Automation of boiler plants: description, device and circuit

To regulate and optimize the functioning of the boiler units, technical means began to be used even at the initial stages of automation of industry and production. Today's level of development of this direction makes it possible to significantly increase the profitability and reliability of boiler equipment, to ensure the safety and intellectualization of the work of maintenance personnel.

Objectives and objectives

Modern boiler automation systems can guarantee trouble-free and efficient operation of equipment without direct operator intervention. The functions of a person are reduced to online monitoring of the operability and parameters of the entire set of devices. Automation of boiler rooms solves the following tasks:

• Automatic starting and stopping of boiler units.
• Boiler power control (cascade control) according to the preset initial settings.
• Control of feeding pumps, control of coolant levels in the working and consumer circuits.
• Emergency stop and activation of signaling devices, if the operating values of the system exceed the specified limits.

Automation object

Boiler equipment as an object of regulation is a complex dynamic system with a multitude of interrelated input and output parameters. Automation of boiler houses is complicated by the fact that in steam units there are very high rates of flow of technological processes. The main regulated values include:

• Flow and pressure of the coolant (water or steam);
• Discharge in the furnace;
• Level in the nutrient reservoir;
• In recent years, increased environmental requirements are imposed on the quality of the fuel mixture being prepared and, as a consequence, on the temperature and composition of the smoke products.

Levels of automation

The degree of automation is specified when designing the boiler room or when overhauling / replacing equipment. It can lie in the range from manual control according to the testimony instruments to fully automatic control according to weather-dependent algorithms. The level of automation is primarily determined by the purpose, capacity and functional features of the operation of the equipment.

Modern automation of boiler house operation implies a comprehensive approach - the subsystems for monitoring and regulating individual technological processes are combined into a single network with functional group management.

General structure

Automation of boiler houses is built on a two-level control scheme. The lower (field) level includes local automation devices based on programmable microcontrollers that implement technical protection and interlocking, adjustment and modification of parameters, primary converters of physical quantities. The equipment intended for transformation, coding and transmission of information data is also included here.

The upper level can be represented as a graphic terminal built into the control cabinet or the operator's automated workstation on the basis of a personal computer. All information from the lower level microcontrollers and sensors of the system is displayed here, and operative commands, adjustments and settings are input. In addition to dispatching the process, tasks of optimizing modes, diagnosing technical condition, analyzing economic indicators, archiving and storing data are solved. If necessary, the information is transferred to the general enterprise management system (MRP / ERP) or to the settlement.

Automation of boiler equipment

The modern market is widely represented both by separate devices and devices, and by sets of automation of domestic and imported production for steam and hot water boilers. The means of automation include:

• Control equipment for ignition and presence of a flame, triggering and controlling the combustion of fuel in the combustion chamber of the boiler;
• Specialized sensors (tension gauges, temperature, pressure, gas analyzers, etc.);
• Actuators (solenoid valves, relays, servo drives, frequency converters);
• Control panels for boilers and boiler equipment (consoles, sensory mnemonic schemes);
• Switching cabinets, communication lines and power supply.

When choosing the technical means of control and monitoring, the most attention should be paid to the automation of safety, which excludes the occurrence of emergency and emergency situations.

Subsystems and functions

Any scheme of boiler house automation includes subsystems for control, regulation and protection. Regulation is carried out by maintaining the optimum combustion mode by setting the discharge in the furnace, the flow of primary air and the parameters of the coolant (temperature, pressure, flow). The monitoring subsystem displays the actual data on the functioning of the equipment on the human-machine interface. Protection devices guarantee the prevention of emergency situations in the event of a violation of normal operating conditions, the supply of a light or sound signal or the shutdown of the boiler units with a fixation of the cause (on a graphical display, mnemonic diagram, shield).

Communication protocols

Automation of boiler plants based on microcontrollers minimizes the use of relay circuits and control lines in the functional scheme . For communication between the upper and lower levels of the control system, the transfer of information between sensors and controllers, an industrial network with a certain interface and data transfer protocol is used to translate commands to actuators. Modbus and Profibus standards are most widely used. They are compatible with the bulk of equipment used to automate heat supply facilities. They are distinguished by high indicators of reliability of information transfer, simple and understandable principles of functioning.

Energy-saving and social effects of automation

Automation of boiler houses completely excludes the possibility of accidents with the destruction of capital structures, the death of service personnel. The automated control system is capable of ensuring the normal functioning of the equipment around the clock, minimizing the influence of the human factor.

In light of the continuous increase in prices for fuel resources, the energy saving effect of automation is not the least important. Savings of natural gas, reaching up to 25% for a heating season, are provided by:

• Optimal ratio of "gas / air" in the fuel mixture in all operating modes of the boiler room, correction for the level of oxygen in the combustion products;
• The possibility of individual adjustment of not only boilers, but also gas burners;
• Regulation not only of the temperature and pressure of the coolant at the inlet and outlet of the boilers, but also taking into account the environmental parameters (weather-dependent technologies).

In addition, automation allows the implementation of energy-efficient heating algorithm for non-residential premises or buildings not used on weekends and holidays.