CASE STUDIES- 4
PRODUCTION IN M/S THREE STAR PAPER MILLS
2. ABOUT THE INDUSTRY:
3. PRODUCTION PROCESS:
- APPLICATION OF CP AND THE RESULTS ACHIEVED
- OVERVIEW OF RESULTS ACHIEVED
1. INTRODUCTION3. PRODUCTION PROCESS:
Pulp & Paper industry is governed by the cyclical nature of stocks world wide. With quantitative restrictions lifted and imported pulp available at cheaper prices there is a general recession in the Indian industry and margins are affected. The problems is more acute with small scale industry as they cannot compete on economies of scale. The increasing regulatory pressure to control pollution is further adding to the woes of industry. In these circumstances the unit decided to adapt Cleaner Production (CP) with assistance from National Cleaner Production Centre (NCPC), India.
Cleaner Production is defined as the continuous application of an "Integrated Preventive Environment Strategy to Processes, Products and Services", to increase Eco-efficiency and reduce risks to humans and the environment.
This case describes the benefits and market sustainability attained by adopting Cleaner production techniques by M/s Three Star Paper Mills Ltd. (TSPM).
2. ABOUT THE INDUSTRY:
M/s Three Star Paper Mills Ltd. (TSPM). situated at Dadri, India is engaged in the production of writing & printing paper (10 to 15 T/day of 48 - 70 gsm) for the past 12 years. The unit is using waste paper as the major raw material (with little portion of imported waste paper).
A brief production process of paper manufacturing from the waste paper as adapted in the unit is detailed below.
Waste paper is sorted manually to pick out plastic, wax-coated paper, bitumen etc. and fed into the vertical pulper through conveyor. Water is added for slushing and the whole content is agitated to make pulp from the waste paper. This pulp is then sent to the sand trap for removing the sand. Then the pulp is sent to the potcher for de-inking. The pulp is de-inked using caustic and
bleached using chlorine, to visual purity. The de-inked pulp is washed with fresh water to remove the chlorine and then taken to the decker drum for increasing the consistency of the pulp and subsequently stored in the Chest. The pulp from this chest is pumped through a single disc refiner and stored in the machine chest. Now this pulp goes to a three stage centri-cleaner to remove the knots and other impurities. Alum, rosin and other additives are added at this stage and then it goes to the paper machine.
The paper machine has 3 principal stages:
i) The gravitational and vacuum de-watering stage i.e. Wire pit - here pulp is fed at a consistency of around 0.7% and when the paper goes out of this stage the consistency becomes around 20%.
ii) The mechanical de-watering stage. i.e. Press Section - Here the paper with 20%consistency (80% moisture) is squeezed through a set of press rolls (having 2 rolls in each set) to get 35% consistency paper (65% moisture).
iii) Thermal drying stage (indirect steam dryer
The final moisture content of the paper rolled on to the pop-reel is around 5- 6%. The paper from the pop-reel goes to the rewinder for making reels in required sizes and then it goes to despatch Section.
APPLICATION OF CP AND THE RESULTS ACHIEVED
1. Installation of a waste paper de-duster has resulted into the removal of all the contaminants in the waste paper like, Bidis, Cigarettes, Plastic, Pins, Threads, Mud, Sand etc. which has lead to the improvement of the paper quality, reduction in chemical consumption etc.
Yeast does produce some organic acids during fermentation but their concentrations are relatively low as compared to the concentrations of acids produced by lactobacillus and other contaminating bacteria. When Lactobacillus is achieved, the generation of lactic acid substantially increases the titrable acidity and often these high acid levels will cause the yeast fermentation to reduce or slow down considerably. In-house fabrication of the mechanical de-duster costed about Rs. 10 lakhs and the savings accrued by the implementation of this option is about Rs. 10 lakhs/annum.
2. By installing a hot dispenser, the quality of the paper was increased and it also reduced chemical consumption for de-inking.
The in-house fabrication of the hot dispenser costed around Rs. 2 lakhs and the savings accrued by this option is Rs. 10 lakhs/annum.
3. The pulper has been changed from vertical to horizontal, high-low type pulper. By implementing this option, plastics are removed as such without getting cut and disturbing the fiber structure. This option has also resulted into the electrical energy reduction by about 20 HP.
This option was implemented with an initial investment of about Rs. 3 lakhs and the savings accrued by this option is about Rs. 5 lakhs/annum.
4. Installation of a Helly screen in place of Couch pit Decker has resulted in the saving of electrical energy.
This option was implemented with an initial investment of about Rs. 0.3 lakhs and the savings accrued by this option is about Rs. 1 lakh/annum.
5. Installation of a pneumatic valve (operating at 3-5 psig) at the main header has resulted into the saving of operating man power, steam saving of about 20% and the paper quality was improved due to the regular & controlled supply of steam to the paper machine.
This option was implemented with an initial investment of about Rs.0.3 lakhs and the savings accrued by this option is about Rs. 2 lakhs/annum.
6. Installation of an economiser has resulted in the increase of the Boiler feed water temperature from 35o C to 75o C and thus the fuel consumption for steam generation was reduced by about 25%.
This option was implemented with an initial investment of about Rs.2 lakhs and the savings accrued by this option is about Rs. 10 lakhs/annum.
7. The diameter of the press roll (top roll) in the mechanical de-watering section of the paper machine was increased to increase the linear load and thereby an additional removal of 4% moisture has been achieved. The implementation of this option has lead to the reduction in the steam required for the drying operation and thus a 20% reduction in the fuel consumption in the boiler.
8. The speed of the paper machine has been increased from the existing level by 20% after providing necessary support in between the beams to arrest the machine vibration. The implementation of this option has increased the production capacity by means of improved capacity utilisation of the plant.
Both the options 7 & 8 put together were implemented with an initial investment of about Rs. 2 lakhs and the savings accrued by these two options are about Rs. 6 lakhs/annum.
9. The existing condensate collection tank was provided with a vent. The flash steam coming out of the system was vented out and was not utilised.
This condensate recovery system was improved by connecting another tank on line. The existing tank was used as a flash steam separator and the vent provided in the existing tank was connected directly to the dryers 1, 2, & 3 so as to utilise the flash steam directly. The condensate from the bottom of the tank is collected in the other tank connected to the system and from there the condensate is pumped to the boiler.
The implementation of this option has lead to 15% increase in the Boiler feed water temperature and also the consumption of steam was reduced by 10 to 15% because of the utilisation of the flash steam which was vented out earlier.
This option was implemented with an initial investment of about Rs. 1.5lakhs and the savings accrued by this option is about Rs. 5 lakhs/annum.
10. By installing a low vacuum box in the wire pit section, the moisture in the paper was reduced by about 2%. This particular option has resulted in the reduction of the press picking by about 1/6th.
This option was implemented with an initial investment of about Rs. 0.5 lakhs and the savings accrued by this option is about Rs. 2 lakhs/annum
11. Periodic maintenance of the pump glands and installation of the 'Save-All' has resulted into the reduction of the fiber loss and saving of the chemicals which otherwise was drained through leakage in the pump glands.
This option was implemented with an initial investment of about Rs. 10 lakhs and the savings accrued by this option is about Rs. 4 lakhs/annum.
12. Above all, the major option implemented by the unit is the recycle of backwater. By implementation of this option, the fresh water consumption has reduced by about 60%.
This option has lead to the reduction in the electrical energy utilised for the treatment of the wastewater (if it is to be discharged) by about 60%. However, the backwater is clarified, screened and then pumped back to the process which consumes only about 40% of the electrical energy which was required before implementation of this option.
13. Another major option is the manufacture of paperboard (by-product) from the solid waste generated from the clarification of the wastewater before recycling in the process. The implementation of this option has resulted into the total elimination of the solid waste generated from the manufacture of paper from the waste paper.
This option was implemented with an initial investment of about Rs. 20 lakhs and the savings accrued by this option is about Rs. 40 lakhs/annum.
The Unit has taken enormous efforts for the generation and implementation of CP measures. By adapting the concept of CP, the unit could improve the quality of paper manufactured and reduce its overall cost of production. The over view of total results are given in the table below:
OVERVIEW OF RESULTS ACHIEVED