Environmental Case Studies

Case Study 118: Scrubbers Industry Sector: Environmental • Stack emission control system

Technology Replaced:

  • Square D 784 PLC System

New Technology Applied:

  • Modicon Quantum Redundant System

Project Description:
Staneco Corporation replaced outdated PLCs with new Redundant Modicon Quantum PLCs for air pollution and dust collection equipment at a power plant. The system was programmed utilizing existing loop drawings along with additional input from client’s engineering staff. The hardware was replaced in a manner which allowed for minimum down time. The existing field wiring was unchanged. Because the new PLC equipment was so much smaller than the original, Staneco came up with a design that added terminal blocks in the same physical locations as the original I/O. These terminals were located on sub-panels along with the new PLC hardware. The terminals were wired to the new PLC I/O. The entire assembly was installed on the existing panel. When the old I/O was removed, the original field wiring was landed back on the new terminals without disturbing the field wiring. This allowed the change to be made in the short outage window.

Project Outcome:
Since the old PLC hardware was obsolete and replacement hardware becoming harder to obtain upgrading the system was essential to the plant’s operation. The new system provided additional fault monitoring and greater data collection making the process easier to troubleshoot and monitor.

Case Study 130: Gas Recovery System Industry Sector: Environmental • Gas Recovery System

New Technology Applied:

  • Allen Bradley SLC 500
  • Allen Bradley Micrologix 1500
  • Allen Bradley PanelView Plus
  • Rockwell RSView32 SCADA

Project Description:
Staneco Corporation designed a control system that purified contaminated ground water. The system consisted of three wells. Water was pumped from two of the wells.  Flow from the wells was monitored.  The flow rate could be regulated either by fixed flow rate or by monitoring the level of the wells and adjusting the flow to keep the level of the wells at a fixed setpoint. The operator selected the desired method of control. A chemical was added to the water and it was pumped back into a third well. The flow rate of the chemical was paced to the flow rate of the water.  Data was collected which included well levels, water flow, and chemical flow. The data was stored in Excel format.

Case Study 102: Stack Emission Control Industry Sector: Environmental • Regenerative Thermal Oxidizers

New Technology Applied:

  • Allen Bradley CompactLogix
  • Allen Bradley PanelView Plus HMI

Project Description:
Staneco designed controls for two thermal oxidizers used at a corn-to-ethanol plant to remove organic chemicals from discharged air. The oxidizers consisted of multiple gas burners which heated combustion chambers containing ceramic pellets. When the process gas is passed through the pellets, the organic chemicals are oxidized, neutralizing them. In order to prevent overheating of the ceramic pellets, a series of dampers were switched based on either time or chamber temperature. As the chambers were switched, some gas escaped unprocessed. To remove these gases, a purge operation was included to re-circulate the untreated gasses. The motors were controlled over Devicenet which included two VFDs. Temperatures and operation of the valves are monitored and alarmed. Data was made available to the plant DCS system.

Project Outcome:
System met and exceeded the required emission acceptable limits. The process also helped minimize fuel consumption.

Case Study 103: Scarfing Industry Sector: Environmental • Scarfing / Crusher Conveyor System

Old Technology Replaced:

  • Antiquated Relay Panel

New Technology Applied:

  • Allen Bradley MicroLogix
  • Allen Bradley Component HMI

Project Description:
Staneco Corporation designed a crusher conveyor control system to replace an existing relay panel. The system consisted of conveying material through a series of conveyors and hydraulic crushers. Crushed material was then conveyed and separated by size and conveyed to different piles. Speed of the conveyor was controlled by VFD based on operator input. Safety interlocks were applied to prevent any possibility of injury. The system was able to operate in automatic, remote and manual modes. HMI displayed alarm conditions and location of fault events.

Project Outcome:
The combination of the PLC and HMI provided a more modernized system which increased throughput and minimized downtime while meeting all safety requirements.

Case Study 104: Air Pollution Controls Industry Sector: Environmental • Regenerative Thermal Oxidizers

New Technology Applied:

  • Siemens Simatic S7-300
  • Siemens Simatic HMI MP 277

Project Description:
Staneco designed controls for two thermal oxidizers used for treatment and abatement of malodorous emissions at a waste treatment facility. The oxidizers consisted of multiple gas burners which heated combustion chambers containing ceramic pellets. When the process gas was passed through the pellets, the organic chemicals are oxidized, neutralizing them. In order to prevent overheating of the ceramic pellets, a series of dampers were switched based on either time or chamber temperature. As the chambers were switched, some gas escaped unprocessed. To remove these gases, a purge operation was included which re-circulated the untreated gasses. Temperatures and operation of the valves was monitored and alarmed.

Project Outcome:
Malodorous emissions were eliminated meeting local requirements.