1. Drum

Its function is to collect, store, purify steam and supplement water supply. In water tube boilers, there are usually 1 or 2 cylinders, the upper cylinder is called the steam drum (drum), and the lower one is called the water drum or mud drum. Inside the upper cylinder is a water distribution tank, a water separation device and a continuous blowdown device. Hot water boiler drum internal assembly pipe and partition, etc. The upper cylinder is equipped with a main steam valve, auxiliary steam valve, safety valve, air valve, water level gauge, blowdown pipe and pressure gauge and other connecting pipes. One end head of the upper cylinder or the top of the manhole door.

One end of the sealing head is provided with a manhole, and the bottom is provided with a periodic blowdown device. The upper and lower cylinders are connected with many rising pipes and falling pipes (bundles), and the whole component is elastic structure.

Shell type boiler drum, in addition to the role of water tube boiler upper and lower drum, but also arranged in the smoke pipe, some also have combustion chamber furnace and other heating surface, at the same time the drum is a part of the heating surface.

The flat head of the drum with the smoke pipe is called the tube plate. The tube plate is in the shape of a flat plate, and the edge is welded to the cylinder. There are many pipe holes on the tube plate, and the smoke pipe is connected by expansion or welding. The part of the tube plate without a smoke pipe is the weak link in the pressure. It is usually strengthened by Angle plate cable-stays or round cable-stays. The stretch is welded between the tube section and the tube plate.

At present, a new convex head tube plate is developed to connect with the tube group, which further reduces the thickness of the tube plate and the flow condition, and improves the stress condition.

2, water wall heating surface

Water wall is a radiant heating surface arranged around the furnace. In the industrial boiler is generally made of φ51×3~φ63.5×3.5mm boiler steel pipe, is the main heating surface of water tube boiler. Radiant heating surface absorbs radiant heat from flame and shields the furnace wall, so it plays a protective role to the furnace wall. At the same time, because of more heat absorption, can reduce the furnace temperature, but also prevent coal burning coking effect.

The upper part of the water wall is directly connected with the upper pot or connected with the upper pot cylinder after passing through the upper box. The furnace water of the upper cylinder is injected into the lower cylinder and the lower collection box through the descending pipe, and absorbs heat through the water wall to form the mixture of soda water, and rises to the upper cylinder to form a closed natural cycle.

In the past, some quick boilers had fins (also called fins) welded to both sides of the water wall tubes. Its purpose is to receive more furnace radiation heat, but also to increase the shielding area of the furnace wall. Because of its difficult processing and poor thermal conductivity, easy to crack, serious tear water wall pipe, so it has been less used, and gradually replaced by special-shaped steel pipe.

3. Collection box

It is the main component of the arrangement and connection of the collecting furnace tube, and has the function of distributing water supply and extraction. According to its location, there are upper and lower collection boxes or import and export collection boxes.

The upper collection box is located in the upper part of the furnace tube, which collects the water vapor mixture of the rising tube bundle and leads to the cylinder through the conduit. Some upper collection boxes are installed on the outside of the furnace wall, and rows of hand holes are opened in the opposite position of the furnace tube for cleaning the inside of the furnace tube.

The lower collecting box is located at the lower part of the furnace tube and is connected with the lower cylinder for water supply and distribution to the riser tube. Located on both sides of the grate under the box, has the function of preventing grate on both sides of the furnace wall from burning out or hanging coke, called coke box. The lower collection box is provided with a blowdown pipe, and the end is also provided with a hand hole for checking and cleaning the inside of the collection box.

In addition to the boiler body collection box, economizer, superheater and other components also have their own corresponding collection box.

The collecting box is generally made of seamless steel pipe with large diameter and welded with two end caps. In recent years, some manufacturers will spin the pipe end to close, instead of welding end cover, more reasonable structure.

4, convection tube bundle heating surface

Convection tube bundle, also known as convection tube, is located between the upper and lower cylinders, generally composed of φ51×3mm boiler steel pipe, is the main heating surface of water tube boiler. In order to fully absorb heat, usually in the middle of the convection tube bundle, composed of baffle wall back and forth or turning flue, increase the flue gas flow, and with a higher smoke speed transverse scour tube bundle. Usually washed by the flue gas tube bundle, due to the high temperature of the flue gas heat transfer more, the density of the pipe soda mixture is small, become a rising pipe, on the contrary, the flue gas temperature low heat transfer less, become a falling pipe.

Smoke scour tube bundle, generally using transverse scour. Because of lateral scour, the thermal effect is superior to longitudinal scour. When the pipe is in the same case of transverse scour, the heat transfer effect of pipe cross row (or called fork row) is better than that of straight row, but with the improvement of heat transfer effect, the flow resistance of flue gas increases correspondingly.

5, fireworks tube heating surface

The smoke pipe is the main heating surface of the smoke pipe boiler and the water and fire pipe combined boiler. Its function is that when the high temperature flue gas produced by the furnace combustion flows through the pipe, it constantly heats the water outside the pipe, so that it gradually becomes steam (or hot water). The smoke pipe is generally installed in the pot shell, and is fixed on the tube plate at both ends by welding or expansion. Because the number of its installation is limited by the shell, and the tube is easy to accumulate ash clogging, easy to accumulate scale outside the tube, so it is not suitable for larger boilers. However, in recent years, we have also studied the large water and fire tube boilers and made some progress.

In recent years, a new type of smoke pipe has been popularized and applied: the threaded smoke pipe. It is to press out about 2mm of threaded grooves on the smoke pipe to improve the heat release of the smoke to the pipe wall, and the effect is remarkable. Compared with ordinary smoke pipe, the heat transfer effect of this kind of threaded smoke pipe can be increased nearly 2 times.

6. Superheater

Economizer and air preheater. They all belong to convection heating surface. In addition to the convection superheater, there are radiation superheater, the rest of the economizer and preheater are installed in the boiler tail flue. Their function is to further reduce the exhaust temperature and improve the thermal efficiency of the boiler.

Located in front of the boiler body, the furnace is a place for fuel combustion, including combustion equipment and furnace. Because of the different fuel and combustion mode, there are mainly layer furnace, chamber furnace, cyclone furnace, boiling furnace and so on. They have water wall pipes all around the furnace. In order to enhance fuel combustion, the layer furnace has front and rear arches. Although different furnace types have different structures, they all have space to organize fuel combustion and corresponding combustion equipment.

The pot and the furnace are connected by the heat transfer process, and the heating surface is the interface between the pot and the furnace. Where there is an exothermic medium (flame, smoke) on the other side, there is a heating medium (water, steam, air) on the other side, the heat transfer, the heat exchange between them is to rely on the heating surface.

The whole body is called the boiler body, which is composed of the cylinder, the heating surface and the connecting pipe and the smoke duct, the combustion equipment and the slag equipment, the furnace wall and the frame (including the platform and the escalator).