It is important to have the correct equipment and working conditions in place to ensure the accurate and efficient incorporation of molasses liquids during the manufacturing process.
Molasses is a liquid that can be added with a high level of precision during the production process.
The molasses fill pipe for the storage tank should be 100mm in diameter and enter at the top of the tank. The vehicle inlet connection should be 100mm BSP male screwed end and be securely fixed at 750mm above ground level. It is good practice to have a duplex filter fitted at the intake point, followed by a valve. Baskets for the filter should have 2mm holes and the maximum number of perforations to allow optimal flow. Providing the intake line is 100mm in diameter, the delivery vehicles can pump molasses through 50 metres of horizontal pipe or 14 metres of vertical pipe. United Molasses delivery vehicles normally carry 13 metres of delivery hose, but can carry an additional 14 metres for difficult site conditions. Discharge pipe lines should be as short as possible to facilitate rapid and easy delivery.
Steel is the most common material for molasses pipework, it is not recommended to use galvanised pipework. When designing pipework for molasses the directional changes on suction should be minimised, however direction changes have no significant impact on the efficiency of pump delivery. The valves used on molasses lines should be of the unrestricted flow type, such as gate valves, plug valves or ball valves.
Given the viscosity of molasses, a positive displacement pump must be used. Centrifugal pumps are primarily designed for liquids with turbulent flow characteristics and should not be used. The main types of positive displacement pumps used in the feed compound industry are rotary gear, lobe, worm and stator, sliding vane and peristaltic. There are two broad categories in most mills, transfer pumps and variable speed metering pumps. The key requirements when specifying a pump unit are: quantity of molasses, viscosity at lowest pumping temperature and delivery pressure. Pumps should be provided with a pressure relief valve either as an integral part or installed in a loop between delivery and suction.
To minimise the effect of temperature, the molasses storage tank should be situated inside the mill building or, if that is not possible, in a very sheltered position outside. It should be accessible and have a level approach capable of supporting a gross vehicle weight of 45 tonnes. The size of tank or tanks required depends on a number of factors, but storage capacity should be sufficient for four days maximum potential usage in the busiest production period. Since most mills order the maximum delivery size of 29 tonnes, the minimum tank size should not be less than capable of holding 35 tonnes. A new vertical tank should be suitable for a liquid having a specific gravity of upto 1.45 and have a minimum plate thickness of 5mm. The recommended tank material for molasses is mild steel and new or second hand tanks should conform to BS 2654 specification. A rectangular tank can also be used if necessary but will need to be custom designed to handle molasses. Cylindrical tanks are most commonly used and the most effective are the cylindrical type fitted with a skirt. The skirt provides protection for the most critical pipework in cold weather. The top and bottom of the tank should be dished and the outlet should be from the centre bottom through a 100mm cast steel valve. This type of tank inhibits the build-up of sludge/sediment and is much easier to keep clean than a flat bottom tank. Standard molasses products will not corrode mild steel, but those internal metal surfaces that are not in contact with molasses – such as the tank top and any uncovered tank sides – may rust because of condensation caused by differences in temperatures between the inside and outside of the tank. To avoid the corrosion caused by condensation, it is important to ensure an adequate air flow by installing vents in the top of the tank. This venting is essential to facilitate the displacement of air during the delivery of molasses. A fully bunded containment area should be provided around the tank(s) to prevent contamination of molasses into water drainage systems in the event of a spillage at loading or a subsequent leak from the tank.
TANK MAINTENANCE, HEATING AND STOCK CONTROL
Manholes should be fitted to main storage tanks together with access ladders and vents to allow for repairs, routine inspection and cleaning. There should also be a facility for draining the tank through a tee section in the pipe between the bottom valve and transfer pump. Heating molasses in the main storage tank is not normally recommended it is more common if heating is required to install a smaller day tank on site, but it is sound practice to provide a 50mm heating coil in all new tanks. The coil can then be used to reduce very high molasses viscosities caused by very cold weather. The coil heating medium should be water, with a maximum temperature of 60°C. In addition, it is critical that the pipework from the main tank to the pump is insulated. Every tank should have an easily accessible and effective contents gauge to allow daily stock control and to ensure that the delivery driver can monitor intake and avoid accidental over-filling. For advice on what gauges are available please don’t hesitate to give United Molasses a call.
Through the selection of the appropriate mixing and inclusion method, greater levels of molasses can be more accurately incorporated into compound feed, at the same time aiding the production process. Pellet quality is much higher, even where low levels of molasses are included. Molasses has proved very effective as an aid to reducing inherent dust in meals and improving the flow from storage bins.
ACHIEVING GOOD MOLASSES INCLUSIONS
To achieve good molasses inclusion levels with standard milling equipment it is essential to be aware of two basic rules: 1. Use a good mechanical mixer to blend the molasses and meal together to ensure that every particle of meal is coated. 2. The higher the viscosity of the molasses, the thicker the coating will be and the more time is required for absorption. When looking at the absorption process the following key factors should be considered:
MIXING With many conventional milling systems it is possible to add molasses to the meal in two or three stages during the production process. Up to 2% molasses can be added to the meal at the main mixer, achieved through injecting molasses at a controlled rate into the lower half of the horizontal mixer (unlike fat and other liquids which are added from the top). This allows maximum absorption time. An in-line high speed molasses mixer can be installed after the main mixer. They are extremely effective if correctly positioned and used within the limitations of the subsequent conveying and storage systems.
While the density of molasses is reasonably stable at all times, the meals into which it is mixed vary considerably due to the variety of raw materials used in feed manufacture today. This is most apparent in mills where ruminant feeds are made. These feeds can contain materials as varied as Beet Pulp, Wheatfeed, Bran, Oatfeed and sunflower husks. The precise addition of molasses must be given special attention where large variations in feed densities do occur. If these variations are not accounted for there could be serious problems with molasses usage and pellet quality. Various methods using fully automatic controls linking a continuous weighing system are available to solve such difficulties.
The addition of molasses to specialised coarse type mixes for cattle, sheep and horses is completely different from the principle applied to meals. Most of the raw materials used are in pelleted, flaked, bruised or caked form and specialised mixing is necessary to preserve the state of the raw materials. This calls for mixers which have a gentle action. The addition of molasses to coarse mixes, aside from nutritional value, also makes feed more palatable, dust free and acceptable to stock. In coarse mixtures it is desirable for a major part of the molasses to remain on the ingredient surface after mixing, unlike meals where molasses has to be absorbed. To assist in the coating process United Molasses makes a special range of molasses blends containing vegetable oils under the trade names of Molashine and Molablend.
Under normal conditions of storage and usage, molasses is quite inoffensive and is neither toxic nor inflammable. It is harmless to the skin and easily washed off with water. Water can be added to molasses, but because the specific gravities of both liquids are very different, mixing the two is a not a straightforward process and requires the ability to thoroughly homogenise. Dilution above 30% moisture is very likely to lead to fermentation, especially if this is accompanied by an increase in temperature. Molasses is relatively stable up to temperatures of 40°C, however further raising of the temperature to levels above 60°C will almost certainly cause thermal decomposition with the molasses sugar content being progressively destroyed.