SCR脱硝尿素催化热解实验与数值模拟研究

论文总字数：41348字

摘 要

关键词：尿素；热解；二氧化钛；CFD

Theoretical Study on Catalytic Pyrolysis of Urea and Numerical Simulation of Urea Catalytic Pyrolysis Furnace

03213728 Haoran Du

Supervised by Zhaoping Zhong

Abstract： With the country’s increasing emphasis on production safety, urea has gradually replaced liquid ammonia and ammonia with its safety. Urea has become an important raw material for ammonia production. However, the traditional urea pyrolysis technology uses about 650 ℃ hot air which is generally heated by fuel, gas or electric to decompose urea solution. It consumes high energy. This study adds pieces of catalyst to improve the rate of urea pyrolysis reaction and reduce the temperature of ammonia decomposition which saves energy. Through the thermogravimetric analysis of urea pyrolysis, we choose titanium dioxide because of its better catalytic performance. We carry out the pyrolysis experiment of urea aqueous solution in two-stage tubular furnace reactor. We use the controlling variate method to investigate the various factors of pyrolysis process of urea solution, such as pyrolysis temperature, gas flow rate, urea solution concentration and the catalyst presence. At the same time, we studied the catalytic pyrolysis furnace of urea by Gambit modeling and Fluent calculation to optimize the size of furnace and flow field analysis. Through the study, we found the catalytic effect of the catalyst on the pyrolysis of urea solution is obvious at low temperature (below 350 ℃). And the temperature required for urea pyrolysis can be greatly reduced by adding the catalyst which also ensures the efficiency of pyrolysis. The initial concentration of urea solution and the carrier gas flow will also affect the ammonia production rate. At the same time, we change the air intake device and the different sections’ size of the urea-catalyzed pyrolysis furnace so that the air flow of the urea pyrolysis furnace main body transverse section is faster beside the wall area, and the flow rate of center region is uniform. This avoids the crystallization of urea solution on the wall. On the basis of the DPM model and the atomizing nozzle model, the number of guns and the length of the furnace are determined so that the droplet trajectory is centered. Through the combination of experimental investigation and CFD numerical simulation, we have obtained the important factors that influence the pyrolysis of urea, and optimize and improve the urea pyrolysis furnace.

Key words: Urea；Pyrolysis；Titanium dioxide；CFD

目 录

1绪论………………………………………………………………………………………………1

1.1研究背景……………………………………………………………………………………1

1.2研究意义……………………………………………………………………………………1

1.3尿素催化热解基础理论……………………………………………………………………2

1.4研究内容………………………………………………………………………………………4

1.5特色与创新…………………………………………………………………………………5

1.6技术关键……………………………………………………………………………………5

2尿素催化热解实验………………………………………………………………………6

2.1实验装置……………………………………………………………………………………6

2.2实验方案……………………………………………………………………………………7

2.3催化剂对尿素热解效率的影响……………………………………………………………8

2.4尿素溶液初始浓度对尿素催化热解效率的影响…………………………………………9

2.5载气流量对尿素催化热解效率的影响………………………………………………… 10

3尿素催化热解炉数值模拟……………………………………………………………………12

3.1模拟步骤………………………………………………………………………………12

3.2模型选择………………………………………………………………………………12

3.3评价指标及优化思路………………………………………………………………………13

3.3.1评价指标……………………………………………………………………………13

3.3.2优化思路……………………………………………………………………………13

3.4不带喷淋的CFD模拟………………………………………………………………………14

3.4.1进气部件模拟优化研究……………………………………………………………15

3.4.2尺寸和扩展角度模拟优化研究……………………………………………………21

3.5带喷淋的CFD模拟…………………………………………………………………………34

3.6尿素催化热解炉初步研究…………………………………………………………………43

3.6.1无喷淋的CFD模拟…………………………………………………………………44

3.6.2有喷淋的CFD模拟…………………………………………………………………46

4总结……………………………………………………………………………………………48

4.1尿素催化热解实验总结……………………………………………………………………48

4.2尿素催化热解炉CFD模拟总结……………………………………………………………48

致谢……………………………………………………………………………………………50

参考文献………………………………………………………………………………………51

尿素催化热解实验探究及尿素催化热解炉流场模拟

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