本文選題：硝酸熔融鹽　切入點：NOx　出處：《華南理工大學》2014年碩士論文　論文類型：學位論文

【摘要】：太陽能熱發(fā)電技術(shù)以其能夠緩解能源危機和提供高品質(zhì)電能等優(yōu)勢成為世界各國爭相發(fā)展的技術(shù)。高溫蓄熱技術(shù)是太陽能熱發(fā)電的關(guān)鍵技術(shù),高溫蓄熱材料又是高溫蓄熱技術(shù)的核心。硝酸熔融鹽高溫蓄熱材料以其熔點低、價格便宜、使用溫度范圍廣和粘度小等優(yōu)點成為太陽能熱發(fā)電的首選材料之一,NaNO3-KNO3二元熔鹽已應用于完全商業(yè)化的太陽能熱發(fā)電站中。 但硝酸熔鹽在高溫下不穩(wěn)定,熱分解可能會產(chǎn)生NOx,因此本文參照空氣中監(jiān)測NOx的國家標準對常見硝酸熔鹽在蓄熱過程中是否排放NOx進行系統(tǒng)地研究,并探究溫度和容器材質(zhì)(碳鋼和不銹鋼)對硝酸熔鹽排放NOx的影響,通過熱力學計算從理論上對硝酸熔鹽排放NOx的原因進行解釋。 實驗對石英舟中的硝酸熔鹽在蓄熱過程中排放的氣體進行監(jiān)測,改變溫度和加入不同材質(zhì)鋼重復實驗。結(jié)果表明,本實驗條件下硝酸熔鹽會放出NOx,且排放NOx的1h平均濃度隨溫度的升高逐漸增大。相同條件下,三、四元硝酸熔鹽排放NOx的1h平均濃度比二元熔鹽大。硝酸熔鹽接觸45#碳鋼或不銹鋼后,確實會放出更多的NOx。蓄熱后,二元熔鹽樣品中NO2-的濃度隨溫度的升高而增大,三、四元熔鹽樣品中NO3-和NO2-的含量隨溫度變化不規(guī)律。 熱力學計算表明,K/NaNO3分解為K/NaNO2和O2是二元熔鹽熱力學上能發(fā)生的反應；三、四元熔鹽含NaNO3較少,KNO3和NaNO2較多,KNO3分解為KNO2和O2以及NaNO2被空氣氧化為NaNO3和NaNO2分解為Na2O、N2和NaNO3的反應在熱力學上都可以發(fā)生,但不產(chǎn)生NOx氣體�？紤]容器材質(zhì)發(fā)現(xiàn),在熱力學上硝酸鹽能與SiO2反應生成NO和NO2,這是實驗監(jiān)測到NOx的真正原因。金屬(Fe、Cr、Ni、Mn)會與K/NaNO3反應生成NO; Fe/Cr/Ni分別或其中任意兩個與K/NaNO3反應生成NO2或與NaNO2反應生成NO的反應在熱力學上都可以發(fā)生,這些反應使硝酸熔鹽接觸碳鋼或不銹鋼后排放的NOx增多。K/NaNO3除熱分解產(chǎn)生NO2-外,也會與金屬反應產(chǎn)生K/NaNO2,使二元硝酸熔鹽接觸鋼材后樣品中的NO2-增多；而三、四元熔鹽除這兩種反應外,本身的NaNO2也會氧化或參與反應,幾種反應的結(jié)果使熔鹽中NO3-和NO2-的含量變化不規(guī)律。 上述研究表明硝酸熔融鹽在由金屬材料制成的蓄熱系統(tǒng)中運行時會排放NOx,接觸水蒸汽后會腐蝕管路；用在開式系統(tǒng)應增加尾氣吸收裝置,否則會對環(huán)境造成污染。
[Abstract]:Solar thermal power generation technology, with its advantages of alleviating the energy crisis and providing high quality electric energy, has become a competitive technology all over the world. High temperature thermal storage technology is the key technology of solar thermal power generation. High temperature storage material is the core of high temperature heat storage technology. High temperature storage material of molten nitrate salt is cheap because of its low melting point. The advantages of wide temperature range and low viscosity have become one of the preferred materials for solar thermal power generation. Nano _ 3-KNO _ 3 binary molten salt has been used in fully commercial solar thermal power plants. However, the nitric acid molten salt is unstable at high temperature, and the thermal decomposition may produce no _ x. Therefore, according to the national standard for monitoring NOx in air, this paper makes a systematic study on whether the common nitric acid molten salt releases NOx during the process of heat storage. The effect of temperature and container material (carbon steel and stainless steel) on the NOx emission of nitric acid molten salt was investigated. The reason of NOx emission from nitric acid molten salt was explained theoretically by thermodynamic calculation. The experiment was carried out to monitor the gas emitted by molten nitrate in quartz boat during the process of heat storage, to change the temperature and to add steel of different materials repeatedly. The results show that, In this experiment, nitric acid molten salt will release no _ x, and the 1h average concentration of NOx emission increases with the increase of temperature. The 1h average concentration of NOx discharged by the quaternary nitric acid molten salt is higher than that of the binary molten salt. When the nitrate molten salt contacts with 4carbon steel or stainless steel, it does release more no _ x.After heat storage, the concentration of no _ 2- in the binary molten salt increases with the increase of temperature. The contents of no 3-and no 2-in the quaternary molten salt samples vary irregularly with temperature. The thermodynamic calculation shows that the decomposition of K / nano _ 3 into K / no _ 2 and O _ 2 is the thermodynamic reaction of binary molten salt. The reactions of quaternary molten salt containing less NaNO3, less KNO3 and more NaNO2, decomposed into KNO2 and O2, and NaNO2 oxidized by air to NaNO3 and NaNO2 into Na _ 2O _ 2, N _ 2 and NaNO3 can occur thermodynamically, but no NOx gas is produced. In thermodynamics, nitrate can react with SiO2 to produce no and no _ 2, which is the real reason for the experimental monitoring of NOx. The metal Fe _ (C) / Nno _ 3 reacts with K / nano _ 3 to produce no, and Fe/Cr/Ni reacts with K / no _ 3 or any two of them to produce NO2 or NaNO2 to produce no. Should be thermodynamically possible, These reactions increase the amount of NOx emitted by nitric acid molten salt after contact with carbon steel or stainless steel. In addition to thermal decomposition, K- / nano _ 3 also reacts with metal to produce K / nano _ 2, which increases the amount of no _ 2- in the sample after binary nitric acid molten salt contact with steel; and third, In addition to these two reactions, the NaNO2 of the quaternary salt also oxidizes or participates in the reaction. The results of several reactions make the contents of no _ 3- and no _ 2- in the molten salt irregular. The results show that nitric acid molten salt will discharge no _ x when it is operated in a regenerative system made of metal materials and corrode the pipeline after contact with water vapor. The exhaust gas absorber should be added to the open system otherwise the environment will be polluted.
【學位授予單位】：華南理工大學
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：TQ126.25;TM615

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