ABSTRACT
This work is aimed at designing and fabricating a spin dryer which can be used in drying spent grains after brewing. This will no doubt save considerable human labours and time wastage involved in conventional method of drying the spent grains by spreading on the ground. It also saves as a means of employments for our teaming population. This machine was designed after due consideration of its ease of production, maintenance and servicing. This study was therefore carried out on the construction of a spin dryer. The dryer mainly consists of a solar collector panel, drying chamber, chimney and a charcoal stove. The solar collector is made up of 5 mm thickness single layer glass, 2 mm black painted aluminum absorber plate and 3 mm fiber glass insulation which is enclosed in a casing made from wood. The drying chamber is made from plywood with 2 cm thickness. Galvanized metal sheet of 1 mm thickness was rolled and welded to make the chimney. The total cost of the dryer was estimated to be N291,847.50 (US$ 765.00*). Different tests were carried out in order to evaluate the performance of the dryer. No load test, i.e. test without keeping any material to be dried, was performed and it indicated temperature could rise up to 53.3 oC in the dryer. Average collector temperature recorded was 56.4 oC. In the evening, the dryer temperature was kept above the ambient and collector temperature by burning charcoal using the backup stove. As a result, after three hours of heat supply the drying temperature reached 50.8 oC. The dryer performance was also evaluated using pineapple and mango. For the different tests carried out the performance parameters used for evaluation included moisture content, drying rate and drying efficiency. The moisture content of pineapple and mango was reduced from 87 % and 85 % to 16 % and 13 %, respectively, within two to three days. When using only solar energy as a heat source, the drying rate for pineapple was found to be 23.7 g/h whereas for mango it was 15.5 g/h. These values were found to be 25.2 g/h and 18.4 g/h, for pineapple and mango, respectively, when solar drying was performed with the backup heater (heater used in the evening only). But a higher drying rate was obtained, 32.5 g/h for pineapple and 19.3 g/h for mango, when the backup heater was used with the solar energy during both the day time and in the evening. The collector efficiency was found to be 31.7 %. Drying efficiency was also found to be 9.7 %, 7.5 % and 8.7 % for solar drying, hybrid mode (backup heater used in the evening) and solar drying in hybrid mode ( backup heater used during day time and evening), respectively.
CHAPTER ONE:
INTRODUCTION
1.1. Background
Machine design is the creation of new and better machines and improving the existing ones. A new or better machine is one which is more economical in the overall cost of production, operation and maintenance.
It is on these background that we came out with a design of a machine, which shall help in solving problems of drying spent grains in our breweries.
The major problem facing breweries in the country in how to utilize the spent grains after brewing. Though some breweries use these spent grains as aids by drying and burning them. We hence see this method of recognition as not being economical but wasteful.
There propelled us to designing a new method of drying these spent grains to the required moisture content through the use of a SPIN DRYER. When these spent grains are properly dried, it could be a major constituent in the production of poultry feeds.
With this spin dryer, the unemployed masses could gain jobs by fabricating or buying this machine for drying of spent grains, and recycling it to a useful feed for poultry.
It is worthy to note that the production of a spin dryer is designed in a way that even the unskilled workers could operate it, in fact, we are designing this project as our quota towards the eradication of unemployment and poverty, which this present government is wedging war against.
Moreover, technology could be bought, borrowed or stolen. Our project is a borrowed technology from the western world, which was primarily used for drying of clothes, but we have expanded this scope to deal favourably with drying of spent grains to the desired moisture content.
Agriculture in Nigeria is mainly carried out on a smallholder basis and it is mainly the traditional system of farming. About 90% of farm holdings are smaller than two hectares in size (MOFA, 2011). But there are some large farms and plantations, especially palm oil, rubber and coconut and to a lesser extent, maize, rice and pineapples. In Nigeria, cocoa, oil palm, coconut, cola and rubber are considered as the major industrial crops while cassava, cocoyam, yam, maize, rice, millet, sorghum and plantain are the main starchy and cereal staples in the country. The main agricultural produce under the category of fruits and vegetables are citrus, pineapple, banana, pawpaw, cashew, mango, tomato, okro, egg plant, pepper, asian vegetables and onion (MOFA, 2011).
MOFA (2011) stated that although agriculture is the largest sector of the economy in Nigeria, contributing about 39% of GDP, there are basic problems faced by this sector which include high post harvest losses as a result of poor post harvest management. For instance, Zakari (2012) has given an estimate showing that the average post harvest loss of mango is between 20 % and 50 %. The main reason for losses has been attributed to the fruit fly presence and a host of diseases as well as lack of cold chain facilities, and long transit time. Antwi (2007) also suggested that there would be loss of fresh produce during the harvest period because of excess production which could lead to unsold produce. This surplus produce should be stored so that it can be used later. But it might be unsafe to keep these produce over a long period due to high moisture content, physical damage, pathogens etc.
