Potentials and strategies for energy-saving and CO₂ emission reduction
in the Chinese lime industry

1 The present situation in the lime industry

The lime industry in China (Figs. 1–3) consists of three sectors. The first sector comprises the metallurgy industry (steel  and iron industry). They produce lime for their own use. With low energy consumption and high quality, domestic advanced lime technology equipment mainly focuses on steel and iron enterprises. The second sector comprises companies from the ­chemical engineering industry. Here also they use most of the lime themselves. Shaft kilns with steel shells are the most important technological equipment in use, which is made in China. The third sector covers companies from the building materials industry, which mainly produce material in earthen kilns that is characterized by poor quality and high-energy consumption. Except for the use of construction and architectural products, these limes could not compensate for lime shortages in the chemical engineering industry and the metallurgy industry.

 
The sustainable development of the economy and society has advanced scientific progress and structural adjustment in the lime industry. In the past “Tenth Five-Year Plan”(2000 –2005) period, rapid increases in the productive output of steel, plastic, and aluminium have invigorated the development of the lime industry. Thanks to the use of lime in the abatement of flue gas oxides of sulphur and in the treatment of the acidity in industrial effluents, lime works gained enormous room for development. The proportion between industrial lime and constructional lime is reversing and is similar to that of developed countries (Figs. 4–5). Lime consumption (use level) from 2001 to 2010 is shown in Table 1. There are more than 5000 lime works in China at present, and most of them are small scale production facilities for the production of lime used for building or construction materials. The figures for lime for architecture and construction are estimated, whilst the figures for lime for other industries are comparatively precise.

 
As regards construction and building materials: expressways and highways for urbanization require a great amount of building lime, while lime consumption for housing construction, which consumed the largest proportion of lime in the past, is decreasing. In this situation, the overall amount tends to be more or less evenly balanced. Therefore, there is no obvious increase and decrease in lime consumption  in those two sectors. However, there is a decreasing proportion of this industry sector.

 
2 Energy-saving and emission reduction potentials
in the lime industry

2.1 Current energy consumption in the lime industry

The fuel used in the lime industry in China, solid fuel in general, is normally anthracite coal with a high calorific value. ­Because coal is in short supply, lime manufacturers acquire materials locally. For example, coal is replaced by bituminous coal or inferior coal as a replacement fuel in the north-eastern and western areas. Lime works in the metallurgy industry mix low calorific value blast furnace gas and coking gas together for calcination. The fuel types used at present in the lime industry in China can be seen in Figure 6. In Figure 7, the fuel types predominantly used in Europe are shown.

In 2006, the heat consumption was about 24 million tons of standard coal, the power requirement about 3 million tons of standard coal and the total energy consumption about 27 mil­­lion tons of standard coal in the lime industry in ­China ­
(Table 2). The total energy consumption in the building ma-terials ­industry in China is about 223 million tons of standard coal. In terms of the energy consumption rate, the lime industry accounts for 12.11  % in the building materials industry, which is equal to 1.11  % of the total energy consumption in China.

 
2.2 Estimation of CO₂ emissions in the lime industry

In the process of conversion from limestone calcinations
(Figs. 8 and 9) to lime, a large amount of CO₂ will be emitted; during the process of which a great amount of energy (mainly including coal as well as natural gas, petroleum, and other fuels as replacements) will also be consumed, and a certain amount of CO₂ will be emitted. At present, the average process CO₂ emission in China (Table 3) is 1.17 ton CO₂/t lime while the respective value is about 0.75 t CO₂/t lime abroad. This difference is mainly attributed to the disparity between the composition of the limestone and the degree of calcination.

2.3 The main problems in the lime industry

The current problems in the lime industry can be divided into four categories:

1. The antiquated technology and equipment:

The lime produced in earthen kilns accounts for more than 60  % of the total output. It is also an issue requiring urgent solutions for energy consumption reduction and an overall ­advancement in technology in the lime industry.

 
2. The small-scale enterprises:

China’s lime output has a leading position in the world. However, the technological level of China’s lime industry is still far below that of the developed countries.

3. The imbalance in development:

Most ­investments in the lime industry go to lime factories in steel enterprises; the products of which, however, don’t enter into the lime market. The enormous investment hasn’t fully fulfilled its function in promoting an overall balanced development of the lime industry in China.

 
4. The lack of professional lime research institutions and organizations:

Today, high-tech production equipment is still being imported. This is disproportionate to China’s position as a large lime producing country.

 
3 Prediction of demand

3.1 Steel industry

The newly established steel and iron policy encourages cross-regional reorganization among large-scale steel corporations, and over 20  % of antiquated capacity are to be eliminated through selection in the structural adjustment of the steel industry. Therefore, technological transformation projects and new ­projects will continue to increase. In addition, people will be more concerned and will attach more importance to lime, because it is the important auxiliary raw material for steel­making. In 2010, the crude steel output expected will be over 300 million tons; accordingly, lime for metallurgy will be over 5 million tons.

3.2 Calcium carbide industry

In recent years, an ever-increasing oil price on the international market has become a heavy burden for the rapidly growing PVC industry. Since 2003, the method of producing ethane by the oil process has gradually given place to that of calcium carbide. Calcium carbide output reached 10 million tons for the very first time in 2006. The calcium carbide industry has already become the second largest consumer of lime.

3.3 The chlorine and alkali industries, precipitated calcium carbonate and building products, such as aeroconcrete, etc.

Outputs of chlorine  and alkali, precipitated calcium carbonate and building products, such as aeroconcrete, etc. have been increasing steadily and continuously during recent years, and the demand for lime is correspondingly increasing.

3.4 Lime in environmental protection

Because of China’s determination regarding environmental protection and the progress made in this respect, in 2006 there was an increase in the use of lime in this field. Lime for the reduction of sulphurates in power utility plants has undergone rapid development.

3.5 Expressways and urbanization

As a basic material for the construction of expressways, inter-town highways and housing in the new villages as well as base material, lime still plays an important role in bricklaying and whitewashing for brick and concrete construction. However, lime is gradually withdrawing from its historical role in urban construction. In recent years, there has been a lower negative growth in the total amount of lime in the field of construction, but a change in the total amount is not yet clearly obvious.

 
4 Suggestions and strategies

We can promote energy saving and CO₂ emission reduction in the following ways:

 
1. Adjustment of the industrial structure, which will limit small-scale production and promote the marketing of modern methods of production:

Small-scale production and earthen kilns should be withdrawn or limited according to the regional economic situations. In the meantime, lime production and the administration of large-scale steel enterprises should be accelerated and moved into the national lime market so as to facilitate progress in the lime industry.

 
2. Progress in technology:

We should improve research and development in the lime industry. Based on the imported technology and equipment, more emphasis should be placed on the development and promotion of the existing technology. At the same time, modification of semi-mechanical and mechanical vertical kilns should be promoted, and the earthen kiln should be eliminated. We should develop high-quality lime production technology and improve recycling technology for lime by-products.

 
3. Full use of quality limestone resources.

 
4. Adoption of  the use of various fuels in lime rotary kilns:

Lime calcinations should be adapted to multi-fuel requirements, and particularly, it should be made possible to utilize gaseous fuel with low calorific value.

5. Ful use of the waste heat in the lime rotary kiln, which comes from waste gas in the preheater of the kiln:

This refers to medium- or low- temperature waste heat, which up to now has not been fully utilized.