余熱鍋爐是利用工業企業爐窯及其它余熱熱源設備產生的余熱而生產蒸汽或熱水的一種供熱設備。它與傳統意義上的鍋爐相比僅有“鍋”而沒有“爐”，但習慣上人們仍然稱它為“余熱鍋爐”。由于“余熱”種類的多樣性從而使余熱鍋爐的結構形式各式各樣，不盡相同。余熱是在工業生產中未被充分利用就排放掉的熱量，它屬于二次能源，是一次能源和可燃物料轉換后的產物。
（一）按余熱的性質可分為以下幾大類：
1. 高溫煙氣余熱：它是常見的一種形式，其特點是產量大、產點集中，連續性強，便于回收和利用，其帶走熱量占總熱量的40~50%，該余熱鍋爐回收熱量，可用于生產或生活用熱及發電。
2. 高溫爐渣余熱：如高爐爐渣、轉爐爐渣、電爐爐渣等，該爐渣溫度在1000℃以上，它帶走的熱量占總熱量的20%。
3.高溫產品余熱：如焦爐焦碳、鋼錠鋼坯、高溫鍛件等，它一般溫度很高，含有大量余熱。
4.可燃廢氣、廢液的余熱：如高爐煤氣、煉油廠的催化裂化再生廢氣、造紙廠的黑液等，它們都可以被利用。
5. 化學反應余熱：如冶金、硫酸、磷酸、化肥、化纖、油漆等工業部門，都產生大量的化學反應余熱。
6. 冷卻介質余熱：如工業爐窯的水套等冷卻裝置排出的大量冷卻水，各種汽化冷卻裝置產出的蒸汽都含有大量的余熱，它們都可以被合理利用。
7. 冷凝水余熱：各工業部門生產過程用汽在工業過程后冷凝減小時所具有的物理顯熱。
（二）由于余熱是與其它生產設備及工藝密切相關，故余熱利用又具有以下特點：
1. 熱負荷不穩定，主要有工藝生產過程所決定。
2. 煙塵的成分、濃度、粒度差別比較大。從而使鍋爐的受熱面布置受影響，須考慮防磨、堵灰及除塵。
3.煙氣成分的多樣性，使有的煙氣具有腐蝕性。如煙氣中的SO2 、煙塵或爐渣中的各種金屬和非金屬元素等都可能對余熱設備產生低溫或高溫腐蝕和積灰。
4.受安裝物所固有條件的限制。如有的對鍋爐進、出煙口標高的限制；有的對鍋爐排煙溫度的限制，使其滿足生產工藝的要求。
（三）由于余熱煙氣性質的不同，故使余熱鍋爐的種類、結構形式各不相同。按結構特點可分為管殼式余熱鍋爐和煙道式余熱鍋爐兩大類。按余熱鍋爐進口煙氣含塵量和煙氣特性又可分為以下五類：
1. 煙氣中含塵量不大于20g/Nm3的余熱鍋爐為一類余熱鍋爐；
2. 煙氣中含塵量大于20g/Nm3且不大于70g/Nm3的余熱鍋爐為二類余熱鍋爐；
3. 煙氣中含塵量大于70g/Nm3的余熱鍋爐為三類余熱鍋爐；
4. 煙氣中含有粘結性煙塵的余熱鍋爐為四類余熱鍋爐；
5.煙氣中含有強腐蝕成分或具有有毒煙氣的余熱鍋爐為第五類余熱鍋爐。
隨著能源供應的緊張，使一些企業不斷提高“節能增效、降耗增產”的意識。因此余熱鍋爐作為“降耗、增效”的設備不斷在能源消耗大的鋼鐵、化工、建材等行業得到用戶青睞。同時各個鍋爐廠家對余熱鍋爐的開發力度和深度也逐漸加大，不斷開發出高性能的產品來占領、擴大市場分額。我廠近幾年開發的余熱鍋爐主要有碳素窯余熱鍋爐、焦化余熱鍋爐、水泥窯純低溫余熱鍋爐、化工三廢混燃余熱鍋爐、玻璃窯余熱鍋爐等系列。其主要特點如下：
碳素窯余熱鍋爐
碳素窯余熱鍋爐為立式自然循環水管鍋爐，該型鍋爐為第一類余熱鍋爐，其進口煙氣的含塵量一般為5g/Nm3左右。其爐型結構布置新穎，性能先進，同傳統碳素回轉窯余熱鍋爐相比，漏風小，密封性能好，并且占地面積小，節省投資。
水泥窯純低溫余熱鍋爐
根據水泥窯生產工藝設備及流程，應用于水泥行業純低溫余熱系統的余熱鍋爐分為窯頭余熱鍋爐和窯尾余熱鍋爐。窯頭余熱鍋爐進口煙氣來自水泥窯窯頭蓖冷機排出的熱空氣，其煙溫較低，含塵量一般為15g/Nm3左右，結合實際情況，鍋爐受熱面采用厚壁螺旋鰭片管，從而組織起更為有效的煙氣流場，加強換熱。窯尾余熱鍋爐進口煙氣來自水泥窯窯尾預熱器排出的煙氣，其煙溫較低，含塵量一般為70g/Nm3左右，粉塵含量大，運行中對受熱面的磨損較嚴重，鍋爐受熱面采用厚壁光管 。
化工三廢混燃余熱鍋爐
化工三廢混燃余熱鍋爐適用于造氣爐三廢回收利用系統的余熱爐，鍋爐采用單鍋筒的自然循環水管鍋爐，鍋爐按煙氣流動方向為立式或隧道式布置。
玻璃窯余熱鍋爐
該型余熱鍋爐利用新型浮法玻璃熔窯尾部煙氣余熱產生可供發電、生產、生活使用的蒸汽，不直接使用一次性燃料，因此它具備節能和能源綜合利用的特點。
本余熱鍋爐采用單鍋筒橫置式的立式自然循環水管鍋爐，整體布置形式采用倒U型，受熱面布置有對流管束和省煤器，各部分受熱面采用模塊化結構，整裝出廠。
燒結機余熱鍋爐
它是應用于鋼鐵行業的燒結機余熱鍋爐，該鍋爐設計入口煙溫約330℃。流經鍋爐高壓過熱器、高壓對流管束、高壓省煤器、低壓對流管束和熱水段，煙溫降至136℃左右。
燒結機余熱鍋爐熱源煙溫較低，粉塵含量較小，為了防止積灰，提高鍋爐熱效率，達到實現鍋爐an全、穩定運行的目的，本鍋爐結合實際運行情況，及其具體結構特點，在整個布置和設計中采取相應有效措施，鍋爐受熱面采用厚壁螺旋鰭片管，從而組織起更為有效的煙氣流場，加強換熱，并且能在較大程度上減輕磨損，延長檢修周期，保證鍋爐有較長的使用年限。受熱面的布置全部采用錯列形式，合理地安排管組的間距，從而既保證有足夠的煙速，達到所要求的換熱效果。
鍋爐墻選用輕型護板爐墻，降低了鍋爐漏風系數，從而滿足生產工藝和穩定發電的需要。
余熱鍋爐在生產系統中的作用
由于生產系統及余熱發電熱力系統的特殊性，鍋爐在整個系統中主要起到以下作用：
a)鍋爐起到降低整個煙氣溫度的作用，能夠保障系統中除塵設備的正常運行，達到低溫環保排放煙氣；
b)鍋爐通過利用余熱產生高溫高壓蒸汽通過與補燃鍋爐整體配套推動氣輪機和發電機發電，為整個水泥生產系統設備提供動力；
c)鍋爐具有一定的自除塵作用，分離出的灰塵可以重新回收利用，達到“一機多用”的功能。
d) 利于降低整個系統能耗，做到能源的充分利用。
余熱鍋爐設計時所應具備的條件
1、煙氣側參數：
煙氣量、煙氣進口溫度、煙氣成分、煙氣含塵量、煙氣側壓力（正壓或負壓）、鍋爐煙氣側系統阻力
2、 鍋爐參數：
鍋爐額定蒸發量、鍋爐額定蒸汽壓力、鍋爐額定蒸汽溫度、鍋爐排煙溫度
3、其它參數：
鍋爐安裝形式、鍋爐結構形式、鍋爐安裝地氣象參數或其它特殊要求。
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.
