Dab tsi yog Kev Tshawb Fawb Cov Thickness rau 316 Stainless Hlau Rhaub hauv 25% Ammonium Nitrate Solution ntawm 110℃nrog 3 Bar Siab thiab Tsis Muaj Chlorides

Oxidising Fertilizer Service: Qhov Kev Lag Luam Tseem Ceeb - tawm

Ib qho 25% ammonium nitrate (NH₄NO₃) tov yog ib qho kev sib koom ua ke hauv kev tsim cov chiv thiab ua cov dej hloov hluav taws xob hauv qee qhov kev lag luam. Cov huab cua yog oxidising heev ntawm 110 ° C thiab 3 bar siab vim muaj nitrate ion uas yog cathodic inhibitor thiab qhov tseeb passivates 316 stainless hlau. Pitting yog qhov kev txhawj xeeb tseem ceeb thaum siv cov tshuaj chloride. Nyob rau hauv cov ntaub ntawv ntawm ammonium nitrate ob yam tsis ua hauj lwm mechanisms yuav tsum tau paub txog: kev nyuaj siab corrosion cracking nyob rau hauv concentrated nitrate daws thiab kev corrosion feem ntau yog hais tias lub pH drifts sab nraum qhov ruaj khov. Yog tsis muaj chlorides qhov kev txiav txim siab tuab yog yooj yim dua. Rau qhov kev ua haujlwm no, cov ntaub ntawv pov thawj lub thickness yog tswj hwm los ntawm kev ua haujlwm zoo, kev tiv thaiv corrosion tsis zoo, thiab nitrate-induced cracking resistance. Thermal efficiency yog ib qho me me tab sis tseem ceeb xav txog.

Electrochemical tus cwj pwm hauv NO3-solutions

Cov nitrate ion yog ib qho muaj zog oxidising tus neeg sawv cev thiab nws tiv thaiv cov zaj duab xis passive ntawm 316 stainless hlau hla ntau qhov kub thiab txias. Lub peev xwm corrosion nyob rau hauv 25% ammonium nitrate ntawm 110 ° C nruab nrab ntawm +200 thiab +400 mV piv rau nyiaj -silver chloride siv electrode thiab zoo nyob rau hauv cheeb tsam passive. Tus nqi corrosion tsis zoo nyob rau hauv xws li ib puag ncig yog tsawg heev, nyob rau hauv qhov kev txiav txim ntawm 0.002-0.008 hli ib xyoo raws li qhov hnyav poob kev tshawb fawb ntawm cov cuab yeej siv nyob rau hauv lub lag luam chiv. Uniform corrosion pub rau kaum xyoo yog 0.02-0.08 hli rau 1.2 hli phab ntsa rhaub thiab lub suab hlau yog ntau tshaj 1.1 hli. Nyob rau hauv daim ntawv thov no, lub thickness yog tsis tsav los ntawm uniform corrosion. Cov zaj duab xis passive yog qhov ruaj khov yog tias cov tshuaj pH nyob nruab nrab ntawm 4 thiab 9. Cov ammonium ion yog cov kua qaub tsis muaj zog, yog li cov tshuaj ammonium nitrate ib txwm muaj pH nyob rau hauv thaj tsam ntawm 5-6, uas yog ib qho pH ruaj khov. Corrosion tus nqi tuaj yeem nce ntxiv yog tias cov tshuaj ua paug nrog cov kua qaub (los ntawm cov txheej txheem nce siab) lossis alkali (los ntawm cov tshuaj ntxuav). Txawm li cas los xij, qhov kev ntxhov siab no feem ntau yog lub sijhawm luv luv thiab tsis tas yuav muaj kev tiv thaiv corrosion loj.

Risk ntawm Nitrate Stress Corrosion Cracking

Kev ntxhov siab corrosion cracking (SCC) yog qhov kev txhawj xeeb tseem ceeb rau 316 stainless hlau hauv cov tshuaj kub ammonium nitrate. Nitrate SCC yog dav tsim rau austenitic stainless hlau thiab susceptibility nce nrog kub thiab nitrate concentration. Ntawm 110 ° C thiab 25% ammonium nitrate, qhov kev pheej hmoo ntawm SCC yog nruab nrab, tab sis tsis tsim nyog. Qhov tseem ceeb tshaj plaws rau kev pib SCC yog tensile stress (los ntawm kev tsim khoom lossis siab) thiab muaj cov concentrated nitrate txheej rau saum npoo. Nitrate SCC tuaj yeem txhim kho ntau yam muaj peev xwm, thaum chloride SCC tshwm sim ntawm cov peev txheej tshwj xeeb. Qhov tawg tawm ntawm nitrate SCC hauv 316 stainless hlau ntawm 110 ° C yog feem ntau 0.05-0.2 hli / xyoo tom qab pib. Qhov kev txhawj xeeb tseem ceeb rau lub tshuab rhaub cua sov yog qhov seem tensile stresses los ntawm cov raj kos duab thiab khoov. Feem ntau, qhov qis ntawm phab ntsa tuab, qhov qis dua qhov seem ntawm qhov kev ntxhov siab, vim tias kev ua haujlwm txias tsawg yog qhov tsim nyog kom ncav cuag qhov kawg ntawm qhov ntev. Lub raj 1.2 hli kos feem ntau muaj qhov seem seem ntawm 50-100 MPa, hos 2.0 hli raj yuav muaj 80-150 MPa. Cov phab ntsa tuab dua muaj kev ntxhov siab ntau dua, uas ua rau muaj qhov tshwm sim ntawm SCC pib. Kev ua haujlwm tiag tiag nrog ammonium nitrate evaporators tau pom tias nyias -walled (1.2-1.5 mm) 316 stainless hlau heaters outlast tuab-walled (2.0-2.5 mm) cov cua sov ua kom zoo ib yam. Kev soj ntsuam tsis ua tiav tau pom tias cov phab ntsa tuab yog tshwm sim los ntawm SCC thaum cov phab ntsa nyias ua tsis tau los ntawm lwm yam, tsis yog corrosion ua rau tom qab kev pabcuam txuas ntxiv.

Siab Containment - 3 Bar

Ntawm 3 bar system siab qhov kev xav tau ntawm hoop kev nyuaj siab yog me ntsis. Rau ib lub raj nrog OD=12 hli thiab phab ntsa=1.2 hli, hoop stress yog 0.3 MPa x 4.8 mm / 1.2 mm=1.2 MPa. Rau phab ntsa uas yog 2.0 hli qhov kev ntxhov siab yog 0.3 MPa x 4.0 mm / 2.0 mm=0.6 MPa. Ob leeg yog me me piv rau 170 MPa yield zog. Lub thickness ntawm lub siab ntim tsis tas yuav tsum tau tshwj xeeb. Tab sis lub rhaub yuav tsum yog mechanically robust txaus los tiv thaiv lub installation torque ntawm threaded kev twb kev txuas. Rau kev txhim khu kev qha kev koom tes koj xav tau ib tug yam tsawg kawg nkaus xov engagement thickness ntawm 1.0-1.2 hli. Tsawg dua 1.0 hli, qhov kev pheej hmoo ntawm cov xov stripping lossis distortion nce ntau, tshwj xeeb tshaj yog nyob rau hauv cov kab loj dua cov cua sov.

Cov txheej txheem cua sov xav tau thiab Thermal Efficiency

Lub thermal conductivity ntawm ammonium nitrate daws yog piv rau cov dej, piv txwv li . 0.60-0.65 W / m K ntawm 110 ° C. Convective heat transfer coefficient rau turbulent flow yog 1000-2000 W/m²·K nyob ntawm qhov tshaj tawm. Lub thermal tsis kam ntawm lub sheath yog hais txog 0.0004 m²·K / W rau phab ntsa thickness ntawm 1.2 hli thiab 0.0007 m²·K / W rau phab ntsa thickness ntawm 2.0 hli. Qhov sib txawv no sib haum mus rau qhov sib txawv ntawm qhov sib txawv ntawm 3-4 ° C ntawm watt ntom ntawm 10 W / cm² (ib txwm rau cov cua sov). Rau cov txheej txheem uas muaj kev cuam tshuam rau hauv cheeb tsam overheating, nws yog ib qho tseem ceeb kom tswj tau lub sheath kub kom tsawg li sai tau. Ammonium nitrate tuaj yeem degrade exothermically saum 180 ° C. Lub phab ntsa 1.2 hli heats 110 ° C bulk tov ntawm 10 W / cm² txog li 125-130 ° C ntawm lub plhaub. Lub phab ntsa 2.0 hli yog ua haujlwm ntawm 128-134 degree. Lub decomposition kub ntawm ammonium nitrate yog hais txog 200 degree. Txawm li cas los xij, ob qho tib si qis dua thiab qhov sib txawv thermal tsis yog qhov tseem ceeb ntawm kev nyab xeeb. Txawm li cas los xij cov phab ntsa thinner me ntsis zoo dua rau kev siv hluav taws xob.

Paub meej thickness cov txheej txheem los ntawm kev lag luam kev paub

Cov khoom siv chiv muaj ntau qhov kev ua haujlwm nrog 316 stainless hlau khoom hauv ammonium nitrate kev pabcuam. Lub immersion thiab ncig cua sov tau pov thawj sheath thickness ntau ntawm 1.2-1.6 hli rau lub sij hawm ntev kev cia siab. Kev siv cov phab ntsa thinner hauv qab 1.0 hli yog tiv thaiv los ntawm cov teeb meem kev siv tshuab. Cov phab ntsa tuab dua 1.8 hli kuj raug zam vim tias lawv pom tias muaj kev ntxhov siab ntau dua thiab muaj feem ntau ntawm SCC tsis ua haujlwm. Nyob rau hauv qhov kev ua pov thawj, 1.4-1.5 hli yog suav tias yog qhov zoo tshaj plaws kev sib haum xeeb, tuab txaus rau cov neeg kho tshuab lub zog thiab ib tug nruab nrab corrosion pub, tab sis nyias txaus kom txo tau cov seem seem thiab SCC kev pheej hmoo. Rau kev tsim lub neej ntawm 10 xyoo nyob rau hauv 25% ammonium nitrate ntawm 110 ° C thiab 3 bar siab uas tsis muaj chlorides tam sim no phab ntsa thickness ntawm 1.4 hli yog tag txaus. Cov khoom siv nrog cov qauv tuav zoo kuj tseem tuaj yeem siv phab ntsa 1.2 hli. Lub phab ntsa 1.6 hli muab cov khoom siv ntxiv tab sis tsis muaj corrosion lossis SCC kom zoo dua li 1.4 hli.

Phab ntsa Thicker uas yog qhov phem dua

Cov phab ntsa tuab tsis xav tau hauv kev pabcuam ammonium nitrate, thiab tej zaum yuav muaj kev phom sij. Cov kev ntxhov siab ntau ntxiv uas tshwm sim los ntawm kev tsim cov raj tuab ua rau lub zog tsav rau SCC pib. Thaum muaj kab nrib pleb, cov phab ntsa tuab muaj cov khoom siv ntau dua rau kev tawg, tab sis qhov tawg ntawm kev loj hlob yog ywj siab ntawm thickness. Ib phab ntsa 2.0mm nrog kev tawg ntawm 0.1mm / xyoo yuav siv sijhawm 20 xyoo los perforate, 1.2mm phab ntsa yuav siv sijhawm 12 xyoos. Tab sis cov phab ntsa tuab muaj qhov pheej hmoo loj dua ntawm kev pib tawg. Cov ntaub ntawv pov thawj los ntawm ammonium nitrate factories qhia tias cov cua sov nrog 2.0-2.5 hli phab ntsa poob los ntawm SCC hauv 3-6 xyoo, thaum cov cua sov nrog 1.2-1.5 hli phab ntsa los ntawm tib tsob nroj ua haujlwm rau 8-12 xyoo thiab feem ntau ua tsis tiav los ntawm hluav taws xob rwb thaiv tsev degradation, es tsis yog sheath perforation. Cov txiaj ntsig pov thawj yog tias cov phab ntsa nyias nyias yog qhov zoo tshaj hauv cov xwm txheej nitrate SCC vim tias txo cov kab mob seem.

Kev sib piv ntawm Kev Tshawb Fawb Thickness Xaiv

Residual Hoop Stress Probability ntawm SCC Initiation Thickness ntawm SheathUniform Corrosion Allowance (10 xyoo) Mechanical Robustness Proven Service Life in Field
1.0 hli 40-80 MPa Tsawg 0.02-0.08 hli Marginal 8-10 xyoo (nyob ntawm kev tuav)
1.2 hli 50-90 MPa Tsawg 0.02-0.08 hli Tsim nyog 10-12 xyoo
1.4 hli 60-100 MpaLow-Moderate 0.02-0.08 mmZoo 10-12 xyoo (zoo dua)
1.6 hli 70-110 MPa Nruab nrab 0.02-0.08 mm8-10 xyoo Zoo heev
2.0 hli 90-140 MPaModerate-High 0.02-0.08 mm Zoo heev 5-7 xyoo (SCC-limited)
2.5 hli 110-160 MPa Siab 0.02-0.08 hli Zoo heev 3-5 xyoos (SCC-limited)
Xaus: Thickness lees paub rau lub sijhawm ntev kev cia siab

316 stainless hlau rhaub nyob rau hauv 25% ammonium nitrate tov ntawm 110 ° C nrog 3 bar siab tsis muaj chlorides cov pov thawj sheath thickness ntau ntawm 1.2-1.6 hli nrog 1.4-1.5 hli yog tsim nyog rau feem ntau installation. Los ntawm kev pom kev xeb, cov phab ntsa nyias hauv qab 1.2 hli tuaj yeem siv tau, tab sis muaj kev phom sij ntawm kev puas tsuaj thaum lub sij hawm nruab thiab tu. Cov phab ntsa tuab dua li 1.6 hli muaj cov kev ntxhov siab loj dua uas ua rau muaj kev phom sij ntawm nitrate kev nyuaj siab corrosion cracking, thiab yog li muaj kev pabcuam qis dua, txawm tias muaj cov hlau ntau dua. Qhov no yog qhov tsis sib xws rau qhov kev xav dav dav engineering uas nyob rau hauv ib puag ncig thicker yog ib txwm zoo dua rau kev tiv thaiv corrosion. Qhov no yog vim lub fact tias qhov loj tsis ua hauj lwm mechanism (SCC) yog tsav los ntawm residual kev nyuaj siab, uas nce nrog thickness. Cov kws tsim qauv xaiv lub rhaub dej rau ammonium nitrate lub luag haujlwm yuav tsum qhia qhov siab tshaj qhov tso cai rau qhov kev ntxhov siab (feem ntau yog 100 MPa) es tsis yog qhov tsawg kawg nkaus tuab. Qhov no tau lees paub tias cov neeg tsim khoom siv lub raj ntim kom zoo nrog qhov tsis tshua muaj kev ntxhov siab, uas yog qhov tseem ceeb tshaj li cov phab ntsa tuab. Cov ntawv thov feem ntau tuaj yeem teev nrog 1.4-1.5 hli hauv kev daws teeb meem los muab kev pom zoo ua ke ntawm kev ua haujlwm zoo, SCC tsis kam thiab thermal efficiency rau kaum xyoo kev pab cuam lub neej.