Distributed Measurement and Control System for 0.5 MW Combustion Chamber

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"A 0,5 MWt test stand for combustion of pulverized fuels was designed and constructed by the Thermal Processes Department at the Institute of Power Engineering. "

- Tomasz Wieczorek , SARW S.C.

The Challenge:
A 0,5 MWt test stand for combustion of pulverized fuels was designed and constructed by the Thermal Processes Department at the Institute of Power Engineering. The variety of studied phenomena (including low emission combustion, combustion in oxygen-enriched atmosphere, simulated exhaust gas recirculation using synthetic gas mixtures, NOx and SOx¬ reduction using catalytic and non-catalytic methods) and the use of fuels that need to be supplied in different ways (various types of coal and biomass, their mixtures, syngas from biomass and waste fuel gasification) imposed a modular design of the stand. This also resulted in the need for a distributed control system. The stand, its actuators and support systems are spread across a few rooms and outside the building.

The Solution:
A distributed control system was developed by SARW, based on the needs of research staff, the stand documentation and correlations between the support systems. The system uses the cRio platform for control and the PXI platform for data acquisition and archiving.

Author(s):
Tomasz Wieczorek - SARW S.C.

The main component of the stand is the cylindrical, horizontal combustion chamber. Its inner walls are coated with an insulating material, and the outer walls are cooled with air. Additionally, the front wall is cooled using water. A pulverized coal burner is mounted axially on the front wall. Primary and secondary air is supplied to the burner (250 and 500 Nm3/h max. respectively). Pulverized fuel (coal, biomass, waste) is transported to the primary air line by a feeder. When using pure biomass as a fuel, an additional dedicated feeder is used with its own container. In 2008 through 2009 the stand was modified for oxy-fuel combustion research. Pipelines were built to transport oxygen and carbon dioxide from cryogenic tanks to the stand. A modular extension was added to the combustion chamber, allowing for further research in various methods of  NOx and SOx¬ reduction. The stand was then equipped with a lean gas burner developed by the Institute, and connected a 150 kW gasifier. In 2013 another module was added to the combustion chamber, this time allowing for PIV and LIF measurement methods to be used during tests.

The control and measurement system needed to handle a large amount of time stamped data from a few hundred measurement devices spread across the stand and its support systems (steam generators, coolant temperature control, detection of hazardous gases).

The Solution

A distributed control system was developed by SARW, based on the needs of research staff, the stand documentation and correlations between the support systems. The system uses the cRIO platform for control and the PXI platform for data acquisition and archiving.

Close cooperation with the technical division of the Thermal Processes Department allowed the development of interface functionalities suitable for the research conducted at the stand. An open design of the system was proposed, taking into account the fact that research stands are frequently modified. Both hardware and software in the system are modular, and the control and measurement subsystems are independent.

Control subsystems are assigned to segments of the stand responsible for supplying particular fuels and providing specified conditions in the combustion chamber – pressure (inlet and exhaust), temperature (heating) and supplying gases for optimization of the combustion process. These tasks are handled by the cRIO platform, which is a part of the system that is not subject to modifications during subsequent tests. Changes to the cRIO unit will be restricted to adding new control loops and modules if needed.

Information about the status of control tasks is passed to the PXI-based data acquisition and archiving unit.  The PXI data acquisition modules collect measurements directly from sensors at the stand and from the support systems (via Modbus RTU and Modbus TCP/IP).

Aside from communication protocols commonly used in data acquisition and control, LabVIEW allows implementing custom ASCII-based interfaces for digital data communication (e. g. for gas analyzers and weighing scales). It enabled direct communication with the devices, eliminating conversion errors which might have occurred if DACs/ADCs with the devices’ analog inputs/outputs had been used instead. Wiring costs have also been reduced.

The user interface was designed for easy reconfiguration, optimized operation and quick access to measurement data by the research staff. With these goals in mind the following were created:

  • Control interface – a stand-alone application that enables control of all the actuators
  • Research interface – an application that contains a visualization of the stand and enables creating reports and configuring the devices. It can be used by an unlimited number of researchers simultaneously.

The user interface was designed so that it can be used by multiple people simultaneously. Additionally, each data acquisition channel can be configured individually including its description, processing settings and the way it is presented in the application (visualization, graphs). Screenshots from the application are presented below.

Any changes in the mentioned parameters are instantly presented in all the running instances of the application. Thanks to this, unified interpretation of the measurements by all users of the system is achieved.

Author Information:
Tomasz Wieczorek
SARW S.C.
Poland
biuro@sarw.pl

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