VACUUM

Classltled Abstracts

III - - V a c u u m P r o c e s s i n g T e c h n i q u e s - - I I I abstr.¢t So and Reference~ Coutd

39 - - M I S C E L L A N E O U S P R O C E S S E S - - 39

Production of Ammonium Nitrate by Continuous Vacuum Crystalhsatton Umted States The operation of a continuous vacuum crystalhsatlon plant as described for the production of

fertlhser-grade a m m o m u m nitrate crystals The process is based on a method described previously by Miller and Saeman, and is safer and more economical than the graining process The sequence of operations is given as follows Neut rahsa t lon of nitrate acid wi th ammonia, purification and concentrat ion of the ammonium nitrate solution, crystalhsatlon, drying and bagging The purified a mmon ium nitrate solution is concentrated to 79% content of am m on i um nitrate in forced-circulation vacuum evaporators operat ing at a pressure of 2 4 inch Hg with a capacity of 7,000 lb of water vapour per hour, four units working in parallel Crystalhsatlon is carried out in five vacuum units, each designed to produce 105 tons of ammon ium nitrate crystals per day They consist essentially of a suspension container, a centrifugal circulation pump, a vaporlser, and a barometr ic leg The, container holds 23,000 gallons of the suspension The vaporlser is 9 ft in diameter The feeding rate is 50 gallons per minute The suspension is circulated from the container to the vaponse r where it is super- sa tura ted by evaporat ive cooling The supersa tura ted solution is re turned to the bo t tom of t]le suspension container to prevent 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 products are collected continuously by air lifts from the suspension container 65~o of the final crystals average + 20 and 97% + 35 mesh in size Operation can be continuous for several months wi thout de-salting The crystalhsers operate in the t empera ture 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 product consists of single, rounded crystals containing a min imum of 33~o nitrogen

~ommazre Ddtafls d 'une installation de productions rdcemment 6rlgde, pour la manufac ture de cr ls taux 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 par Miller et Saeman

A Laboratory-Scale Continuous Flash Evaporator qee \bs t r ac t No 201 III

Frozen Concentrated Pineapple Juice

H a w a ~ A new plant wor th one million dollars for the production of frozen concentrate of pineapple juice has been pu t into operat ion The processing in the plant is somewhat different from tha t of orange juice processing, for instance, wi th regard to the method of recovering ~ olatlle esters and re-introducing them into the final product Another special feature of the plant is the faclhtles it offers for 24-hours continuous operation, a l though fresh lmce for processing is received during 6 hours of the day only The process consists of seven steps as follows (1) Fresh Juice is prepared in the usual manner (2) Inact ivat ion of enzymes by heat t reat- ment and pumping to the concentrat ion plant (3) A small amoun t is collected in a separate t ank for blending at a later stage The greater pa r t is fed into a high vacuunl low tempera ture triple-effect evaporator for part ial concentrat ion and separat ion of the volatile esters (4) The esters are t reated in a special vacuum fractlonatlng still The concentrated esters are stored at a tempera ture of 35°F (5) The partially concentrated lume is returned to the evapora tor for a second pass at a slower rate resulting in a 66 ° Brlx concentrat ion During this operat ion pressure in the first effect averages 50 m m Hg, m the second 35 m m Hg, and in the third 25 m m Hg (6) Blending This is effected by mixing set quanti t ies of single s t rength cut-back juice and volatile flavour concentrate to the 66 ° Brlx lulce concentrate reducing the density of the final product to 47 ° Brlx (7) Canning and freezing The lat ter process is carried out in an air blast tunnel 86 ft long, 16 ft wide, and fitted with a 10 ft wide conveyor The tunnel operates at -40°C for 18 hours per day The remaining 6 hours it is used for freezing pineapple chunks

Sommazre Description ddtalllde d 'une installation de production a grande ecbelle, de jus d 'ananas, congel6 concentrd

Study of Vacuum Fumtgahon Techniques See Abstract No 197/III

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

See Abstract No 196/I

On New Methods of Insulating Very Low Temperature Apparatus

See Abstract No 202/I

The Analysis of Heat Transfer through Thermal-Insulating Materials

See Abst rac t No 201/I

214/III

Article by W C Saeman,

I W McGamy & E G Houston

Industr Eng~ 9 Chem

44, Aug 1952 1912-1915

215/III

216/Ili

Article b~ A A Smyse: Food Engnq

24, Aug 1952 72-169, 170, 172

217/III

218/II!

219/ii1

220/III

October 1952 Vacuum 437 Vol [I No d