Design and Improvement of Dewatering System Implemented for Biogas Slurry
Date
2023-11
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
IOE Pulchowk Campus
Abstract
The report titled "Design and Improvement of Dewatering System Implemented for
Biogas Slurry" aims to validate the screw of existing dewatering machine initially
created by Sherpa et al. in 2017 and modified by Sujan Jojiju in 2023. The goal is to
validate the design, test the modified machine with effective screw press and evaluate
its performance with respect to nutrient contents present in input and output materials
along with comparison of its efficiency with conventional sun-drying process used in
drying the slurry sample.
In Nepal, there is a significant demand for organic fertilizers and dewatering the biogas
residue could serve as an eco-friendly alternative to chemical fertilizers. The design for
validation of screw component and testing of machine are related to research,
recommendations from literatures and advice from supervisors.
SolidWorks is used for the design process and ANSYS for the simulation works while
its testing is conducted at workshop of GRIT Engineering Pvt. Ltd. The biogas slurry
used for testing as well as sun-drying is collected from the biogas plant’s prototype of
1m3
capacity present in the premises of Pulchowk Campus, Lalitpur. The machine's
performance is evaluated at various operating speeds (36, 25, 20, 15, 10 and 8 rpm)
using a Variable Frequency Drive (VFD). The results reveal that the most efficient
operating speed being 8 rpm. The liquid yield, extraction efficiency, and extraction
losses are determined to be 52.51%, 79.11% and 22.80%, respectively.
The slurry sample is sun-dried for 24, 48 and 72 hours whose nutrients concentrations
(TS, N, P, K) are tested in Soil Water and Air Testing Laboratories Pvt. Ltd. The results
show that optimum duration of sun-drying is 48 hours as its reduction of Total Solid
contents is least. The slurry sample before testing in dewatering machine is also pretreated for 24 and 48 hours to check the efficiency of existing machine and compare the
results with that of sun-drying process.
From Financial analysis, the machine's installation cost is NRs. 392,000, along with the
payback period, IRR and NPV are calculated as 1year 10months 23days, 44% and NRs.
353575.86 respectively
Description
A biogas plant is straightforward, inexpensive and uncomplicated way to sustain energy
supply since it allows for natural breakdown of organic ingredients without use of air. The
question of whether the biogas slurry need to be dewatered and dried before using it in
agriculture is raised, which can be utilized as a high nutrient fertilizer as it also does not
impact the environment
Keywords
Variable Frequency Drive