Batch process control automated systems

Development of automated batch process control systems has lagged behind that of continuous process control. Flexible factory scale commercial systems have only begun to appear in the last five years (1-4). Increases in the performance/price ratio of small computers are now making automation of laboratory scale batch processes more practical. 

The primary goal of the work described here is to provide a means whereby specifiers can become implementers that is, to provide automation systems tools (for the specific case of batch polymerizations) allowing process and production experts to design, implement, maintain, and enhance their own "state-of- the-art" control systems. 

Apparatus. Since all the polymer modification reactions presented in this paper involved gas consumption, an automated gas consumption measuring system was designed, fabricated and used to keep constant pressure and record continuously the consumption of gas in a batch type laboratory scale reactor. Process control, data acquisition, and analysis was carried out using a personal computer (IBM) and an interface device (Lab-master, Tecmar Inc.). 

General References Fisher, Batch Control Systems Design, Application, and Implementation, ISA, Research Triangle Park, N.C., 1990. Rosenof and Ghosh, Batch Process Automation, Van Nostrand Reinhold, New York, 1987. 

It is now common practice in our laboratory to assay parathyroid hormone by a fully automated system in batches of 60 samples with appropriate controls at intervals of 20 samples. Patient samples are input at the appropriate dilution, this process taking approximately 1 hr. On the reagent addition unit, labeled antibody is added, as well as plasma to standards and buffer to plasma samples. Reagent addition takes 10-15 min. After incubation at 4 for 72 hr, the assay tubes are allowed to adjust to room temperature (the Kemtek 3000 does not have means of refrigeration), and immunoadsorbent is added, with a 10 sec delay between each addition. When addition is complete (30-40 min), filtration is commenced with a cycle that takes 50 sec for its five simultaneous transfers plus washing. The filters are dried and counted. It should be noted that this procedure differs from the standard immunoradiometric technique in that it is the radioactivity not bound to antigen that is counted. The data therefore resemble those derived from a classical radioimmunoassay and can be processed by the Kemtek computer using a polynomial cubic analysis. ... 

Automatic instruments with discrete (batch) sample handling and analysis have special problems when used for automated process-control. These instruments consist of a sampling system, an analyzer, and a memory device that maintains the... 

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