A laboratory-scale continuous flash evaporator

VACUUM Classltled Abstracts

III

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Vacuum

Processing

Techniques

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III

Coutd

39 - -

MISCELLANEOUS

PROCESSES

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abstr.¢t So and Reference~

39

Production of Ammonium Nitrate by Continuous Vacuum Crystalhsatton Umted States The operation of a continuous v a c u u m crystalhsatlon p l a n t as described for the production of fertlhser-grade a m m o m u m nitrate crystals The process is based on a m e t h o d described previously b y Miller and Saeman, and is safer and more economical t h a n the graining process The sequence of operations is given as follows N e u t r a h s a t l o n of nitrate acid w i t h ammonia, purification and concentration of the a m m o n i u m nitrate solution, crystalhsatlon, drying and bagging The purified a m m o n i u m nitrate solution is concentrated to 79% content of a m m o n i u m nitrate in forced-circulation v a c u u m evaporators operating at a pressure of 2 4 inch H g with a capacity of 7,000 lb of w a t e r v a p o u r per hour, four units working in parallel Crystalhsatlon is carried out in five v a c u u m units, each designed to produce 105 tons of a m m o n i u m nitrate crystals per d a y T h e y consist essentially of a suspension container, a centrifugal circulation p u m p , a vaporlser, and a barometric leg The, container holds 23,000 gallons of the suspension The vaporlser is 9 ft in diameter The feeding rate is 50 gallons per m i n u t e The suspension is circulated from the container to the v a p o n s e r where it is supers a t u r a t e d b y evaporative cooling The s u p e r s a t u r a t e d solution is r e t u r n e d to the b o t t o m of t]le suspension container to p r e v e n t the crystals from settling out Excess crystal nuclei collecting on the surface are removed, and the suspension is reclrculated to the vaporlser The finished crystalline p r o d u c t s are collected continuously b y air lifts from the suspension container 65~o of the final crystals average + 20 and 97% + 35 m e s h in size Operation can be continuous for several m o n t h s w i t h o u t de-salting The crystalhsers operate in the t e m p e r a t u r e range of 90 I ° F to 100°F in order to produce f o r m - I I I crystals instead of f o r m - I V which would be produced below 90 ! ~'F The p r o d u c t consists of single, rounded crystals containing a m i n i m u m of 33~o nitrogen ~ommazre Ddtafls d ' u n e installation de productions rdcemment 6rlgde, p o u r la m a n u f a c t u r e de crlstaux de nitrate d ' a m m o m u m selon une mdthode de crlstalhsatlon continue sous vide, bas6e sur les prlnclpes de production proposals p a r Miller et Saeman

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Article by W C Saeman, I W McGamy & E G Houston Industr Eng~ 9 Chem 44, Aug 1952 1912-1915

A Laboratory-Scale Continuous Flash Evaporator qee \ b s t r a c t No 201 III

215/III

Frozen Concentrated Pineapple Juice Hawa~ A new p l a n t w o r t h one million dollars for the production of frozen concentrate of pineapple juice has been p u t into operation The processing in the plant is s o m e w h a t different from t h a t of orange juice processing, for instance, w i t h regard to the m e t h o d of recovering ~ olatlle esters and re-introducing t h e m into t h e final p r o d u c t A n o t h e r special feature of the p l a n t is the faclhtles it offers for 24-hours continuous operation, a l t h o u g h fresh lmce for processing is received during 6 hours of the day only The process consists of seven steps as follows (1) F r e s h Juice is prepared in the usual m a n n e r (2) I n a c t i v a t i o n of enzymes by heat t r e a t m e n t and p u m p i n g to the concentration plant (3) A small a m o u n t is collected in a separate t a n k for blending at a later stage The greater p a r t is fed into a high v a c u u n l low t e m p e r a t u r e triple-effect e v a p o r a t o r for partial concentration and separation of the volatile esters (4) The esters are treated in a special v a c u u m fractlonatlng still The concentrated esters are stored at a t e m p e r a t u r e of 35°F (5) The partially concentrated lume is returned to the e v a p o r a t o r for a second pass at a slower rate resulting in a 66 ° Brlx concentration During this operation pressure in the first effect averages 50 m m Hg, m the second 35 m m Hg, and in t h e third 25 m m H g (6) Blending This is effected b y mixing set quantities of single s t r e n g t h cut-back juice and volatile flavour concentrate to the 66 ° Brlx lulce concentrate reducing the density of the final p r o d u c t to 47 ° Brlx (7) Canning and freezing The latter process is carried o u t in an air blast tunnel 86 ft long, 16 ft wide, and fitted with a 10 ft wide conveyor The t u n n e l operates at -40°C for 18 hours per day The remaining 6 hours it is used for freezing pineapple chunks Sommazre Description ddtalllde d ' u n e installation de production a grande ecbelle, de jus d'ananas, congel6 concentrd

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Article b~ A A Smyse: Food Engnq 24, Aug 1952 72-169, 170, 172

Study of Vacuum Fumtgahon Techniques See A b s t r a c t No 197/III

217/III

Method and Apparatus for Fusing Dielectric Material in a Partial Vacuum by High-Frequency Electric Fmlds

218/II!

See A b s t r a c t No

196/I

O n New Methods of Insulating Very Low Temperature Apparatus

See A b s t r a c t No

202/I

The Analysis of Heat Transfer through Thermal-Insulating Materials See A b s t r a c t No 201/I

October 1952

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Vac uum Vol [ I No d

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