Question

3-9. 10,000 kg / h of a 20% NaOH solution are treated in a simple evaporator and must be concentrated to 50% by weight. The steam used as the heating medium is saturated steam at 4 at overpressure. An absolute pressure of 150 mm Hg is maintained in the evaporation chamber. The integral coefficient of heat transmission is 2,500 Kcal / m2.h.C. If the supply enters the evaporator at 20 ° C, calculate: a) The heating surface. b) The hourly consumption of heating steam. c) The economy.

Answer 1

Sol 10,000 Igino of a 20% naon Solution are treared in a simple evaporator and must be 50% Concentrared by weight +V) waren F = feed flow rare (Kg/ho) vapor T S = Steam rave (Kylho) feed To a temperature of feed (XF)=0.2 TS = temperature of steam Steam T= temperature maintained in the evaporation Productle] FGTF STS Chamber. Xp=0.5 Overall Balance, If= utp overall Solid balance F XF = P Xp 10,000 X 0.2 - PX 0.5 P= 4000 kg ihr Va 10,000 -4,000 = boookalho By using steam table Saturated steam Payam or u.ou bar TS = 152.236°C latent hear of steam (ds) = 2106.67 kJ l kg

and at P= 150mming immung = 133.322 Pa 19998.3 Pa P= 150 x 133.322 Pa Or Iban 10 15 a 0.20 bar P= 0.199 Now, 4.09 KJlKg.K Solution T= 105.099°C larent hear of steam (av) = 2242.92 KJ 1 kg Cof thear capacity) of Moon ot 206 = TE = 20°C Now, overall enegy balance, Sasa F CPF (T-Tf ) tva SX 2106.67 = 10,000 x 4.01 (1056099-20) 16000 x 2242.92) 2007.894 kg lho S = . 3412469.9+ 13457520 2106.67 a) The healing surface Sds = UA (AT) = UA(TS-TJ] Us 2500kcal imen.c Tekcal 24.10у ҚT U- (2500 X40184 ) KJ im. hic U= 10460 KJ l minic (2009.894 x 2106.67) = 10460 LAI (152.236-105.0991 A - 8007.894 X 2106.67 340215 mp 493053.02 heating supace area = 34.215 me

hourly of h b) the consumption Ś= 8007.094 Kglihr heating steam ( ) the econo conomy Ig of water vaporised (w) - kg of steam used (s] + economy GOOO -0.749 p007.894 economy of evaporator co.749