Yudian Products' Application in 35t/h Boiler Production Control

Abstract : This paper describes the application of Yudian regulator and manipulator in production control of 35t/h boiler in terms of engineering overview, control process requirements, control design, application notes, and use effects in combination with a large 35 t/h boiler modification project. . Practice has proved that Yudian products provide a good automation guarantee for the stable operation of the boiler.

Key words: 35t/h boiler, drum level control, desuperheated water temperature control

I. Project Overview

The 35t/h boiler of our steel plant was rebuilt in June 2015 and resumed production two months later. The boiler mainly provides steam power with certain temperature and pressure for the steam turbine, and drives the axial fan to supply air for the blast furnace. The boiler overhaul automation equipment was correspondingly transformed. As the key instrument for boiler production control, Xiamen Yudian's AI-808P regulator and AI-708J manipulator were selected.

Second, control process requirements

The boiler is an important equipment for metallurgical enterprises and is a high-temperature and high-pressure vessel that is managed by the first-level safety license. In the boiler field control, each parameter is related to the safe operation of the boiler, of which the drum water level detection and control, desuperheated water temperature control is the most important.

Regarding the adjustment of the water level of the steam drum: If the water level of the steam drum is too high, steam will be brought into the water and the steam turbine blades will be damaged. If the water level of the steam drum is too low, the boiler may be burned or may explode. Therefore, the boiler production process requires that the drum water level must be maintained within the range of 0±15mm.

About desuperheating water temperature regulation: The desuperheating water regulates the flow of fluid in the valve through the crooked channel to control the flow of desuperheated water required for the boiler main steam and reheat steam temperature. The purpose is to consume energy to reduce the flow rate and prevent the liquid from cavitation. The temperature of desuperheated water must be controlled in the range of 350±8°C.

Specific requirements for regulators and controllers:

(1) The adjustment is stable and no oscillation can occur.

(2) Rapid response, no signal hysteresis.

(3) Feature-rich, set Dacheng, including all the necessary elements of PID function.

(4) Friendly man-machine interface, flexible operation and convenient use.

(5) Convenient communication with PLC or other instruments.

(6) Realize bumpless hand/automatic switching.

Third, control design

1. AI-808P regulator features: Adopt advanced AI artificial intelligence adjustment algorithm, no overshoot, with self-tuning function; input adopts digital correction system; advanced modular structure, provides rich output specifications, can meet various complexities Industrial site requirements; user-friendly operation design.

2, AI-708J operator features: Integrated communicator and servo amplifier function, and the PLC system is well-matched; can achieve automatic two-way non-disturbance hand switch, in particular, automatic switching slow-change function makes the control more stable and convenient, Simplify the preparation of the PLC control program; complete functions, panel display at a glance; modular structure design, multiple types of signal connection; stable quality, reliable operation, anti-jamming performance in line with electromagnetic compatibility (EMC) requirements, convenient parameter lock The function greatly improves the speed of parameter modification and avoids the important parameter being mistakenly modified; the operation is simple and convenient.

3. For small boilers, single-loop PID control is often used for the control of the drum water level and temperature control of desuperheated water. Before the big modification, the above two parameters were adjusted using a small PLC to achieve the PID adjustment function. Because the operation effect was not very satisfactory, the technicians decided to use Xiamen Yudian's regulator and manipulator to constitute an independent regulation system to replace the PLC to achieve regulation control. The electrical wiring diagrams of the regulators, operators, and electric actuators used in the two control systems are shown in Figures 1 and 2:

Figure 1 Drum water level regulation control wiring diagram

Fig. 2 Temperature regulation control circuit for desuperheated water

Fourth, application instructions

1. The main screen of the boiler soda system is shown in Figure 3:

Figure 3 Main screen of the boiler soda system

2. Number of operators: This boiler uses two AI-808P regulators and two AI-708J operators.

3, application description:

(1) The above 4 regulators and operators are installed on the operating table of the boiler duty room, in parallel with the CRT of the PLC operation station. In this way, personnel at the post can monitor the operation of the boiler while easily adjusting the AI-808P and AI-708J.

(2) Automatically adjusting the valve: manually set the drum water level value and desuperheated water temperature value on the regulator, the regulator calculates and outputs to the operator, the operator then outputs the 220VAC forward/reverse signal to the electric actuator to control separately Water supply and desuperheating water electric actuator opening. At this point the operator is placed in the "automatic" state.

(3) Manual adjustment of the valve: The operator is placed in the "manual" state, and the opening degree of the valve is adjusted by the switch button on the operator. At this point the system is off the regulator.

(4) Since the instrument is a maintenance-free instrument that uses auto-zeroing and digital calibration technology, it does not require calibration and maintenance. When there is a problem of out-of-tolerance, the problem can be solved by cleaning and drying the inside of the instrument. This is a unique feature compared with other instruments. It can greatly reduce instrument failures and processing time, and increase the operating rate of the instrument. It is therefore well received by field technicians.

(5) AI-808P regulator adopts artificial intelligence adjustment algorithm, uses fuzzy rules for PID adjustment, has some characteristics of self-learning and memory controlled objects in the adjustment, with no overshoot, high precision, simple parameter determination, etc. These features have added a lot to the already complex and traditional systems. After nearly half a month of running-in, the regulating system gradually became stable, which significantly reduced the workload of the operator and achieved the intended purpose of retrofitting.

(6) The universal input of the regulator provides great convenience for a variety of applications on the industrial site, making the work on device selection, product interchange, and emergency replacement of spare parts very simple and quick.

(7) The AI-708J combines the functions of the operator and servo amplifier to reduce installation space, reduce wiring, reduce maintenance, reduce failure rate, and increase equipment operation rate.

Fifth, the use of effects

The 35t/h boiler has undergone major modification operations for more than a year. The AI-808P regulator and AI-708J operator have been operating stably and reliably. The control indicators fully meet the requirements of the production process. The drum water level is maintained at 0±15mm. The warm water temperature is maintained at 350±8°C, and its outstanding performance provides a good automation guarantee for boiler safety production.

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I Features:

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II.Main model and spec

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