The document summarizes steam heated drum drying and cross flow air drying methods. Steam heated drum drying involves heating water in drums connected by tubes to produce steam for drying. Cross flow air drying uses hot air blown perpendicular to material flow through small ducts to reduce drying time for continuous semi-continuous processing. Both methods were evaluated for drying spirulina containing 55-66% moisture, with cross flow drying taking 14 hours at 62 degrees Celsius and being cheaper than drum drying.

1. Submitted to:
Dr. Arockiya Aarthi Rajathi,
Department of Microbiology.
Assistant professor,
Submitted by:
P.Pugazhenthi,
I-Msc, Microbiology.

2. Steam heated drum drying &
Cross flow air drying

3. STEAM HEATED DRUM DRYING
 Initially the boilers were designed with 4 drums or
3 drums like stirting boiler.
 The single drum at bottom and three drums on the
top were connected through a network of tubes.
 The rational demand of stream in terms of
capacity, pressure and temperature.

4. STRUCTURE:

5. FUNCTION:
 Within the boiler, fuel and air are force into the
furnace by the burner.
 There, it burns to produce heat.
 From there, the heat (flue gases) travel
throughout the boiler.
 The water absorbs the heat, and eventually
absorb enough to change into a gaseous state -
steam.
 To the left is the basic theoretical design of a
modern boiler.
 Boiler makers have developed various designs to
squeeze the most energy out of fuel and to
maximized its transfer to the water.

6.  Water enters the boiler, preheated, at the top.
 The hot water naturally circulates through the
tubes down to the lower area where it is hot.
 The water heats up and flows back to the steam
drum where the steam collects.
 Not all the water gets turn to steam, so the process
starts again.
 Water keeps on circulating until it becomes steam.
 Meanwhile, the control system is taking the
temperature of the steam drum, along with
numerous other readings, to determine if it should
keep the burner burning, or shut it down.

7.  As well, sensors control the amount of water entering
the boiler, this water is know as feedwater.
 Feedwater is not your regular drinking water.
 It is treated with chemicals to neutralize various
minerals in the water, which untreated, would cling to
the tubes clogging or worst, rusting them.
 This would make the boiler expensive to operate
because it would not be very efficient.
 On the fire side of the boiler, carbon deposit resulting
from improper combustion or impurities in the fuel can
accumulate on the outer surface of the water tube.
 This creates an insulation which quickly decrease the
energy transfer from the heat to the water.

8.  This device, which looks like a lance, has a tip at the
end which “blows” steam.
 This blowing action of the steam “scrubs” the outside
of the water tubes, cleaning the carbon build up.
 Water tube boilers can have pressures from 7 bar to
as high as 250 bar.
 The steam temperature’s can vary between saturated
steam, 100 degrees Celsius steam with particle of
water, or be as high as 600 - 650 degrees Celsius,
know as superheated steam or dry steam.
 The performance of boiler is generally referred to as
tons of steam produced in one hour.
 In water tube boilers that could be as low as 1.5 t/hr
to as high as 2500 t/hr.

9. CROSS FLOW AIR DRYING
 One of the most popular continuous flow dryers
called cross flow dryers.
 In this type of dryer the air glow is generally
perpendicular to the grain flow.
 The cross flow dryers combine the simple
operation of a batch system with the increased
efficiency of a semi continuous design.
 In this type of dryers, the blower forces hot air
through many small ducts or channel.
 This reduces drying time and allows processing of
all the trays at once.

10.  To prevent the over heating of the trays a cross
flow dryer uses sensors to control the blower
output.
 The wet solids of spirulina containing 55-66%
moisture after the cloth filtration were dried at 62
degree celsious for 14 hrs.
 When sun drying is not possible due to cloudy
or rainy wheather.
 The process is cheaper than drum drying.

11. STRUCTURE

12.  Reference:
 Text book: Biotechnology & utilization of algae the
Indian experience- L.W. Venkata Raman, E.N.Becker.
 https://scholar.google.co.in