„SEVER“ heating plant, Control system of gas fired water type boiler VK6 58 MW

The consortium of companies: „Remming“ (mechanical works), „Best izgradnja“ (civil works) and „Mikro Kontrol“ ( electrical and control system works), within the Serbian heating plants rehabilitation project financed by Federal Republic of Germany Government through KfW bank, performed building contruction, boiler and pipelines manufacture and installation, and control system realization and its integration into existing district plant heating system of the Novi Sad city.


Within the project, it was necessary to build a new facility beside the existing one at the „Sever“ heating plant location, because of the new boiler's large size and its vertical construction (10.4m height, 10m width and 25m length) . Apart from control system electric installation, it was necessary to provide common building electric installation (lighting, video surveillance, fire detection). 
Combustion device comprises two burners designed for natural gas combustion, gas fittings and independent burner management control system (BMS); the burners are located at two platforms (height  2.2m and 5m); the BMS is based on fail-safe control system S7-315F CPU, and designed according to international standards which regulate safety systems in process industry (IEC 61508 and IEC 61511).The BMS has to control burner firing, to regulate the load (by changing air – fuel ratio), to monitor critical process parameters; it communicates with supervising boiler control system (BCS) through Profibus DP, and exchanges all the necessary informations (start conditions, interlocks, load reference value, alarms).

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The hot water boiler 58MW is designed, manufactured, installed and put into operation according to directives which regulate pressure water-type boiler installations (ISO 12952); technical requests that had to be fulfilled were:
1. air emission limit values (according to relevant directives in Republic of Serbia ):
SO2: 35mg/m3
NOx: 110mg/m3
CO: 80mg/m3
dust: 5mg/m3
2. boiler thermal power:
nominal load: 58MW
minimal load: 5.8MW
3. efficiency at 100% of load: 98%
4. boiler process parameters:
temperature mode: 150oC / 70oC
pressure drop through boiler: 1.32bar
nominal water flow rate: 660 m3/h

The valves with electric motor actuators, ON/OFF or continuous control, are mounted on hot water and return water pipelines, on the air and flue gas ducts. A fan driven by a 200kW electric motor has been installed on the burner air supply. Another fan, driven by a 4kW motor, has been installed on flue gas circulation duct, in order to regulate flue gas Nox ratio. Both motors are regulated by frequency inverters. 

The process signals are acquired through followng transmitters:
  • hot water and return water (before and after ECO) pressure and temperature
  • flue gas  pressure and temperature (before and after ECO, after LUVO)
  • fresh air pressure and temperature
  • flue gas oxygen ratio (O2) 
  • neutralisation water pH ratio
  • water flow at return pipeline, combined with heating power measuring device (energy calculator)

The control system includes two regulating loops:
  • burner load regulating loop, with possible choice of two process values: heat water temperature (boiler outlet), or district heating pipeline temperature; the choice is made by SCADA operator
  • fresh air (burner supply duct) temperature regulation; the actuator is regulating valve on the duct 

The control system has to provide that VK6 boiler works independently from Novi Sad district heating system (CSU), i.e. it has to generate heating energy according to „Sever“ SCADA operator request; the alternative mode of work is that control system receives heating energy reference from CSU, according to it's complex mathematical model based on heating network configuration.

„Mikro Kontrol“ designed, manufactured and connected following distribution panels:
The control system panel, consisting of PLC panel (in boiler room) and HMI panel (in operator room)
common consumption distribution panels
field equipment local panels

For the new facility „Mikro Kontrol“ designed, mounted cable trays, laid and connected both signal cables and power cables; the lighting, video surveillance and fire detection equipment  were mounted and connected,; sensors   were delivered and connected both for BMS and BCS).
For the new gas pipeline, which transports the gas to the new facility, „Mikro Kontrol“ performed cathodic protection and potential equalization.
All works done by  „Mikro Kontrol“ are completed with necessary test reports and approvals.

Control system is based on Omron PLC CJ2 family, 10“ HMI, integrated in existing Wonderware SCADA monitoring system of the „Sever“ heating plant; besides, it was necessary to integrate VK6 control system into Novi Sad district heating CSU, which meant that these data had to be visualized, logged, reported  and incorporated in Information System of Novi Sad district heating system.

During control system realization, Mikro Kontrol engaged following human resources:
  • detailed and as-built design: one engineer, 45 days duration
  • control panels manufacturing, wiring and testing: four electricians, 20 days  duration
  • cable and cable trays installation, field eq. connecting: four electricians, 30 days  duration
  • PLC and SCADA application programming: three engineers, 60 days duration


Vase Pelagica 30
11000 Belgrade, Serbia
+381 (0)11 3699 080
+381 (0)11 3699 939
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