Investment Cost: 22,000 Yuan
| Cleaner Production in Pulp and Paper Mill | China | 1990 | CP Audit |
MANUFACTURE OF PAPER AND PAPER PRODUCTS # 21
Background
Beijing No.7 Paper Mill, a state-operated enterprise, was founded in 1960 as an integrated mill involved in the production of pulp and paper. It is located in the chemical zone in Tongxian county. The mill owns a total area of 17.9 hectares and employs 1,694 workers and staff members, in which 88 staff members are responsible for management and 66 staff members produce the technical support in the different departments.
Total output of paper and paperboard is 33,000 tons per year. The profits reach 1,274,000 Yuan a year with annual gross industrial product of 98.298 million Yuan (in 1990 fixed prices).
The pulp and paper mill consumes a lot of energy and water. The pollutant discharges and/or emissions from the mill also are very large, especially waste water containing fine fabric and filler particles. Some useful materials in the waste water were also discharged as waste.
Environmental pollution still is a serious problem though some environmental pollution control measures have been performed in the mill. A major problem is the lack of available technologies for treating the black liquor from the wheat straw pulp line.
Lack of good management practices, production adjustments and strict environmental requirements greatly affect economic benefits.
Process and Waste Treatment Information
The mill operates a wheat straw pulping line, waste paper breaking and pulping line, paperboard breaking and pulping line, and market paper production line.
The original manufacturing process is stock proportioning, stock refining, mixing, primary and secondary cleaning, pressure screening, water removing, pressing, drying, size pressing, drying and calendar, and winder.
The main pollutant is waste water. Waste water from each production line is discharged into air floating equipment to be treated. The method for total amount controls of pollutant discharge and/or emission is used to manage environmental pollution. Pollution permits are adopted to control the total amount of pollutant discharges and/or emissions. Overall, the production capacity is reduced causing serious pollution.
Cleaner Production Principle
Process modification; Housekeeping
Cleaner Production Application
A total of 27 options were generated. All the options were divided into 3 classes, in which 8 options were of no or low investment and labelled Class A, 12 short-term options were labelled Class B, the last 7, long-term options were labelled Class C.
The eight options in Class A, are easily implemented through strengthening management or housekeeping and entailing no or low investments.
1. Using white water for breaking and pulping waste paper and board to reduce water consumption.
2. Using white water to dilute rejects in tank in the first step of cleaning to reduce water consumption.
3. Sensible use of condensed water from dryers to save energy.
4. Sensible use of paper lints from press section to reduce loss and prevent pollution.
5. Increasing the washing of straw pulp to reduce consumption of Aluminium Sulfate.
6. Increasing scraping times in air floating tank to reduce reprecipitation of the fibers.
7. Keeping open the air inlet door in air floatation and observing the rules of operation.
8. Forbidding the use of fresh water to clean chests and provide good tools for sanitation workers.
The twelve short-term options in Class B, are easily implemented with low investments, short payback periods and good benefits.
9. Using dispersive rosin instead of soap rosin.
10. Adding denatured starch and other additives, to increase retention of fines and fillers, and to reduce solids content in white water.
11. Adding white water pipe in the beginning of the end of the tank’s first step cleaning system and reducing fiber deposit.
12. Changing the valve in the air inlet pipe, to increase water flow, and to change some structures.
13. Only using white water to dilute brokes in coach tank, and to save fresh water.
14. Backfeeding water from vacuum pump and vacuum coach pump back to white water tank directly.
15. Increasing height of mixing tank, to reduce overflow of pulp slurry.
16. Adopting the grooved press roll instead of the normal plain press roll in order to reduce energy consumption in the following procedure.
17. Improving efficiency of decker and reduce fiber losses.
18. Training operators and improving their skills.
19. Adding flocculate and improving efficiency of air floatation.
20. Using plastic wire instead of bronze wire.
The seven long-term options in Class C, are not easily implemented because of the need for large investments and the length of time necessary for their implementation.
21. Using high pressure water to wash wire and to reduce water consumption.
22. Adding a vacuum pump in the third step of steam inlet and to keep a pressure differential and reduce steam consumption.
23. Making an efficient schedule of production and reducing the repeated starts and stops.
24. Using surplus white water to board machine.
25. Using warm air hood and heat pump to reduce steam consumption.
26. Installing modern metering gauges and insuring maintenance and reducing leakage.
Development Stage
The no-or low-investment options in Class A have been implemented. All Options in Class B were studied and analysed with the weight method, and then those with higher weight scores were selected for implementation. Options in Class C were put aside.
Based on the weight analysis, options 9, 12, and 16 have higher weight scores. Technical evaluation, economic analysis, and environmental assessment for three options in Class B were carried out. Options 9, 12, and 16 are environmentally attainable, economically and technically feasible. Options 9, 12, and 16 will be implemented in January, 1997, June, 1996 and December, 1996, respectively. Other options in Class B will be put aside.
Environmental and Economic Benefits
The discharge amount of waste water was reduced from 671,982 tons a year to 470,387 tons per year. The reduction amount and the reduction rate are 201,595 tons and 30%, respectively. COD amount discharged in waste water went from 583.2 tons a year to 373.25 tons per year and the reduction rate of COD is 36%, suspended solids (SS) from 988.68 tons to 533.89 tons per year and the reduction rate of SS 46%.
| Number | Item | Before Implementation (t) | After Implementation (t) |
| 1 | Raw Materials | ||
| Pulp | 4,062.24 | 3,995.28 | |
| Talc powder | 1,116.00 | 1,071.36 | |
| Aluminium Sulfate | 624.96 | 602.64 | |
| 2 | Energy Consumption | ||
| Electricity | 4,767.55 kWh | 4,017.60 kWh | |
| Coal | 6,392.45 | 5,356.80 | |
| 3 | Water Consumption | 977,616 | 709,776 |
| 4 | Product Output | 4134 | 4464 |
| 5 | Waste Waste water | 671,982 | 470,387 |
| 6 | Pollution | ||
| COD | 583.2 | 373.25 | |
| SS | 988 68 | 533.89 |
The reduction rate of waste water and COD and SS are 30%, 36%, and 46%, respectively.
Investment Costs
| Changing the valve in the air inlet pipe, to increase water flow, and to change some structures. |
| Adopting the grooved press roll instead of the normal plain press roll to reduce energy consumption in the following procedure. |
| Using dispersive rosin instead of soap rosin. |
Payback Time
| Using dispersive rosin instead of soap rosin. |
| Changing valve in air inlet pipe, to increase water flow, and to change some structures. |
| Adopting the grooved press roll instead of the normal plain press roll to reduce energy consumption in the following procedure. |
Internal Rate of Return(lRR) 19.6%
Constraints
None reported.
Contacts
Review Status
This case study was submitted to UNEP IE by the Sino-Norwegian Cleaner Production Program. It was edited and formatted for the ICPIC diskette in May 1997.
Subsequently the case study has undergone a technical review by Dr Prasad Modak at Environmental Management Centre, Mumbai, India, in September 1998.