Presentation on theme: "Process Heating – Temperature Stability Under Dynamic Flow Rates Direct Steam Injection for Sustainability David Degelau Hydro-Thermal Corp Certified Steam."— Presentation transcript:
1 Process Heating – Temperature Stability Under Dynamic Flow Rates Direct Steam Injection for SustainabilityDavid DegelauHydro-Thermal CorpCertified Steam System Specialist
2 Presentation Summary Industrial heating methods Direct steam injection (DSI) basicsInherent properties for sustainabilityCase Studies -Thanks to all of you for the opportunity to speak with you regarding direct steam injection this afternoon. I’ll begin with presenting the basics of direct verses indirect heating using conventional sludge heat exchangers as a reference point for presenting the benefits of DSI.I’ll review internal modulation verses external modulation.Cover the advantages of DSI using hot water heat exchangers as a reference point.I’ll show various digestion heating flow schemes using DSI.Present typical DSI heater dimensions and installations.Followed by specific digester benefits that can be realized with DSI and conclude with a summary and questions and answers.
3 Industrial Heating Methods Direct and Indirect Steam Heating
4 Indirect or Direct Heating Steam inCold Liquid InWarm outThis chapter discusses the difference between direct and indirect steam heating of fluids.Indirect heating is most commonly seen in the form of plate & frame or shell & tube heat exchangers.Heat exchangers inefficiently transfer heat through a membrane. This results in only ~ 83% of the heat energy transferred to the process fluid while the remaining energy is discharged in the form of condensate.DSI uses 100% of the steam’s heat energy by adding steam directly to the process fluid.The primary benefits of Direct contact heating vs Indirect includeEnergy savings of 25% or more.Precise and instantaneous temperature control is possible to within 1 degree FNo production floor space is requiredReduces maintenance via self cleaning and elimination of a condensate return systemCold liquid inHot condensate out
5 Direct Fluid Heating - Sparging Oldest method of direct steam injectionVery inefficientProne to tank failureLimited temperature controlHigh maintenance costsAs we have already discussed the difference between direct and indirect heating, I’d like to discuss other forms of direct steam injection.Sparging is the oldest, simplest and least complicated technique for mixing steam with liquid or slurry to effect heating. It is basically injecting steam directly into a fluid filled tank. Though considered simple and inexpensive, sparging is very inefficient and the operation invariably results in:Poor heat injection economics due to steam energy escaping from vessels without condensing.Equipment failure (both vessel and sparger pipes) due to the vibration associated with steam hammer when not operated within their narrow design envelope.Usually less than satisfactory on/off process control. A sparger is the least controllable DSI heating method.High maintenance costs for tanks, sensors and piping are the norm if the equipment operates outside the design parameters.
6 Common Sparging Problems Steam HammerSteam bubbles present in pipeBubbles combine and growBubbles contact cool pipe wall and collapseWater rushes into void at high velocityOverheated zone around sparge nozzleSteam bubbles in pipe may damage tankSteam bubbles may escape into atmosphereStart with sparging nozzle, discuss how they are supposed to work. Breaking up steam into relatively small bubbles.Bubbles are still relatively large.As temperature demand drops, pressure drops, potentially causing instability.Bubbles can be present if liquid is hot, or not miscible with steamStartups can be rough since liquid can back up to steam valve.Tanks:Overheated Zone around nozzleAs tank heats, Heat transfer slowsSteam may escape to atmosphereAgitation very important
7 Direct Fluid Heating – Mixing Tees Very high maintenanceProne to scaling and foulingSteam hammer commonPotentially very dangerousLimited temperature controlMixing Ts combine separate streams of steam and cold water to produce heated water. Because accurate temperature control is difficult to maintain with this method, mixing Ts are not the best choice for process fluids. When used for water, mixing tees are prone to scaling, fouling and excessive hammer. Due to the plugging, scaling and fouling, mixing tees can also be very dangerous if live steam flows through the hoses.
8 Direct Fluid Heating – Sparge Tube TMPerforated tube spargerRequires external steam control valveVery high maintenanceProne to scaling and foulingSteam hammer commonLimited temperature control due to external controlInternal spring prone to breakageCommonly known as the Pick heater, the modulatable sparger tube (MST) heater consists of a spring controlled, variable-injection sparger tube inside a cast process flow body. In response to a temperature sensor, the external flow control valve modulates the steam to a spring-loaded piston. MST heaters work reasonably well on clear liquids and some low solids solutions but are subject to severe clogging and steam hammer if frequent maintenance is not performed. In typical water heating applications, these devices typically require monthly tear down and acid bath cleaning. Since the steam flow is dependent upon a spring loaded valve, accurate temperature control is difficult once the spring begins to wear. Spring failure is a common issue with this type of heater.
10 Contrast: Heat Exchanger vs. DSI Indirect vs. DirectIndirect = heat transfer only; no fluid mixingSteam in(Hot)WarmoutCold LiquidinHot Condensate
11 DSI AdvantagesRapid and uniform heating—important in starches and food productsCan heat highly viscous fluidsHandles fluids that are difficult to heat—avoids “bake-on”; abrasive slurriesCompact footprintMinimizes plugging and foulingRapid response time
12 Energy Losses in the Heating Process WaterTreatmentMakeup waterProcess FluidHXTrap systemBoilerBlow Down lossesCondensate lossesStack lossesFlash lossesHeat lossSteamEnergy losses in a typical systemStack losses: 10-30% of energy inputBlow down losses – 5-10% of boiler outputCondensate losses due to leaks or non functioning trap systems – up to 10% of energy inputFlash losses – 5-10% depending on system pressures as hot condensate is reduced in pressureCondensate heat losses < 2% of energy inputPump power
13 Maintenance – Steam Systems WaterTreatmentSlurryHXTrap systemBoilerCondensate returnBlow DownMakeup waterAll Boilers require water treatment systems to produce soft treated water. Salt, chemicals and water quality must be added and monitored.A portion of the boiler contents must be purged periodically to remove sediment and maintain efficienciesTypically 5-10% of the output volume is discharged in this manner. In DSI systems output is usually 2-5% less.Steam based heat exchangers have a boiler and condensate return system that must be maintained. These systems drop the water pressure and temperature below the boiling point.They are often prone to failure due to plugging and scale buildup.A well-maintained steam system will typically experience a 10% trap failure in a 1-year period. This can translate into significantlosses to the system.System debris, improper sizing, and improper application are common causes of steam trap failure. Steam trapscan fail in different modes. Two main failure modes result in significant economic impact. Afailed-open steam trap allows “live” steam to discharge from the system, a steam leak. Steamtraps may also fail closed, which allows condensate to backup into the equipment drained by thetrap. If this is a process heat exchanger, the product will not receive the energy intended. Waterhammer can also result, which can damage piping components.* Steam Survey, 2002 Greg Harrell, Ph.D., P.E. US Dept. of Energy
14 Internal Modulation Steam Inlet Steam Velocity ~1500 ft/sec Full Steam Pressure(Psteam)High VelocitySteam JetSteam NozzleCombining tubeStem / PlugHot Liquid DischargeSteam InletLiquid InletSteam Velocity~1500 ft/secThe hydro heater uses patented internal steam modulation bringing full steam pressure to point of injection.This allows 0-100% adjustment control with complete stability. Other advantages include sonic velocity steam for self cleaning, proper mixing and no need for costly external modulation or control valves. Our K and M series models feature a manual or automatically adjustable combining tube to shear, ribbonize and control the slurry and ensure complete cooking of the process fluid. This eliminates hammering, noise and ensures a complete and consistent cooking process.Patented internal modulation DSI unit
15 Contrast: Sparging vs. DSI Paper mill – actual dataReduced steam usage by 33%932 lbs (422 Kg) with spargers624 lbs (283 Kg) with DSITime SavingsDaily production increased by 32%
16 Maximum Boiler Energy Efficiency 100% efficient use of steam heat energyReduced steam consumptionLess energy required at boiler25% - 30% reduction is commonLower energy costsDirect Steam Injection heating technology is extremely energy efficient and can represent a significant part of a business’ energy reduction and sustainability initiatives. DSI systems transfer 100% of steam’s sensible and latent energy to the fluid to be heated. This reduces the amount of steam necessary which in turn lowers the energy requirement at the boiler. In fact, when comparing to a shell & tube or plate & frame style heat exchanger, DSI systems are typically 25-30% more efficient. With energy costs unstable at best and continuing to rise, many of our customers are realizing annual savings in the hundreds of thousands.rev 3.09
17 Energy Comparison Report Process fluid to be heatedProcess flow rateIncoming temperatureDesired temperature at outputAvailable steam pressure% of condensate returned to the boilerBoiler makeup water temperatureHours per day in useBoiler fuel cost per million BtuIf you are using heat exchangers and would like to know how much a DSI system can reduce your energy costs, please gather as much information as you can about your specific operating parameters and check with a direct steam injection engineer.
18 ENERGY Calculator Process fluid type In/out temperature Process flow rateHours per day in useSteam pressure% condensate returnedBoiler makeup water temperatureBoiler fuel cost per million BTUEnergy.gov
19 Precise Temperature Control = Efficiency Poor Temp ControlTight Temp ControlTight temperature control results in Lower set-pointBeyond the achievable energy savings demonstrated in the ROI calculator, there are additional, inherent advantages of using direct steam injection compared to a heat exchanger.A heat exchanger is slow to respond to varying conditions (steam pressure, incoming water temperature) causing a wide variation in discharge water temperature. Because of this inefficiency, in order to achieve minimum set points with a heat exchanger the target set point is set higher compared to a DSI heater which accurately controls temperature and adjusts immediately to varying conditions.In addition, because of the direct steam heating efficiency, the required set point is lowered, resulting in overall less steam usage (reducing carbon emissions by using less natural gas to make steam).
20 Direct Steam Advantages Reduced steam consumptionSignificantly lower energy costsLow maintenanceHandles fluids that are difficult to heat—avoids “burn-on”; highly viscous or abrasive slurries are no problemSmall sizeConsistent, precise discharge temperatureNo condensate return requiredDirect Steam Injection technology offers significant advantages over less efficient indirect methods of heating process fluids. Whenever it is determined that some slight dilution is acceptable, this technology should be considered.
21 Sustainability & the Triple Bottom Line Sustainability TriangleEconomicSales, profits, ROIJobs createdTaxes paidEnvironmentalAir, water qualityEnergy usageWaste producedSocialCommunity impactsProduct responsibilityFirms that maximize the sweet spot thrive in changing environments
22 Direct Steam Injection Technology Real-World Results Case Studies
23 Typical Food Processing Applications Utility HeatingCIP and COP water heatingWashdown hose stationsJacketed kettlesSterilization potsCan toppingBottle and can rinsingThermal inactivationProcess HeatingPet food processingThick stock/paste heatingBaby food/formula cooking/pasteurizingSauce heating/thickeningSoup base cookingCondiments heatingUHT pasteurizationStarch cookingSPEND TIME ON THIS SLIDE Explain some of these in more details ~ give examplesMeat and poultry sanitizing importance ~ 180F USDA regulationsCleaning/sanitizing lines at major soda and beer mfgCan topping at major veggie canning plants ~ replacing HX’sJacketed Kettles to eliminate hot spots and burn on in dairies for exampleSanitary DSI heaters are used in a variety of applications where FDA or USDA requirements need to be met.23
24 Success #1 Processor Reduces Cycle Time (Slurry Heating) Meat slurry cookingCustomer needs to give permission to use name, or use a ‘not to be named’ company format
25 Success #2 Plant Improves Throughput (Water Heating) Jacketed vessel tanksReplaced inefficient tank spargerScaling clogged heaterSteam hammer damaged tanksDSI benefit impactSelf-cleaning design increased uptime by 20%$2000/month saved by eliminating tank welding repairsConsistent temperature set-point maintained60°F incoming water raised to 200°F400 gallons per minute (widely fluctuating)
26 Success #3 Firm Improves Product – Slurry Viscosity Product in extruder - viscosity kept at acceptable levels to run smoothly and fasterSave timeSave energy
27 Summary: DSI = Sustained Benefits DSI effectively transforms heat energyNear-instantaneous energy (heat) transferEffectively 100% efficientSignificant measurable sustainable benefitsEnergy savingsSanitation effectivenessLower production costsReduced maintenance costsProductivity improvementMore work gets done = more bottom line profits!Simply ~ We transform Energy, HX’s transports it!
28 David Degelau Hydro-Thermal Corp 262.548.8900 400 Pilot Court Engineer, Certified Steam System Specialist400 Pilot CourtWaukesha, WI