The Hindu : Business : Waste minimisation programme found profitable in fertilizer unit

Online edition of India's National Newspaper
Friday, Aug 11, 2006

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Business

Waste minimisation programme found profitable in fertilizer unit

Staff Reporter

Scheme implemented with the help of IORG

PALAKKAD: The waste minimisation programme implemented in small-scale fertilizer manufacturing unit of 10 tonnes per day capacity Epsom salt could save Rs.8.65 lakhs.

The scheme implemented with the help of Industrial Operations Research Group (IORG), Palakkad, saved Rs.8.5 lakhs per annum by making a small investment of up to Rs.1 lakh for purchasing and using suitable weighing machines and adopting improved practices. The payback period is less than two months.

The manufacture of Epsom salt requires manganese ore, sulphuric acid, magnesium oxide and water as ingredients. The present practice is to add these ingredients on continuous basis, mix them till reaction is completed and the clear liquid of magnesium sulphate separates out which is sent for crystallisation and drying.

A study conducted by N.G. Nair of IORG said that a typical SSI unit has a capacity to produce 10 tonnes per day of Epsom salt. A large number of reaction tanks and mixing tanks are constructed and workers use large wooden batons to mix the ingredients poured in these tanks. The transfer of liquid is facilitated by overflow or siphoning action using PVC pipes.

The quality of ingredients used is based on `thump rule' dictated by the supervisor. There is no weighing system, as these ingredients are not issued on weight but by volume basis. The purity of the ingredients does not receive serious considerations.

It has been observed that magnesium ore received by the units come in different impurity levels, which vary from 50 to 75 per cent. As this aspect gets ignored, the input quantity of the ore taken for reaction varies. In effect, these chemicals are not issued in their molar proportions. This results in excess consumption of material, which along with the impurities appear as sludge and is indicative of the waste generated in the unit, he said.

For the production of 10 tonnes of Epsom salt per day, the requirement of various ingredients estimated are six tonnes of 25 per cent purity ore and 120 kg of magnesium oxide. Further four tonnes of sulphuric acid would be required and 4.5 KL of water for the reaction purpose. Another 5.5 KL of water will also be required to account for evaporation and potential seepage losses and for keeping the reactant mass in solution. The impurities\sludge generated would amount to approximately 1.5 tonnes per day.

Thus it has been found that the current usage of ingredients and potential amount of resource conservation feasible and economic savings potential for a typical fertilizer unit manufacturing 10 tonnes of Espson salt is Rs.8.5 lakhs per annum, Dr. Nair said.

The manufacture of Epsom salt finds another bottleneck, which is in the drying process. According to present practices, after crystallisation and recovery of product through centrifuge, the product is dried in open air and is subject to vagaries of climate, which is restrictive on the production capacity\yield of these units.

To overcome this problem the usage of electrically driven rotating drum is found economical. The heat recovered from the flue gases from the boiler furnace has been utilised for drying the magnesium sulphate crystal.

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