OPTIMIZATION OF CASSAVA MASH DEWATERING PROCESS PARAMETERS

Abstract

Cassava dewatering is an important aspect in cassava processing due to its significance to influence drying time and energy use. In this study, cassava dewatering process parameters were optimized using D- optimal response surface methodology and Analysis of variance (p<0.05) was used to determine the effect of the factors on the responses. Selection of process variables was carried out with the Design-Expert® (version 11) software experiment, design of experiment resulted in 32 runs. Numerical input factors are mass (15 – 35 kg) and force (5 – 25 kN) while categorical input factors are dewatering bags (jute bag, polyethylene bag and cloth bag) and dewatering machine (motorized hydraulic press, manual hydraulic press and screw press) were selected. The output factors (responses) were selected as dewatering time, moisture flow rate, dewatering pressure, starch content percentage, moisture content percentage, dewatering efficiency, machine capacity and dewatering time. The cassava tubers were peeled, grated into cassava mash. The cassava mash was measured and dewatered based on the design of experiment. During each experiment, initial mass of mash, final mass, dewatering time and volume of effluent were recorded for determination of responses also laboratory analysis of samples was done for starch content (%) and dry matter (%) after each experiment was carried out. The results show that the output factors ranges from, 23.43 - 60%, 7 – 44 mins, 21.9 x 10-6 - 40.0 x 10-6 m3s-1, 20.02 - 101.01 Nm-2, 44.05 - 52.23%, 44.49 - 58.9%, 13.71 - 288.0 kg/h and 205.7 - 1008.0kg/h for dewatering efficiency, dewatering time, moisture flow rate, dewatering pressure, (%) starch content), (%) dry matter machine capacity and dewatering rate respectively. The effect of the factors on the responses using analysis of variance show that the mass of cassava mash significantly (p<0.05) affects the machine capacity, dewatering efficiency, dewatering rate and moisture flow rate. Dewatering force had significant effect on machine capacity, moisture flow rate and dewatering rate. The moisture flow rate, dewatering time and dewatering rate were significantly affected by the machine factor. The variation in the dewatering bag did not have any significant effect on any of the responses at (p<0.05). The dewatering efficiency, moisture flow rate, machine capacity, dewatering time and dewatering rate show that the combination of the input factors can significantly explain the variation in the responses, while the combination of the input factors had no significant influence on the (%) starch content and (%) dry matter as P value is greater than 0.05. For optimal performance determination, the objective functions for the eight response variables are to maximize the dewatering efficiency, percentage of starch content, moisture flow rate, dewatering rate, machine capacity, percentage of dry matter and minimize the dewatering time while dewatering pressure, dewatering force, machine, mass and bag were set in range. Jute sack using motorized hydraulic press with 5 kN dewatering force and 35 kg of cassava mash had the highest desirability of 57.5% with the following optimum values: dewatering efficiency of 45.38% with starch content of 48.759%, moisture flow rate of 24.930 x 106 m3s-1, dewatering rate of 5290 kgh- 1, dry matter% of 54.458 %, machine capacity of 162.71kgh-1, dewatering time of 17.977 min, dewatering pressure of 20. 2022 Nmm-2. Based on the parameters studied and the obtained optimal operational conditions, this research will enhance dewatering operation and help to reduce drying time and energy use.