The economical and efficient use of energy in industrial production in general and in the production of building materials in particular has been carried out throughout the business development process of the industry. Vietnam's construction material manufacturing sector in general has a fast development rate, with a modern technology level equivalent to or nearly equivalent to the world's technology level. Energy consumption in the production of building materials is very large with two main forms of energy: electricity and thermal energy (provided from burning fuels: coal, LPG, CNG, oil); in the cement industry alone, the cost of electricity accounts for 5-37%, the cost of heat energy accounts for 45-55% of the total cost of production. This article outlines the current state of energy use and solutions to improve energy efficiency in the production of building materials in Vietnam.

1. Current status of energy use in the building materials industry

a) Production technology

Currently, all cement production lines in Vietnam are produced by dry method, rotary kiln, and cyclone heat exchanger tower; This is the most advanced kiln technology in the world today.

Figure 1. Cement plants with modern technology are gradually replacing outdated technology factories.

(Photo: ximang.vn)

Popular technologies in the production of ceramic and granite tiles in our country today are: Raw material processing by wet method, spray drying to create powder, carpentry forming on hydraulic presses, quick drying by vertical drying. or multistage roller kiln, decorative glazed (for ceramic tiles) and quick fired by roller kiln. In recent years, a number of factories have invested in raw mills according to the dry method, combined drying and grinding.

Sanitary ware production units are typically very old (as of the time of data collection), the oldest line is from 1950 and the latest line is 2018. However, to meet production needs have also improved during the operation. The technology and equipment identified for the main equipment are the kiln and drying system. Basically, sanitary ware production lines in Vietnam have two main technologies: China and Italy, in addition, there are also some German or Vietnamese production lines that are partially manufactured. Sanitary ware manufacturers all use LPG/CNG fuel or a mixture of these two types of fuel for the production process.

The construction float glass production units are all under 10 years old, installed and operated from 2010 to present. Technology and equipment of some units are synchronized, modern and originated from European countries, some units have asynchronous equipment, imported from many different countries.

b) Energy consumption (1-2)

The level of energy consumption of building materials production industries depends heavily on technology and capacity scale.

For the cement industry: The average heat energy is about 800 kcal/kg clinker, depending on the capacity of the kilns. For kilns with a capacity of 5,000 tons of clinker/day (equivalent to 1.8 million tons of cement/year) or more, the average heat consumption is about 755 kcal/kg clinker. For kilns with a capacity of 3,000 - 4,500 tons of clinker/day (equivalent to 1.0 - 1.6 million tons of cement/year), the average heat consumption is about 820 kcal/kg of clinker. For kilns with a capacity of 2,500 tons of clinker/day (equivalent to 0.91 million tons of cement/year), the average heat consumption is about 850 kcal/kg of clinker. For kilns with a capacity of 300 - 1,750 tons of clinker/day (equivalent to 0.25 - 0.65 million tons of cement/year), the average heat consumption is about 930 kcal/kg of clinker. Average power consumption is 95 kWh/ton of cement. Factories investing in a system using furnace exhaust heat to generate electricity have saved 20-30% of the plant's electricity usage.

For the ceramic tile industry, heat consumption is from 1076-1598 kcal/kg of product, and power consumption is from 111-190 kWh/ton of product.

For the granite tile industry, the heat consumption is from 1326-1667 kcal/kg of product, and the power consumption is from 224-360 kWh/ton of product.

Fuel and energy in ceramic tile products are mainly coal, liquefied petroleum gas (LPG), natural gas CNG and electricity. Fuel and energy costs account for a large proportion of 30-35% of the total cost of ceramic tile production. Power consumption is average.

For the sanitary ware manufacturing industry, the heat consumption is from 1930-2347 kcal/kg of product, and the power consumption is from 343-689 kWh/ton of product.

For the float glass manufacturing industry, the heat consumption is from 1783-1843 kcal/kg of product, and the power consumption is from 146-156 kWh/ton of product.

2. Management solutions and technologies to improve energy efficiency

            a) State management solutions

            Vietnam has promulgated the Law on Economical and Efficient Use of Energy (Law No. 50/2010/QH12) regulating the economical and efficient use of energy; policies and measures to promote economical and efficient use of energy; rights, obligations and responsibilities of organizations, households and individuals in economical and efficient use of energy... Accordingly, industrial production establishments must develop and implement plans for using energy energy saving and efficiency every year. Decree No. 21/2011/ND-CP also stipulates that key energy users must develop annual and five-year plans on economical and efficient use of energy; formulating and implementing measures for economical and efficient use of energy according to established objectives, policies and plans.

The Prime Minister has approved the development strategy of building materials in Vietnam for the period to 2050 according to Decision No. 1266/QD-TTg. Whereby:

Period 2021 - 2030:

Tile industry: Heat consumption for 1 kg of product: Ceramic tile: ≤ 1,100 kcal/kg product; Granite bricks: ≤ 1,200 kcal/kg product; Cotto bricks: ≤ 1,400 kcal/kg product. Power consumption for 1 kg of product: Ceramic tile: ≤ 0.12 kWh/kg product; Granite bricks: ≤ 0.30 kWh/kg of product; Cotto bricks: ≤ 0.14 kWh/kg of product.

Sanitary ware industry: Thermal energy ≤ 2,300 kcal/kg product. Electricity ≤ 0.5 kWh/kg product.

Construction glass industry: Heat consumption < 1500 kcal/kg product; Power consumption < 100 kWh/ton of product.

The period 2031-2050

Tile industry: Using clean fuel in the production of ceramic tiles, no longer using coal gas as fuel.

Sanitary ware industry: heat energy consumption: ≤ 2,000 kcal/kg product; Power consumption: ≤ 0.4 kWh/kg of product.

Construction glass industry: Continue to invest in-depth in existing glass production facilities, invest in new high-quality products with high economic value, especially glass products suitable for green architecture, energy saving.

The regulatory agencies need to implement the contents specified in the issued laws, decrees and strategies.

b) Management and technical solutions at the factory (2)

Install energy monitoring meters. The factory needs to monitor the energy monitoring and calculate the energy consumption rate on the monthly production output, monitor the energy loss in each area to find the cause and fix it in time.

Develop a plan for sustainable energy use. These goals aim at measurable outputs and are therefore comparable to the goal itself.

Enhanced internal management and equipment maintenance. Regularly propagate and train employees on energy saving. Increase operator involvement (power saving should be based on a broad basis and must be supported by operators).

Measure and list the areas that consume a lot of electricity (such as press engines, crushers, compressors, ...) along with electricity consumption to control and evaluate regularly, areas that consume a lot of electricity. . Install automatic controls to turn off equipment when not in use.

Develop an energy management system in accordance with ISO 50001 to help manufacturers establish the systems and processes needed to improve energy performance, including energy use, consumption and efficiency

c) Technical solutions (2)

Manage, maintain, maintain, monitor, measure, calibrate, upgrade ... electrical equipment to minimize energy loss. Optimize air compressor system, replace old air compressor with high efficiency air compressor.

Install and set up inverter system for equipment, equipment system operating intermittently, often running with relatively large load fluctuations.

Some solutions to reduce energy consumption for some specific building materials manufacturing industries are as follows:

Figure 2.The residual heat generating area of Xuan Thanh Cement Joint Stock Company

(Photo: ximang.vn)

Cement production: Using multi-channel nozzles, Raise the secondary air stream temperature; Reducing the calcination temperature by using mineralizing additives to reduce the temperature of clinker mineralization, using highly active raw materials, making blends with low agglomeration temperature, and reducing NOx gas generation; ensure that the kiln firing process is stable; Improve the secondary air flow temperature to save fuel, reduce NOx; Improve furnace

productivity to reduce heat loss through furnace walls, invest in a system to utilize excess heat from waste gas to generate electricity; Production of high-grade clinker reduces the amount of clinker used in cement.

Production of ceramic tiles: Insulating the furnace shell, reducing the life of the furnace shell; Make the most of the waste heat from the kiln to be reused for different stages for the production process of drying raw materials (spray drying), drying, and supporting the combustion process for the kiln; To replace consumed fuels, use LPG, CNG and new fuels to gradually replace traditional fuels with large emission levels (coal, oil); Install an automatic system to control humidity and temperature, the temperature distribution process in the drying and firing oven; Use heating auxiliaries suitable for each type of product; Using water-saving additives reduces water (approximately 3%), thermal energy (approximately 90 kWh/t product) and electricity (approximately 1.5 kWh/t product) [3].

Production of sanitary ware: Insulate the furnace shell well so that the oven shell does not heat > 50 0C; Set the optimal firing curve. The potential savings from this area can be around 5-10% [4]; Use heat pump for lake processing area.

Glass production [5] : Process optimization, through control of operating parameters, loss control, 10% reduction in total energy demand; Use low NOx emission burners.

In order to ensure energy efficiency and maximum savings in consumption, it is necessary to invest in modern and advanced technological equipment, and to remove outdated technological equipment.

3. Recommendations to improve energy efficiency in the building materials industry

Although there is a Law on Economical and Efficient Use of Energy to promote and support efficient use of energy, the enforcement is not thorough; For units that do not perform, there is no appropriate reward and punishment method. Therefore, the management agency needs to issue a reward and punishment mechanism and implement it thoroughly.

The potential solutions in all building materials manufacturing industries are vast and technically feasible. However, economies of scale, investment value and funding resources are fundamental barriers to these solutions. The level of economic barriers also depends largely on the development orientation as well as the potential of each production unit. Therefore, management agencies need to issue appropriate support and encouragement policies.

The management agencies need to review the current status of implementation, evaluate the effectiveness, difficulties and obstacles in the implementation of relevant laws, decrees and strategies to make appropriate adjustments to the actual situation.

The tree management agencies set the energy consumption norms for the industry, as a basis for the units to implement.

Many production units do not have enough staff, workers with knowledge and experience in high technology and good energy management. This is a major technological barrier. Therefore, it is necessary to train technical and managerial staff in technology and energy engineering.

Production units need to actively implement regulations, develop plans and implement solutions to use energy efficiently and effectively every year.

4. Conclusion

            Implementing activities to improve the efficiency of economical and efficient use of energy is the right direction according to Vietnam's policy, in line with the world's trend. All countries have policies to encourage and enforce efficient use of energy depending on actual conditions.

Building Materials Institute is a leading unit in the field of building materials, will continue to research, develop, and apply energy-efficient solutions in the production and use of building materials. Time to cooperate with other countries to develop standards, assessment and testing methods, and to advise on developing development orientations suitable to Vietnam's conditions./.

MSc. Nguyen Thi Tam, MSc. Cao Thi Tu Mai (Institute of Building Materials, IBM)

& Vietnam Energy Conservation and Energy Efficiency Association

References:

1. Decision No. 1266/QD-TTg dated August 18, 2020 of the Prime Minister approving the Strategy for development of building materials in Vietnam in the period of 2021 - 2030 with orientation to 2050".

2. Nguyen Thi Tam, Cao Thi Tu Mai, 20120, Report on building energy consumption norms for the building materials industry, Institute of Building Materials

3. 2021, Reference Document on Best Available Techniques in the Ceramic Manufacturing Industry, European IPPC Bureau

4. Scalet B, Garcia Munoz M, Sissa A, Roudier S, Delgado Sancho L. Best Available Techniques (BAT) Reference Document:for:Manufacturing of Glass:Industrial Emissions Directive 2010/75/EU:(Integrated Pollution Prevention and Control) . EUR 25786 EN. Luxembourg (Luxembourg): Publications Office of the European Union; 2012. JRC78091

5. Law on economical and efficient use of energy No. 50/2010/QH12 passed by the 12th National Assembly on June 17, 2010 and took effect from January 1, 2011.

6. Decree No. 21/2011/ND-CP dated March 29, 2011 of the Government detailing and implementing measures for the Law on Economical and Efficient Use of Energy.