Combustion system of methanol boiler: burner

The burner is the core part of the methanol boiler, so the fuel is atomized after it is injected into the boiler through the burner, and it is easy to mix with air to burn quickly and release heat quickly. classify

Burners are also called burners, which can be divided into oil burners and gas burners according to fuel; According to the object of use, it is divided into kiln burner and boiler burner; According to the application fields, it can be divided into industrial burners, civil burners and special burners. Among them, fuel burners are divided into light oil (such as diesel oil) and heavy oil burners (such as waste engine oil), and gas burners are divided into natural gas burners, liquefied gas burners, city gas burners, biogas burners and so on. We usually refer to the boiler burner.

Advantages and principles Compared with coal-fired boilers with the same parameters and capacity, the thermal intensity of the furnace volume can be doubled, that is, it can reach1046.6×10kj/m.h. However, in order to reduce the thermal load in the burner area and prevent the water wall tubes in this area from overheating, the furnace volume is only reduced by about 1/3. Because there is little ash in the fuel oil, slagging will not occur on the convection heating surface, so the flue gas temperature at the furnace outlet can be as high as 1300 ~ 1350℃, and the inter-tube pitch of the convection heating surface can be reduced, so as to improve the heat transfer coefficient of the heating surface and save the heating area and steel. In order to prevent the carbon black and grease accumulated on the economizer and air preheater from spontaneous combustion, steam soot blowers must be installed on these parts to keep the heating surface clean. At the same time, membrane wall can be used to make a boiler with slightly positive pressure (500 ~ 1000 N/m) because the fuel does not coke slag. The induced draft fan can be omitted, and the flue gas can be discharged out of the furnace only by the blower. If the whole shell of the boiler is made of thick steel plate, it can also be made into a positive pressure (0.3 ~ 0.6 MPa) boiler, which can make the whole structure of the boiler more compact and is mostly used in gas-steam combined cycle generator sets. The overall layout of the boiler is similar to that of the coal-fired boiler, except that the bottom of the furnace of the oil-fired boiler is mostly made into a holding furnace bottom inclined to the back wall10 ~ 30 to obtain good combustion characteristics. In order to atomize fuel, there are two types of fuel nozzles: mechanical centrifugal fuel nozzle and steam atomizing Y fuel nozzle. With the help of the pressure (2 ~ 3.9 MPa) of the oil entering the burner, the mechanical centrifugal nozzle makes the oil flow into the atomizing sheet with tangential grooves from many small holes, enters the vortex chamber in the center of the atomizing sheet at a great speed, rotates at a high speed, and is ejected to form a hollow conical atomizing torch (Figure 1). This nozzle has two forms: simple mechanical type (Figure 2) and oil return type. The former has simple structure, but poor fuel injection regulation. When the boiler load changes, it is necessary to change the oil pressure to change the fuel injection quantity. However, if the oil pressure decreases, the atomization quality will be poor, so it is only suitable for boilers with basic load or infrequent load adjustment. The latter is to make part of the oil flowing into the vortex chamber from the tangential groove flow to the oil return pipeline through the oil hole in front of the oil outlet, and adjust the oil injection amount by changing the oil return amount (that is, oil return adjustment). Because the oil pressure entering the vortex chamber is basically unchanged, the atomization quality of oil is not affected, so it can adapt to large load changes. Oil return can be divided into single-hole oil return and porous oil return. Steam atomizing Y nozzle atomizes oil by high-speed steam injection. The nozzle head consists of oil holes, steam holes and mixing holes arranged in Y-shape. The oil pressure is 0.5 ~ 2 MPa, and the steam pressure is 0.6 ~ 1 MPa. Oil and steam enter the mixing hole and collide with each other to form emulsified oil-steam mixture, which is then sprayed into the furnace through the mixing hole to form an atomizing torch. In terms of adjustment, keep the steam pressure unchanged and adjust the oil pressure to change the fuel injection quantity. The oil burner consists of an oil nozzle and an air conditioner. The former is used to inject fuel into the furnace to form an atomizing torch. The function of the latter is to provide an appropriate amount of air to the oil droplets in the atomizing torch. In order to prevent the oil and gas evaporated from atomized oil droplets from cracking under anoxic conditions above 700℃ and producing carbon black particles that are difficult to burn out, it is necessary to mix some air and oil mist in advance to oxidize the oil and gas without cracking. Therefore, the air conditioner can be designed as a volute or equipped with guide vanes with adjustable opening to make the air rotate, and then the rotating airflow sprayed from the circular tube in the center of the volute is well mixed with the atomizing oil gun, as shown in figure 1. Oil burners, such as pulverized coal burners, can be arranged at the front wall, front and rear walls, top or four corners of the furnace. According to the capacity of the boiler, each furnace can be equipped with 8 ~ 40 oil burners. When the fuel oil contains vanadium, it will cause high temperature corrosion of the tube wall in the superheater area of the boiler. When the sulfur content of oil is high, it will cause low temperature corrosion in economizer and preheater area. These two kinds of corrosion will lead to equipment damage and affect the availability of the boiler. The solution is to adopt low excess air operation mode. Excessive air is controlled at 1 ~ 3%, which can effectively inhibit corrosion. Definition of boiler This kind of boiler which uses methanol as fuel and burns with burner is called methanol boiler.