Detailed explanation of the structure and capacity configuration and treatment of gas hot water boilers
In recent years, China's urban central heating industry has developed rapidly. Because the use of hot water heating systems has the advantages of good heating quality, energy saving, safe operation, and low equipment maintenance costs, the hot water heating system has now become the main form of winter heating in northern cities and towns in China. The development and progress of technology make it develop towards large-scale and multi-type. Arch pipe and front wall heating surface
Due to the limitation of China's environmental protection standards and considering the reliability of the operation of combustion equipment, at present, most of the hot water boilers for centralized heating in China are large-scale chain-fired hot water boilers. In actual operation, hot water boilers of different structural forms show their own technical characteristics, and at the same time, various problems are exposed.
At present, the furnace types of gas-fired hot water boilers are mainly three series: single (dual) drum water-tube hot water boilers, water-fire tube hot-shell water heaters and angle-tube hot water boilers. Various problems have occurred to varying degrees, but it is still the main type of central heating boilers in China. The structure of the single (double) drum water pipe hot water boiler inherits the structure of the original steam boiler of the same type. Its advantages are reliable operation, but the disadvantages are large boiler steel consumption, high cost, and large field installation workload, especially boiler High height, resulting in high cost of the boiler room.
In addition, due to the dense arrangement of the exhaust pipes of the flag-type heating surface at the tail of the boiler, ash plugging often occurs and it is difficult to remove. In order to enable heating companies to understand the development status of large-scale chain-fired hot water boiler furnace types, this article introduces two types of operation problems that have been summarized in recent years based on the different boiler capacities.
(1) The boiler adopts the combined structure of the heating surface of the boiler shell pyrotechnic tube and the heating surface of the water pipe. The hot water boiler takes full advantage of the technical advantages of the two heating surfaces. The drum adopts a quasi-elastic combination structure of arched tube sheet and threaded smoke pipe, which not only makes the boiler structure compact, but also has good low cycle fatigue resistance. The water cooling wall on the boiler side and the convection heating surface of the water pipe adopt a parallel structure and are connected to the upper and lower headers, which not only has high heat transfer efficiency, but also serves as the support structure of the boiler body to ensure that the boiler can expand freely and thermally expand under working conditions, and the boiler runs safely. reliable.
(2) The boiler uses the heating surface of the convection tube bundle as the flue gas flow behind the furnace to ensure that the flue gas temperature of the front tube sheet smoke box is lower than 650 ° C, which eliminates the occurrence of local subcooled boiling and scaling in the end area of the flue tube. Possibility type also eliminates the hidden danger of cracks in the tube sheet, and fundamentally solves the crack accidents that occur in the hole area of the front tube sheet of the raw water fire boiler shell-type hot water boiler with wing-shaped flue structure!
(3) The boiler working fluid adopts compound cycle technology. The front arch tube and front wall heating surface of the boiler, and the rear arch tube and rear wall heating surface adopt natural circulation method of working medium. The side water cooling wall tube and side convection tube bundle are forced circulation mode during normal operation to ensure the side water cooling wall tube. The water speed in the convection tube bundle is not only higher than the safe water speed of the heat load it receives, but also to ensure that the sediment carried by the return water is unlikely to deposit in the lower header, which completely eliminates the possibility of the side water wall tube bursting.
(4) The water-cooled wall on the boiler side and the convection heating surface of the water pipe adopt a parallel structure. If a power outage occurs during operation, the flue gas system stops working, and the side water-cooled wall pipe and water pipe convection tube bundle will automatically form a working fluid natural circulation circuit. The water capacity of the side water-cooled wall and the water pipe convection heating surface connected to the lower header is very large. The steam exhaust valve is opened immediately, and the safety of the side water-cooled wall pipe and the water pipe convection bundle is fully guaranteed!
(5) After the boiler's return water passes through the side water-cooled wall pipe and the convection heating surface of the water pipe in a forced circulation manner, all of it is sent to the bottom of the drum. Through the designed jet disturbance device, the bottom of the drum can be made during operation. Impurities and sediment do not settle, making it easy to be taken away by the hot water sent out of the boiler, or discharged by a sewage pipe installed at the bottom of the boiler. This not only ensures the safe operation of the drum, completely eliminates the accident of the drum shell blistering due to the deposition of dirt on the bottom of the drum shell, but also makes more effective and safe use of the heating surface of the drum bottom.
There are three ways to express the output of gas hot water boilers, namely kcal / h (Kcal / h), and hot water boilers are kcal / h (Kcal / h megawatt (MW)).
(1) Kcal / hour is an expression in the metric unit, which indicates the heat supplied by the hot water boiler per hour.
(2) Ton or steamed ton is a common term borrowed from a steam boiler. It means that the heat supplied by a hot water boiler per hour is equivalent to the heat of a certain quality (usually expressed in tons) from 20 ° C and all vaporized into steam. Heat.
(3) Megawatt (MW) is a unit of power in the International System of Units. The basic unit is W (1MW = 106W). ), Tons / hour (t / h), megawatts (MW official documents should use this expression.
With the development of the central heating business, more large-scale chain-fired grate boilers will be used as the main heat source or peak heat source of the central heating system. How to choose the structural form of the hot water boiler and reasonably configure the boiler capacity It has important practical significance for the energy-saving and safe operation of heating enterprises and energy-saving and consumption-reduction.