If all the thermal power plants in Vietnam apply the new coal mixing formula, the savings will be huge. The proposed solution has been tested successfully in Ninh Binh Thermal Power Plant.

Anthracite coal mixed with imported combustible coal to increase combustion efficiency and to reduce coal consumption is the scientific studied thesis, presided over and conducted by Prof. Dr. Truong Duy Nghia - Chairman of Thermal Technical Sciences of Vietnam. The studied subject is supported by the Ministry of Science and Technology.

At the announcement of the initial results of the thesis "Research into the combustion technology for burning the mixture of nonflammable coal and the imported flammable coal in order to improve the fuel efficiency at coal-fired thermal power plants in Vietnam", the Deputy Prime Minister Hoang Trung Hai appreciated the achieved results. According to the Deputy Prime Minister, the finding of new mixing formula for coals will ensure the economic objectives, improve operational efficiency of the plant, helping the thermal plants become more proactive to go in search for fuel sources. 

As the Project leader - Prof. Dr. Truong Duy Nghia - said: At present, coal-fired thermal power plants in Vietnam use only one type of coal throughout the "life cycle" of the plant, and the fuel coal is within a template choice as specified from the design stage. Coal used in most thermal power plants in Vietnam today is the anthracite - a difficultly flammable coal. If mixing it with the imported coal of the same type, there is no technical problem, but mixing it with other coal types, it can be a big problem.

However, the team has found a solution for Vietnamese anthracite coal mixed with bituminous coal importedfrom Indonesia. This technique reduces the negative indicators of domestic coal (such as reducing the amount of ash), thereby improving the combustion, increasing combustion efficiency and reducing coal consumption. The experiments in Ninh Binh Thermal Power Plant initially brought about unexpected successes.

For a clearer description of the experiment, Engineer Trinh Van Doan - Director Ninh Binh Thermal Power Plant said: "The Plant performed the coal mixing in accordance with the proportions as specified by the scientists. All the work shifts of boiler operation are arranged in compliance with the test operation mode conducted by the board of researchers, directly carried out under the leadership of team leader and the experimental data is recorded. The results show that, during the burning of the mixed coal, the boiler operates with safety and stability. The adjustment of the capacity whether to increase –or to decrease the load, is convenient, and easy. The mixed coal gets ignited earlier than the domestic coal does, the combustion chamber is very stable."

Especially, Engineer Doan affirmed that the efficiency of the boiler was more even between the loads, and added an increase from 2% to 5% of capacity as compared to domestic coal. In the experiment, the mixing ratio of 10-20% of imported coal has been recognized as giving the best operating mode for boilers in Ninh Binh Thermal Power Plant, the average efficiency of 84-85%. In case of purely domestic coal burning, the combustion rate was only 82%.

"NOx content in the flue smoke decreased by 10-15% compared with 100% in case of domestic coal burning. In the process of burning coal mix, it does not produce the slag, slag flows, or slag falls. The automatic slag discharge system of the boiler shows its stable operation. The electrostatic dust removal system works better as the input dust concentration is reduced below the norm "- Engineer Doan said.

For accurate and objective indicators, Ninh Binh Thermal Power Plant had prepared tables for recording the process parameters during experiments, built up the processes with assignments given to the experimental units. The experimental boiler systemwas isolated for performance to ensure the highest accuracy.

Huge savings of coal if scaled up 

The Minister of Science and Technology Mr. Nguyen Quan says that it is a research theme of importance to science and technology programs at state level, presided over by the Ministry of Science and Technology. The outcomes are of great significance for energy efficiency as well as for improvement of energy use in Vietnam - especially when we are experiencing difficulties in meeting the energy needs for industrialization.

"When we mix a certain percentage between imported coal with domestic coal, it can enhance the productivity and efficiency of coal burning for boiler and furnace, also applicable to fluidized combustion control mode 1-3%. It can be said that we are saving 1-3% of fuel used for combustion boilers in thermal power plants. If the technique is applied universally to all thermal power plants currently operating in Vietnam, it will save huge amounts of coal, especially in the context of coal being imported. "- Minister Nguyen Quan said.

The Minister of Science and Technology also suggested that the team should review the results of the study, and make proposal to Coal and Minerals Corporation of Vietnam so that the solution could be applied universally in all thermal power plants in the near future.

In recognition of the initial results of the research, the Deputy Prime Minister Hoang Trung Hai said that the team should obtain the feedbacks, reviews, and supplement the research with a financial effectiveness report. The Deputy Prime Minister also encouraged to implement similar schemes, promoting science and technology to increase the value of production, reducing greenhouse gas emissions, ensuring environmental preservation.

"The outcomes of this research will be the basis for further studies in order to improve optimal operation mode when switching from anthracite coal into mixed coal for fuelling. The thermal power plants,which are designed to burn imported coal, should also study to use mixed coal, towards reducing the import of bituminous coal and replaced with domestic anthracite coal"- Deputy Prime Minister Hoang Trung Hai gave the guidance.

Mr. Nguyen Khac Son - General Director of Power Generation Corporation 1 - also reveals that in the long term, thedomestic coal resources are not sufficient to meet the demands of ProjectDuyen Hai 1 and Project Vinh Tan 2. Therefore, the corporation must do research and apply the solution of mixed coal for Project Duyen Hai 1. The research will focus on finding out the type of imported coal, whichcan be mixed with coal dust 6a.1 to ensure economic effectiveness and slag-free operation of the boiler. 

"The bituminous coalas a planned supply to Project Duyen Hai 3 and Duyen Hai 3MR 3 potentially produces clogging of slag, thus study on the appropriate mix with other coals should be conducted to reduce the risk of boiler slag " –Engineer Son affirmed.

Mr. Son also suggested that the scientists need to do the researches, in-depth experiments on mixed coal combustion technology to ensure the stable operation of boiler and power production cost optimization.

Trong Tan