Effect of self-assembly gel crosslinking property and the wetting characteristics of coal under different acid solution

Porosity and Fracture Changes of Bituminous Coal under Action of Dry–Wet Cycles in Acid Environment

“…Zhang tested the bituminous coal after hydrochloric acid and nitric acid treatment by using the X-ray diffraction (XRD) technique, and the results showed that hydrochloric acid could remove sulfate and nitric acid could remove pyrite. Xie − studied the effect of surfactant synergistic compound acidification on the chemical structure and wetting characteristics of coal and also investigated the mechanism of the influence of chemical structure on the wetting characteristics of coal. Han studied the changes of surfactants and ionic liquids on the physicochemical properties of acidified coal.…”

Research on how acidification affects the coal's microscopic pore structure in the Guizhou mining region

“…As an unconventional energy source, CBM is a natural and clean energy source that can be used as a fuel and a chemical raw material and is of great significance to the global energy development strategy 2–4 . How to improve the permeability of coal beds is a key factor affecting CBM mining, in which acidification technology has been applied in engineering practice and has clear development prospects 5–8 …”

“…Focusing on three typical inorganic acids, HF, HCl, and HNO 3 , the pore, microcrystalline and combustion properties of raw and acidified coal were analyzed using X‐ray diffraction (XRD) and simultaneous thermal analysis (STA), and the fractal dimensionality theory, microcrystalline structure analysis theory, and thermal evaluation kinetic theory were utilized to analyze the pore, microcrystalline, and combustion properties of raw and acidified coal, respectively, and the results showed that the HF has the best enlarging effect on the volume of the pores and the pore size of the coal, followed by HNO 3 , and that inorganic acids can cause the layer spacing of the bituminous microcrystalline structure to collapse, and promote the transverse splicing and vertical stacking of the aryl structure, thus increasing the extent of the condensation of the aryl rings in the bituminous coal, as well as the degree of coal deterioration 21 . The addition of sodium dodecyl sulfate to the acidification treatment intensified the substitution reaction of the benzene ring structure in coal, according to research employing FTIR on the impact of acidification on the chemical composition of coal 6,19 . The effect of acid‐thermal coupling on the destruction of coal pores and cracks was studied.…”

Study on the Response Law of Coal Pore Structure and Permeability Affected by Acidification Time

“…The coal seam gas (coalbed methane) emitted in the process of coal mining will not only threaten the safety of mine production and cause casualties but also destroy the ozone layer and cause serious greenhouse emissions. − Studies show that methane can cause damage to the ozone layer 7 times as much as carbon dioxide, and the induced greenhouse effect is 20 times as much as that of carbon dioxide at the same quality. − In recent years, with the rapid development of the national economy, the depth and intensity of coal mining have been increasing, and the mine gas emission is also increasing rapidly. − At the same time, coalbed methane is also a kind of clean energy, and the proven reserves in China are as high as 12 trillion m 3 , which has great potential for development. − Coalbed methane development and effective gas extraction can not only reduce gas emissions and gas accidents but also improve the atmospheric environment . Due to the low permeability of most coal seams in our country, the effective extraction range of coal seams is small, the gas concentration is low, the extraction is difficult, and the treatment effect is not ideal. − In order to solve this engineering problem, a variety of measures have been taken to increase the permeability of coal seams, such as hydraulic punching, hydraulic fracturing, deep-hole presplitting carbon dioxide phase transformation cracking, etc. − In addition, coal surface modification technology has also been widely used in coal seam infiltration. − After acid infiltration, this technology changes the pore structure and surface properties of coal, so that the porosity and permeability of the coal seam are increased and the permeability of the coal seam is greatly improved. A multicomponent acid solution treatment of different ranks of coal was carried out by Zepeng et al It was found that the coal sample had a good antireflective effect after acidizing treatment, and the best formula of the acid solution was selected.…”

“… 24 − 28 In addition, coal surface modification technology has also been widely used in coal seam infiltration. 29 − 32 After acid infiltration, this technology changes the pore structure and surface properties of coal, so that the porosity and permeability of the coal seam are increased and the permeability of the coal seam is greatly improved. A multicomponent acid solution treatment of different ranks of coal was carried out by Zepeng et al 30 It was found that the coal sample had a good antireflective effect after acidizing treatment, and the best formula of the acid solution was selected.…”