氧化鋯氧量分析儀原理 |
時間:2018-12-06 09:14:03 點擊: 次 |
氧化鋯氧量(liang)分析儀,它又被(bei)稱為氧化(hua)鋯氧分析儀(yi),氧(yang)化鋯分析儀/氧(yang)化鋯氧(yang)量(liang)計/氧(yang)化鋯氧(yang)量(liang)表。主要用于測(ce)(ce)量(liang)燃燒(shao)過程(cheng)中(zhong)煙氣(qi)的含氧(yang)濃(nong)度,同(tong)樣也適用于非燃燒(shao)氣(qi)體氧(yang)濃(nong)度測(ce)(ce)量(liang)。在傳感器內(nei)溫(wen)度恒定的電(dian)化學電(dian)池(氧(yang)濃(nong)差電(dian)池,也簡稱(cheng)鋯頭(tou))產(chan)生一個毫伏電(dian)勢(shi),這個電(dian)勢(shi)直接反應出煙氣(qi)中(zhong)含氧(yang)濃(nong)度值。 氧(yang)傳感(gan)器(qi)(qi)(qi)的(de)關鍵部件是(shi)氧(yang)化鋯,在氧(yang)化鋯元件的(de)內(nei)(nei)外兩(liang)側涂上多(duo)孔性(xing)鉑電極制成(cheng)氧(yang)濃度(du)差電池(chi)(chi)。它位于(yu)傳感(gan)器(qi)(qi)(qi)的(de)頂端。為了使(shi)電池(chi)(chi)保(bao)持額定的(de)工作溫度(du),在傳感(gan)器(qi)(qi)(qi)中(zhong)設(she)置了加熱(re)器(qi)(qi)(qi)。用氧(yang)分析(xi)儀內(nei)(nei)的(de)溫度(du)控制器(qi)(qi)(qi)控制氧(yang)化鋯溫度(du)恒(heng)定。氧(yang)化鋯氧(yang)量分析(xi)儀的(de)構(gou)成(cheng)是(shi)由(you)氧(yang)傳感(gan)器(qi)(qi)(qi)(又稱氧(yang)探頭、氧(yang)檢測器(qi)(qi)(qi))、氧(yang)分析(xi)儀(又稱變送(song)器(qi)(qi)(qi)、變送(song)單元、轉換器(qi)(qi)(qi)、分析(xi)儀)以及它們之間的(de)連接電纜等組成(cheng)。 氧(yang)化(hua)(hua)鋯(gao)(gao)(gao)探(tan)頭是(shi)利(li)用氧(yang)化(hua)(hua)鋯(gao)(gao)(gao)濃差(cha)電勢來(lai)測定氧(yang)含量(liang)的(de)(de)傳(chuan)感器,其(qi)核(he)心的(de)(de)氧(yang)化(hua)(hua)鋯(gao)(gao)(gao)管(guan)安置在一微型電爐內,位于整個探(tan)頭的(de)(de)頂(ding)端。氧(yang)化(hua)(hua)鋯(gao)(gao)(gao)管(guan)是(shi)由氧(yang)化(hua)(hua)鋯(gao)(gao)(gao)材料(liao)摻以一定量(liang)的(de)(de)氧(yang)化(hua)(hua)釔或氧(yang)化(hua)(hua)鈣經高溫燒結(jie)后形成的(de)(de)穩定的(de)(de)氧(yang)化(hua)(hua)鋯(gao)(gao)(gao)陶瓷燒結(jie)體。 由于(yu)它的立方晶格中(zhong)(zhong)含有氧(yang)(yang)(yang)(yang)(yang)離(li)子(zi)(zi)空(kong)(kong)(kong)穴,因(yin)此在(zai)高溫下(xia)(xia)它是(shi)良好的氧(yang)(yang)(yang)(yang)(yang)離(li)子(zi)(zi)導體(ti)。因(yin)其這一(yi)特性,在(zai)一(yi)定高溫下(xia)(xia),當鋯(gao)管兩(liang)邊(bian)(bian)的氧(yang)(yang)(yang)(yang)(yang)含量(liang)不同時,它便是(shi)一(yi)個(ge)(ge)典(dian)型的氧(yang)(yang)(yang)(yang)(yang)濃差電(dian)(dian)(dian)(dian)池(chi),在(zai)此電(dian)(dian)(dian)(dian)池(chi)中(zhong)(zhong),空(kong)(kong)(kong)氣(qi)(qi)(qi)(qi)(qi)(qi)是(shi)參比(bi)氣(qi)(qi)(qi)(qi)(qi)(qi),它與煙(yan)(yan)氣(qi)(qi)(qi)(qi)(qi)(qi)分別位(wei)于(yu)內外電(dian)(dian)(dian)(dian)極(ji)。在(zai)實際(ji)的氧(yang)(yang)(yang)(yang)(yang)探頭中(zhong)(zhong),空(kong)(kong)(kong)氣(qi)(qi)(qi)(qi)(qi)(qi)流經(jing)外電(dian)(dian)(dian)(dian)極(ji),煙(yan)(yan)氣(qi)(qi)(qi)(qi)(qi)(qi)流經(jing)內電(dian)(dian)(dian)(dian)極(ji),當煙(yan)(yan)氣(qi)(qi)(qi)(qi)(qi)(qi)氧(yang)(yang)(yang)(yang)(yang)含量(liang)P小于(yu)空(kong)(kong)(kong)氣(qi)(qi)(qi)(qi)(qi)(qi)氧(yang)(yang)(yang)(yang)(yang)含量(liang)P0(20.6%O2)時,空(kong)(kong)(kong)氣(qi)(qi)(qi)(qi)(qi)(qi)中(zhong)(zhong)的氧(yang)(yang)(yang)(yang)(yang)分子(zi)(zi)從(cong)外電(dian)(dian)(dian)(dian)極(ji)上(shang)奪(duo)取4個(ge)(ge)電(dian)(dian)(dian)(dian)子(zi)(zi)形成2個(ge)(ge)氧(yang)(yang)(yang)(yang)(yang)離(li)子(zi)(zi),發生(sheng)如下(xia)(xia)電(dian)(dian)(dian)(dian)極(ji)反(fan)(fan)應(ying): O(P0)+4e-→2O-氧(yang)(yang)(yang)(yang)(yang)離(li)子(zi)(zi)在(zai)氧(yang)(yang)(yang)(yang)(yang)化(hua)鋯(gao)管中(zhong)(zhong)迅速遷(qian)移(yi)到煙(yan)(yan)氣(qi)(qi)(qi)(qi)(qi)(qi)邊(bian)(bian),在(zai)內電(dian)(dian)(dian)(dian)極(ji)上(shang)發生(sheng)相反(fan)(fan)的電(dian)(dian)(dian)(dian)極(ji)反(fan)(fan)應(ying): 2O-2 →O(P0)+4e- 由于(yu)氧(yang)(yang)(yang)(yang)(yang)濃差導致氧(yang)(yang)(yang)(yang)(yang)離(li)子(zi)(zi)從(cong)空(kong)(kong)(kong)氣(qi)(qi)(qi)(qi)(qi)(qi)邊(bian)(bian)遷(qian)移(yi)到煙(yan)(yan)氣(qi)(qi)(qi)(qi)(qi)(qi)邊(bian)(bian),因(yin)而產生(sheng)的電(dian)(dian)(dian)(dian)勢又導致氧(yang)(yang)(yang)(yang)(yang)離(li)子(zi)(zi)從(cong)煙(yan)(yan)氣(qi)(qi)(qi)(qi)(qi)(qi)邊(bian)(bian)反(fan)(fan)向遷(qian)移(yi)到空(kong)(kong)(kong)氣(qi)(qi)(qi)(qi)(qi)(qi)邊(bian)(bian),當這兩(liang)種(zhong)遷(qian)移(yi)達到平(ping)衡后,便在(zai)兩(liang)電(dian)(dian)(dian)(dian)極(ji)間產生(sheng)一(yi)個(ge)(ge)與氧(yang)(yang)(yang)(yang)(yang)濃差有關(guan)的電(dian)(dian)(dian)(dian)勢信號E,該電(dian)(dian)(dian)(dian)勢信號符合"能斯特"方程: E=(RT/4F)Ln(P0 /P) (1) 式中(zhong)(zhong)R、F分別是(shi)氣(qi)(qi)(qi)(qi)(qi)(qi)體(ti)常(chang)數和法(fa)拉第常(chang)數,T是(shi)鋯(gao)管絕(jue)對(dui)溫度(du)(K), P0是(shi)空(kong)(kong)(kong)氣(qi)(qi)(qi)(qi)(qi)(qi)氧(yang)(yang)(yang)(yang)(yang)含量(liang)(20.6%O2), P 是(shi)煙(yan)(yan)氣(qi)(qi)(qi)(qi)(qi)(qi)含量(liang)。 由(you)(1)式可見,在(zai)一定的(de)(de)高(gao)溫(wen)條(tiao)件(jian)下(xia)(一般)600℃),一定的(de)(de)煙(yan)氣(qi)氧含(han)量(liang)便會(hui)有一對應的(de)(de)電勢(shi)(shi)輸出(chu)(chu),在(zai)理(li)想(xiang)狀態下(xia),其(qi)電勢(shi)(shi)值(zhi)在(zai)高(gao)溫(wen)區域內對應氧含(han)量(liang)。在(zai)理(li)想(xiang)狀態下(xia),當被(bei)測煙(yan)氣(qi)與參(can)比氣(qi)濃度一樣時,其(qi)輸出(chu)(chu)電勢(shi)(shi)E值(zhi)為 0 mV, 但在(zai)實(shi)際應用中,鋯(gao)(gao)管實(shi)際條(tiao)件(jian)和現場情況均不是理(li)想(xiang)狀態。故事實(shi)上的(de)(de)鋯(gao)(gao)管是偏離此值(zhi)的(de)(de)。 實際(ji)上,一定氧含(han)量鋯管(guan)輸(shu)出的(de)電勢為(wei)理論值(zhi)和(he)本底電勢的(de)和(he),我們稱(cheng)為(wei)無濃差條件(jian)下(xia)鋯管(guan)輸(shu)出的(de)電勢值(zhi)為(wei)本底電勢或稱(cheng)為(wei)零(ling)位電勢,此值(zhi)的(de)大小又在不同溫度下(xia)呈不同的(de)值(zhi),并(bing)且隨鋯管(guan)使用期(qi)延長而變化。因此,如不對此情況處理,會嚴重影響整套測氧儀的(de)準(zhun)確和(he)探(tan)頭壽命。 鑒(jian)于此,ZO系列(lie)氧分(fen)析儀采取了(le)(le)"雙參數校正法",對探頭本底電勢作特(te)殊處理,彌補(bu)了(le)(le)鋯(gao)管的(de)離散性缺陷,延(yan)長了(le)(le)探頭的(de)使用壽命。 |
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