余热锅炉是利用工业企业炉窑及其它余热热源设备产生的余热而生产蒸汽或热水的一种供热设备。它与传统意义上的锅炉相比仅有“锅”而没有“炉”，但习惯上人们仍然称它为“余热锅炉”。由于“余热”种类的多样性从而使余热锅炉的结构形式各式各样，不尽相同。余热是在工业生产中未被充分利用就排放掉的热量，它属于二次能源，是一次能源和可燃物料转换后的产物。
（一）按余热的性质可分为以下几大类：
1. 高温烟气余热：它是常见的一种形式，其特点是产量大、产点集中，连续性强，便于回收和利用，其带走热量占总热量的40~50%，该余热锅炉回收热量，可用于生产或生活用热及发电。
2. 高温炉渣余热：如高炉炉渣、转炉炉渣、电炉炉渣等，该炉渣温度在1000℃以上，它带走的热量占总热量的20%。
3.高温产品余热：如焦炉焦碳、钢锭钢坯、高温锻件等，它一般温度很高，含有大量余热。
4.可燃废气、废液的余热：如高炉煤气、炼油厂的催化裂化再生废气、造纸厂的黑液等，它们都可以被利用。
5. 化学反应余热：如冶金、硫酸、磷酸、化肥、化纤、油漆等工业部门，都产生大量的化学反应余热。
6. 冷却介质余热：如工业炉窑的水套等冷却装置排出的大量冷却水，各种汽化冷却装置产出的蒸汽都含有大量的余热，它们都可以被合理利用。
7. 冷凝水余热：各工业部门生产过程用汽在工业过程后冷凝减小时所具有的物理显热。
（二）由于余热是与其它生产设备及工艺密切相关，故余热利用又具有以下特点：
1. 热负荷不稳定，主要有工艺生产过程所决定。
2. 烟尘的成分、浓度、粒度差别比较大。从而使锅炉的受热面布置受影响，须考虑防磨、堵灰及除尘。
3.烟气成分的多样性，使有的烟气具有腐蚀性。如烟气中的SO2 、烟尘或炉渣中的各种金属和非金属元素等都可能对余热设备产生低温或高温腐蚀和积灰。
4.受安装物所固有条件的限制。如有的对锅炉进、出烟口标高的限制；有的对锅炉排烟温度的限制，使其满足生产工艺的要求。
（三）由于余热烟气性质的不同，故使余热锅炉的种类、结构形式各不相同。按结构特点可分为管壳式余热锅炉和烟道式余热锅炉两大类。按余热锅炉进口烟气含尘量和烟气特性又可分为以下五类：
1. 烟气中含尘量不大于20g/Nm3的余热锅炉为一类余热锅炉；
2. 烟气中含尘量大于20g/Nm3且不大于70g/Nm3的余热锅炉为二类余热锅炉；
3. 烟气中含尘量大于70g/Nm3的余热锅炉为三类余热锅炉；
4. 烟气中含有粘结性烟尘的余热锅炉为四类余热锅炉；
5.烟气中含有强腐蚀成分或具有有毒烟气的余热锅炉为第五类余热锅炉。
随着能源供应的紧张，使一些企业不断提高“节能增效、降耗增产”的意识。因此余热锅炉作为“降耗、增效”的设备不断在能源消耗大的钢铁、化工、建材等行业得到用户青睐。同时各个锅炉厂家对余热锅炉的开发力度和深度也逐渐加大，不断开发出高性能的产品来占领、扩大市场分额。我厂近几年开发的余热锅炉主要有碳素窑余热锅炉、焦化余热锅炉、水泥窑纯低温余热锅炉、化工三废混燃余热锅炉、玻璃窑余热锅炉等系列。其主要特点如下：
碳素窑余热锅炉
碳素窑余热锅炉为立式自然循环水管锅炉，该型锅炉为第一类余热锅炉，其进口烟气的含尘量一般为5g/Nm3左右。其炉型结构布置新颖，性能先进，同传统碳素回转窑余热锅炉相比，漏风小，密封性能好，并且占地面积小，节省投资。
水泥窑纯低温余热锅炉
根据水泥窑生产工艺设备及流程，应用于水泥行业纯低温余热系统的余热锅炉分为窑头余热锅炉和窑尾余热锅炉。窑头余热锅炉进口烟气来自水泥窑窑头蓖冷机排出的热空气，其烟温较低，含尘量一般为15g/Nm3左右，结合实际情况，锅炉受热面采用厚壁螺旋鳍片管，从而组织起更为有效的烟气流场，加强换热。窑尾余热锅炉进口烟气来自水泥窑窑尾预热器排出的烟气，其烟温较低，含尘量一般为70g/Nm3左右，粉尘含量大，运行中对受热面的磨损较严重，锅炉受热面采用厚壁光管 。
化工三废混燃余热锅炉
化工三废混燃余热锅炉适用于造气炉三废回收利用系统的余热炉，锅炉采用单锅筒的自然循环水管锅炉，锅炉按烟气流动方向为立式或隧道式布置。
玻璃窑余热锅炉
该型余热锅炉利用新型浮法玻璃熔窑尾部烟气余热产生可供发电、生产、生活使用的蒸汽，不直接使用一次性燃料，因此它具备节能和能源综合利用的特点。
本余热锅炉采用单锅筒横置式的立式自然循环水管锅炉，整体布置形式采用倒U型，受热面布置有对流管束和省煤器，各部分受热面采用模块化结构，整装出厂。
烧结机余热锅炉
它是应用于钢铁行业的烧结机余热锅炉，该锅炉设计入口烟温约330℃。流经锅炉高压过热器、高压对流管束、高压省煤器、低压对流管束和热水段，烟温降至136℃左右。
烧结机余热锅炉热源烟温较低，粉尘含量较小，为了防止积灰，提高锅炉热效率，达到实现锅炉an全、稳定运行的目的，本锅炉结合实际运行情况，及其具体结构特点，在整个布置和设计中采取相应有效措施，锅炉受热面采用厚壁螺旋鳍片管，从而组织起更为有效的烟气流场，加强换热，并且能在较大程度上减轻磨损，延长检修周期，保证锅炉有较长的使用年限。受热面的布置全部采用错列形式，合理地安排管组的间距，从而既保证有足够的烟速，达到所要求的换热效果。
锅炉墙选用轻型护板炉墙，降低了锅炉漏风系数，从而满足生产工艺和稳定发电的需要。
余热锅炉在生产系统中的作用
由于生产系统及余热发电热力系统的特殊性，锅炉在整个系统中主要起到以下作用：
a)锅炉起到降低整个烟气温度的作用，能够保障系统中除尘设备的正常运行，达到低温环保排放烟气；
b)锅炉通过利用余热产生高温高压蒸汽通过与补燃锅炉整体配套推动气轮机和发电机发电，为整个水泥生产系统设备提供动力；
c)锅炉具有一定的自除尘作用，分离出的灰尘可以重新回收利用，达到“一机多用”的功能。
d) 利于降低整个系统能耗，做到能源的充分利用。
余热锅炉设计时所应具备的条件
1、烟气侧参数：
烟气量、烟气进口温度、烟气成分、烟气含尘量、烟气侧压力（正压或负压）、锅炉烟气侧系统阻力
2、 锅炉参数：
锅炉额定蒸发量、锅炉额定蒸汽压力、锅炉额定蒸汽温度、锅炉排烟温度
3、其它参数：
锅炉安装形式、锅炉结构形式、锅炉安装地气象参数或其它特殊要求。
Waste heat boiler is the use of industrial enterprises and other waste heat heat source furnace heat generated by the equipment to produce steam or hot water heating equipment. Compared with boilers in the traditional sense, it has only a "pot" and no "furnace," but people still call it "a waste heat boiler." Due to the variety of "excess heat" types, the structure of waste heat boilers varies from one type to another. Residual heat is the amount of heat that is emitted from an underutilized industrial production. It is a secondary energy and is the result of a conversion of energy and combustible materials.
(A) According to the nature of waste heat can be divided into the following categories:
1. High-temperature flue gas waste heat: It is a common form, which is characterized by large production, production points concentrated, continuous, easy to recycle and use, the heat taken away 40 to 50% of the total heat, the waste heat boiler Recovery of heat, can be used for production or living with heat and power generation.
2. High-temperature slag waste heat: such as blast furnace slag, converter slag, electric furnace slag, the slag temperature above 1000 ℃, it takes away the heat of 20% of the total heat.
3. High-temperature product waste heat: such as coke oven coke, steel billet, high-temperature forgings, etc., it is generally high temperature, containing a lot of waste heat.
4 combustible waste gas, waste heat: such as blast furnace gas, oil refinery catalytic cracking, waste black paper mills and so on, they can be used.
5 chemical reaction waste heat: such as metallurgy, sulfuric acid, phosphoric acid, chemical fertilizer, chemical fiber, paint and other industrial sectors, have a lot of chemical reaction heat.
6. Residual heat of cooling medium: If a large amount of cooling water is discharged from a cooling device such as a water jacket of an industrial kiln, the steam produced by various vaporizing and cooling devices contains a large amount of waste heat, all of which can be rationally used.
7. Condensate water waste heat: the industrial process steam used in the industrial process to reduce the condensation when the physical sensible heat.
(B) As the waste heat is closely related to other production equipment and processes, so waste heat utilization has the following characteristics:
1. Unstable heat load, the main process of the production process decision.
2. Soot composition, concentration, particle size difference is relatively large. So that the boiler heating surface layout affected, we must consider wear-resistant, blocking ash and dust.
3. The diversity of flue gas composition, so that some flue gas corrosive. Such as flue gas SO2, soot or slag in a variety of metals and non-metallic elements, etc. may waste heat equipment, low temperature or high temperature corrosion and fouling.
4 by the installation of the inherent conditions of the restrictions. For example, there are restrictions on the entrance and exit heights of boilers, and some restrictions on the temperature of boiler exhaust smoke make it meet the requirements of the production process.
(C) Due to the different nature of the residual heat flue gas, so the type of waste heat boiler, the structure of different forms. According to the structural characteristics can be divided into shell and tube waste heat boiler and flue-type waste heat boiler two categories. Waste heat boiler imports of flue gas dust and flue gas characteristics can be divided into the following five categories:
1. The waste heat boiler with dust content not more than 20g / Nm3 in the flue gas is the first type of waste heat boiler;
2. Waste heat boiler with dust content greater than 20g / Nm3 and not more than 70g / Nm3 in flue gas is the second type waste heat boiler;
3. Waste heat boiler with dust content greater than 70g / Nm3 in flue gas is the third type waste heat boiler;
4. Flue gas containing cohesive soot and waste heat boiler for the fourth category waste heat boiler;
5. Waste heat boilers with strong corrosion components or toxic fumes are the fifth type of waste heat boilers.
With the tight supply of energy, some enterprises have continuously raised their awareness of “energy saving, efficiency enhancement, and consumption reduction and production increase”. Therefore, waste heat boiler as "the preferred equipment for reducing consumption and increasing efficiency" is continuously favored by users in such industries as steel, chemical industry and building materials with high energy consumption. At the same time, various boilers and manufacturers of waste heat boiler development efforts and depth gradually increased, and constantly develop high-performance products to occupy and expand market share. In recent years I plant the waste heat boiler developed mainly carbon kiln waste heat boiler, coking waste heat boiler, cement kiln pure low temperature waste heat boiler, chemical waste waste heat boiler, glass kiln waste heat boiler series. Its main features are as follows:
Carbon kiln waste heat boiler
Carbon kiln waste heat boiler is a vertical natural circulation water tube boiler, which is the first type of waste heat boiler, the dust content of imported flue gas is generally about 5g / Nm3. Its furnace structure layout novel, advanced performance, with the traditional carbon rotary kiln waste heat boiler, air leakage is small, good sealing performance, and covers an area of small, save investment.
Cement kiln pure low temperature waste heat boiler
According to the cement kiln production process equipment and processes, the waste heat boiler used in the pure low temperature waste heat system of the cement industry is divided into a kiln waste heat boiler and a kiln waste heat boiler. The imported flue gas from kiln waste heat boiler comes from the hot air discharged from the kiln cooler of kiln cement kiln. The flue gas temperature is low and the dust content is about 15g / Nm3. According to the actual situation, the heating surface of the boiler adopts thick-walled spiral fin tube , So as to organize a more effective flue gas flow field and enhance heat exchange. Kiln waste heat boiler inlet flue gas from the cement kiln kiln exhaust preheater flue gas, the lower the flue gas temperature, the amount of dust is generally about 70g / Nm3, dust content, the operation of the heating surface of the more serious wear and tear, Boiler heating surface using thick-walled light pipe.
Chemical waste mixed waste heat boiler
The chemical wastes waste heat boiler is suitable for the waste heat recovery furnace of the waste gas recycling system of three waste gas generators. The boiler uses the natural circulation water boiler of the single drum, and the boiler is arranged vertically or tunnelly according to the flowing direction of flue gas.
Glass kiln waste heat boiler
The waste heat boiler utilizes the residual flue gas waste heat from the rear of the new float glass furnace to generate steam for power generation, production and life. It does not use disposable fuel directly, so it has the characteristics of energy saving and comprehensive utilization of energy.
The waste heat boiler adopts single-drum horizontal type vertical natural circulation water boiler, the overall layout adopts inverted U-shaped, heating surface is arranged with convection tube bundle and economizer, the heating surface of each part adopts modularized structure and is assembled and shipped out of factory.
Sintering machine waste heat boiler
It is a sintering machine waste heat boiler used in the iron and steel industry. The inlet smoke temperature of this boiler is about 330°C. Flow through the boiler high pressure superheater, high pressure convection tube bundles, high pressure economizer, low pressure convection tube bundles and hot water sections, smoke temperature dropped to about 136 °C.
In order to prevent fouling and improve the boiler thermal efficiency and achieve the goal of safe and stable operation of the boiler, the boiler combined with the actual operation and the specific structural characteristics of the heat exchanger in the entire layout And the design to take appropriate and effective measures, the boiler heating surface with thick-walled spiral fin tube, which organized more effective flue gas flow field, to enhance heat transfer, and to a greater extent reduce wear and tear, extending maintenance intervals, to ensure Boilers have a longer useful life. The heating surface of the layout of all staggered form, a reasonable arrangement of pipe spacing, which not only ensure adequate smoke speed, to achieve the required heat transfer.
Boiler wall light armored wall selection, reducing the boiler air leakage coefficient, so as to meet the production process and the need for stable power generation.
The role of waste heat boilers in production systems
Due to the particularity of the production system and the thermal system of waste heat power generation, the boiler mainly plays the following roles in the whole system:
a) The boiler plays the role of reducing the temperature of the entire flue gas, can ensure the normal operation of the dust removal equipment in the system and achieve the emission of flue gas at low temperature and environmental protection;
b) The boiler generates high-temperature and high-pressure steam by using the waste heat, and drives the gas turbine and the generator to generate power for the entire cement production system and equipment through the whole package with the afterburning boiler;
c) The boiler has a certain self-dedicated function. The separated dust can be recycled and used to achieve the function of “one machine with multiple functions”.
d) help reduce the energy consumption of the entire system, make full use of energy.
Waste heat boiler design should have the conditions
1, the flue gas side parameters:
Flue gas volume, flue gas inlet temperature, flue gas composition, flue gas dust content, flue gas side pressure (positive or negative pressure), boiler flue gas side system resistance
2, the boiler parameters:
Boiler rated evaporation, boiler rated steam pressure, boiler rated steam temperature, boiler exhaust temperature
3, other parameters:
Boiler installation form, boiler structure, boiler installation site weather parameters or other special requirements.
