Kev sib raug zoo ntawm alkalinity thiab pH nyob rau hauv cov dej demineralized yog txawv kiag li los ntawm cov pa hauv dej. Demineralized dej systems (ion pauv, rov qab osmosis + sib tov txaj / EDI) lub hom phiaj kom tshem tawm yuav luag tag nrho cov ions ntawm dej, thiab alkalinity, raws li anion (bicarbonate, carbonate, thiab lwm yam), yog ib txwm tsom rau kev tshem tawm.
1. Alkalinity yog lub cev sib cais, tab sis acidic gases nyob twj ywm.
Nyob rau hauv lub cation exchanger (cation bed), thawj bicarbonate alkalinity nyob rau hauv cov dej reacts nrog H⁺ ntawm cov resin, hloov mus rau carbon dioxide (CO₂). Hauv qhov no:
Alkalinity poob rau yuav luag xoom (bicarbonate yog khaws cia los ntawm cov resin, H⁺ hloov tawm), thiab pH poob rau ib ncig ntawm 4.3-5.5.
Cov dej ntws tawm ntawm lub sijhawm no yog cov dej acidic uas muaj CO₂, tab sis nws cov acidity los ntawm cov pa yaj, tsis muaj zog acidic anions. Lub decarbonation ntauwd (carbon separator) yog qhov tseeb rau kev tshem tawm CO₂. 1. Tshem tawm CO₂ ua rau pH nce siab tshaj 6, tab sis cov alkalinity tseem xoom. Qhov no qhia tau hais tias nyob rau hauv ib tug demineralized dej system, tsis muaj alkalinity, tus nqi pH yog kiag li tswj los ntawm CO₂.
2. Cov pH ntawm cov dej ntshiab zoo tagnrho yog cuam tshuam los ntawm cov cua.
Tom qab dhau los ntawm lub txaj sib xyaw lossis EDI, cov dej conductivity qis heev (< 0.1µS/cm), theoretically resulting in a pH of 7.00. However, if you measure the pH in an open beaker, you will often find it fluctuating between 5.6 and 6.8, inexplicably becoming acidic.
Qhov no tsis yog vim cov dej tsis zoo, tab sis qhov tseeb vim tias cov alkalinity yog xoom. Yog tsis muaj alkalinity tsis, dej ntshiab yuav tam sim nqus cov nyiaj CO₂ los ntawm huab cua, tsim carbonic acid, ua rau poob qis hauv pH. Hauv kev tsim vaj tsev, kev sib khi nitrogen thiab lwm yam kev ntsuas tau siv.
Qhov kev hloov pauv pH no tsuas yog yuav tsum muaj cov lej ntawm CO₂ (ob peb milligrams ib liter), uas yuav luag tsis muaj kev cuam tshuam rau ion load ntawm tag nrho cov kab ke, tab sis pH ntsuas tseem qhia tau tias acidity. Hauv qhov xwm txheej no, pH thiab alkalinity tsis muaj kev sib raug zoo ntawm cov pa roj carbonic acid; pH tsuas yog qhia txog CO₂ cov dej uas nyuam qhuav nqus los ntawm huab cua.
3. Kev ntsuas alkalinity tsis muaj qab hau, thiab kev ntsuas pH nyuaj.
Hauv kev kho dej ib txwm siv, ob qhov kev ntsuas no tau sib koom ua ke. Hauv dej demineralized:
Alkalinity hloov ntawm qhov ntsuas ntsuas mus rau "qhov taw qhia impurity." Thaum kuaj pom muaj qhov tseem ceeb ntawm bicarbonate alkalinity, nws qhia tau hais tias anion pauv txaj tsis ua hauj lwm, sib xyaw txaj to, los yog txo EDI kev ua tau zoo, teeb liab teeb meem. Nyob rau hauv ib txwm ua hauj lwm demineralized dej, tag nrho alkalinity yuav tsum nyob ze rau 0.
Kev ntsuas pH nthuav qhia kev sib tw tseem ceeb. Ordinary pH metres nthuav tawm cov lus teb qeeb heev ntawm cov electrode thiab cov kua dej tsis ruaj khov hauv cov dej tsis zoo - conductivity, ua rau kev nyeem ntawv kom nrawm heev.
Tus nqi pH nyeem nyob rau hauv qhov teeb meem no yuav tsis sawv cev rau qhov tseeb hydrogen ion kev ua los yog siv tau rau kev coj noj coj ua tshuaj vim tsis muaj alkalinity los tswj kev sib npaug. Kev lag luam, pH tswj hauv cov dej demineralized feem ntau tsis tso siab rau kev nyeem ntawv los ntawm offline lossis online pH metres tab sis ua tiav los ntawm kev ntxiv ammonia hauv kev faib ua feem rau qhov tshwj xeeb conductivity thiab ntws tus nqi.
4. Txhawm rau tiv thaiv corrosion, tsis muaj zog alkalinity kev sib raug zoo yuav tsum tau tsim tsim.
Lub pH ntawm boiler feedwater los yog siab - purity dej siv rau nti tu yuav tsum tau hloov mus rau 8.8-9.3 los tiv thaiv steel corrosion. Txij li cov dej ntshiab tsis muaj alkalinity, ntxiv ib tee ntawm alkali ua rau pH mus rau 10; qhia qee qhov me me ntawm CO₂ ua rau pH poob rov qab mus rau 6.
Yog li, qhov tsis muaj zog alkalinity yuav tsum tau tsim los siv cov tshuaj alkalizing tsis muaj zog (xws li ammonia lossis morpholine):
Thaum ammonia ntxiv, nws sib txuas nrog dej los tsim ammonium hydroxide, muab me me ntawm hydroxide alkalinity thiab stabilizing pH ntawm qhov tsis muaj zog alkalinity.
Qhov alkalinity no tsis yog carbonate alkalinity, tab sis qhov tsis muaj zog alkalinity pab los ntawm hydroxides. Nws lub luag haujlwm yog muab lub chaw tsis muaj me me, tiv thaiv pH los ntawm kev hloov pauv wildly nrog CO₂.
Nyob rau lub sijhawm no, pH thiab alkalinity rov qab - txuas. Muab lub hom phiaj pH tus nqi (piv txwv li, 9.0), qhov sib thooj ammonia concentration yuav tsum tau khaws cia yuav tsum tau muab xam, thiab qhov tsis muaj zog alkalinity yog indirectly kaw nyob rau hauv kev siv conductivity (specific conductivity). Hauv luv luv, nws suav nrog kev siv qhov ntsuas qhov tseeb ntawm alkalinity los tswj cov pH ntawm qhov tsis tshua muaj siab.