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.