- Drying, together with cutting, is one of
the most difficult things in plastic recycling and therefore
one of the most expensive step of the process.
- For all kinds of scrap flakes, we do suggest centrifugal
dryers because of smooth operation, high efficiency
and production rate, maintenance and low energy consumption.
- Till today, even with the thinnest thickness of
film, we got moisture level down to the point a good
extruder can get handle it directly without the needing
of any other energy source.
- And this means saving a lot.
- Give us a call and we'll show it to you in practice.
- If we make too long
you will not reading it but, if you pay some attention
to this, you may save a lots of time and money.
everybody already running a washing line knows
what we are talking about.
like washing, is very related to the thickness of flakes
so, if you're running a washing line for ground crates
or battery cases, drying is not big deal because thickness
is in the range of some millimeters that, for us, is
a huge thickness.
down to microns, the matter is completely different.
are four of five common drying systems available
on the market:
Centrifugal dryers (spin dryers)
Hot air systems
Rotating screens with hot air crossing
some more not very common
Microwave continuous owens
Infrared lights continuous owens
these, first drying step is anyway the removal of most
of water when flakes come out from a sink float tank
or any other dewatering system of any line, meaning
when material has 50% or more water content.
the only two ways we know of, and they are spin
dryers and squeezing presses.
choice went to spin dryers for the following reasons:
A squeezing press has an enormous torque on main shaft
therefore to build it mechanically right one makes it very
The hydraulically operating counter-pressure doesn't
react in real time and this gives quite many problems.
Too long to list.
While water goes out, dirt, if any left, stays together
Sometimes presses melt some or all material so it needs
to work together with a granulator or an agglomerator.
Most of the time capacity is limited or to say it better,
if throughput is high, drying effect is low.
Very high maintenance.
It works only with soft materials so the range of application
our choice went to spin dryers only, not because we
say it's easy; it is just easier and more effective.
spin dryer behave differently according to the following
of the rotor.
of the holes of the screen basket.
of holes per square unit.
time of material.
rate doesn't effect much the drying curve.
is a diagram of one of our standard spin dryer:
we said before, performance can vary a little bit according
to some parameters but this gives you a fair idea of
what we are talking about.
example, changing the holes size to a bigger dimension,
certainly means increase the drying effect but also to
the amount of fines coming out from the screen itself,
so it is always matter to find the right compromise.
important matter is the cleanness of the screen basket;
if holes become jammed by material, the drying effect
decreases a lot, therefore continuous cleaning is strongly
we said before, residence time, that means how long
flakes stay into the basket or, in other words how many
times flakes hit the screen, has a lot of importance.
believe it or not, there are way ways to control the