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.