The process of separating the seed from the cotton fibre is called ginning. The ideal ginning is the separation without any damage of the fibre. Ginning is the first mechanical process involved in processing cotton. Ginning mill separates cotton fibers from the seed bolls and dust particles. The main application of ginned cotton referred to as lint is for spinning operations, where lint is converted to yarn.
- To make the fibre totally free from seed.
- To increase the quality of the fibre.
- To get fair price of the product.
- To make the spinning process easy & effective.
- To collect the fibres & the seeds at a time in a separate passage.
Methods of ginning:There are two methods of ginning
1. Manual method; 2. Mechanical method;
# Hand ginning # Saw ginning
# Foot roller ginning # Knife roller ginning
# Charka ginning # Macarthy roller ginning
Difference between Saw ginning & Roller ginning:
|Saw ginning||Roller ginning|
|1. Used for the fibres which are not easily separated from the seeds.||1. Used for the fibres which can easily be separated from the seeds.|
|2. Used for short to medium staple fibre.||2. Used for long staple fibre.|
|3. Higher production rate up to 500 lbs/hour.||3. Lower production rate up to 100-200 lbs/hour.|
|4. It gives less clean lint.||4. It gives more clean lint.|
|5. Saw ginning tends to damage the fibre if precautions are not taken.||5. Possibility of damaging the fibre is less.|
|6. It contains more impurities.||6. It contains less impurities.|
Manufacturing Process& Technology
Ginning process is shown in the flow chart given below. Seed cotton is fed tograding system where grading is done followed by pneumatic conveying. Fromhere it is fed to preliminary cleaning process, followed by saw gin, lint cleaner,pre-bale press and cotton bales.
Ginning Process involves two cleaning stages:
1. Pre Cleaning
2. Post Cleaning
The main operation of separating seed from cotton is done by saw gin. In the ginhouse after ginning process is completed the cotton lint and cotton seeds areseparated and the lint passes out through pneumatic system to the Post-cleaner(Lint Cleaners) in which small impurities, dust particles, small fibers are carriedout and cotton becomes free from contamination.
Cleaned Lint is taken to the bale press which compresses the ginned lint intobales that weigh around 170 Kgs. After pressing is completed the bale istightened and covered fully with cloth, after then the bale is weighed and kept inthe hall safely.
Packaging the Lint:
The bales are then wrapped with a protective cover, ready for delivery to thewarehouse where they are sold to various textile mills
The technology required for the ginning & pressing operations are cottonginning machinery, pre cleaner, lint cleaner, Kappas conveyor system, lintconveyor system,Hydraulic cotton baling press, conveyor for seed, electricalinfrastructure, Humidifier and weighbridge etc. The other optional machineryrequired is the foreign fibre detectors/removers.
Minimum economic size of the plant:
The minimum economic capacity of the ginning mill is about 24 Gins.
Yield and Production:
The yield of lint cotton is assumed at 32%, seed is assumed at 65% and waste isassumed at 3% which are based on the industrial norms and manufacturersspecifications.
The investment cost for setting up a ginning mill of 24 gins will be around Rs.9.64 Crores or BDT. 14.07 Crores Cand the break up of the cost is tabulated below.The land requirement will be around 7 acres. The pre-operative expense includesinterest during construction of Rs 0.24 crores. Plant & Machinery includinginstallation, erecting & commissioning charges are of 2.63 crore. Buildings andcivil works are estimated to be 2.73 crore. Contingencies, electricity deposits arealso considered in the project cost. Margin money for working capital isestimated to be 3.54 crore.
Estimated Project Cost
1 Land & Site Development 0.17
2 Buildings & Civil works 2.73
3 Plant & Machinery including erc., ins.,& freight 2.63
4 Electricity Deposits 0.12
5 Preliminary Expenses 0.07
6 Pre-operative Expenses 0.24
7 Contingency @5% 0.14
8 Margin Money for Working capital 3.54
Total Project Cost Rs. 9.64or BDT 14.07 Crores