Briques réfractaires avec gangue de charbon et cendres volantes en Chine

Introduction aux dangers et à l'utilisation complète de deux déchets solides, Gangue de charbon et cendres volantes

2.1 Impact on the ecological environment

Coal gangue is piled up like a mountain, causant de graves dommages à l'environnement, écologie, and the safety of people’s lives. The inorganic components of coal gangue are mainly oxides of silicon, aluminum, le fer, calcium, and magnesium, but there are also trace heavy metal elements such as P, Hg, Sn, Cu, Zn, As, Cr, etc. Le stockage d'une grande quantité de gangue de charbon occupe non seulement une grande quantité de ressources terrestres rares, mais libère également des sulfures pour polluer l'environnement, les terres agricoles, et eaux souterraines. L'accumulation d'une grande quantité de stockage au fil du temps et l'augmentation de la température due au chauffage interne entraîneront une fumée dense dans la cour de la gangue de charbon en raison de la combustion spontanée, libérant une grande quantité de gaz nocifs tels que le CO, CO₂, SO ₂, H ₂ S, PAS d'Å dans l'air, avec SO ₂ étant le principal polluant. The massive emission of harmful gases not only endangers the surrounding environment and air quality, affects the physical health of the mining area and nearby residents, but also affects the surrounding ecological environment, causing slow growth of trees, severe crop yield reduction, et dans les cas graves, tree and crop death. In addition to combustion, heavy metals are acid water generated by rain erosion, which flows into rivers or infiltrates into soil, causing groundwater and Soil contamination pollution. Another characteristic of coal gangue stored in the open air is its susceptibility to weathering and fragmentation. Some form fine particles of ash after spontaneous combustion, which undergo a series of complex reactions such as oxidation, decomposition, dehydrogenation, and condensation to form carbon black, cendres volantes, and particulate suspended solids, forming haze and directly affecting the local environment and people’s health.

Cendres volantes, like coal gangue, is widely piled up in many places. Encountering strong winds and flying coal ash is a prominent environmental pollution problem that many places urgently need to solve. China has become a major coal producing country and the country with the highest coal consumption worldwide, as well as the country with the largest use of coal to produce waste fly ash. Due to the fact that fly ash generated by thermal power generation has become the biggest source of pollution for industrial solid waste, the placement of fly ash also requires the use of large areas of land, resulting in waste of land resources, and can have adverse effects on the surrounding air, water quality, and soil.

2.2 Overview of Comprehensive Utilization

Large amounts of land acquisition or the discharge of coal gangue and fly ash in mountain valleys will become history, and its way out is resource utilization. In the past 20 années, the government has issued many regulations, documents, and policies to promote the comprehensive utilization of coal gangue, providing strong support in finance and taxation, and continuously improving the comprehensive utilization rate of solid waste. In 2019, the comprehensive utilization rate of large comprehensive solid wastes will reach 55%, 5 percentage points higher than that in 2015, of which the comprehensive utilization rate of coal gangue and fly ash will reach 70% et 78% respectivement [1]. Although satisfactory results have been achieved, there is still a significant gap compared to some developed countries. According to online materials from China Building Materials Industry Planning and Research Institute and Huajing Industry Research Institute, the utilization rate of coal gangue and fly ash in Japan is very high. Taking fly ash as an example, it reached as high as 98.3% in 2011, and the added value of utilization is also high, with cement being the dominant factor, accounting for 67.13%; Civil engineering accounts for 13.58%; Building panels, lightweight aggregates, and others account for 17.59%. In 2016, the utilization rate of fly ash in Europe was 83.4%, which not only had a high utilization rate but also diversified utilization channels. By 2016, fly ash in Europe had been basically utilized, avec 40.8% being used as concrete admixtures; 17.0% replace cement in concrete; 16.4% for road materials; 5.5% for concrete blocks; 3.7% for others. In the early 1970s, Germany, France, and other countries achieved a comprehensive utilization rate of 30% pour 50% of coal gangue. In the 1960s, Japan used coal gangue sintered lightweight aggregates for the construction field, reducing building weight by 20%, rendant sa contribution aux murs légers particulièrement importante.

2.3 Application dans l'industrie des matériaux muraux

Dans les pays développés, dès le début des années 1960, Germany, France, et le Japon a largement utilisé la gangue de charbon et les cendres volantes pour produire divers matériaux de mur, qui ont été largement utilisés dans les projets de construction. La Chine a introduit la technologie de la gangue de charbon et des briques à combustion interne de cendres volantes dans les années 1960, dans le but d'économiser du charbon et de réduire les coûts. Dans les années 1970, la gangue de charbon et les cendres volantes sont devenues les principaux combustibles internes, se transformant progressivement en gangue de charbon et en cendres volantes comme principale source de combustion interne, complété par du charbon externe. En cours de développement de briques à combustion interne de gangue de charbon et de cendres volantes, le ministère des matières premières organise diverses formes de classes d'études et d'activités de promotion et d'échange de réalisations sur la production de divers matériaux de mur à l'aide de gangue de charbon et de cendres volantes. Avant 1980, les entreprises de briques et de tuiles de matériaux de mur appartenaient principalement à l'État, and many state-owned brick factories created many technical experience and practical achievements in coal gangue and fly ash internal combustion bricks. Taking the utilization of coal gangue as an example, a production line with a design capacity of 15 million pieces of coal gangue bricks was built in the original Neijiang Machine made Brick and Tile Factory in 1973.

If we say that coal gangue and fly ash were only used as internal combustion materials around the 1960s, and the amount of utilization was very small, then it was only after the 1970s that a large number of coal gangue and fly ash were used as the main raw materials to produce wall products. The products were mainly solid bricks, but also porous bricks, Concrete masonry unit and hollow blocks. The earliest successful trial production of coal gangue bricks was carried out by Sichuan Yongrong Mining Bureau, and the Shigu Coal Mine in Gaoming City also built an annual production line of 15 million coal gangue bricks in the 1970s. In the 1980s, les produits de matériaux de gangue de charbon et de cendres volantes se sont développés rapidement. Avec l'amélioration continue de la gangue de charbon et de la technologie des matériaux de paroi frittés de cendres volantes et l'expansion de l'échelle de production, le niveau d'équipement semble ne pas pouvoir suivre les besoins de développement des produits en gangue de charbon et en briques de cendres volantes. A la fin des années 1980, La Chine a entamé une phase d'introduction, innovation, et développement ultérieur. Shanxi, Shandong, Ningxia, Anhui, Heilongjiang and other provinces have introduced equipment for producing wall materials using coal gangue and fly ash from the United States, Germany, Italy, and others. With the approval of the former State Economic and Trade Commission [2], a production line with an annual output of 60 million coal gangue Concrete masonry unit was introduced in Shuangyashan, Heilongjiang Province. Technically, it is required to make bricks from all coal gangue, and the assembled tunnel kiln is fired by ultra internal combustion. The product quality is Concrete masonry unit and porous load-bearing clean water wall bricks, and truly achieve “no soil for brick making, no coal for brick burning”. The product is of high grade. This introduction project has received strong support and high recognition from relevant central ministries and commissions, causing strong reactions within the industry. The coal gangue production line adopts a one-time sintering process and a super internal combustion coal gangue sintered brick process. Its equipment, Kaizhuang tunnel kiln and super internal combustion roasting technology have been fully digested and innovated, and its research and development achievements have won the second prize of the National Science and Technology Progress Award. It has been widely promoted and applied in China, making important contributions to the comprehensive utilization of coal gangue in the wall material industry in China. Provinces and cities with coal gangue have basically successfully built production lines, augmentant rapidement la production annuelle de briques de matériaux de mur de gangue de charbon dans tout le pays à plus de 200 milliards de briques standards. The annual output of sintered products in China’s wall material industry is more than 810 billion pieces [3], of which the bulk solid wastes such as coal gangue and fly ash, environmental protection and other new wall material products have developed rapidly in recent years, with an annual output of nearly 600 billion pieces, becoming the largest solid waste comprehensive utilization industry in China. The annual utilization of solid waste has exceeded 135 million tons, and the annual energy saving has reached 32 million tons of standard coal. Le principal combustible utilisé pour les produits de briques et de tuiles frittées est constitué de déchets solides en vrac tels que la gangue de charbon et les cendres volantes.. Il y a très peu d’utilisation externe d’énergies fossiles telles que le charbon et le gaz naturel. Les déchets énergétiques tels que la gangue de charbon et les cendres volantes représentent plus de 80%, alors que le charbon et le gaz naturel ne représentent que moins de 80%. Cela a contribué à l'utilisation globale des déchets solides, aux économies d'énergie et à la réduction des émissions de carbone dans l'ensemble de l'industrie des matériaux de construction..