發(fā)布時間：2018-04-26 04:39

  本文選題：分級燃燒 + 數(shù)值模擬��； 參考：《上海發(fā)電設(shè)備成套設(shè)計研究院》2017年碩士論文

【摘要】：我國是世界燃煤大國,而其中電廠發(fā)電占了約60%的煤炭使用比例。由燃煤帶來的環(huán)境問題日益突出,在其排放的各種污染物中,氮氧化物(NOx)對環(huán)境的影響最為明顯,因此控制NOx排放量為電廠清潔排放的首要指標。目前廣泛采用的是在原一次風、二次風基礎(chǔ)上增設(shè)燃燼風來降低NOx排放。燃燼風的配風率和相對高度對于爐膛出口煙溫有著重要的影響,而爐膛出口煙溫的變化關(guān)系到鍋爐整體性能的計算和運行的經(jīng)濟性,是鍋爐能否實現(xiàn)設(shè)計性能的一個重要參數(shù),對鍋爐安全經(jīng)濟運行具有直接的影響。過去采用的爐膛出口溫度計算方法只考慮了一次風的變化而忽略了二次風的配風比,由于采用空氣分級燃燒以后二次風需抽調(diào)一部分比例的風量來在爐膛主燃區(qū)上方形成補燃區(qū)域,因此改變二次風的配風比以及結(jié)構(gòu)以后對爐膛出口的溫度有著明顯的影響。隨著CFD技術(shù)的發(fā)展,對于爐膛出口溫度的計算方法修正可以不再局限于實驗法,可節(jié)約大量的時間和人力成本。本文以實際改造案例為基礎(chǔ),對超臨界鍋爐燃燼風配風率和相對高度的變化進行數(shù)值模擬,研究這些因素對爐膛出口煙溫的影響,初步分析并總結(jié)燃燼風配風率和相對高度對爐膛出口煙溫的變化規(guī)律,探討相應的計算方法。希望能為鍋爐的設(shè)計或改造提供有益的參考。研究借助FLUENT對珠海電廠一期600MW超臨界鍋爐進行模擬,以鍋爐BMCR工況數(shù)據(jù)為基礎(chǔ),選取不同燃燼風率和相對高度位置對整個爐膛進行燃燒模擬,并與實際工程改造數(shù)據(jù)相比對,期望找出燃燼風率和相對高度變化對爐膛出口煙溫影響的回歸分析表達式,即燃燒條件影響系數(shù)的計算方法。燃燼風相對高度對爐膛出口溫度的影響主要體現(xiàn)在分離燃燼風層和主燃區(qū)上層燃燒器之間的間隔,本文提出了表征該影響因素的新的當量比,與燃燼風率共同構(gòu)成了新的燃燒條件影響系數(shù)算法。該算法表明:燃燼風相對高度對爐膛出口溫度變化有一個正負斜率區(qū)間,當燃燼風相對高度低于一定值時,爐膛出口溫度與燃燼風率為負斜率線性關(guān)系,當燃燼風相對高度高于一定值時,爐膛出口溫度與燃燼風率為正斜率線性關(guān)系。改進后的燃燒條件影響系數(shù)總體為原燃燒條件影響系數(shù)的0.9倍左右,即加設(shè)燃燼風后爐膛燃燒火焰中心會有所抬高,并且爐膛出口溫度會隨燃燼風率和相對高度的變化而變化。實際工程初步驗證,結(jié)果表明該計算方法具有一定可信度。
[Abstract]:China is a big coal-burning country in the world, and about 60% of the coal is used by power plants. The environmental problems caused by coal combustion are becoming more and more prominent. Among the pollutants emitted, no _ x (no _ x) has the most obvious impact on the environment. Therefore, controlling the NOx emission is the primary index of clean emission in power plants. At present, it is widely used to reduce NOx emissions by adding cinder wind on the basis of primary and secondary air. The air distribution rate and relative height of the burning cinder have an important influence on the flue gas temperature at the outlet of the furnace, and the change of the flue gas temperature at the outlet of the furnace is related to the calculation of the overall performance of the boiler and the economy of its operation, and is an important parameter of whether the boiler can realize the design performance. It has direct influence on the safe and economical operation of boiler. In the past, the furnace outlet temperature calculation method only considered the change of primary air and neglected the ratio of secondary air to air distribution. Since it is necessary to adjust a part of the air volume of the secondary air after the air staged combustion to form a supplementary combustion area above the main combustion zone of the furnace, the change of the air distribution ratio of the secondary air and the structure of the secondary air have an obvious influence on the temperature of the furnace outlet. With the development of CFD technology, the calculation method of furnace outlet temperature can not be limited to the experimental method, and can save a lot of time and labor costs. In this paper, based on the actual reconstruction cases, the variation of the air distribution rate and the relative height of the burning cinder of supercritical boiler is simulated, and the influence of these factors on the flue gas temperature at the outlet of the furnace is studied. The variation law of air distribution ratio and relative height of burning cinder on flue gas temperature at furnace outlet is analyzed and summarized preliminarily, and the corresponding calculation method is discussed. It is hoped that it can provide useful reference for boiler design or renovation. In this paper, the 600MW supercritical boiler of Zhuhai Power Plant is simulated by FLUENT. Based on the boiler BMCR working condition data, the combustion simulation of the whole furnace is carried out at different burning cinder rates and relative height, and compared with the actual engineering reconstruction data. It is expected to find out the regression expression of the influence of the burning cinder rate and the relative height on the flue gas temperature at the outlet of the furnace, that is, the calculation method of the influence coefficient of the combustion condition. The influence of the relative height of cinder air on the outlet temperature of furnace is mainly reflected in the interval between the upper burner of separating the cinder layer and the upper layer of the main combustion zone. In this paper, a new equivalent ratio characterizing the influence factor is proposed. Together with the cinder rate, a new algorithm for calculating the influence coefficient of combustion conditions is proposed. The algorithm shows that there is a positive and negative slope range between the relative height of burning cinder and the temperature of furnace outlet. When the relative height of burning cinder is lower than a certain value, the linear relationship between furnace outlet temperature and cinder rate is linear. When the relative height of burning embers is higher than a certain value, the linear relationship between furnace outlet temperature and cinder rate is linear. The influence coefficient of the improved combustion condition is about 0.9 times of that of the original combustion condition, that is, the combustion flame center of the furnace will be raised with the addition of cinder air, and the furnace outlet temperature will change with the change of the cinder rate and the relative height. The experimental results show that the method is reliable.
【學位授予單位】：上海發(fā)電設(shè)備成套設(shè)計研究院
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TM621.2

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