發(fā)布時(shí)間：2018-05-15 11:06

  本文選題：余熱鍋爐 + 受熱面��； 參考：《山東大學(xué)》2017年博士論文

【摘要】：能源短缺是社會(huì)發(fā)展中的一個(gè)嚴(yán)重問題,能源回收利用已成為能源行業(yè)關(guān)注的焦點(diǎn)。余熱鍋爐是指利用工業(yè)廢氣、廢料或廢液中的余熱加熱給水,產(chǎn)生蒸汽的設(shè)備,是余熱回收過程中最重要的部件。因此,相關(guān)余熱鍋爐運(yùn)行的分析和優(yōu)化已成為現(xiàn)階段余熱利用研究的重點(diǎn)。隨著余熱鍋爐結(jié)構(gòu)系統(tǒng)的復(fù)雜化及工況的多變性,相關(guān)動(dòng)態(tài)特性對余熱鍋爐的安全、高效運(yùn)行具有重要意義。同時(shí),由于廢氣(液)中含有大量的固體顆粒雜質(zhì),是一種多組分的復(fù)雜介質(zhì)。顆粒雜質(zhì)會(huì)以不同的形態(tài)在換熱管表面形成積灰及結(jié)渣。顆粒的沉積會(huì)導(dǎo)致余熱回收效率降低、余熱鍋爐低負(fù)荷運(yùn)行甚至被迫停機(jī)。因此,研究基于變工況、多組分的余熱鍋爐傳熱強(qiáng)化、傳熱動(dòng)態(tài)響應(yīng)特性及結(jié)構(gòu)設(shè)計(jì)和優(yōu)化具有重大意義。本文以U型直流余熱鍋爐為研究對象,運(yùn)用理論分析、數(shù)值模擬和實(shí)驗(yàn)研究方法,分析了鍋爐受熱面?zhèn)鳠帷⒘鲃?dòng)、飛灰顆粒沉積及動(dòng)態(tài)特性,主要研究工作及取得的成果如下:1.理論分析顆粒在流體中運(yùn)動(dòng)和受力過程,求解了實(shí)際工況顆粒運(yùn)動(dòng)方程數(shù)值解,并分析顆粒運(yùn)動(dòng)過程中受到的不同作用力的影響程度。結(jié)合顆粒運(yùn)動(dòng)數(shù)值計(jì)算結(jié)果及顆粒碰撞、沉積和脫附臨界速度參數(shù),建立了一個(gè)新的適用于低溫受熱面的松散型顆粒沉積理論模型,能夠較準(zhǔn)確地預(yù)測受熱面飛灰顆粒沉積位置、沉積數(shù)量及積灰形態(tài)。2.基于商業(yè)軟件Fluent 15.0,通過自定義函數(shù)(UDFs),對U型直流余熱鍋爐整體進(jìn)行了全尺寸數(shù)值模擬。研究得到各級受熱面換熱管束間的溫度場和流場分布特征,分析了入口煙氣溫度和流量對鍋爐性能的影響。對于單級受熱面,包括傳統(tǒng)順排、叉排以及一種新型順排錯(cuò)流結(jié)構(gòu),對比管排布置差異對受熱面?zhèn)鳠帷⒘鲃?dòng)和飛灰沉積的影響。針對多組分復(fù)雜介質(zhì)煙氣工況,利用低溫受熱面松散型顆粒沉積模型,研究了不同顆粒粒徑和煙氣流速對顆粒沉積的影響及沉積分布特征。數(shù)值模擬結(jié)果表明:在低溫?zé)煔夤r下,顆粒粒徑和煙氣流速是飛灰顆粒沉積的主要影響因素。較高的煙氣流速使小顆粒有較強(qiáng)的沉積傾向;較低的煙氣流速會(huì)促進(jìn)大顆粒的沉積。與傳統(tǒng)順排和叉排受熱面相比,新型順排錯(cuò)流受熱面強(qiáng)化傳熱Nu提高9.8%～23.2%,飛灰沉積降低4.9%～5.6%,該受熱面以增加壓降及煙氣流動(dòng)阻力為代價(jià),強(qiáng)化傳熱并有效減少飛灰沉積。3.設(shè)計(jì)并搭建了 U型直流余熱鍋爐綜合實(shí)驗(yàn)平臺(tái),利用某水泥廠低溫余熱對鍋爐的傳熱、流動(dòng)、積灰特性進(jìn)行分析,驗(yàn)證了數(shù)值模擬的合理性。以U型直流余熱鍋爐為研究對象,完成了不同煙氣溫度、煙氣量、給水溫度及給水量工況的余熱實(shí)驗(yàn),分析了不同工況參數(shù)對余熱鍋爐蒸汽溫度及蒸汽量的影響。以系統(tǒng)(?)效率為目標(biāo),分析了余熱鍋爐各級受熱面換熱及(?)損失,并證明U型直流余熱鍋爐可有效回收低溫余熱。為進(jìn)一步回收余熱鍋爐所產(chǎn)生高溫給水中的余熱,在理論分析的基礎(chǔ)上,構(gòu)建了變分流點(diǎn)與分流流量余熱鍋爐-閃蒸系統(tǒng)模型,通過選擇不同給水量及給水分流溫度,實(shí)現(xiàn)系統(tǒng)(?)效率優(yōu)化。實(shí)驗(yàn)結(jié)果表明,煙氣量32000 Nm3/h的典型工況下,利用余熱鍋爐-閃蒸系統(tǒng),選擇給水流量15.90 m3/h,分流水溫度409.67 K,余熱系統(tǒng)和余熱鍋爐本體最佳(?)效率分別為44.43%和54.61%,實(shí)現(xiàn)年收入861000RMB,并在1.1年后收回成本。4.基于熱力學(xué)原理和質(zhì)量、動(dòng)量及能量平衡方程,提出了一個(gè)適用于直流余熱鍋爐不同受熱面的動(dòng)態(tài)仿真模型,該模型可模擬給水在換熱管內(nèi)相變過程,彌補(bǔ)實(shí)驗(yàn)無法觀測的缺陷。模型利用Matlab/Simulink軟件建立,同時(shí)基于實(shí)驗(yàn)工況,并利用遺傳算法和粒子群算法對模型進(jìn)行參數(shù)識(shí)別和優(yōu)化。優(yōu)化后余熱鍋爐動(dòng)態(tài)模型與實(shí)驗(yàn)數(shù)據(jù)匹配度高,均方根誤差范圍2.97～4.43。兩種優(yōu)化方法適應(yīng)度函數(shù)收斂值近似,粒子群算法收斂時(shí)間更短。模型可預(yù)測在啟動(dòng)和停機(jī)期間不同工況下的溫度變化,在保證金屬換熱管使用壽命的前提下,獲取最佳運(yùn)行條件。仿真結(jié)果表明:余熱鍋爐停機(jī)時(shí)間約為啟動(dòng)時(shí)間2倍,在冷啟動(dòng)與停機(jī)過程中,水溫變化呈現(xiàn)與煙氣溫度變化相同的趨勢,但具有一定延遲。給水與煙氣共同作用決定給水飽和狀態(tài)臨界點(diǎn)及時(shí)刻。
[Abstract]:Energy shortage is a serious problem in the development of society. Energy recovery and utilization has become the focus of attention in the energy industry. The waste heat boiler is the most important part in the process of waste heat recovery, which is the most important part of waste heat recovery process using the waste heat of industrial waste gas, waste or waste liquid, and it is the most important part in the process of waste heat recovery. Therefore, the analysis and optimization of the operation of related waste heat boiler With the complexity of the structure system of the waste heat boiler and the variability of the working condition, the relative dynamic characteristics are of great significance to the safety and efficient operation of the waste heat boiler. At the same time, because of the large amount of solid particle impurities in the waste gas (liquid), it is a complex medium of multi component. The deposition of different forms on the surface of the heat transfer tube forms the accumulation of ash and slag. The deposition of the particles will lead to the reduction of waste heat recovery efficiency, the low load operation of the waste heat boiler and even the shutdown. Therefore, it is of great significance to study the heat transfer enhancement of the waste heat boiler based on the variable conditions, the dynamic response characteristics of the heat transfer and the design and optimization of the structure of the heat transfer. This paper is based on the U type straight. Flow waste heat boiler is used as the research object. Using theoretical analysis, numerical simulation and experimental research methods, the heat transfer, flow, particle deposition and dynamic characteristics of the heated surface of the boiler are analyzed. The main research work and the achievements are as follows: 1. the motion and force process of particles in the fluid are analyzed theoretically and the numerical value of the particle motion equation in the actual working conditions is solved. The influence degree of different forces in the process of particle motion is analyzed. Combining the numerical results of particle motion, particle collision, deposition and desorption critical velocity parameters, a new theoretical model of loose particle deposition suitable for low temperature heating surface is established, which can predict the position of fly ash particles deposition in the heated surface accurately. .2. is based on the commercial software Fluent 15. Through the custom function (UDFs), the overall size numerical simulation of the U type DC waste heat boiler is carried out. The temperature field and flow field distribution characteristics between the heat transfer tubes at all levels are studied. The effects of the inlet flue gas temperature and flow on the performance of the boiler are analyzed. The thermal surface, including the traditional rows, the forks and a new type of dislocation flow structure, is used to compare the influence of the arrangement of the tube arrangement on the heat transfer, flow and fly ash deposition in the heated surface. The numerical simulation results show that the particle size and gas flow velocity are the main factors affecting the deposition of fly ash particles under the low temperature flue gas condition. The higher velocity of flue gas makes the small particles more inclined to deposit, and the lower gas flow velocity will promote the deposition of large particles. The heat transfer enhancement Nu increases 9.8% ~ 23.2% and the fly ash deposit decreases by 4.9% ~ 5.6%. The heating surface is at the cost of increasing pressure drop and flue gas flow resistance, intensification of heat transfer and effectively reducing the.3. design of fly ash deposition and building a comprehensive experimental platform for U type DC waste heat boiler. The rationality of the numerical simulation is verified by the analysis of the characteristics of the dynamic and accumulating ash. Taking the U type DC waste heat boiler as the research object, the waste heat experiment of different flue gas temperature, flue gas quantity, water supply temperature and water supply condition is completed. The influence of different working conditions on the steam temperature and steam quantity of the waste heat boiler is analyzed. The system (?) efficiency is the objective and the analysis of the effect of the system (?) The heat exchange and (?) loss of the heating surface at all levels of the waste heat boiler have been proved, and it is proved that the U type DC waste heat boiler can effectively recover the low temperature waste heat. In order to further recover the waste heat from the high temperature feed water produced by the waste heat boiler, based on the theoretical analysis, a model of the variable flow point and the flow flow waste heat boiler flash system is constructed, and the water supply is selected by the selection of different water supply. The system (?) efficiency is optimized. The experimental results show that, under the typical working condition of 32000 Nm3/h, the water flow rate is 15.90 m3/h, the water flow temperature is 409.67 K, and the best (?) efficiency of the waste heat system and the waste heat boiler is 44.43% and 54.61% respectively, and the annual income is 861000RMB and 1.1. After year, the recovery cost.4. is based on the thermodynamic principle and the mass, momentum and energy balance equations. A dynamic simulation model for different heating surfaces of DC waste heat boilers is proposed. This model can simulate the phase change process in the heat exchange tube and make up for the defects which can not be observed by the experiment. The model is based on the Matlab/Simulink software and is based on the model. The parameters of the model are identified and optimized by the genetic algorithm and particle swarm optimization. The dynamic model of the afterheat boiler is well matched with the experimental data, the average square root error range is 2.97 to 4.43., and the convergence of the fitness function is approximate, and the convergence time of the particle swarm optimization algorithm is shorter. The model can be predicted in the start and downtime. The temperature change under different working conditions and the optimum operating conditions are obtained on the premise of ensuring the service life of the metal heat exchange tube. The simulation results show that the shutdown time of the waste heat boiler is about 2 times the starting time. In the process of cold start and shutdown, the change of water temperature presents the same trend as the temperature change of the flue gas, but it has a certain delay. Gas interaction determines the critical point and time of water saturation.

【學(xué)位授予單位】：山東大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2017
【分類號(hào)】：TK229.929
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本文編號(hào)：1892199