Question

In the Bayer process for refining alumina the initial stage is to dissolve the Al203 out of the bauxite using hot caustic soda. The dissolution process takes place in a series of vertical vessels known as digesters. In the single stream process, saturated steam is injected into the caustic soda/bauxite slurry in the first digester as shown below. Saturated steam Bauxite in caustic soda slury 25-C Flow rate-350uh Bauxite slury 130-c The slurry is heated from 25°C to 130°C at the rate of 350 t/h. The slurry has a specific heat capacity of 2.66 kJ/kg.K. a) Calculate the heat required in kW to heat the slurry from 35 to 130°C. [3] b) What is the minimum supply temperature and gauge pressure in kPa of the steam required to provide the heat? [2] c) Assuming no heat loss, how much steam in tonne/hour is required to heat the slurry? [2] d) What should be the design pressure for the digester? [1]

Answer 1

Cnive n Ps peeties T 25 , 126°c, ウ= 350tん 9 7-2 ドJc T2: CP 2-66 K Heat Reguivd AT Te-TIAT / 30-25 Jorc O097 2 X 2 66 x10 5 ニ 27,147.96 KW b.) final temp fr the STuery 130 c We hailalur nby PInons (30 4emp Stam Steam for bettel Amd ute Sa turate We design wit provide Latemt heat Tem b Min 2)ro: find from steam table Min Pressurs ニ 16893ヒPa. for gatrated steam at 13 3ec 16Q.93 KPa at From paut b we Cam Read teble Steam 2174 Latent heat -1 27,147.96とW We nead 27,147.9くKI1/ 0 Msteam KC 2174 36 tonhel

AS are We Steam for heatina teake we Can desijn pressuee timet 1. 18 5.13 k T&73 1l (nanse are au prresures 0 1k