The most common of the available methods is to use the vapour generated in the first evaporator as the heating medium for a second evaporator. 2. Determine the total amount of vapor evaporated by performing an overall material balance. In any evaporation operation, the major process cost is the steam consumed. K. If each effect has the same surface area, calculate the area, the steam rate used, and the steam economy. The amount of heat required to raise the temperature of a substance can be expressed as: Imperial Units? 0000012001 00000 n
%PDF-1.4
%����
Saturated steam at 205.5 kPa (121.1°C saturation temperature) is being used. If these areas are reasonably close to each other, the calculations are complete and a second trail is not needed. 4. 0
0000001471 00000 n
Proper utilization of steam helps in saving in the input cost of water and coal. Then calculate the boiling point in each effect. Calculate the amount vaporized and the flows of liquid in each effect using heat and material balance in each effect, Calculate the value of heat transferred in each effect. 396 0 obj
<>stream
In this way the amount of vapour (kg) produced, In addition to the economy increase in multiple-effect evaporation, a capacity variation would be expected. 0000003051 00000 n
Steam consumed and steam utilized at the point of application are not equal. The amount of steam consumption in multiple effect evaporators is already mentioned in Lesson 4. The same principle will work for subsequent calandrias and last calandria will correspond to condenser vacuum. 3. The rate of condensation of steam during the warm-up period is maximum. Calculation of steam consumption in a pipe during the start-up operation and normal continuous operation is possible, and will be discussed in detail below. 0000002431 00000 n
Increasing ΔT1 and lowering ΔT2 and ΔT3 proportionately as a first estimate, ΔT1 = 15.56oC , ΔT2 = 18.34oC , ΔT3 = 32.07oC. Lesson 3. Saving of each kg of steam is directly proportional to the saving of some percentage of water, coal and electricity. Calculate the value of heat transferred in each effect. 2. qt = U1 A1 ∆t1 + U2 A2 ∆ t2 + U3 A 3 ∆ t3 + ………. The increased steam economy must then, be balanced against the increased equipment cost. 5.2.3 Calculations for multiple- effect evaporators, For a multiple – effect evaporator system calculations, the values required to be obtained are. 0000010185 00000 n
Since the areas and heat transfer coefficients are equal, qt = U1 A1 (∆ t1 + ∆ t2 + ∆ t 3 …….) Several evaporators can be connected in series. 0000010039 00000 n
Thus results in the following benefits: Process plant running load is the steam load which is related to the normal (full load) continuous load of the plant. The heat of milk is considered to be negligible. Feed = 3000 Kg/hr, feed temperature = 30 DegC, Intial TDS = 5%, Final TDS = 30%, available steam pressure for TVR = 6.5 Kg/Cm2, Initial total COD = 70000 ppm, what will be final distillate TDS and COD? Note, however, that the temperature difference from initial steam to the final condenser which was available for a single-effect evaporator will be unchanged by inserting any additional effects between the steam supply and the condenser. For 13.4 kPa, the saturation temperature is 51.67oC from the steam tables. Following the above steps outlined, the calculations are as follows, 1. We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites. The increase in latent heat with decreasing pressure and additional radiation losses affect , the economy as the number of evaporators used is increased. &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;!-- /* Font Definitions */ @font-face {font-family:Shruti; panose-1:2 0 5 0 0 0 0 0 0 0; mso-font-charset:1; mso-generic-font-family:auto; mso-font-pitch:variable; mso-font-signature:262144 0 0 0 0 0;} @font-face {font-family:&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;Cambria Math&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;; panose-1:2 4 5 3 5 4 6 3 2 4; mso-font-charset:0; mso-generic-font-family:roman; mso-font-pitch:variable; mso-font-signature:-1610611985 1107304683 0 0 159 0;} @font-face {font-family:Calibri; panose-1:2 15 5 2 2 2 4 3 2 4; mso-font-charset:0; mso-generic-font-family:swiss; mso-font-pitch:variable; mso-font-signature:-1610611985 1073750139 0 0 159 0;} /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-unhide:no; mso-style-qformat:yes; mso-style-parent:&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;; margin-top:0in; margin-right:0in; margin-bottom:10.0pt; margin-left:0in; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;Calibri&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;,&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;sans-serif&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;; mso-fareast-font-family:&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;Times New Roman&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;; mso-bidi-font-family:Shruti;} p.MsoHeader, li.MsoHeader, div.MsoHeader {mso-style-priority:99; mso-style-link:&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;Header Char&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;; margin-top:0in; margin-right:0in; margin-bottom:10.0pt; margin-left:0in; line-height:115%; mso-pagination:widow-orphan; tab-stops:center 3.25in right 6.5in; font-size:11.0pt; font-family:&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;Calibri&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;,&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;sans-serif&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;; mso-fareast-font-family:&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;Times New Roman&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;; mso-bidi-font-family:Shruti;} span.HeaderChar {mso-style-name:&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;Header Char&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;; mso-style-priority:99; mso-style-unhide:no; mso-style-locked:yes; mso-style-link:Header; mso-ansi-font-size:11.0pt; mso-bidi-font-size:11.0pt;} .MsoChpDefault {mso-style-type:export-only; mso-default-props:yes; font-size:10.0pt; mso-ansi-font-size:10.0pt; mso-bidi-font-size:10.0pt; mso-ascii-font-family:Calibri; mso-hansi-font-family:Calibri; mso-bidi-font-family:Shruti;} @page Section1 {size:8.5in 11.0in; margin:1.0in 1.0in 1.0in 1.0in; mso-header-margin:.5in; mso-footer-margin:.5in; mso-paper-source:0;} div.Section1 {page:Section1;} --&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt; Module 1. (1) F = 22 680 = V1 + L1 = 6048 + L1, L1 = 16 632 kg/h, (2) L1= 16 632 = V2 + L2 = 6048 + L2, L2 = 10 584 kg/h, (3) L2= 10 584 = V3 + L3 = 6048 + L3, L3 = 4536 kg/h. Multiple effect evaporator is used for steam economy. The area of the heating surface in each effect, The kg of steam per hour to be supplied, and. During the plant start-up after a long time or from cold, then the steam is required to heat the system uniformly to bring the system close to the normal working temperature of the system. 0000069522 00000 n
Step 3. Normally steam consumed or generated in a steam boiler is more than what is required for use at the point of application. To find W, find the mass of the various steam main items from Table 1. 0000004343 00000 n
When steam condenses on the wall of an exposed/uninsulated steam pipe, it gives up its enthalpy of evaporation. By controlling the opening of orifice plates present in the airline of heating jackets is also used to control different vacuum levels in all the calandrias. It therefore follows that the steam consumption can be determined from the heat transfer rate and vice-versa, from Equation 2.6.3. Since the main valve is far bigger in size (designed for full flow requirement) and not appropriate to use for small flow during the warm-up period. 0000006605 00000 n
The feed rate is 22680 kg / h at 26.7, C. The heat capacity of the milk is (K1) C, 4.19 – 2.35x kJ/kg.K. = U1 A1 ( ∆ t) total. Step 1. Using the equation for BPR for evaporator number 3 with x = 0.5, BPR3 = 1.78x+6.22x2 = 1.78(0.5)+6.22(0.5)2 = 2.45 oC, so T3 = 51.67+2.45 = 54.12 oC. The rate of condensation of steam needs to be taken into account for sizing the steam traps, and also in finalizing the boiler output. 0000000016 00000 n
0000001650 00000 n
0000001194 00000 n
Therefore, methods of reducing steam consumption (or of increasing economy, defined as mass of vapour produced per unit mass of steam consumed) are very important. It gives less condensation of vapour in second calandria. Heat transfer area oTemperature of condensing steam = 134 C. (i) The area of the heating surface in each effect, (ii) The kg of steam per hour to be supplied, and. 5.2.2 Multiple effect Evaporator capacity and steam economy. startxref
The pressure in the vapor space of the third effect is 13.4 kPa. In flow type applications the product or fluid is heated when it constantly flows over … the amount of vapour leaving each effect, particularly in the last one. Steam consumption within the pipe system needs to be judiciously monitored and controlled. The BPR in each effect is calculated as follows: (1) BPR1 = 1.78 x1 + 6.22(x1)2 = 6.22(0.136)2 = 0.36oC, (2) BPR2 = 1.78(0.214) + 6.22(0.214)2 = 0.65oC, (3) BPR3 = 1.78(0.5) + 6.22(0.5)2 = 2.45oC, Σ ΔT available = Ts1 – T3 (saturation) – (BPR1 + BPR 2 + BPR 3), ΔT1 = 12.40 oC similarly ΔT2 = 19.50oC and ΔT3 = 34.07oC. The most common of the available methods is to use the vapour generated in the first evaporator as the heating medium for a second evaporator. Estimate the temperature drops ∆T1, ∆T2 and ∆T3 in the three effects. Step 2. Determine the total amount of vapor evaporated by performing an overall material balance. When the solution being evaporated has a significant boiling-point rise, the capacity obtained is very much reduced, for the boiling-point rise reduces the ∆t in each effect.