Different ways to a finished beverage
Blending and dosing technology for soft drinks
In the beverage industry, a distinction is made between two manufacturing methods: dosing and blending. This article provides an overview of the current state of technology and of how the different techniques are used.
For decades now, the most familiar method of manufacturing carbonated or non-carbonated beverages has been to use dosing technology. Dosing means that a certain quantity of a substance is added to or removed from a production or measuring process, the amount and the timing or sequence having been pre-determined.
For the beverage industry, this means that a conveying mechanism with metering technology and quantity pre-selection is used to introduce a particular volume of each substance into a target tank. For the most part, pumps are used to convey the required quantities of liquid.
Centrifugal pump
A centrifugal pump is a fluid flow machine which contributes additional energy by means of a rotating impeller. The pump serves to convey liquids through piping. Liquids that enter the pump housing are entrained by the rotating impeller, and initially forced into a circular path within the pump housing. On this path, the pressure built up by centrifugal force presses the water radially outwards into the network of piping connected to the pump. Standard centrifugal pumps are non-self-priming, so that the pump and the suction port must always be filled with medium.
If air gets into the suction port during operation, conveyance of the medium will generally be interrupted. There are special designs such as the jet pump or the vane-type scavenge pump which are able to vent the suction port automatically when liquid is introduced into them. One special form of centrifugal pump is the side-channel pump, a self-priming centrifugal pump, which however is categorised as a displacement pump.
Rotary piston pump
Rotary piston pumps are forced conveyance pumps that are able to build up a very high pressure. This pressure may rise to such an extent that downstream shut-off valves or even the rotary piston pump itself may be destroyed. For this reason, pumps of this type may never be operated against a closed system. In practice, the pump will be equipped with a bypass. This bypass contains a spring-loaded valve which opens the bypass when a predetermined pressure is reached. The medium then passes through the circuit bypassing the rotary piston pump. Inside the pump, two convex rotary pistons operate without contact in cylindrical chambers free of dead space. With this type of pump the shear force exerted on the medium is very low; as a result, even viscous media carrying solid components are conveyed in a gentle manner. One very advantageous feature is that the rotary piston pump can convey media free of pulsation, with the aid of frequency regulation.
Volumetric metering technology
To determine the volume of an ingredient to be dosed into a product, electromagnetic flow meters or mass flow meters are predominantly used. Electromagnetic induction metering is based on Faraday’s law of induction. When a conductive substance (in this case a liquid) moves through a magnetic field, an electric potential is created. The voltage is proportional to the speed of flow and to a very large extent independent of the physical properties of the medium, such as its density, viscosity, consistency, pressure and temperature.
Precise metering is therefore dependent on the liquid to be metered having a sufficient minimum conductivity. As long as the electrical conductivity is greater than 10 µS, no problems are likely to arise in metering.
Mass metering – weighing liquids as they flow
In recent years, mass flow metering to determine the mass in kilograms has been gaining in importance. Thanks to the direct determination of the mass and density of the liquid as it flows, balances or conversion formulae have largely been rendered superfluous. The mass flow meter consists of a pipe in the form of a bend, a semicircle or a complete circle.
Depending on the type of medium (gas or liquid), the mass or the speed of flow, these pipes may be large or small. Other shapes than those described above are also possible. These can be used to achieve a degree of precision that is acceptable in legal metrology. The measuring device is very well suited to multiphase flow. Gas bubbles in liquids, for example, do not cause any significant metering errors. The pressure loss is very small, since only curved elements are
involved. There is no opening in the pipe, so that it is eminently suitable for the food industry. The metering principle is that of the Coriolis force, named after the French physicist Gaspard Gustave de Coriolis.
Mobile dosing device with mass flow meter and quantity pre-selection
Batch operation
Batch operation means that the beverage is manufactured not continuously, but in successive lots or batches. Working in batch operation involves bringing different ingredients together in accordance with individual recipes. The batch device in the beverage industry is a flexible system for producing successive batches in one or more mixing tanks, using a variable number of basic ingredients/essences.
Where there are appropriate pump systems to convey the liquid, mobile or stationary batch mixers can be installed to automate the production. Generally, such systems consist of metering and dosing equipment mounted on a base frame.
Mobile batch mixer
The basic structure is such as to allow the apparatus, which incorporates a number of inlet valves, a deaeration device, a pump, a metering device and a two-stage valve, to be used as a simple batch mixing unit. The concentrate or ingredient lines are connected to the disc valves. One disc valve is connected to the product water pipe. The entire system, all the way to the mixing tank, is filled with water via the water valve. The concentrate/product valves are opened and closed in succession in accordance with the recipe. The dosing procedure finishes with product water. The product water flushes the ingredients through the piping to the mixing vessel; in this way, the product water rinses out and cleans the piping and restores the equipment to its initial status (everything filled with product water).
In connection with this type of equipment in particular, it should be mentioned that any measuring inaccuracy in the metering device is applied equally to all the metered media within the batch. As a result, mixing errors are largely excluded. This system is particularly suitable for filling operations with small starter batches.
The mobile batch mixer for mixing liquid products is an economical solution for the automation and modernisation of the starter area.
The device is distinguished by the following features:
- consistently high product quality,
- optimum use of raw materials without overdosing,
- a high degree of accuracy and reproducibility,
- security against operating errors,
- relief of staff in the starter area.
DI-Batch stationary batch mixer
The batch mixing device of type DI-Batch for the mixing of multi-ingredient products in liquid or powder form is a well-tried and economical solution for automating and modernising the production area. The device is positioned between the ingredient storage area on the one side and the mixing tanks on the other. Thanks to its compactness, the device can easily be integrated into an existing system. Essentially, the device provides for the automatic dosing of the individual concentrates and ingredients. A dissolving vessel with recipe-controlled dosing of water allows dry ingredients to be dissolved with precision.
Through a lance system, recipe-controlled quantities of rinsing water can be used to extract residual quantities from ingredient drums or small containers and convey them to the mixing tank. If desired, the mixing system can also incorporate a bottle-emptying device as a so-called rework station.
Mobile batch mixer device with rotary piston meter
The inline blending process
The aim of a blending procedure is to create a mixture, any sample of which displays precisely (or within a defined degree of tolerance) the proportions of the initial input ingredients. Blends may be created out of one or more components with the same or different physical or chemical properties. For the beverage industry, it is essential that the mixture should be homogeneous.
Where there is a requirement for large quantities of finished beverage to be available immediately, continuous blending equipment is used. GEA Diessel's DICON continuous blending system mixes liquid components continuously in line in constant proportions. The combination of highly accurate metering devices (electromagnetic counters or mass flow meters), digital controls and high-quality regulating valves enables two or more components to be blended in exact proportions.
External pumps supply the system with water, sugar solution and syrup base. It is very important that a suitable pump should be selected, as described above. All volume flows are continuously recorded by the flow meter, which transmits the counting pulses to the plant control system.
This control system compares the metered values with the target proportions, and controls the regulating valves in such a way as to comply precisely with the recipe.
The varying flow characteristics of the different components cause them to mix in the pipe. Static or dynamic mixers take account of the varying viscosities in order to effect the homogeneous blending of the beverage. If the beverage is carbonated, an additional thorough blending is effected using a booster pump. In this case it may be possible to do without an upstream mixer, as long as the various components permit.
Summary
In this article, two highly accurate procedures for the manufacture of a beverage are presented. An assessment as to which procedure is more suitable in a particular case must take account of general conditions at the facility and the volume of beverage to be produced. Basically, inline blending makes sense if the manufacture of large quantities with few product changes is envisaged. If the building is such that it is not possible to extend it (e.g. to provide a new syrup room with a mixing tank), this would be a good argument in favour of the inline blending procedure.
The dosing procedure with a batch mixer is particularly suitable for operations producing small volumes. It is easy to change the product at short notice, since the system is filled with water at the beginning and end of the process. The mixing tanks that are required permit subsequent correction of the dosed beverage if consistently high product quality is a particularly important factor.
The author:
Wolfgang Zenker, studied at Hildesheim College of Electrical Engineering from 1983 to 1985 to become a state-examined electrician. Worked in the field of communications technology from 1985 to 1986. Since 1987 Key Account Manager "Soft drink and spirituous liquor industries" at GEA Diessel GmbH.