Boiler is an energy consuming equipment. Especially for Northeast China, there are nearly five months in heating season every year. Therefore, we can imagine that investment in manpower and material resources is a lot. At present, China's existing boiler widespread backward technology, obsolete equipment, manual operation, high labor intensity, low energy consumption and thermal efficiency of the boiler, tea problems. This is very disproportionate to the current situation of rapid economic development in China. The emission of soot, SO2 and other pollutants caused by the use of boilers has seriously affected the atmospheric environment of our existence. In order to change this situation, in addition to improving the furnace structure, combustion method, updating equipment, the most effective method is to use computer control, according to incomplete statistics, the computer control can save 5~ 10%, but also has to reduce environmental pollution, improve the degree of automation, has the advantages of improving working conditions.
With the development of computer technology and primary instrument technology, computer controlled boiler system has been greatly developed and improved, and has been widely applied to control of large, medium and small boilers.
2 system consists of two main types of boiler microcomputer control system: distributed and centralized.
The distribution system is mainly used for large boiler system control, mainly including: central microcomputer, field microcomputer, PLC and field instrument. Centralized for small boilers, including industrial control computers, peripheral equipment, industrial automation instruments. Here, the author adopts the centralized control system, control three sets of four tons of water and steam boiler furnace, small boiler generally has the advantages of simple structure, convenient use, mainly composed of a boiler barrel, furnace, superheater, economizer, air preheater, the measurement parameters, general furnace temperature, furnace pressure, steam flow, circulation flow and exhaust temperature.
The industrial control computer is the core of the whole system, mainly used for the management and responsible for the information collection of boiler control, the whole system, print statements and Lang police, requires a friendly man-machine interface, can accurately show the timing process and various parameters of the boiler, the boiler control in the best running state.
External equipment; halo industrial control computer and field instrument connection part consists of interface component and actuator, the interface part of the collection of external sensors to collect data, and realize the control of the external, include: 32 12 A/D acquisition card, 8 Road 8 Road 32 D/A isolation card, optical isolation D/I card, D/0 card 32 optically isolated, I/V template, relay board.
An instrument to realize the visual display on the operating table, including temperature, pressure, flow and so on.
3 system has the function of automatic control mode, the system realizes the control of the boiler of a computer system in the operation process of boiler, furnace pressure can of boiler, coal, water supply automatic control 23-53 Liu Xiufeng (1975-), female, assistant engineer, mainly engaged in environmental supervision work.
System.
It has manual and automatic switching functions to ensure the normal operation of the system in any case.
The real-time display function, the multi-level management menu of the industrial computer system software, the Chinese character display, the boiler operation flow chart, the boiler running current parameter, each parameter change trend chart and so on.
The management function can automatically record the situation of the handover class, record the time of stopping the furnace, the amount of coal consumption in the statistical period, and the printing report.
The alarm function can alarm the important parameters of the boiler, such as pressure, temperature, water level and so on.
4, control content 4.1, the control of combustion to the boiler is mainly to control the combustion and control the combustion well, and the boiler can run according to the best condition, and at the same time, it can save energy. The control of combustion is divided into three parts: the amount of coal, the volume of air supply and the negative pressure of the furnace.
When the outlet temperature of the water heater or the gas pressure of the furnace is higher than the given value, the system adjusts the speed of the coal feeder according to the design control algorithm, changes the instant coal supply volume, and controls the blower to change the air supply volume accordingly.
When the boiler is in normal combustion, the furnace pressure must be kept at -20~-30Pa. If it goes beyond this range, the thermal efficiency of the boiler will be significantly reduced, and the negative pressure of the furnace is mainly regulated by the induced draft.
In a word, combustion control is a process of multivariable input, multivariable output, large inertia and large lag. Its control is quite complicated due to the fact.
4.2, the feedwater control (water level control) of the steam boiler can be divided into two single impulse, two impulse and three impulse control. For small boiler, the single impulse control and the actual water level control can meet the requirements, but the false water level phenomenon should be overcome.
The 5 - meter is selected to the reliability of the whole system and the safe operation of the boiler. The first instrument includes temperature, pressure, flow, and liquid level. The temperature and heat resistance of a nickel chromium nickel aluminium temperature, because at low temperatures, the thermal resistance with temperature measurement accuracy of strip, and a nickel chromium nickel aluminum under high temperature and high sensitivity. A differential long pass pressure gauge used for pressure measurement. For the flow, the orifice type flowmeter is selected according to the volume of the measurement.
6 application software development and application software uses the Microsoft development kit is the software design in the WindwS98 platform, using Chinese software interface, the operation is simple, intuitive, rich graphics, picture map, divided photos, trend chart, alarm loop diagram, diagram and flow chart etc.. The main performance is: the simulation of the 32 channels in the field and the switch quantity of the 12 channels are input to the computer for processing, and the screen display is given.