Improving Boiler Room Efficiencies The Effect of …

1 Effect of Pressure on Steam Plant Operations01/02/01 Tech Paper #9161 Drawing Courtesy of Kewanee Boiler ManufacturingImproving Boiler room EfficienciesA Seminar on the ways and means of increasing Boiler room Effect of System PressureReduction in the Boiler PlantPresented byDavid C. FarthingRev 9/00 Effect of Pressure on Steam Plant Operations01/02/01 Tech Paper #9162 ContentsA MESSAGE FROM THE PLANT OPTIMIZATION & IT Boiler VS. FEEDWATER TABLES AT DESIGN Boiler OPERATING DISTRIBUTION OPERATING PLANT SYSTEM OF SYSTEM PRESSURE ON STEAM OF A 125 PSIG DESIGN OF 125 PSI DESIGN SYSTEM OPERATING AT 75 OF 125 PSI DESIGN SYSTEM OPERATING AT 105 THE of Pressure on Steam Plant Operations01/02/01 Tech Paper #9163A Message from the speakerEnergy costs today are the highest in recent history.

2 Gaining whatever efficienciesmay be found in thermal processes can help to stabilize the effects of rising s economic and environmental demands dictate that we get the greatestpractical Efficiencies from our plants. To do this we must have a basicunderstanding of what those Efficiencies are and how we may implement hope for you today is that you will leave this seminar with a clearer understandingof some of the economical and technically feasible opportunities you have toimprove your steam ,David C. FarthingIndustrial Sales ManagerFederal CorporationIntroductionImproved efficiency has many connotations, everything from fuel savings, improvedequipment operation and useful life span, to labor and manpower savings.

3 Thispaper will focus on the Effect of steam pressure reduction as a possible means ofthermal optimization and energy savings. The strategy presented will have bothtechnical and economic feasibility discussions presented with Plant Optimization & AutomationSteam plant optimization is the overall improvement of the plant s operation. Themost common strategies used to accomplish this task include, and generally focuson the improvement of primary equipment operating efficiency, fuel and energysavings. In heavy commercial and industrial Boiler applications these efficienciesare normally found in the application of waste heat recovery equipment, systemsand process automation, and improved operating of Pressure on Steam Plant Operations01/02/01 Tech Paper #9164 Keeping It CleanOne of the myths that need's to be cleared-up before we go forward is the Effect ofboiler and plant cleanliness on Improving efficiency.

4 Keeping Boiler furnace andwatersides clean does not improve efficiency. Keeping these surfaces cleanmaintains the factory delivered efficiency of the equipment. That is the efficiencyrating the equipment was designed to have. Allowing these surfaces to becomedirty or scaled lowers the original design efficiency, thus requiring more energy toaccomplish the same amount of can be seen in the chart below, a waterside scale build-up of .03 inch can resultin a 2% loss of efficiency. Increase the scale thickness to inch and you canexpect losses of 10% or greater.

5 David Farthing s TechStuff Rev The Effect of Scale & Soot Build-up on Heat Transfer in Boilers Conversely soot build-up in the furnace of .02 inch can result in as much as a 15%loss in thermal efficiency. Keeping these fireside and waterside surfaces in goodorder is paramount to efficient a clean plant lowers the risk of accidents and allows the operating staffmore efficient access to equipment and operating environments. It s just plaincommon sense and good practice. It is also the first place to look whenimplementing any thermal efficiency improvement Transfer Loss Due To Scale & Transfer MultiplyerSoot vs.

6 Heat vs. Heat TransferSoot ThicknessScale ThicknessEffect of Pressure on Steam Plant Operations01/02/01 Tech Paper #9165 Rating Boiler HorsepowerBoilers are rated from and at 212 degrees F and zero PSIG pressure. Additional Btuinput is required as steam pressure is increased. Operating pressure is a function of theend process s heat requirements and the piping restrictions of the distribution obvious consideration, being the overall cost of the distribution system during theoriginal installation. In the initial analysis it is normally less costly to lay-up a smallerdistribution line and run at elevated pressures, than a larger line which would allow theboiler to operate at a lower pressure.

7 The chart below shows the theoretical addition ofBtu required to increase steaming pressure based on feedwater vs. Feedwater Tables at Design PressureAdditional BTU Required to Develop 1 Boiler Horsepower vs. Feedwater Temperature FeedwaterBoiler Operating PressureTemperature025507510012515017520 0225250505,7667,6648,7339,49210,11310,63 111,07911,45911,83812,14912,4591004,0415 ,9397,0087,7678,3888,9069,3549,73410,113 10,42410,7341253,1795,0766,1466,9057,526 8,0438,4928,8719,2519,5619,8721502,3164, 2145,2836,0426,6637,1817,6298,0098,3888, 6999,0091751,4543,3514,4215,1805,8016,31 86,7677,1467,5267,8368,1472005912,4893,5 584,3174,9385,4565,9046,2846,6636,9747,2 842121772,0753,1443,9034,5245,0425,4905, 8706,2496,5606,8702251,6262,6963,4554,07 64,5935,0425,4215,8016,1116,4222301.

8 4542,5233,2823,9034,4214,8695,2495,6285, 9396,2492401,1092,1782,9373,5584,0764,52 44,9045,2835,5945,9042507641,8332,5923,2 133,7314,1794,5594,9385,2495,5592604191, 4882,2472,8683,3863,8344,2144,5934,9045, 214270741,1431,9022,5233,0413,4893,8694, 2484,5594,8692759711,7302,3512,8683,3173 ,6964,0764,3864,6972807981,5572,1782,696 3,1443,5243,9034,2144,524 David Farthing s TechStuff Rev The Effect of Feedwater Temperature on Boiler Output Determining Boiler Operating PressureAs previously mentioned, Boiler operating pressure is a function of the process s totalheat requirement and the restrictions in the distribution line.

9 Most firetube and watertubeboilers are designed to have discharge velocities less than 5,000 feet per minuet. Thislimitation is to prevent priming or carryover of the liquids in the water/steam separationdrum, which might occur at higher velocities. Carryover occurs when the surfacepressure at the water/steam interface is reduced below operating pressure by thenegative pressure Effect of accelerated velocities. The physical properties of thewater/steam interface dictate the Boiler s drum and discharge nozzle size at specificoperating pressures to maintain these velocity the Boiler operates outside of the limits the water/steam interface rises in level,thus reducing the surface area, which in turn increases the velocity Effect .

10 This onlyserves to amplify the problem and can result in the feedwater pumps failing to keep upwith feed demand due to very high amounts of of Pressure on Steam Plant Operations01/02/01 Tech Paper #9166 Determining Distribution Operating PressureDistribution Operating Pressure is a function of how much and how far. This is to say,how much heat energy is required at the end point and how far does it have to travel toget there. The heat energy available is in direct relationship to volume of steam andsteaming pressure. However, the issue we are concerned with in determining theoperating pressure of the distribution system is the volume of steam to be steam volume required to be transported from the Boiler to the point of use heavilyimpacts distribution operating pressure.