Safety:
Three key ‘ingredients’ are necessary
for hazardous conditions to be present in any drying
system, they are:
- Oxygen - Minimum threshold conditions
for Oxygen concentrations for biosolids to ignite
have been documented to be as low as 5%.
- Temperature – Minimum
threshold temperatures for biosolids to spontaneously
ignite have been document to be as low as 115C
(239F)
- Fuel (dust)
They key to any successful drying
operation is the successful and reliable management
of these ingredients under all possible operating
conditions such as start-up, shut-down, normal
operation, and even upset conditions.
Schwing Bioset’s fluid bed
dryer operates under inert conditions as the Oxygen
concentrations are held to less than 3% (typically <1%)
and operates at a temperature of 85C (185F). Any
dust that is generated is instantly removed from
the fluid bed and captured as it passes through
a cyclone.
Automation:
This mode of operation allows for the system to
be completely automated and even operate unattended. The
dryer is controlled by maintaining a constant
energy balance over the dryer by monitoring the
gas temperature as it exits the dryer. The
first level of control, as the gas temperature
increases or decreases, is to vary the speed
at which wet cake is pumped into the dryer with
the Schwing Bioset piston pump. The second
layer of control is to then change the heat input
from the indirect heating source. This
simplistic method of control requires minimal
Operator attention and allows the fluid bed dryer
to accommodate fluctuations in the dry solids
content of the incoming wet cake.
Reliability:
As there are very few moving parts within the entire
system, and the equipment used is of the highest
Schwing Bioset quality, equipment availability
of over 90% in any given year is possible.
Thermal Efficiency:
Utilizing heat exchange tubes submerged within
the fluidized layer, the fluid bed achieves extremely
high thermal efficiencies. The self cleansing
action of the fluidized bed prevents the heat
exchangers from becoming fouled and losing efficiency.
Additional Features:
- Wet cake is fed directly into
the fluid bed without the need for pre-conditioning
the wet cake or recycling any dried biosolids.
- Low off gas requirements - equal
to volume of gas that is entrained in the wet
cake.
- Drying, cooling, and dry granulate
storage all operate under inert conditions as
off gas is used in each process before treatment.
- Final product is virtually dust
free
- 90% of dried pellets are 1-4
mm in size. No additional milling, screening,
or classifying is necessary.
- Dryer can start-up and shut-down
in approximately 30 minutes.
System Supply:
Schwing Bioset is the only manufacturer who can
offer the wet cake storage, pumps, dryers and
dry granulate storage from a single manufacturer. As
the upstream and downstream components are equally
important to any successful drying installation,
the proper integration of high performance equipment
is a must. By selecting a drying system
from Schwing Bioset, the Customer is assured
all components will be seamlessly integrated. |
