Seed Separation and Processing
Seed Separation and Processing Operations
Seed separation and processing encompasses a large number of distinct stages. Processing is needed for all kinds of seeds, including grains and cereals (e.g., corn, rice, wheat, oats and barley), soybeans, oilseeds and pulses, vegetables and other crop types, grass seed, and flowers and ornamentals. During seed separation and processing, raw seed is separated from contaminants (such as weeds, plant material, trash, insects and other seed types), cleaned and prepared for commercial sale. Seed preparation and conditioning processes include:
- Threshing and pre-cleaning (winnowing, scalping, debearding)
- Basic and fine cleaning
- Grading (e.g., gravity separation)
- Seed treatment/seed coating (film coating, pelleting, encrusting)
- Seed packaging
Seed processing and conditioning equipment includes:
- Length separators
- Gravity separators
- Precision sizing equipment
- Grain dryers
- Feed milling equipment
- Film coating systems
Material handling and packaging equipment used for seeds and grains include:
- Bucket elevators
- Belt conveyors
- Vibrating conveyors
- Continuous cup elevators
- Drag conveyors
- Bagging scales
- Bulk storage systems/grain silos
Dust Control Solutions for Seed Conditioning
RoboVent offers robust and innovative dust control solutions for all stages of the seed processing industry, including seed cleaning, drying, fine cleaning, grading/gravity separation, seed treatment/seed coating, silo filling/storage and seed packaging. A RoboVent solutions engineer can design an effective dust control system for your seed conditioning application that fully meets ACGIH and NIOSH recommendations. We can help you:
- Evaluate your dust-producing processes and combustion risk.
- Design and install a dust control solution tailored to your seed conditioning application.
- Maintain your dust collection system for maximum longevity and efficiency.
RoboVent Senturion is a heavy-duty, versatile dust collector suitable for seed conditioning applications. Senturion features:
- Advanced filters and a space-saving design for a footprint that is 20% smaller per CFM compared to traditional dust collection systems.
- Modular design to allow the unit to be fit into the space envelope for the facility.
- Heavy-duty cabinet construction with powder coating inside and out for use in outdoor conditions.
- Optional abrasive-resistant intakes and baffle systems to protect the dust collector filters.
- Maintenance-saving features to reduce downtime.
Dust Control Regulations for Seed Conditioning
Companies involved in conditioning, processing, coating, transporting and packaging seeds and grains must meet general Occupational Safety and Health Administration (OSHA) regulations related to worker safety along with specific OSHA and National Fire Prevention Association (NFPA) standards for combustible dusts. Seed coaters may have to follow additional Environmental Protection Agency (EPA) regulations related to release of pesticides into the environment. Relevant standards include:
- Combustible dusts: Combustible dusts are regulated under OSHA’s General Duty Clause (Section 5(a)(1)) with additional requirements under the Hazardous Locations (§1910.307), Hazard Communication (§1910.1200) and Housekeeping (§1910.22) standards. In addition, manufacturers dealing with combustible dusts must follow National Fire Protection Association (NFPA) standards for prevention of fires and explosions. Seed and grain dust fall under NFPA 61, Standard for the Prevention of Fires and Dust Explosions in Agriculture and Food Processing, as well as NFPA 654, Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing and Handling of Combustible Particulate Solids. Dust collection systems for seed conditioning dusts must also meet NFPA 68, Standard of Explosion Protection by Deflagration Venting, and NFPA 69, Standard on Explosion Preventing Systems. OSHA’s Combustible Dust National Emphasis Program (NEP) outlines policies and procedures for inspecting workplaces that create or handle combustible dusts.
- Nuisance dusts: Many seed conditioning dusts fall under the OSHA definition of “nuisance dusts,” which are regulated under the general particulate matter concentration limits set by OSHA. The general limit for “Particulates Not Otherwise Regulated” (PNOLs) is 15 mg/m3 (8-hour TWA limit) for total particulate and 5 mg/m3 for respirable particulates. Employers must also follow general Housekeeping standards (OSHA 1910.22, Walking-Working Surfaces) to prevent accumulation of dust on surfaces. If the dust contains fertilizers, pesticides or other substances used for seed coating, employers may also have to consider specific OSHA Permissible Exposure Limits (PELs) for those substances.
- Other Regulations Specific to the Seed Conditioning Industry: OSHA has issued additional regulations for Grain Processing Facilities (1910.272). These regulations are primarily concerned with the high combustion risks of grain dust. Grain handling facilities must have a written plan for control of fugitive grain dust, including engineering controls and housekeeping measures to prevent the accumulation of dust both in the air on surfaces.
Considerations in Selecting a Dust Control Solution for Seed Conditioning Dust
Dust control solutions for the seed conditioning industry must be designed to handle large volumes of dust and reduce the very real risk of combustion. In addition, they must fit within the space constraints of the seed conditioning tower or facility. A well-designed dust collection and containment system will improve facility safety while reducing maintenance requirements for the dust collector. Here are some of the primary considerations in dust collector design for seed conditioning.
Combustible Dust Control
Combustion risk is the number one concern in the seed conditioning industry, and the dust collector must be designed accordingly. This may include elements such as:
- explosion vents for safe venting of the energy from a dust collector explosion
- isolation valves to prevent a pressure wave from propagating back into the facility
- rotary airlock to prevent dust in the collection bin from being used to fuel an explosion
- heavy-duty doors and side panels
Seed and grain storage will require a bin venting dust collector. The dust collector is mounted directly to the top of the bin, hopper or silo to collect airborne particulate within the enclosure. Bin venting is necessary to prevent a combustible dust explosion within the storage unit. Both the silo/storage bin and the dust collector must be equipped with deflagration vent panels for safety.
Seed conditioning towers and seed processing facilities may have limited space for a dust collection system. Cartridge-style dust collectors are more compact than baghouse dust collectors and well suited for most seed conditioning processes. Look for space-saving features such as:
- Modular design, which allows the unit to be designed to meet specific space requirements (e.g., vertical vs. horizontal design).
- Advanced filter design (with more usable filter media per cartridge), which enables a more compact design for the dust collector.
If the dust collection system will be outdoors, the dust collector cabinet and ductwork must be built to withstand the elements. Look for:
- Heavy-duty cabinet construction with powder coating inside and out.
- Ductwork materials and tubing designed for heavy-duty use in outdoor environments. Instead of poly tubing, the dust collector may need copper or stainless steel tubing that will withstand heat, moisture and UV exposure.
Abrasive Dust Control
The abrasive nature of some seed conditioning dusts, along with high overall volumes of dust, creates special challenges for the design of the dust collection system. Dust collectors for seed conditioning processes producing abrasive dust are likely to require modifications to protect the filters and extend the life of the dust collector. These modifications may include:
- Abrasion-resistant air intakes
- Drop-out boxes to allow coarse, heavy dust to fall out of the airstream before it hits the filters
- Baffles within the ductwork, intake and filter cabinet to protect the filters
- High-quality filter media designed for use with abrasive dusts
Industrial dust collectors used in seed conditioning applications should have features to help reduce maintenance and enable changing of the collection bins without shutting down the unit. Look for:
- Vertical filter design and an advanced filter pulsing system to enable efficient shedding of excess dust from the filters to extend filter life.
- Flexible discharge options, including options for multiple drums or bins or connection to a conveyor system for collection and removal of dust.
- Rotary valves between the hopper and collection bin that enable bin changing without shutting down the unit.
- A bin sensor system, which can be added to the collection bin to monitor dust levels and provide an alert when the bin needs to be changed.
Dust Collection Challenges for Seed Separation and Processing
For the seed separation and processing industry, product cleanliness is paramount. Contaminants must not be allowed to reenter the processing lines, and fugitive dust must be controlled so that the final product is clean and dust-free for buyers. Many seed conditioning processes produce high volumes of coarse, abrasive dust, which creates challenges for dust collection equipment. In addition, dust produced by seeds and grains is highly combustible. Dust control challenges for seed separation and processing include:
- Combustion risk: Combustion is the biggest risk faced by the seed processing Many of the dusts created during seed separation, processing and conditioning are highly combustible. That means they can generate an explosion when allowed to concentrate enclosed areas such as a grain silo, bin or conveyor system. In fact, most grain dusts are considered to be highly combustible. Special care must be taken when collecting combustible seed conditioning dusts to minimize the risks of an explosion inside the dust collector.
- Abrasion: Dust produced by some seed processing activities (especially pre-cleaning, destoning, etc.) is abrasive and may include materials such as small stones and other debris. Abrasive dust creates a lot of wear and tear on dust collection equipment and filters.
- Microbial growth: Seed and grain dusts create an ideal breeding ground for many different kinds of microbes, including yeasts, molds and bacteria. Many dangerous molds thrive on grain products such as corn and wheat. Dust control is important to reduce the spread of microbial pathogens through the seed separation and processing supply chain. Uncontrolled dust on surfaces can become a breeding ground for dangerous yeasts, molds and bacteria. If this dust is allowed to re-contaminate seed processing lines, pathogens can end up in the final product.
- Health and safety hazards: Heavy dust created by seed separation and processing operations can cause lung irritation or trigger asthma or allergies if inhaled. Uncontrolled dust of any type is also a housekeeping and sanitation consideration. While dust exposure may be less of a problem for processes that are conducted in open-air environments or by primarily robotic processes, it is still important to keep fugitive seed and grain dust away from areas where it can be inhaled. Dust created during seed coating (filming, pelleting or encrusting) or while moving and transporting coated seeds may be hazardous or toxic when inhaled. Seeds may be coated with fertilizer, pesticides (such as neonicotinoids), fungicides (e.g., “red dust”/Captan/Metalaxyl Thiram), micronutrients, biostimulants or microbial coatings that promote plant growth. Seed pelleting and seed encrusting are used to create a protective shell around the seed and increase size, weight and uniformity for easier planting. Inhaling pesticides, fungicides and fertilizers may cause acute respiratory distress and long-term health impacts. Workers exposed to fertilizer dust are at higher risk of lung cancer and emphysema. “Red dust” fungicides have been linked to neurotoxic and developmental impacts.
- Environmental concerns: “Dust off” of coating materials such as red dust from treated seeds may also pose an environmental concern. Fugitive pesticide dusts, especially neonicotinoids, become an environmental problem when allowed to escape into the atmosphere. Fugitive neonicotinoids in the environment have been implicated as a possible cause of large die-offs of wild bee colonies in recent years. Fungicides and pesticides also have detrimental environmental impacts when they wind up in aquatic ecosystems. Other impacts on the environment have not been fully studied. It is best practice in the seed coating industry to minimize the release of fugitive red dust and other coating dusts into the environment.