Selection of control scheme for flue gas purification system: PLC or DCS
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For new projects, the flue gas purification system (bag filter dust removal, common ash conveying system, lime slurry preparation system, activated carbon injection system, etc.) is controlled by a DCS; a DCS cabinet is installed on-site, and communication with the DCS main station is established via fiber optics. There are also the field devices; process control is carried out by PLCs, which in turn communicate with the DCS. Could the engineers please explain the advantages and disadvantages of these two options? Setting cost considerations aside, DCS sub-station control seems advantageous for making subsequent modifications – what other benefits are there?
Do you all take a break at noon? ? Take it on myself
If the field equipment is not specialized equipment (with the control system provided by the equipment manufacturer), it can be controlled directly by the DCS.
For flue gas treatment, there are many analog signals, and it is possible to use DCS for all of them; this ensures that spare parts are interchangeable, and maintenance personnel do not need to acquire extensive technical knowledge. Communication between DCS systems from the same manufacturer is completely seamless.
For this type of equipment, an on-site PLC is sufficient; only a few key points need to be connected to the DCS in order to reduce unnecessary investment and waste
For the several flue gas ventilation control systems I worked on, DCS was used in those installations, and they were located in pharmaceutical factories, chemical plants, and steel mills.
Will adding to an existing DCS system increase CPU load?
The last edit to this post was made by gdjj2001 on 2015-11-18 at 11:05. Setting aside cost considerations and future maintenance needs, using a DCS remote cabinet is the best option; it makes it very convenient to make changes to equipment, add new equipment or programs in the future. Fault resolution is also faster, and field staff will certainly prefer this solution. This solution has 2 disadvantages: 1) the equipment cost will definitely be higher, 2) it takes more time to program it
There are many analog signals and the calculations are complex; choose DCS； For digital signals, a PLC is often the preferred choice.
Of course, it’s more convenient to use DCS for everything; it’s important to consider the cost~~~
Now, the functional boundaries between DCS and PLCs have become quite blurred; it’s unclear whether the site constitutes a dust explosive area, and installing local cabinets on-site is also a hassle