The MSD™ (Multi-Stage Dryer)/ FSD™ (Fluidized Spray Dryer)

Nah kalau pengen tahu tentang, spray dryer. Mesin yang digunakan pada industri-industri food dairy. Salah satu teknologi yang digunakan untuk menggubah susu cair menjadi bubuk, menggunakan sistem ini. Silahkan baca-baca untuk lebih jelasnya. Semoga bermanfaat.

A
MSD™ (Multi-Stage Dryer)/ FSD™ (Fluidized Spray Dryer) is a dryer that
combines spray drying and fluid bed drying technologies. Through the
process it produces coarse, agglomerated, free-flowing dustless powder.
This drying principle was first introduced in the early 70'es by using
the VIBRO-FLUIDIZER™ for the final drying.

A new dryer concept
GEA
Niro has always focused on developing dryers with improved energy
efficiency and final product quality, and in order to improve the dryer
efficiency even further, without deposit problems in the chamber, a
completely new spray dryer concept - named MSD™ (Multi-Stage Dryer) -
was developed around 1980. Since then GEA Niro has delivered more than
300 plants with the MSD™/FSD™ concept.











Drying in more stages

The first necessary step to reach the concept of the MSD™ was spray drying
in two stages. The MSD™/FSD™ operates with three drying stages, each
adapted to the moisture content prevailing during the drying process.
In the preliminary drying stage the concentrate is atomized by
co-current nozzles placed in the hot drying air duct.

The
air enters the dryer vertically through the air disperser at high
velocity, ensuring optimal mixing of the atomized droplets with the
drying air. The evaporation at this stage takes place instan-taneously
during the passage vertically down through the specially designed
drying chamber. In this primary drying stage the particles reach a
moisture content of 6-15 %, all depending upon the type of product.

Second-stage drying
At
such high moisture content the powder will exhibit high thermo
plasticity and becomes very sticky. But the design and air flow pattern
in the MSD™ plant is created in a way, that prevents the particles from
sticking to the drying chamber, but be led directly into the integrated
static fluid bed for the second-stage drying.

The integrated
static fluid bed is supplied with air at a sufficient velocity and
temperature for the second stage drying. The drying air from the
preliminary drying stage and the subsequent second-stage drying leaves
the chamber from the top.

VIBRO-FLUIDIZER- final drying and cooling
When the powder has reached a certain moisture content, it is discharged via a rotary valve into a VIBRO-FLUIDIZER™
for the final drying and subsequent cooling. The drying/cooling air
from the chamber and VIBRO-FLUIDIZER™is passed through a cyclone,
separating the powder contained in the air. The fine powder is returned
back to the atomization device, the chamber cone (static bed), or the
VIBRO-FLUIDIZER™ depending on the requirements to the final powder bulk
density. On today's modern dryers the cyclone(s) are replaced by a CIP-able bag filter.

Powder structure
The
high velocity air inlet for the primary drying is creating a venturi
effect, the vacuum of which will suck surrounding air - with entrained
fines particles - into the wet atomizer cloud. This will result in a
"spontaneous agglomeration"

The powder will therefore exhibit
a coarse powder structure o riginating from this agglomeration in the
atomizer cloud. Further there is a continuous supply of dry fines
particles from the cyclones/bagfilter that will stick to the semi-dry
particles enhanching the agglomeration. For non-agglomerated powders
all fines from the cyclone/bag filter are returned to the VIBRO-FLUI DIZER™.

It
has been possible to operate this plant at a very high primary drying
air temperature (220-275 C) and an extremely short residence time,
still maintaining a good solubility of the powder. The physical
dimensions of this type of plant are small, and thus the requirements
to the size of the building are limited.

This together with
the improved drying economy (10-15 % less compared to conventional
two-stage drying), due to the high primary drying air temperature,
makes it a very attractive solution, and is today the preferred dryer
for top quality products like cold-water instant whole milk powder and infant milk formulas/baby foods. To improve the drying economy further a heat recovery system can be installed.

Source: www.niro.com

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