Use of a Centrifugal Pressure Nozzle as a Chemical Reactor

I = incrementally-cut powder

k = equilibrium constant

n = index number for equilibrium stage N = total number of stages R = raffinate flow rate (mass/time) RC = rotary-cut powder ri = radius of particle of phase i s1 = surface to volume ratio (length-1) for particle of

phase i

x = ratio of impurity mass to raffinate mass xn = ratio of impurity mass to raffinate mass leaving stage n y = ratio of impurity mass to extract mass y n = ratio of impurity mass to extract mass leaving stage

n

p1'

= effeceive density including void volume of phase i (mass/length3)

Literature Cited Bennet, C.O., Meyers, J.E., "Momentum, Heat, and Mass Transfer," Chapter 39, McGraw-Hill, New York, N. Y.. 1962. Porter, J.J., Lyons, D.W., Nolan, W.F., Environ. Sci. Techno/., 6 , 38 (1972). Robertson, G.H., Morgan, J.P., Text. Chem. Coiorist, 5 (5), 98 (1973). Saville, N., Shelton, W.J., Ward, R . . Sewell, J., West Riding Worsted & Woolen Mills Ltd., Comersai Mills, Cleckheaton, Yorkshire, England, 1971, Sherwood, T.K., Pigford. R.L.. "Absorption and Extraction," p 406, McGraw-Hill. New York, N. Y., 1952. Truter, E. V . , "Wool Wax,"Cleaver Hurne Press Ltd., London, 1956.

Greek Letters = density of phase i (mass/length3)

Receivedfor review November 5, 1973 Accepted July 18, 1974

pi

Use of a Centrifugal Pressure Nozzle as a Chemical Reactor Milton D. Marks, Jr., and Edwin J. Crosby* Department of Chemical Engineering, University of Wisconsm, Madison, Wisconsin 53706

The feasibility of using a centrifugal pressure nozzle as a chemical reactor for the manufacture of selected solid products in particulate form was demonstrated by the production of powdered sodium stearate. Stoichiometric quantities of molten stearic acid and aqueous sodium hydroxide were fed separately to the slightly modified adapter for the nozzle with the resulting mixture being sprayed into unheated air and collected as a flowable powder a short distance from point of atomization. Powders containing greater than 98 wt YO (dry basis) sodium stearate and ranging in size from 10 to 100 were produced.

Introduction

A major goal of process technology is the development of simpler and more efficient methods for producing desired products and performing required operations. In the specific case of particulate solids, a variety of methods are used. The production of many products may include a number of steps such as a chemical reaction, purification, precipitation, solvent separation, drying, and comminution. Such procedures can be costly in terms of the initial capital investment, operation, and low process efficiency. In addition, when numerous processing steps are involved, many variables usually must be controlled to ensure a product of adequate quality. The development of a simple and convenient means to transform the raw material directly into the particulate product with a minimum of intermediate processing steps offers definite advantages. For a process which involves the fairly rapid and essentially irreversible reaction of two or more liquid reagents to produce a nonvolatile product in the form of a molten solid, a slurry, or a concentrated solution, the intimate contact of these reagents in the body of a spray nozzle could lead to the direct production of particulate solids. If the reaction were completed within the nozzle proper, then any cooling and/or drying could occur in a spray chamber. If the reaction were not completed in the nozzle, it possibly could continue within the drops after atomization. Any necessity for further comminution of the solids could be entirely eliminated. However, the physical nature of solid particles produced in this manner might be different from that of powders produced by other meth20

Ind.

Eng. Chem., Process Des. Develop., Vol. 14, No. 1, 1975

ods. Further, the time required for processing could be significantly reduced. Finally, the number of variables which would have to be monitored to maintain a desired quality of product also might be reduced. In order to demonstrate the feasibility of this technique in the manufacture of an existing product, the production of a powdered soap was chosen for study. This product was selected primarily because the reagents are immiscible at low temperatures and thermal degradation can occur at elevated temperatures. System Studied The specific chemical system chosen to test the proposed processing scheme was the formation of sodium stearate by the direct neutralization of the fatty acid. This system was picked not only for convenience but also because of its commercial importance. Chemistry and Kinetics. Soaps can be prepared either by the saponification of a natural glyceride or by the direct neutralization of the fatty acids. The use of direct neutralization is a more recent development which was brought about by the advent of efficient processes for the continuous hydrolysis of glycerides. Sodium hydroxide and potassium hydroxide are the most commonly used alkalies for both saponification and neutralization. In the present study, stearic acid was reacted with aqueous sodium hydroxide. n-C1,H,,COOH

+

NaOH(aq) e n-C,,H,,COONa(aq)

+ HOH

This reaction is slightly reversible, exothermic, and essentially autocatalytic (Smith, 1932). Typical forms of the conversion and rate curves for this reaction are shown in Figure 1. The reaction begins as a slow, interfacial reaction between the two immiscible reagents. However, both stearic acid and sodium hydroxide are soluble in aqueous sodium stearate. Consequently, as more soap forms and dissolves greater amounts of the remaining reactants, the rate of conversion is greatly accelerated by the transition from an interfacial reaction to a homogeneous reaction. The duration of the interfacial reaction can be shortened by the use of elevated temperatures which greatly enhance the miscibilitv of the reagents, by the generation of a highly dispersed initial emulsion which greatly increases the interfacial area between the reactants, and by the addition of a small amount of fatty acid when glycerides are being saponified. The rate of the homogeneous reaction is dependent on the nature of the soap phase present in the mixture. Most commercial processes operate with soap concentrations between 50 and 75 wt % and with the soap in its “neat-soap” phase. “Neat soap” is a particularly good solvent for the unreacted fats, fatty acids, and alkali. Commercial Processes. Successful saponification of glvcerides and neutralization of fatty acids can be accomplished by either batchwise or continuous processing (Furnas. 1942; Kent. 1962). Currently there are two batchwise and four continuous methods in common use for the manufacture of soap. Although many other schemes have been proposed, apparently few of these have been implemented industrially. The two batchwise processes are the “boiling pan” or “kettle” method and the “cold process.” The “boiling pan” method is essentially a refinement of original schemes for making soap. In this process (Wigner, 1940), the reagents are mixed and reacted at 100°C in large, heated, steam-agitated kettles. The soap is precipitated as a curd by a strong brine solution. This curd is washed several times and then is converted into “neat soap.” After solidification in large drying frames, the soap is molded into bars or converted into chips, flakes, or powder. The “cold process” relies primarily on the heat of reaction and on diffusional processes for heating and mixing, respectively. The four commonly employed continuous processes are the Mon Savon, the Unilever, the Sharples, and the De Laval Centripure processes (Jones, 1958). In the Mon Savon and the Tjnilever processes finely dispersed initial emulsions are formed to promote a rapid initiation of the reaction. The Mon Savon process uses a colloid mill operating at 100°C and the 1Jnilever process employs a steam jet emulsifier. The Sharples and the De Laval Centripure processes avoid the interfacial reaction entirely by using concentrated soap solutions. The Sharples process uses a two-stage centrifuge system to separate the unreacted alkali from the soap, while the De Laval Centripure process carefully controls the alkali content in the reaction chamber which is maintained a t 120°C. One of the reportedly largest plants in existence using the De Laval Centripure mehod continuously neutralizes fatty acids obtained from glyceride hydrolysis to produce about 1900 bars of soap per minute (Ladyn, 1964: Meinhold, 1965). Alternate Processes. Many other schemes have been proposed for producing soap as is evident from a review of the U. S. Patents for the past 60 years. At least three of these are of interest to the present work. Lorenz and Brown (1937) patented a process to produce anhvdrous soap powder by spraying an emulsion of fats and alkali into superheated steam. Dickinson and Moreton (1938) patented a process in which fats, alkali, and steam were

@

z >

W

8

E:! INDUCTION PERIOD I

I

I

OO TIME

TIME

Figure 1. Typical reaction hiqtories for neutraiization of fatty acids (Jones. 1958: Levenspiel. 1362).

mixed in a nozzle at the verge of atomization. Later Lorenz (1941) patented a revised version of the patent issued to Lorenz and Brown in which the operation of the proposed process was more specifically outlined. It is somewhat difficult to determine whether any of these processes were reduced to practice because of the apparent lack of experimental evidence to substantiate the various claims made in the patents. Process Investigated. In the proposed process for the production of powdered sodium stearate, the stearic acid and the sodium hydroxide are supplied to the process with the acid above 70°C in order to keep it molten and the hydroxide as an aqueous solution of desired concentration. The reagents are pumped separately, but in stoichiometric proportions. by metering pumps through heat exchangers designed to heat the streams very rapidly to temperatures high enough to promote miscibility. The heated reagents then pass at moderately high pressures, which depend on the operating temperatures and on the desired nature of the powdered product. into separate inlets of a suitably modified adapter for a centrifugal pressure nozzle. This modified adapter acts as a mixing chamber for the two streams. An alternate arrangement is the replacement of the adapter with a small mixing chamber equipped with a mechanical stirrer. However, this scheme introduces problems related to the sealing of moving parts. In either case, the residence time within the mixing unit is minimum and no stagnant fluid regions exist. The reagents are intimately contacted a t or near their point of entry into the mixing unit and the chemical reaction proceeds quite rapidly and goes essentially to completion. After a very short residence time within the spray nozzle, the aqueous sodium stearate is sprayed into a drying chamber where the necessary conditions to produce a powder of the desired moisture content exist. The final product then is removed from the tower bv conventional means for packaging or for further processing. Experimental Procedure Apparatus. The experimental equipment used in this study is schematically represented in Figure 2. It was designed to produce about 8 lb of sodium stearate per hour at temperatures up to 400°C: and at pressures up to 300 Ind. Eng. C h e m . , Process Des. Develop., Vol. 14, No. 1 , 1975

21

SWAGELOK FITTING 1/16 I D PLUG1

[WITH

REAGEhiT

STREAM

O R I F CE NSERT

Figure 3. Centrifugal pressure nozzle with modified adapter.

Figure 2. Schematic diagram of experimental apparatus

psig. Molten-stearic acid, blanketed with nitrogen to prevent oxidation. was supplied from an electrically heated. stainless steel storage tank and the sodium hydroxide was supplied from a carboy. These reagents were metered in approximately stoichiometric quantities by separate gear pumps (Zenith Products Co., Type B440'7, size no. 2 a t rated displacement of 1.168 cm3irev for the sodium hydroxide and size no. 5 a t rated displacement of 2.920 crn3/rev for the stearic acid) driven through a single variable-speed transmission (Graham Transmissions, Inc., 0-195 rpm) by a Ih-hp electric motor. The pressure of each stream was monitored immediately downstream from the pumps. A stainless steel pressure transducer was used with the stearic acid to minimize the hold-up of the acid which might have solidified in the tube of a standard pressure gauge. Each stream was equipped with a rupture disk mounted a t the same point as the transducer or gauge. The heat exchanger for each reagent consisted of 5 ft of lh-in. 0.d. stainless steel tubing traced with a 576-W electric heater for the acid and a 626-W electric heater for the sodium hydroxide. Between the pumps and the heaters as well as prior to the pumps, each stream was equipped with an electric preheater which could generate 450 W for the acid and 153 W for the sodium hydroxide. The two streams then passed to a centrifugal pressure nozzle (Delavan Manufacturing Co., Type SDS, size 3is in. with a no. BE distributor and orifices of either 0.055 or 0.038 in. in diameter) whose standard adapter was modified to promote intimate mixing of the reagents. The entire assembly of atomizer and adapter was electrically traced with a 125-W heater. The temperatures of the stearic acid in storage, of' each stream immediately upstream from the pumps, of each stream immediately downstream from the heat exchangers, and in the mixing section of the atomizer were measured with no. 30 iron-constantan thermocouples mounted in thin-walled stainless steel thermowells. In this study the spray chamber was a large stainless steel container fitted with a partial cover which allowed all vapors to escape readily while the powder was collected. Nozzle Modification. The adapter for the nozzle was modified, as shown in Figure 3, to promote intimate mixing of the two streams. This modification consisted of screwing a specially designed stainless steel plug into the adapter and introducing two inlet ports as illustrated. This plug provided a mixing and reaction zone 3/16 in. in diameter and in. long. These dimensions were compatible with the flow rates used. A thermowell of l , in. ~ 0.d. tubing protruded about 5h2 in. into the mixing chamber and provided an annular region adjacent to the inlet ports. In order to determine which arrangement of the inlet 22

Ind. Eng. Chem., Process Des. Develop., Vol. 14, No. 1 , 1975

ports promoted reasonably rapid and complete mixing of the reactants, several configurations were investigated. The mixing action was studied qualitatively by observing the flow patterns of water dyed with a green food coloring and undyed sucrose solution in a transparent, plastic (Lucite) replica of the mixing chamber. This replica was overdimensioned externally with one side machined flat and polished to permit good viewing of the flow conditions. The viscosity ratio between the sucrose solution and water a t room temperature was chosen to match or exceed the estimated viscosity ratio of 8:1 between the stearic acid and sodium hydroxide solution at the processing temperatures investigated. To allow improved visual observation and photographic recording of the mixing action, viscosity ratios as high as 14:l were used. Mixing at lower viscosity ratios was expected to be somewhat more efficient than that a t higher viscosity ratios. The plastic model of the mixing chamber was fabricated to allow installation in the experimental equipment in place of the modified adapter for the centrifugal pressure nozzle. To improve observation and recording of the mixing action, the pump speeds were somewhat below those used during actual operation and ranged from 10 to 25 rpm. Since the basic characteristics of a given mixing pattern tended to persist as the flow rates were increased, it seemed reasonable that the most advantageous arrangement a t low flow rates was likely to be equally advantageous at somewhat higher rates. Eight variations of location for the inlet ports and insertion of the thermowell were studied. In all instances the volumetric flow rate of the water was 40% of that of the sucrose solution. These flow rates corresponded to those of the sodium hydroxide solution and stearic acid, respectively. The configurations for the mixing chamber and the resulting flow patterns are illustrated in Figure 4. The broad arrows show the motion of the fluids and the shaded regions indicate the unmixed sucrose solution. In configuration A the water entered radially into the chamber while the sucrose solution was fed tangentiallv so as to cut across the water inlet. A distinct swirling motion occurred in the direction of the incoming sucrose solution. This flow pattern persisted throughout the chamber. The incoming water was deflected toward the base of the thermowell and subsequently swirled in the annular region between the thermowell and the wall of the chamber. No marked stream segregation was noted even a t the lower flow rates. Configuration B was the same as configuration A except that the thermowell was removed. In this instance the swirling action was considerably reduced and a distinct segregation of the two streams was apparent. Even a t higher flow rates the mixing characteristics of this configuration were very poor. In configuration C the sucrose solution was fed radiallv into the chamber and the water entered tangentiallv so as to cut across the inlet of the sucrose solution. There was a certain amount of swirling near the inlet ports in the direction of the entering

CONFIGURATION

A

CONFIGURATION E

CONFIGURATION

8

CONFIGURATION F

CONFIGURATION

c -zp

CONFIGURATION G

0

c\

i

,

CONFIGURATION CONFIGURATION D'

.

__

.

'

H

-n'

Figure -2. Configurations for mixing chamber and resulting flow patterns

water stream. However, this swirling motion was not maintained throughout the chamber. Even a t its most intense point a t the base of the thermowell, the swirl was never as intense as that observed for configuration A. Configuration D was the same as configuration C except for the absence of the thermowell. For this arrangement the incoming water initially moved toward the outlet end of the chamber and then swirled in loop-fashion back toward the rear of the chamber. There was moderate segregation of the two streams. In configuration E both streams entered radially into the mixing chamber a t right angles to each other. Both streams impinged on the thermowell and divided into smaller streams. The uater stream split into two main branches. One branch swirled around the base of the thermowell and the other branch swirled in the same direction around the tip of the thermowell. The swirling motion produced by this configuration did not produce as effective mixing as that in configurations A and C. Configuration F differed from configuration E only by the absence of the thermowell. In this instance the water impinged on the unbroken stream of the sucrose solution and also split into two main branches. The one branch flowed around the entering stream of sucrose solution and then rejoined the other branch. There was insufficient swirl to promote reasonable mixing in the chamber. In configuration G the two streams entered the mixing chamber in radial opposiion to each other. Both streams impinged on the thermowell and divided into smaller streams. The water formed two major loops. One loop developed beyond the tip of the thermowell in a plane with the entering streams. The other loop developed near the inlet port for the sucrose solution in a plane perpendicular to the entering streams. This pattern of the two perpendicular loops persisted a t considerably higher flow rates. The mixing produced by this configuration was of the same level as that for configuration E. Configuration H was the same as configuration G except that the thermowell was removed. The sucrose solution traversed the mixing chamber as an unbroken stream and impinged directlv on the inlet port of the water. This produced a large backmixing flow loop for the water near the rear of the chamber with little mixing elsewhere.

The presence of the thermowell in the mixing chamber materially enhanced the mixing for all the configurations studied either by breaking up the incoming streams or by directing the tangentially incoming stream toward the other stream through local reduction of the mixing volume. At very high flow rates, the thermowell was a less significant factor in the determination of the mixing patterns. Configurations E and G were less effective for promoting mixing than configurations A and C. Since the swirling action was more intense and persistent in configuration A than in configuration C, it was concluded that configuration A gave the highest degree o f mixing with the least segregation of the streams and was the best scheme for contacting the reagents. This is the arrangement shown in Figure 3 . The stearic acid was fed tangentially and the sodium hydroxide solution was fed radially into the mixing chamber. Operation. It was possible to produce experimental products a t as many as four sets of operating conditions per day. By not changing the conditions too drastically, the unsteady-state period between tests was relatively short and the amount of reagents used was minimized. On the basis of the rated pump displacetnents, the stearic acid and the sodium hydroxide were to be fed to the nozzle in nearly stoichiometric quantities. The concent ration of the sodium hydroxide solution was 25 wt cio for most of the tests conducted. Both heat exchangers and the mixing section of the nozzle were heated to about 350 to 400°C prior to pumping the reagents in order to achieve steady-state conditions more quickly. The preheaters and the pump fbr the stearic acid were also heated before starting I he process. When the system attained the desired temperature. the valves at the feed tanks were opened and the pumps were started. Usually about 15 to 20 min was required to bring the system t o the initial steady-state conditions. At the flow rates used. a steady-state period of 10 t o 15 min was sufficient to produce an adequate sample for analysis. At a pump speed of 22 rpm, the stearic acid had an estimated residence time of about 4 sec in its heat exchanger and about 1sec in the nozzle. The system was shut down and cleaned by cooling the Ind. Eng. Chem., Process Des. Develop., Vol. 14, No. 1, 1975

23

POROUS PAPER THERMOCOUPLE

97OOr

'

05 IO 15 20 25 30 35 SODIUM HYDROXIDE IN AQUEOUS STEARATE-HYDROXIDE MIXTURE, WT %

40

Figure ti. Effect of sodium hydroxide concentration on pH of aqueous solutions containing sodium stearate. c

_

_

SOLVENT FLASK

ELECTRIC MANTLE

VARIAC

Figure 5 . Modified Soxhlet extraction unit. equipment to between 80 and lOO"C, closing the valves at the feed tanks, and flushing with hot water. Analysis. In order to meet the standards of commercially available sodium stearate, it was necessary to produce a powder containing a t least 98 wt % sodium stearate with less than 0.5 wt % excess sodium hydroxide. Therefore, it was important to analyze quantitatively all experimental products for the amount of each chemical present. Since most of the commonly used methods for determining the purity of soaps, e.g., free fatty acid content, are based on the attainment of some equilibrium condition, they were not applicable to the present situation since equilibrium was not anticipated. Consequently, a method of analysis which would preclude continuance of the reaction beyond that obtained in the process was developed. The moisture content of the product was determined by drying the as-received powder in a vacuum oven a t room temperature. It was found that stearic acid could be readily extracted from the dried powder by refluxing warm benzene a t 60-65"C, L e , below the melting point of the acid, through the sample in the modified Soxhlet extraction unit shown in Figure 5. In this manner it was possible to remove any unreacted stearic acid while a t the same time minimizing the chance for further reaction between the acid and any sodium hydroxide present. The concentration of sodium hydroxide in the extracted powder was determined by measuring the pH of an aqueous solution of known concentration of the extracted powder (Leeds & Northrup. Model F664 pH meter with Calomel Reference Electrode No. 1199-45 and Glass Measuring Electrode No. 1199-31). The measured value of pH was then compared with an empirically established curve of p H us concentration of s o d i u m hydroxide which is shown in Figure 6. This procedure was possible because the pH of a dilute solution of aqueous sodium stearate is a weak function of the stearate concentration, while the pH of an aqueous sodium stearate-sodium hydroxide solution is a strong function of the hydroxide concentration in the ranges of concentrations of interest. This analytical procedure gave a quantitative analysis which proved to be reasonably accurate and reliable. The standard deviation of the measured sodium stearate concentration, based on 89 measurements, was estimated to be 0.85 wt %. Infrared spectroscopy was used as an approximate check on the quality of the extraction step in this analysis (Hen24

Ind. Eng. Chem., Process Des. Develop., Vol. 14, No. 1 , 1975

niker, 1967). Because of the limited resolution of the available equipment (Beckman Microspec), it was not possible to separate the carbonyl absorption peaks a t 5.9 p for stearic acid and a t 6.4 p for sodium stearate in mixtures containing more than 92 wt 70 sodium stearate. Differentiation between samples with a difference of less than a 5 wt % in sodium stearate concentration below the 92 wt 70 level was extremely difficult. Despite these limitations, the infrared spectra were useful verifications of the extraction procedure. In addition to the chemical analyses, several physical properties of the powders were recorded. The color, odor of fatty acid, and texture of each of the products were noted. Also, each of the powders was viewed microscopically to determine particle sizes and characteristics. Finally. the bulk densities of the powders were determined on a bone-dry basis by weighing the amount of dried powder which could be held in a glass vessel of approximately 6 ml volume when it was gently tapped to distribute and to settle the particles. The reported values were the average of five measurements which had an approximate standard deviation of 0.002 g/ml.

Results and Interpretation Products were produced in quantities of 2 to 3 lb a t 22 sets of operating conditions. The recorded conditions and the results of the chemical analysis, the infrared analysis, and the physical observations for each product are summarized in Table I. Technical grade sodium stearate powder was considered to be representative of commercially available sodium stearate and hence was used as a reference. The manufacturer's specifications for this powder are listed in Table 11. The results obtained when the chemical and physical analyses were applied to this commercial product are also reported in Table I. General Observations. For the operating conditions and system studied in this work, the proposed process functioned well. In all instances a flowable powder, whose flowability varied somewhat with moisture content and particle size, was obtained. Microscopic observation indicated that the particles were generally irregularly shaped and ranged from 10 to 100 p in size with aggregates as large as 300 g. Photomicrographs of the commercial product and an experimental product are shown in Figure 7 . The fragmentary nature of the particles in the experimental product is probably a result of the mechanism of atomization and the rapid quenching of the molten sodium stearate in the unheated drying medium. In general, the moisture content of the powders with low acid content decreased as the temperature in the mix-

Table I. Summary of Experimental Results

-

I____

Product analysis Experimental conditions

Quantitative procedure

Trial no.

Physical properties

_-___ Infrared,

-

OrificePump Temp, 'C Wt !&, d r y basis wt a Bulk diam, speed, _______-Wt 9; d r y basis, density, in. rpm Acid NaOH Mixer Acid NaOH NaSt" H 2 0 NaSt" g/ml ColorC Textured Odor" __

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

0.055 0.038 0.055 0.055 0.038 0.038 0.038 0.038 0.055 0.038 0.038 0.038 0.038 0.038 0.038 0.038 0.038 0.038 0.038 0.038 0.038 0.038

Comm.f

.,.

37 17 21 31 31 21 21 31 31 27 31 37 21 31 21 27 31 21 27 37 27 21

200 265 205 276 215 295 245 302 250 310 313 279 295 231 246 200 169 203 180 154 252 283

130 178 151 157 171 180 200 184 166 173 179 188 191 185 179 184 174 180 144 146 177 185

.. .

170 200 167 179 183 224 250 235 187 199 205 208 245 206 228 210 178 193 164 168 198 230

...

4.0 4.1 12.6 5.2 2.5 2.3 2.7 2.0 3.1 1.2 1.3 2.9 3.3 22.1 19.2 26.5 1.1 0.9 2.0 1.0 9.8 10.7 0.5

2.5 4.0 0.0 0.0 2.9 1.4 0.7 0.6 0.4 2.7 1.7 0.1 0.0 0.0 0.0 0.0 0.4 0.6 0.3 0.5 0.0 0.0 0.0

93.5 91.9 87.4 94.8 94.6 96.3 96.6 97.4 96.5 96.1 97.0 97.0 96.7 77.9 80.8 73.5 98.5 98.5 97.7 98.5 90.2 89.3 99.5

___

11.4 11.5 0.4 1.2 13.6 5.3 3.7 3.4 5.2 11.1 6.2 1.3 0.8 0.2 0.1 0.3 10.1 5.3 19.6 23.0 1.1 0.2 1.8

>92 >92 81-86 86-92 >92 >92 81-86 >92 81-86 >92 >92 86-92 81-86 i81 92 >92 >92 ,