. The test bins were each 114 feet deep and held 9,000 bushels. Site D was 25, 310, and
320 feet from the three bin sites [(11), p. 3, 4]
b. Existing Control System
The existing dust control system consisted of several baghouse filters located throughout
the elevator. The various systems collected dust and discharged it through a system of ducts into
a dust bin. The lower control system controlled Site B, collecting dust from the ducts at the end
of the second enclosed belt and the boot of the bucket elevator. The upper control system
serviced Site C, at the head of the bucket elevator and the gamer. The gallery control system
removed dust from the hood over the front end of the gallery belt and first tripper, Sites C and
D. The headhouse system removed dust from hoods servicing the beginning of the house belt
and second tripper, Sites D and E. In order to collect dust in bags for the test, the dust discharge
duct at Sites B, C, between C and D, and between D and E were averted [(11), p. 4].
c. Additive Application
As illustrated in Figure 3-2, an automatic spray unit consisting of two nozzles, sprayed
the grain stream at the first transfer point as the grain was moved from one storage bin to
another. The first nozzle applied the additive to the top surface of the grain near the end of the
first conveyor belt, and the second nozzle sprayed the underside of the grain stream as it fell
from the first belt to the second belt, four feet from the first nozzle [(11), p. 5]. Some immediate
mixing was achieved as the grain fell from the first belt to the second belt. The grain flowed
at a rate of 400 ft/min. The level of additive applied to the grain ranged from 0.02-0.08% for
the mineral oil on the com; 0.02-0.06% for the soybean oil on the wheat; and 0.03-0.06% for the
soybean oil on the soybeans. The oil flow rates were controlled with compressed nitrogen via
a control valve. Since these tests were conducted during the winter in cold weather, heat was
applied to the oil to achieve sufficient spraying. All three types of oil were separately applied
to the com, but the soybeans and the wheat were only treated with soybean oil [11].
d. Sampling Procedure
Two control lots of grain without oil suppression were tested, one with the dust control
system on, and one with the dust control system off. High, medium, and low levels of oil were
applied and tested with the dust control system off. At least one test with each type of oil was
administered with the dust control system operating to determine the difference in the amount
of dust collected by the existing control system. Hi-volume air samplers were used to collect
airborne dust samples at Sites B, C, and E. The samplers operated continuously as the batch of
grain moved through the elevator [11].
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NOZZLE
FROM SPRAYING SYSTEM
FLOW REGULATOR
•BELT
CONVEYOR
Figure 3-2: Liquid Additive Spraying System. [11]
Grain samples collected at Site C at two-minute intervals were analyzed for their fine
material content, grain grade, moisture content, and weight — a drop test dustiness analysis was
performed using a HIAC particle counter (High Accuracy Particle Counter) to determine the
particle size distribution and concentration. This test involved creating a dust cloud by dropping
dusty material and allowing it to hit a surface. If two materials differing in dustiness are treated
in the same manner, the two resulting clouds will differ in the number and size of particles. If
no difference in the number or size of particles exists, the two materials are equally dusty. The
objective of the test was to detect dust originating only from grain samples by preventing dust
from grain handled outside the test environment from interfering in the total counts [11].
e.
Results
Since testing was conducted continually from December 7-12 due to a tight schedule,
some fine dust possibly remained from one test to the next. Emissions were measured inside the
enclosed transfer belt before entering the boot, at the open gallery, and inside the bin overspace
where the bin was being filled. The drop test analysis showed significant dust reduction with the
use of oil suppression for all three grams, often > 90%. Also, the use of oil reduced trailing dust
emissions (dust from the work floor, garner, and gallery floor) by 75%. Since the FDA limits
the application of oil additives to grain at 0.02% by weight, or 200 ppm, the table below provides
only those results relating to an application rate of 0.02% by weight. Appendix A contains tables
showing the complete results of the tests. Because the drop test results represent dust control
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levels in a controlled (ideal) environment, they do not appear to represent practical levels of
control.
Table 3-1: Percentage Reduction in Dust Concentration [11].
Grain
type
Com
Wheat
Additive
Mineral oil
Soybean oil
Amount
of
additive
0.02%
0.02%
Dust
control
system
on
off
off
off-
Reduction in
pre-leg enclosed
belt dust
concentration
SiteB
31.0%
55.8%
63.3%
-156.2%
Reduction in
gallery open
belt dust
concentration
SiteC
73.3%
96.7%
77.0%
-604.0%
. Reduction in
binoveispace
enclosed dust
concentration
SiteE
79.6%
69.1%
70.7%
6.5%
a Since these values are not valid reduction percentages, it is assumed that a malfunction occurred during testing.
No explanation was given as to why these numbers were obtained.
Both oils had similar performances. Good reduction locations included the boot, bucket
elevators, and the gallery floor. Bad reduction locations included the enclosed belt and the pre-
leg belt. The authors concluded that the most effective level of oil treatment is approximately
0.03%. After twelve months of storage, no adverse effects on the grain were detected.. The
functional properties of the wheat, including baking and milling, were not affected and there was
no evidence of oxidative rancidity for mineral oil treatments [11].
/. General Comments
The USD A reached the following conclusions from the results of the tests:
(i) Thorough mixing of the grain following the application of oil is one of the most
critical elements in the success of controlling dust. The treatment should be
applied at an early stage of grain flow from a bin. The modifications required for
effective application in existing installations is rninimal.
(ii) Little oil accumulated on the equipment or walls. This was credited to proper
mixing and low treatment levels.
(iii) There was no consistent detection of the presence of soybean oil or mineral oil on
the corn or wheat.
The tests demonstrated an effective reduction in dust emissions when 0.03-0.10% by
weight of mineral oil was applied to all three grain types, and 0.02-0.08% by weight of mineral
oil was applied to com. The optimum effectiveness was achieved for oil applications in the
range of 0.02-0.05%. The effectiveness of the mineral oil to control dust emissions from the corn
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was not affected after three months of storage. Dust dispersion causes an average grain weight
loss of 0.14% with each grain handling. The application of oil decreased this loss to 0.035% or
less [11].
2. Agricultural Engineering Department at Texas A&M
The Agricultural Engineering Department at Texas A&M performed a study to determine
the amount of dust retained by corn and milo with the application of mineral oil at different
levels for varying grain dust concentrations.
a. Test Procedure
Mineral oil was mixed with the grain samples in a box at 0 ppm, SO ppm, 100 ppm, 200
ppm, and 400 ppm by weight. Grain dust was subsequently added to the grain at concentrations
corresponding to 0.0%, 0.1%, 0.25%, and 0.5% by weight of the grain. The samples were mixed
again, after which the dust was removed and analyzed. From this, the optimal mineral oil
application rate for dust retention was determined [6].
b. Test Results
1. Corn
A 200 ppm application rate for mineral oil on corn produced the maximum dust retention
of 83.8%, of which 35.6% of the particles retained were less than 10 um (PM-10). For the
remaining free dust, 28.9% of the particles were PM-10 [6].
2. Milo
Results indicated that an application rate for mineral oil of 200 ppm provided the
optimum dust retention of 73.7%, of which 46.8% of the particles retained were PM-10 [6]. For
the remaining free dust, 33.7% of the particles were PM-10 [6].
c. Test Conclusions
The tests performed on the corn and milo grains illustrated a reduction in the amount of
suspended smaller dust particles, with a greater amount of these smaller particles being retained
on the grain surface. This adhered dust can be sold as grain, thereby increasing the value of each
batch.
Since these tests were conducted in a controlled environment and not performed in an
actual elevator, the results cannot be used as control efficiency data because the tests were
conducted under ideal conditions, not actual field conditions. However, the results demonstrate
the potential effectiveness of the oil suppression system and provide information regarding PM-10
emissions reductions [6].
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CHAPTER 4
CONVENTIONAL CONTROLS
A. CONVENTIONAL CONTROLS
Conventional control methods for reducing PM emissions from grain handling and
processing operations associated with grain elevators include process modifications to prevent or
decrease emissions, and the use of capture and collection systems [(1), p. 524]. Grain handling
generates PM emissions in the form of fugitive emissions, resulting from the dust's absorption
of mechanical energy by the grain operations and the local air currents within the elevator.
Process modifications are designed to reduce these effects.
The primary modifications employed for handling and transfer operations are construction
and sealing practices that reduce air currents, minimize the vertical distance the grain must fall,
and minimize grain velocities. Although the aforementioned practices minimize emissions, most
elevators employ ventilation or capture systems to achieve emissions' rates that are within
acceptable levels.
Except for small elevators, most grain handling and processing plants use ventilation or
receiving pits, cleaning operations, and elevator legs. Hooding systems are sometimes used for
handling and transfer operations [(1), p. 526]. The PM emissions are collected by capture
systems, such as hoods and aspirators, and routed to the conventional collection controls. The
collection systems most frequently used to control dust emissions from grain handling operations
are fabric filters and cyclone collectors.
B. FABRIC FILTERS
The baghouse (or fabric filter), the most effective device currently used, demonstrates an
efficiency greater than 99% and collects larger particles as well as very small and light particles
[(1), p. 525-527]. The collected dust consists of a high concentration of fine, dry dust which
creates a high explosion potential if the dust is not handled appropriately.
Operating grain elevators subject to the New Source Performance Standards (NSPS)
requirements outlined in 40 CFR Part 60, Subpart DD use fabric filters exclusively. Elevators
not subject to the NSPS, but governed by more stringent local requirements as a result of their
location, also employ fabric filters [(3), p. 4-1].
The typical fabric filter used at an elevator filters 2,000-50,000 cubic feet of air per
minute, depending upon the operating conditions at the particular elevator and the dust collection
demand on the system. The filter operates under negative pressure with a fan drawing air
through the apparatus [(3), p. 4-1].
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Most filters are made of felted, synthetic fabrics, with air-to-cloth ratios ranging from 3:1
to 15:1; typical filters range between 8:1 and 11:1. Filter bags must be cleaned periodically. The
dust cake may be dislodged from the fabric in several ways ~ using back pressure; collapsing
the cloth to crack the dust cake; snapping the cake off using compressed air; or blowing off the
cake with a reverse jet that impacts the cloth's outside surface. When properly maintained, the
fabric filters will emit no visible emissions [(3), p. 4-3].
C. CYCLONES
Cyclones retain a higher percentage of large particles than small particles; the large
particles are often restored to the grain stream, while the smaller particles are emitted to the
atmosphere. Cyclones demonstrate an efficiency ranging from 85-99% depending on the
operation or area controlled in the handling system [(1), p. 525-527]. Sometimes cyclones are
used to prefilter the air sent to baghouses so that a high portion of the collected dust can be
reintroduced to the grain stream and the smaller, lighter and more hazardous particles can be
removed [(19), p. 182}.
Elevators not subject to the NSPS requirements, especially small and older facilities, use
cyclones. These cyclones are classified as either "high-efficiency" or "high-throughput". High-
efficiency cyclones have narrow inlets and long bodies when compared to their diameters, and
small outlets; high-throughput cyclones have large inlets, large diameters, and large outlets.
Unlike the fabric filter, the cyclone does not address the problem of visible emissions [(3), p. 4-
3].
D. CYCLONE/BAGHOUSE COMBINATION
Many elevators use cyclones in a series within a baghouse. The collected dust is not sent
through the grain handling and controls again. Certain limitations govern the use of this method
to lessen the continual recirculation of dust [(19), p. 182]:
• The dust should not be reverted to the bucket elevator.
• The dust should be reintroduced to the grain stream below the point of collection.
• The dust should not be added to the stream in areas where the dust could reenter
the controls.
• The dust added to conveyors or spouts should be introduced under or inside the
grain stream.
E. CONTROL MALFUNCTIONS
Although the baghouse and cyclone are effective controls of PM emissions in grain
elevators, both control devices can fail if the entire system is not properly operated and
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maintained. [(1), p. 526] In order for the control devices to operate efficiently, the elevator
operators must be aware of possible problems associated with the devices and prevent their
occurrence. Typical system malfunctions are described below.
a. Fabric Filters
A decrease in the control efficiency of fabric filters maybe caused in several ways:
tears in the bags; excess emission generation from the control device outlet; and plugging of the
bags. In addition, operating problems may lead to the interruption or inefficient operation of the
control device.
Bag blinding problems have often been observed in very humid areas, but similar
problems are also seen in cooler climates. In cooler climates, bag blinding may result from
ducting the elevator exhaust stream, generated from the handling of warm, moist grain, to a
control device located outside in a cooler environment. Bag blinding may be diminished by
using baghouse heating systems and cleaning the bags before ceasing operation of the system.
Dust bridging in the baghouse hopper, caused by poor hopper design or faulty shutdown
methods, can be diminished by designing the system to allow elevator personnel to easily access
the hopper for inspection and cleaning. Malfunction of the bag cleaning mechanism may cause
dust to build up on the bags, ultimately leading to the plugging of the systems.
In some operations, the pulse-jet control panel sits on the top of an outdoor baghouse
unprotected. Dust and moisture collecting inside the control panel may cause the solenoid valves
to short circuit, resulting in failure of the system. This problem may be reduced by practicing
appropriate general operation and maintenance procedures.
Since the emissions from several grain handling and processing operations are controlled
by one air pollution control system, excess emissions may result from improper design and
operation of the ventilation system connecting the source to the control system. [(1), p. 527-8]
b. Cyclone
The control efficiency of the cyclone is based upon design parameters and the velocity
of the gas stream passing through the device. Reduced gas velocities, resulting from plugging
in the cyclone, improper damper settings in the ductwork, or plugging in the ductwork that cause
an increased pressure drop through the system, lead to a decrease in cyclone control efficiency.
A common problem is air leaking into the cyclone from the dust discharge; this problem may be
alleviated through routine checks of the dust discharge mechanisms. Routine inspections of the
system identify problems that may lead to a reduction in control efficiency. Such examinations
include a review of the cyclone pressure drop, the exhaust fan current, the condition of the
cyclone walls and fan blades, and the exhaust rate at the pickup points. [(1), p. 527]
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CHAPTER 5
CONTROL TECHNOLOGY COSTS
A. INTRODUCTION
In this chapter the costs of oil application systems and conventional control devices to
control dust at grain elevators are discussed and compared. Most costs presented in this chapter
were obtained either from the literature or from price quotes (or price sheets) prepared by
vendors of oil application equipment or oil. (One set of cost numbers was obtained from an EPA
report entitled Standards Support and Environmental Impact Statement Volume 1: Proposed
Standards of Performance for Grain Elevator Industry.) The comparative cost analysis presented
at the end of this chapter was prepared by a vendor of oil application equipment.
B. OIL APPLICATION SYSTEMS FOR DUST SUPPRESSION
The cost of installing and operating an oil application system depends on the local
conditions and the availability of oil and equipment. The average installation cost in 1989 was
$1000-$3000. According to a study conducted at Texas A & M University in 1985, a basic
system should cost less than $5,000, with more complex self-monitoring systems ranging from
$8,000-$ 10,000 [17]. A representative from InterSystems, Incorporated in Omaha, Nebraska
indicated that current prices for the company's inclusive dust suppression system, the Dustop,
range from $4,000 and up depending on the amount of oil required, which is based on the
throughput and size of the grain elevator. Since grain handling operations vary among the
different elevators, the oil application system must be custom fit to serve the particular needs of
the grain elevator, thereby generating different cost estimates. The sections that follow present
various cost estimates for oil application systems as provided by different vendors [20].
1. Cost Analyses for Oil Application Systems
Information obtained from price sheets and price quotes prepared by several vendors of
oil application systems are summarized in this section. For more detailed cost numbers, refer to
Appendix B.
a. Analysis by Morrison Oil Company
Based on 1992 figures compiled by the Morrison Oil Company (a seller of white mineral
oil to the grain handling industry), installation costs for an oil system supplying a 7,000,000
bushel/year elevator include about $6,400 for equipment, a 7,600-gallon bulk storage tank, and
installation labor. Annual operating costs for such an elevator are about $24,700; over 90% of
this amount is for the cost of oil [(10), p. 1-2]. Details of these costs and the assumptions used
are presented in Appendix B-l.
Morrison Oil believes it is possible to recover the cost of the oil used. If the weight of
the oil is sold as grain, 10,500 gallons at 7.2 pounds per gallon equals 75,600 pounds or 1,260
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bushels at 60 Ib/bushel. At $2.70/bushel, this selling of the oil as grain translates to a value of
$3,402. In addition, assuming a handling loss of 0.14% (as reported by ASA) on 7,000,000
bushels, a loss of 9,800 bushels is realized. Assuming that 75% of the loss from a single
handling is dust, this equals 7,350 bushels per handle per year. With the application of oil, this
dust is now retained by the grain stream and can be sold as grain for $19,845, again using the
$2.70/bushel figure. The total revenue recovered from selling the oil and dust as grain is,
therefore, $23,247. Considering electricity, depreciation, repairs, and the cost of recovery
described above, the net annual operating cost for this oil application system is $1,428 [(10), p.
4].
b. Analysis for Arco Prime DS Oil
A cost analysis was performed for an oil application system using the naphthenic-based,
low-viscosity, food-grade white mineral oil Arco Prime DS, based on May 1987 average grain
prices for wheat ($2.90/bushel), corn ($1.90/bushel), and soybeans ($5.60/bushel), and a $10/ton
market value for dust. This evaluation assumed an annual throughput of 10,000,000 bushels for
each grain type and a consumption of 15,000 gallons of oil for each type of grain processed.
Calculations incorporated the cost of the oil and the selling of the oil and dust as grain, but
equipment costs were not included. For wheat, the net cost of treating with oil was $1,925 or
$0.0002/bushel; for corn, the net cost was $13,675, or $0.0014/bushel; but a net savings of
$29,800, or $0.003/bushel was computed for soybeans [21].
c. Analysis by Phoenix Park Systems1
Phoenix Park Systems, a manufacturer of oil application equipment in Wenona, Illinois,
advertises three models. The first, which has one point of application (spray head), costs roughly
$5,000 when fully equipped. The second, which has two application points, costs about $7,400
fully equipped. The third model has three application points and costs about $9,900 fully
equipped. These costs exclude the cost of storage tanks and oil, and appear to exclude labor
costs [8]. (All costs are in 1992 dollars.) Details of these costs are found in Appendix B-2.
2. Oil Application System Costs for Existing Elevators
The following are cost outlays for oil application systems installed at existing grain
elevators.
a. Avon Grain Company1
The Avon Grain Company in Carlisle, Iowa installed an oil application system in 1984
at a cost of $10,000 ($11,100 in 1992 dollars2), which included an 8,000-gallon tank. This
system included electric in-line heaters to heat the oil to 70°F at the point of application. An
1 The capacity and the throughput of the grain elevator were not indicated.
2 Dollars normalized to 1992 values using Plant Cost Indices published by Chemical Engineering, McGraw-Hill,
Inc., New York, NY,
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annual savings of $30,000 ($33,300 in 1992 dollars) was calculated when compared to the
maintenance and operating costs of running the elevators existing 13 pneumatic dust fans3 [(22),
p. 6, 7].
b. Heartland Co-op*
The Heartland Co-op in Minburn, Iowa procured a Dustop system in 1987 which included
a pump and heater contained in a 3 ft x IVi ft cabinet for less than $4,000 ($4,425 in 1992
dollars) [(22), p. 7].
3. Oil Costs
Once the equipment has been installed, the main expenditure is for the oil. In the United
States the oil selected depends on the market price. The prices of soybean and mineral oil
fluctuate, usually in opposition, depending on the soybean and petroleum markets. To exhibit
a loyalty to their patrons, elevators processing soybeans often use soybean oil.
The most economical means of purchasing oil is in bulk from a tanker truck, but for small
facilities using smaller amounts of oil annually, buying the oil in separate barrels is more
practical. The average cost of applying paraffinic oil to grain is approximately $0.003 -
0.005/bushel [8]. Including shipping and handling, the cost of oil obtained from bulk shipments
could be near $0.86/L ($3.25/gal), while oil purchased in barrels may cost up to $1.59/L
($6.00/gal) [(14), p. 10].
C. CONVENTIONAL CONTROLS
1. Cost Analyses for Conventional Controls
Although conventional control systems are effective, the installation, operation, and
maintenance costs are high. Researchers in 1982 found that the investment costs of dust control
systems range from $144,500-$229,000 ($164,800-$261,200 in 1992 dollars) for elevators with
an annual throughput up to 63.4 x 104 m3 (18 million bushels) and may exceed $700,000
($798,500 in 1992 dollars) for larger elevators, which may handle this amount of grain in one
month. The capital cost of a new dust control system is estimated at $5-$ 107 cfm of air
controlled. Operating expenses include electrical power consumption, demand charges, and
maintenance expense. Pneumatic systems (baghouses) must be inspected and serviced daily, and
demand charges vary within the industry because they are based on peak power consumption
[14].5
3 No calculations were provided to substantiate this savings estimate.
4 The capacity and the throughput of the grain elevator were not indicated.
5 These costs only represent control device costs, excluding capture system costs.
5-3
-------
A typical baghouse system installed on a 10' by 12' receiving pit will cost $40,000 to
$55,000 ($45,600-$62,700 in 1992 dollars), excluding pit construction costs. When designing
such a system, the following elements must be considered:
• Adequate room around the receiving pit must be reserved for aspiration equipment.
• To ensure efficient operation, the pit hopper must be properly designed.
• The method to be used by the elevator for returning dust to the grain must be identified,
since most systems reintroduce the dust collected by the controls to the grain stream.
• The pit area should be minimized to handle vehicles delivering grain to the elevator, but
the capacity should be large enough so that the grain remains below the bar grating. The
smaller the area, the lower the system's air requirements and subsequent investment costs.
The two types of collectors include cloth bag filters and cyclones. However, the use of cyclones
has decreased since they do not meet clean-air standards, grain can be lost, and visible emissions
have been a problem. For most elevators, the bag filter is the preferred aspiration control for the
receiving pit. The use of fans with either control ensures a more stable operation of the system
and longer equipment life [23].
In 1977, as part of EPA's proposed standards of performance for the grain elevator
industry, extensive cost estimates were made for conventional control technologies. It is not
possible to summarize all of EPA's findings because of the many scenarios that were analyzed;
however, EPA compiled capital and annualized costs for the best control technology for all grain
processors. The characteristics for the grain processors model plant considered the following
throughputs (million bushels/year) for the various grain types handled: 2.78 for wheat, 10 for wet
corn, 2.88 for rice, 3.35 for dry corn, or 11.10 for soybean. The agency found that the total
investment requirements for grain processors were $248,800 ($649,500 in 1992 dollars), and
annual operating costs were $71,600 ($186,900 in 1992 dollars) [2].
D. COST COMPARISON - OIL APPLICATION AND CONVENTIONAL CONTROLS
1. Cost Simulation
In 1985, a systems engineering simulation was developed at Texas A&M University to
estimate the costs of ventilation dust control systems (fabric filters) and oil application systems.
The grain operations were identified as grain unloading, storing, conveying, loading, and dust
handling. For the model, the system was split into three major subsystems: grain receiving, grain
loading, and dust collection while conveying. The arrivals and departures of grain at an elevator
were modeled and the annual grain throughput was related to energy consumption based on
equipment capacities, efficiencies, and operational characteristics. The dust control system was
running during any grain movement [14].
The following variables served as simulation inputs: annual grain throughput, elevator
leg capacities, associated dust control ventilation horsepowers, investment cost of dust control
5-4
-------
equipment, turnover rate, dust control operating time as a multiple of leg time, oil application
level, cost of oil per liter, kilowatt-hour electrical energy rate, and power demand charge. Table
5-1 provides the elevator operating levels, equipment capacities, and investment costs used in the
simulation.
TABLE 5-1: Operating Characteristics and Investment Cost of Model Elevators [(14), p.l 1]
Annual
Throughput
(million bu)
1
5
10
18
25
40
Leg
Capacity
(thous. bu/h)
20
30
40
80
85
140
Dust
Control
(hp)
180
188
235
440
465
680
Dust Control
Investment
Cost($)
144,500
157,500
223,000
229,000
300,000
700,000
Annual
Fixed Cost
(S/thous. bu)'
20.01
4.36
3.09
1.76
1.66
2.42
a Annual Fixed cost assumed to be 13.85% of initial investment, including depreciation, interest on investment,
insurance, and taxes.
The results of the simulation using the model elevator characteristics given in Table 5-1 and
controlled by a conventional dust control system are provided in Table 5-2.
TABLE 5-2: Simulation Results - Conventional Dust Control [14, p.l 1]
Throughput
(10* bu/yr)
0.9
5.6
10.7
18.1
25.2
41.2
Dust*
Collected
(tons)
97.9
665.0
1205.9
2126.3
2969.0
4851.2
Revenue1*
Lost as
Dust ($)
9,071
61,678
115,899
197,006
275,703
449,480
Foreign1
Matter
Cost
(Vthous. bu)
10.08
11.01
10.83
10.86
10.94
10.91
Electricity"
Cost
(S/thous. bu)
7.65
3.00
2.63
2.90
2.70
2.43
Total
Cost
($/thou& bo)
37.7
18.4
16.6
15.5
15.3
13.3
The dust collected was assumed to be 0.4% of the annual throughput.
The revenue lost as dust was calculated at a rate of $2.55 per bushel.
The foreign matter cost was calculated by dividing revenue lost as dust by the annual throughput
The electrical cost includes demand charges (assumed as a power factor of five times the combined load of 3-4
elevator leg dust-control systems) and an electricity rate of $0.10 per kWh.
The total cost includes annual fixed cost (Table 5-1), variable cost (electricity cost), and foreign matter losses.
5-5
-------
The results of the simulation using the model elevator characteristics given in Table 5-1 and
controlled by an oil application system are provided in Table 5-3.
TABLE 5-3: Simulation Results - Oil Application Systems [14, p.l 1]
Throughput
(10* butyr)
0.9
5.6
10.7
18.1
25.2
41.2
Oil
Used
(gallons/yr)
1744
8692
16,830
28,322
38,388
62,850
Storage
Capacity
(gallons)
555
2721
5258
8851
11,995
19,656
Investment*
Cost
($)
2957
3385
3886
4593
5214
6720
Total"
Cost
(Vinous, bu)
5.71
5.11
5.11
5.11
5.11
5.11
The investment cost was estimated at $1200 for basic oil application equipment including installation and
storage costs. The basic system consisted of a pump, regulator, spray nozzle, and connecting lines. The storage
costs were based on tank capacity, which was assumed to be one quarter of the annual use, plus 25% excess
capacity.
The total cost includes electrical energy, maintenance (3% of the initial investment), interest, depreciation, taxes
on investments, and oil purchased at $3.50 per gallon.
It is not clear why the total cost per thousand bushels remains constant for all systems above
900,000 bushels throughput capacity. Perhaps the additional revenue recovered from selling dust
and oil as grain offsets the increased cost of oil storage and usage.
The difference in cost between operating a conventional dust control system and an oil
application system is provided in Table 5-4 below.
TABLE 5-4: Difference in Cost for Controls [14, p.l 1]
Throughput
(10* bu/year)
0.9
5.6
10.7
18.1
25.2
41.2
Conventional Dust Control
Total Cost
($/thousand bu)
37.7
18.4
16.6
15.5
15.3
13.3
Oil Application System
Total Cost
(I/thousand bu)
5.71
5.11
5.11
5.11
5.11
5.11
Net
Savings
($/thousand bu)
31.99
13.29
11.49
10.39
10.19
8.19
5-6
-------
This simulation illustrates the net savings realized when using an oil application system as
opposed to a conventional dust control system. As shown in Table 5-4, greater economic
benefits are yielded for smaller grain elevators. In the gram handling and processing industry,
the various grain elevators have unique equipment layouts which may prevent application of the
oil early in the process. For these situations, conventional dust-control systems may have to be
used hi conjunction with the oil application system, but the application of oil may enable the
conventional controls to be shut off for part of the elevator's operation time [(14), p. 11].
2. Comparison Cost Analysis
Costs provided by two companies have been compared and summarized here. The first
is a comparison between an oil application system and a baghouse; the second is a cost
comparison among options to repair an existing conventional control system, renovate the system,
or purchase an oil application system.
a. Lyondell Petrochemical Co.
The following comparative economic analysis between an oil application system and a
baghouse was performed in 1991 by Lyondell, a manufacturer of white grade mineral oil.
Lyondell estimated capital investment for an oil application system at $11,500, and annual
operating costs of $37,500 for a system on an elevator with a capacity of 8 million bushels per
year. For a system on an elevator with a 12 million bushels/year capacity, the operating cost
increased to $55,500.
Lyondell calculated operating costs for a baghouse. The annual operating costs for an oil
application system were subtracted from those for the baghouse. (Lyondell provided no
supporting documentation.) This resulted in an operating cost savings of almost $43,000 per
year. Further, Lyondell calculated the savings from capturing the dust and selling it as grain to
be about $31,200 for the 8 million bushel/year system, and $46,100 for the 12 million bushel/year
system. The net annual benefits of operating an oil application system were calculated by
Lyondell to be in excess of $30,000 [20]. Appendix B-3 details these calculations.
b. A Midwest Elevator Company
An unnamed Midwest elevator company performed a cost analysis to decide whether to
repair or renovate its existing control system which included 11 cyclones, 13 fans, and a dust bin,
or treat the grain with oil application.6 Table 5-5 presents cost figures that apply to the
elevator's options, and are hi 1987 dollars:
6 The capacity and the throughput of the grain elevator were not indicated.
5-7
-------
TABLE 5-5: Midwest Elevator Company Cost Analysis [9]
ITEM
COST
Installation/
Capital
Annual Operating
TOTAL
REPAIR
Mend cyclone holes
Replace some cones
Replace two cones
$63,000
$100,000
$163,000
RENOVATE
Install filter/baghouses
Install pneumatic system
$290,000
$100,000
$390,000
OIL APPLICATION
SYSTEM
Continue air aspiration at
receiving pit
Shut down mechanical
devices
Install oil application
system
$40,000
$90,000 (oil costs)
$130,000
Based on these figures, the company determined that the installation of an oil application system
could save them $30,000-$260,000 [9].
5-8
-------
CHAPTER 6
CONCLUSIONS
Title V of the Clean Air Act Amendments of 1990 requires each State to develop and
implement an operating permits program containing the elements outlined in 40 CFR Part 70.
Pursuant to this program, sources will be required to pay operating fees based on the amount of
pollutants emitted. In addition, stricter dust regulations and safety standards for grain elevators
have been developed by the federal government. Many large companies have already
implemented the equipment and operating procedures required by the new regulations, but smaller
facilities that do not use mechanical dust control equipment may find oil application to be cost
effective. Regulatory requirements and permitting costs have heightened industry's desire to use
economical and efficient dust control methods and have increased interest in the use of oil
application at grain handling facilities.
According to tests conducted by the U.S. Department of Agriculture and Texas A&M, oil
application systems achieved control efficiencies comparable to those achieved by conventional
controls (cyclones, and baghouses). Fabric filters demonstrate efficiencies higher than 99%;
cyclones achieve efficiencies within the range of 85-99%; and the oil application system
demonstrated high-end control efficiencies ranging from 85-98%, depending on the type of grain
and the location tested. Average levels of dust reduction for all test locations and all grains
ranged from 62% to 78%, while the average levels for the best controlled locations for each grain
ranged from 72% to 91%. The gallery open belt was the best controlled location for three of the
four grain-oil combinations tested, with dust reduction levels of 77%, 88%, and 91% achieved.
Although these tests indicate a promising technology, EPA has concluded that these tests are
inadequate for the purpose of determining emission factors for the application of oil suppression
technology. As a result, the CTC is pursuing additional testing.
When compared to conventional controls, the operating and equipment costs of the oil
application system appear to be significantly lower. Energy consumption of the oil system is
negligible when compared to conventional controls, and the system requires little or no
maintenance. As illustrated by analyses made by different vendors supplying the equipment and
oil, thousands of dollars may be saved when using an oil application to control grain dust
emissions. The oil application system seems to be an attractive alternative for smaller elevators
that may not be able to afford installing expensive conventional controls.
The advantages of using oil application to suppress dust emissions are numerous. Since
the dust remains entrained in the grain, housekeeping and dust disposal costs are reduced. There
is less weight loss with each handling, and the dust attached to the grain surface can be sold as
grain. Therefore, instead of paying to remove the dust from the elevator, the dust can now be
sold. The use of oil may also extend the life of the equipment operating in the elevator since
reduced dust contamination translates to cleaner moving parts. In addition, the decrease in
6-1
-------
airborne dust improves the safety of the working environment by reducing the possibility of a
grain elevator explosion.
The main disadvantage with the oil system is the market response to oil-treated grain.
Although studies have demonstrated no significant effects on the quality of the grain, grain
exporters are hesitant to purchase grain from an elevator using this control method because the
acceptance of this method worldwide is not certain. Foreign markets are demanding grain based
on higher quality standards, so exporters do not want to risk buying grain that may not be
sellable. When compared to conventional controls, the application of oil for dust control is fairly
new, with implementation occurring within the past decade. Once this uncertainty regarding the
effect oil has on grain quality is resolved through additional testing, the main obstacle for this
control system should be surmounted. Based on efficiency, economic, and safety factors, the oil
application system appears to be an appealing technology for the grain handling industry.
6-2
-------
REFERENCES
1. Anthony J. Buonicore and Wayne T. Davis, Air Pollution Engineering Manual. Air
Pollution and Waste Management Association, (New York, 1992): pp. 517-528.
2. U.S. Environmental Protection Agency, Standards Support and Environmental Impact
Statement Volume 1: Proposed Standards of Performance for Grain Elevator Industry,
(Research Triangle Park, North Carolina, January 1977). EPA-450/2-77-001a.
3. U.S. Environmental Protection Agency, Review of New Source Performance Standards
for Grain Elevators, (Research Triangle Park, North Carolina, January 1984).
EPA-450/3-84-001.
4. Susan K. Robinson, "Edible Oils Prove Value As Dust Suppressants," Agribusiness
Worldwide April 1989: 12-17.
5. Rudolph M. Morawek, "White Oil Treatments for Grain Dedusting Are Here," Grain Age
March/April 1989: 5.
6. BJ. Lesikan, C.B. Parnell, Jr., and H.D. Wardlaw, Jr., "Dust Suppression Results with
Mineral Oil Applications for Com and Milo," International Winter Meeting of the
American Society of Agricultural Engineers, 15-18 December 1987.
7. Susan Robinson, "Dust Suppression With Oil," World Grain January/February 1989:8-13.
8. Phoenix Park Systems, (Cost analysis performed in 1990), Wenona, Illinois.
9. Gary L. Everett, Effective Dust Suppression Using Mineral Oil, (Texas, February 25,
1987).
10. Morrison Oil Company, (Cost analysis performed hi 1992).
11. Fang S. Lai, Charles R. Martin, and Byron S. Miller, Examining the Use of Additives to
Control Grain Dust, National Grain and Feed Association Fire and Explosion Research
Report (Manhattan, Kansas: U.S. Department of Agriculture / U.S. Grain Marketing
Research Laboratory, 1982).
12. David Jones, "Oil Additives to Reduce Grain Dust," NebGuide April 1990.
13. Ray Vrtiska, "Suppressing Dust with Oil-A Close Look,"
14. K.J. Goforth, D.D. Jones, and C.B. Parnell, Jr., "Using Oil Additive for Grain Dust
Control," Agricultural Engineering September 1985: 9-12.
R-l
-------
15. Lyondell Petrochemical Company, "Information About the Hardware Involved in the Use
of Food Grade Mineral Oil for Dust Suppression," Inflo-Topics in Lubricant Technology,
1-3.
16. Tom Hegadorn, "Dust Control-Options Update", 46-48.
17. Kerry James Goforth, "Systems Simulation of Oil Additives to Grain at Terminal
Elevators," diss., Texas A & M University, May 1985.
18. Ray Vrtiska, "Dust Suppression Gains Acceptance," Grain Digest.
19. Robert M. Frye, "Grain Handling and Storage-Dust Disposal Challenge: Who You Gonna
Call? Dust Busters?," 181-183.
20. Lyondell Petrochemical Company / Lubricants, Cost analysis performed in 1991.
21. Lyondell Petrochemical Company, Economic Considerations of Grain Dust Control with
Mineral Oil (Cost analysis performed 1983-5), Houston, Texas.
22. Farmland Insurance Companies, "Grain Facilities Discover Oil," Foresight May/June
1988: 6-11.
23. "Controlling Grain Dust Can be a Challenge," Feed and Grain June/July 1991: 18-19.
R-2
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This Page Intentionally Left Blank
-------
Table 1. Percentage reduction in dust concentration for experimental lots
of soybeans treated with soybean oil as an additive
Level of
additive
0.03
0.03
0.03
0.06
Dust control
system
on
off
off
off
Pre-leg enclosed
belt dust
concentration
76.3
65.6
1.8'
25.6
Gallery open
belt dust
concentration
70.6
97.2
91.3
92.6
Drop test dust
concentration
98.6
97.3
85.1
97.3
Bin overspace
enclosed dust
concentration
88.2
89.5
66.7
89.2
Since this value is extremely low compared to the other results, it is assumed that a malfunction occurred during
testing. No explanation was given as to why this number was obtained.
Table 2. Percentage reduction in dust concentration for experimental lots
of wheat treated with soybean oil as an additive
Level of
additive
%
0.02
0.02
0.03
0.03
0.03
0.06
0.06
Dust control
system
off
off
on
off
off
off
off
Pre-leg enclosed
belt dust
concentration
%
63.3
-156.2
21.3
44.0
37.6
43.1
55.1
Gallery open
belt dust
concentration
%
77.0
-604.0
28.6
75.0
60.0
71.0
64.0
Drop test dust
concentration
%
95.9
-987.7
94.2
95.9
90.4
95.9
95.9
Bin overspace
enclosed dust
concentration
%
70.7
6.5
50.9
85.2
82.7
85.1
89.3
Since these values are not valid reduction percentages, it is assumed that a malfunction occurred during testing.
No explanation was given as to why these numbers were obtained.
A-l
-------
Table 3. Percentage reduction in dust concentration for experimental lots
of corn treated with mineral oil as an additive
Level of
additive
%
0.02
0.02
0.04
0.08
Dust control
system
on
off
off
off
Pre-leg enclosed
belt dost
concentration
%
31.0
55.8
62.2
56.7
Gallery open
belt dust
concentration
%
73.3
96.7
95.7
98.2
Drop test dust
concentration
%
95.9
97.5
98.8
97.5
Bin overspace
enclosed dust
concentration
%
79.6
69.1
86.4
87.7
Table 4. Percentage reduction in dust concentration for experimental lots
of corn treated with soybean oil as an additive
Level of
additive
%
0.03
0.06
0.10
0.03
0.06
0.10
0.06'
Dust control
system
on
on
on
off
off
off
off
Pre-leg enclosed
belt dust
concentration
%
17.2
23.0
13.3
42.0
29.1
40.5
94.6
Gallery open
belt dust
concentration
%
46.7
20.0
60.0
93.8
95.4
94.3
92.5
Drop test dust
concentration
%
97.4
98.5
98.9
98.0
98.3
99.3
99.3
Bin overspace
enclosed dust
concentration
%
70.9
82.6
72.5
77.6
81.5
73.7
77.4
Top sprayer on only.
Dust control system on at pre-leg belt only.
A-2
-------
-------
APPENDIX B-l
ANALYSIS BY MORRISON OIL COMPANY
Installation costs for an oil system include:
Dustop n (factory assembled system consisting of the following equipment:
pump, flow regulators, relief valves, gauges, filters, control, solenoid switches,
nozzles, and plumbing for 2 legs) $3,505
7600 gallon bulk storage tank $2,361
Installation Labor $500
Total Installation Cost $ 6,366
The annual operating cost analysis provided below includes the cost of the oil, electric power for
the pump, and maintenance costs [11, p. 2]:
Electricity $200
Depreciation $1,275
Oil $23,100
Repairs $100
Total Annual Operating Cost $24,675
These operating expenses were calculated using the following assumptions:
• the elevator handles 7,000,000 bushels per year;
• an installation cost of $6,366 based on a 5-year straight line depreciation; and
• the mineral oil is applied at Wi gallons/1,000 bushels at $2.25/gallon (which
translates to 1/3 of a cent/bushel).
B-l
-------
APPENDIX B-2
ANALYSIS BY PHOENIX PARK SYSTEMS
The following cost figures were assembled by Phoenix Park Systems in Wenona, Illinois in 1990
for the various oil application system products it sells.
1. The Phoenix Park Base Unit With Heater (Model 1-DI), costing $4,235, consists of:
Base Pump Module: 1A HP motor/pump unit, flow meter, flow control, "auto-off-
manual" mode switch, keyed power switch with indicator light, pump run light,
depressurization mode light, 8 amp pop-out circuit breaker, 115 volt single phase.
Heat Module: flow-through heater with thermostatic control, circuit breaker; on-off
indicator lights for power on and thermostat operation, face-mounted thermometer with
0-180°F range.
Spray Head: one spray nozzle complete with screen, 7 psi check valve and 18" flex
connector for 3/8" line.
2. The Phoenix Park Two Application Point Unit (Model 2-DI) consists of two base pump
modules and one heater module stacked with two spray heads, as described in the base
unit (Model 1-DI). This system costs $6,160.
3. The Phoenix Park Three Application Point Unit (Model 3-DI) consists of three base pump
modules and one heater module stacked with three spray heads. This system costs
$8,250.
Additional miscellaneous equipment may be purchased as needed. Such parts include spray tips
for the oil, a spray stand for belt conveyors, an explosion-proof paddle switch (which detects the
presence of grain flow on the belt conveyor and starts and stops the application of oil), tape, an
explosion-proof thermostat, and an ammeter relay. The price of add-on equipment ranges from
$5 for the spray tips to $468 for the ammeter relay. Table 1 provides the prices for bulk storage
tanks.
These cost figures apply to storage tanks made of carbon steel, vertical with 2" tee vent, 20"
loose cover roof manhole, 18" shell manhole, 3" mild steel outlet, 1" sight gauge outlets, 3" up
fill and tank tie-downs. The interior is sand blasted and coated with food grade epoxy and the
exterior is coated with primer. Polyethylene or fiberglass tanks are also available.
B-2
-------
TABLE 1: Storage Tank Costs
Capacity (Gallons)
500
1000
2000
4100
6000
8250
10000
Dimensions
48" x 64"
48" x 128"
64" x 144"
8'x 11'
8' x 16'
8' x 22'
ll'x 14'
Price
$1,145.35
$1,748.00
$2465.35
$3,813.35
$4,766.70
$5,677.35
$6,218.70
Costs for a typical oil-application system are as follows:
1. A system with one application point consists of the following equipment:
Model 1-DI $4,235.00
Spray Lance (1) 76.00
Amp Relay (1) 196.50
100' PVC Pipe and fittings 35.00
100' Closed cell insulation 21.00
400.00
4,963.50
Wiring
This system requires 24-36 man hours to install.
2. A system with two application points consists of the following equipment:
Model 2-DI $6,160.00
Spray Lance (2) 152.00
Amp Relay (2) 393.00
100' PVC Pipe and fittings 70.00
100' Closed cell insulation 42.00
590.00
Wiring
This system requires 36-48 man hours to install.
$7,407.00
B-3
-------
3. A system with three application points consists of the following equipment:
Model 3-DI $8,250.00
Spray Lance (3) 228.00
Amp Relay (3) 589.50
100' PVC Pipe and fittings 85.00
100' Closed cell insulation 65.00
Wiring 650.00
$9867.50
This system requires 48-72 man hours to install.
The system costs provided for the three cases above will increase depending upon the storage
tank size selected by the elevator operator, if a storage tank is used. Small elevators may elect
to purchase the oil in barrels, thereby eliminating the need for a storage tank. These figures
apply to equipment costs only and do not include the price of the oil [10].
B-4
-------
APPENDIX B-3
COMPARATIVE ANALYSIS BY LYONDELL
The following comparative economic analysis between an oil application system and a
baghouse was performed by Lyondell, a manufacturer of white grade mineral oil. The
components of the cost of a food-grade mineral oil system include items in (i), below.
(i) Capital Investment:
Tank and pad $4,000
Installation labor $2,000
Electric controls, nozzles, regulators, etc $3,000
Pump and power unit $1,500
Plumbing $1.000
Total $11,500
(ii) Operating Costs:
8 million bu/yr
Fixed costs
Depreciation cost $733
Interest cost $690
Variable costs
Maintenance cost $150
Mineral oil cost $35.937
Total $37^10
12 million bu/yr
Fixed costs
Depreciation cost $733
Interest cost $690
Variable costs
Maintenance cost $150
Mineral oil cost $53.905
Total $55,478
B-5
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(Hi) Operating Cost Savings Analysis:
Lyondell calculated operating costs for a baghouse. The operating costs for an oil
application system were subtracted from those for the baghouse. The results are as follows:
Electrical energy $16,650
Labor $20,080
System maintenance $3,550
Daily check $2.510
Total $42,790
(iv) Dust Capture Savings Analysis:
The dust capture savings were estimated to be $31,210 for an 8 million bu/yr system and
$46,090 for an elevator handling 12 million bu/yr, based on selling the dust as grain using the
following equation:
Dust Capture Savings = (Number of Bushels) x (Dust % Weight Loss) x (Cost/Bushel) x 75%
The following assumptions were made:
Wheat sold at $4.00/bushel
Oil Recovers 75% dust
Shrink/handling loss ranges from 0.10%-0.20%
(ASA indicated a shrink loss of 0.14% for each handling)
Based on the figures above, the annual savings realized when operating a mineral oil system
instead of a baghouse are [20]:
8 million bu/vr 12 million bu/vr
Mineral Oil System Cost
Savings over Pneumatic System
Dust Capture Savings
Net Mineral Oil System Savings
- $37,510
+ $42,790
+ $31.210
+ $36,490
- $55,478
+ $42,790
+ $46.090
+ $33,402
B-6
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TECHNICAL REPORT DATA
(Please read Instructions on the rcrenc before completing)
. REPORT NO.
EPA-453/R-94-049
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
Oil Suppression of Particulate Matter at Grain
Elevators
5. REPORT DATE
July 1994
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
R. Chettri and J. Phillips
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
ViGYAN, Inc.
5203 Leesburg Pike, Suite 900
Falls Church, Va. 22041-3406
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
68-01-0073, WA 1-34
12. SPONSORING AGENCY NAME AND ADDRESS
Control Technology Center (MD-13)
U.S. EPA, Office of Air Quality Planning and Standards
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
OAQPS project lead is Robert Blaszczak, MD-13, (919) 541-0800.
sponsored by the Air and Energy Engineering Laboratory, ORD.
The CTC is also
16. ABSTRACT
The Nebraska Department of Environmental Control (NE DEC) requested assistance
from EPA s Control Technology Center (CTC) in the evaluation of oil suppression
technology to control particulate matter (PM) emissions from grain elevators.
Grain elevators act as intermediate storage and transfer points for grain as it
is transported from the farms to the market. The operations performed at elevators,
including receiving, handling and transfer, drying, loading and shipping, generate
emissions of PM in the fora of grain dust, which is the pollutant of concern at
elevators. The basic oil suppression system applies a fine spray of edible oil to the
grain stream to coat the grain surface. The dust adheres to the oil on the grain,
thereby decreasing the amount of airborne dust.
This report evaluates oil suppression systems and compares their cost and
effectiveness to those of existing conventional controls used by elevators,
specifically fabric filters and cyclones.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COSATi Held/Group
Grain elevator
Particulate matter
Mineral oil
Pollution
Pollution control
Stationary source
18. DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS (Tliii Rc
Unclassified
21. N-O. or PAGES
56
20. SECURITY CLASS il
\ Unclassified
•).. PRICE
EPA Form 2220-1 (R«v. 4-77)
PREVIOUS EDITION is oesoi-ti c
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