spray dryer experiment

7/24/2019 Spray dryer experiment

1/17

1.0 INTRODUCTION

1.1 Background of Experiment

Spray drying is a very widely applied, technical method used to dry aqueous or organic

solutions, emulsion and others in industrial chemistry and food industry. Dry milk powder,

detergents and dyes are just a few spray dried products currently available. Spray drying can be

used to preserve food or simply as a quick drying method. It also provides the advantage of

weight and volume reduction. It is the transformation of feed from a fluid state into a dried

particulate form by spraying the feed into a hot drying medium.

The spray drying is the most widely used in industrial process for particle formation and

drying. It is well suited for continuous production of dry solids in powder, granulate or

agglomerate form from a liquid feed. asically, spray drying is accomplished by atomi!ing feed

liquid into a drying chamber through a rotating wheel or no!!le, where the small droplets are

subjected to a stream of hot air and converted to powder particles as a result of moisture

evaporation. The resulting rapid evaporation maintains a low droplet temperature so that high

drying air temperatures can be applied without affecting the product.

"s the powder is discharged from the drying chamber, it is passed through a powder#air

separator and collected for packaging. $ost spray dryers are equipped for primary powder

collection at efficiency of about %%.& ' and most can be supplied with secondary collection

equipment if necessary.

1.2 O!ecti"e# of Experiment

To study the process of spray drying which is applied to dry aqueous organic solutions,

emulsion and others.

Experiment 5: Spray Dryer | 4SKKK SECTION 04 1


2/17

1.$ %cope of Experiment

The e(periment was conducted by a group of four people in Separation ) *aboratory,

+niversity Technology $alaysia. "ll the apparatus setup was provided in the laboratory and the

e(periment was carried out on the )th September )-. This e(periment is only as afundamental reference for further laboratory study.



3/17

2.0 T&eor'

2.1 %pra' dr'er

Spray drying is widely used in the industry for conversion of a suspension or solution

into a dry products. In spray drying the suspension or solution feed is atomi!ed and the droplet

formed comes into contact with hot gas. /hen the droplets and the heated gas come into contact,

the solvent in the droplets evaporate, leaving a dry powdered product. This method usually used

in industrial technique used on large scale for drying and powdering very thermally sensitive

materials such as foods and pharmaceuticals. " spray dryer is a device used in the spray dryingmethod. The spray dryer used some type of atomi!er or spray no!!le in order to disperse the

liquid into a controlled drop si!e spray. It takes liquid stream and separates the solute as a solid

and the solvent into a vapor. +sually the solid is collected in a drum or cyclone. The liquid input

stream is sprayed through a no!!le into a hot vapor stream and then vapori!ed. The solids form

moisture quickly leaves the droplets. The function of the no!!le is to make the droplets as small

as possible, ma(imi!ing heat transfer and the rate of water vapori!ation. 0enerally, the range of

droplets si!e is between )- to 1-2m depending on the no!!le. 3urthermore, the spray dryer can

dry the product very quickly compared with other methods of drying. The liquid state turn into

dried powder in a single step, which can be advantageous for profit ma(imi!ation and process

simplification.

In order to reduce the dusts and increase the flow ability of the powders, multiple of

spray dryer effects are used to dry the liquid in one stage. There are two steps in drying process

which are one at the top 4as per single effect5 and an integrated static bed at the bottom of the

chamber. The bottom of the chamber allows the fluidi!ing powder inside a humid atmosphere to

agglomerate to fine the particles with medium particle si!e. Then, the fines generated by the first

stage drying can be recycled in continuous flow either at the top chamber or at the bottom of the

chamber. The drying of the powder can be finali!ed on the e(ternal vibrating fluidi!ed bed. The

hot drying gas can be passed as a co6 current or counter current flow to the atomi!er direction.

The co6 current flow enables the particles to have a lower residence time within the system and



4/17

the particle separator operates more efficiently. +sually, the counter6 current flow method

enables a greater residence time of the particles in the chamber and usually is paired of spray

dryer in food and drug production.

3igure ).7 The spray Dryer

2.2 (pp)ication of #pra' dr'er

I. *ood indu#tr'7 milk powder, coffee, tea, eggs, cereal, spices, flavorings, starch, and

starch derivatives, vitamins, en!ymes, stevia, and colorings.

II. +&armaceutica)7 antibiotics, medical ingredients, additivesIII. Indu#tria)7 paint pigments, ceramic materials, catalyst supports and microalgae.

2.$ *unction of #pra' dr'er



5/17

I. " device used to produce dried foods

II. 8roduce a good quality final product with low water activity and reduce the weight,

resulting in easy storage and transportation.

2., T&e parameter# of #pra' dr'er

I. In)et temperature7 The higher the temperature inlet, the faster is the moisture

evaporation but the powder is subjected to higher temperatures, which may distort the

chemical# physical properties of heat6 sensitive products.II. Out)et temperature7 This governs the si!ing of powder recovery equipment, and the

higher the outlet temperature, the larger will be the si!e of powder recovery equipment

and conveying ducts. The outlet temperature also controls the final moisture content of

the powder.

III. -o)ume of particu)ate poder otained/

VP=VR [(P1P2)]1

/here7

9p: 9olume of particulate powder, cm;

9< : Standard volume, cm;

8: 8ressure after applying pressure on the standard density

8): 8ressure after taking 9cinto account

I-. O"era)) t&erma) efficienc'/

overall=[ TAiTAoTAiT]100Experiment 5: Spray Dryer | 4SKKK SECTION 04 5


6/17

/here7

T"i: The inlet air temperature

T"o: The outlet air temperatureT=: The ambient temperature

2. +rincip)e of #pra' dr'er

There are three fundamental steps involved in spray drying7

i. "tomi!ation of a liquid feed into fine droplets.

ii. $i(ing of these spray droplets with a heated gas stream, allowing the

liquid to evaporate and leave dried solids.

iii. Dried powder is separate from gas steam and collected.

2. Benefit# of #pra' dr'er

i. Typical application in pre6 formulated products

ii. $icroencapsulation, solid solutionsiii. Improved bioavailability, improved product stability

iv. 8roducts with unusual or difficult characteristics

v. Sticky or hygroscopic productsvi. Difficult to isolate products

vii.


7/17

spray6 dried foods often serve as baby foods. Spray drying keeps the retail

price of such foods low, because of the process e(tends the product?s shelf

life.

iii. Indu#tria) product#7 Spray dryers give an advantage in many commercial

and industrial industries. 3or e(ample, in fabrics and clothing, and spray6

dried pigments appear in many wall paints. Spray dryers reduce the si!e of

particles found in dyes to allow more consistent and convenient dispersion

into paints. The dyes are allowed to dissolve in liquids that can then dye

clothes and fabrics.iv. T&e production of mi)k poder u#ing #pra' dr'ing tec&ni3ue7 $ilk

powder production is an e(ample of spray drying. During the process of milk

powder production, after cooling stages, the milk emulsion is concentrated

and after that the concentrated emulsion becomes ready for spray drying. The

concentrated emulsion is atomi!ed into droplets by a centrifuged atomi!er or

high pressure spray no!!le, which located at the top of the spray chamber. The

droplets fall into the spray chamber in a concurrent flow with a hot air, the

moisture in the emulsion droplets is removed by hot air. $ilk droplets shrink

in si!e as water is evaporated from its surface. 3inally, the droplets lost most

of their moisture and become particles with a solid crust formed at their

surfaces

$.0 4et&odo)og'

$.1 5enera) %et6up +rocedure#

. The cyclone chamber on the holder is installed

). The no!!le housing is installed;. The sample 4liquid5 is prepared

. the power supply and the main switch in a panel spray drier is switched on

&. Set the temperature 4inlet5@. The blower and the heater is switched on

A. >utlet temperature increased until --BC

1. The feed pump is switched on



8/17

$.2 5enera) %&ut6don +rocedure#

. The feed pump and the blower). The heater is switched off and temperature outlet is decreased in range ;&6-BC

;. The main switch in a panel spray drier and the power supply

. The sample is taken out while the cyclone chamber and housing no!!le isremoved

,.0 RE%U7T

Ta)e ,.1/ Experiment re#u)t of particu)ate poder8# den#it'

Data Te#t 1 Te#t 2 Te#t $ ("erage

9olume of particles

powder, 9p4cm;5

).)@ @.A& @.A& 1.@&

Density of

particulate powder,

4kg#m;5

&.;) %%.% %%.% 1.A;

Ta)e ,.2/ Experiment re#u)t of in)et and out)et temperature

Operation #tate In)et temperature 9C: Out)et Temperature 9C:

efore e(periment %% --

During e(periment )-- %;

"fter e(periment %% 1%

Experiment 5: Spray Dryer | 4SKKK SECTION 04


9/17

Thermal efficiency 4overall5 : @.'

.0 DI%CU%%ION

*igure .1 +roce## *)o Diagram for Entire %pra' Dr'ing %'#tem

Experiment 5: Spray Dryer | 4SKKK SECTION 04 !


10/17

*igure .2 +roce## B)ock Diagram for Entire %pra' Dr'ing %'#tem

Spray drying process is one of the drying techniques used for production of food

powders. It is the simplest technique used by commercial industry to convert the fluid material

into solid or semi6solid particles where the product is heat sensitive or heat resistant. In spray

drying process, the spray dryer uses hot air to evaporate water from the product. The hot air used

is air or inert gas 4nitrogen gas5. The main driving force is the temperature difference between

the surrounding air and the temperature of particle or known as the wet bulb temperature of the

inlet air.

3rom the figure above, the spray dryer pump a liquid stream into drying chamber andseparate the solute as solid and the solvent into a vapour. Then, the liquid input stream is

sprayed through a no!!le or atomi!er by a hot vapour stream and vapori!ed. The hot air used is

air or inert gas 4nitrogen gas5. "ir is heated by heating element before it enters the chamber.

"fter that, the bulk liquid will be converted into droplets or mist though a no!!le. The function

of no!!le is to make droplets as small as possible to ma(imi!e heat and mass transfer and rate of



11/17

water vapori!ation. In common, no!!le si!e varies from ranges of )-2m to 1-2m. "ccording

to Singh and Di(it 4)-5, the choice of atomi!er depends on the nature and the configuration of

feed a well as desired product characteristic. /hen the hot air and the droplet contact with each

other, it will evaporate the moisture content of droplet and changes it into powder form. The

dried powder product will be separated by using a cyclone where dense particles are recovered at

the drying chamber base. Drying is finished when the particle temperature is equal to the air

temperature. 3or industrial based drying process, the spray dryers are equipped with the filters

4bag filters5 in order to remove the finest powder. Chemical scrubber is used to remove the

remaining powder or volatile pollutants.

3rom the result obtained, the average density of the milk particulate powder is

1.A;kg#m;. Eowever, it is different with the standard density value of milk which is -;&

kg#m;. The large difference is mainly due to the errors occurring during the e(periment. The

solid particles are precipitated at the bottom part of the bottle, and this causes the water cannot

evaporate from the solution effectively. Eowever, the product collected into the small sample cell

for measuring density is not including the wet product, while only dried particulate is taken into

account. Therefore the mass of the particulate is affected. >n the other hand, the input

temperature set may not the most suitable for the separation process to happen. ther than that, the major difficulty in spray drying milk solutions is encountered in attempting

the formation of droplets during the spray drying operation. Instead, filaments are usually

formed. These are caused by premature drying of liquid filaments formed near the spray no!!le

before they can be broken up into droplets.3ormation of these filaments also results in a

considerable loss of milk during drying because of plastering of the walls of the spray dryer and

incomplete drying of the product.

+sing the, the performance of spray drying is calculated which is measured in terms of

thermal efficiency by using temperature measured during the e(periment. If the drying process is

assumed to be adiabatic, that is, the heat loss is negligible, the overall thermal efficiency

4Foverall5 can be appro(imated to the relation7



12/17

',--

=TT

TT

Ai

AoAi

overall

where T"iand T"oare the inlet and outlet air temperatures, respectively and

T

is the ambient

air temperature. The thermal efficiency found in the e(periment is @.'.

There are some modifications that can be made on the e(isting system to increase the

recovery percentage of product. y increasing the inlet temperature, the recovery percentage can

be increased. "t higher inlet air temperatures, there is a greater temperature gradient between the

atomi!ed feed and drying air and it results the greatest driving force for water evaporation. The

use of higher inlet air temperature leads to the production of larger particles and causes the

higher swelling. If temperature is low, the particle remains more shrunk and smaller. Gijdam

4)--@5 were obtained the similar results in the production of milk powder at )-BC and )--BC.

The higher drying temperature is lower the moisture content and increase its hygroscopicity. This

is related to the water concentration gradient between the product and the surrounding air, which

is great for the less moist powder. The increase of inlet temperatures has given the higher process

yield and it was due to the greater efficiency of heat and mass transfer processes occurring when

higher inlet air temperatures were used. /hen the drying temperature is sufficiently high and the

moisture is evaporated very quickly and the skin becomes dry and hard. "s a result, the hollow

particle cannot deflate when vapor condenses within the vacuole as the particle moves into

cooler regions of the dryer. Eowever, when the drying temperature is lower, the skin remains

moist and supple for longer, so that the hollow particle can deflate and shrivel as it cools.

Secondly, the rate of air flow must be at a ma(imum in all cases. The movement of air is

decided the rate and degree of droplet evaporation by inducing, the passage of spray through the

drying !one and the concentration of product in the region of the dryer walls and finally e(tent

the semi6dried droplets and thus re6enter the hot areas around the air disperser. " lower drying air

flow rate causes an increase in the product halting time in drying chamber and enforces the

circulatory effects. The effect of drying air flow rate on powder solubility depends on its effect



13/17

on powder moisture content and density of powder. Density variation can arise from temperature

changes and migrating pollution. y using C>$S>* multi physics we can able to get the e(act

solution which is used for both temperature and concentration changes. The rising of air flow

rate was led to the increased of powder moisture content and decrease in powder solubility

48apadakis, %%15.

*astly, at higher atomi!er speed, the smaller droplets were produced and more moisture

was evaporated resulting from an increased contact surface.

.0 CONC7U%ION

The objective of this e(periment had been achieved as the milk which was fed in liquid

had been evaporated into dry particulates through the spray dryer. The density measured was

1.A; kg#m; and overall thermal efficiency for the spray dryer was @.'. The measured

density of milk is different with the standard value which is -;& kg#m ;. This may due to some

errors occurred during the e(periment. The spray drying system needs to be modified in order to

have better efficiency in recovering products.



14/17

RE*ERENCE%

. 3eli( Hngman, Spray Drying as an "ppropriate Technology for the 3ood and

8harmaceutical Industries, ournal of Hnvironment Science, Computer Science and

Hngineering J Technology,September6 Govember )-), 9ol. , Go. ;, @A6 A@.

). Dr. $ukesh 0ohel, )--%, Spray Dryer7"


15/17

@. H.Don!, 8. oiron, .* Courthaudon, Characteri!ation of industrial dried whey

emulsion at different stages of spray drying, ournal of 3ood Hngineering, )-, )@,

%-6%A.

A. Charles >nwulata, )--&, Spray Drying,

https7##www.princeton.edu#Lachaney#tmve#wiki--k#docs#SprayMdrying.html,

retrieved on )A September )-.

1. Samatha Singh, Deepa Di(it, " review on spray drying7 Hmerging technology in 3ood

Industry, International ournal of "pplied Hngineering and Technology, )-, 9ol.

45, 61.

(++ENDI;

Table "ppendi( /H(perimental result of calculation of particulate density

Data for ca)cu)ation of particu)ate poder8# den#it'

Total weight 4g5 &.-&

/eight of beaker 4g5 .;-

/eight of sample 4g5 -.@A&Standard volume, 9


16/17

Sample calculation

9(:Ca)cu)ation of "o)ume of particu)ate poder< -p9cm$:

Vp=VR[(P1P2)1]

for test1,

Vp=6.28 [( 16.4935.537)1]Vp=12.426

9B: Ca)cu)ation of particu)ate poder8# den#it' 9kg=m$:

density , = mass of particulate powder(g)

volume of particulate powder(cm3)

1000 kg

m3

for test1,

= 0.675 ( g )

12.426(cm3)

1000kg

m3

=54.321 kg /m3

9C:Ca)cu)ation of t&erma) efficienc' 9>o"era)):

overall=

(TAiTAo

TAiT )100

overall=( 2009320025 )100overall=61.14



17/17


spray dryer experiment

Documents