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Design and Development of a Batch Fluidized Bed Freezer and Fluidized Bed Dryer for Diced Food Products1
Design and Development of a Batch Fluidized Bed Freezer and Fluidized Bed Dryer for Diced Food Products l
W. S. Reid Engineering Research Service Research Branch Agriculture Canada Ottawa, Ontarío
R. Stark Food Processing Section Research Branch Agriculture Canada Kentville, Nova Scotia
Abstract A fluidized bed freezer and a fluidized bed dryer is described for freezing or drying 5 or 15 kg batches of particulate food products using two sizes of plastic bed 30.4 or 45.7 cm diameter. Fluidization velocities can be up to 243 m/min in either bed. The freezer air temperature is controlled using hot gas bypass load cnotrol of the two stage condensing unit. Temperature control is within ±0.88°C throughout the range -17.8°C to --40°C. Freezing times for diced potatoes from 15.5°C to -23.5 oC can be achieved in 7.0 min for a 15 kg sample and 3.5 min for a 5 kg sample from 12.8°C. Similarly, 3.0 min ancl 6.2 min were required for 5 kg ancl 15 kg samples of diced apples. The dryer air is steam heated producing air temperatures up to 127°C, controlled within ±2°C aboye 64°C by a pneu-' matic cam programmer. Drying times to 10% moisture were in the range 1.5 to 3.5 h for 9.6 mm cube diced pota toes or apples depending on test conditions.
Résumé Un congélateur a lit fluidisé et un séchoir a lit fluidisé sont décrits pour la congélation ou le séchage de lots de 5 ou 15 kg de produits alimentaires particulaires utilisant deux tailIes de lit plastique de 30.4 ou 45.7 cm de diametre. Les vitesses de fluidisation peuvent atteindre 243m/min dans l'un ou l'autre des lits. La température de l'air au congélateur est controlée a l'aide d'un modérateur de charge a court-circuit de gaz chaud de l'unité de condensation a deux étages. La variation de la température est ±0.88°C pour la marge -17.8°C a --40 oC. Les temps de congélation pour des pommes de terre en cubes de 15.5°C a -23.5°C sont de 7.0 mino pour un échantillon de 15 kg et 3.5 mino pour un échnntillon de 5 kg partir de 12.8°C. Dans le cas de pommes en cubes, il a faIlu 3.0 mino et 6.2 mino respectivement pour des échantillons de 5 kg et de 15kg. L'air du séchoir, chauffé a la vapeur, peut atteindre 127°C. Les varíations de température n'excede pas ±2°C aux températures excédant 64 o e et le controle de la température se fait par un programmeur a carne pneumatique. Les temps de séchage a 10% d'humidité ont été dans la marge de 1.5 a 3.5 h. pour des pommes ou des pommes de terre en cnbes de 9.6 mm suivant les conditicns de l' essai.
a
Introduction The unit described was designed for freezing, drying, 01' dehydrofreezing batch quantities of diced 01' whole vegetable and fruit products as a versatile pilotplant to provide laboratory size samples similar to those producpd by industrial techniques. 1 Contribution No. 290 from Engineering Research Service. Can. Inst. Fcod Sci. Technol. J. Vol. 7, No. 4, 1974
Considerable work has been done on fluidization, particularly in the chemical engineering field, but in the food processing industry such work is limited. Scott et. al. (1967) designed a batch unit by modifying a commercial fluidized bed dryer. Three problems were identified as a result of testing this unit, namely: in· adequate low temperature performance, pOOl' operational flexibility, and caking of the frozen or diced product due to pOOl' initial fluidization. For operational flexibility two units, a freeezr and dryer, were combined in the new designo The main cost penalties were the additional ducting, fan motor and controls required. Drying and freezing could then be carried out simultaneously, and. this permitted precooling of the freezer section for rapid transfer from dryer to feezer during dehydrofreezing. Two bed sizes were incorporated to handle large 01' small samples (5 and 15 kg). Table 1 shows the final specification upon which the design was based as a result
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I
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nected to interstage through solenoid valve Z, Fig. 4. The function of valve AA is to give quick start-up after shut down and after pull down, 01' to help during an initial start-up, should the main suction pressure I'egulator fail to function. After start-up the hand valve is cloRed, and the suction pressure regulator pilot is operated from interstage pressure through solenoid valve Z. The fan and ducting foI' the dryer is similar to that of the freezer except that the air fl'Ow is single pass, with the option of utilizing ambient (external) air 01' room air (Fig. 3). Steam heating of the air was selected as being the most economical with system pressure,s up to 8.79 kg/cm 2 (Fig. 6). To cover the control requirements for large and small beds and high and low temperatures, a linear control valve 'of 2.61 Ov and high rangeability was incorporated, in conjunction with a resistance bulb response time of 0.25 sec (Rosemount 176MA24AC), located 25 cm after the fan 23fJ
Fig.
5.
Fluidized bed freezer refrigeration sehematie. A. evaporator - Keeprite, 4-8 24 x 30, 2 units; B. liquid line 0.95 em diam; C. suction line 5.4 em diam; D. hot gas bypass line 2.23 em diam; E. water outlet 3.17 em diam; F. regulating water valve - Penn, V46AD-l, 2.54 em NPT; e. filter dryer - Aleo, high eapaeity ADK - S485; H. hand valve - Meuller 1.6 cm pipe; 1. pilot valve hot gas bypass - Alco FAI8; J. regulator hot gas bypass - Aleo FA8-12H-S9; K. aeeumulator Refrigeration Researeh 5.4 em ODS 3838; L. suetion filter Aleo ADKS 30017; M. suetion pressure regulator - Alco 722-18, 5.4 em ODS; N. solenoid valve - Aleo 230R8MS5; O. expansion valve - Aleo ZZC2-1l2R.W6A; P. pilot equalizer lines, 0.64 em diam ; Q. power element assembly expansion valves Alco XC726RW6A; R. expansion valve - Aleo ZZCI-1/2RW6A; S. hand valve - Meuller VG-14; T. eondensing unit - Copeland W4WU-1000-R502; U. interstage piping 0.96 em diam ; V. sight glass Alco AMI-I-555; W. expansion valve Aleo LCL6CT53; X. solenoid valve Alca 200R-453T, 15W, 0.96 cm; Y. solenoid valve - Aleo S310-1, 2.24 em; Z. solenoid val ve - Sporlan A351 ; AA. hand valve - Imperial Eastman, 0.96 cm.
Fluidized bed freezer and dryer - eleetrieal distributCanadian eeneral ion sehematie. A. fan motor Eeleetrie 1l08, 5.6 kW induetion; B. main diseonneet -c.e.E. 3236, 100A, 3P; C. diseonneet - c .e .E. 2236, 60A, 3F; D . pilot light - c.e.E. OC212BC e/w 833A, 529-19; E. timer - Automatie Timing and Control s MTD 30 min; F. eontroller freezer - Honeyw e 11 servoline 452CIL-23-111-71 ; e . reeorder Honeywell servoline eontroller liquid ·n itrogen Y-452-CIL-34-111-71; H. on-off selector - c.e.E. CR2940 UB202A e/w 833A 529-30; l . timer - Automatie Timing and Control s MTD 6 h; J. solenoid valve Aleo 230 R8 M55; K. pneumatie recorcler cam programmer Honeywell 425FllL-71-111-60 ; L. solenoid valvc - Aseo 8262Cl; N. solenoicl valve Aseo 822C2L T, O. regulator hot gas bypass - Alco FAI8-12, H-59; P. temperature eontroller - Honeywell L4008 10-40-1 thermostat; Q. oil pressure cut out - Penn series 275; R. solenoid valve de-super heat Sporlan B6Fl ; S. high and low pressure eut out Ranco 012-4007; T. relay - C.e.E. CR2810 AI4AH2 ; U. switeh - c.e.E. CR2940 UA20313 e/ w 833A 5922; V. switeh - c.e.E. CR2940 UA202C e/w 833A 592-2 Hammond Ee.5J; Y. thennostate Honeywell L4008 1040; Z. contactor Fumas 42DC35; AA. relay - Heinnemann 071-0130-33 OL; BB. time clelay relay - c .e .E. CR2820 B110CAZ; CC. eompressor -Copeland, Copelmatie W4WU'-1000; DD. switeh c.e.E. CR2940 UA202B c/w 833A 592-2 ; EE. interlock kit - C.e.E. 392 L438-5 ; FF. starter - c.e.E. CR106P lAAP3 e/w 110V coil; ce. light fluoreseent - C and M Products R. 5.6024; HH. switeh - C.G.E. 86211 SN30A 2P; 11. circuit breaker - c.e.E. Fl TRP .460; JI. single ground outlet - c .e.E. 4094-2; KK. switch snap aetion - c.e.E. 5011-2.
outlet. This combination gave ±2°0 control from 64 to 127°0, below 64°0 control was within ±3.5°0. Reduction of steam pressure from 7.03 kg/cm 2 to 4.22 kg/cm 2 gave control of -+-1.5°0 throughout the mnge.
Testing Air distribution across the freezing coil and bed, adequate temperature control, quick pull down, electri cal, refrigeration and mechanical reliability, function and ease of 'Úperation were checked. Air distribution, air velocity and pressure drop were measured using either an anemotherm model 60 air meter 01' a J. Inst. Can. SeL Teehnol. AlIment. Vol. 7, No 4, 1974
W. S. Reid Engineering Research Service Research Branch Agriculture Canada Ottawa, Ontarío
R. Stark Food Processing Section Research Branch Agriculture Canada Kentville, Nova Scotia
Abstract A fluidized bed freezer and a fluidized bed dryer is described for freezing or drying 5 or 15 kg batches of particulate food products using two sizes of plastic bed 30.4 or 45.7 cm diameter. Fluidization velocities can be up to 243 m/min in either bed. The freezer air temperature is controlled using hot gas bypass load cnotrol of the two stage condensing unit. Temperature control is within ±0.88°C throughout the range -17.8°C to --40°C. Freezing times for diced potatoes from 15.5°C to -23.5 oC can be achieved in 7.0 min for a 15 kg sample and 3.5 min for a 5 kg sample from 12.8°C. Similarly, 3.0 min ancl 6.2 min were required for 5 kg ancl 15 kg samples of diced apples. The dryer air is steam heated producing air temperatures up to 127°C, controlled within ±2°C aboye 64°C by a pneu-' matic cam programmer. Drying times to 10% moisture were in the range 1.5 to 3.5 h for 9.6 mm cube diced pota toes or apples depending on test conditions.
Résumé Un congélateur a lit fluidisé et un séchoir a lit fluidisé sont décrits pour la congélation ou le séchage de lots de 5 ou 15 kg de produits alimentaires particulaires utilisant deux tailIes de lit plastique de 30.4 ou 45.7 cm de diametre. Les vitesses de fluidisation peuvent atteindre 243m/min dans l'un ou l'autre des lits. La température de l'air au congélateur est controlée a l'aide d'un modérateur de charge a court-circuit de gaz chaud de l'unité de condensation a deux étages. La variation de la température est ±0.88°C pour la marge -17.8°C a --40 oC. Les temps de congélation pour des pommes de terre en cubes de 15.5°C a -23.5°C sont de 7.0 mino pour un échantillon de 15 kg et 3.5 mino pour un échnntillon de 5 kg partir de 12.8°C. Dans le cas de pommes en cubes, il a faIlu 3.0 mino et 6.2 mino respectivement pour des échantillons de 5 kg et de 15kg. L'air du séchoir, chauffé a la vapeur, peut atteindre 127°C. Les varíations de température n'excede pas ±2°C aux températures excédant 64 o e et le controle de la température se fait par un programmeur a carne pneumatique. Les temps de séchage a 10% d'humidité ont été dans la marge de 1.5 a 3.5 h. pour des pommes ou des pommes de terre en cnbes de 9.6 mm suivant les conditicns de l' essai.
a
Introduction The unit described was designed for freezing, drying, 01' dehydrofreezing batch quantities of diced 01' whole vegetable and fruit products as a versatile pilotplant to provide laboratory size samples similar to those producpd by industrial techniques. 1 Contribution No. 290 from Engineering Research Service. Can. Inst. Fcod Sci. Technol. J. Vol. 7, No. 4, 1974
Considerable work has been done on fluidization, particularly in the chemical engineering field, but in the food processing industry such work is limited. Scott et. al. (1967) designed a batch unit by modifying a commercial fluidized bed dryer. Three problems were identified as a result of testing this unit, namely: in· adequate low temperature performance, pOOl' operational flexibility, and caking of the frozen or diced product due to pOOl' initial fluidization. For operational flexibility two units, a freeezr and dryer, were combined in the new designo The main cost penalties were the additional ducting, fan motor and controls required. Drying and freezing could then be carried out simultaneously, and. this permitted precooling of the freezer section for rapid transfer from dryer to feezer during dehydrofreezing. Two bed sizes were incorporated to handle large 01' small samples (5 and 15 kg). Table 1 shows the final specification upon which the design was based as a result
@®®®0CD
I
® ®
® ® ® ----® 1-c8O'::::-J
® Fig.
4.
nected to interstage through solenoid valve Z, Fig. 4. The function of valve AA is to give quick start-up after shut down and after pull down, 01' to help during an initial start-up, should the main suction pressure I'egulator fail to function. After start-up the hand valve is cloRed, and the suction pressure regulator pilot is operated from interstage pressure through solenoid valve Z. The fan and ducting foI' the dryer is similar to that of the freezer except that the air fl'Ow is single pass, with the option of utilizing ambient (external) air 01' room air (Fig. 3). Steam heating of the air was selected as being the most economical with system pressure,s up to 8.79 kg/cm 2 (Fig. 6). To cover the control requirements for large and small beds and high and low temperatures, a linear control valve 'of 2.61 Ov and high rangeability was incorporated, in conjunction with a resistance bulb response time of 0.25 sec (Rosemount 176MA24AC), located 25 cm after the fan 23fJ
Fig.
5.
Fluidized bed freezer refrigeration sehematie. A. evaporator - Keeprite, 4-8 24 x 30, 2 units; B. liquid line 0.95 em diam; C. suction line 5.4 em diam; D. hot gas bypass line 2.23 em diam; E. water outlet 3.17 em diam; F. regulating water valve - Penn, V46AD-l, 2.54 em NPT; e. filter dryer - Aleo, high eapaeity ADK - S485; H. hand valve - Meuller 1.6 cm pipe; 1. pilot valve hot gas bypass - Alco FAI8; J. regulator hot gas bypass - Aleo FA8-12H-S9; K. aeeumulator Refrigeration Researeh 5.4 em ODS 3838; L. suetion filter Aleo ADKS 30017; M. suetion pressure regulator - Alco 722-18, 5.4 em ODS; N. solenoid valve - Aleo 230R8MS5; O. expansion valve - Aleo ZZC2-1l2R.W6A; P. pilot equalizer lines, 0.64 em diam ; Q. power element assembly expansion valves Alco XC726RW6A; R. expansion valve - Aleo ZZCI-1/2RW6A; S. hand valve - Meuller VG-14; T. eondensing unit - Copeland W4WU-1000-R502; U. interstage piping 0.96 em diam ; V. sight glass Alco AMI-I-555; W. expansion valve Aleo LCL6CT53; X. solenoid valve Alca 200R-453T, 15W, 0.96 cm; Y. solenoid valve - Aleo S310-1, 2.24 em; Z. solenoid val ve - Sporlan A351 ; AA. hand valve - Imperial Eastman, 0.96 cm.
Fluidized bed freezer and dryer - eleetrieal distributCanadian eeneral ion sehematie. A. fan motor Eeleetrie 1l08, 5.6 kW induetion; B. main diseonneet -c.e.E. 3236, 100A, 3P; C. diseonneet - c .e .E. 2236, 60A, 3F; D . pilot light - c.e.E. OC212BC e/w 833A, 529-19; E. timer - Automatie Timing and Control s MTD 30 min; F. eontroller freezer - Honeyw e 11 servoline 452CIL-23-111-71 ; e . reeorder Honeywell servoline eontroller liquid ·n itrogen Y-452-CIL-34-111-71; H. on-off selector - c.e.E. CR2940 UB202A e/w 833A 529-30; l . timer - Automatie Timing and Control s MTD 6 h; J. solenoid valve Aleo 230 R8 M55; K. pneumatie recorcler cam programmer Honeywell 425FllL-71-111-60 ; L. solenoid valvc - Aseo 8262Cl; N. solenoicl valve Aseo 822C2L T, O. regulator hot gas bypass - Alco FAI8-12, H-59; P. temperature eontroller - Honeywell L4008 10-40-1 thermostat; Q. oil pressure cut out - Penn series 275; R. solenoid valve de-super heat Sporlan B6Fl ; S. high and low pressure eut out Ranco 012-4007; T. relay - C.e.E. CR2810 AI4AH2 ; U. switeh - c.e.E. CR2940 UA20313 e/ w 833A 5922; V. switeh - c.e.E. CR2940 UA202C e/w 833A 592-2 Hammond Ee.5J; Y. thennostate Honeywell L4008 1040; Z. contactor Fumas 42DC35; AA. relay - Heinnemann 071-0130-33 OL; BB. time clelay relay - c .e .E. CR2820 B110CAZ; CC. eompressor -Copeland, Copelmatie W4WU'-1000; DD. switeh c.e.E. CR2940 UA202B c/w 833A 592-2 ; EE. interlock kit - C.e.E. 392 L438-5 ; FF. starter - c.e.E. CR106P lAAP3 e/w 110V coil; ce. light fluoreseent - C and M Products R. 5.6024; HH. switeh - C.G.E. 86211 SN30A 2P; 11. circuit breaker - c.e.E. Fl TRP .460; JI. single ground outlet - c .e.E. 4094-2; KK. switch snap aetion - c.e.E. 5011-2.
outlet. This combination gave ±2°0 control from 64 to 127°0, below 64°0 control was within ±3.5°0. Reduction of steam pressure from 7.03 kg/cm 2 to 4.22 kg/cm 2 gave control of -+-1.5°0 throughout the mnge.
Testing Air distribution across the freezing coil and bed, adequate temperature control, quick pull down, electri cal, refrigeration and mechanical reliability, function and ease of 'Úperation were checked. Air distribution, air velocity and pressure drop were measured using either an anemotherm model 60 air meter 01' a J. Inst. Can. SeL Teehnol. AlIment. Vol. 7, No 4, 1974