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Boiler economizer
Boiler economizer is a highly efficient and energy-saving device widely used in industrial boiler systems. Its main function is to use the waste heat of flue gas to increase the boiler feed water temperature and reduce fuel consumption, thereby achieving the purpose of energy conservation and emission reduction.
Below we will introduce the boiler economizer in detail from the aspects of definition, working principle, type, advantages and disadvantages.
What is a boiler economizer?
Boiler economizer is a heat exchange device that uses the waste heat of flue gas to heat the boiler feed water. It is usually located at the tail end of the flue of the boiler, and absorbs the heat of the flue gas to increase the feed water temperature, reduce fuel consumption, and achieve the effect of energy conservation and emission reduction.
Working principle of boiler economizer
The working principle of boiler economizer is to use the heat exchange principle to transfer the waste heat in the flue gas to the boiler feed water. Specifically, the flue gas enters the economizer from the tail end of the boiler and exchanges heat with the economizer tube group connected in parallel in the boiler system. Through heat exchange, the flue gas temperature is reduced, and the boiler feed water is heated at the same time. After the heated feed water enters the boiler, it can reduce fuel consumption and improve boiler efficiency.
Types of Boiler Economizers
Boiler economizers can be divided into many types according to their structural form and installation location. Common types include: horizontal, vertical, built-in and external.
1. The horizontal economizer has a simple structure and is easy to install, but it occupies a large area;
2. The vertical economizer has a compact structure and occupies a small area, but it is easy to accumulate dust;
3. The built-in economizer can be directly installed in the boiler body, saving space, but it will reduce the efficiency of the boiler;
4. The external economizer can be flexibly arranged, but requires additional connecting pipes.
Advantages and Disadvantages of Boiler Economizers
The advantages of boiler economizers mainly include:
1. It can significantly reduce fuel consumption and improve boiler efficiency;
2. It can reduce greenhouse gas emissions and is beneficial to environmental protection;
3. It can reduce wear and corrosion of the boiler system;
4. It can increase the boiler feed water temperature and reduce steam pipeline losses.
Boiler economizers also have some disadvantages:
1. It will increase the initial investment cost; it needs regular maintenance and cleaning;
2. It is susceptible to dust accumulation and corrosion;
3. It needs to reasonably match the flue gas volume and feed water flow.
Boiler economizers can reduce flue gas temperature, gas heat, improve boiler thermal efficiency, and save fuel. The flue gas temperature at the superheater outlet is about 700°C. Even if a large number of convection tube bundles are arranged after the superheater, because the boiler water temperature is the saturation temperature under the drum pressure, the temperature of the flue gas leaving the convection tube bundle is still as high as 250-350°C, and the flue gas still contains a lot of heat. Installing an economizer after the superheater or convection tube bundle can effectively reduce the flue gas temperature, recover a lot of heat, and save a lot of fuel. Because early boilers usually use coal as fuel, it is called an economizer.
There are many ways to classify economizers, which can be classified as follows:
1. According to the degree of heating of feed water: it can be divided into non-boiling type and boiling type;
According to the manufacturing material: there are two types of cast iron and steel pipe economizers.
Non-boiling economizers are mostly made of cast iron, but some are made of steel pipes, while boiling economizers can only be made of steel pipes. Cast iron economizers are mostly used in boilers with a pressure of 2.5MPa. If the pressure exceeds 2.5MPa, economizers made of steel pipes should be used;
2. According to the form of the device: there are two types: vertical and horizontal;
According to the relative flow direction of exhaust gas and feed water: there are three types: downstream, countercurrent and mixed;
According to the structural form: light tube economizer and fin economizer. Fin economizers include: H-type economizer (more commonly used) and spiral fin economizer.
3. According to the form of heat conduction: direct conduction and indirect conduction;
Direct conduction is to use boiler exhaust gas to directly radiate and preheat boiler water; indirect conduction is to indirectly preheat boiler water through heat transfer medium; after the 1990s, direct conduction technology has developed rapidly in China, and has made great breakthroughs in technology, mainly including patents for heat transfer oil technology and super heat conduction energy-saving technology. In particular, the aerospace super heat-conducting material technology that began in the early 21st century has been at the forefront of the world’s boiler energy-saving field.
