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Jet ouster efficiency has been defined by research workers in different ways, like mark efficiency, aggregation efficiency, overall efficiency and fractional efficiency ( Mohebbi et al. , 2003 ; Pulley 1997 ; Yung et al. , 1977 ; Leith et al. , 1985 ; Boll 1973 ; Calvert 1970 ) . The overall aggregation efficiency is defined as

For particulate affair

( 2.14 )

For gaseous pollutant: Taheri et Al. ( 2008 ) defined aggregation efficiency ( the extentof soaking up ) as

where are the initial, concluding, and equilibrium partial force per unit area of gaseous pollutant in millimeter of, severally

Collection efficiency have been reported with regard to gas/liquid ratio, gas and liquid flow rates, geometry of venturi scrubber like projection ratio length of pharynx, angle and length of convergent diffusor subdivision and belongings of particulate/gas pollutants. Research workers have reported different empirical correlativities to foretell efficiency on the footing of different premises they have considered. The huge literature has been published on the topic. Table 2.6 is the summery of some of the earlier research. Typical graphical presentations are shown in Figure 2.15, 2.16, 2.17 and 2.18. Tocopherol: images4.5.jpg

Figure 2.15: Dependence of the overall aggregation efficiency of liquid gas ratio

( Vishwanath et al. , 1997 ) .

Tocopherol: 17.8.jpg

Figure 2.16: The consequence of pharynx gas speed on the aggregation efficiency in venturi scrubber ( GA-ANN no. 1 ) . ( Taheri et al. , 2008 )

Tocopherol: images4.7.jpgFigure 2.17: Consequence of fluctuation in venturi figure and aspect ratio on aggregation efficiency for a changeless Venturi figure.

( Ananthanarayanan and Vishwanathan, 1998 )

Tocopherol: imagesafter 4.2 jet ejector.jpgE: imagesafter 4.2 jet ouster 1.jpg

( A ) ( B )

Figure 2.18: Efficiency as a map of ( A ) atom diameter ( B ) liquid to gas ratio with liquid surface tenseness as a variable. ( Ott el al. , 1987 )

Ott et Al. ( 1987 ) developed a theoretical account analyzing the consequence of surface tenseness on public presentation of venturi scrubber. They examined the consequence of liquid surface tenseness on droplet size and on atom incursion into the droplet. ( Figure 2.18A and B )

Economopoulou and Harrison ( 2007 ) developed graphical tools for gauging the overall aggregation efficiency of Venturi scrubbers under the specified design and operating conditions based on the well-established theoretical preparations of Calvert ( 1970 ) and Yung et Al. ( 1978 ) .

Taheri et Al. ( 2010 ) simulated gas soaking up in a venturi scrubber and developed a

3-dimensional mathematical theoretical account, based on a non unvarying droplet concentration distribution. They validated their theoretical account with the experimental informations reported by Johnstone et Al. ( 1954 ) and Wen and Fan, ( 1975 ) for remotion by utilizing alkalic solution and. They used Lagrangian attack for H2O droplet motion. Yung et Al. ( 1978 ) and Crowder et Al. ( 1981 ) have developed mathematical theoretical accounts to analyze different parametric quantities of high energy Venturi scrubbers.

2.3.2 Jet ousters

The application of jet ouster as vacuity bring forthing device and as jet pump is good known

( Gamisans et al. , 2004 ; Govatos, 1981 ; Cunningham, 1974 ; Cunningham and Dopkin, 1974 ; Bonnington, 1956, 1960, 1964 ; Bonnington and King, 1972 ; Blenke et al. , 1963 ; Kroll, 1947 ) . With the fast growing of chemical procedure industry, their usage as entraining and pumping device to manage caustic fluids, slurries, exhausts and dust laden gasses has increased. Their usage as mass transportation equipment for liquid-liquid extraction, gas soaking up, gas denudation, slurry reaction like hydrogenation, oxidization, chlorination, agitation, etc. has increased. Due to increasing involvement in the use of jet ousters, figure of research workers have attempted to optimise their public presentation. ( Das and Biswas, 2006 ; Gamisans et al. , 2004 ; Gamisans et al. , 2002 ; Dasappa et al. , 1993 ; Mukharjee et al. , 1988,1981 ; Radhakrishnan and Mitra, 1984 ; Pal et al. , 1980, 1975 ; Biswas et al. , 1977, 1975 ; Acharjee et al. , 1975 ; A Singh et al. , 1974 ; Bhat et al. , 1972 ; Davis et al. , 1967 ; Mitra and Roy,1964 ; Mitra et al. , 1963 ) .

Working of jet ouster

A jet ouster is a device in which suction, blending and scattering of secondary fluid is done by using the kinetic energy of a motivation ( primary ) fluid. Das and Biswas ( 2006 ) stated that when jet ousters are used as a device for reaching gas-liquid, the secondary fluid may be dispersed by the shearing action of the high speed motive fluid or the motivation fluid itself may acquire dispersed when it is arrested by a secondary fluid. Figure 1.1 shows the typical ouster system in which the jet of primary fluid publishing out of a nozzle creates a low force per unit area part around it. The force per unit area derived function between the entry point of the secondary fluid and the nozzle tip provides the driving force for entrainment of the secondary fluid. Two chief flow governments in ousters are coaxial-flow and froth-flow. The coaxial-flow constitutes a cardinal nucleus of primary fluid with secondary fluid fluxing in the annulate part formed between the jet of primary liquid and ouster. Froth-flow government is a co-current flow of fluids with one stage wholly dispersed in the other. Witte ( 1969 ) termed the phenomenon of alteration from coaxial-flow to froth-flow as blending daze. Here a portion of the kinetic energy of the flow is dissipated in the daze making the gas-liquid scattering. The blending daze consequences into coevals of little bubbles and accordingly creative activity of high interfacial country

( ~ 2000m2/m3 ) . Ousters therefore, give superior gas-liquid mass transportation rates and higher rates of reaction as compared to conventional gas-liquid contacting equipments like moved armored combat vehicles, bubble columns, packed columns, etc. , Yadav and Patwardhan ( 2008 ) stated that there could be diverse aims for ouster design depending on application as follows:

( a ) To acquire big entrainment of the secondary fluid.

( B ) To bring forth intense blending between the two fluids.

( degree Celsius ) To pump fluids from a part of low force per unit area to a part of high force per unit area.

Geometry of ouster

The important parts of an ouster are ( Refer Figure 2.19 ) primary unstable recess, suction chamber, secondary fluid recess, meeting subdivision, pharynx or blending zone, diverging subdivision or diffusor. The ouster may be specified by denoting nozzle diameter, pharynx diameter, diameter of suction chamber, length of pharynx, length of diffusor, distance between noses to beginning of pharynx, angle of meeting subdivisions and angle of diverging subdivisions. Performance of the ousters has been studied in footings of ( a ) country ratio, i.e. , country of throat/area of nose, ( B ) pharynx aspect ratio i.e. , length of throat/diameter of pharynx, ( degree Celsius ) projection ratio i.e. , distance between nozzle tip to the beginning of pharynx / diameter of pharynx and ( vitamin E ) suction chamber country ratio.

Tocopherol: PHD DRAWINGAbysD1.jpg

Figure 2.19: Conventional diagram demoing geometry of an ouster

Dutta and Raghavan ( 1987 ) studied and compared the public presentation of jet ousters with and without Venturi and pharynx. Similarly Gamisans et Al. ( 2002 ) studied jet ouster without diffusor. Both of them concluded that the jet ousters without diffusor or pharynx are less effectual compared to ejector with them.

Many research workers have studied the mass transportation features and public presentation of the jet ousters followed by contactors, bill of exchange tubing, jammed column or bubble column

( Li and Li, 2011 ; Rahman et al. , 2010 ; Balamurugan et al. , 2008, 2007 ; Utomo et al. , 2008 ; Mandal, 2010 ; Mandal et al. , 2005 ; 2004, 2003a, 2003b ; Havelka et al. , 2000, 1997 ; Dutta and Raghavan, 1987 ; Ogawa et al. , 1983 ; Mitchell, 1981 ; Biswas et al. , 1977 ) . All have similar decision that there is less aggregate transportation coefficient in the drawn-out part compared to that in the ouster itself.

Consequence of ouster geometry

Das and Biswas ( 2006 ) reported that the efficient operation of an ouster depends on the design of the suction chamber, the commixture pharynx, the divergent diffusor and the forcing nose. Besides, the comparative dimensions of the assorted parts of the ouster, the factors such as form of the entryway to the parallel pharynx, angle of divergency and the projection ratio are besides of import factors to be considered.

Different research workers have studied the consequence of geometry of jet ouster like country ratio, angle of convergence and divergency, projection ratio, form of entry of convergent subdivision, length of pharynx etc. , Yadav and Patwardhan ( 2008 ) compiled dimensions of different constituents of ousters studied by different research workers ( See Table 2.7 ) .

Area ratio ( AR )

The country ratio is defined as the ratio of country of pharynx to country of the nose

Bonigton ( 1964 ) studied the consequence of altering the diameter ratio i.e. ratio of nozzle diameter to throat diameter ( / ) alternatively of country ratio of the jet ouster public presentation. Acharjee et Al. ( 1975 ) , Singh et Al. ( 1974 ) , Bhat et Al. ( 1972 ) and Mitra et Al. ( 1963 ) studied the consequence

of country ratio on Mass ratio ( ratio of mass of driving fluid to the entrained fluid ) . It can be concluded from these surveies that as the country ratio is increased the entrainment ratio besides increases. But at the higher country ratio the addition in entrainment ratio becomes less. A typical correlativity is shown in Figure 2.20.

*Indicate the optimal value suggested by the research worker

Table 2.7: Geometric parametric quantities of ousters used by deferent research workers

( Yadav and Patwardhan, 2008 )

Tocopherol: images4.9.jpg

Figure 2.20: Consequence of country ratio on mass ratio for water-water system

( Singh et al. , 1974 )

Projection ratio

The projection ratio ( ) is defined as the ratio of the distance between the shooting nose to the beginning of pharynx ( ) to diameter of pharynx ( )

A typical secret plan of vs. is presented in Figure 2.21. It is observed that as rises the entrainment ratio is non much effected but at definite value of, the MR, rises all of a sudden and E: images4.10.jpg

Figure 2.21: Variation of entrainment of air with projection ratio of water-air system

( Acharjee et al. 1975 )

once more falls to old value. Thus the at which it draws maximal entrained fluid is considered to be optimal. Biswas et Al. ( 1975 ) , Acharjee et Al. ( 1975 ) and Devis et Al. ( 1967 ) had likewise observed that at around 2.10 is optimal. Singh et Al. ( 1974 ) in their research survey observed optimal as around 0.5. It has been suggested that the optimum is influenced by geometry of entryway to the commixture tubing. Table 2.7 shows that the optimal value of suggested by the different research workers is different. Yadav et al. , ( 2008 ) utilized computational fluid kineticss ( CFD ) patterning to analyze the function of, angle of meeting subdivision and diameter of suction chamber. They studied the consequence of PR ( 0, 2.5, 5, 10 and 14.5 ) on entrainment, force per unit area profile along the axis of ouster and power efficiency. They concluded that the rate of entrainment and power efficiency additions as the projection ratio additions that is because of the fact when 1 increases the it leads to the decrease in the coevals of radial flow. However beyond & gt ; 5 negligible sum of radial flow is generated and therefore the rate of entrainment and energy efficiency remain changeless. Hence it may be considered that the optimal projection ratio is 5 Figure 2.22 ) .

Figure 2.22: Consequence of projection ratio ( LTN/DT ) on energy efficiency

( Yadav and Patwardhan, 2008 )

Diameter of suction chamber

Though transverse sectional country of the suction chamber is of import parametric quantity which effects the public presentation of Venturi, it has non been given the necessary attending. Yadav and Patwardhan ( 2008 ) studied the consequence of diameter of suction chamber. To analyze the consequence of suction chamber diameter they defined suction chamber country as

They concluded that maximal power efficiency ( 20 to 25 % ) is obtained for =6.6 and for & gt ; 13.6 it remain changeless. ( Refer Figure 2.23 ) Degree centigrade: Documents and SettingsARCHITECTUREDesktop2.23.jpg

Figure 2.23: Consequence of country ratio on efficiency of ousters for different values of projection ratio ( Yadav and Patwardhan, 2008 )

Consequence of angle of convergent subdivision and divergent subdivision

It can be seen from Table 2.7 that figure of research workers have worked to happen optimal angle of convergence and divergency. Yadav and Patwardhan ( 2008 ) studied the consequence of angle of convergence on entrainment and efficiency. In Figure 2.24 entrainment for different angles: 2.5Es , 10Es , 30Es and 90Es has been shown. It can be seen that the rate of entrainment is low for I? = 2.5Es . It increases with addition in I? and attains a maximal value for I? =10Es . Further addition in I? consequences in lessening in the rate of entrainment of the secondary fluid. Similarly their survey shows that the largest force per unit area driving force is generated for I? = 10Es and it consequences in the highest entrainment for this instance. With addition in I? beyond 10Es the force per unit area driving force was observed to cut down and it consequences in lessening in the rate of entrainment. They besides showed that highest efficiency is obtained at I? =10Esand larger values of I? consequences in hapless energy efficiency. Therefore, they suggested for obtaining maximal entrainment the angle of convergent may be kept between 5Es-15Es . The angle of divergent subdivision has been kept between 7Es to maximum 10Es by many of the research workers.

Tocopherol: images4.12.jpg

Figure 2.24: Consequence of angle of meeting subdivision iˆ?i?±iˆ© on rate of entrainment

( Yadav and Patwardhan, 2008 )

Mathematical theoretical accounts

Utomo et Al. ( 2008 ) developed three dimensional CFD theoretical account to look into mass transportation features. They varied the gas-liquid flow ratio in the scope of 0.2 to 1.2 and the length to diameter ratio of blending tubing ( / ) from 4 to 10. Their CFD surveies show that at

, the volumetric mass transportation coefficient increases with regard to gas flow rate. They observed that at, the graph of volumetric mass transportation coefficient vs gas-liquid flow rate ratio reaches the upper limit at gas-liquid flow rate ratio of 0.6. A singular observation in their survey was that volumetric mass transportation coefficient decreases with the addition of blending tubing length. They validated consequences obtained from CFD with the experimental consequence ( constellation of ouster has a commixture tubing diameter of 22 millimeters and diffuser mercantile establishment diameter of 40 millimeters, diffuser angle of 3.5 and a bill of exchange tubing length of 100 mm. ) . The blending tubing lengths are varied between 88 and 220 millimeter with the nozzle diameter of 8.5 millimeter.

Kandakure et Al. ( 2005 ) developed a CFD theoretical account to understand the hydrodynamic features of ousters. They varied the value of the faux pas speed between the stages for proof maintaining nozzle speed invariable ( at different tallness to diameter ratio of pharynx ) to formalize the theoretical account. They found that when the faux pas speed is made 13 % of the axial H2O speed, it matches the experimental informations really good. They found that the predicted air entrainment is the upper limit for the ouster with tallness to diameter ratio of pharynx equal to zero and the country ratio of 4. They justified that the CFD simulations eliminate all such empiricist philosophy.

Kim et Al. ( 2007 ) studied the consequence of the ouster geometry ( nozzle diameter and blending chamber diameter ) and the operating conditions ( liquid circulating rate, liquid degree in column ) on the hydraulic features in a rectangular bubble column with a horizontal flow ouster. They found that the gas stage armed robbery additions with increasing liquid circulating rate and decreases with increasing liquid degree in the column. They applied the multiphase CFD simulation with the mixture theoretical account and concluded that the gas suction rate additions with increasing liquid circulation rate contrarily the gas suction rate lessenings with increasing the liquid degree in the column and nozzle diameter. The predicted values obtained from CFD simulation were compared with the experimental information, which were good fiting.

Li and Li ( 2011 ) investigated the entrainment behaviour and public presentation of gas-liquid ousters utilizing different package and computational technique like Computational Fluid Dynamics ( CFD ) and validated with experimental informations over a broad scope of operating conditions for ouster with different constellations.

2.3.3 Parameters other than geometry of the ouster

Many research workers ( Gamisans et al. , 2004, Gamisans et al. , 2002, Brahim et al.1984 ; Bhutada, and Pangarkar, 1987 ; Acharjee et al. , 1975, Singh et al. , 1974 ; Bhat et al. , 1972 ; Davis et al. , 1967 ; Mitra and Roy 1964 ; and Mitra et al. , 1963 ) studied consequence of mass ratio ( MR ) as a map of motor force per unit area, suction force per unit area, centrifuge force per unit area, force per unit area bead, AR, PR, Reynold ‘s figure, Euler ‘s figure etc. Some of research workers ( Mitra et al. , 1963 ; Bonington 1964 ) studied the consequence of caput ratio on ouster public presentation, caput ratio is defined as:

where = force per unit area caput at discharge of ouster, m ; = force per unit area caput at suction of ouster, m ; and = operating force per unit area, m. The empirical equations to foretell mass ratio ( MR ) from dimensionless analysis given by assorted writers are summarized in Table 2.7a. Similarly table 2.7b summarizes mass ratio ( MR ) correlativities from theoretical analysis given by assorted writers.

Primary fluid

Secondary fluid

Geometry and scope investigated

Mass ratio correlativity

Writers

Air

Water

Flow-upward:

Davies et Al. ( 1967 )

Water, glycerol, kerosine

Air

Flow-horizontal:

Bhat et Al. ( 1975 )

Water, glycerol, kerosine

Air

Flow-upward:

Acharjee et Al. ( 1975 )

Water, mono ethene ethanediol

Air

Flow-downward:

Ben Brahim et Al. ( 1984 )

Water

Air

Flow-downward:

Dutta & A ; Raghvan ( 1987 )

Water

Air

Flow-downward:

Bhutada & A ; Pangarkar ( 1987 )

Water

Water

Flow-horizontal:

Singh et Al. ( 1974 )

Table 2.7a: Mass ratio correlativities from dimensionless analysis given by assorted writers ( Balamurugan et al. ( 2007 )

Geometry and scope investigated

Geometry and the locations where the energy and impulse balance were taken

Correlation and comments on loss coefficient

Writers

Flow-horizontal:

Bhat et Al. ( 1975 )

Primary fluid-water, glycerol and kerosine

All the losingss are clubbed as loss factor and values of were fitted utilizing experimental consequences

Secondary fluid-air upper limit

was through empirical observation fitted to and

= a?’

Each country ratio has different and the value ranges from 0.01 to 0.06

Flow-upward:

Acharjee et Al. ( 1975 )

Primary fluid

Water, glycerol, kerosine

All the losingss are clubbed as loss factor and was fitted to fit

the experimental values

Secondary fluid-air

Each country ratio has different and value ranges from 0.01 to 0.28

Flow-horizontal:

Entire suction was obtained for individual stage from loss at each subdivision

Biswas and Mitra ( 1981 )

Primary fluid-water, nacl, acetone-water mixture ( 30 % ) and glycerin ( 30 % )

Entire suction created partly utilised for entrainment and scattering

Secondary fluid-air

Maximum

and are fitted from experimental informations

Flow-horizontal: reappraisal of bing informations, individual stage

Entire loss coefficient = 1 a?’ diffusor efficiency + oss coefficient of pharynx

and were obtained from experimental informations of old writers besides individual loss coefficient was proposed. Value of scopes from 0.21 to 0.34

Henzer ( 1983 )

Table 2.7b continued

Continued from old page

Flow-downward:

Brahim et Al. ( 1984 )

Primary fluid-water, mono ethene ethanediol

Secondary fluid-air

All the losingss are clubbed as loss factor and was fitted with

experimental values. Valuess of scopes from 3-7

Maximum L/G = 15

Table 2.7b: Mass ratio correlativities from theoretical analysis given by assorted writers

Bonington ( 1964 ) published a secret plan of power efficiency vs caput ratio with diameter ratio as parametric quantity. As per their carbon monoxide relation the maximal efficiency achieved is about 33 % at caput ratio 4 and diameter ratio ( ratio of diameter of nose to throat diameter ) 0.52. Similar surveies have besides been done by Yadav and Patwardhan ( 2008 ) , Gamisans et Al. ( 2004 ) , Cunningham ( 1974 ) and Blenke et Al. ( 1963 ) .

Yadav and Patwardhan ( 2008 ) defined Energy efficiency of ouster as

Where

and

where is absolute force per unit area at diffusor mercantile establishment, Pa ; is absolute force per unit area at pharynx, Pa ; flowrate of secondary fluid, is denseness of the primary fluid, ;

, diameter of nose, m ; , speed of primary fluid at mercantile establishment of nose.

2.4 Gas soaking up in jet ouster

In any soaking up procedure, whether followed by a chemical reaction or non the gas must foremost be dissolved in the liquid. Thus, gas liquid mass transportation is one of the most cardinal stairss in finding the soaking up rate or the overall reaction rate. ( Charpentier, 1976 )

There is bare literature available on the survey of mass transportation in jet ouster. The rate of mass transportation is expressed by analyzing interfacial country between two stages, liquid side mass transportation coefficient and gas side mass transportation coefficient ( Shabani, 2010 ) . There are different factors which influence the value of a, and.

Physico-chemical factors

Solubility of solute in liquid stage and its diffusivity, concentration of responding reagent in the liquid, reaction rate changeless, reaction equilibrium invariable, viscousness and denseness of liquid, etc. are of import physico-chemical factors. Danckwerts ( 1967 ) showed the consequence of alteration in temperature at the surface ( ensuing due to the heat of soaking up and the heat of reaction ) on alteration in concentration of the merchandise of the reaction at the surface and depletion of reactant dissolved in liquid at the surface ( in instance of pseudo-first order reaction ) .

Shabani et Al. ( 2010 ) has been reported that mass transportation rate is a terrible map of solution concentration and effectual interfacial country.

Hydrodynamic factors

Gas flow rate, liquid flow rate and gas to liquid flow ratio are chief hydrodynamic factors which affect the rate of soaking up. Laurent ( 1978 ) established the hydrodynamic features in the jet ouster. They studied the influence of the gas and liquid flow rates and the diameter of the ouster on the rate of mass transportation.

2.4.1 Methods of finding of interfacial country

There are chiefly three methods used to find the interfacial country that are reported in the literature:

1. Measuring the bead size and bead size distribution

2. Photographic method

3. Chemical method

In the present survey the chemical method for mensurating interfacial country is used. In this method, gas-liquid chemical reaction is utilized to mensurate the interfacial country and volumetric mass transportation coefficient. One of responding constituent ( known as solute ) like and from gas stage is absorbed in liquid stage which contains another reactant like ammonium hydroxide, Na carbonate, dithionite, cupric chloride, acerb sodium carbonate or Na sulfite. Oyevaar and Westerterp ( 1989 ) concluded that the mistake in interfacial country measured by chemical method is less than 10 % and 20 % for automatically agitated reactor and bubble column severally, if the transition is less than 99 % . Raghuram ( 2009 ) used photographic method to find interfacial country and bubble diameter.

Weisweiler and Rosch ( 1978 ) studied interfacial country and bubble size distribution in jet reactors utilizing system. They used chemical method to look into interfacial country.

2.4.2 Determination of interfacial country by chemical method

Harmonizing to the survey of Dehkordi and Savari ( 2011 ) , the theory of gas soaking up accompanied by a chemical reaction explained by Danckwerts ( 1970, 1968 ) , has been widely used to measure the volumetric liquid-side mass-transfer coefficient and the specific interfacial country a in assorted gas-liquid contactors.

See a chemical reaction between gas constituent and a constituent in liquid stage. This reaction may be written as follow:

( 2.23 )

If the reaction is irreversible of the mth order in and order in, the local rate of reaction per unit volume may be expressed by

( 2.24 )

where and are the local concentrations of and severally. Doraiswamy and Sharma ( 1984 ) stated that if reaction satisfies

and

where, , , and are the solubility of gas in the aqueous solution, initial concentration of reactant B, molecular diffusivity of in the aqueous solution, and the mass-transfer coefficient, severally.

Then the reaction between and happen wholly in the movie, and the concentration of B at the interface is practically the same as that in the majority of the liquid stage. Here represents the ratio of the sum of responding in the movie to that of sum A reacting in the majority. If the reaction is pseudo-mth order in and the rate of soaking up of component per unit volume of the reactor can be expressed by

Here, it may be interpreted that under these status the rate of soaking up is independent of or the hydrodynamic conditions. So it means that if reaction is fast pseudo-mth order, so by holding the cognition of solubility of the gas ( ) , the molecular diffusivity of the gas constituent dissolved in the liquid stage ( and the kinetic parametric quantities of the reaction

( i.e. , , and ) , specific interfacial country can be evaluated by finding by experimentation rate of soaking up of per unit volume of the reactor ( ) .

Jhaveri and Sharma ( 1968 ) compared the work of different research workers who studied soaking up accompanied by pseudo order reaction to measure the effectual interfacial country, , as a map of the liquid flow rate in a research lab jammed column. Oxygen was absorbed in aqueous solutions of cupric chloride and Na dithionite. Isobutylene was absorbed in an aqueous solution of sulphuric acid. There is a good understanding among the values of obtained by utilizing different systems. The value of appears to be a alone map of the liquid flow rate in the scope of liquid belongingss covered in their probe ( ionic strength 1 to 34.5 g ion/1, viscousness 1 to 9 cP ) .They further concluded that the effectual interfacial country remains practically the same irrespective of the responding species and the dynamicss of the reaction. Similarly Gemisans et Al. ( 2002 ) studied different agreement of jet ouster like individual phase, two phase with and without secondary jet and without pharynx utilizing soaking up of and from the gas into and solutions severally. They studied the consequence of fluctuation in solute concentration, air flow rate and absorbing solution flow rate. They observed that the liquid flow rate have strong influence on where as the solute concentration and gas flow rate have slight influence. These consequences are in consonant rhyme with the observations of Jhaveri and Sharma ( 1968 ) . They have besides concluded that there was considerable betterment in soaking up efficiency in instance of two phase jet ouster holding merely one jet, but at that place was increased energy ingestion. Shabani et Al. ( 2010 ) and Laurent et al. ( 1978 ) studied the parametric quantities impacting the interfacial country in a jet ouster utilizing system. Both of them have reported similar consequences that interfacial country additions with increasing liquid speed up to certain degree. There are several research workers who worked on the chemical method for the finding of interfacial country in gas liquid contactors ( Raghuram et al. , 1992 ; Oyevaar and Westerterp, 1989 ; Ogawa et al. , 1983 ; Virkar and Sharma, 1975 ; Sahay and Sharma, 1973 ; Volgin et al. , 1968 ) .

2.4.3 Determination of overall volumetric mass-transfer coefficient by chemical method

Doraiswamy and Sharma ( 1984 ) derived a correlativity which may be used to find the overall volumetric mass-transfer coefficient by chemical method. If the reaction is an irreversible mth order with regard to and order with regard to, and fulfill the status

so the reaction between the gas and the liquid can take topographic point wholly in the majority of the liquid stage and there is negligible reaction happening in the movie. Furthermore, if the reaction between the gas constituent and the liquid is sufficiently fast, such that the concentration of un-reacted constituent in the majority of liquid stage is negligible so the soaking up rate of gas per unit volume of the gas-liquid reactor ( ) can be expressed as

( 2.29 )

To guarantee such status the reaction should fulfill

Therefore if and the solubility of the gas constituent in the liquid stage are

known, so the volumetric mass transportation coefficient can be by experimentation evaluated utilizing the above equation.

2.4.4 Restrictions of the chemical method for the finding of mass transportation coefficient

The specific surface country for mass transportation in the gas-liquid contactor is the cumulative country of all the bubbles or beads or movie divided by the volume of sample.

However the physical methods of finding interfacial country step the local Sauter mean diameter and therefore local interfacial country. But for practical intents one demand to find an overall interfacial country for the full contactor. The chemical method of finding interfacial country makes it possible to find straight the overall interfacial country over the full contactor. Charpentier ( 1982 ) observed that the difference between the interfacial country measured by the chemical method and photographic method may be due to a little figure of big bubbles ruling the interfacial country by the accidental exclusion of little bubbles by the photographic method.

Joosten and Danckwerts ( 1973 ) introduced rectification factor I? which they defined as ratio of addition of liquid soaking up capacity to increase of mass transportation due to chemical reaction.

Government

Parameter to find

Order

Minimum value of

Maximum value of

Physical soaking up or decelerate chemical reaction

3.3

0.25

Intermediary imposter Thursday order chemical reaction

and

1

4.0

0.20

Rapid imposter Thursday order chemical reaction

0

A?

1

2

2

1.35

1.80

2.60

3.70

4.80

0.48

0.48

0.30

0.21

0.16

Instantaneous chemical reaction

3.3

0.27

Instantaneous chemical reaction at the interface

20

0.55

= recess solute gas concentration. = rate of soaking up, = gas abode clip, = reduced diffusion clip,

= soaking up efficiency.

Table 2.8: Restricting values of and for the assorted chemical governments used to mensurate the mass transportation parametric quantities ( Midoux et al. , 1980 )

Due to presence of chemical compound the coalescency rate reduces well and therefore chemical method may take to error for the fast coalescing systems. Midoux et Al ( 1980 ) proposed a flow theoretical account for shriveling & A ; non shriveling bubbles. Table 2.8 presents the modification conditions which can be used to minimise the mistake in gauging mass transportation parametric quantities by chemical method.

Charpenter ( 1982 ) suggested that complimentary conditions proposed by research workers be verified before utilizing their informations for graduated table up.

2.4.5 Consequence of the ouster geometry on the mass transportation features

Cramers and Beenackers ( 2001 ) investigated the consequence of geometrical design parametric quantities like the presence of a swirl device in the upstream subdivision of the nose, the commixture tubing length and the ratio of nose to blending tubing diameter ratio. They observed that all these parametric quantities have important consequence on the mass transportation features. They besides studied the influence of gas denseness on mass transportation features and observed that the volumetric mass transportation coefficient ( ) increases when higher denseness gases are used. There are some other research workers who carried out similar surveies ( Balamurugan et al. , 2008, 2007 ; Gourich, 2007 ; Baier, 2001 ) . Table ( 2.9 ) is comprehensive list and the co-relations given by different research workers ( Balamurugan et al. , 2007 ) .

Their probes may be summarized as follows:

Influence of the whirl device

For the same the ouster with swirl device causes higher gas stage force per unit area difference. The ouster without a swirl device creates higher values compared to the ouster with a swirl device in the nose. The value of additions with addition in. In instance of presence of twirling device, there are two distinguished flow governments seen viz. bubble flow and annulate flow. The ouster without a swirl device creates higher values as compared to the ouster without twirling device because it utilizes the supplied energy more efficaciously. In similar survey, Zheng et Al. ( 2010 ) and Baier ( 2001 ) ( Figure 2.25 ) concluded that the gas armed robbery and interfacial country are larger in instance of jet ouster without whirl compared to gush ouster with whirl.

System

Dimensions ( m )

Method of measuring

Correlation

Writer

Hold-up

Up, primary-water ;

secondary-air

2, 3

Otake et Al. ( 1981 )

Up, primary-water ;

secondary-air

Type 1:

Type 2:

Type 3:

= 0.292

1

1

Zahradnik et Al. ( 1982 )

Up, primary-water ;

secondary-air

1

1

Zahradnik et Al. ( 1982 )

Up, primary-water ;

secondary-air

2,4

2

1

,

Ogawa et Al. ( 1983 )

Up, primary-water ;

secondary-air

superficial speed

1

1

Rylek and Zahradnik ( 1984 )

Up, primary-water ;

secondary-air

Zahradnik et Al. ( 1985 )

Downward, primary-water ;

secondary-air

1

Bhutada and Pangarkar ( 1987 )

Table 2.9 continued

Continued from old page

Downward, primary-solution of

and ;

secondary-air + mixture

3

2

Dutta and Raghavan ( 1987 )

Up, primary-sodium sulfite

solution, secondary-air

2

1

Bando et Al. ( 1990 )

Downward, primary-water ;

secondary-air

1

Dirix ( 1990 )

Downward, primary-water ;

secondary-air

Not mentioned

1

Cramers and Dierendonck ( 1992 )

Downward, primary-water ;

secondary-air

1

Cramers and Dierendonck ( 1992 )

Up, primary-water ;

secondary-air

2

Zahradnik et Al. ( 1997 )

Up, primary-water ;

secondary-air

2

Havelka et Al. ( 1997 )

Downward, primary-water ;

secondary-air

Not mentioned

1

Cramers and Beenackers ( 2001 )

Downward, primary-water,

CMC ; secondary-air

2

Mandal et Al. ( 2003 )

Downward, primary-water ;

secondary-air

3

2

Mandal et Al. ( 2003 )

Holdup measuring methods: 1. Bed enlargement method ; 2. difference of inactive force per unit area along the column ; 3. flicker picture taking for bubble size appraisal ; 4. picture taking for bubble size appraisal. Mass transportation appraisal measuring methods: 1. Dynamic method-monitoring of unsteady O soaking up into antecedently deoxygenized H2O in the bed, i.e. on the rating of system response to an input measure alteration nitrogen-air ; 2. soaking up in Na sulfite solution with Cobaltous sulphate as accelerator ; 3. soaking up of tilt in the mixture of and. Interfacial country measuring methods: 1. soaking up in Na sulfite solution with Cobaltous sulphate as accelerator ; 2. soaking up of CO2 in aqueous solution of Na hydrated oxide.

Table 2.9: Hold-up, and measurement methods and correlativities given by assorted writers

Figure 2.25: Influence of the swirl device on the entire gas armed robbery ( Iµtot )

( Baier, 2001 )

Influence of the nose to blending tubing diameter ratio or )

When utilizing a swirl device lessenings with increasing diameter ratio. When no swirling device is used so there exists an optimal diameter ratio about 0.38. They correlated as follow

and

Influence of the commixture tubing length

For the standard ouster ( / = 2 ) , the blending zone is located in both the commixture tubing and in a big volume of the diffusor. However, when the commixture tubing length is increased, it is found that the commixture is about completed in the commixture tubing. This indicates that the initial scattering volume ( blending zone volume ) is influenced by the ouster constellation. From this ocular observation, it can be concluded that the blending zone volume of an ouster with a / ratio of 10 is smaller compared to the blending zone volume of an ouster with a shorter blending tubing. They besides noted that this observation is in dissension with the

experiment of Dirix and Wiele ( 1990 ) , the commixture tubing length has no influence on ( kLa ) . ( Figure 2.26 )

Figure 2.26: Influence of the commixture tubing length on ( Baier, 2001 )

Utomo et Al. ( 2008 ) have besides studied the consequence of blending tubing length on volumentric mass transportation coefficient. They concluded that an ouster with longer blending tubing creates lower volumetric mass transportation coefficient compared to shorter blending tubing. It is seen that by increasing /ratio, the volumetric mass transportation coefficient lessenings for any gas liquid flow rate ratios. They besides explained that when the commixture tubing length is increased, the force per unit area bead is besides increased.

Influence of the gas denseness on mass transportation features

In the bubble flow government, the volumetric mass transportation coefficient additions when higher denseness gases are used. The consequences could be explained by utilizing Levich ‘s theory, i.e. when the gas denseness additions, smaller bubbles get dispersed ensuing in an addition of the kLa value.

( Figure 2.27 )

Figure. 2.27: Influence of gas denseness on without swirl device ( Baier, 2001 )

Influence of liquid viscocity on mass transportation features

kLa [ s-1 ] Baier ( 2001 ) investigated the consequence of viscocity on mass transportation coefficient.They explained that the volumetric mass transportation coefficient decreases with addition in liquid viscousness ( Figure 2.28 ) . They compared their consequences with Terasaka and Hideki ( 1991 ) , Sedelies et Al. ( 1987 ) and Stein and Schafer ( 1984 ) and found good understanding

Figure 2.28: Influence of the liquid viscousness on ( Baier, 2001 )

2.4.6 Factors set uping mass transportation features

Biswas et Al. ( 1977 ) studied the effectual interfacial country in a liquid jet induced horizontal gas-liquid contactor. They determined the effectual interfacial country at assorted gas liquid throughputs by chemical method. Their consequences are summarized as follows:

At same motor liquid flow rate, interfacial country additions with increasing secondary liquid flow rate. Interfacial country is relative to flux of secondary fluid ( gas ) , .

Maximum interfacial country ( approx. 2400mA?/mA? ) is created by the nozzle holding country ratio 9.3

At same suction gas flow rate, higher interfacial country is achieved by increasing motor fluid flow rate ( liquid ) .

Interfacial country can be predicted by empirical correlativity

( 2.33 )

Where is the fraction of gas hold up based on entire system volume ( dimensionless )

is the fraction of gas armed robbery at no faux pas ( dimensionless )

Specific interfacial country produced for same energy/volume to jet ouster is much higher compared to that produced in jammed bed, jet contactor and bubble column.

2.4.7 Use of jet ouster in reactor

The usage of jet ouster in the loop-reactor has been reported in the literature ( Gourich et al. , 2007 ; Tang et al. , 2006 ; Ping-fang Han et al. , 2005 ; Havelka et al. , 2000 ; Dierendonck et al. , 1998 ; Ogawa et al. , 1983 ) . These surveies have reported about the hydrokineticss and the factors impacting the mass transportation features of the jet ouster used in the different profiles of loop-reactors.

Weisweiler and Rosch ( 1978 ) observed that the interfacial country and per centum transition addition with increasing jet speed. When jet speed is increased the transition increases depending on the gas throughput and at high jet speed a maximal transition of about 100 % is achieved. Liquid jet speeds of less than 10 m/s barely affect the interfacial country for the scattering of the gas watercourse into little bubbles. The liquid jet must be extremely disruptive which is ensured when the jet speed exceeds 10 m/s.

Gourich et al. , ( 2007 ) and Dierendonck et al. , ( 1998 ) compared the public presentation of jet ouster in cringle reactor with conventional gas liquid contractors. Their findings were similar to Weisweiler and Rosch ( 1978 ) that cringle ouster Venturi contactors are various tools to transport out both fast and slow reactions.

Raghuram ( 2009 ) studied interfacial country in gas-liquid ouster for a Na chloride-air system for a ouster holding same nose and pharynx diameter ( 3mm ) . They observed that for given flow rate of air and liquid the interfacial country decreases easy as scattering is moves off from the nose. They besides reported that interfacial country additions with increasing liquid to air ratio. They achieved interfacial country of the melody of

Dierendonck et Al. ( 1998 ) concluded that the cringle ouster Venturi reactors are an efficient option to the moved armored combat vehicle reactors, offering easier scale-up.

2.4.8 Mass transportation features in multi nose jet ouster

Radhakrishnan and Mitra ( 1984 ) studied multi nozzle liquid gas ousters, and observed that optimal ratio of length of pharynx to diameter of pharynx is between 6 to10. Similarly optimal country ratio is from 14.56 to 16.39 and gave the co-relation for gas hold up as

( 2.34 )

( 2.35 )

Where fractional liquid hold up i.e. ratio of liquid volume to the volume of system

– figure of openings in the nozzle home base and are Reynold ‘s Numberss based on superficial liquid and gas speed on the tubing diameter.

They reported co-relation for interfacial country of system, :

. ( 2.36 )

They besides reported that the optimal public presentation is obtained with nozzle holding = 14.6, This nozzle gave maximal specific interfacial country per unit energy input.

2.4.9 Mass transportation with chemical reaction

Danckwerts ( 1970 ) proposed in agitated movie diffusion, convection and reaction proceed at the same time. To do any utile anticipation about the behaviour of such systems, it is necessary to utilize highly-simplified theoretical account which simulate the state of affairs sufficiently good for practical intents without presenting a big figure of parametric quantities which are hard to find.

There are many conjectural theoretical accounts to foretell the consequence of chemical reaction on soaking up rate in the literature.

Whitman ‘s ‘Laminar movie theoretical account ‘ ( 1923 ) : steady-state diffusion through a dead movie

Higbie ‘s ‘Systematic surface reclamation ( incursion ) theoretical account ‘ ( 1935 ) : transeunt soaking up into surfaces which are consistently replaced by fresh liquid

Danckwerts ‘s ‘Random surface reclamation theoretical account ‘ ( 1951 ) : transeunt soaking up into surfaces which are indiscriminately replaced.

Danckwerts and Kennedy ( 1954 ) compared these three theoretical accounts and showed that the three theoretical accounts lead to closely similar anticipations about the consequence of physico-chemical variables ( solubility, diffusivity, reaction rate etc. ) on the rate of soaking up.

Wall and Beek ( 1967 ) compared chemosorption and physical soaking up and concluded that chemsorption is more than physical soaking up.

Vieth et Al. ( 1963 ) derived an equation which describes the mass transportation to a fluid in to the full developed turbulent flow in a pipe. They explained that their correlativity for mass transportation is indistinguishable with the well-known Chilton-Colburn analogy ( 1934 ) . They extended their analysis to the instance of coincident mass transportation and irreversible first-order chemical reaction and found that the solutions of their correlativity in understanding with fact is reported by Danckwerts and Kennedy ( 1954 ) for incursion and movie theoretical accounts.

However the surveies by Beltran et Al. ( 1998 ) , Danckwerts et Al. ( 1963 ) and Richards et Al. ( 1964 ) had compared different theoretical accounts for different systems and have reported the consequence of assorted parametric quantities.

2.4.10 Reaction systems used to qualify mass transportation with chemical reaction

Sadek et Al. ( 1977 ) proposed a theoretical account for the coincident soaking up of S dioxide and Cl into assorted acid.

Ravindram and Pyla ( 1986 ) besides proposed a theoretical theoretical account ( based on coincident diffusion and an irreversible chemical reaction ) for foretelling the sum of gaseous pollutant removed in a venturi scrubber. For proof of their theoretical account they used system of and soaking up in dialute. They found first-class understanding between the consequences predicted by the theoretical account and those by experimentation determined.

Chlorine

Chlorine is one of the most polluting gases in procedure industries. The soaking up of Cl in aqueous solution of Na hydrated oxide is normally commercially practiced method to cover with Cl pollution. There have been a few surveies on the soaking up of in to aqueous Na hydrated oxide solution in different gas-liquid contactors. ( Roy and Rochelle, 2004 ; Ashour et al. , 1996 ; Lahiri et al. , 1983 ; Hikita et al. , 1973 )

Hikita et Al. ( 1973 ) studied the rate of soaking up of pure Cl into assorted concentrations of aqueous Na hydroxide solution at They used a liquid-jet column for their research survey. They applied incursion theory for gas soaking up accompanied by a two-step instantaneous chemical reaction. The experimental consequences were in good understanding with the theoretical anticipations. They termed their theoretical account “ two reaction-plane theoretical account ” as shown below:

Aqueous solution containing and exists in the part between the gas liquid interface and the first reaction plane ( part 1in Figure 2.29 ) , C: Phd 1-6-2012edit thesis finalksa fig 1 22-6-12.jpg

Figure 2.29: Concentration profiles for soaking up of into aqueous solution

( Hikita et al. , 1973 )

Aqueous solution containing, and exists in the part between the first reaction plane and the majority of liquid ( part 2 in Figure 2.29 ) ,

The theoretical anticipations and the experimental observations by Spalding and Takahashi et Al. are in good understanding.

Tamir et Al. ( 1975 ) concluded that the neglecting of the consequence of the gaseous environment every bit good as majority flow part is non justified for soaking up of gases with high solubilities and big heat effects. They presented a incursion theoretical account and validated the theoretical account by utilizing the soaking up of Cl into methylbenzene ( investigated by experimentation by others ) . They found a divergence of 25 % between computations based on simplified theoretical account and the more general theoretical account presented by them

Lahiri et Al. ( 1983 ) deliberated on the soaking up of Cl in aqueous solution of Na hydrated oxide with coincident desorption of hypochlorous acid ( followed by its dissociation to chlorine monoxide ) at 55A°C and 75A°C in a moved contactor with a level gas-liquid interface. A moderately good understanding has been found between the theoretical anticipations and experimental observations.

Roy and Rochell ( 2004 ) measured the soaking up rate of Cl into aqueous solution of sulfite/bisulfite utilizing a stirred-cell reactor and a wetted-wall column in the scope pH 4.7 and 5.7. They developed a theoretical account utilizing the theory of mass transportation with fast reaction. They besides reported that there is sweetening of soaking up by utilizing the succinate buffer on the rate of Cl hydrolysis. They besides found that the di-succinate consequences in greater sweetening of soaking up than the mono-succinate anion and the add-on of Na chloride ( ) every bit good oxygen did non impact the rate of soaking up in S ( IV ) . They opined that these consequences are relevant in the coincident remotion of Cl, S dioxide and elemental quicksilver from flue gas.

Sulpher dioxide

Uchida and Wen ( 1973 ) simulated soaking up of in and alkalic solution utilizing a mathematical theoretical account developed by them. They compared the deliberate consequences based on their theoretical account with experimental informations obtained in several types of Venturi scrubbers that showed satisfactory understanding.

Charpentier ( 1976 ) published a reappraisal paper in which he presented. Different theoretical and empirical correlativities to cipher and.

Laurent et Al ( 1978 ) studied soaking up with chemical reaction in Venturi jet scrubber. They used decelerate irreversible reaction to step and fast pseudo mth order reaction for.

Asai et Al. ( 1986 ) analyzed the rate of mass transportation accompanied by chemical reaction of general order continuing in two uninterrupted stages on the footing of the two-film theory. They could happen satisfactory truth.

Atay et Al. ( 1987 ) developed empirical theoretical accounts to depict the fluid flow features and gas soaking up efficiency of ouster Venturi scrubber. They determined the S dioxide soaking up efficiency by experimentation on a commercial scrubber.

Bandyopadhyay and Biswas ( 2007, 2006, 2006a ) , studied the remotion of utilizing H2O and dilute base as scouring media in a tapering bubble column scrubber. They observed the sweetening of remotion of due to presence of particulate affair in the base scouring media.

Carbon Dioxide

Mandal et Al. ( 2003b ) investigated by experimentation, and, in a down flow bubble column by chemical method viz. , soaking up of in aqueous Na hydrated oxide and Na carbonate/bicarbonate buffer solutions severally. The equipment consists of jet ouster followed by bubble column. They developed correlativities to foretell and in footings of superficial gas speed by using Polynomial arrested development analysis of the experimental informations,

( 2.37 )

and

( 2.38 )

They besides compared the experimental information with the predicted values obtained from above equation and found that it fitted really good.

Silva and Danckwerts ( 1973 ) studied the consequence of adding a little measure of halogen ( Cl or Br ) to a watercourse of C dioxide on soaking up rate of C dioxide. The add-on of a little measure of Cl or Br additions greatly the rate of soaking up of the C dioxide into alkalic solutions. This is due to the formation of hypochlorite ion or hypobromite ion in the solutin which are accelerators for the reaction between and H2O.

Similar surveies were done by utilizing -alkali systems by different research workers ( Cents, 2005 ; Gomez and Navaza, 2005 ; Meikap et al. , 2004, 2001 ; Dimicocoli et al. , 2000 ; Alvarez et al. , 1980, 1981 ; Pohoreckie, 1968 ; Vidwans and Sharma, 1967 ; Danckwert and Kennedy, 1958 ) .

Many research workers, ( Bhatt et al. , 2010, 2007 ; Gandhi et al. , 2009 ; Ahari et al. , 2008 ; Gulbeyi and Cevdet, 2006 ; Yusuf et al. , 1999 ; Cooney, 1992, 1985 ; Yaici et al. , 1988 ; Cooney and Olsen, 1987 ; Botton et al. , 1987 ; Mahajani and Sharma, 1981, 1980, 1979 ; Midoux et al. , 1984 ; Ogawa et al. , 1983 ; Charpentier, 1982, 1976 ; Laurent and Charpentier, 1974 ; Shende and Sharma, 1974 ; Volgin et al. , 1968 ; Jhaveri and Sharma, 1968, Danckwerts and Sharma, 1966 ) have proposed theoretical accounts to foretell soaking up with chemical reaction by analyzing different reaction systems.

Kordac and Linek ( 2008 ) studied the consequence of add-on of salt and ace impregnation, on the mass transportation coefficient of C dioxide-water system. Their experiments show that mass transportation coefficients are enhanced by the consequence of liquid ace impregnation.

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