It seems obvious that China, the country with the world’s largest population and fastest-growing economy, would lead the world in cement production. China’s dependence on cement, producing and consuming 60% of the world’s cement, is understandable considering concrete is key to meeting the needs of the country’s megacities, expansive roadways, and other infrastructure.
Interview with Changming Gao, Senior Consultant
with the Chinese Cement Association
Following industry leaders
Most of China's top 10 cement producers are deploying their own intelligent cement production demonstration lines, with the purpose to promote the development of the entire industry. For example, China Red Lion Cement Co., Ltd (the 7th largest cement producer in China) is discussing a complete upgrade of its plant into a smart plant. Smart plant transformations typically include fuel and energy substitution, digitalization, new equipment, process engineering and automation.
Such massive modernisation retrofits have brought the performance and quality level of Chinese manufacturing equipment quite close to European suppliers. “Generally speaking, the gap between European and Chinese products is below 10%, and for some equipment, it’s equivalent,” says Mr. Gao. It’s not all about efficiency either; it’s about meeting strict sustainability standards, including reducing emission levels.
Out with the old
Today, according to Gao’s sources, China has 210 cement kilns with a capacity of less than 2000 tpd and a clinker production capacity of 57 million tpa, which accounts for 3.2% total capacity.
Moreover, China has around 125 cement kilns of less than 2500 tpd with a clinker production capacity of 77 million tpa, which amounts to 4.3% total capacity. These cement plants were built in the 1990s before a big wave of technological advantages emerged. These plants consume a lot of energy, produce high amounts of emissions, have low production efficiency, and have lower economic returns than newer plants. The China Cement Association plans to phase out all of these older plants within three years, which will reduce clinker production by 7.5% (134 million tpa). That’s the equivalent of reducing cement production capacity by 210 million tpa.
Emit less
Cement plant emissions are a significant problem everywhere, not least in China. China’s Ministry of Environmental Protection (MEP) found the cement industry contributed 15-20% of PM2.5 (particulate matter smaller than 2.5μm), 3 to 4% of SO2 and 8 to 10% of NOx to the country's total emissions.
However, since the beginning of this century, the Chinese government has revised the acceptable levels for pollutant emissions from the cement industry to the current maximum limits: (MG/NM3)
100 DUST – 200 SO2 – 800 NOx
Different places, different standards
But enforcing these limits in China is more complex than a single, state-wide standard, points out Gao. Some areas have different emission standards, many of which are even stricter than national standards. For example, the current emission standards differ among the coastal developed areas and the less-developed northeast and northwest areas. This is a key reason some plants produce even lower levels of emissions. Notably, about 3 to 5% of China’s cement plants have achieved ultra-low emissions and an estimated 10-20% of China’s plants are below the national standard indicators.Emission levels from 3-5% of China’s cement plants (MG/NM3)
10 DUST 30 SO2 200 NOX
Est. emission level differences from underdeveloped northeast areas and northwest areas (MG/NM3)
20~50 DUST 50~100 SO2 300~600 NOX
Not wasting waste
China’s cement production industry is not only focused on reducing emissions, but is also consciously trying to reduce the amount of non-renewable energy required to run its cement plants. Gao reports that the country has more than 60 cement kilns in operation that co-process municipal waste, with five million tpa of crude garbage disposed. This accounts for 2.5% of the total municipal waste collected.
Though these numbers may seem substantial, China’s municipal wastes are not separated, and therefore the moisture levels of the waste are very high (nearly 50%) and their calorific value is very low (1200Kcal/kg). In fact, this five million tpa of garbage is equivalent to only about 700,000 tonnes of effective standard coal. The Thermal Substitution Ratio (TSR) provided by the national cement industry, alternative fuel is about 1.6%, which, according to Mr. Gao, is still low compared with the TSR of more than 30% in Europe and 70% in Germany.
“Most of the cement industry in China understands there is a long way to go and a lot of room for improvement,” states Mr. Gao. At present, China’s top 30 cement companies have nearly 600 cement kilns. Even if state subsidies do not increase, the China Cement Association estimates the number of cement kilns for co-processing waste would increase to 200 by the end of 2020. This co-processing increase could increase the total amount of garbage disposal to 25 million tpa.
Waste co-processing options
Two main technical methods for co-processing waste preside in China's cement industry, explains Gao. One pre-processes the raw waste and feeds it into the gasifier for combustion. The hot gas is introduced into the precalciner, as a heat source to the kiln system. This is an offline system with low thermal energy utilisation. The other is an online system that directly feeds the raw waste into a precalciner for combustion. The heat generated in this second method is directly used in the kiln system, which can double the heat utilisation rate. Gao believes that China’s experience with transforming its cement industry to be able to integrate co-processing raw waste is of great value to many developing countries. Typically, these countries do not have a specialised industry for preparing refuse-derived fuel (RDF).
Shutdown innovation
China’s cement plants are attempting to meet market demands, while simultaneously focusing on sustainability and compliance with legislation, stresses Gao.
For five years, the ‘defending the blue sky’ production suspension scheme has been in practice. This involved cement plants in some areas shutting down for one to two months during the winter period to avoid the superposition of pollutants generated and minimise the impact on air quality.
Now, says Gao, the main strategy is a ‘peak-shifting shutdown’ scheme, which is meant to regulate the supply of cement in the market to maintain or increase cement prices. As a result, more areas have joined in pursuing this peak-shifting shutdown and the shutdown time has also extended.
However, to avoid the accumulation of garbage, some cement plants that co-process municipal waste are exempt from this shutdown. Other plants, however, are shut down during the specified production suspension period regardless of emission levels.
“Some believe those plants should be treated differently according to their emission levels,” says Gao. “Others believe it’s a matter of technological advancements that can reduce energy use or pollution emissions.”
A common objective
The idea is that plants with advanced, efficient equipment should be stopped for less time or even exempt from the shutdown period, while plants with outdated facilities should be shut down or even completely stopped. Yet, current Chinese regulation does not dictate that all cement plants must abide by this ‘single solution’ approach, says Gao. The ultimate aim is to not only encourage the enthusiasm of plants to widely apply equipment with ultra-low emissions, but also discourage and eliminate outdated production capacity. With the modernisation of plant equipment driven by a huge focus on lowering emissions and consuming alternative energy sources, there’s no doubt the world is seeing an important shift in the Chinese cement industry.
Keep exploring