| Wheat mill run pellets | [German version] |
Table of contents |
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| General: | ||
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Product information | |
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Packaging | |
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Transport | |
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Container transport | |
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Cargo securing | |
Product information
Product name
| German | Weizenprodukt-Pellets |
| English | Wheat mill run pellets |
| French | |
| Spanish | |
| Scientific | Triticum spec. |
| CN/HS number * | 2302 30 ff. |
(* EU Combined Nomenclature/Harmonized System)
Product description
The following methods may be used in the production of vegetable pressing residues:
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pressure filtration (pressing: cold and hot pressing) |
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solvent extraction |
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pelletization |
Unlike wheat bran pellets, wheat mill run pellets are produced from wheat mill runs, i.e. residues from the wheat milling process with a considerable flour content. Suitable binders (e.g. 1 – 3% of molasses, fat or colloidal clays) are added to this material and the composition is then pressed under high pressure in pelletizing machines or extruders to form cylindrically shaped pellets. From a transportation standpoint, pellets generally have the same characteristics as the original plant residues, in particular in terms of the product’s oil and water content. A distinction is drawn between expeller pellets and extraction meal pellets depending on their origin.
The oil content of wheat mill run pellets depends upon the comminution rate of the particular residues.
Quality / Duration of storage
Wheat mill run pellets are white in color.
Product intended for shipping must be adequately matured. The time required for maturing is determined by the oil content. On the other hand, stored product from the previous year’s harvest should not be accepted.
The consignor must provide certificates relating to the moisture and residual oil content and the maturing time of the product. Confirmation or certification should also be obtained as to whether the starting material is expeller or extraction meal. Residual oil contents of < 1.5% indicate extraction meal, while higher oil contents indicate expeller.
Intended use
Wheat mill run pellets are primarily used as a feedstuff.
Countries of origin
This Table shows only a selection of the most important countries of origin and should not be thought of as exhaustive.
| Europe | |
| Africa | |
| Asia | |
| America | USA |
| Australia |
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Packaging
Pellets are mainly transported as bulk cargo. Only exceptionally is the product transported as bagged cargo (in very small quantities).
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Transport
Symbols
 Bulk cargo |
 Spontaneously combustible, Class 4.2 IMDG Code |
Means of transport
Ship, truck, railroad
Container transport
Bulk containers subject to compliance with lower and upper limits for water and oil content and the maturing time of the product and water content of the container floor (see RF Self-heating, possible fire hazard due to solvent residues).
Cargo handling
Do not unload very hot product with hydraulically operated grabs as the hydraulic lines are not capable of withstanding such elevated temperatures. Use only cable-operated grabs for spontaneously heated product.
Stowage factor
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approx. 1.6 m3/t [1] |
Angle of repose
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approx. 40° [1] |
Grain size
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Diameter 6 mm, length approx. 13 mm |
Stowage space requirements
Cool, dry. Mechanical ventilation of the stowage spaces must be possible. Do not stow over heated double bottom tanks, close to the engine room bulkhead and pipework which may become hot.
Segregation
Tarpaulins
Cargo securing
In the case of maritime transport, the IMO (International Maritime Organization) „Code of Safe Practice for Solid Bulk Cargoes“ must be complied with.
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Risk factors and loss prevention
RF Temperature
Wheat mill run pellets require particular temperature, humidity/moisture and ventilation conditions (SC VII) (storage climate conditions).
Favorable travel temperature: 5 – 25°C [1]
In tropical ports, temperatures of 25 – 55°C may occur in the products to be loaded.
The temperature must constantly be measured at various depths in the hold during the voyage. If the temperature rises above 55°C and any further increase is observed, countermeasures must be taken, e.g. tight closing of all hatch openings and injection of CO2 or inert gas (see RF Self-heating).
The enzymes which initiate and intensify fat degradation and thus the self-heating process reach optimum levels of activity at temperatures of 35 – 40°C, i.e. temperatures which are easily reached within the heaped cargo. The travel temperature should thus be between 5 and 25°C. Temperatures of up to 30°C are also admissible for short periods. However, these conditions are difficult to maintain during an ocean voyage, as a consequence of which very careful attention must be paid to ensuring that at least the critical water content of the product is not exceeded in order to avoid self-heating to the greatest possible extent.
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RF Humidity/Moisture
Wheat mill run pellets require particular temperature, humidity/moisture and ventilation conditions (SC VII) (storage climate conditions).
| Designation | Humidity/water content | Source |
| Relative humidity | 70% | [1] |
| Water content | 0.5 – 11% | [1] |
| Maximum equilibrium moisture content | 70% | [1] |
In some cases, the water content of wheat mill run pellets may approach zero.
Pellets must be protected from all forms of moisture (seawater, rain and condensation water), since moisture encourages mold, mustiness and self-heating.
Moisture promotes self-heating brought about both by hydrolytic/enzymatic degradation and by microorganisms and may be the result of an excessively high product water content or alternatively of external influences (excessively high relative humidity (critical equilibrium moisture content 75%), water splashes, rain).
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RF Ventilation
Wheat mill run pellets require particular temperature, humidity/moisture and ventilation conditions (SC VII) (storage climate conditions).
Recommended ventilation conditions: surface ventilation.
As with bulk cargoes of expeller, pellets are also often not ventilated.
In order to avoid moisture damage on the surface of the cargo, ventilation must not be performed with cold external air. The ventilation system must then be switched to return air.
Due to the principal causes of self-heating in vegetable pressing residues, two problems arise with regard to ventilation:
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At an excessively high product water content, localized overheating caused by enzymes or bacteria results in self-heating. The resultant heat must be dissipated by constant ventilation by means of a good ventilation system. Drying by ventilation is useful, but its effectiveness is questionable because, as heating proceeds, increasingly large quantities of water vapor are released. The activity of the initiating microorganisms is not suppressed by nonventilation of the hold as some of the thermophilic (= heat-loving) bacteria are anaerobic organisms (which require no oxygen supply to stay alive). |
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In a product with an excessively low water content, which must be expected to undergo oxidative fat cleavage, the supply of oxygen must be interrupted as this process would otherwise be accelerated. Any attempt to cool the cargo by ventilation supplies air, so further promoting the oxidation process. |
Ventilation is helpful in the first case, but hazardous in the second. The correct ventilation measures may only be implemented if the characteristics (loading temperature, water content, duration of prior storage) of the cargo are known. However, if a large batch is made up of various sub-batches, it is entirely possible for both the above-stated causes to occur in the same heap of cargo.
Solvent vapors from pellets made from extraction meal are heavier than air and do not take the form of surface vapors; as a result, they cannot rise upwards and be dissipated by surface ventilation. They may theoretically be eliminated by ventilation only if the temperature of the cargo rises due to self-heating, causing the vapors to rise in the cargo, in which case, however, direct surface ventilation would be inappropriate (see RF Self-heating).
A certificate stating residual oil content, water content and maturing time should be demanded from the consignor.
If the oxidation processes under way in the hold are vigorous, it is not possible to dissipate the quantity of heat generated by ventilation. This particularly applies if a sub-batch susceptible to oxidation with a low water content is loaded next to a sub-batch with a high moisture content.
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RF Biotic activity
Wheat mill run pellets display 3rd order biotic activity.
They belong to the class of products in which respiration processes are suspended, but in which biochemical, microbial and other decomposition processes still proceed.
Care of the cargo must be aimed at limiting the autoxidative fat cleavage process and so preventing possible self-heating of the product.
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RF Gases
An increase in CO2 and CO content in the hold air indicates that a cargo fire has begun. CO2 has a smothering action on the seat of the fire because it displaces oxygen.
The vapors of the solvent used during production from extraction meal are denser than air and may thus accumulate in the lower parts of the hold.
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RF Self-heating / Spontaneous combustion
The oil content of wheat mill run pellets depends upon the comminution rate of the particular residues.
Wheat mill run pellets are liable to the risk of self-heating/spontaneous combustion.
Wheat mill run pellets are assigned to class 4.2, pursuant to the IMDG Code. All types and varieties of pellets, expellers and extracts fall within the class „Seed Cake“ under UN numbers 2217 and 1386.
Since oil content is of central significance to the risk of self-heating, it should be determined whether the pellets were made from expeller or extraction meal, as the residual oil content of extraction meal (< 1.5%) is substantially lower than that of expeller. The present oil content is indicative of a product based on expeller.
Smoking/open flames are prohibited during loading, discharge and access to holds.
Causes and promoting factors of self-heating are moisture, oxygen, elevated residual oil content, high fiber content and grain size.
Oxygen promotes oxidative fat cleavage. The principal cause underlying self-heating caused by oxidative fat cleavage is an excessively high residual oil content. In pellets, a residual oil content in excess of 7 – 10% promotes oxidation processes.
An elevated unsaturated fatty acid content in the residual oil constitutes a very serious storage risk as such fatty acids have a strong tendency to undergo autoxidation with (atmospheric) oxygen, plentiful supplies of which are also available in a feedstuff cargo, to form saturated fatty acids. This autoxidation, as a kind of flameless combustion, results in considerable evolution of heat which may result in a hazardous build-up of heat in the feedstuff cargo if the heat cannot be dissipated.
The maturing time before ocean transport is of great significance to the promotion of self-heating processes in pellets, with both excessively short and excessively long maturing times possibly being disadvantageous. On acceptance, pellets should thus exhibit temperatures which are only insignificantly (approx. 10%) above external air temperature. It must be ascertained whether the batch is from the previous year’s production. Unfavorable storage conditions over the period prior to shipping may mean that the product is already at elevated temperature when it arrives on board. Continuous temperature measurements are thus required during loading of the cargo.
The main risk for transport of any cargo which has heated ashore is that the product is loaded at temperatures of above 55°C and retains this temperature in the hold and, due to the poor thermal conductivity of the product, areas with a permanent heat build-up form for the entire duration of transport. The longer the duration of transport, the greater are the consequential losses arising from heating.
In the areas with a heat build-up of above 60°C, the autoxidation process of the feedstuff containing residual oil gradually begins and continues as the unsaturated fatty acids oxidize. The hot spots do not spread much further. The product does, however, dry out, as a result of which moisture migrates upwards from below and water vapor collects in the space between the surface of the cargo and the underside of the hatch covers or weather deck. This accumulation of water vapor combined with maximally airtight hatch covers is the most effective method of fighting fire, as any external supplies of oxygen are blocked off.
Pursuant to the IMDG Code/IMO, ships must be equipped with systems for injecting CO2 or inert gas.
The poor thermal conductivity of pressing residues is also of significance to self-heating. Self-heating may occur simultaneously at various points within the cargo and continue to such an extent that carbonization (release of hydrogen, leaving carbon behind) occurs. The resultant fine-pored carbon has the characteristic of starting to smolder when exposed to oxygen.
Due to the poor thermal conductivity of the product, temperature measurements to detect seats of risk are very difficult. Numerous measurements must be performed and some must also be taken within the heap. Surface measurements alone are not adequate.
The poor thermal conductivity also explains late detection of the seat of a fire. The particular risk is that the cargo burns within the heap without generating appreciable quantities of smoke. The seat of the fire carves out a cavity with the result that fatal accidents may occur when someone steps onto the surface of the cargo and breaks through into such cavities.
In order to be able to detect a cargo fire in good time, it is recommended to make regular gas measurements of the hold air. A rapidly rising CO2 content indicates increased microbial activity combined with evolution of heat within the cargo. This evolution of heat ultimately leads to the spontaneous combustion of the cargo, with evolution of carbon monoxide (CO). The presence of CO gas is considered the most reliable indication of a fire. Levels of 0.002 – 0.005 vol.% of CO in the air are deemed normal, with values rising to above 1 vol.% in a cargo fire.
On unloading, small flames may appear on the exposed surface of a heated cargo: volatile gases which have formed in the cargo over the course of self-heating and have a flash point of around 60°C have spontaneously ignited. These flames do not cause the remainder of the cargo to burn as the ignition temperature of most organic cargoes is of the order of 300 – 500°C. If such small flames or glowing areas of the surface occur in isolated areas, it is helpful to tip the last grab load back down into the area of the hold concerned, so smothering the flames.
The subsequent phases of self-heating possibly culminating in a cargo fire and the action to be taken are described in the article by „Capt. R. Becker: Course of self-heating processes in feedstuffs of animal or vegetable origin containing residual oil, Hamburg, 1996“.
It is possible to conclude from characteristics observable in the ship’s hold, such as temperatures, appearance and odor of the cargo, whether the product was loaded at too high a temperature and whether it has undergone self-heating with microbial spoilage and subsequent autoxidation.
The following features must be observed and recorded for this purpose:
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the flow behavior of the cargo in the heap (caked, free-flowing) |
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the color of the product (normal, brown to black) and the distribution of color differences in the product in the hold |
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the odor of the product (normal, healthy, fresh, musty, burnt) |
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the temperature and appearance of the cargo at various depths in the bulk load |
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the appearance of the cargo surface when the hatches are opened |
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the appearance of escaping smoke/fumes (steam is white, smoke from overheated product with a temperature of above 90°C is black) |
On the basis of this information, it is possible to conclude on the spot whether:
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the product was loaded too moist |
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the product was loaded at too high a temperature after a drying process (toasting) |
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the product was shipped shortly after production without complying with the maturing time |
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biogenic self-heating has occurred during the voyage as a result of metabolic processes in microorganisms |
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self-heating has occurred without a preceding biological self-heating process by chemical autoxidation of unsaturated fatty acids |
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the product was loaded in a discolored state (brown to black) as a result of drying processes (toasting) performed during manufacture |
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RF Odor
| Active behavior | Peanut pellets have a slight, pleasant odor, but should not be stowed together with odor-sensitive products. |
| Passive behavior | Peanut pellets are sensitive to unpleasant and/or pungent odors. Odor-tainted pellets are rejected by livestock (especially horses and cattle). |
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RF Contamination
| Active behavior | Wheat mill run pellets cause dusting during handling. In general, up to approx. 10% of the product is powder due to abrasion. There is a risk of dust explosion at a dust/ air ratio of 20 – 2000 g/m3 . |
| Passive behavior | Wheat mill run pellets are sensitive to contamination by dust, dirt, fats and oils. The holds or containers should thus contain no residues of previous cargoes, such as ores, minerals, chemicals, salts, fertilizers. |
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RF Mechanical influences
No risk.
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RF Toxicity / Hazards to health
An increase in CO2 and CO content in the hold air indicates that a cargo fire has begun. Danger: Risk of asphyxiation and poisoning on inhalation. No access is permitted to the hold until it has been adequately ventilated and the atmosphere tested with a gas detector. The CO content may rise from 0.002 – 0.005 vol.% to 1 vol.%. The lethal (fatal) dose is approx. 0.1 vol.%.
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RF Shrinkage/Shortage
Slight losses (trickle losses) may occur during cargo handling.
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RF Insect infestation / Diseases
Insect infestation, especially by various species of beetles (e.g. khapra beetle), is more frequent in pellets based on expeller than those based on extraction meal. Increasing levels of humidity/moisture and heat promote mite infestation.
If required by the consignor or import regulations, fumigation (e.g. with methyl bromide) must be performed.
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