The wet feed solid material to a continuous dryer contains 40 wt% water on a wet basis (see hint), and is dried to 25 wt% (wet basis) by a counter-current air flow. The dried solid product leaves at the rate of 800 kg/h (dry solid+moisture). Fresh air to the system is at 26°C and has a humidity of 0.004 kg water/kg dry air. The moist air leaves the dryer at 35°C and humidity of 0.02 kg water/kg dry air. Part of this air is recirculated and mixed with the fresh air before entering the heater (See drawing below). The heated mixed air enter the dryer at 65°C and humidity of 0.010 kg water/kg dry air. The wet solid enters at 25°C and leaves at the same temperature (25°C). Calculate the mass flow rate of air recycled. Hint: Wet basis weight percent of water = [kg of water/(kg of water + kg of dry solid) ] x 100% Dry basis weight percent of water = [kg of water / kg of dry solid ] x 100%) (1) fresh air (3) heater recirculated air (6) (4) dryer dry solid X2, TS2 FIGURE 9.10-4. Process flow for air recirculation in drying. (2) (5) moist air wet solid X₁, TS1
The wet feed solid material to a continuous dryer contains 40 wt% water on a wet basis (see hint), and is dried to 25 wt% (wet basis) by a counter-current air flow. The dried solid product leaves at the rate of 800 kg/h (dry solid+moisture). Fresh air to the system is at 26°C and has a humidity of 0.004 kg water/kg dry air. The moist air leaves the dryer at 35°C and humidity of 0.02 kg water/kg dry air. Part of this air is recirculated and mixed with the fresh air before entering the heater (See drawing below). The heated mixed air enter the dryer at 65°C and humidity of 0.010 kg water/kg dry air. The wet solid enters at 25°C and leaves at the same temperature (25°C). Calculate the mass flow rate of air recycled. Hint: Wet basis weight percent of water = [kg of water/(kg of water + kg of dry solid) ] x 100% Dry basis weight percent of water = [kg of water / kg of dry solid ] x 100%) (1) fresh air (3) heater recirculated air (6) (4) dryer dry solid X2, TS2 FIGURE 9.10-4. Process flow for air recirculation in drying. (2) (5) moist air wet solid X₁, TS1
Introduction to Chemical Engineering Thermodynamics
8th Edition
ISBN:9781259696527
Author:J.M. Smith Termodinamica en ingenieria quimica, Hendrick C Van Ness, Michael Abbott, Mark Swihart
Publisher:J.M. Smith Termodinamica en ingenieria quimica, Hendrick C Van Ness, Michael Abbott, Mark Swihart
Chapter1: Introduction
Section: Chapter Questions
Problem 1.1P
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Question
![The wet feed solid material to a continuous dryer contains 40 wt% water on a wet basis (see hint) and is dried to 25 wt%
(wet basis) by a counter-current air flow. The dried solid product leaves at the rate of 800 kg/h (dry solid+moisture). Fresh
air to the system is at 26°C and has a humidity of 0.004 kg water/kg dry air. The moist air leaves the dryer at 35°C and
humidity of 0.02 kg water/kg dry air. Part of this air is recirculated and mixed with the fresh air before entering the heater
(See drawing below). The heated mixed air enter the dryer at 65°C and humidity of 0.010 kg water/kg dry air. The wet
solid enters at 25°C and leaves at the same temperature (25°C). Calculate the mass flow rate of air recycled.
Hint:
Wet basis weight percent of water = [kg of water / (kg of water + kg of dry solid) ] x 100%
Dry basis weight percent of water = [kg of water/ kg of dry solid ] x 100%)
(1)
fresh
air
(3)
heater
recirculated air (6)
c
dryer
dry solid
X2, TS2
FIGURE 9.10-4. Process flow for air recirculation in drying.
(2)
(5)
moist
air
wet solid
X₁, TS1](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2Ff24f314d-65d6-495f-a371-db467effc487%2F92f4ecd9-8820-471a-89c9-197bd59262aa%2F1od5df_processed.jpeg&w=3840&q=75)
Transcribed Image Text:The wet feed solid material to a continuous dryer contains 40 wt% water on a wet basis (see hint) and is dried to 25 wt%
(wet basis) by a counter-current air flow. The dried solid product leaves at the rate of 800 kg/h (dry solid+moisture). Fresh
air to the system is at 26°C and has a humidity of 0.004 kg water/kg dry air. The moist air leaves the dryer at 35°C and
humidity of 0.02 kg water/kg dry air. Part of this air is recirculated and mixed with the fresh air before entering the heater
(See drawing below). The heated mixed air enter the dryer at 65°C and humidity of 0.010 kg water/kg dry air. The wet
solid enters at 25°C and leaves at the same temperature (25°C). Calculate the mass flow rate of air recycled.
Hint:
Wet basis weight percent of water = [kg of water / (kg of water + kg of dry solid) ] x 100%
Dry basis weight percent of water = [kg of water/ kg of dry solid ] x 100%)
(1)
fresh
air
(3)
heater
recirculated air (6)
c
dryer
dry solid
X2, TS2
FIGURE 9.10-4. Process flow for air recirculation in drying.
(2)
(5)
moist
air
wet solid
X₁, TS1
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