Energy storage via storing flood in abandoned mines and low temperature heat energy utilization from mine water

The utilization of underground space in abandoned mines is a key direction supported by the coal industry. By combining underground space utilization, flood storage, and heat supply in winter, this paper proposes a comprehensive utilization model of flood storage and heat extraction in the abandoned mine, based on three technologies: ground flood diversion, underground flood storage and heat pump. This paper addresses the concept, key technologies and scientific issues of the model. The distribution of abandoned mines in China and its relationship with precipitation distribution were analyzed. The potential for flood and energy storage in abandoned mine was also studied. Results showed that 13 provinces, including Anhui, Henan, and Shandong province, can utilize approximately 60 million cubic meters of underground space and store nearly 6 volumes of West Lake water, making it suitable for engineering demonstration of flood storage and heat extraction in abandoned mines. Among them, five abandoned mines in Huainan mining area can utilize approximately 300 000 cubic meters of underground space, with energy storage capacity of up to 94 500 GJ that can meet the heating demand of 210 000 square meters. Taking Qishan Mine as an example, a scheme was designed based on ground flood diversion and storage, underground water storage, and mine water extraction and utilization. According to preliminary calculations, the heating power of Qishan Mine can reach 6 835 kW which can provide heating for 136 700 square meters of buildings, reduce carbon dioxide emissions by about 5 330 tons, and save 3.507 5 million yuan. This demonstrates the feasibility of flood and energy storage in abandoned underground space. Research showed that the comprehensive utilization model of flood storage, energy storage, and heat extraction in abandoned mines can not only effectively utilize the underground space of abandoned mines but also alleviate local flood disasters during the flood season. It can develop low-grade clean energy in mine water and has certain significance in improving the added value of underground space utilization in abandoned mines and promoting the utilization of underground space in abandoned mines

Study on Preparation and Performance of CO₂ Foamed Concrete for Heat Insulation and Carbon Storage

Environmental problems caused by large amounts of CO2 generated by coal–electricity integration bases have raised concerns. To solve these problems, this study develops a CO2 foam concrete (CFC) material with both heat insulation and carbon fixation characteristics to realize CO2 in situ storage and utilization. In this study, a Portland-cement-based CO2 foam concrete (PC-CFC) with good thermal insulation performance and carbon fixation ability is prepared using carbonation pretreatment cement and a physical foaming method. The effects of CO2 on the compressive strength, thermal insulation, and carbon fixation properties of PC-CFC are studied. The internal relationship between the compressive strength, thermal insulation, and carbon fixation performance of PC-CFC is analyzed, and the feasibility of PC-CFC as a filling material to realize the in situ mineralization and storage of CO2 in the coal–electricity integration base is discussed. The experimental results show that the compressive strength of PC-CFC is significantly improved by CO2 curing. However, CO2 in the PC-CFC pores may weaken the strength of the pore structure, and the compressive strength decreases by 3.62% for each 1% increase in PC-CFC porosity. Using CO2 as a foaming gas and the physical foaming method to prepare CFC can achieve improved thermal insulation performance. The thermal conductivity of PC-CFC is 0.0512–0.0905 W/(m·K). In addition, the compressive strength of PC-CFC increases by 19.08% when the thermal conductivity of PC-CFC increases by 1%. On the premise of meeting the thermal insulation requirements, PC-CFC can achieve improved compressive strength. The carbon sequestration rate of the PC-CFC skeleton is 6.1–8.57%, and the carbon storage capacity of PC-CFC pores is 1.36–2.60 kg/ton, which has obvious carbon sequestration potential; however, the preparation process and parameters of PC-CFC still require further improvement. The research results show that PC-CFC has great potential for engineering applications and is of great significance for realizing carbon reduction at the coal–electricity integration base

Effect of carbonation and foam content on CO2 foamed concrete behavior

Coal and electricity integration plays an important role in ensuring national energy security, but it still faces the challenge of carbon emission reduction. The development of in-situ CO2 sequestration and utilization technology for pithead power plants is an effective way to achieve low-carbon and efficient utilization of coal power. The preparation of foam concrete for mining using CO2 is a type of carbon capture, utilization, and storage technology featuring in-situ CO2 sequestration and utilization in pithead power plants and mine filling and sequestration. The purpose of this study is to evaluate the basic performance and carbon sequestration potential of Portland cement-based CO2 foam concrete (PC-CFC) as a mining material. In this study, PC-CFC was prepared through physical foaming and the carbonation pretreatment cement process. The influence of carbonation pretreatment time and CO2 foam content on density, strength, and carbon sequestration of PC-CFC was investigated. The experimental results showed that carbonation pretreatment could enhance the stability of CO2 foam in Portland cement and improve the CO2 foaming performance. With the extension of carbonation pretreatment time, the extend of dry density reduction decreases from 16.6% to 0.8%. A 60 min–90 min of carbonation pretreatment can achieve the best treatment performance. Carbonation pretreatment and CO2 foam can promote the degree of cement hydration, optimize the PC-CFC pore structure, and improve the compressive strength of PC-CFC. However, the PC-CFC material strength owing to the extended carbonation treatment time, which leads to well-developed vesicle distribution, has an overall decreasing trend. In addition, the 7 day (d) compressive strength of PC-CFC can reach more than 60% of the 28 d compressive strength, which has evident early strength characteristics. Extending the carbonation pretreatment time and CO2 foam content increased the PC-CFC carbon sequestration that ranged from 61.0 kg/ton to 85.7 kg/ton. The dry density of the PC-CFC material was significantly and positively correlated to the 28 d compressive strength and negatively correlated to the amount of carbon sequestration. In the case in which the best carbon sequestration effects is achieved, a single filling of the working face end can store ∼3929.31 kg of CO2; in the most economical condition, it can store ∼3642.79 kg of CO2. The conducted research provides new ideas for the low-carbon and green development of coal and electricity integration