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Belt
drier with integrated CIP cleaning
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Short description:
Every owner of a belt drier, who demands certain minimum
standards with regard to hygiene in his factory, knows the
problems when cleaning his drier. Especially manufacturers
of sticky products like e.g. coated cereals know the lengthy
and arduous job of cleaning the drier tunnel.
From the field of food and dairy products e. g., CIP
cleaning systems have been well-known for a longer time
already, cleaning automatically with a greater number of
stationary spray nozzles, tanks, piping etc. Such systems
are out of the question for a belt drier. The reasons are,
among other things, that numerous mobile parts of a belt
drier have to be cleaned and the size of many drying tunnels
requires a vast number of nozzles and, consequently, of
cleaning solvent.
STELA Laxhuber now has developed a cleaning system with
rotating high-pressure nozzles, installed on a slide
moveable diagonally and longitudinally.
Rotating spray nozzles offer the best possible distribution
of the cleaning solvents in all directions, that is to the
front sides and the labyrinth sheets as well.
Through installation of rotating spray nozzles on an upper
and lower slide, STELA has succeeded in managing with the
lowest possible amount of cleaning solvents for this CIP
cleaning system.
The regular drying process is not disturbed as the cleaning
slide is situated outside the product zone.
The CIP system itself, which produces the cleaning solvent,
can be conceived as a fresh-preparation cleaning because of
the low amount of cleaning solvent required and the
intensive cleaning. A batch cleaning system with several
containers is not necessary.
Detailed description:
The integrated CIP cleaning system is used for cleaning belt
driers for sticky and/or heavily polluting bulk goods or
similar products.
The driers are cleaned via cleaning slides above and below
the drying belts, which are equipped with rotating spray
nozzles. Consequently, the areas above and below the belts
are cleaned. The belt is cleaned in the separate
online-cleaning station of the drier. The upper and lower
slides each are supplied together and operated alternately.
The supply of water and the cleaning solvents is carried out
through 1” tubes with automatical tube take-ups.
The CIP system is installed as a compact unit on a base
frame and consists essentially of a 2,500 l tank, a built-in
recirculation pump, a heat exchanger, a re-rinseable
screening unit and the proportioning equipment for the
cleaning concentrates.
Cold water, hot water, lyes and acids are available as
cleaning media. The cleaning tank is filled with water up to
an adjustable amount according to demand. The water is
cycled via the heat exchanger for heating. For preparation
of acid or alkaline cleaning solvents, concentrate is dosed
until the preselected reference value is achieved.
Pre-rinsing is carried out with cold or hot water, which is
sprayed first over the upper and then over the lower sledges
for one or two passages. The water rinses off easily
detachable incrustations and washes them out of the drier.
The considerably polluted pre-rinsing water is lead into the
gully before the screening unit so that the sieve is not
clogged.
Afterwards, a 1-2% soda lye or an appropriate cleaning agent
is preparated and heated. The main incrustations are cleaned
under the belt in circulation via the lower slide moving
back and forth. For appropriate pollution, this procedure
can also be carried out with the upper slide at first. When
the temperature and the reference value have achieved the
minimum values in return flow from the drier, this cleaning
phase goes on for a preselected time or for a number of
slide passages that have to be determined. Afterwards, the
cleaning solvent is lead into the gully and the plant is
rinsed with water.
Now, the drying plant is equally cleaned with nitric acid,
with usually lower concentration and temperature and shorter
cycles.
The re-rinsing with cold fresh water is carried out via the
upper and the lower slide as long as the reference value in
the return flow does not indicate residual cleaning agents
any more.
A screening unit in the return flow prevents particles from
flowing into the cleaning tank and from there into the
nozzles and from clogging these nozzles. The current through
the sieve can be changed through a bank of valves. When the
surface of the sieve is clogged by the dirt, the
pre-compression rises. The sieve is moved in a circle now
and re-rinsed with a clean solvent directly from the tank.
This automatic re-rinsing is possible at any time during
cleaning.
The use of double-seat valves for the dosing of the
concentrate and the distribution to the driers guarantees,
in case of sealing failures as well, that the last rinsing
water cannot be contaminated with chemicals. Furthermore, it
is ensured that during cleaning moisture can never be
pressed into another operating drier.
The nozzle systems are blown through by means of compressed
air at the end of cleaning so that, after cleaning, water
cannot drip from the nozzles onto the product to be dried.
At the front sides of the drier, the slides are moved to the
wall to less than 700 mm each to drizzle these areas
thoroughly.
Product distribution and drier screens are designed flexibly
to enable the slide to pass.
Optionally, the scarcely polluted re-rinsing water can be
collected and used for pre-rinsing of the next cleaning
process to reduce water consumption for pre-rinsing.
The control is constructed as S7 with OP 37 visualization
and operation. Communication is carried out via a H1-bus.
The cleaning process is determined by the CIP control. The
programme can be started at the switchboard of the drier.
The cycles are synchronized with the slide passages of the
drier through a relevant exchange of signals.
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