Mineralization technology of solid waste carbon dioxide: carbon neutralization code of "waste" into gold

Origin: When solid waste meets carbon emission reduction

The birth of solid waste CO₂ mineralization technology stems from the collaborative solution to two major environmental problems-industrial solid waste accumulation and greenhouse gas emission. Since Seifritz first proposed CO₂ mineralization storage in 1990, it has been considered as a large-scale CO₂ storage technology with potential and application prospects. At the beginning of the 21st century, scientists found that industrial solid wastes (such as coal gangue, steel slag and fly ash) rich in metal elements such as calcium and magnesium can react chemically with CO₂ to generate stable carbonate minerals, thus realizing the double benefits of "fixing carbon with wastes". This discovery has quickly become a global research hotspot, especially under the background of China's "double carbon" strategy, this technology is regarded as the key path to realize circular economy and carbon emission reduction.

Development: from laboratory to 10 thousand ton production line

From the thermodynamic point of view, the standard Gibbs free energy of carbonate produced by mineralization reaction is 0~180 kJ/mol lower than that of CO₂. Mineralization reaction is a process from high energy state to low energy state, and the carbonate produced is relatively stable and will not decompose even after a long time. The early research of CO₂ mineralization technology focused on the optimization of chemical reaction conditions, such as accelerating mineralization through high-activity solid waste and high-temperature and high-pressure environment, but energy consumption and cost restricted commercialization. After 2015, mineralization technology ushered in three major leaps: first, raw materials expanded from single solid waste to multi-source solid waste such as steel slag, carbide slag and phosphogypsum; At the same time, low-carbon technologies such as microbial catalysis and photothermal driving greatly reduce the energy consumption in the mineralization process; In addition, the mineralized products have changed from "supporting role" in landfills to high-value products such as building materials and soil remediation agents, and gradually formed an integrated process flow of solid waste pretreatment, —CO₂ capture, mineralization reaction and product utilization, which expanded the mineralized products to the fields of building materials, agriculture and chemical industry.

For example, a state-owned enterprise in Anhui invested in the construction of the first 10,000-ton CO₂ mineralization project in the domestic coal chemical industry to prepare all solid wastes and negative carbon building materials, realizing the cooperative disposal of high-mineralized active solid wastes (carbide slag, steel slag, phosphorus slag, etc.) and low-mineralized active solid wastes (fly ash, gasification slag, etc.), and carrying out mineralization reaction with CO₂ flue gas without external heat source to prepare mineralized building materials products with high strength, high carbon fixation rate and negative carbon emission, with an average carbon fixation rate of 15.

Research hotspot and direction

At present, the research on solid waste mineralization technology mainly focuses on the following directions. Firstly, through pretreatment technologies such as nano-pulverization and microbial mineralization, the reaction rate of metal ions such as calcium and magnesium in solid waste is accelerated to solve the problem of low mineralization efficiency of raw materials; Secondly, by mixing multi-source solid waste such as steel slag and fly ash, the proportion of components is optimized, and the reaction efficiency is significantly improved; At the same time, develop a solar-driven mineralization system to realize a low-energy carbon fixation system using primary energy; In addition, the research focuses on promoting the system integration of carbon capture, transportation and mineralization devices to form a zero-carbon industrial park with "solid waste + CO = resource products".

Research Difficulties and Solutions

The scale of technology faces three challenges: first, the contradiction between high investment in mineralizing equipment and upside-down product profits, and the carbon emission reduction of enterprises needs to be converted into comprehensive income per ton of 200 yuan through the policy combination of "carbon tax return+green credit"; Second, the treatment capacity of the existing process is less than 5% of the solid waste stock, so it is urgent to optimize the reaction parameters by using AI algorithm, and the mineralization efficiency will jump 8 times within 3 years; Third, solid waste collection, carbon source supply and product consumption are separated, and the demand of power plants, steel mills and building materials factories can be dynamically matched by relying on the "urban mineral" cloud platform, and the industrial chain can be blocked.

Future prospect: 100 billion-level green rich ore

By 2030, solid waste mineralization technology is expected to reshape the industrial ecology: on the environmental level, the country can consume nearly 100 million tons of solid waste and absorb about 20 million tons of CO₂ annually, which is equivalent to creating a carbon sink scale of Saihanba Forest Farm; On the economic level, new industries such as mineralized building materials and carbon sink trading have been promoted, and the trillion-dollar market has been instigated to activate the vitality of circular economy; On the social level, traditional industries such as cement plants and steel plants have been upgraded to "urban carbon sinks", and technology has enabled the deep integration of industrial civilization and ecological civilization to write a sustainable development plan for China.

Source： https://mp.weixin.qq.com/s/NRSxK7dDYiehkQbf1UR4mQ