Design and Fabrication of a Total Organic Carbon Analyzer

摘要

An automated total organic carbon (TOC) analyzer has been constructed to analyze highly contaminated wastewaters from coal gasification and liquefaction processes. These wastewaters have TOC contents of 10--20,000 mg/L, sulfide contents of 20--30,000 mg/L and ammonia contents of 1000--20,000 mg/L. Most commercial TOC analyzers require dilution of such wastewaters and/or traps and scrubbers to remove the oxides of sulfur and nitrogen that interfere with the measurement of carbon dioxide. This TOC analyzer was designed to handle these wastewaters with a minimum of sample preparation, with no traps or scrubbers and with a minimum of operator attention. The TOC analyzer uses a high temperature cobalt oxide on asbestos packed reactor for total carbon (TC) determinations and a low temperature phosphoric acid wetted quartz chip packed reactor for carbonate carbon (CC) determinations, with TOC being the difference (TOC = TC--CC). The furnace temperatures are regulated by time-proportioning temperature controllers. A mass/flow controller is used to regulate the oxygen carrier/combustion gas flow rate. The carbon dioxide produced is measured by a nondispersive single-beam infrared photometer. A commercially available laboratory automation system operates and monitors the TOC analyzer. The automation system operates the analyzer via two event control modules (ECM's). Generally 20 mu L injection volumes are used and samples having carbon concentrations of 10--10,000 mg/L can be analyzed every three minutes. The signal from the infrared photometer is digitized by an analog-to-digital converter and stored by the automation system. The automation system monitors the oxygen flow rate and the TOC analyzer's power status. If a problem develops, the automation system shuts down the analyzer and notifies the operator. 30 refs., 9 figs., 11 tabs. (ERA citation 13:048034)