Jiangsu Xianda paperless recorder in the boiler how to control the temperature - Database & Sql Blog Articles

A series of multi-channel paperless recorders produced by Jiangsu Xianda Instrument Co., Ltd.

Control of Temperature in Paperless Recorder Boiler Control of Temperature in Paperless Recorder Boiler Microcomputer Control is a new technology developed in recent years. It is a microcomputer soft, hardware, automatic control, boiler energy saving and other technologies. Closely combined products, there are more than 300,000 medium and small boilers in China, and the annual coal consumption accounts for 1/3 of China's raw coal production. At present, most industrial boilers are still in high production with high energy consumption, high waste, and environmental pollution. status. Improving thermal efficiency, reducing coal consumption, and controlling with a microcomputer are a far-reaching task.
As a boiler control device, its main task is to ensure the safety, stability and economic operation of the boiler and reduce the labor intensity of the operators. It adopts microcomputer control and can perform many functions such as automatic detection and automatic control of the boiler.
The boiler microcomputer control system generally consists of the following parts: the boiler body, the primary instrument, the microcomputer, the manual switching operation, the actuator and the valve, the slip motor, etc. The primary instrument will measure the temperature, pressure and flow of the boiler. The amount of oxygen and the speed are converted into voltage, current, etc., which are sent to the microcomputer. The hand automatically switches the operation part. When manually, it is manually controlled by the operator. The operator controls the slip motor and the valve, and the control signal is sent to the microcomputer automatically. Part of the automatic operation. The microcomputer monitors, alarms and controls the operation of the whole boiler to ensure the normal and reliable operation of the boiler. In addition to ensuring the safety of the boiler operation, important parameters such as boiler water level and boiler drum pressure should be used in the design of the microcomputer system. It is essential to set up conventional instruments and alarm devices to ensure that the water level and drum pressure have double or even triple alarm devices, so as to avoid major accidents in the boiler.
Control System:
The boiler is a relatively complicated adjustment object. It not only adjusts the quantity, but also the various quantities are related to each other, affect each other, and restrict each other. The energy conversion mechanism inside the boiler is more complicated, so it is necessary to establish an ideal mathematical model for the boiler. more difficult. To this end, the boiler system has been simplified and divided into three relatively independent adjustment systems. Of course, in some systems, other systems such as primary air volume control loops can be subdivided, but they are mainly in the following three parts:
The special combustion automatic regulation system of the furnace negative pressure is the main adjustment. The boiler combustion process has three tasks: coal supply control, air supply control, and furnace negative pressure control. Keeping the ratio of gas to air so that the air excess coefficient is around 1.08, the economics of the combustion process, and maintaining the negative pressure of the furnace, the automatic adjustment of the combustion process of the boiler is a complicated problem. For the 3×6.5t/h boiler, the combustion of the blast furnace gas is required to maximize the use of the blast furnace gas, so it can be operated according to the maximum output of the boiler, and the steam pressure is not strictly required; the economy of combustion is not done. Higher requirements. In this way, the automatic adjustment of the boiler combustion process is simplified to the constant gas flow regulation of the furnace negative pressure as the main parameter.
The size of the furnace negative pressure Pf is affected by the amount of air introduced, the amount of air blown, and the amount of gas (pressure). The negative pressure of the furnace is too small, and the furnace squirts outward and leaks blast furnace gas, which endangers the safety of equipment and operating personnel. The negative pressure is too large, the air leakage of the furnace increases, the smoke loss increases, and the power consumption of the induced draft fan increases. According to the manual manual adjustment and groping for many years, the design of Pf=100Pa of 6.5t/h boiler is carried out. The adjustment method is to adjust the air and gas ratio manually to achieve the ideal combustion state. When the induced draft fan is fully open, the furnace negative pressure is reached at 100 Pa. After the automatic input, the gas butterfly valve is adjusted to make the blast furnace gas flow under pressure fluctuations. The gas flow rate in the initial state is to maintain the optimum ratio of blast furnace gas to air during combustion.
Boiler water level adjustment unit

The water level of the drum is an important parameter affecting the safe operation of the boiler. If the water level is too high, the normal operation of the steam-water separation device will be destroyed. In severe cases, the steam will increase in water, increase the fouling on the pipe wall and affect the steam quality. If the water level is too low, it will destroy the water circulation, causing the water wall tube to rupture. In severe cases, it will cause the dry pot and damage the steam drum. Therefore, its value is too high or too low may cause a major accident. Its adjusted amount is the steam drum water level, and the adjustment amount is the feed water flow rate. By adjusting the feed water flow rate, the material inside the steam drum is dynamically balanced, and the variation is within the allowable range, due to the boiler drum water level to the steam flow rate. Positive response to changes in feedwater flow. However, when the load (vapor flow rate) increases sharply, the performance is "reverse response characteristic", the so-called "false water level". This is caused by the increase in load, which causes the drum pressure to drop and the water inside the drum. As the boiling point temperature drops, the boiling of the water suddenly increases, forming a large amount of bubbles, which raises the water level. The drum water level control system is essentially a system that maintains the balance of boiler inlet and outlet water. It is based on the water level as a control indicator of water balance. By adjusting the amount of water inflow to achieve the balance of inlet and outlet, the drum water level is maintained near the middle line of the largest steam drum separation interface to improve the evaporation efficiency of the boiler and ensure Production safety. Since the boiler water level system is a controlled object with self-balancing ability, there is a false water level in the operation. In actual application, the water level single impulse, the water level steam volume double weight and the water level, the steam amount, and the water supply amount can be used according to the situation. Control System.
Deaerator pressure and water level adjustment: The deaerator part adopts single impulse control scheme and single loop PID regulation.
Monitoring management system:
The above control system is generally controlled by PLC or other hardware system, and the following functions are to be completed in the upper computer:
Real-time accurate detection of boiler operating parameters: In order to fully grasp the operating conditions of the entire system, the monitoring system will monitor and collect boiler-related process parameters, electrical parameters, and equipment operating status in real time. The system has a rich graphics library, which can be used to display the boiler's device graphics along with the relevant operating parameters on the screen; in addition, the parameters can be displayed in the form of lists or groups.
Comprehensive analysis and timely issue of control instructions: Based on the monitored boiler operating data, the monitoring system issues control commands in accordance with the set control strategy to regulate the operation of the boiler system equipment to ensure efficient and reliable operation of the boiler.
Diagnostic fault and alarm management: The main control center can display, manage and transmit various alarm signals of boiler operation, thus greatly improving the safety explosion-proof and safe operation level of the boiler. At the same time, the file management of the alarm can make the owner know all kinds of problems and weaknesses of the boiler operation. In order to ensure safe and reliable operation of the boiler system, the monitoring system will perform fault diagnosis based on the monitored parameters. Once a fault occurs, the monitoring system will display the alarm point on the operator's screen in time. The alarm-related display function associates the user-defined display with each point so that when an alarm occurs, the operator can immediately access the details of the alarm point and follow the recommended emergency actions.

History running parameters: The real-time database of the monitoring system will maintain a history of boiler operating parameters, in addition to the monitoring system. A dedicated alarm event log is provided to record alarm/event information and operator changes. The historical data can be displayed as an instantaneous value or as an average value over a certain period of time, depending on the operator's requirements. Historical data can be displayed in a variety of ways, such as curves, specific graphics, reports, etc. In addition, historical data can also be applied by a variety of network-based applications.

Calculate operating parameters: Some operating parameters of the boiler operation cannot be directly measured, such as annual operating load, steam consumption, water replenishment, condensate return, and cumulative operating time of the equipment. The monitoring system provides a rich set of standard processing algorithms that are calculated based on the measured operating parameters.