Low-carbon transition technology path: fuel substitution

The development process of fuel substitution

Fuel substitution technology is a mature carbon reduction technology in cement industry. From a worldwide point of view, Europe is in the leading position, with an alternative fuel replacement rate of about 39%, followed by Brazil and North America, about 5%, while China's cement industry fuel replacement rate is less than 2%, which is at the bottom.

At present, the development of fuel substitution technology in China's cement industry is relatively backward, and it is still in the stage of using cement kiln collaborative disposal technology. Due to the low quality of waste pretreatment and disposal, the calorific value of the "alternative fuel" produced by the collaborative disposal line of cement kilns constructed by most cement enterprises fluctuates greatly, which has a great impact on the operation of the cement clinker production line, and fails to meet the internationally recognized quality standard of alternative fuel.

1. Biomass fuel

Biomass is a general term for all plants, microorganisms, some animals and their waste. Biomass fuel refers to solid, liquid or gaseous fuels extracted from biomass. The biomass substitute fuels commonly used in cement industry are mainly: straw, rice husk, waste wood, agricultural and forestry waste, etc. Unlike traditional fuels such as oil and coal, this new biofuel is a renewable fuel and is less likely to cause environmental pollution than other fuels.

Biomass fuel has the characteristics of carbon neutral, renewable and environmentally friendly (low carbon content, no sulfur, heavy metals and other elements), and has become one of the important directions for the development of cement companies in the future.

China is rich in biomass resources, which can produce about 829 million tons of straw every year, of which about 694 million tons can be collected; 9.604 million tonnes of the forestry residues produced could be used for energy in the future; In the future, when combined with CCUS, it can become a carbon-negative technology. In short, China's biomass fuel carbon potential is huge, but due to the biomass fuel has high calorific value volatility, difficult recovery, poor combustion stability and other characteristics, biomass alternative fuel in China's cement industry has not been large-scale application.

Foreign biomass fuel replacement process started earlier, Holcim, Cemex, Heildelberg biomass fuel (animal bone meal, crops, wood chips and other crops) in the alternative fuel accounted for more than 15%. Heidelberg Cement alternative fuels will account for 26.4% of the fuel mix in 2021. Of these, waste-based biomass used accounts for about 42% of the alternative fuel mix. (Holcim and Lafarge were not merged until 2017.)

2. RDF, a refuse derived fuel

RDF stands for Refuse Derived Fuel, that is, refuse derived fuel, which is a harmless solid fuel made by sorting waste plastics, waste paper, waste wood, textiles, etc. from domestic garbage and then breaking, drying and forming them. The calorific value of RDF is 14595 ~ 20016 kJ/kg, which is much higher than that of coal (about 10870kJ/kg), while the average calorific value of China's general municipal solid waste is about 4000kJ/kg. [5] Mr. Gao Min, Technology Center of Chengdu Building Materials Industrial Design and Research Institute Co., LTD., wrote in the article "Technology for Collaborative Disposal of Urban and rural domestic waste in Cement kilns" : "(1) Urban and rural domestic waste is divided into three parts after pretreatment: primary RDF, detrite residue, inorganic heavy matter... ; (2) The organic combustibles obtained by air separation are further broken and processed in multiple stages to make the organic combustibles into primary RDF, without adding any additives (lime powder, pulverized coal, etc.) in the preparation process, and without traditional necessary processes such as drying and molding, simplifying the disposal method."

The American Society for Testing Materials (ASTM) classifies RDF into seven categories based on the degree and nature of waste processing. [6] RDF started early in foreign countries and is now relatively mature. More than 30 RDF power stations have been built in the United States, and many companies in Japan have productized RDF. In China, it is still in the initial stage, and there are few RDF landing projects. In recent years, Chengdu Building Materials Institute and Huaxin Cement have designed and put into operation a number of domestic waste preparation RDF and cement kiln collaborative disposal projects.

At present, the alternative fuel in China's cement industry is in a low stage of development, and the concepts of "RDF derived from garbage" and "combustible waste" are confused. Some people mistakenly refer to the technical model of using cement kilns to cooperatively dispose of raw ecological urban domestic waste in Liyang, Huasinhao Ruiwu, Jinyu Handan, Finland, and so on, as "RDF". (The collaborative disposal technology of cement kiln is to formulate targeted disposal plans according to the physical form, packaging method and chemical characteristics of the hazardous waste to be disposed of, respectively from the raw mill, decomposition furnace and kiln door cover, etc., to realize the harmless disposal process of hazardous waste while producing clinker or cement.) In the fuel substitution actions of 8 cement head companies at home and abroad, there are actions to use cement kiln collaborative disposal technology for fuel substitution and solid waste treatment. Jiang Xuchang (2021) collected and sorted out the technical models of ten different scale cement kilns for collaborative disposal of urban domestic waste developed by 12 existing units in China, and showed that so far, none of them has applied "RDF" that meets the European standard in a true sense.

Because RDF is produced from domestic garbage, the current garbage classification policy in our country is not popular, but only implemented in some cities. Therefore, the RDF prepared in China has high moisture content and low calorific value, which is obviously different from the international mainstream RDF-5.

In 2020, the amount of domestic waste produced in China is about 310 million tons. According to the calculation of the calorific value of garbage derived combustible material after pretreatment of one ton of domestic waste, China's domestic waste can replace 90 million tons of standard coal after combustion. RDF has great potential for development, and the future RDF industry and standards need to be established, especially the waste pretreatment industry.

Conch Cement (stock code: 600585,00914) through the integration and application of step furnace, hot pan furnace and other technologies, the collaborative disposal and CKK project to upgrade, direct RDF fuel into the kiln, further improve the utilization rate of caloric value. The plan is to replace about 10% of fossil fuels with RDF by 2025.

Holcim and Heidelberg Cement have relatively better solid waste management, alternative fuel production systems and operational management systems. Holcim is working to replace traditional fossil fuels with non-extractive fuels sourced locally, alternative and derived from waste, and is beginning to adopt near-infrared spectroscopy technology that can be used to analyze alternative fuel properties during feeding and compensate for mass changes in real time using the optimal fuel mix. This solution increases the use of alternative fuels, thereby reducing CO2 emissions. Our country should learn from its relevant successful experience and perfect the production standard system and quality control management standard system of alternative fuels.

UltraTech Cement: Use municipal solid waste while increasing co-treatment of industrial waste to reduce the amount of waste sent to landfills or incineration. Using municipal solid waste (MSW) as cement plant fuel, waste-derived fuel (RDF) is becoming increasingly popular in India, where RDF has the potential to replace 15-20% of the primary fossil fuel in its cement manufacturing industry.

In addition, in early 2022, Cemex announced the acquisition of Broquers Ambiental, a sustainable company focused on separating, recycling and treating municipal solid waste generated in the city of Queretaro, Mexico. The acquisition is part of Cemex's Future Action Plan, which aims to become carbon neutral; Cemex is an industry leader in the use of renewable diesel, an advanced second-generation biofuel that is fully compatible with its current fleet and can reduce the carbon footprint of transport by 60 to 80 percent when used at 100 percent.

3. Tire derived fuel TRF

Waste fuel has the advantages of high heat value and low water content, so it is also the earliest alternative fuel for the cement industry. In the 1950s, it was first applied in Germany, and it is now more popular abroad. About 40% of cement plants in the United States are burning waste tires, and about 10% of Japanese waste tires are used as alternative fuel for cement kilns. In Eastern European countries such as Poland and Ukraine, waste tires are used as the main energy source for rotary kilns (the fuel replacement rate is more than 60%). [7]Holcim cement, Cemex cement, Heildelberg cement and Lafarge cement tyre derived fuels accounted for 10%, 16%, 11.6% and 19.7% of alternative fuels, respectively. The waste tires in China are mainly produced by recycled rubber, the comprehensive recovery rate is about 50%, and the proportion of used in cement kilns is less.

Waste tires have high calorific value, low renovation cost, simple process, and the nitrogen oxides emitted by combustion and the heavy metals in ash are less than coal (" China Cement production enterprises greenhouse gas emissions Accounting methods and reporting Guide "has also clearly pointed out that 20% of fossil carbon in waste tires is still included in carbon emissions, 80% of biological carbon is not included in carbon emissions). It is one of the alternative fuels that China's cement industry should focus on developing in the future.

4. Hydrogen fuel

Hydrogen fuel substitution in cement production refers to the replacement of fossil fuel heating with clean energy hydrogen in the clinker calcination process, and the hydrogen is injected into the kiln.

Heidelberg Cement: In 2021, a Cement kiln at Heidelberg Cement subsidiary Hanson UK's Ribblesdale plant successfully operated for the first time in the world in a zero-fuel mix, consisting of hydrogen (39%), biomass components (12% of meat and bone meal) and glycerin (49%) delivered by tanker. The government-funded trial achieved a 100% alternative fuel substitution rate.

Cemex: Cemex is a leader in the use of hydrogen, having started using hydrogen in its plants as early as 2019, and will begin the technical transformation of all its European cement plants in 2020. In 2022, CEMEX invested in HiiROC, a start-up company that produces hydrogen using a unique plasma process and has a low-cost, zero-emission hydrogen production technology. The objective of CEMEX's investment is to increase the hydrogen injection capacity of CEMEX cement kilns, thereby increasing the rate of replacement of fossil fuels by alternative fuels.

Holcim is also working on hydrogen as an alternative fuel.

5. Electricity, solar energy and other new energy heating

For cement production, the use of electric heating is not very feasible from the technical requirements (requiring higher temperature and power), equipment transformation or operational economics, and may not become an important means of emission reduction in the future, but it does not rule out its potential. Solar heating methods are also currently being researched and piloted. Cemex and Synhelion use solar energy to heat a mixture of CO2 - and water vapor to calcinate the clinker; The Cemzero project in Sweden and a project in Norway in 2018 demonstrated the combination of cement production and electric heating.

China Building Materials (Stock code: 03323) : Increase the use of solar, wind and other new energy. For example, Ningxia Building Materials proposed the concept of "zero purchased power factory" through "photovoltaic + wind power + energy storage + waste heat power generation" and built a cadmium telluride photovoltaic power generation system in southwest Lijiang. The Group also promotes the use of renewable energy, using approximately 404,716 MWH of renewable energy during the 2021 reporting period.

China Resources Cement (stock code: 01313) : The Group plans to promote the pilot of distributed PV projects in Guangdong Fengkai and Luoding, Guangxi Wuxuan, Tianyang, Luchuan, Pingnan and other cement production bases, as well as some aggregates, prefabricated construction plants and other suitable locations, and gradually expand to other production bases.

Conch Cement (Stock code: 600585,00914) : In 2021, the Group upgraded the wind power generation system, completed the strategic acquisition of Conch New Energy, and expanded the technology development of energy storage systems and new energy plate business such as photovoltaic power generation, increased the proportion of clean energy use in the process of cement production, further strengthened clean production, and reduced the carbon footprint of products. By the end of the reporting period, the Group had completed 19 photovoltaic power generation projects with a total of 200MW, with an annual cumulative power generation of 164 million KWH.

Heidelberg Cement: Since the beginning of 2021, Heidelberg Cement has signed agreements with pilot projects on various continents to add 150 MW of renewable energy generation from wind and solar, with an expected total capacity of 350 GWH per year. Some of these projects will produce green electricity for Heidelberg Cement from as early as 2022.

Cemex: In 2021, Cemex managed nearly 23 million tons of waste and non-recyclable by-products, nearly 57 times the amount of waste sent to landfills. Co-processing waste in cement kilns as an alternative fuel is a more efficient waste management solution for society than landfill or incineration. Cemex continues to lead the industry in clean power in 2021, with its cement plants consuming close to 30% clean power.

In 2020, thanks to an agreement with PGE Obrot, Cemex's operations in Poland achieved 100% renewable energy supply. In addition, Cemex has extended its agreement with Engie for three years to power its operations in the UK with 100% renewable energy. In cooperation with Synhelion, a Swiss photothermal technology company, Cemex successfully combined the cement clinker production process with Synhelion's concentrator heat utilization system for the first time in 2022. Synhelion is a global pioneer in sustainable solar fuels with a unique technology that converts concentrated solar thermal energy into the hottest heat treatment processes available on the market.

In the future, the development of alternative fuels in China's cement industry will be affected by the price changes of coal and petroleum coke, the gradual popularization of garbage classification, and the improvement of related technologies such as pretreatment technology. If accompanied by the correct guidance of policies, I believe that the fuel replacement of the cement industry will go further and further, and the low-carbon road of cement will also be doubled.