Materials balance in a tung oil mill

Abstract

SummaryWeights were determined and analyses made of tung fruit milled and of all products leaving the mill for two runs of about 90 tons each in a commercial mill under normal operating conditions. Dry matter, oil, and nitrogen in the fruit were satisfactorily accounted for in products leaving the mill, 101% of the oil being accounted for in each run. This showed that the methods of analysis and sampling were accurate.Losses occurred principally in particles of kernels occluded with the hulls and in the screw‐press cake. Seventy‐eight and 82% of the oil in the fruit was recovered as filtered oil.Repressing the filter‐press cake by adding it back to the stream of ground nuts just before they entered the screw‐presses was not proven to be economical as at the end of the run just as much cake was on hand, and it had as high an oil content as if no filter cake had been fed back through the screw presses. Only about half as much oil could be filtered per filtration cycle, resulting in an increase in cost of labor and a decrease in filtering capacity.The apparent oil content of the screw‐press cake decreases by about 2% after four to eight days as compared to its apparent oil content at the time of pressing because of polymerization. Thus, screw‐press cake samples should be analyzed for oil as soon as possible after extrusion.