Process Analyzer uses WinPLC
from AutomationDirect to monitor
cyanide destruction
NEXTChem Process Analyzers, LLC produces chemical process analyzers for industries such as metal treatment, metal finishing, chemical, wastewater, and pulp and paper. The process analyzers are used to automate laboratory measurement processes and then use the measurements for process control. Some of NEXTChem's customers include a large aerospace company, who uses the analyzer for measuring caustic cleaner for jet engine parts, and a major steel manufacturer, who measures sulfuric acid in coke oven scrubbers.
Conductivity and pH are the traditional methods for measuring and controlling chemical processes. However, both of these methods are not capable of providing exact chemical concentrations. This severely handicaps the ability to provide useful process control.
Laboratory measurements performed with process analyzers are generally one of two types: titration or standard addition. Titration is a measurement technique that uses a chemical reaction to determine a chemical concentration. Standard addition is a measurement technique that uses the response of an ion selective electrode to determine a chemical concentration. Both of these measurements provide exact information on the chemical process and greatly lower the amount of time it takes to report chemical measurements, from hours to only minutes.
A customer of NEXTChem's is a medical device maker who uses the analyzer to monitor cyanide destruction. Cyanide is used in a metal plating process at the customer's facility and the local municipality has a strict limit on the amount of cyanide that can be discharged into sewers. The analyzer at the facility confirms that all the cyanide is removed from the wastewater before it is discharged into the sewer.
To accomplish the task of cyanide destruction, the NEXTChem Basic OMNIChem process analyzer makes use of AutomationDirect 's DL205 PLC with Entivity WinPLC CPU and H2-SERIO modules, along with digital input and analog output modules, also from AutomationDirect . The WinPLC is programmed with Entivity Studio software. "The Entivity software makes it possible for non-programmers to create very complex programs, and the DL205 system was small enough, but powerful enough to be used in our analyzers," says Tim Pearson of NEXTChem.
The process begins with a D2-TD2-2 digital output module that is used to activate pilot solenoids, which send air pressure to sample valves that allow fresh samples into the analyzer. The H2-SERIO module then sends ASCII commands to a stepper motor controller that activates stepper motors in the analyzer. The stepper motors are connected to pumps that add the proper amount of reagent required for the cyanide analysis.
Next, the cyanide ion selective electrode measures the amount of cyanide present in the sample. This concentration is converted into a voltage signal, which to sent to a voltage-to-current converter. The current signal is brought into the analyzer with an F2-08AD-1 analog input module. The WinPLC then performs all the needed calculations to determine the concentration of cyanide present in the sample. Finally, an F2-08DA-2 analog output module transmits an analog voltage that is relative to the concentration of cyanide present in the sample.
NEXTChem has enjoyed several benefits from their new system, including lower system costs and faster measurement speed. Says Tim Pearson of NEXTChem, "The high quality and low cost of parts from AutomationDirect have enabled NEXTChem to move our process analyzers into the next generation process control. NEXTChem had considered a proprietary controller using C++ programming, however the ease of programming the WinPLC offers has enabled us to bring our product to market six months earlier then we had anticipated, and at a lower cost."
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