Chemical Processing - July 2008 - (Page 30) the condensate pot corresponds to the bottom of the exchanger. If the condensate pot level is above the bottom of the exchanger, the exchanger can’t be completely drained of condensate. If the condensate pot level is exactly at the bottom of the exchanger, there would be no hydrostatic head for condensate f low when the exchanger is completely drained of condensate (and the condensate f low is at its maximum). As the condensate pot level is dropped further below the bottom of the exchanger, the hydrostatic head for f luid f low increases — but this also raises the possibility for windup in the liquid outlet temperature controller. Windup can’t occur if the control valve is either perfectly sized or undersized. However, as previously noted, most valves are oversized at least to some degree. In this case, an additional consequence of oversizing the valve is the possibility of windup in the liquid outlet temperature controller. This is another case where the windup prevention mechanisms as customarily configured in digital systems are ineffective. Figure 6 indicates that the upper output limit could be set at 78% (for an equal-percentage valve) but this value is neither precise nor constant. Instead, the windup prevention should be invoked at the instant the condensate is completely drained from the exchanger. Detecting this requires additional instrumentation (such as a level switch) to provide the necessary information so the system can properly initiate its windup protection mechanisms. In large production facilities where multiple exchangers can be physically located within a reasonable proximity, condensate pots are commonly installed to address the condensate return issues. (Installing a condensate pot for an individual exchanger is difficult to justify.) There are competing designs for condensate pot arrangements but in most the pressure in the condensate pot is the steam supply pressure and the condensate flows from the exchangers to the condensate pot by gravity. CeCil l. Smith is president of Cecil L. Smith, Inc., Baton Rouge, La. E-mail him at cecilsmith@cox.net. http://www.sulzerchemtech.com http://www.sulzerchemtech.com
Table of Contents Feed for the Digital Edition of Chemical Processing - July 2008 Chemical Processing - July 2008 Contents From the Editor ChemicalProcessing.com Field Notes In Process Energy Saver Compliance Advisor Who’s a Big Hit? Succeed with Condensate Control Take Some Basic Steps with pH Measurements Steam Projects Provide Fast Payback Process Puzzler Plant InSites Equipment & Services Product Spotlight/Classifieds/Ad-Lits Ad Index End Point Chemical Processing - July 2008 Chemical Processing - July 2008 - Chemical Processing - July 2008 (Page Cover1) Chemical Processing - July 2008 - Chemical Processing - July 2008 (Page Cover2) Chemical Processing - July 2008 - Chemical Processing - July 2008 (Page 3) Chemical Processing - July 2008 - Chemical Processing - July 2008 (Page 4) Chemical Processing - July 2008 - Contents (Page 5) Chemical Processing - July 2008 - Contents (Page 6) Chemical Processing - July 2008 - From the Editor (Page 7) Chemical Processing - July 2008 - From the Editor (Page 8) Chemical Processing - July 2008 - ChemicalProcessing.com (Page 9) Chemical Processing - July 2008 - ChemicalProcessing.com (Page 10) Chemical Processing - July 2008 - Field Notes (Page 11) Chemical Processing - July 2008 - In Process (Page 12) Chemical Processing - July 2008 - In Process (Page 13) Chemical Processing - July 2008 - In Process (Page 14) Chemical Processing - July 2008 - Energy Saver (Page 15) Chemical Processing - July 2008 - Energy Saver (Page 16) Chemical Processing - July 2008 - Compliance Advisor (Page 17) Chemical Processing - July 2008 - Who’s a Big Hit? (Page 18) Chemical Processing - July 2008 - Who’s a Big Hit? (Page 19) Chemical Processing - July 2008 - Who’s a Big Hit? (Page 20) Chemical Processing - July 2008 - Who’s a Big Hit? (Page 21) Chemical Processing - July 2008 - Who’s a Big Hit? (Page 22) Chemical Processing - July 2008 - Who’s a Big Hit? (Page 23) Chemical Processing - July 2008 - Succeed with Condensate Control (Page 24) Chemical Processing - July 2008 - Succeed with Condensate Control (Page 25) Chemical Processing - July 2008 - Succeed with Condensate Control (Page 26) Chemical Processing - July 2008 - Succeed with Condensate Control (Page 27) Chemical Processing - July 2008 - Succeed with Condensate Control (Page 28) Chemical Processing - July 2008 - Succeed with Condensate Control (Page 29) Chemical Processing - July 2008 - Succeed with Condensate Control (Page 30) Chemical Processing - July 2008 - Succeed with Condensate Control (Page 31) Chemical Processing - July 2008 - Take Some Basic Steps with pH Measurements (Page 32) Chemical Processing - July 2008 - Take Some Basic Steps with pH Measurements (Page 33) Chemical Processing - July 2008 - Take Some Basic Steps with pH Measurements (Page 34) Chemical Processing - July 2008 - Take Some Basic Steps with pH Measurements (Page 35) Chemical Processing - July 2008 - Take Some Basic Steps with pH Measurements (Page 36) Chemical Processing - July 2008 - Take Some Basic Steps with pH Measurements (Page 37) Chemical Processing - July 2008 - Take Some Basic Steps with pH Measurements (Page 38) Chemical Processing - July 2008 - Steam Projects Provide Fast Payback (Page 39) Chemical Processing - July 2008 - Steam Projects Provide Fast Payback (Page 40) Chemical Processing - July 2008 - Process Puzzler (Page 41) Chemical Processing - July 2008 - Plant InSites (Page 42) Chemical Processing - July 2008 - Plant InSites (Page 43) Chemical Processing - July 2008 - Equipment & Services (Page 44) Chemical Processing - July 2008 - Equipment & Services (Page 45) Chemical Processing - July 2008 - Product Spotlight/Classifieds/Ad-Lits (Page 46) Chemical Processing - July 2008 - Product Spotlight/Classifieds/Ad-Lits (Page 47) Chemical Processing - July 2008 - Product Spotlight/Classifieds/Ad-Lits (Page 48) Chemical Processing - July 2008 - Ad Index (Page 49) Chemical Processing - July 2008 - End Point (Page 50) Chemical Processing - July 2008 - End Point (Page Cover3) Chemical Processing - July 2008 - End Point (Page Cover4)
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