oEPA
United States
Environmental Protection
Agency
Office of Air Quality
Planning and Standards
Research Triangle Park NC 27711
EPA-450/3-84-001
January 1984
Air
of New
Source Performance
Standards for
Grain Elevators
-------
EPA-450/3-84-001
Review of New Source Performance
for
Grain Elevators
Emission Standards and Engineering Division
U.S ENVIRONMENTAL PROTECTION AGENCY
Office of Air and Radiation
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
January 1984
-------
This report has been reviewed by the Emission Standards and Engineering Division of the Office of Air Quality Planning
and Standards, EPA, and approved for publication. Mention of trade names or commercial products is not intended to
constitute endorsement or recommendation for use. Copies of this report are available through the Library Services
Office (MD-35), U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711; or, for a fee, from
the National Technical Information Services, 5285 Port Royal Road, Springfield, Virginia 22161.
Publication No. EPA-450/3-84-001
-------
TABLE OF CONTENTS
Section Title Pa9e
1 EXECUTIVE SUMMARY '. 1-1
1.1 Best Demonstrated Control Technology 1-1
1.2 Economic Considerations Affecting the NSPS 1-2
1.3 Recommendations of Revision of Current NSPS 1-2
1.4 Recommendation on Extension to the NSPS 1-2
2 INDUSTRY STATUS 2-1
2.2 The Grain Elevator Industry 2-1
2.3 The Emission Problem 2-5
2.4 Grain Elevator Handling Facilities 2-7
2.4.1 Truck Receiving 2-8
2.4.2 Railcar Receiving 2-10
2.4.3 Barges 2-13
2.4.4 Grain Handling and Conveying Equipment 2-13
2.4.5 Grain Cleaning 2-15
2.4.6 Grain Drying 2-15
2.4.7 Loading 2-19
2.4.8 Ships 2-22
2.5 Selection of Grain Elevators for NSPS Control 2-25
References 2-27
3 CURRENT NSPS FOR THE GRAIN ELEVATOR INDUSTRY 3-1
3.1 Federal New Source Performance Standard 3-1
3.2 State Emission Limitations for Grain Elevators 3-2
References 3-5
-------
Section Title Page
4 STATUS OF CONTROL TECHNOLOGY 4-1
4.1 Particulate Control I 4-1
4.1.1 Receiving (Unloading) 4-4
4.1.2 Rail cars 4-8
4.1.3 Barges 4-12
4.1.4 Handling and Conveying Equipment 4-12
4.1.5 Loading 4-22
4.1.6 Rail cars 4-22
4.1.7 Barges 4-26
4.1.8 Ships 4-29
4.1.9 Potential New Control Technology 4-29
References 4-32
5 COMPLIANCE TEST RESULTS 5-1
5.1 Particul ate Emission Test Data 5-1
5.2 Visible Emissions 5-1
5.3 Other Atmospheric Emissions 5-2
5.4 Water and Solid Waste Emissions 5-2
References 5-4
6 COST ANALYSIS 6-1
6.1 Updated Costs for the Affected Facilities 6-1
6.1.1 Particulate Control 6~5
References 6~8
IV
-------
Section Title
7 ENFORCEMENT ASPECTS 7-1
8 ANALYSIS OF POSSIBLE REVISION TO THE STANDARDS 8-1
8.1 Possible Revision to NSPS 8-1
8.1.1 Truck Loading 8-1
8.1.2 Truck Unloading 8-2
8.1.3 Rail car Receiving 8-3
8.1.4 Railcar Unloading 8-3
8.1.5 Barge or Ship Unloading 8-4
8.1.6 Barge or Ship Loading 8-5
8.1.7 Grain Drying 8-8
8.1.8 Grain Handling 8-9
8.1.9 Control Devices 8-10
8.2 Possible Revisions to Monitoring Requirements 8-10
8.3 Extension to Other Sources 8-11
8.4 Extensions to Other Emissions 8-12
-------
LIST OF FIGURES
No. Title Page
2-1 Grain FT ow from Farm to Market : 2-4
2-2 Terminal Elevator 2-6
2-3 Truck Unloading Control System 2-9
2-4 Rail Car Receiving 2-11
2-5 Grain Cleaning 2-16
2-6 A Rack Grain Dryer 2-17
2-7 Column Grain Oryer 2-18
2-8 Truck and Railcar Loading 2-20
2-9 Barge and Ship Loading 2-23
4-1 Typical Fabric Filter Used by Grain Elevators 4-2
4-2 Truck Unloading Control System 4-5
4-3 Truck Grain Dump Facility 4-6
4-4 Beam and Baffle Detail 4-7
4-5 Railcar Unloading Control Systems 4-9
4-6 Boxcar Unloading Control System 4-11
4-7 Typical Barge Receiving Control System 4-13
4-8 Transfer Point Control System 4-15
4-9 El evator Leg 4-16
4-10 Grain Handling and Cleaning Dust Control System 4-18
4-11 A Rack Grain Dryer 4-20
4-12 Column Grain Dryer 4-21
4-13 Truck Loading Control System 4-23
VI
-------
LIST OF FIGURES (Continued)
No. Title Page
4-14 Retractabl e Spout Deadbox for Truck Load-out 4-24
4-15 Combination Deadbox with Suction Hood 4-25
4-16 Dust Control System for Boxcar Loading 4-27
4-17 Barge or Shiploading Dust Control System 4-28
vn
-------
LIST OF TABLES
No. Title Page
3-1 Typical State Process Weight Regulations for
Grain Elevators 3-4
5-1 Compl iance Test Data 5-3
6-1 Port Terminal Moderl Plant Control Devices, Air
Flows, and Costs 6-2
6-2 Capital Costs, Annualized Costs, and Cost Effectiveness 6-3
vn i
-------
1. EXECUTIVE SUMMARY
The new source performance standards (NSPS) for grain elevators were
promulgated by the Environmental Protection Agency (EPA) on August 3, 1978.
As specified in the Clean Air Act, the grain elevator NSPS applies only
to grain terminal elevators with permanent grain storage capacity of
2.5 million bushels or greater, and grain storage elevators (mills) with
permanent grain storage capacity of 1.0 million bushels or greater.
These standards affect the truck loading station, truck unloading station,
railcar loading station, railcar unloading station, ship loading station,
ship unloading station, barge loading station, barge unloading station, grain
dryer, grain handling operations, and emission control devices. Affected
facilities are those facilities which commenced construction or modification
after August 3, 1978.
The objective of this report is to review the NSPS for grain elevators
and to assess the need for revision on the basis of developments that have
occurred since the original NSPS was promulgated. The following paragraphs
summarize the results and conclusions of the review, as well as recommendations
with respect to EPA action in implementing any changes in the NSPS.
1.1 BEST DEMONSTRATED CONTROL TECHNOLOGY
The NSPS regulates particulate matter (PM) from the affected facilities
named above. The original PM standard was based on the use of baghouses.
No significant changes have occurred in control technology for the affected
l-i
-------
participate matter sources. Electrostatic precipitators (ESP's) cannot
be used because of explosion hazards. Scrubbers are not used because
of water and solid waste problems. Cyclones will not meet the NSPS.
Compliance test results, State and local control agency inspector
reports, and unofficial observations during plant visits in this review
show that all affected NSPS facilities are in compliance with the NSPS.
1.2 ECONOMIC CONSIDERATIONS AFFECTING THE NSPS
The capital and annualized costs for the control system for each
affected facility were estimated during the NSPS development. During
this review, those costs were updated to September 1982 dollars using the
Chemical Engineer's plant cost index. In addition, costs for the affected
facilities were revised based upon information supplied by industry and
vendors.
The cost-effectiveness for each affected facility was estimated from
the updated and revised costs and the emissions reduction resulting from
the application of the control techniques. No credits were taken in
these cost estimates for the recovered grain dust. The cost effectiveness
of the various affected facilities ranges from about $90 for the grain
dryer facility, to about $870 for the ship loading station.
Since the NSPS was promulgated, only six NSPS grain elevators have
started operation or been modified. The growth rate for grain production
has been about 14 percent per year between 1978-1981 but grain elevators
have been designed to handle more grain rather than to build new facilities,
1-2
-------
Since the Clean Air Act exemptions are based on storage capacity, facilities
may significantly increase handling rate without being regulated by the NSPS.
The forecast for growth is difficult to determine for the next few years
because of what happens in the world markets, government policies, and excess
supplies.
1.3 RECOMMENDATIONS OF REVISION OF CURRENT NSPS
There has been general compliance with the current NSPS, as reported
by State and local agencies, and the achievability of the existing standard
has been demonstrated. Based on information provided EPA during this
review, it is recommended that the basis for the NSPS remain unchanged.
1.4 RECOMMENDATION ON EXTENSION TO THE NSPS
Because there are not any other types of pollutants being emitted
for the grain elevator affected facilities, there will be no considerations
for extension of the NSPS to other processes or pollutants.
1-3
-------
2. INDUSTRY STATUS
2.1 Introduction
On August 3, 1978, the Environmental Protection Agency (EPA) promulgated
new source performance standards (NSPS) for the grain elevator industry. As
specified in the Clean Air Act, the grain elevator industry NSPS applies
only to grain terminal elevators with permanent storage capacity of 2.5 million
bushels or greater and grain storage elevators (mills) with permanent storage
capacity of 1.0 million bushels or greater. These standards established
emission limits and equipment specifications for and require testing and
reporting of particulate emissions from the various grain elevator processes
that were built or modified after August 3, 1978. The Clean Air Act Amendments
of 1977 require that the EPA Administrator review and, if appropriate, revise
such standards every 4 years [Section lll(b)(1)(B)].
This report represents the results of a review of the NSPS for the grain
elevator industry. The report covers recent and projected growth of the grain
elevator industry and describes any changes in process and control technology
since NSPS promulgation.
The review was conducted by reviewing recent literature on grain elevator
industry statistics, discussions with EPA Regional Offices and State and local
air pollution agencies, discussions with process and emission control equipment
vendors, visiting new or modified elevator facilities, and discussions with the
National Grain and Feed Association.
2.2 The Grain Elevator Industry
The grain elevator industry has not changed significantly since the
promulgation of NSPS in August 1978. There are fewer small country elevators
2-1
-------
in favor of larger storage or higher handling capacity elevators. Also,
because of sluggish or low farm prices, more grain is being stored on
farms.* Commentators, during the development of the NSPS, provided data to
estimate that about 200 elevators would come under NSPS regulation by 1982.2
However, this review indicates that only six grain elevator facilities and
no flour mills are required to meet the NSPS requirements. Industry sources
indicated in their questionnaire responses that the grain elevator industry
would be growing, but none could provide any definitive data on the industry's
growth over the next 5 years. However, a large constructor of grain elevators
estimated that for about 2 years the growth rate will be negligible until the
grain glut is resolved, then growth would increase at about 5 percent per
year.^
Grain elevator facilities are used to condition, handle, and store grain1/
as it moves from the farm to markets. In general, elevators are classed as
either "country" or "terminal." The U. S. Department of Agriculture (USDA)
distinguishes between country and terminal elevators on the basis that
terminals furnish official weights; that is, each receipt or shipment is
weighed under the supervision of a State inspector; however, not all terminal
elevators furnish official weights.
Country elevators generally receive grains as they are harvested in fields
within 10 to 20 miles or more of the elevator. They unload, weigh, and store
the grain and may dry or clean it before shipment to terminal elevators or
processors. Terminal elevators are classified into two groups, inland (or
T7Grain includes wheat, corn, oats, millet, soybeans, rice,
milo, and other similar products.
2-2
-------
subterminals) and port terminals. Inland terminal elevators receive most
of their grain from country elevators and ship to processors, other terminals,
and exporters. The primary functions of most inland terminal elevators are
to store grain in quantity and condition it to meet buyer's specifications.
They dry and clean grain, as country elevators do, but they also blend
different grades of grain.I/
Port terminals are defined as those located on major waterways or in
seaports which export agricultural products. The port terminal provides
the same basis functions as an inland terminal, but can load ships and barges.
Plants, which process grain in-house, also use elevators to receive and
store grain. These plants process grain into food or food intermediates for
human and animal consumption. All of the same basic functions are performed
at storage elevators owned by processors as at country or terminal elevators.
Rarely is grain shipped by processors.
About 85 percent of the grain sold by farms is handled by country
elevators before shipment to terminal elevators or grain processors. The
other 15 percent bypasses country elevators. This is possible largely
because improved roads, larger trucks, and more on-farm storage facilities
make it economical to ship directly to more distant terminal elevators and
processors. Figure 2-1 shows the flow of grains from the farm to market
and the number of grain elevators in operation in 1981.
Agricultural Stabilization and Conservation Service (ASCS) data show
that the average storage capacity of a country elevator is about 400-500,000
T7The USOA classifies each grain into six grade. No. 1 grade grains
must meet specific minimum test weights (pounds per bushel) and
maximum limits on the percent moisture, foreign material, damage, etc.
2-3
-------
NUMBER '
OF FACILITIES,
[V)
I
FARM
COUNTRY
ELEVATOR
INLAND
TERMINAL
EXPORT
TERMINAL
OR PROCESSOR
(10,000)
(413)
(82)
--
AND"
PROCESSING
' PLANTS
'TOTAL d5,000)
Figure 2-1. Grain Flow from Farm to Market.
-------
bushels. Typical storage capacities of country elevators constructed today
range from 300,000 to 1,000,000 bushels. Terminal elevators can have a
storage capacity of zero to about 4,000,000 bushels or more. The storage
capacity of grain elevators can be increased by adding bins on to the
original structures and storage in steel tanks or warehouse-type buildings
("flat storage"). The largest capacity under one roof is 18,000,000 bushels.
The storage capacities of processing plants range between 500,000 and 3 million
bushels.3
Country elevators receive almost 100 percent of their grain by truck.
They ship primarily by truck and rail in near equal quantities. Inland
terminals receive grain primarily by truck and rail, and ship primarily by
rail and water. Port terminals receive grain by rail, truck, or barge,
depending on their location and facilities. They ship almost exclusively by
water.
Although elevators are located throughout the United States, the major
concentration is in the grain producing States in the Mid-Plains, South Plains,
and Great Lakes regions. Terminal elevators are located in the principal
grain-marketing and shipping centers, most of which are in metropolitan areas.
Grain processing facilities for wheat, corn, and rice mills, soybean
processing plants, and wet corn mills are located in both rural and urban
areas. Although most were originally constructed in rural areas, they have
since been surrounded by metropolitan growth.
2.3 The Emission Problem
There are five primary functions that take place in an elevator as shown
in Figure 2-2; receiving, handling, cleaning, drying, and shipping. All of
2-5
-------
VENTS
ro
cr>
HEAD HOUSE
ELEVATOR LEGS
BARGE AND SHIP
LOADING
^SCALPERS
CLEANERS
SCALE AND GARNER BINS
WITH VENTS
GRAIN
DRYERV |
TRUCK
= RECEIVING
AND LOADING
HOPPERCAR RECEIVING
AND CAR LOADING /
/BXCAR
MARINE,
LEGS !
ml nil ken
RECEIVING CONVEYORS
BARGE
Figure 2-2. Terminal elevator.
-------
these are materials handling processes rather than processes which effect
a chemical or physical change in the product. Particulates are the main
pollutants, although very small amounts of combustion products can be
emitted from grain dryers (these usually operate less than 3 months per year
and burn natural or propane gas). The dust (or particulates) may contain
60-90 percent organic material. Three to twenty percent of the inorganic
portion may be free silicon (sand from entrained dirt). Specific materials
in the dust include particles of grain kernels, spores of smuts and molds,
insect debris, pollen, and dirt from the field.3
The grain dust can be emitted from almost any point in the elevator
process and most of the emissions are fugitive. They become airborne in
most cases because of ineffectual hooding or pollutant capture systems;
even effective hood designs may allow some dust to escape.
2.4 Grain Elevator Handling Facilities
The grain handling facilities at an elevator include receiving (by truck,
railcar, and barge), handling and conveying, cleaning, drying, and loading
(into trucks, rail cars, and marine vessels).
Several factors common to each of the grain handling facilities that
can affect emissions are discussed below. The first is the characteristics
of the dust which varies with the type of grain handled. A test conducted to
determine the magnitude of emissions from several grain handling facilities
also indicated that emissions from soybeans were higher than for corn, wheat,
and milo at the time of the test.3 Soybeans may contain more dirt since they
grow close to the ground and the harvester may scrape up earth as it cuts the
plant off. Corn as "beeswings," large flaky particles that readily become
2-7
-------
airborne because of their large surface area and low density. They can
be a nuisance to nearby residents during the harvest season. The moisture
content of the grain is another factor. It can vary from 11 to over 35
percent at harvest, however, not enough data are available to quantify the
effect on emissions.
The percentage of "foreign material" or "dockage" in grain (the ratio
of the weight of material other than whole grain kernels to the total weight)
can also affect emissions. Most of the foreign material may be weed seeds,
broken kernels, dirt, stones, and other heavy particles that do not cause
an emission problem. However, since chaff, straw, and other light materials
are also present with the heavy particles, a high percentage of foreign
matter is a rough indication of high emissions potential. The percent
foreign matter is often determined for each load of grain received or shipped.
2.4.1 Truck Receiving
Grain is emptied from most trucks (see Figure 2-3) by lifting the front
end with a hydraulic platform to allow grain to flow from the tailgate. The
grain falls from the truck through a heavy grate and into the receiving hopper.
Dust-laden air evolves as air in a hopper is displaced by grain. A conveyor
beneath the hopper moves the grain to storage bins.
The size of the receiving hopper limits the speed at which the grain
can be handled. Small hoppers used at country elevators and elevators at
grain processors where grain can be received at a relatively slow pace
minimize air pollution. By rapidly filling with grain, they "automatically"
decrease the free-fall distance from the truck bed. When this "choke
feed" principle occurs, it may take 5 to 10 minutes to empty a truck. At
2-8
-------
CONTROL DEVICE
ELECTRICALj
ACCOROIAN I
DOORS '
Figure 2.3. Truck unloading control system
-------
subterminal and terminal elevators where large receiving hoppers and hydraulic
platforms are used, a large 800 bushel truck is. often emptied in 3-4 minutes.
Some trucks have trailers with "hoppers" from which grain is emptied
through approximately a 24 inch by 24 inch opening in the bottom of each
hopper. Comparatively little dust evolves when hopper trucks are unloaded
since the grain flows slowly.
Most facilities, in order to protect the receiving hopper, have a
shelter with a roof and two sides that trucks can drive through. Unfortunately,
this type of building can act as a "wind tunnel" which not only increases dust
emissions but make them more difficult to contain and capture. Newer facilities
have quick closing doors at one end which close when the truck is in position
to be dumped, thus reducing or eliminating the "tunnel" effect.5.6.7'8'9'13
2.4.2 Railcar Receiving
2.4.2.1 Hopper Cars
Hopper cars are typically divided into compartments or hoppers. Each has
an opening about 2 feet square in the bottom through which the grain is dis-
charged into a receiving hopper. The receiving hopper may be small so that
only one compartment at a time can be emptied. This is common at country
elevators and elevators at grain processors where grain can be received at
a relatively slow pace. As at truck stations, small receiving hopper rapidly
fill with grain thereby decreasing the free-fall distance from the hopper car
and minimizing air emissions (see Figure 2-4). At larger facilities the
receiving hopper can permit all hoppers on the rail car to empty simultaneously.
Most facilities protect the receiving hopper from the weather by a large
2-10
-------
Ni
I
BUCKET ELEVATOR
LEG
LEG BOOT
Figure 2-4. Rail car receiving.
-------
shed with large openings at both ends. The shed can act as a wind tunnel which
makes it more difficult to contain and capture dust emissions.13
2.4.2.2 Boxcars
Conventional boxcars are sometimes used to haul grain. Before it is
loaded, a boxcar must be fitted with a "grain door" which is installed over
the lower part of the sliding door openings in the side of the car. The grain
door is made of wood or heavy cardboard and covers about three-fourths the
height of the car door opening.
The most common method of unloading boxcars is to break the grain door.
This results in a surge of dust as the grain falls into the receiving hopper
beside the tracks (see Figure 2-4). After this initial surge, the remaining
grain is scooped out of the car using power shovels, a front end loader,
or some similar means. A cloud of dust forms as each scoop of grain strikes
the receiving hopper. The other common unloading technique, used mainly by
terminal elevators, is a mechanical car dump. The car is clamped to a
movable section of track which rotates and tilts the car to dump the grain out
of the door into the receiving hopper. This technique is rapid but results
in violent agitation of the air around the flowing grain. These air currents
entrain the grain dust and sweep it from the receiving area. During this
review, it was found that the use of boxcars is rapidly declining and some
terminals will not accept them. Modern large terminals like to unload unit
trains (100 cars or more) rapidly and only hopper cars allow this rapid
unloading rate.
2-12
-------
2.4.3 Barges
Grain is received by barge at some inland terminals but mostly at port
terminal elevators. The unloading areas are generally open to the weather.
In most cases, grain is unloaded with a bucket elevator (marine leg) that is
lowered into the barge.12,7,5 Their capacities range from 15,000 to 75,000
bushels per hour; the average is about 30,000.
Dust is generated in the barge by the buckets of the leg and at the
transfer point at the top of the leg where the grain is dumped into a
receiving hopper. To completely clean the barge, it may be necessary to
push or pull the grain to the leg with power shovels or front end loaders.
These too, generate fugitive dust emissions. In the Northwest, specially
designed barges are equipped with a screw conveyor that can bring the grain
to the center of the barge and marine leg.l0^1 This allows the rest of the
barge to remain closed and requires no additional equipment (front end loaders,
etc.) to handle the grain. This process keeps emissions from barge unloading
very low.
2.4.4 Grain Handling and Conveying Equipment
Handling and conveying equipment includes bucket elevators (legs) used
to elevate the grain; conveyors (screw, drag, and belt type) which move it
horizontally; scale and surge bins used to weigh it; and distributors which
direct it to one of several places in the elevator complex.
A screw conveyor is a screw (6 inches or more in diameter) contained
within a trough. The grain which enters one end of the trough is pushed
forward as the screw turns. A drag conveyor consists of a continuous
chain with paddles attached inside a rectangular enclosure. The grain is
2-13
-------
pushed forward by the paddles. These conveyors move the grain slower (about
100-175 feet per minute) than belt conveyors. A belt conveyor is a continuous
belt (about 24-72 inches wide) that carries the grain forward at about 300-800
feet per minute. Friction between the grain and the belt occurs only when it
drops onto the moving belt, therefore, few kernels are broken.
The grain is usually conveyed to a leg which lifts it to the top of the
"headhouse" where it is discharged to a distributor system (see Figure 2-4).
The grain is usually distributed directly from the headhouse into storage
bins or silos. Some newer facilities do not use legs and use conveyors to
distribute the grain throughout the facility.
To ship grain, it is dropped from the bottom of the silo, conveyed to
a leg, and elevated to the distributor or just conveyed to the distributor
for those newer facilities without legs. From there it falls to grain
cleaners or the load-out scales. Some country and terminal elevators have
scales which are preceded and followed by surge bins. Conveyors discharge
a continuous stream of grain into the upper surge bin while the scale weighs
batch quantities and discharges them into the lower surge bin, which also
empties continuously. The grain either drops directly into the shipping
vehicle, or is conveyed to the shipping station.
Dust emissions may occur at transfer points as grain is fed onto or
discharged from a conveyor. Examples of transfer points are the discharge
from one conveyor onto another, the discharge from a leg onto a conveyor,
or the discharge from a storage silo onto a tunnel belt conveyor. If these
transfer points are open to the atmosphere, fugitive dust will be emitted
2-14
-------
directly to the interior of the elevator. This can affect the working
environment in the elevator and cause occupational health, housekeeping,
and explosion propagation problems.
Dust emissions from handling equipment can be prevented in many areas
through the use of totally enclosed equipment. Another method which minimizes
dust is to handle grains at lower velocities. This reduces agitation of the
air around the flowing grain and less dust becomes airborne.14
2.4.5 Grain Cleaning
Grain cleaners are used in many elevators because the grain must meet
USDA standards (Figure 2-5). Equipment used to clean grain varies from
scalping it to a simultaneous screening and winnowing operation. The simple
screening devices remove large sticks, rocks, tools, and other trash.
Screening operations are usually totally enclosed and emissions generated
are captured and collected in a fabric filter.
2.4.6 Grain Drying
Depending upon the grain and its basic moisture content, some grains
must be dried within a few days after receipt to prevent spoiling. Corn,
soybeans, and milo are the three major grains that require drying. A
typical country elevator might be equipped with a 1000-3000 bushel per hour
(bu/hr) dryer while a typical terminal elevator may have one or more
3500-5000 bu/hr dryers. There are two basic types of grain dryers, rack
and column (see Figures 2-6 and 2-7). Grain enters the top of both types
and flows downward in a continuous stream and out the bottom. Heated air
blown through the grain streams evaporates the excess moisture. Grain with
16-35 percent moisture can be reduced to 15-17 percent in one or more passes
through the dryers.
2-15
-------
GRAIN'
SCALPER,'
(COARSE SCREEN
DRUM)
AIR AND DUST
FOREIGN GRAINS, STONES, LARGE TRASH
GRAIN
FINES AND BROKEN KERNELS
Figure 2-6. Grain cleaning.
-------
WET PRODUCT IN
I
I
-J
WET GRAIN
EXHAUST AIR
HEATED AIR INLET
EXHAUST AIR
DRY GRAIN
CROSS-BAFFLE DRYERS
Figure 2-6. A Rack Grain dryer.
-------
DRYER
SECTION
COOLER
SECTION
COLUMN DRYER
CONVEYOR
OR
SCREW
Figure 2-7. Column Grain Dryer.
2-18
-------
Dust and chaff can become entrained in the air and carried from the
dryer. The potential quantity of dust emissions is largely dependent on
the type and model of dryer. In a column dryer the grain flows in a column
between two perforated metal sheets to the bottom. Most of the dust is
trapped within the grain and never reaches the side of the dryer. A rack
dryer contains baffles or racks around which the grain and hot air must
flow. This turning motion of the grain creates more beeswings and hulls
(a major portion of dryer emissions) than are created by column dryers.
The dryer is more open, also, since the air does not pass through metal sheets.
2.4.7 Loading
2.4.7.1 Trucks
Grain is shipped by truck from both country and inland terminal elevators.
The grain to be loaded out may be weighed in the scale hopper and then dropped
into the lower surge bin. It flows directly from the surge bin down a chute
into the truck (see Figure 2-8). Grain elevators without hopper scales will
load directly into the truck through the loading spout. Sometimes the loading
area is not enclosed and wind that blows across the end of the loading spout
entrains dust from the grain stream. Enclosing the truck loading area
on at least three sides by using quick closing doors will greatly reduce the
atmospheric emissions. Dust emissions can also be reduced by decreasing the
free-fall distance between the end of the loading spout and the truck bed.
This can be done with a telescoping loading spout or the loading spout can
be surrounded by a canvas enclosure with a duct that can withdraw dust
emissions to a control device.15
2-19
-------
GRAIN
KJ
I
KJ
O
RAILCAR LOADING TRUCK LOADING
Figure 2-8. Truck and railcar loading.
-------
2.4.7.2 RaiTears
2.4.7.2.1 Hopper Cars - Grain is shipped by hopper cars from country
and inland terminal elevators. They are loaded through either a long
rectangular hatch down the center of the car or two rows of round hatch
openings. If the grain elevator has a hopper scale, the grain to be loaded
out is weighed in the scale hopper and then drops into the lower surge bin.
It flows from the surge bin directly down a loading chute into the railcar
(see Figure 2-8). Grain elevators without a hopper scale will load directly
into the railcar through the loading spout. Dust is entrained in the air
displaced from the car. Reducing the free-fall distance between the end of
the spout and the top of the hopper car with telescoping loading spouts also
lowers emissions. Also, the pouring spout can have an annular space around
it through which the dust emissions can be withdrawn to a control device.
The amount of dust escaping the car can be reduced by keeping hatch openings
not being used closed or having flexible ducts placed in the openings which
withdraw the dust emissions to a control device.I5
2.4.7.2.2 Boxcars - Before a boxcar can be filled with grain, grain
doors must be installed over the doorway in the side of the car. The grain
door, constructed of wood or a heavy cardboard, covers about three-fourths
of the height of the door opening. The grain is directed down a loading
spout and through the opening above the grain door (see Figure 2-8). Dust
is entrained in the air displaced from the car. A hooding system covering the
door area with a duct or flexible ducts can withdraw dust emissions generated
and reduce emissions to the atmosphere.15 Industry sources indicate that
very few boxcars are used anymore and probably will be eliminated in the future.
2-21
-------
2.4.7.2.3 Barges - There are two mechanisms which result in emissions
during the loading of barges. The first is when the grain drops from the
loading spout into the barge (see Figure 2-9). Often, a free-fall distance
of several feet between the end of the spout and the top of the barge
allows wind to entrain dust from the grain stream. This free-fall distance
can be reduced and emissions minimized by using telescoping loading spouts
with an annular space at the end of the spout to capture dust emissions.
Also, a choke feeder type pouring spout can be used to reduce the effect
of the free-falling grain. The second is re-entrainment as the dust boils
up from the hold. Barges can carry approximately 50,000 bushels of grain.
The hold is usually covered with large steel hatches. To fill a barge,
portions of the top must be uncovered. Some cover designs use several
small hatches that one man can open. The smaller hatch openings minimize
the surface area of the grain that is exposed to the wind.
2.4.8 Ships
Grain loaded into ships is conveyed from the scale to the loading dock
where it drops down long spouts into the ship's hold at rates of 30,000
to 100,000 bushels per hour.
Fifty to 80-foot long loading spouts are not unusual. Emissions
increase with the length of the spout because more dust is created by
abrasion of the kernels as they bounce down the long loading spout. The
velocity of the falling grain also increases, which causes an increase in
the amount of air entrained in the grain stream. Strong winds, when present,
also increase dust emissions by entraining dust from the free-falling grain
2-22
-------
^GRAIN
ro
i
ro
GRAIN
BARGE LOADING
GRAIN
HARDHAT
BUTTERWORTH
'GRAIN
TRIMMER
BULK CARRIER
TANKER
'TWEEN DECKER
Figure 2-9. Barge and ship loading.
-------
stream below the loading spout. Increased loading rates cause more rapid
displacement of dust-laden air from the hold and also increase emissions.
Three types of ships are used to haul grain. Each presents a different source
of dust emissions (see Figure 2-9).
2.4.8.1 Bulk Carrier
The bulk carrier's hold is compartmented by a series of vertical bulkheads.
There are no internal structures to hamper the loading operation. Hatch openings
are large and permit easy access to all parts of the hold. The loading operation
for this ship can be separated into three stages: (1) the initial buildup of
a grain pile in the bottom of the hold, (2) filling to about the top 25 percent
of the hold, and (3) "topping off" or filling the top 25 percent of the hold.
Emissions are greatest during "topping off" because the wind can readily carry
the dust away. The hold cannot be covered at this time because it is necessary
to move the spout around rapidly to spread the grain. Therefore it is necessary
to minimize the distance between the spout and the grain surface in order to
reduce emissions. Newer facilities use a choke-type feeder which reduces the
emissions during all phases of the filling operation.
2.4.8.2 'Tweendecker'
The hold of the 'tweendecker1 is similar to a bulk carrier except that
instead of an unencumbered open space, the 'tweendecker' has two horizontal
intermediate decks (see Figure 2-9). The grain must be carefully stored under
the intermediate decks to assure the hold is completely filled. Otherwise,
the grain could shift which could cause the ship to list or capsize. To position
the grain under the intermediate deck a "trimmer" or high-speed conveyor belt
2-24
-------
is used to throw the grain from the loading spout. This trimmer generates
a large amount of dust so that loading a 'tweendecker' results in more
emissions than a bulk carrier. However, industry personnel report that
very few tweendeckers are used to carry grain.
2.4.8.3 Tanker
A tanker is designed for transporting liquid in bulk, but is often
used for grain (see Figure 2-9). Access to the holds is gained through
two types of hatches. The primary hatch, the "hardhat," is three feet
in diameter and is used for loading most of the grain. The "butterworth"
is one foot in diameter. It is used for filling the small spaces which
remain after filling throughout the hardhats. Less dust escapes during
filling of tanker than other ships since they can be enclosed.
2.5 Selection of Grain Elevators for NSPS Control
There are about 15,000 grain elevators of various storage and handling
capacities throughout the United States with the majority located in the
grain belt areas. As specified in the Clean Air Act, the grain elevator
NSPS applies only to those grain elevators with a permanent storage capacity
of 2.5 million bushels or greater and grain storage elevators (mills) with
permanent storage capacity of 1.0 million bushels or greater. Grain
elevators were selected for NSPS development because they can be significant
sources of particulate matter (PM). At the time of NSPS development, the
nationwide emissions of PM from grain elevators were estimated to be 606,000
tons per year in 1971.3 Using the model plant from Chapter 6, total
uncontrolled PM emissions from this plant would be about 5400 tons per
2-25
-------
year. Emissions from this plant without NSPS controls would be about 2600
tons per year. If the plant were to meet NSPS regulations, emissions
would be reduced to about 100 tons per year of PM. Growth in the grain
industry is expected to continue, but because of uncertainties of the
world markets, surpluses, and governmental policies, the accuracy of any
firm growth rates are suspect.
2-26
-------
REFERENCES:
1. Agricultural Statistics, 1981. U. S. Department of Agriculture,
Washington, D. C.
2. Federal Register. Thursday, August 3, 1978, Part III, Environmental
Protection Agency, "New, Modified, and Reconstructed Grain Elevators,
Standards of Performance for New Stationary Sources.
3. Standards Support and Environmental Impact Statement, Volume I:
Proposed Standards of Performance for Grain Elevator Industry:
EPA-450/2-77-001a, January 1977.
4. Telecon: Iversen, R., EPA, with R. Nolan, R. S. Fling and Partners,
Minneapolis, Minnesota. Discussion on growth rates and capital costs
of affected shipping facilities. November 17, 1982.
5. Trip Report: Cargill, Inc., Channelview, Texas, August 16, 1982.
6. Trip Report: Cargill, Inc., Chesapeake, Virginia, August 25, 1982.
7. Trip Report: The Anderson's, Toledo, Ohio, September 7, 1982.
8. Trip Report: Cargill, Inc., Portage, Indiana, Septembers, 1982.
9. Trip Report: Cargill, Inc., Toledo, Ohio, September 7, 1982.
10. Trip Report: Bunge, Inc., Portland, Oregon, June 24, 1982.
11. Trip Report: United Grain Corporation, Vancouver, Washington,
June 23, 1982.
12. Trip Report: Bunge, Inc., Destrehan, Louisiana, August 19, 1982.
13. "Dust Control for Truck and Rail Receiving," W. Gary Winsett,
T. E. Stivers, Organization; Grain Dust Control Seminar by National
Grain and Feed Association, St. Louis, Missouri, May 7-8, 1981.
14. "Dust Containment for Grain Handling Operations," Donald R. Biorn,
Cargill, Inc., Minneapolis, Minnesota, Grain Dust Control Seminar by
National Grain and Feed Association, St. Louis, Missouri, May 7-8, 1981,
15. "Minimizing Dust Emissions During Truck and Rail Load-Out," Gary L.
McDaniel, MAC Equipment Inc., Grain Dust Control Seminar by National
Grain and Feed Association, St. Louis, Missouri, May 7-8, 1981.
2-27
-------
3. CURRENT NSPS FOR THE GRAIN ELEVATOR INDUSTRY
3.1 Federal New Source Performance Standard
New source performance standards (NSPS) for the grain elevator
industry were promulgated on August 3, 1978, limiting particulate matter
and visible emissions from new, modified, and reconstructed grain elevator
terminals (2.5 x 106 bushels storage capacity or larger) and grain
storage elevators at flour mills (1.0 x 106 bushels storage capacity
or larger).!
The standards limit particulate matter and visible emissions
from the affected facilities at grain elevators as follows:
Affected Facility
Fugitive Emissions
Truck loading
Truck unloading
Boxcar and hopper
car loading
Boxcar and hopper
car unloading
Barge or ship loading
Barge or ship unloading
Grain dryer
Emission Limit
10% opacity
5% opacity
5% opacity
5% opacity
2Q% for all loading operations
Equipment standard: Marine
leg enclosed from top to bottom
of leg, with ventilation flow
rate of both leg and receiving
hopper of 40 ft^ of air per
bushel of grain unloaded.
0% opacity or equipment standard:
(1) column dryer-use of perforated
plates with hole sizes no larger
than 0.094 inch diameter. (2) Rack
dryer-use of 50 mesh or finer screen.
3-1
-------
Affected Facility
Grain handling
Emission control device on
air ventilated from affected
facilities
Emission Limit
0% opacity
0% opacity and 0.01 grain per
dry standard cubic foot
Particulate emissions must be tested by Method 5 and visible
emissions by Method 9. All process parameters must be monitored
during the test period and the type of grain being handled must
be identified. Where an equipment standard is required, the
equipment must be inspected or certified information provided by
the owner/operator that the equipment meets NSPS requirements.
No continuous monitoring requirements to meet NSPS are required for
the grain elevator industry.
3.2 State Emission Limitations for Grain Elevators
In general, only a few States have regulations that specifically
pertain to existing grain elevator facilities. Those States that do not
mention grain elevators as a specific industry usually have a process
weight regulation that would include grain elevator processes (see
Table 3-1).
For those States that specifically mention grain processes, the
regulations usually vary depending upon the storage capacity of the
facility. Facilities of 300,000 bushels of storage and under have regu-
lations that require good engineering design and operating techniques
and to not be a nuisance in their area. Facilities above 300,000 and
below 2,000,000 bushels of storage are required to use good engineering
design and operating practices, and if in a rural area, control device
efficiencies are required to be 90 percent or better. If the facility
3-2
-------
is in an urban area, the control device efficiency is increased to 98
percent or better. Existing facilities over 2,000,000 bushels of storage
and new facilities usually have to meet the requirements of 98 percent
efficient control devices, equipment design criteria, and specific
ventilation rates similar to NSPS requirements. Finally, some States
have a specific emission limitation on the control device. All States
limit visible emissions to less than 20 percent opacity for new facilities
and 40 percent opacity for existing facilities. Most States have accepted
delegation of enforcing the NSPS for the grain elevator industry. Those
States that have not accepted delegation of NSPS cite that they do not
have the money or personnel at this time to handle NSPS regulation, or
that State legislation has not provided a regulation to meet NSPS.
3-3
-------
TABLE 3-1. TYPICAL STATE PROCESS WEIGHT REGULATIONS FOR GRAIN ELEVATORS
Particulate Regulation Opacity Regulation
1. E = (4.1)(pO-67) <_ 60,000 Ib/hr <_ 20%
E = (55)(pO-l1) minus 40 > 60,000 Ib/hr
(a)
2. E = (3.12)(p0.985) _< 40,000 Ib/hr
E = (25.4)(pO.287) > 40,000 Ib/hr
E = rate of emissions in Ib/hr.
P = Process weight in ton/hr.
(a) Texas regulation
3-4
-------
REFERENCES
1. Federal Register. August 3, 1978, Part III, EPA, Standards of
Performance for New, Modified, and Reconstructed Grain Elevators.
2. Environmental Reporter: State Air Laws. Volumes 1, 2, and 3.
3-5
-------
4. STATUS OF CONTROL TECHNOLOGY
The review of the NSPS did not reveal any new control technology or
techniques since NSPS promulgation, except for some experimental work
with oil, water, and steam sprays discussed later in this chapter.
However, many plants have made considerable improvements in controlling
emissions by adding new control devices or replacing older, less efficient
control devices, not only for environmental purposes but also to reduce
explosion potential, improve working conditions, and other safety
conditions. ^5
4.1 Particulate Control
Data from a questionnaire survey and plant visits of new or recently
modified elevators that were required to meet the NSPS show the exclusive
use of fabric filters as the control device.1 Fabric filters find
extensive use by non-NSPS elevators that are located in more heavily
populated urban areas where State and local ageancies require more
stringent control techniques, and are starting to find increased use in
smaller elevators and country elevators as required by local and State
control agencies or for safety reasons.
The typical modern fabric filter (see Figure 4.1) at an elevator
handles 2000 to 50,000 cubic feet of air per minute depending upon
the grain handling facility applied. Most are package units that can
be supplied by several manufacturers. The filters operate under negative
pressure with the fan pulling air through the system. Felted, synthetic
4-1
-------
Valve Body Assembly:
-Plenum Chamber
Butterfly Valve
Reverse Air
Pressure Blower
Magnehelic
Gauge
" .*» "%
~ 'J w t » . -
;'. > Lower Chamber
Wire Sleeves
with Filter
Stockings
Sin Level Indicator
Rotary
j) Air Lock
Discharge
uL
Figure 4-1. Typical Fabric Filter Used by Grain Elevators
4-2
-------
fabrics are the most common collection media. The air-to-cloth ratios can
range from 3:1 to 15:1, but are usually between 8:1 and 11:1. The filter
bags are cleaned by reversing the air flow through them. Air flow reversal
methods include forcing the dust cake off the fabric with back pressure;
collapsing the cloth thereby cracking the dust cake; snapping the cake off
with a pulse of compressed air; and blowing it off with a reverse jet which
traverses the outside surface of the cloth. The fabric filters typically
have efficiencies in excess of 99 percent, and a well operated and maintained
unit will not have visible emissions.
Some non-NSPS elevators may still use cyclones, especially those
elevators that are small, older, or located in rural areas. Cyclones are
classified as either high-efficiency or high-throughput. High-efficiency
cyclones are characterized by a narrow inlet opening, long body length
relative to body diameter, and a small outlet diameter. The higher gas
velocity in the cyclone results in a collection efficiency of about 85 to
95 percent. The pressure drop across a high efficiency cyclone may be
3 to 5 inches of water.
High-throughput cyclones have large inlet openings, large diameter
bodies and large outlet diameters. The slower gas velocity results in
collection efficiencies between 60 to 85 percent and pressure drops of
only 0.5 to 2.0 inches of water. The major problems with cyclones are
their low particulate matter collection efficiencies compared to fabric
filters and their visible emissions.
4-3
-------
The method of capturing particulate emissions for each grain elevator
process in the industry is considered individually to show the most
important differences. The techniques used for each process are discussed
below.
4.1.1 Receiving (Unloading)
4.1.1.1 Trucks
Modern truck receiving hoppers are usually enclosed except for the
ends (doorways). (Figure 4-2) The typical capture system consists of a
collection of hood(s) spaced (Figure 4-3) around the receiving hopper.
Also, hoods may be mounted either above or below the grate. Location below
the grate is preferable because the resulting downward draft helps prevent
escape of dust generated in the hopper. Specially designed baffles in-
stalled under the grate help retard the upward flow of dust-laden air
out of the hopper (Figure 4-4).10 This design is typical for some new
truck and rail unloading systems. Such systems are typically designed for
a face velocity of 200 feet per minute or more through the grate.20 In the
best controlled systems, the receiving hopper is enclosed on three sides
with a door installed at the entrance that will automatically close when
the safety stop for the truck is in place or is operator controlled.
However, some truck unloading stations cannot close the door when unloading
a hopper truck because the unloading station is not long enough. Although
hopper type trucks do not generate as much dust as the end unloading
trucks, some emissions could be carried outside the structure depending
upon the velocity of the wind. The best truck unloading stations are
those that are designed to be able to close the door for any type of
4-4
-------
CONTROL DEVICEH
ELECTRICALi
ACCORDIAN |
DOORS
Figure 4-2. Truck unloading control system..
-------
n
SWINGING DUSTI
CONTROL BAFFLES i
^^V.^V--::-,.*' ry-Trfv
TRUCK WHEEL BLOCK
-GRATING/ V _T>USfl_
SUPPORT BEAMS! ^ EXHAUST i
J3UCTSI
MAlN-EXHAUSTDUCTf
T_O FABRIC FtLTERJ
PLAN VIEW,'
GRATING
-STTr-^N OUTSIDE AIR" / SUPPORT i
' ~f" ) /(BEAMS i..^;^::
EXHAUST
r DUCTS f
\ ^-;: GRAIN;'
^J^yY-^TTT/.^^
MAIN
D'JCT
TXil \ ^-1X! V; ^^
-DUST FLOW/ -
SIDE VIEW
Figure 4-3. Truck grain dump facility,
4-6
-------
'GRATING /
.OUTStPE AIR,
~\
\
GRATING;
SUPPORT BEAM!
OUTSIDE AIR
GRAIN'
SWINGING DUST!
CONTROL BAFFLE
* (Swinging baffle
size slightly
exaggerated to
show detail.)
Figure 4-4. Beam and baffle detail
4-7
-------
truck.20 The door should be closed before each truck is dumped. These
two techniques prevent wind from interfering with the effectiveness of
capture by the hood. There are little or no visible emissions of fugitive
dust when the receiving area is enclosed on at least three sides during
the unloading operation and the best capture system is used.2.10 After
capture, the dust is aspirated to a fabric filter.
4.1.2 Rail cars
4.1.2.1 Hopper Cars
Hopper cars are sometimes unloaded using the choke feed concept to
reduce or eliminate emissions. In this case the receiving hopper is usually
shallow and the discharging grain forms a cone between the opening at
the bottom of the hopper and the receiving grate (see Figure 4-5).20
There may be a momentary cloud of dust as the receiving hopper fills, but
very little during the remainder of the unloading operation as the grain
slowly flows into the hopper. Walls around three sides of the receiving
area or a skirt around the hopper will help prevent wind from blowing dust
from the cone of grain. However, most large elevators use or unload unit
trains and the closing of a door after each car (disconnecting and connecting
process) could cause the train to be held an excessive length of time and
result in penalties (demurrage) to the elevator.
Most new modern rail unloading stations seen during this review are
quite large, and the emissions generated during unloading rarely reach the
open doorways. Emissions from a deep receiving hopper are contained by
aspirating dust from below the grate to a fabric filter. The efficiency of
dust pickup can be increased by installing special baffles under the grate to
4-8
-------
\ \UNLOADING*A \ \ \
J\.\\
. \ \ »
\\ \ \
ELECTRICAL
ACCORDIAN
DOORS
HOPPER CAR
UNLOADING
RECEIVING HOPPER
Figure 4-5. Railcar unloading control systems.
-------
help retard the upward flow of dust-laden air out of the hopper as discussed
in truck unloading. Such systems are typically designed for a face velocity
of 200 feet per minute or more through the grate. The receiving area can
also be enclosed on three sides, where unit trains are not used, to help
prevent wind currents from decreasing the effectiveness of the dust capture
system. Most modern elevators today use deep receiving hopper. There were
few visible emissions of fugitive dust seen coming from the modern unloading
or loading buildings and control systems visited during this review.2.5'8
4.1.2.2 Boxcars
Very few grain elevators handle boxcars anymore and grain elevator
operators have indicated that the days of the boxcar are numbered. Several
elevators visited during the review had closed their boxcar unloading
facility. However, those in use are similar in design to those for hopper
cars.
Two unloading methods are used for boxcars.20 One method is breaking a
grain door (heavy paper) inside the regular car door opening. This produces
a surge of grain and dust as the grain falls into the hopper. The remaining
grain is scooped out by hand or tractor and each scoop produces a surge of
dust. Since most of the dust is generated in the receiving hopper, it is
usually captured by special hoods located below the grate and aspirated to a
fabric filter (see Figure 4-5). Baffles installed under the grate help
prevent the upward flow of dust-laden air out of the hopper. The efficiency
of dust pickup is improved by stopping wind action with a flexible enclosure
around the car door (Figure 4-6).
4-10
-------
UNLOADING
DEVICE
ENCLOSURE-
HOPPER
Figure 4-6. Boxcar unloading control system.
4-11
-------
Another common boxcar unloading method is a mechanical boxcar dump which
picks up and tilts the boxcar to dump the grain. This rapid unloading creates
a large surge of dust which is difficult to contain unless the unloading
facility is completely enclosed. Capture systems for these facilities are
typically designed for a face velocity of 200 feet per minute or more through
the grate.20 There are reportedly little or no visible emissions of fugitive
dust when the best capture system is used.14 No boxcar facilities were in
operation during plant visits in this review.
4.1.3 Barges
To minimize emissions from unloading grain from barges, the bucket
elevators (marine legs), receiving hoppers, and conveyor belts are enclosed.
Dust is aspirated from the enclosures to a cyclone or fabric filter (Figure 4-7)
Good maintenance of the enclosures is essential for good capture. The NSPS
requires that the marine leg be enclosed from top to bottom (except where it
is necessary to have the bottom pulley portion open - Figure 4-7) and have
a ventilation flow rate of 40 ft3 of air per bushel of grain unloaded. Also,
newer marine legs use large plastic buckets to handle the grain and the leg
can operate at a slower speed, thus not generating as much dust when picking
p O Q Q pQ
up the grain, but still delivering the same or more bushels per hour.^J>°>^
4.1.4 Handling and Conveying Equipment
4.1.4.1 Transfer Points
Screw conveyors are enclosed and are operated slowly (usually about
100-175 feet per minute) so that no dust is emitted. Drag conveyors are
also totally enclosed and normally not aspirated. Hoods are needed on
4-12
-------
-p-
I
)»
U)
FABRIC
FILTER
MARINE
LEG(S)
_r'
U
x-1
Figure 4-7. Typical barge receiving control system.
^
(*£*>. rVt^*^^-*"'??* *i??t^*=y*r!F5?r:
f/.'c:- ;. ::-r? -_ :. ;. -' : '..' ' -: '.7-.,
BARGE
JL_
-------
belt conveyors only at points where the grain is to be transferred
(i.e., where it enters or leaves the belt) or when they are located out
of doors. Otherwise, a column of air travels with the conveyor and does
not disturb the grain dust. Sometimes, if transfer points are close
together, the belt is hooded along its entire length. Modern elevators,
recently visited, usually hood the entire conveyor system. The capture
velocity of air into the hood should be 100 feet per minute faster than the
speed of the conveyor belt (500-800 feet per minute) to overcome the laminar
layer of air that accompanies the grain away from the hood. Air and dust
are aspirated from the hoods to fabric filters (Figure 4-8).
4.1.4.2 Legs
When grain enters the bottom of a "leg" or bucket elevator, a positive
pressure is created at the top. It is necessary to relieve this pressure
by venting the leg to an emission control device. Dust can build up in
legs creating explosive conditions; therefore, some insurance companies
require that they be vented to minimize this possibility.
New elevator legs may have large plastic buckets and the leg is
designed to allow it to operate at a slower speed, thus not generating as
much dust. The larger buckets (Figure 4-9) allow a greater handling
capacity and the plastic construction reduces the chances of sparks being
caused in the leg and attendant explosions. There are no visible emissions
of fugitive dust when the best enclosures and/or aspiration systems are
used (Figure 4-9), and none were seen from the legs during plants visits for
the NSPS review.2'4'6'8'9'10'12
4-U
-------
CONVEYOR BELT
Figure 4-8. Transfer point control system.
-------
ELEVATOR LEG
I
cr>
Figure 4-9. Elevator leg.
-------
Some new elevators have eliminated legs feeding the storage silos
and use only conveyor systems. The major reason for this is that the legs
are considered the largest generator of dust within a grain facility,
therefore, have the greatest potential for explosions. Conveyor belt
systems reduce this hazard considerably.
4.1.4.3 Scales and Garners
A scale hopper or bin and the associated surge bins (garners) may be
vented to a common collector (Figure 4-10). Fabric filters are the major
control device. There are no visible emissions of fugitive dust from the
bins when the best capture and control system is used.2»4>6>8>9>10»12
4.1.4.4 Storage Silos
In the past, emissions from silos were not visible; therefore, they
were not controlled because the tops of the silos were usually interconnected,
which eliminates atmospheric emissions. Howerver, as a fire and safety
precaution, modern plants and many recently modified plants do not inter-
connect silos. In some modern elevators, storage silos are aspirated to a
fabric filter (Figure 4-10).
4.1.4.5 Cleaning
Emissions from screen cleaners are controlled by hooding or partially
enclosing the cleaner and aspirating the dust to a cyclone or fabric filter
(see Figure 4-10). The more thorough aspiration-type cleaners use tight
enclosures around the screens and more suction to lift out light impurities.
Some modern elevators use screen cleaners which have air-tight enclosures and
required no aspiration or emissions control device. There are no visible
emissions of fugitive dust when enclosed equipment or the best capture and
control system is used.14
4-17
-------
I
1
co
CLEANER
FILTER
HEADHOUSE
FILTER
// I GALLERY
/ I SYSTEM
V
TUNNEL BELT SYSTEM
Figure 4-10. Grain handling and cleaning dust control system.
-------
4.1.4.6 Drying
There are two types of dryers used in the industry, column and rack or
cross baffle (Figures 4-11 and 4-12).12.22 Both dryers use heated air which
dries the grain as it moves down the heating zones of the dryers.
In a column dryer the grain passes down between perforated plates and
the heated air is forced through the grain from inside to the outside.
It has been shown that column dryers with column perforation plate hole
diameters of 0.094 inch or less will achieve zero percent opacity.14 There
were no visible emissions seen from column dryers in operation at one plant
during this review.^
Another dryer being used in the industry uses a wire screen with
rectangular openings of 0.0486 inch by 0.5 inch. This screen size opening
has been found in compliance with the NSPS.1^
In a cross baffle or rack dryer, the drying air with particulate matter
is cooled and goes to a rotary drum system covered with a 50 mesh polyester
screen. The screen separates the particulate matter out of the gas stream
and the gases passing through the screen can go to a control device for
further cleaning, or in newer and more energy efficient units, allow some
of the gases to be recirculated back to the heating cycle. Vacuum heads
continually clean the screen and the particulate matter is returned to the
product cycle or sent to the dust bin. No rack dryers were seen in operation
during this review. There are reportedly no visible emissions using the best
system of capture and control.14
4-19
-------
m
x
X
>
c
to
o
3
O
W
en
i
o
>
Trt
n
m
O
m
3)
en
m
H
O
0>
I
QJ
O
O>
3
O
n>
DISCHARGE
SECTION
COOLINO ZONE
DRYING ZONE
GARNER
SECTIONS
FAN CHAMBER ROTARY CENTRILECTOR
CHAMBER
-------
DRYER
SECTION
COOLER
SECTION
COLUMN DRYER
CONVEYOR
OR
SCREW
Figure 4-12. Column Grain Dryer
4-21
-------
4.1.5 Loading
4.1.5.1 Trucks
Very few truck loading stations have aspiration type control systems,
mainly because loading trucks at most terminal elevators is a very small
part of their loading of grains. Emissions from truck loading can be
minimized by reducing the free-fall distance between the end of the
loading spout and the truck bed. This can be accomplished with a tele-
scoping spout (Figure 4-13). The height of a telescoping spout can be
adjusted quickly to any level to maintain it at the surface of the grain.
Another more modern system is to use the telescoping system with a choke
or controlled feed (Figure 4-14). The controlled feeder slows the velocity
of the grain as it comes down the spout and reduces the formation of
dust. Also, the dust can be aspirated to a control device in the annular
air space around the pouring spout. A permanent hood would not be efficient
because of the variety in size and height of the trucks. Capture can be
improved if the loading area is enclosed on three sides. There are
little or no visible emissions of fugitive dust when the loading area is
enclosed and a telescoping loading spout or choke feeder is used.14'23
Truck loading is rare at large grain elevators and is usually confined
to small elevators.
4.1.6 Rail cars
4.1.6.1 Hopper Cars
Emissions from hopper car loading can be similarly minimized by use of
a telescoping loading spout or choke feeder as discussed for trucks
(Figure 4-15).14>23 All hatch doors on the car should be kept closed except
for the one grain is entering. This allows the car to act as its own settling
chamber.
4-22
-------
ELECTRICAL
ACCORDIAN
DOORS
Figure 4-13. Truck loading control system.
4-23
-------
Air Suction
Air Conduit
Must be Flex
Hose or Swivel
Joint
Telescoping
Grain Spout
Outer Sleeve
Must Be Telescoping
or Collapsible
Must Maintain
12" Clearance
to Be Most
Effective
Dead Box
Figure 4-14. Retractable spout deadbox for truck load-out.
4-24
-------
Grain Spout
.p-
N3
Figure 4-15. Combination deadbox with suction hood.
-------
Another technique used is to install a hood at the discharge of the
loading spout or on one of the hatch doors not being used and aspirate
the dust to a control device. The hatch doors must be kept closed and
control will be further improved if the loading area is enclosed. There are
little or no visible emissions of fugitive dust when good capture systems
are used.
4.1.6.2 Boxcars
Presently, there are very few boxcar loading stations and most do not
use any type of control device. However, these emissions can be captured
by a hood located beside the track (Figure 4-16). A flexible accordian-
type enclosure should be extendible from the hood to the door of the car.
The dust can then be aspirated to a control device. There are little or
no visible emissions of fugitive dust when the best capture system is used.14.23
4.1.7 Barges
Emissions from barge loading can be minimized by reducing the free-fall
distance from the end of the spout to the grain surface as discussed previously.
Also, a choke-type feeder could be used as discussed in the truck loading
section, and openings not being used should be closed. In addition, aspiration
from the discharge end of the spout can be applied (Figure 4-17). Visible
emissions of fugitive dust seldom exceed 10 percent opacity when the spout is
kept at the surface of the grain or choke-feeder used, and dust is aspirated
from the end.14.24 The dust aspirated from the end of the spout is usually
collected in a fabric filter.
4-26
-------
LOADING SPOUT
EXHAUST DUCT
EXHAUST DUCT
APPROX. 12" CLEARANCE
BETWEEN BOXCAR AND HOUSING
Figure 4-16. Dust control system for boxcar loading.
4-27
-------
DUST
COLLECTOR
:.».;.*
HOSE ADAPTER
r FOR TANKER
Figure 4-17. Barge or shipleading dust control system.
4-28
-------
4.1.8 Ships
The major approaches used to control emissions from ship loading are
discussed below:
The entire hold is covered with canvas or plastic except where the
loading spout enters. Dust may be aspirated from beneath the cover to a
cyclone or fabric filter, but in some cases the cover is used to make the
hold a large settling chamber.4'9
In another approach, a telescoping loading spout is kept extended to
the grain surface. Aspiration can be applied to the end of the spout and
the dust collected in a fabric filter as shown in Figure 4-17. However,
some facilities do not have an aspiration system and depend upon the pouring
spout being kept just a few inches above the grain pile, thus reducing the
free-fall and keeping emissions to a minimum. Any emissions escaping this
system are not captured. Visible emissions of fugitive dust seldom exceed
20 percent opacity when either system is used and the dust is aspirated to
the dust collection system.2
Finally, a choke or controlled type feeder (as discussed and shown in
the truck loading section is used at most new modern loading terminals.^4'24
Visible emissions of fugitive dust seldom exceeded 10 percent opacity when
this system was operating properly,14 and during plant visits for the NSPS
review. All modern or modified elevators visited during this review used
only fabric filters as the control device on ship loading operations.
4.1.9 Potential New Control Technology
Some companies are experimenting and using additives such as oil, water,
and steam as methods for reducing dust emissions. One company is using
4-29
-------
water sprays on their ship loading facility. Water is applied at the rate
of 0.2 percent using carefully calibrated pumps and nozzles in each pouring
spout. The ship loading facility uses a standard telescoping pouring spout
which depends upon keeping the free-fall distance between the spout discharge
and grain pile to a minimum to help reduce dust generation. EPA in this
review did not see the water system in operation, but local and State agency
personnel report good results with the system.15
A couple of companies have been experimenting with and using a mineral
oil which is sprayed on the grain as it is carried by a conveyor belt. The
oil is applied by carefully controlled metering pumps and spray nozzles
at the rate of about 200 ppm. EPA observed a demonstration of the oil
system at a large inland grain terminal.16 The results between the tests
with grain and no controls versus using the oil spray were dramatic with
nearly zero opacity for the oil test compared to 40-50 percent opacity for
the uncontrolled test. Oil spraying is reportedly being used by another
company at various points in their in-house processing of grains which are
used internally.5 Oil treatment has been approved for use on grains for
animal usage, but has not been approved for shipment of grains overseas
or grains for human consumption.
Oil treatment appears to have several advantages in that it appears
that the grain may be re-handled without generating excess dust emissions.
One company estimates conservatively that almost 40 percent of their energy
bill could be reduced due to not operating emission control systems.4 Also,
maintenance and other operating costs would be reduced or eliminated.
Furthermore, one of the most important aspects of this system would be the
4-30
-------
potential for eliminating explosive situations, other safety and housekeeping
problems (OSHA regulations), and the possible elimination of dust handling
systems. However, some potential problems in the case of oil treatment to
be resolved are possible rancidity of the grain with time, oil build-up on
the process equipment with time, and the additional cost of treatment per
bushel of grain compared to conventional dust control systems. Another
potential dust suppression system being studied by one company is the use
of steam.18 The company has done some development work and has it in
operation on a rail loading facility. They claim good results, but EPA did
not see the process in operation during this review.
All the systems have the potential to suppress dust emissions and deter
potential explosive problems, OSHA problems, reduce operating, maintenance,
and energy costs, and recover the dust that is now discarded or sold at a loss,
4-31
-------
REFERENCES:
1. Trip Report: North Pacific Grain Growers, Inc., Kalama, Washington,
June 21, 1982.
2. Trip Report: Cargill, Inc., Portland, Oregon, June 22, 1982.
3. Trip Report: United Grain Corporation, Vancouver, Washington,
June 23, 1982.
4. Trip Report: Louis-Dreyfus Corporation, Portland, Oregon, June 24, 1982
5. Trip Report: FAR-MAR-CO, Inc., Galveston, Texas, August 16, 1982.
6. Trip Report: Cargill, Inc., Channelview, Texas, August 16, 1982.
7. Trip Report: Continental Grain Company, Westwego, Louisiana,
August 19, 1982.
8. Trip Report: Bunge Corporation, Portland, Oregon, June 24, 1982.
9. Trip Report: Bunge Corporation, Destrehan, Louisiana, August 19, 1982.
10. Trip Report: Cargill, Inc., Chesapeake, Virginia, August 25, 1982.
11. Trip Report: The Anderson's, Toledo, Ohio, September 7, 1982.
12. Trip Report: Cargill, Inc., Toledo, Ohio, September 7, 1982.
13. Trip Report: Cargill, inc., Burns Harbor, Indiana, September 8, 1982.
14. Standards Support and Environmental Impact Statement, Volume 1,^
"Proposed Standards of Performance for Grain Elevator Industry.1
EPA-450/2-77-001a, January 1977.
15. Trip Report: The Anderson's, Toledo, Ohio, September 7, 1982.
16. Trip Report: Bunge Corporation, July 21, 1982.
17. Telephone conversation, Con-Ag Corporation, September 1, 1982.
18. Trip Report: Peavy Grain, Paulina, Louisiana, August 18, 1982.
19. Grain Dryer Compliance Test, South Dakota Department of Water and
Natural Resources, January 6, 1983.
20. "Dust Control for Truck and Rail Receiving," W. Gary Winsett,
T. E. Steigs Organization, Grain Dust Control Seminar by National
Grain and Feed Association, St. Louis, Missouri, May 7-8, 1981.
4-32
-------
21. Trip Report: Columbia Grain, Inc., Portland, Oregon, June 22, 1982.
22. "Dust Control for Grain Dryers," James M. Appal el, The Anderson's,
Grain Dust Control Seminar by National Grain and Feed Association,
St. Louis, Missouri, May 7-8, 1981.
23. "Minimizing Dust Emissions During Truck and Rail Load Out," Gary L.
McDaniel, MAC Equipment Inc., Grain Dust Control Seminar by National
Grain and Feed Association, St. Louis, Missouri, May 7-8, 1981.
24. "Controlling Dust for Barge and Ship Loading," Richard J. Nolan,
R. S. Fling & Partners, Inc., Grain Dust Control Seminar by National
Grain and Feed Association, St. Louis, Missouri, May 7-8, 1981.
25. Prevention of Grain Elevator and Mill Explosions, National Materials
Advisory Board, Publication NMAB 367-2, National Academy Press,
Washington, D.C. 1982.
4-33
-------
5. COMPLIANCE TEST RESULTS
Since August 3, 1978, when the NSPS were promulgated, six grain
elevators have been newly constructed or had major modifications which
made them subject to NSPS. Two of these plants had compliance tests
conducted for particulate matter on some of the control devices. Visible
emissions tests were conducted at one of the six plants. Two of the
plants-3.4 are still undergoing modifications and compliance reports from
two State control agencies have been received on two other plants.5,6
5.1 Particulate Emission Test Data
During this review, available emission test data were obtained
for two grain elevator terminals from the State of Texas.^^ These data
are summarized in Table 5-1. These data show that the fabric filter control
devices easily met the NSPS requirements for particulate matter emissions.
At one grain elevator, there were 36 different fabric filters, therefore,
the State, with EPA approval, chose four fabric filters to be tested
and these would be considered typical for all fabric filters to determine
if the facility was in compliance. At the other grain elevator terminal,
a new scale tower system that had to meet NSPS was source tested . Again,
the results show the fabric filter control device easily met NSPS require-
ments for particulate emissions. Process information was taken during
the compliance tests and shows that normal operating conditions were
being observed during the tests.
5.2 Visible Emissions
Visible emission readings were taken for the compliance tests
at plant B. The results show that the opacity readings from the control
5-1
-------
devices were zero, thus, meeting NSPS requirements. Plant visits to
several grain elevator terminals during this review did not reveal any
apparent violations of the grain elevator visible emission NSPS (unofficial
readings) requirements for all the processes required to meet the NSPS.
5.3 Other Atmospheric Emissions
There is not any known data of other atmospheric emissions from
grain elevator terminals. Some elevators have dryers which are usually
fired by gas. However, no data have been found on the amount of
emissions from grain dryers on this source.
5.4 Water and Solid Waste Emissions
There are no known grain elevators that use wet scrubbers, however,
one company reports using a grain washer. The water from this washer
is captured and sprayed on vacant land on the property of the grain
elevator.
At some grain elevators, the dust from the control devices (except
ship loading) is captured and sent to a storage silo where the dust is
sent to a landfill or sold. Most elevators return all dust to the process
stream. The major reason for collecting and removing the dust, other
than environmental considerations, is to reduce the potential for dust
explosions.
5-2
-------
TABLE 5-1. COMPLIANCE TEST DATA
Plant
A
B
B
B
B
Source
Scale
tower
Scale
tower
Rail
unloading
Transfer
house
Silos
System
FF
FF
FF
FF
FF
Emissions (a)
gr/dscf g/dscm
0.0004
0.0051
0.0062
0.0054
0.0033
0.0009
0.0117
0.0142
0.0126
0.0076
Percent
lOpacity(b)
0
NT
NT
NT
NT
Reference
1
2
2
2
2
(a) EPA Method 5 for particulate matter: average of 3 tests,
NSPS = 0.0230 g/dscm (0.01 gr/dscf)
(b) EPA Method 9 for visible emissions.
CODE - FF = fabric filter
NT = not taken
5-3
-------
REFERENCES
1. Emission test report, Cargill, Inc., Channel view, Texas. Texas Air
Control Board, November 17-20, 1981.
2. Emission test report, FAR-MAR-CO, Inc., Galveston, Texas. Texas Air
Control Board. April 10-13, 1981.
3. Trip report, United Grain Corporation, Vancouver, Washington,
June 23, 1982.
4. Trip report, Continental Grain Company, Westwego, Louisiana,
August 19, 1982.
5. Inspectors report for Cargill, Inc., Chesapeake, Virginia,
Norfolk, Virginia, Air Pollution Control District.
6. Inspectors report for Cargill, Inc., Burns Harbor, Indiana,
Indiana State Board of Health.
5-4
-------
6. COST ANALYSIS
The purpose of this chapter is to present updated capital and
annualized costs for the control systems used to achieve the NSPS. The
model plant size, air flows, and control devices are shown in Table 6-1.
The costs are presented for each of the affected facilities for the
various capacities shown on Table 6-2. The cost-effectiveness of the
control systems is also presented. All costs are in terms of August 1982
dollars. Actual industry costs are used where available.
The capital cost of a control system includes all the cost items
necessary to design, purchase, and install the particular device or
system. The capital cost includes the purchased costs of the major
control device and auxiliaries such as pumps, fan, and instrumentation,
the equipment installation cost including foundations, piping, electrical
wiring, and erection; and the cost of engineering construction overhead,
and contingencies.
The annualized cost of a control system is a measure of what it
costs the company to own and operate the system. The annualized costs
include direct operating costs such as labor, utilities, and maintenance;
and capital related charges such as depreciation, interest, administrative
overhead, property taxes, and insurance.
6.1 Updated Costs for the Affected Facilities
The NSPS for grain elevators cover particulate emissions and equipment
standards for the dryers and marine legs. The updated costs, including
capital costs, annualized costs, and the cost-effectiveness for each system
6-1
-------
TABLE 6-1. PORT TERMINAL MODEL PLANT CONTROL DEVICES, AIR FLOWS, AND COSTS
Type
Facility
Port terminal
80,000,000 bu/yr
throughput.
5,000,000 bu
storage capacity
CTl
I
ro
Process
Truck
Rail
Barge
Grain
Drying
Land
Ship
Percent
Throughput
20
45
35
100
100
1
98
Control
Device
FF
FF
FF
FF
Vacuum
screen
FF
FF
Air Flow
(cfm)
20,000
30,000
40,000
240,000*
900,000**
30,000***
60,000
Capital
Costs
$/cfm
8.40
8.40
8.40
8.40
8.40
Operation
and Maint.
Costs $/cfm
0.51
0.51
0.51
0.51
0.51
**
***
Based on information from questionnaires, a facility of this size would have control devices cleaning
about 550,000 cfm of gases, therefore, subtracting the loading and unloading facility air flow
the balance of air flows would be used for conveyor hoods, transfer points, silos, cleaning, weighing,
etc. as the grain passes in and out of the terminal.
50-75 percent of air flow is recirculated depending on the type of dryer.
In most cases, the system used here will be the same system used for unloading.
-------
TABLE 6-2. CAPITAL COSTS, ANNUALIZED COSTS, AND COST EFFECTIVENESS (cont)
oo
Process
Receiving
Truck
Rail
Barge
Handling
Shipping
Land (2)
Ship (3)
Emissions to
Meet NSPS
(T/yr)
3.3
7.8
5.7
14.1
0.5
53.5
Emission
Reduction
(Tons/yr)
61.5
147.0
107.7
691.5
8.5 (Assume
837.5
Capital
Cost
($)
168,000
252,000
336 ,000
2,016,000
same unit as rail
3,504,000
Annual
Cost
($/yr)
28,021
42,032
56,043
336,258
unloading)
725,050
Cost
$/ton
456
286
520
486
866
Drying
12.7
620.9
263,000
57,000
92
(1) Based on using air pollution control systems for 3-3500 bu/hr dryers and having to dry all grain handled to
meet contract specifications.
(2) These emissions would probably be recovered from the truck or train unloading system as is done with most
port facilities that ship by land. Therefore, in this model, these emissions were added to the rail loading
system as it is very unlikely that only truck loading is done at a port terminal.
(3) Includes cost of control devices, choke type pouring spout, and heavy structural modifications to
shipleading dock.
-------
TABLE 6-2. CAPITAL COSTS, ANNUALIZED COSTS, AMD COST EFFECTIVENESS
Process
Receiving
Truck
Rail
Barge
Handling
Shipping
Land
Ship
Drying**
Percent of
Throughput
20
45
35
100
1
98
100
Parti cul ate
Emission
Factors
(Ib/T)
1.0
1.0
1.0
1.7
1.0
1.0
1.1
Uncontrolled
Emissions
(T/yr)
240
540
420
1,680
12
1,188
1,320
Estimated
Collection
Effectiveness
Before NSPS (%)
73
73
73
58
25
25
52
Emissions
Before NSPS
(T/yr)
64.8
145.8
113.4
705.6
9.0
891.0
633.6
Estimated
Collection
Efficiency
for NSPS(%)
95
95
95
98
94
94
98
-------
are shown in Table 6-2. These costs were updated to August 1982 dollars
using the Chemical Engineering plant cost index and company and vendor
data in 1982 dollars.1,2,3,4,5 Tne original costs were presented
in the NSPS support document and were calculated based on January 1976
dollars.1 Table 6-2 also presents the emission reduction resulting from
application of control techniques. These reductions are based upon the
difference between the levels reported in the NSPS support document
before NSPS proposal and NSPS.
6.1.1 Particulate Control
For each of the particulate control systems shown in Table 6-1, no
credit was taken for any recovered grain dust even though most companies
report selling the dust for $10-24 per ton.7.8.9.10 For the model plant
shown in Table 6-1, the dust recovered from the various control systems
(except for the ship loading) would reduce the annual operating costs
approximately 5 percent if the dust was sold at a minimum price of $10 per ton.
Actual capital costs were obtained from several companies and vendors
for the control devices associated with the facilities subject to the NSPS.
Most companies reported the total capital costs for all control systems
and based on total air flows required for these facilities, a dollar per
cubic feet per minute (cfm) relationship was developed (see Table 6-1).
This relationship compared favorably with vendors' engineering estimates
for similar control systems.3.4.5 The capital costs shown for each
affected facility in Table 6-2 are based on this single cost per cfm.
The capital cost for material handling control systems may be less than
6-5
-------
some of the other more elaborate control systems for the loading or
unloading facilities, but the total costs are still representative of
the actual total costs of control. Development of more specific capital
costs for each affected facility would be difficult because the capital
costs for these affected facilities depend greatly on site specific
requirements.
The capital costs for the dryer system were developed from vendor
information for some recent installations and reflects the difference
in costs between a dryer that meets NSPS versus a dryer without a screen
column control system.3>5 jhe model plant includes three 3500 bu/hr
dryers through which all of the grain processed would be passed. These
systems are usually designed so that each dryer can be fed and discharged
at 15,000-20,000 bu/hr. They are designed in this manner because most of
the grain coming to port facilities has been dried once and usually all
the grain needs is an additional 1 or 2 percent of drying to meet
contract specifications compared to 5 to 6 percent at country elevators or
inland terminals.
The cost effectiveness for each affected facility is shown on Table 6-2.
The cost effectiveness results do not reflect any credit for grain dust
sold. A separate cost-effectiveness for land loading facilities was not
calculated because most land loading facilities use the same control system
for loading and unloading as port terminals. Therefore, the emissions from
loading were added to the rail unloading systems (rarely do port facilities
load trucks) which is included in the cost-effectiveness for this affected
facility.
6-6
-------
One should note that the cost-effectiveness data shown on Table 6-2
are prepared as if the costs of removing the dust are solely due to the
NSPS. Actually, much of the cost should be ascribed to minimizing
explosions and improving worker exposure. Operators of grain elevators
have been advised and are keenly aware that dust generation, if not
controlled, can cause severe explosions. One of the major recommendations
of the National Materials Advisory Board, investigating grain elevator
explosions, was to advise all grain elevators to control dust generation
and remove airborne dust from all grain processes.6 Furthermore, it was
recommended by the Academy that cost-effectiveness studies be conducted on
the cost of adding dust removal and control systems versus the potential
dollar loss if no action is taken.
6-7
-------
REFERENCES
1. Standards Support and Environmental Impact Statement, Volume I:
Proposed Standards of Performance for Grain Elevator Industry:
EPA 450/1-77-OOla. January 1977.
2. Telecon: Iversen, R., with R. Nolan, R. S. Fling and Partners, Inc.,
Minneapolis, Minnesota. Discussion of capital costs of affected
shipping facilities. November 17, 1982.
3. Telecon: Iversen, R. with H. E. Bland, Aeroglide Corporation,
Raleigh, N. C. Discussion of capital, installation, and operating
costs for grain dryers. October 20, 1982.
4. Telecon: Iversen, R., with B. Panning, Carter-Day, Minneapolis,
Minnesota. Discussion of capital, installation, and operating costs
of fabric filters for grain elevator facilities, October 21, 1982.
5. Telecon: Iversen, R., with L. Funk, Carter-Day, Minneapolis,
Minnesota. Discussion of capital, installation, and operating costs
for grain dryers.
6. "Prevention of Grain Dust Explosions," National Materials Advisory
Board, Publication NMAB-2. National Academy Press, Washington, D.C. 1982,
7. Questionnaire Response, Cargill, Inc., Toledo, Ohio, October 20, 1982.
8. Questionnaire Response, North Pacific Grain Growers, Inc., Kalama,
Washington. August 6, 1982.
9. Questionnaire Response, Louis-Dreyfus Corporation, Portland, Oregon,
August 3, 1982.
10. Questionnaire Response, United Grain Corporation, Vancouver, Washington,
August 9, 1982.
6-8
-------
7. ENFORCEMENT ASPECTS
EPA Regional Offices, States and local agencies, and companies subject
to the NSPS were contacted to determine any problems with either enforcing
or complying with the NSPS. Discussions with EPA offices and State and
local agencies indicated that there are no major problems in enforcing
the NSPS. The major concern in enforcing the NSPS comes mainly from the
ship loading operations, because it is difficult to determine where to
read opacities coming out of the hold of a ship. The hold opening may
be 40 feet by 40 feet or more on large bulk carriers and it is sometimes
difficult to position oneself correctly to read opacities. Also, wind
currents may pick up dust that has settled on the grain in the ship's
hold and combine these with the emissions from the loading operation.
Despite these problems with shiploading, good loading practices and
well controlled and maintained equipment will keep emissions to a
minimum. Also, an experienced opacity reader should be able to find a
position that allows the reader to make sensible opacity readings even
under somewhat difficult circumstances.
Weather conditions are a problem that can present a unique situation
which is difficult to control. If loading is proceeding in an area where
PM emissions will cause problems to the environment or surrounding area
(for example a nearby residential area), tarps may have to be used to
reduce this effect. However, tarps cannot be used during the "topping-off"
7-1
-------
process and the enforcement agency will have to use powers of persuasion
and common sense to be sure that the loading'operations are being conducted
by the loading operators as cautiously as possible under the circumstances
to minimize PM emissions.
Company personnel contacted on plant visits during this review
indicated that, except for ship loading, they have no problems complying
with the NSPS. The companies also commented that they have not experienced
any problems in interpreting the NSPS or degradation in terms of emissions
or operations since the initial installation of the control systems.
Enforcement agencies have used reasonable judgment by choosing 4 or 5
key control systems (out of 20-40) when they have required compliance
tests (especially for Method 5) and if these systems meet the NSPS,
it is assumed the others are in compliance.
7-2
-------
8. ANALYSIS OF POSSIBLE REVISION TO THE STANDARDS
The EPA Regional Offices, State and local agencies, and industry
were contacted to determine the number and location of new or modified
facilities subject to the NSPS. Available NSPS compliance test data
and opinions of control agency and industrial personnel were solicited
regarding all facets of the NSPS. As shown in Chapter 5, the limited
amount of data subject to the NSPS indicate that all are in compliance
with the NSPS. No new control technology has emerged since the inception
of the NSPS. The only concern of control agency and industrial personnel
was meeting the ship loading NSPS. No difficulties have been reported
in terms of enforcing the NSPS, but there has been some confusion by
some agencies on the modifications section of the NSPS.
This chapter will analyze possible revisions to the NSPS for each
affected facility.
8.1 POSSIBLE REVISION TO NSPS
8.1.1 Truck Loading
No truck loading operations were viewed during plant visits because
truck loading is more predominant at country elevators and inland terminals
and no truck loading facilities were found that were subject to the NSPS.
Because the costs are still expected to be reasonable and no difficulties
in meeting the truck loading standard have been reported by control
agency or industry personnel, there appears to be no need to revise the
NSPS for truck loading.
8-1
-------
8.1.2 Truck Unloading '
Several truck unloading facilities were'seen in operation during
plant visits. All truck unloading station enclosures were open at each
end so that a truck could be driven through the enclosure to where the
truck's tailgate would be in the correct position over the receiving
hopper. In the best truck unloading stations, doors on the opposite end
of the enclosure from the truck's position would automatically close or be
closed by the operator before the truck was raised and the grain dumped.
All stations observed with closing doors at one end met the standard but
those truck unloading stations open on both ends rarely met the NSPS and
never met the NSPS if any wind was blowing. Two State agencies provided
written inspection reports that stated that the NSPS truck unloading
facility in their State met the NSPS.
One could totally enclose the truck unloading station. However,
this would require considerable addition to the building to handle the
trucks being raised, thus increasing the capital costs significantly.
Also safety would be questioned because trucks have occasionally slipped
the safety devices and fallen. In a total enclosure this could be dangerous
and cause costly damage. Considering the small decrease in emissions
for a total enclosure versus the enclosure with doors on one end, total
enclosure does not appear cost-effective.
Because the costs are reasonable and no difficulties in meeting the
standard have been reported by control agencies or industry personnel
for those facilities using end door closures, there appears to be no
justification for revising the NSPS for truck unloading.
8-2
-------
8.1.3 Rail car Loading
No railcar loading operations were seen during plant visits. Most
railcar loading occurs at inland terminals and no railcar facilities
were found that were subject to the NSPS. Because the costs are still
expected to be reasonable and no difficulties in meeting the standard
have been reported by control agency or industry personnel, there appears
to be no need to revise the NSPS for railcar loading.
8.1.4 Railcar Unloading
Several railcar unloading stations were observed during plant visits.
All stations observed (uncertified Method 9 opacity readings) met the
NSPS. One State sponsored Method 5 compliance test on the control device
met the NSPS. Two State agencies provided written inspection reports
that state that the NSPS railcar facility in their State met the NSPS.
Most railcar unloading stations are large enclosures open on each end.
Usually emissions are only generated at the beginning of dumping a car
as the initial surge of grain hits the bottom of the hopper. Those
emissions escaping the hopper control system usually fall out within the
railcar unloading enclosure and rarely escape to the atmosphere.
One could require doors on the enclosure ends and that they be
closed during the unloading operation; however, such enclosures would
significantly slow operations. Most large terminals are designed to
handle large quantities (bushels) of grain and the railcar unloading
stations at those large terminals are designed to handle unit trains
(100 cars or more) so that unit handling costs are kept to a minimum.
8-3
-------
Besides the extra capital expense of installing the doors, the cost to
the company of having to connect and disconnect rail cars so that the
doors could be closed would be significant and negate the efficiency of
using unit trains.
Because the costs are reasonable and no difficulties in meeting the
current standard have been reported by control agency or industry personnel,
there appears to be no need to revise the NSPS for rail car unloading.
8.1.5 Barge or Ship Unloading
n Barge unloading was observed in operation during plant visits and met
\ .1 ^
kfr ^ ' NSPS levels. All the unloading facilities had equipment designed to
./ .'»**
V ' ' '
* '^ meet the NSPS even though they were not required to meet the NSPS. Two
State agencies reported that the NSPS barge unloading facility in their
State met the NSPS. No official data were provided other than written
inspection reports from on-site inspectors. Barges are unloaded by a
marine leg which is essentially a bucket elevator that is placed on the
grain which picks up the grain and transfers it to a conveyor system and
to storage. The enclosed top half of the marine leg is connected by
ductwork to a control device. The NSPS requires that the flow rate to
exhaust the marine leg be a minimum of 40 ft3 of air per bushel of
grain unloaded. No ship unloading was observed because it is rare for a
grain ship to be unloaded in the United States. However, the same technique
would be used for ship unloading as is used in barge unloading.
8-4
-------
Marine legs are the only unloading technique used in the United States
at this time. There were some references noted in trade periodicals that
some foreign ports may use pneumatic systems to unload grains, but no
information could be found on this technique during this review.
Because the costs are reasonable and no difficulties have been
reported in meeting the standard by control agency or industry personnel,
there appears to be no need to revise the NSPS for barge or ship unloading.
8.1.6 Barge or Ship Loading
No barge loading facilities were found that were subject to the
NSPS. Therefore, none were seen during plant visits as most barge loading
occurs at inland waterway terminals. However, barge loading and ship
loading have similar loading equipment and emission control systems
(discussed next).
Several ship loadings were seen during plant visits. All the facilities
visited met the NSPS (uncertified Method 9 opacity readings). Two State
agencies reported that ship loading facilities in their State met the
NSPS. No official readings were provided other than written inspection
reports from on-site inspectors. Observations during plant visits showed
that with a commitment to good loading practices and control techniques
(discussed next), the ship loading facility can meet the NSPS.
There are essentially two types of loading spouts used in ship
loading operations. Each requires a similar but somewhat different loading
technique if PM emissions are to be kept to a minimum. One technique, used
8-5
-------
mostly by older facilities, utilizes a standard telescoping metal pouring
spout that is about 18 inches or more in diameter and 50-80 feet long.
Using this type of pouring spout usually requires that the ship's hold
be covered with a tarp or similar material and the pouring spout inserted
between the edge of the ship's hold and the tarp. The tarp reduces the PM
emissions that are generated when the grain drops from the pouring spout
into the ship's hold. However, when the grain fills the hold to within
the last 25 percent from the top, the tarp has to be removed so the operators
can see to "top off" or be sure the hold is completely filled properly, the
ship balanced, and the grain as level as possible. If the operators did
not finish filling the uncovered hold carefully (described in the next
paragraph) significant emissions can be discharged to the atmosphere.
In completing the filling of the ship's hold the pouring spout is
extended to within a few inches of the grain surface. This reduces the
free-fall distance through the ambient air and keeps emissions to a
minimum. Also, this same loading technique can be used for the entire
ship filling operation without using a tarp. Again, proper operator
control is the key to controlling emissions and readjustment of the spout
is necessary from time to time; unfortunately the loading personnel who
operate this equipment are quite independent and may or may not follow
procedures that keep emissions to a minimum.
The second technique for controlling ship loading emissions is the
use of a choke feeder. This system also uses a telescoping pouring spout
8-6
-------
but has a larger and more complicated filling spout which is usually
larger in diameter than a conventional spout. The choke feeder itself
is located inside the filling spout and is a cylindrical unit that has
large holes in the sides but closed on the bottom. Thus, the grain
comes down the spout and hits the choke feeder which fills up and then
slowly runs out the holes in the sides. The choke feeder is surrounded
by another cylindrical unit which allows an annular space between it and
the choke feeder. This annular space is under a negative pressure and
the emissions collected are removed by ductwork leading to a baghouse.
Considerable emissions are captured at the pouring spout. However, even
with this type of loading system and for the best results in reducing PM
emissions, the operator must keep the end of the pouring spout as close
to the pouring surface as possible to keep the grain free-fall to a
minimum.
At this time there does not appear to be any alternative control
techniques, thus, what is being used today is best control technology.
There is some development work being done using water, steam, and vegetable
oil which show promise of reducing dust emissions from grain handling.
However, none of these processes are operating on full scale operations
and have not been approved for grain shipments (those for human consumption)
by governmental agencies.
Another problem voiced mainly by State and local control agencies is
the difficulty in reading opacities during ship loading. The opening of a
ship's hold on a bulk tanker may be 40 feet by 40 feet or more. In
8-7
-------
addition, weather conditions can affect opacity readings considerably,
especially wind currents. The wind can swirl the dust plume around varying
the opacity greatly. Also, the wind can pick up the dust already settled
on the poured grain and add it to the pouring emissions. Sometimes it
is difficult to position oneself correctly to get the best possible
opacity readings. Lastly, there is not a specific or uniform method of
where (height above hold) one should read opacities as the PM emissions
leave the hold.
Even though some control agencies and industry personnel have
commented on the difficulty in meeting the ship loading NSPS, plant visits
and observations show that the NSPS can be met with proper loading techniques
and a well maintained control system, and all NSPS facilities are in compliance.
Therefore, there appears to be no need to revise the NSPS for the barge
or ship loading facility at this time, but these facilities should be
thoroughly studied again during the next review if these concerns persist.
8.1.7 Grain Drying
There are two types of grain dryers used in the industry; a column
dryer and a rack dryer. One column dryer was observed in operation
during the plants visits, and no visible emissions were seen. Also,
information on grain dryers provided by three State control agencies
show this affected facility can meet the NSPS. The column dryer feeds
grain from the top down through a vertical cylindrical perforated steel
plate column that has holes no larger than 0.094 inch in diameter. The
8-8
-------
hot gases come up the column through the grain and discharge the moisture
laden gases out through the holes. The rack dryer is similar except
that the grain passes through heated baffles through which hot gases are
passed. The rack dryer uses a 50 mesh screen or finer to capture particulate
emissions. Recently, another dryer introduced a rectangular mesh screen
with openings 0.0486 inch by 0.5 inch. One State control agency recently
conducted a Method 9 compliance test on this unit and determined that it
met the NSPS for grain drying.
Because the costs are reasonable and best control technology is
being used and no difficulties in meeting the standard have been reported
by State agency or industry personnel, there appears to be no need to
revise the NSPS for grain dryers.
8.1.8 Grain Handling
Grain handling covers all aspects of moving the grain to and from
the grain elevator processes as required. Grain elevators use conveyor
belts to move grain and elevator legs to lift the grain to the top of
the storage silos or the top of the head house to be cleaned, screened,
dried, weighed, and stored. Some new, modern elevators even use conveyor
systems to lift the grain instead of elevator legs. Most modern elevators
use completely enclosed conveyor belts and transfer systems. These are
all ducted to baghouses. The cleaning, screening operations, elevator
legs, and weigh hoppers are also enclosed and ducted to baghouses.
Observations made during plant visits, baghouse compliance tests at
two facilities, and reports by inspectors from two other control agencies
show that the grain handling facilities meet the NSPS.
8-9
-------
Because the costs are reasonable and best control technology is
being used and no difficulties in meeting the standard have been reported
by control agency or industry personnel, there appears to be no reason
to change the NSPS for grain handling facilities.
8.1.9 Control Devices
All NSPS facilities use baghouses as the control device to capture
particulate matter. Observations during plant visits, compliance tests
(see table in Chapter 5), and control agency reports indicate the control
device is easily meeting the grain loading and opacity standard. Other
types of control devices, such as scrubbers and electrostatic precipitators
(ESP) are not normally used because of the water pollution problems from
scrubbers and the potential for explosions with ESP's. Cyclones will
not meet NSPS requirements. Because the costs are reasonable and baghouses
are considered best control technology, and no difficulties in meeting
the standard have been reported by control agency or industry personnel,
there appears to be no reason to change the NSPS for control devices.
8.2 POSSIBLE REVISIONS TO MONITORING REQUIREMENTS
The NSPS does not contain any monitoring requirements for the various
affected facilities. Requiring monitoring and record keeping for each
affected facility could pose a heavy paperwork and cost burden on the plant
because of the large number of control devices used (for example, 36 at
one facility).
Most facilities reported that baghouses are checked daily for any
pressure drop changes, visible emissions, and potential maintenance problems.
This is to assure that the baghouse and attendant equipment are operating
8-10
-------
properly. The facilities visited and those responding to our quesionnaire
did not report any abnormal or unusual operating and maintenance problems
with the control devices. Malfunctions occur rarely and no records are kept.
If a malfunction occurs, the entire system is shut down immediately.
It should be emphasized that these facilities and their manager are
acutely aware that grain dust causes explosions. Therefore, plant inspections
revealed clean (housekeeping) plants with computerized systems to monitor
plant operations. Newer facilities have interlocks so that if a malfunction
occurs within that process, the whole system shuts down. In fact, in some
larger facilities every bearing is connected to a heat sensor and a computer
which prints out the bearing temperature every few minutes. If the temperature
goes above a set point, an alarm sounds and the process affected shuts down
automatically. Grain elevators now monitor dust emissions and mechanical
operations quite carefully for safety reasons.
Because companies monitor themselves closely for safety and other
reasons, there appears to be no reason to revise the NSPS and require
monitoring.
8.3 EXTENSION TO OTHER SOURCES
The NSPS covers all significant emissions in grain elevators.
There are very few, if any, fugitive sources that are not controlled in
NSPS facilities. This again is mainly due to safety considerations.
Therefore, there is presently no reason to revise the NSPS to include
other sources as all appear to be covered under the present NSPS.
8-11
-------
There have been concerns expressed by control agencies and enforcement
personnel that the size cutoff for grain elevators mandated by Congress is
allowing a large percentage of grain elevators not to be regulated by the
NSPS. Therefore, it is recommended that Congreee should consider reducing
the cutoff size for grain elevators when Congress discusses changes to the
Clean Air Act.
8.4 EXTENSIONS TO OTHER EMISSIONS
The NSPS regulates only PM emissions from grain elevators. As all
the functions in grain elevators are grain handling processes, no chemical
changes are made in the product. Therefore, PM is the major pollutant.
The only other types of pollutants will be small amounts of combustion
products that can be emitted from the grain dryers. Dryers usually
operate only about 3 months per year and burn natural or propane gas.
Because there are no emissions other than PM to be controlled,
there is no reason to change the NSPS.
8-12
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-450/3-84-001
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
A Review of New Source Performance Standards for
Grain Elevators
5. REPORT DATE
January 1984
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
DAA for Air Quality Planning and Standards
Office of Air and Radiation
U. S. Environmental Protection Agency
Research Triangle Park. North Carolina 27711
13. TYPE OF REPORT AND PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
EPA 200/04
15. SUPPLEMENTARY NOTES
16. ABSTRACT
This report reviews the current Standards of Performance for New Stationary
sources: Subpart DO - Grain Elevators. Emphasis is given to the state of control
technology, extent to which plants have been able to meet current standards,
experience of representatives of industry and of EPA officials involved with
testing and compliance, economic costs, environmental and energy considerations,
and trends in the grain elevator industry. Information used in this report is
based on data available as of March 1983.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS C. COSATI Field/Group
Air Pollution
Air Pollution Control
New Source Performance Standards
Grain Storage
Grain Elevators
Grain Handling
Grain Mills
Air Pollution Control
13B
rRIBUTION STATEMENT
Unlimited
19. SECURITY CLASS (This Report)
Unclassified
20. SECURITV CLASS (This page)
21. NO. OF PAGES
102
22. PRICE
SPA Form 2220-1 (Rev. 4-77)
EDIT'ON IS OBSOLETE
------- |