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11.01.2011 14:40 Age: 6 yrs

By: Roman Savochenko

The automatic control system (ACS) of the ball mill's load.

The ACS BM (ACS) is designed to provide centralized monitoring and automatic process control of coal grinding in ball mills at the normal technological process, as well as at start and stop conditions (routine and emergency) of the boilers of the thermal power plants based on coal.

Supplier: "DІYA" Ltd.


The overall structural diagram of the cabinet ACS mills.

ACS Structure

PURPOSE

  1. Creating the conditions to achieve maximum productivity of the ball mills (for example, "BM 287/410").

  2. Reducing unit cost of electricity on the mechanisms of pulverization.

  3. Increasing the efficiency of the boiler due to stabilization of the combustion process of more homogeneous fuel and to reduce of its mechanical underburning.

  4. Reducing of the maintenance costs and costs for routine repairs of pulverization equipment.

FUNCTION

ACS provides the following functions:

  • Remote automatic control of loading volume of coal in a rotating drum of the mill, the temperature of hot air at the entrance to the mill, the temperature of dust/air mixtures after the mill, the drop of pressure in the mill, depression before the mill and control of actuators.

  • Automatic adjustment of the productivity of supply of raw coal by the coal load of the mill's drum with a restriction on the deviation of the temperature of dust/air mixtures at the output of the mill.

  • Automatic dust/air mixture's temperature stabilization at the output of the mill.

  • Stabilization of the depression of hot air at the entrance to the mill.

  • Protection of technological equipment of raw coal grinding:

    • stop of the raw coal feeder according to the setpoints of the technological parameters;

    • stop of the raw coal feeder according to the alarm signals.

STRUCTURE AND CONFIGURATION OF TECHNICAL EQUIPMENT

  • PLC control cabinet with the options:

    • frequency converters of the raw coal feeder drives of the ball mills;

    • direct pulse output to the feeder's actuator;

    • direct analog output to the feeder's actuator.

  • Software for integration into the automation of the enterprise or at the engineering workstations (AWP's) of the boilers' engineers:

    • providing the ACS data via standard protocols and interfaces;

    • providing the Web-interface to the ACS;

    • specialized engineering workstations  of the boilers' engineers;

    • providing data on the local touch panel.

Generalized block diagram of ACS is shown in Figure 1. The composition of ACS, presented in Figure 1, includes: PLC control cabinet with touch panel for the local control, two operator's workstations AWP 1 and AWP 2, and software for the integration into automation of the enterprise.

 

Fig. 1: Block diagram of ACS.

 

 PLC control cabinet can be supplied on request in one of the following options:

  • with frequency-controlled drive of the the raw coal feeder (the frequency converters are built in the cabinet);

  • with the direct pulse or analog output to the actuator of the feeder, for example, to control the rotation angle of the knife;

  • with the possibility of local control through local touch screen;

  • with the possibility of integration into existing process control system via standard protocols and communication interfaces;

  • with the providing of the Web-interface to the ACS.

For optimal and reliable operation the AWPs are supplied with the following software: "ALTLinux" distro of the OS Linux and SCADA-system "OpenSCADA".

Control cabinet includes: PLC controllers, UPS, automatic machines, terminal blocks, relays, lamp to illuminate during the routine work.

The ACS can control the load of the mill by the specific algorithm, that takes into account the interrelated parameters, such as calculating the volume of the coal loading in the mill, and the temperature of dust-air mixture at the output from the mill.

Measuring of the volume of load of the mill's drum is made with the help of vibration analysis by a specific algorithm in real time.

MAIN RESULTS OF THE ACS ADOPTION AT "KRAMATORSKTEPLOENERGO" LTD

As a result of the ACS adoption it was provided:

  • Continuous monitoring and visualization on the screen workstations in the form of graphics: the volume of the coal loading in the drum of the mill, the temperature of dust-air mixture after the mill, depression before the mill and other parameters.

  • Automatic control of feeder's performance with frequency-controlled feeders' drives on specific algorithms.

  • Automatic temperature stabilization of the dust-air mixture at the output from the mill.

  • Automatic stabilization of depression of hot air at the entrance to the mill.

Effectiveness of ACS adoption is expressed in the follows:

  • Through the work of a single mill in a continuously lit with automatic maintenance of the required amount of coal in the drum of the mill it is provided the rated load of the boiler during the second mill was stopped for 16 hours a day, reducing to 30% the specific energy consumption for grinding of coal. In addition, it was eliminated overflow (obstruction) of mill and mills idle, and it is reduced the load on the engineers of boilers associated with continuous switching on and off mills, which took place before the ACS adoption.

  • By reducing the thinness of coal grinding and keep its value constant it was reduced the content of combustibles in ash and increase the energy efficiency of the boiler.

  • Payback of the ACS is 0.6 years.

OPTIONS OF SUPPLY

Order code: DM 1[.F][.SCR][.485][.OPC][.WEB][.ARM][.ARM2][.ACS]

Code

Description

DM 1

The basic configuration consists of:

  • ACS cabinet;

  • connection via Ethernet;

  • ModBus/TCP and ModBus/UDP protocols.

F[N]

Optional inclusion of frequency converters in the specified number N (1-4).

SCR

Optional inclusion of a local control panel.

485

Option to enable support for the RS485 interface and ModBus/RTU, ModBus/ASCII protocols. The module of OpenSCADA system — «Transport.Serial».

OPC

Option to enable support for protocol OPC UA. The module of OpenSCADA system — «DAQ.OPC_UA».

WEB

Option to include support for Web-based ACS control interface. The module of OpenSCADA system — «UI.WebVision».

ARM

Workstation.

ARM2

Two redundant workstations.

ACS[N]

Accelerometer, vibration sensor in the specified number N (1-4).


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