Case Study: Boiler Operating Practices to Reduce Energy Consumption at VINAPAPER Company Limited
VINAPAPER COMPANY LIMITED was established in 2007 by DIANA UNICHARM JOINT STOCK COMPANY. However, since September 2017, all shares of Diana Unicharm were transferred to BJC INTERNATIONAL COMPANY LIMITED based on Hong Kong. VINAPAPER has the production capacity of 20,000 tons of paper rolls and 20,000 tons of DIP pulp per year, using advanced technology from Austria and Italy. The main products of VINAPAPER are branded E’mos tissues.
The company has remained at the forefront in the adoption of new production technologies, bringing the highest quality products at reasonable prices to Vietnam consumers. The company’s production technology for women’s sanitary pads and baby diapers is the most modern in Vietnam.
In addition, the company pays special attention to solutions that reduce production costs and protect the environment, such as energy efficiency solutions. To this end, the plant has cooperated with national experts from the Project “Promotion of Energy Efficient Industrial Boiler Adoption and Operating Practices in Vietnam” of the Ministry of Industry and Trade (MOIT) and the United Nations Industrial Development Organization (UNIDO) to implement the boiler efficiency evaluation as well as the boiler efficiency improvement solution.
The steam system of VINAPAPER was identified as a key energy user of the company, with the fuel cost for steam systems accounting for nearly 30% of overall energy costs.
Boiler fitted with economizer
The steam system consists of 2 chain grate boilers, each with a capacity of 15 tons/hour. These boilers run alternately, providing steam for the production process and operating at a pressure of 11.5 bar. These boilers are equipped with an economizer to use waste heat from flue gas, leading to increased boiler efficiency.
Within the facility, steam is used to dry paper rolls, accounting for nearly 90% of the total steam production, and heating for the DIP line.
System system diagram
The boiler efficiency evaluation done by national experts trained by the UNIDO Project
Under the framework of the Expert Training Program on Boiler Efficiency Evaluation Technique, two national experts were sent to the Company to do boiler efficiency assessment of one operating boiler during 27-31 March 2017 with the backup provided by an international expert. The findings of this assessment are as following:
- Boiler is operated in sufficient load;
- Temperature of flue gas is varied from 160oC – 200 oC. So, it is not sufficient for more heat recovery from flue gas;
- Oxygen content is quite stable but very high at about 14.66%;
- Feed water is in very bad condition and blowdown is not sufficient.
Based on the data collection and findings, some energy saving solutions were made as following:
- Retrofit the feed water treatment system and install an automatic blowdown system.
- Tuning the combustion process for lower excess air or lower oxygen content in flue gas.
After consideration of energy saving opportunities recommended by consultant team, the factory has tried to control O2 content in flue gas with following activities and results.
The Methodology of O2 control done by factory’s boiler operators with technical assistance of the UNIDO Project is presented as below:
- Keep thickness of coal fuel at the minimum acceptable to supply steam for production process. Check the ash removal to ensure complete combustion.
- Check the combustion situation in the combustion chamber through the chamber doors.
- Reduce the frequency of both fans to ensure the pressure of combustion chamber do not too much higher or lower than atmospheric pressure (ensure the flame do not coming out of the doors (higher than atmospheric pressure) or use a very light materials such as a small piece of cloth and put it in front of the door and the cloth should not be drafted into the chamber).
- Check the situation of combustion chamber and change the valves below the win box to make sure the combustion is in good condition (should ask the cooperation of the boiler operators in this activity because they have experience).
- Measure CO and O2 of flue gas by using the Bacharach. If CO is high and O2 is also high (more than 8%), try to control valves at win box. If CO is high and O2 is low (<4%), you can increase frequency of fan). The target is both O2 and CO is low.
- Record all parameter of frequencies, thickness of coal, CO and O2 each time of changing and make up as boiler operating procedure. Instrument used is the combustion analyzer – Brand name: Bacharac and Testo 330-2LX.
The factory has tried to control the O2 content and it took 2 weeks to try and correct. The result of the tuning activity is that the O2 content reduce from 14.66% to about 12%. Actual coal consumption reduction of factory shows that coal consumption every day reduce from 23 – 24 tons/day to about 21.5 tons/day after the flue gas O2 reduction.
It is no cost solution, but resulting the annual energy savings of approximately 700 tons of coal, an equivalent saving of 1,200 million VND (~US$ 51,600).
Production line with 10 bar steam pressure
VINAPAPER Limited Company
Tan Chi Industrial Complex, Tan Chi,
Tien Du, Bac Ninh
Tel +84 241 3 726 666
Fax +84 241 3 721 668
The project “Promotion of Energy Efficient Industrial Boiler Adoption and Operating Practices in Vietnam” by the Ministry of Trade and Industry and UNIDO.
Project Management Unit.