Spray Gas Quench Design Considerations - BETE Fog Nozzle, Inc.

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Maintenance ConsiderationsMaximum reliability can often beenhanced with simple system configurationsuch as strainers to prevent smallamounts of solids from plugging nozzles,as mentioned above. If nozzles are subjectto high temperature environments anddo not continually have a flow of liquidor atomizing gas, the nozzle will overheatand material failure can result. The risk ofan unplanned shutdown is reduced withscheduled maintenance to manage wearor erosion of nozzles and to inspect forpartial clogging and overheating nozzles.We recommend visual inspection and thedevelopment of a routine replacementplan. Some systems require nozzlechange-out every 1 to 2 years to fullymaintain the process performance. Forclean liquid service an annual inspectionis a starting point for a PM (PreventativeMaintenance) program.Examples of Spray Quench ApplicationsThe examples below provide aperspective on the range of designsand considerations involved insystem design.Pressurized Gas QuenchA large-scale reactor gas dry wall quenchsystem was used by a customer to cool apressurized gas stream (~100 psi) from1000° C to 250°C to protect downstreamequipment. Because this system wasrefractory lined, a dry-wall design wasessential to prevent excessive thermalstresses on the refractory. A high degreeof turndown (8:1) was necessary tomanage conditions from startup to fullrate operation. The system geometry,shown in Figure 11, had a short distancebetween the liquid injection point and theend of the refractory lining. The customerinitially used a nozzle (not from BETE)that cooled only to 500° C. The nozzleused was a spring-loaded pintle typedesigned as a steam-desuperheatingnozzle, which resulted in a large dropsize at a higher flow. BETE ApplicationsEngineering analysis showed theexcessive drop size produced by thisnozzle and the system configuration werethe root causes of inadequate cooling.The spray impinged on the refractory walland liquid flowed at the bottom of thepiping. The surface area of the liquidstream flowing co-currently with the gaslimited the ineffective heat transfer.The system designed in collaborationBETE Applications Engineering was agroup of 19 BETE TF 8 FC nozzlesarranged as shown Figure 11B. Thesewere sized to operate at a pressure dropof 200 psi to achieve the desired dropsize and spray penetration into the highvelocity gas steam. The system requiredthe addition of a high-pressure centrifugalpump to deliver quench water to the spraynozzles. Three lateral headers were usedto manage the turndown. At low rate onlyone header would be in operation and agas purge would cool the other headers.Full rate operation would have all threeheaders in operation.The resulting quench system design onlyrequired fine-tuning of the transitionpoints between the operation of one, two,and three headers. High reliability wasachieved with careful consideration of allthe operating modes and proper materialselection even though the spray lanceswere in a harsh high temperatureenvironment.QuenchLiquidCooled gasoutletHot gas inletFigure 11A. Cross section oforiginal system showing nozzlecentrally mounted in the 1 meterID system.Header 1Header 2Header 3Figure 11B. End view of headersystem and nozzles.8PERFORMANCE THROUGH ENGINEERING
Acid Gas QuenchA customer’s acid gas recovery fromenergy efficient thermal treatmentsystems required the cooling ofHydrogen Chloride acid gas betweena heat recovery boiler exit from 250° Cto 50° C at the entrance of an absorptiontower. The quench liquid for this wet-walldesign was the strong acid from theabsorber tower. As with many wet-walldesigns, the amount of evaporation of thequench liquid is approximately 10%.Entrainment of small droplets into thepacked tower reduces the countercurrentabsorption efficiency. Therefore, a largerdrop size with sufficient surface area forheat transfer was needed. A cost effectivesolution was required that was compatiblewith the corrosive hot aqueous HCl.The nozzle selected by BETE ApplicationsEngineering BETE TF 16 FC made fromglass filled PTFE. This material choiceallows operations with HCl at approximately30 psi to achieve the drop size of350 micron required for the heat transfer.These nozzles were mounted in anejector venturi inducing gas flowthrough the system.Gas Cooling ExampleA confidential process being developedby a customer required the cooling gasstream to be instantaneous and uniform.The drop size needed to achieve the50-millisecond evaporation time andquench liquid flow rate restricted thenozzle type to the two-fluid nozzle. Steamwas chosen as the atomizing gas mediumbecause any non-condensable gas wouldadd to the overall process complexity.The BETE XASR external-mix nozzlewas selected to allow the most efficientuse of steam. An internal mix nozzlewould have required additional steamto preheat the liquid to saturation.The process performance met allexpectations for the entire range ofoperating conditions and rates.SummaryAn optimized spray quench designrequires engineering analysis of theoperating environment, spray nozzleperformance and process reliability.BETE Applications Engineers willpartner with you to develop andoptimize the quench system for yourapplication. Our analysis tools andexperience with hundreds of applicationsprovide a rapid and robust engineeringdesign of your spray quench system.The result is a quench system thatoperates efficiently and reliably foryour process.BETE Fog Nozzle,Inc.50 Greenfield St.Greenfield, MA 01301 USAT (413) 772-0846F (413) 772-6729www.bete.com9PERFORMANCE THROUGH ENGINEERING
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Spray Gas Quench Design Considerations - BETE Fog Nozzle, Inc.

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