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ACS TP of the ball mills "ШБМ 287/410" of the boiler "БКЗ 160–100 ПТ"

Company: «Kramatorskteploenergo» Ltd. Work: Automation of the loading of two ball mills "ШБМ 287\410" Start: July 2009 Finish: August 2010 Performers: Belousov E.M. - engineering manager; Sadovoi A.V. - scientific adviser; Savochenko R.A. - development of the PLC firmware, programming of the PLC and top-level; Lysenko M.S. - top-level programming; Zaichuk E.N. - development of algorithms; Birukov V.V., Lesov L.I. - control cabinet's design.

1. Automation object

On balance of the "Kramatorskteploenergo" Ltd. there is the heat electropower station composed of four working boilers "БКЗ 160–100 ПТ" (6, 7, 8 and 9). Boilers produce steam with pressure of 100 kg/cm2, with a nominal capacity of 160 t/h on the single boiler. The fuel of the boilers is natural gas and coal dust. Currently much attention is paid to the using of coal in steam producing because of high gas prices. The 7, 8 and 9 boilers have a working system of dust-training, which provides boiler with dust.

The process of dust-training includes: workshop of coal-preparation, the carrier of coal to the bunkers of the ball mills, two ball mills and dust bunkers.The subject of this project is the automatic control of loading process of the ball mills.

The company uses ball mills "ШБМ 287\410". Functional scheme of a ball mill with automation components is shown in Figure 1.

Fig. 1. Functional scheme of a ball mill

2. ACS TP (Automatic Control System of Technological Process)

Structure scheme of the ACS TP is shown on the Figure 2, composite nodes of which are two controllers cabinets "PLC 1", "PLC 2" and two operator workstations "АРМ 1", "АРМ 2".

Fig. 2. Structure scheme of the ACS TP.

Based on the structure, ACS TP consists of the automation object - mill, controllers ("PLC 1" and "PLC 2"), as well as of two workstations ("АРМ 1" and "АРМ 2").

Each controller operates independently with the mills of separate boiler. For example, the "PLC 1" controller controls the mills of the boiler 7, and "PLC 2" - with the mills of the boiler 9.

The technological process data are concentrated and presented on the workstations. Each workstation presents the TP data of all boilers. With each other workstations are connected in redundant scheme that prevents data loss at the time of stopping one of the workstations. In order to optimize the load on the controller the inquiry of controllers makes only one workstation, while another workstation is receiving data from the main one. The main workstation is "АРМ 1", which performs a direct inquiry of controllers. In case of failure of the "АРМ 1" the controller's inquiry performs "АРМ 2", and makes it until the restoration of an "АРМ 1". In the process of restoration after failure of the workstation the synchronization of archives depths up to 1 hour is made. Restoration of the archives for the longer time interval is made simultaneously with access to these archives.

2.1. PLC

As a programmable logic controller it is used in the PLC LP-8781 of ICP DAS company of LinPAC family. The industrial controller of this family is the first product built on the x86-compatible processor, the previous controllers of this family were based on ARM processor. Besides the x86 processors these controllers have significant resources of memory and disk space.

A special feature of the technological process of this project is the availability of specific requirements to the resources and functions of the controller having the small set of parameters. Moreover, the decisive factor is the limited funding. All these requirements are satisfied by a LP-8x81 family of controllers:

• relatively low price;
• high performance for PLC;
• architectural and programmatic openness of the PLC;
• industrial design and extended temperature range.

PLC (Fig. 3) is structurally made in a modular manner, where the modules are installed in the rack. Rack is combined with a processor module and can have 1, 3 or 7 slots for expansion modules. Expansion modules can be of two types, namely modules in parallel and serial bus. Modules on the parallel bus (I-8x) are fast. Modules on the serial bus (I-87x) are installed on the bus of RS-485 interface and operate at a speed of 115000 bps on the DCON protocol. In addition to modules directly into the rack the controller can be expanded with additional racks with modules on the serial bus (I-87x) through the serial interfaces of the processor.

Fig. 3. PLC of LP-8x81 family.

ACS TP capacity for one boiler is: 18AI, 2AO, 10DI, 16DO. Hence the controller is required with the number of at least 6 expansion slots. Proceeding from this the LP-8781 controller is selected and the following modules for connection of external signals:

For the UPS connection the serial interface COM2 of controller is used.

There are some important features of controllers' adjustment:

• It was built the latest version of driver UPS nut-2.4.1.
• To ensure the stable and uniform work of the serial interfaces in the mode of real time priorities using it was necessary to set priority 20 of the real time for the kernel thread "events / 0". Setting the priority is made in the first run of the procedure of inquiry the UPS of the runtime of controller on OpenSCADA by the following code:

• The 5 priority of the real time is set for incoming transports, in order to improve the uniformity and reactivity in response to requests from the top level.

Controllers are mounted in the cabinet with the size 2000x800x400, which includes machines, terminal blocks, relays, and UPS separate for each boiler.

2.2. Workstation

Workstations of the operator are based on the office PC with the following configuration:

Both the system units are placed in the cabinet of the operator's table. The operator's table is equipped with two separate display of workstations and mouses. Cabinet with system units was closed with doors on both sides. On the doors the filters are installed, and one of them has fan. Despite of the presence of the fan and because of the large saturation of the room with coal dust the overheating of the system units and failures took place. To solve this problem, it was optimized the air moving in the cabinet, and also lowered the frequency of workstation's processors from 2500 to 1600 MHz.

At workstations was installed the system software ALTLinux 5.1 and SCADA-system OpenSCADA 0.6.4.2.

The following activities on the system-wide configuration were done:

• The time synchronization was configured of "PLC 1", "PLC 2" and "AРM 2" with "АРМ 1".
• An account of the operator "operator" with password "123456" was created.
• An automatic loading of the working interface on behalf of the operator and the launch of the OpenSCADA with the ball mills ACS TP project was configured.
• KDE desktop environment is configured to eliminate unnecessary functions when working with dialog boxes and excluding the possibility of closure of the operator interface be the mouse.

3. Algorithms

The control algorithms of the ball mills are quite complex, due to the following factors:

• The use of indirect mechanisms to obtain the values of the level of coal in the mill.
• Accounting of different ways of control the loading of the mill, from the direct regulation of temperature of dusty mixture at the outlet from the mill to control the loading on the calculation of the coal level inside the mill.

Using the algorithms the programs of the controller designed for loading control of ball mills were created. In the algorithms and programs the analog and digital signals coming from the inputs (to output) of analog and discrete modules of the controller, the signals, generated by the workstation, and the intermediate signals, generated on their basis, were used.

Programs are implemented in user programming languages, of the OpenSCADA system. Block schemes are implemented in the environment of the DAQ.BlockCalc module, but the realization of the blocks itself and templates of parameters - on the JavaLikeCalc language of the DAQ.JavaLikeCalc module of the OpenSCADA system.

3.1. Pre-processing

For pre-processing of analog signals after ADC of the analog input module of the controller the template of parameters was created with the following functions:

• detecting of uncertainty (the break, out of range of acceptable values);
• corrections using the calibration coefficients;
• filtrations;
• bring to the engineering (technological) units;
• formation of the alarm bits for violations of borders;
• simulation of analog input as with the built-in function, and with the external input, which can be used to connect the signal model.

Based on this template the additional templates were created:

• template of the parameter of manual input, with the additional function of input the value;
• template of the universal PID parameter with the reflection of its own attributes of the analog and pulsed regulator.

For the grouping and processing the discrete signals the template of a discrete parameter was created, which allows you to:

• combine two digital inputs and three digital outputs in the configuration of pumps and valves.

3.2. General algorithms

Common algorithms are summarized in two block schemes for each mill. The first block scheme contains the contours of analog regulators and work with a period of 500ms. The second block scheme contains the contours of pulsed regulators and operates with a period of 100 msс.

4. User interface

User Interface of the ACS of the BM(ball mills) contains five signal objects (Fig.4): four, by one for each mill 7A, 7B, 9A, 9B and the one signal object "Diagnostics" for the diagnostic of the system. Each signal object contains one mnemonic scheme, two graphics groups, contours group, group of the overview frames, and four documents. From each mnemonic scheme of the mill you can call two dialogues: "Сalibration of the mill level" and "Setting the optimization algorithms". Signal object "Diagnostics" contains one mnemonic scheme, a graphics group and one document.

Fig. 4. General view of the window of user interface.

Fig. 4 shows specified areas of video frame:

1. panel of signal objects;
2. selection the display type panel;
3. control panel;
4. workspace display;
5. status bar with the tools.

4.1. Signal object of the mill

Fig. 5. Mnemonic scheme of the signal object of the mill.

Fig. 6. Graphics group 1 of the signal object of the mill.

Fig. 7. Graphics group 2 of the signal object of the mill

Fig. 8. Contours group of the signal object of the mill.

Fig. 9. Group of the overview frames of the signal object of the mill.

Fig. 10. The document "List of actions" of the signal object of the mill.

Fig. 11. The document "Alarms report" of the signal object of the mill.

Fig. 12. The document "Diagnostic report" of the signal object of the mill.

Fig. 13. The document "Operator's report" of the signal object of the mill.

Fig. 14. Dialog "Level calibration" of the signal object of the mill.

Fig. 15. Dialog "Setting the optimization algorithms" of the signal object of the mill.

4.2. Signal object "Diagnostics"

Fig. 16. Mnemonic scheme of the signal object "Diagnostics".

Fig. 17. Graphics group of the signal object "Diagnostics".

Рис. 18. Document of the signal object "Diagnostics".

4.3. General-system

Fig. 19. Group of result graphics.

5. Results

As a result of this work the industrial control system was obtained, the result of which is the savings of coal and electricity up 30%, due to the uniformity of the load of the mills.

In Figures 20 and 21 the diagrams of mill control on load are shown, and in the Figures 22 and 23 - on the temperature of dust-air mixture after the mill.

Fig. 20. The control of the mill on load.

Fig. 21. The control of the mill on load in the regulator's control panel.

Fig. 22. The control of the mill on the temperature.

Fig. 23. The control of the mill on the temperature in the regulator's control panel.

6. Economic effect

As a result of the work a significant economic effect is received, the calculation and the nature of which is held in the table below. The effect is calculated by the customer based on actual statistical data. In the period from 06/21/2010 to 06/30/2010 the work of mills was made in the manual mode and without ACS. In the period from 08/21/2010 to 08/30/2010 the ACS SHBM worked in the automatic mode.

The act of SAU SHBM pilot tests by the customer, describing the economic effect can be downloaded here.

7. Links