Factors affecting the level of effectiveness of dryers used in Sri Lankan tea manufacturing

Abstract

Tea production is basically a drying process of freshly harvested green tea leaves, reducing its moisture content from about 75-83% down to 3%. In black tea manufacturing tea undergoes mainly withering, rolling, fermenting, drying, grading and packaging processing steps. Sri Lanka mainly produces tea by the Orthodox technology. Drying is the most expensive process in the manufacture of tea (http://www.biriz.biz/cay/TeaSector2002). The capital investment on dryers is also the highest among the different processing machines. There are three different types of tea dryers up to now namely ECP (Endless Chain Pressure), FBD (Fluidized Bed Dryer) and combination dryers. ECP dryer has been used in tea industry since 1907 and fluidized bed dryer was first developed for tea in Sri Lanka in 1974 (Temple S.J., 2000). Tea dryers have its defined output as rated output. But normally dryer machines give lower output (actual output) than rated output. There may be several reasons affecting for dryer output deviation from rated output. Ultimately this would lead to poor production and high cost of production to the tea factories.

Main objective is to find out the factors affecting for deviation of actual dryer output from rated dryer output in different types of tea dryers.

Materials and Methodology

Effectiveness of three types of tea dryers was taken as dependent variable. Effectiveness of tea dryers can be measured as the ratio between actual output and rated output. It will be finally taken as a percentage value.

As independent variables four factors have been selected as moisture content of withered leaves (wither percentage %), age of three types of dryers (Years), moisture of firewood used for drying (firewood moisture) and dhool percentage taken after roll breaking process (first, second and third dhool percentage).

The sampling frame was 37 tea dryers representing three manufacturing regions in Sri Lanka (Up country, Mid country and Low country). There were 17 ECP dryers, 15 FBD dryers and 5 combination dryers in the sample. The data were collected for recent three months time period and average values were taken finally. For the analysis descriptive, correlation and simple linear regression was used.

Results and Discussion

According to descriptive statistics mean effectiveness of ECP, FBD and combination dryers were 85.88%, 89.83%, 91.53% respectively.