Typical Chinese Coals Research Articles

Sulfur migration and distribution during pyrolysis of a typical Chinese pyrite-enriched coal

ABSTRACT Sulfur migration and distribution during pyrolysis of coal is quite complicated with the effect from different intertwined influencing factors, which requires extensive investigation. In this research, a typical Chinese pyrite-enriched coal was selected and pretreated through acid leaching combined with CrCl2 reduction. Thereby, minerals such as silicates and sulfates in the raw coal were effectively separated with the ash contents decreased from 37.74% to 0.57% while the inorganic sulfur was completely removed. Furthermore, programmed combined with isothermal pyrolysis of the selected coal and its two pretreated counterparts were conducted on the home-designed horizontal reactor to systematically ascertain the gaseous sulfur evolution. Possible sulfur formation pathways were revealed to explain the effect from the intertwined factors between the reaction temperature and the intrinsic factors as minerals distribution, different sulfur occurrences and their association with the organic matrix of coal. Finally, quantitative evaluation of the temperature effect on the sulfuric gases distribution and their yields was conducted with the total fraction of all the gaseous sulfur much decreasing from 5.6% to below 2.0% for the deashed and depyrited coal. Overall, through such a systematic investigation on the sulfur evolution from a typical pyrite-rich coal, comprehensive insights were obtained for future efficient sulfur control.

Research on Oxy-Fuel Combustion Characteristics of Two Typical Chinese Coals

Oxy–fuel (O2/CO2) combustion technology shows great potential for carbon reduction. However, difference in the combustion atmosphere would affect coal combustion characteristics and pollutant emissions. In order to explore oxy–fuel combustion characteristics, two typical Chinese coals, sub–bituminous and lean coal, were utilized. Based on thermogravimetry and pilot–scale test, the ignition and burnout characteristics under oxy–fuel and air combustion atmosphere were investigated. Besides, the NOx emission characteristics were also investigated on the pilot–scale test. Through experimental results, these two kinds of coal showed different combustion characteristics, mainly due to differences in coal quality. Compared with air combustion, oxy–fuel combustion affected the coal combustion process. Firstly, the ignition temperature of sub–bituminous and lean coal decreased from 418 and 477 °C to 405 and 415 °C, respectively; the burnout temperature also decreased from 855 and 985 °C to 808 and 838 °C, respectively. Then, coal combustion performance was evaluated by comprehensive combustion characteristics (S); with an increase in S from, respectively, 3.659 and 2.013 to 4.826 and 3.545 × 10−8(min−2 × K−3), the combustion performance significantly improved. Then, the char burnout time was advanced for 1~3 min. Similar results were obtained on the pilot–scale test. The ignition temperatures decreased from 505 and 552 to 490 and 512 °C, respectively. Moreover, the char burnout rate increased by 0.5~5% and 2~11%, respectively. Lastly, the NOx concentration in flue gas was 2.2~2.6 and 2.0~2.3 times higher for the two kinds of coal under oxy–fuel combustion.

Experimental study on the contribution of included/excluded minerals to particulate formation during coal char combustion

The contributions of included and excluded minerals to particulate matter formation are quantified in this work. By devolatilization of three typical Chinese coals, three coal chars with low (LA), moderate (MA), and high ash (HA) content (with both included and excluded minerals) were prepared, from which three float coal chars with low (LA−), moderate (MA−), and high ash (HA−) content (without excluded minerals) were separated by density differentiation method. The coal chars before and after separation were burned in a drop-tube furnace at 1600 K, the results of three float coal chars can directly reveal the contribution of included minerals, and the comparison of two kinds of chars with and without excluded minerals would reveal the excluded mineral contribution to ash distribution. The size distributions of the combustion-generated ash particle were obtained from the combination of ELPI+ and laser particle-size analyzer. The fractions of included/excluded minerals were obtained from SEM images. The results from the combustion of the float chars indicate the physical transformation of included minerals, while the results from original coal chars involve the transformation of both included and excluded minerals. Results indicate that the distribution of ash particles from included minerals for HA− char possesses a single peak, while the ash distributions of MA− and LA− char show a bi-modal shape. The excluded minerals in LA and MA chars mainly contribute to the ash emissions with sizes larger than 80 μm. The contribution from excluded minerals reach 86% to the ash particles of 205 μm for HA char, 54% for MA char and 51% for LA char. The number fractions of included minerals continuously decrease with a transformation into excluded minerals during char dynamic combustion.

Risk Evaluation Model of Coal Spontaneous Combustion Based on AEM-AHP-LSTM

Immediately and accurately assessing the risk of coal spontaneous combustion and taking targeted action are crucial steps in coal spontaneous combustion prevention and control. A new model, AEM-AHP-LSTM, was proposed to solve the weight calculation problem of multiobjective evaluation in the process of coal spontaneous combustion. Firstly, the key indicators of coal spontaneous combustion were analyzed and used as risk factors to establish an evaluation system. Next, the objective and subjective weights were calculated using AEM and AHP, respectively. The objective and subjective weights were then combined, and TOPSIS was used to calculate the score of the evaluation sample. Finally, the obtained evaluation samples were trained with the BP, RBF, and LSTM model to resolve the problem of model overdependence on historical data and achieve the auto-adapt adjustment of weight with data change. Additionally, data from 15 typical Chinese coal mines were applied to the model. The results indicate that, compared with the BP and RBF neural networks, the LSTM model has higher prediction accuracy, stronger generalization ability, and stronger practicability. The modeling and application findings show that the AEM-AHP-LSTM model was better appropriate for the risk assessment of coal spontaneous combustion. This method can potentially be further applied as reliable approach for the assessment of mine disaster risk.

Experimental evaluation of the dynamic water-blocking effect in coalbed methane reservoir

Field observations indicate that almost 59% of coalbed methane (CBM) wells in the southern Qinshui Basin showed insufficient daily gas production (∼600 m3/t); this is caused by the water-blocking effect (WBE) attributed to the invasion of fracturing fluids or the accumulation of formation water. WBE can cause serious damages to the low-permeability reservoir but has not been paid sufficient attention to in CBM studies. To enhance understanding of the dynamic WBE in the multiphase flow process, we conducted core flooding experiments on two typical Chinese bituminous coal and anthracite coal samples. During the flooding experiments, real-time nuclear magnetic resonance (NMR) measurements of the change of water signal in the core were used to calculate the gas-water relative permeability and to evaluate the dynamic WBE. The results highlight that a more pronounced WBE occurred in anthracite coal compared with bituminous coal. The gas breakthrough model can calculate the gas breakthrough time, which is a useful parameter for evaluating water blocking. The water-blocking threshold pressure gradient (TPG) was determined based on experimental data. The results reveal that the water-blocking TPGs for both samples follow a positive power-law relationship with the normalized water saturation. The water-blocking TPG is approximately an order of magnitude higher than that of the conventional gas TPG. A high water-blocking TPG value reflects stronger gas/water interference during multiphase flow, exerting a negligible impact on the gas migration through the coalbed, which should be prioritized in CBM production. The implications of this study are important for a better understanding of the interaction mechanism of gas and water transport in coal reservoirs during the gas production process.

Characterization of in-situ and cooling char from ten typical Chinese coals

Coal char has lots of functions such as combustion, gasification, adsorbent, activated carbon production and carbon materials. Most of coal chars are generated from raw coal pyrolysis at high temperature, and later cool down to room temperature before further utilizations. The additional cooling process between the two stages have great influence on char structure, performance and reactivity. Herein, we prepared in-situ char and ex-situ char with different cooling rates from ten typical Chinese coals, including anthracite, bituminous and lignite. SEM morphology, powder X-ray diffraction, elemental H/C ratio, specific surface area and active surface area of the cooling chars were characterized. Results show that carbon structure tends to be graphitized while cooling. In-situ char has the lowest carbon graphitization and thus the highest carbon defects, which provides more active surface area and carbon active sites. Char reactivity decreases in the order of raw coal > in-situ char > rapid cooling char (103–104 K/s) > medium cooling char (10–100 K/s) > slow cooling char (0.1 K/s), where char reactivity is more sensitive to cooling rate in low rank char than high rank char. The decline of reactivity during cooling is probably due to the loss of carbon active sites

Effects of pressure on the chemical looping combustion of coal with CuFe2O4 combined oxygen carrier

Chemical looping combustion (CLC) has fast developed as an attractive technology for clean utilization of coal as well as inherent CO2 separation at the low energy penalty. Increase of the system pressure has been acknowledged as one of the effective measures in CLC for sufficient conversion of coal along with affiliated benefits for CO2 sequestration, but the complex consequences as incurred should be well considered. In this research, reaction of a typical Chinese bituminous coal of high sulfur content (designated as LZ) with CuFe2O4 combined oxygen carrier (OC) within 0.1–3.0 MPa in the CO2 atmosphere was systematically investigated, with focus on the effect of the system pressure to the conversion of LZ coal, transfer of the oxygen involved in CuFe2O4, sulfur evolution and redistribution. Sequential reactions of CuFe2O4 with the volatiles emitted from pyrolysis of LZ coal and further reaction with the released gasification products and residual char were accomplished, which was beneficial to overcome the mass transfer limitation of the reducing gases evolved from LZ coal to OC under the pressurized conditions and alleviate the inhibition effect resulting from accumulation of the transferred reactive gases around the surroundings of OC. And thus, under the pressurized conditions, improved conversion of LZ coal was reached by oxidization of more intractable C-C/C-H groups to oxygen bound carbon groups. Meanwhile, deep reduction of the added CuFe2O4 occurred with deficient Fe3O4 at the lower valence being formed, which would interact with the silicon minerals present in LZ coal to form various iron silicates. Furthermore, sulfur evolution from coal was found to directionally interact with the reduced CuFe2O4 to mainly form solid Cu2S due to their high combination potential. And deeper reduction of Cu2S was instigated especially at 3.0 MPa with Cu1.8S formed, and the total solid sulfur fraction was increased with the elevated system pressure. Overall, comprehensive information on the interaction of coal of high sulfur content with CuFe2O4 under the extended pressurized conditions around 0.1–3.0 MPa was provided, which would be meaningful for the realistic pressurized CLC in the future.

Characteristics and evolution of products under moderate and high temperature coal pyrolysis in drop tube furnace

Drop tube furnace is a high-efficiency pyrolysis reactor, which is helpful for fundamental research of coal base poly-generation technology. In this paper, the characteristics of coal pyrolysis product at various temperature using drop tube furnace were investigated. A typical Chinese lignite Pingzhuang coal was used in current research, pyrolysis temperature ranged from 600 to 1000 °C with a step of 100 °C. The compositions of pyrolysis gas, coal tar and char were characterized and discussed in detail. Results showed that volatiles and moisture content decreased after pyrolysis, hydrophilic functional groups like carboxyl and hydroxyl also decreased, pyrolysis was a dehydration upgrading process for lignite. Specific surface area and total pore volume increased from 1.65 m2/g and 11.57 mm3/g in raw coal to 199.10 m2/g and 191.95 mm3/g in 1000 °C char, respectively. As for pyrolysis gas, when temperature increased, H2 and CO increased obviously, other compositions like CO2, CH4 and C2~C3 hydrocarbons decreased, consequently, the gross heating value of pyrolysis gas decreased from 22.5 MJ/m3 at 600 °C to 13.1 MJ/m3 at 1000 °C. High temperature pyrolysis had a high content of syngas (H2+CO), which can be utilized as raw material in synthetic chemical industry. There were high content of toluene in low temperature coal tar. There were more polycyclic aromatic hydrocarbons and less aliphatic chain hydrocarbons in high temperature coal tar.

Roles of moisture and cyclic loading in microstructures and their effects on mechanical properties for typical Chinese bituminous coals

This work aimed at studying the roles of moisture and cyclic loading in microstructures and their effects on mechanical properties for typical Chinese bituminous coals. Different relative moisture contents (100%, 75%, 50%, 25%, and 0%) for Shenmu coal (SM), Hongshaquan coal (HSQ), and Wucaiwan coal (WCW) were chosen to study the effects of moisture. The raw SM was then further selected to investigate the effects of cyclic loading. Images of coals surfaces and mechanical properties during simulated crushing process were recorded and combined to be analyzed. The results showed that the moisture possessed significant effects on coal mechanical properties, which strongly depended on their porosities. As for low porosity coal (SM), the adsorption of moisture can soften and lubricate the microstructures, weakening mechanical properties. While the drying process would destroy the microstructures and decease mechanical properties for high porosity coals (HSQ and WCW). Under the cyclic loading process, the cumulative effects of strain showed a step-up state and the first cyclic loading can typically cause the biggest change of microstructures and produce the largest strain under different stress levels. Finally, a normalized quantitative relationship (σr=-0.67Dr2+1.62Dr+0.07) between the relative fractal dimension and relative stress was built.

Spectral energy characteristics of radiation in oxy-coal combustion for energy utilization

In this paper, the radiative energy characteristics, especially the spectral distribution characteristics, of the oxy-fuel combustion of pulverized coal are studied from the perspective of radiative energy utilization. Based on a modified tube furnace test platform, the radiative energy flux and spectral distribution of oxy-fuel combustion for three typical Chinese coals under O2/N2 and O2/CO2 atmospheres in the temperature range of 600–1000 °C are measured online using radiative heat flux sensors. In particular, the radiative exergy and its spectral distribution characteristics are analyzed based on the second law of thermodynamics. It is found that the intensity of the radiative energy and exergy increase, as does the proportion of spectral radiation below the wavelength of 4.1 μm, with the increase of the oxygen ratio and combustion temperature under the experimental conditions. In contrast, different atmospheres are found to have little effect on the radiation characteristics. One-dimensional calculation cases of media radiation transfer constructed according to the combustion characteristics can better reveal the proportional characteristics of the spectral radiation. The results provide a reference for research on the cascade conversion and management of photo-thermal energy in fuel combustion.

Effect of coal rank, oxygen level and particle size on oxidation reactivity of typical Chinese coals

The changeable and deteriorating coal quality in air staging mode threats the safe and economic operation of the boiler. Non-isothermal TGA experiment was performed with varying heating rates (5, 10, 15 and 20 K/min) on six Chinese coals at 20 % O2 and on the lean coal with varying O2 (5%, 10 %, 20 % and 40 %). Isoconversional method is adopted to determine the activation energy (Eα) and frequency factor (Aα). Influence of particle size at varying oxygen concentration is compared between lean coal and bituminous coal at 20 K/min. The characteristic temperature (T0.1, T0.5 and T0.9) increases as the coal rank increases and oxygen level decreases. The slope of the line (characteristic temperature vs. O2) increases from 1.6 to 3.6 as the conversion increases from 0.1 to 0.9, which means the oxygen diffusion has an increasingly important role as the oxidation proceeds. As O2 decreases, the effect of particle size reduction on combustion improvement of low volatile coal is increasingly significant than that of high volatile coal. The smaller economic fineness of coal particle can be established for low volatile coal in low NOx combustion mode compared with that for high volatile coal.

A machine learning approach to improve ignition properties of high-ash Indian coals by solvent extraction and coal blending

Indian coals are of poor quality, having high ash content and lower calorific value as compared to foreign coal reserves. To circumvent the problems of high ash content and low calorific value in coal, this study endeavours to explore two methods of improving ignition characteristics of Indian coals: solvent extraction and coal blending. The thermal decomposition behaviour of four Indian coals with and without solvent extraction were investigated through a thermogravimetric analyser under non-isothermal conditions. Kinetic parameters and activation energies of the coals were determined by using Arrhenius, Coats-Redfern, Doyle-Ozawa and Friedman methods. It was found that solvent extraction of the coal reduced the activation energy by approximately 50%. Pearson correlation analysis performed on the chemical composition and ignition properties of 16 typical Chinese coals and 48 of their blends showed that moisture, volatile matter, fixed carbon, calorific value, oxygen, and carbon content of coals were the most relevant factor to ignition temperature and activation energy. Accordingly, three-layer back-propagation neural network models were trained and tested and found to be reasonably accurate. The selected neural networks were used to predict the ignition characteristics of 17 Indian coals. 16 Indian coals were then hypothetically blended with 84 coals from various other countries to form 1344 blends, whose ignition characteristics were further predicted using the trained neural network models. 220 of these 1344 blends were found to have better ignition properties than the original Indian coals. The maximum reductions observed in ignition temperature and activation energy were 79.08 K and 179.38 kJ/mol respectively.

Experimental comparison of CO2, CH4, and N2 adsorption capacity on typical Chinese coals at different temperatures

ABSTRACT Competitive adsorption of CO2/N2/CH4 on coals is important to evaluate potential application of CO2- or N2 – ECBM, which is not fully addressed in previous studies. In this paper, CH4, CO2, and N2 adsorption behaviors are experimentally compared at different reservoir temperatures (307 K, 318 K, and 333 K) and pressure up to 9 MPa. It is found that adsorption capacities all decrease with increasing temperature for CH4, CO2, and N2, while the differences in maximum adsorption capacity at different temperatures is not significant. Maximum adsorption capacity of anthracite coal is much larger than those of bituminous coals, while the maximum adsorption capacities of two selected bituminous coal are close to each other. The maximum adsorption capacity of CO2 is 1.93 mmol/g，which is significantly higher than that of CH4 and N2 with exactly 1.80 mmol/g and 1.11 mmol/g respectively. However, for a given coal sample, gas type does not affect the thermal-stimulated desorption capacities significantly.

Mechanism study of nitric oxide reduction by light gases from typical Chinese coals

Coal devolatilization plays an important role in NO formation and reduction. In this study, the coal pyrolysis experiment was performed in an entrained flow reactor to obtain the light gas release characteristics. Six typical Chinese coals with volatile content ranged from 8.8% to 38.3% were studied. The pyrolysis temperature was in the range from 600 to 1200 °C. A significant rank dependence of HCN, CO and C2H2/C2H4/C2H6 was observed and their release for high volatile coals was higher than that for low volatile coals. The HCN–N/NH3–N ratio ranged from 0.00 to 0.66 for anthracite coals and ranged from 1.63 to 3.90 for high volatile coals. Based on the experimental results, the effect of coal pyrolysis gas on NO reduction in a plug flow reactor at reducing atmosphere was kinetically calculated. The optimal excess air ratio(αopt) corresponding to the maximum NO removal efficiency decreased with an increase in reduction temperature. For the light gas from the HL coal pyrolyzed at 800 °C, the αopt decreased from 0.73 to 0.17 when the reduction temperature increased from 927 to 1327 °C. The rate of production analysis indicated that NO removal efficiency was determined by 3 competing reaction paths: NO reduction, NO formation and oxygen consumption by combustible species.

Effect of Partial Rapid Pyrolysis on Bituminous Properties: From Structure to Reactivity

In this paper, a typical Chinese bituminous coal was pyrolyzed rapidly and repeatedly in a high frequency furnace at 1000 °C, to investigate the changes of coal physicochemical structures, reactivities and their relationship. The physicochemical structure was mainly characterized by Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, pore analysis, etc. The results showed that after the rapid pyrolysis, the specific surface area was reduced significantly, the average particle size and the content of amorphous carbon structure increased first and then decreased, the content of oxygen-containing group exposed to the surface decreased and the aromaticity increased gradually. The reactivities were analyzed by thermogravimetric analysis (TGA), including slow pyrolysis (from 105 to 1000 °C) and in-situ gasification (at 850, 900, 950 and 1000 °C). For slow pyrolysis, the primary decomposition peak of pretreated samples was inhibited while the secondary peak was enhanced. For in-situ gasification,...

Heavy metal concentrations of soils near the large opencast coal mine pits in China.

Mining is a common industrial activity and significant source of soil heavy metal (HM) pollution. However, nearly all studies on the effects of mining activities on soil environmental quality have entailed field monitoring of small regions or bibliometric analyses. This study therefore investigated the pollution of surface soils surrounding 135 large opencast coal mining pits in China. A total of 1772 surface soil samples were collected, and the concentrations of eight major HMs were determined. The HM concentrations in this study were relatively lower than the published HM concentrations of coal mine soils from 50 typical Chinese coal mines. However, pollution assessments indicated that Cd, Cu, and As concentrations were concerning. Significant correlations existed between all of the HMs and mining pit area (p<0.01), as well as between the Pb and Zn concentrations and direction (p<0.05). Climate conditions had large influences on the HM concentrations. The concentrations of all studied HMs, except for Ni, were highest in Anthrosols and lowest in hydromorphic soils. The concentrations of all HMs, except for Hg, in land use types showed a descending trend of cultivated land>garden plot>grassland. Significantly negative correlations (p<0.01) between all HM concentrations and elevation were observed. Cr, Zn, and Ni were significantly and positively correlated with the slope, and no HMs, except Cr, showed significant correlations with the parcel area. This paper provides insights for the policymakers regarding soil pollution control and management strategies near coal mine pits.

Conversion of Organic Matter in Coal by Photocatalytic Oxidation with H2O2 over SFC/TiO2 in Isolated Oxygen System

Shenfu bituminous coal (SFBC), Geting coal (GTC), Shengli lignite (SLL), and Holingola coal (HLGLC) were oxidized by UV light radiation with aqueous H2O2 over SFC/TiO2 in a closed suspension system (CSS) to understand structural characteristics of 4 typical Chinese coals. Raw and oxidized coals were dried and extracted with acetone thoroughly to ensure residue extraction. Meanwhile, the extracts were analyzed using a gas chromatograph/mass spectrometer. The results show that organic matters (OMs) in coals can be converted into a large number of oxygen-containing organic compounds (OCOCs), mainly containing ketones, esters, alcohols, etc. Oxidizing species such as hydroxyls, hydroperoxyl, and alkyl radicals are excited by light irradiation and substitute for hydrogen atoms of methyls and methylenes of acenes or branched-chain alkanes in coals. Acetic acid and acetaldehyde can be formed and dissolved in aqueous solution in the oxidation reaction. The yields can be improved with the enhancement of the oxidation effect.

Time-Resolved Intermediate-Volatility and Semivolatile Organic Compound Emissions from Household Coal Combustion in Northern China.

Coal combustion in low-efficiency household stoves results in the emission of large amounts of nonmethane organic compounds (NMOCs), including intermediate-volatility compounds (IVOCs) and semivolatile organic compounds (SVOCs). This conceptual picture is reasonably well established, however, quantitative assessment of I/SVOC emissions from household stoves is rare. We used a proton-transfer-reaction time-of-flight mass spectrometer (PTR-ToF-MS) to quantify the emissions of organic gases from a typical Chinese household coal stove operated with anthracite and bituminous coals. Most NMOCs (approximately 64-88%) were dominated by hydrocarbons and emitted during the ignition and flaming phases. The ratio of oxidized hydrocarbons increased during the flaming and smoldering stages due to the elevated combustion efficiency. The average emission factors of NMOCs were 121 ± 25.7 and 3690 ± 930 mg/kg for anthracite and bituminous coals, respectively. I/SVOCs contributed to approximately 30% of the total emitted NMOC mass during bituminous coal combustion, much higher than the contribution of biomass burning (approximately 1.5%). Furthermore, I/SVOCs may contribute over 70% of the secondary organic aerosol (SOA) mass formed from gaseous organic species emitted as a result of bituminous coal combustion. This study highlights the importance of inventorying coal-originated I/SVOCs when conducting SOA formation simulation studies.

Production of benzenecarboxylic acids from two typical Chinese subbituminous coals by oxidation in aqueous sodium hypochlorite solution and insights into structural characteristics

Zhundong subbituminous coal (ZSBC) and Shenmu-Fugu subbituminous coal (SFSBC) were oxidized in aqueous sodium hypochlorite solution at 30 °C for 10 h to produce valuable benzenecarboxylic acids (BCAs) and to understand structural characteristics of the 2 typical Chinese subbituminous coals. Fourier transform infrared spectrometer, gas chromatograph/mass spectrometer, and direct analysis in real time ionization source coupled to an ion trap mass spectrometer were used to characterize the resulting products from the oxidation. The results show that the distributions of functional groups, molecular masses, and group components of the products from ZSBC and SFSBC oxidation are largely similar. Non-chlorine BCAs are the dominant carboxylic acids (CAs) from the oxidation and the total yields of BCAs from ZSBC and SFSBC oxidation are 15.6 wt% and 16.5 wt% based on organic matter in ZSBC and SFSBC, respectively, suggesting that both coals contain abundant polycyclic or condensed aromatic rings (ARs). Various BCAs, including cata-condensed aromatics, polyaryls, and peri-condensed aromatics, were generated from different aromatic precursors (APs) via the oxidation. According to the distributions of BCAs, ZSBC is rich in polyaryl moieties with Car-Car bridged linkages between the ARs, while SFSBC contains much more highly condensed ARs. O2− dissociated from NaOCl could play a crucial role in producing BCAs from the ARs in ZSBC and SFSBC. In addition, some nitrogen-containing CAs were produced and their possible APs in ZSBC and SFSBC were speculated.

Research on the sustainable development of China’s coal cities based on lock-in effect

Contradictions in various coal city aspects have become increasingly prominent, with many cities becoming locked in due to lack of overall planning and resource degradation, and sustainable development of coal cities has attracted widespread attention. However, many research challenges remain regarding breakthrough of coal city lock-in effect. This paper evaluated 43 typical Chinese coal city 2012–2016 lock-in breakthrough abilities considering economy, environment, and sustainable development capacity aspects. We then used the fixed effect model to analyze impact mechanisms for various influencing factors on lock-in breakthrough. We found there was no significant change in overall lock-in breakthrough capacity in recent years. Technological innovation and human resources played important roles in lock-in breakthrough, and higher secondary industry proportion implied poorer ability to lock in breakthroughs. Economic externality and government finance had no significantly affect. Therefore, the government should clarify coal city transformation goals, establish a typical city as a benchmark for others, accelerate alternative industry developments, increase talent introduction and personnel training, and insist that technological innovation solves urban development problems from the root.