摘 要

钛白粉是白色颜料中性能最好的中间工业材料，广泛应用于涂料行业。目前，生产钛白粉的主要方法是硫酸法和氯化法，硫酸法生产钛白粉工艺过程中将会产生具有较高温度的煅烧尾气，因而具有较大的回收潜力。本课题所做的余热回收就是对年产12万吨钛白粉的～400℃的煅烧尾气进行余热回收，节能减排。

由于排放的煅烧尾气中含有较多的硫化物、水蒸汽等，露点温度较高，因而当尾气温度低于露点温度时，将会造成低温腐蚀，所以在回收尾气余热时，应控制排烟温度高于露点温度。本课题正是基于这样的实际背景，设计了一套高效回收煅烧尾气余热进行有效利用的系统装置，利用尾气的余热来将20℃常温水加热产生0.8MPa(G)、175℃饱和蒸汽，达到提高能量利用率和节能减排的目的。

根据钛白尾气在露点温度以下会造成对余热回收设备传热面低温腐蚀的特点，取热装置应控制排烟温度不低于烟气露点温度（～200℃），为防止变工况的影响，本课题采用以导热油为热媒的间接取热方式，即：低温导热油在循环油泵的驱动下进入尾气取热段，在尾气取热段内低温导热油吸收尾气的余热变成高温导热油，高温导热油流动至放热段，在放热段内高温导热油释放热量使20℃常温水被加热产生0.8MPa(G)、175℃饱和蒸汽供钛白工艺使用，同时，高温导热油降温成低温导热油，在循环油泵的驱动下，低温导热油再次回到尾气取热段内吸收尾气的热量，如此循环，达到将煅烧尾气的余热有效回收利用的目的。

本课题通过对整个换热系统进行符合工艺要求和现场空间要求的热力计算，进而设计出换热器系统各主要部件的施工图，在热力计算过程中，根据本课题的需要，选定换热管的材料、尺寸、数量和换热管的排列方式，然后进行结构计算，由于导热油蒸发器一侧压力较高，因此应对其尺寸进行强度校核。

关键词：钛白尾气 余热回收 热媒 低温腐蚀 节能

The design of a system for waste heat recovery of exhaust gas in titanium dioxide production with an annual output of 120000 tons

Abstract

Titanium Dioxide, widely used in the coatings industry, is the best intermediate industrial material for white pigments. At present, the main method of producing titanium dioxide is sulfuric acid and chlorination method, The process of producing titanium dioxide with the method of sulfuric will bring with it a higher temperature of the calcined exhaust, which has a great recovery potential. The waste heat recovery done in this paper is to recycle the heat from the calcined exhaust whose outlet temperature is about 405℃ for an annual output of 120000 tons of titanium dioxide .

Due to the exhaust gas containing sulfide and water vapor, dew point temperature is a little high. So when the exhaust temperature is lower than the dew point temperature, low temperature corrosion will appear. As a result, when it comes to the recovery of waste heat, we should ensure that the exhaust temperature is higher than the dew point temperature to avoid the appearance of low temperature corrosion. Based on this background, we design a set of efficient system to recover the heat of exhaust gas. The waste heat is used to generate 0.8MPa(G),175℃ saturated vapor by heating 20℃ saturated water to achieve the purpose of improving the energy utilization rate and energy saving and emission reduction.

It is well known that when the exhaust temperature is below the dew temperature, it will result in low temperature corrosion on the heat transfer surface of the waste heat recovery equipment. So, we should control the outlet temperature of the collector above the exhaust gas dew point temperature(200℃). In order to avoid the influence of the changing working conditions, The indirect heat transfer method which chooses heat transfer oil as heat medium is adopted in this paper. Driven by recycle oil pump, low temperature heat transfer oil enters the heat collector, meanwhile, the low temperature heat transfer oil absorbs the heat from the exhaust gas and becomes a higher temperature heat transfer oil, and then, the high temperature heat transfer oil flows to the heat release section, during which, the heat released by high temperature oil is used to make 20℃ saturated water generate 0.8MPa(G),175℃ saturated vapor, and the saturated vapor is used for the titanium dioxide process. At the same time, high temperature heat transfer oil becomes low temperature heat transfer oil, and driven by recycle pump, the low temperature heat transfer oil returns to the heat collector and then absorbs the heat of exhaust gas. Under such a circulation, the purpose of recycling the waste heat of the exhaust gas has been achieved.

In this subject, the structure parameters such as heat pipe materials, sizes and the array of the heat pipes have been designed according to the subject requirements. And so, we can design the main parts of the heat exchange system construction drawings. Then the heat balance calculation, the structure checking and the flow resistance calculation are all accomplished. However because the pressure on the side of the heat transfer oil evaporator is a little high, so we should check the strength of it’s size.

Key words: Titanium dioxide exhaust gas; Waste heat recovery; Heat medium

Low temperature corrosion; Energy saving

目录

摘 要 I

Abstract II

第一章 绪论 2

1.1 课题的研究背景和目的 2

1.2钛白粉行业现状 3

1.3钛白粉制取方法 3

1.4钛白粉尾气处理方法 3

1.5钛白尾气特点 4

1.4.1 钛白尾气余热回收新技术 4

1.6低温腐蚀 4

1.6.1 低温腐蚀机理和危害 4

1.6.2 降低排烟温度减轻低温腐蚀方法 5

1.7热媒 6

1.7.1.水热媒技术简介 6

1.7.2.水热媒技术在分散式余热回收系统上的应用原理和方式 6

1.8结束语 6

第二章 12万吨/年钛白尾气余热回收系统设计 8

2.1 设计要求 8

2.2钛白尾气余热回收系统设计中要考虑的问题 8

2.3 热力计算中遇到的问题 8

2.4 图纸设计所遇到的问题 9

第三章 热力计算书和结构设计 10

3.1原始设计参数 10

3.2取热器设计 10

3.2.2.结构设计 12

3.3导热油蒸发器设计 19

3.3.1.热平衡计算 19

3.3.2.结构计算 19

3.4．导热油蒸发器尺寸设计 22

3.5 施工图设计 23

第四章 总结 24

参考文献 25

致谢 27

第一章 绪论

1.1 课题的研究背景和目的

能源是经济发展和人类生存的物质基础，目前，能源短缺和环境问题是目前两个较为关键的问题，必须得到合适的解决实现节能减排。

我国能源总量较大，但是和此同时，能源的分配存在不平衡，是一次能源量较多，而类似石油等二次能源匮乏。从现今社会发展来看，资源利用率较为低下的问题越来越严重。但是大众对能源的所需量却是和日俱增的，对能量的品质也提出了更高的要求。从低品位余热中回收热量不仅仅是减轻了对环境的影响，而且提高了能量利用率并且减少了能量消耗。