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AUTOMATIC PROPORTIONAL DOSING
OF THE ADDITIVES FOR FLOUR
Asis.Prof.D-r. Ivanka Georgievaä, Asis.prof. Vladimir Gebovää
ä - South-Western
University, Bulgaria E-mail: vanyakg@abv.bg
ää South-Western University, Bulgaria E-mail askon@abv.bg
ABSTRACT
Analyzed is the existing situation with the dosing
devises for mixing additives in the Bulgarian mills. Offered is
variant for automatic control of the mixing of the components of flour. The application
of the control system leads to: increase in the preciseness of the proportional
dosing, ignoring the jams on the exit of the dosing devise and the influence
of the subjective factor in decision making and carrying out of regulation
adjustments, systematizing the behavior of the characteristics of the flour
and improvement of the flour quality.
Key words:
îproportional dosing, controls,
automatization, and quality.
The process of preparing
homogenous composition from dispersion materials by mixing them is widely
used in the foodstuff and other industries. The obtaining of mixtures with top quality from dust or granulated
materials in the mixing devises with uninterrupted action is defined by the
effectiveness of the work of the mixing devises, the selecting of optimal parameters of the regimes of
mixing and from the quality of the dosing system incoming components.Òhe solving of the problems with the quality of
dosing begins in the process of design and construction of the mixing complexes,
which constructively combine mechanism for uninterrupted dosing of components
and mechanism for uninterrupted mixing.
The analytic investigation
of dosing devises for mixing of bulk materials [2]
is
orientated towards discovering the relation between the speed of the flow
of materials, the forces acting
in the process of mixing and the constructive parameters of the dosing devises. Made are proposals for finding out optimal constructive
parameters of the mixing devises from point of view the quality of mixing
the different components.
The
investigations on the question about creation and practical implementation
of mixers with automatic control of the quality established that in the literature
there is lack of information.
The aim of the present
work is to solve concrete production problem dictated by the need of the milling
complexes for control of the proportion additive-flour.
The improvement of
the quality of the bread and the other dough articles requires before the
process of packing enrichment with special components called additives.
The destination of
the additives is to whiten the flour and to improve the bread baking properties:
relaxing, production of wet gluten, number of falling, fats, and ash contents.
The mixing of the
flour with the additives must guarantee high homogeneousness and precise percentage
ratio between the components with dependence on the destination of the product.
When not keeping the
percentage ratio overdosing takes place or not sufficient dosing which causes
worsening of the quality of the flour. In the present work the authors offer a variant for solving
the problem by modernization of the existing situation in the 30 leading mills
in Bulgaria. The existing now active principle of mixing is show on fig. 1.
The flow of flour
1 is passed from the previous technological section by transporter or in gravity
way from plansihtery to the opening of the worm mixer 2. Near the worm opening
is mounted dosing device for additives 3.
The dosing devices
for additives to flour by now are divided in two basic construction groups:
with proportional and uninterrupted dosing. The capacity of the dosed product varies between 3-20
g/min in the proportional dosing devices and 50-500 g/min in uninterrupted
dosing devises. At the end of the
worm mixer the flour enters the buffer cells with enough volume ensuring non-stop
work of the mill.
The control of the quality of the mixing and all left
components is carried at the end of the cells and before packing the product.
The transport delay from the moment of putting the additive till the moment
of taking the samples varies from 3 to 12 hours. This transport delay defines
the shortcomings of the system. The investigations in the mills on the capacity
of the grains and milled products are presented on fig. They show great fluctuation
of the same within 48 hours.
The change of the
capacity of the flour causes drive of the proportions in mixing with the additive. As seen from fig.2 the dispersion
of the capacity reaches 20%, which at this stage is considered normal for
the Bulgarian mills.
The upper shortcomings
regarding the quality of dosing, without keeping in mind the capacity of the
product can be overcome with the proportional dosing. The authors propose variant for solving the problem
by building a system for automatic control of the dosing device for additives
– fig.3.
The system is built
with the following modules:
Ø
Electronic scale 1. It is portion and running type with high accuracy
in measurement in the conditions of vibrations of the working environment
and fluctuation of the flow. Such scales are produced by company Buhler and
by the Bulgarian company Askon. The electronic scale [1]
is
a part of the system for automatic proportional dosing by measuring the capacity
of the flour. ;
Ø
Separator 4. Its destination is to divide the electronic scale
from the worm mixer. It breaks into small portions the capacity of the flour
coming from the electronic scale to the mixer.
Ø
Worm mixer 5. It is designated for transportation and mixing
of the flour and the additive.
The single parameter
diffusion model of the mixer with uninterrupted action is presented by the
equation 1 [2]:
(1)
Where: Ñ0- initial proportional condition, t- time of mixing, l-length of the mixer.
The mixing devices with uninterrupted
action have smoothing functions on the input flows. Graphic relation on fig. 4, obtained after investigation
of mixers with different length, proves that exponential relation carries
out the smoothing.
Ø
Dosing device for
additives 8. It is driven by three
phase motor 6, n=1400 min-1. By gear is driven the shaft of the feeding device-
plate or screw. The additive is poured
freely from packets in the bunker of the dosing device. The valve opening
of the plate under the dosing device plays important role regarding the quality
of dosing. The correlation function can be presented by equation 2 but the
fixed in real conditions graphic relation is shown on fig. 5.
(2)
Ø
Inverter is driving
the motor of the dozer. Can be used inverters
produced by different companies, but they must have the following parameters: wide range of change of frequency from 10 to
100 Hz, realization of the ratio
, increase of the tension at low speed of rotation, power of the driven motors from 80
to 150W. In building the automatic system on fog.3 is used the specialized scheme Motorola MC MP3 HAC produced in 2002 for control directly of AGBTs. This leads to elimination of the errors of the
subjective factor, increase of the reliability, decrease of the price and
dimensions. The control of the
frequency of the inverter is carried out proportionally to the capacity of
the flour from the electronic scale according to the equation 3.
(3)
Where: s-liding of the rotor compared to the stator of the motor,
K- coefficient of proportion, Q- capacity of the
flour, measured by the electronic scale,
t2-t1- period of time, for which the electronic scale is measuring uniformly.
Ø
Interface 4. It is with protocol, ensuring monitoring and control of all processes, which are controlled by the electronic scale.
Ø
Laboratory. Realized is uninterrupted monitoring and control
of the technological parameters of the grain and the milled products. In the different mill plants the possibilities
are different. There are measured the technological properties
of the flour at the outlet of the system before packaging and at the inlet
as well.
As a result from the
laboratory measurements is formed the technological decision by the supervisor
of the mill. By the PC he makes
new control task for proportional dosing, based on iteration principle.
The principle of work
of the automatic system is based on dosing of the additive according to the
changeable capacity of the flower.
As a result from the
implementation are achieved:
Ø
High preciseness of
proportional dosing, as a sequence from
the measument of the capacity of the flour in real time and proportional dosing
of the additive;
¨
Avoided are jams at
the outlet of the dosing device because of the fact that it is maximum open;
¨
Ignored is the influence
of the subjective factor in decision making and adjustments;
¨
Systematized the behavior
of the characteristics of the flour in a definite time interval for every
packet production;
¨
Improved is the quality of the product.
CONCLUSIONS:
1.
Created is automatic system for proportional dosing of additives in changeable
flow of flour.
2.
The system is built on the basis of the newest inventions in the field
of tensometric measurements, control of frequency of asynchronic motors and
computer control of the process.
3.
The system allows quick and effective modernization of the existing technological
lines in the mill production, leading to great economic effect and increase
of compatibility of the mill plant in the conditions of market economy.
REFERENCES:
1.
Korzun V., Investigation of the
smoothing abilities of the mixing complex for bulk materials. , Èçâåñòèÿ ÂÓÇ Òåõíîëîãèÿ ëåãêîé ïðîìûøëåíîñòè1
Ìîñêâà, 1991ã.
2.
Ivanez I., Analysis of the dosing
devices of the mixing aggregate on the basis of correlation functions, Èçâåñòèÿ ÂÓÇ Ïèùåâàÿ òåõíîëîãèÿ, Ìîñêâà, 2001ã.