Assuming equal amount vaporized in each effect, V1 = V2 = V3 =6048 kg/h. 5.2.4 Triple-effect evaporators’ calculation method. Lesson 5. Multiple Effect (3) Evaporator Steam Consumption Calculation - posted in Process Heat Transfer: Hi friends, I would like to calculate the multilple 3 effect evaporator steam consumption. CARE AND MAINTENANCE OF EVAPORATORS, Last modified: Thursday, 4 October 2012, 10:25 AM, BASIC CONCEPTS OF MULTIPLE EFFECT EVAPORATORS. (6) Overall heat – transfer coefficients in each effect. Method to calculate the warm-up condensing load for a period of 30 minutes in a steam system. qt = U1 A1 ∆t1 + U2 A2 ∆ t2 + U3 A 3 ∆ t3 + ………. Step 1. Several evaporators can be connected in series. 0000010185 00000 n A good practice is to warm-up the system very slowly for safety-reasons, pipes have the benefit of reduced thermal and mechanical stress. The rate of condensation of steam needs to be taken into account for sizing the steam traps, and also in finalizing the boiler output. 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. The ‘warm-up load’ is the steam load which is associated with the steam consumption during the start-up of the plant. 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. As shown in figure1 above, before the main valve/bypass valve separator is installed to ensure that steam passing through the valve should be dry to protect the valve wear and tear. The method is feasible if the second evaporator is operated at a lower pressure than the first, so that a positive value of ∆t is obtained across the steam-chest surface of the second evaporator. The time required to warm up the pipe network decides the warm-up (bypass) valve size. trailer Fig_5.1.SWF, 5.2.1 Different level of vacuum in each effect of multiple effect evaporator. Determine the boiling point in the last effect from the known outlet concentration and pressure in the last effect. %PDF-1.4 %���� (4) Final concentration in the liquid leaving the last effect, (5) Physical properties such as enthalpies and / or heat capacities of the liquid and vapours, and. 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. The calculations are done using material balances, heat balances, and the capacity equations q = UA∆T for each effect. So in that calandria milk initially will be heated and then raised to corresponding boiling point and vapour will be released. 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. Usually, the areas of each effect are assumed equal. 5. The result is that the evaporation using more than five or seven effects is rarely economical. A convenient way to solve these equations is by trial and error. The basic steps to follow are given as follows for a triple – effect evaporators. The method is feasible if the second evaporator is operated at a lower pressure than the first, so that a positive value of ∆t is obtained across the steam-chest surface of the second evaporator. The boiling point rise of the milk (independent of pressure) can be estimated from BPR°C = 1.78x + 6.22x, , where x is weight fraction of T.S. It gives less condensation of vapour in second calandria. Making an overall and a solids balance to calculate the total amount vaporized (V1+V2+V3) and L3, Assuming equal amount vaporized in each effect, V, Making a solids balance on effects 1, 2 and 3 and solving for. Multiple effect evaporator is used for steam economy. Estimate the temperature drops ∆T1, ∆T2 and ∆T3 in the three effects. Making an overall and a solids balance to calculate the total amount vaporized (V1+V2+V3) and L3, FxF = 22680(0.1) = L3 (0.5) + (V1+V2+V3) (0). For the simplest case, where each effect has area and coefficient equal to that of every other effect and where there are no boiling point rises q. 2. 0000001650 00000 n 0000005567 00000 n BASIC PRINCIPLES OF EVAPORATORS, Lesson 2. The area of the heating surface in each effect, The kg of steam per hour to be supplied, and. This gives rise of back pressure in first calandria tube and thereby the boiling point in first calandria will rise. If the warm-up/heating time of the system is increased to say 24 minutes, then the initial steam flow rate for heating can be reduced further. To find W, find the mass of the various steam main items from Table 1. Steam condensation when it travels on its way to point of use mainly due to exposed surfaces. Thus, multiple-effect evaporation using n effects increases the steam economy but decreases the heat flux per effect by a factor of about 1/n relative to single-effect operation under the same terminal conditions. Lesson 6. The rate of condensation of steam during the full load running a load of the plant is minimum. Determine the boiling point in the last effect from the known outlet concentration and pressure in the last effect. startxref In addition to the economy increase in multiple-effect evaporation, a capacity variation would be expected. (Supervisory Control and Data Acquisition), Programmable Logic Controllers (PLCs): Basics, Types & Applications, Diode: Definition, Symbol, and Types of Diodes, Thermistor: Definition, Uses & How They Work, Half Wave Rectifier Circuit Diagram & Working Principle, Lenz’s Law of Electromagnetic Induction: Definition & Formula. Without the thermocompressor, the specific steam consumption would be approx. 2. Making a solids balance on effects 1, 2 and 3 and solving for x, (1) 22 680(0.1) = L1x1 = 16 632 (x1), x1 = 0.136, (2) 16 632(0.136) = L2x2 = 10 584 (x2), x2 = 0.214, (3) 10 584(0.214) = L3x3 = 4536 (x3), x3 = 0.50. 0000006605 00000 n Full disclaimer here. Saving of each kg of steam is directly proportional to the saving of … The pressure in the vapor space of the third effect is 13.4 kPa. 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. For the simplest case, where each effect has area and coefficient equal to that of every other effect and where there are no boiling point rises qt = q1 + q2+ q3 + …………..where qt is the total heat-transfer rate in all effects and q1, q2, q3 are the heat transfer rates in each of the individual effects. 0000003051 00000 n &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. This vapour is going in the next calandria’s heating jacket where the milk is cold and nowstart heating thereby the temperature difference between heating vapour and milk will decrease. xref 376 0 obj <> endobj If these areas are reasonably close to each other, the calculations are complete and a second trail is not needed. The difference in steam consumption and steam utilization is due to: When steam condenses on the wall of an exposed/uninsulated steam pipe, it gives up its enthalpy of evaporation. The amount of steam consumption in multiple effect evaporators is already mentioned in Lesson 4. 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.
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