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Optimisation of Heat Losses in Paper Dryers

Description

Normally, in a paper dryer, the steam cylinders are about 4- 5 feet in diameter. A typical paper machine has 40 to over 100 steam cylinders, requiring 1,275 to 1,575 BTUs steam input per pound of water dried from the sheet. This case study reflects how insulation of the side plates of these cylinders, non-covered surfaces and non-insulated piping would prevent the heat emission to the surrounding area, resulting in significant saving of energy.

Implementing Industry

Daman Ganga Paper Mills is a medium sized company engaged in recycled packaging products. Company produce a range of recycled products such as Paper, Core-Board, Cores & Tubes, Fibre-Drums, Partition Boards, Insulation Boards, Acoustic Boards, etc. The company started its operation in the year 1982, with present production capacity of Kraft Board 60 Tons per day, with annual turnover of 50 Crores.

Implemented technology / technique

BEFORE:

  • Transfer of paper pulp from the pressure zone to the drying zone, resulted in removal of moisture, thereby, increasing the pulp consistency from 45%-50% upto 94%. For the purpose, a total of 21 drying cylinders are installed for removal of moisture. 

  • It was identified that the side plates of the cylindrical dryers were not insulated. With an open installation of a cylinder dryer, continuous thermal energy was lost due to radiation and convection. The side plates of cylinders and non-insulated pipings emit heat to the surrounding area. Additionally, removal of great quantities of ambient air from the area resulted into even higher loss of energy by convection.

AFTER:

All the cylinder dryers were insulated at side plates with Rock Wool supported by aluminium cladding (specifically designed for motion at fixed RPM), the insulation provided is having following properties:

  • The density varies according to the operation needs, 60kg/m³ to 160kg/m³.

  • The moisture absorbency is very less.

  • Very light and easy to apply.

  • Can be tailored to any requirement, set by the customer.

  • Has a thermal conductivity ranging from 0.07 W/mK to 0.21 W/mK. This depends on the product and the boundary conditions of the system.

  • Is very resistant to most alkalis. And the leachable chloride content is less than 5ppm, thus not propagating corrosion.

The modification was done in-house by the industry in December, 2013 with the help of local contractor. 

Economic benefits

Capital cost incurred by industry for insulation was Rs. 5,00,000 with no operational cost giving a total savings of Rs. 28,71,000 per annum giving return of investment in just 2 months.

Environmental benefits

By insulating the side plates of cylinder, the dryer reduced average steam consumption up to 75 kg per ton of paper and average fuel consumption up to 29 kg per ton of paper production

Contact details 

Mr. Banjul Shah, Director; banjul.shah@damanganga.com