Gas Heat Research Articles

Zero/negative carbon emission coal and biomass staged co-gasification power generation system via biomass heating

Currently, most coal utilization technologies cannot completely remove CO2, which hinders coal utilization in the context of carbon neutrality. Staged coal-steam gasification has proven to be a potential clean coal utilization method suitable for power generation. However, it cannot achieve zero or negative carbon emissions, and there is the potential to improve energy efficiency further. This study introduces biomass into staged coal gasification and proposes a novel power generation system based on coal- and biomass-staged co-gasification via biomass external combustion heating. Biomass with a lower energy level was combusted to provide heat for gasification, thus improving the energy level matching between the gasification and biomass combustion reactions. The synergistic effect of coal and biomass reduces the tar yield and improves the gasification efficiency. Furthermore, as a carbon-neutral fuel, the introduction of biomass in the staged coal-gasification process can achieve zero or negative carbon utilization of coal. The entire system was simulated using the ASPEN PLUS software, key processes were experimentally validated, and the energy efficiency and carbon emission performance were systematically studied. The results indicated that the improved gasification methods and the synergistic effect between coal and biomass significantly improved the energy performance and emission reduction characteristics. The power efficiency of the novel system was the highest at 40.03% when the biomass blending ratio of the co-gasification sub-process was 0.8, which was 5.27% and 10.46% higher than conventional integrated gasification combined cycle (IGCC) system and biomass direct-fired power plant. The carbon-specific emissions of the novel system could be reduced to −308.1 kgCO2/MWh, achieving negative carbon utilization of fossil fuels. This novel staged coal and biomass co-gasification method heating by biomass can achieve efficient and negative carbon utilization of fossil fuels.

Modeling for on-line monitoring of carbon burnout coefficient in boiler under partial load

Combustion stability of boiler deteriorates under low load, making carbon burnout coefficient decrease, further reducing boiler thermal efficiency. The online monitoring methods of carbon burnout coefficient and boiler thermal efficiency can track energy efficiency levels of boiler in real-time under low loads. It is of great practical significance to optimize and adjust combustion conditions of boilers and upgrade boiler real-time energy efficiency. Nevertheless, extremely difficult challenge for online monitoring technology of carbon burnout coefficient seriously restricts the online monitoring of boiler thermal efficiency.In this background, an innovative theoretical model between excess air coefficient and carbon burnout coefficient is derived according to incomplete combustion equation inside furnace. Calculation method of excess air coefficient is proposed with a brand new perspective on energy balance of economizer. Subsequently, on-line monitoring model of carbon burnout coefficient and boiler thermal efficiency is constructed and verified.The online monitoring results of a 600 MW unit indicate, lower carbon burnout coefficient magnifies the degree of virtual height of calculation results and calculation error from traditional methods of national standard for calculating excess air coefficient. This operating mode results in a significant shortage of actual air flow into boiler under partial load.Carbon burnout coefficient, showing an upward trend with unit load increasing, is as high as 0.99 with unit load of 489 MW. As unit load decreases to 161 MW, carbon burnout coefficient decreases to 0.80. Additionally, combustion conditions fluctuation is greatly influenced by changing in coal quality. Under partial load, volatility in carbon burnout coefficient increases with electrical load below 300 MW. Combustion stability and combustion efficiency of boiler under low load significantly decrease. The variation in exhaust flue gas heat loss of boiler with unit load changes is relatively small due to opposite effect by exhaust gas temperature and excess air coefficient. Actually, changing trends and fluctuation degree of boiler thermal efficiency are mainly influenced by carbon burnout coefficient with a variation in load. Overall, boiler thermal efficiency, affected by heat loss of incomplete solid on combustion, fluctuates greatly at low loads. The implementation of online monitoring for carbon burnout coefficient provides a quantitative basis for improving boiler energy efficiency under low load conditions.

Gas production from hydrates by CH4-CO2 replacement: Effect of N2 and intermittent heating

Extraction of CH4 gas from Natural Gas Hydrates (NGHs) while storing CO2 by CH4-CO2 replacement method is a promising technique for achieving CO2 emission reduction and CH4 production. However, improving the kinetics and enhancing the replacement efficiency is the fundamental issue for efficient CH4 production and CO2 safe sequestration, which have become the bottlenecks in NGH extraction. In this work, the CO2 replacement characteristics and kinetics process were further elucidated. The effects of small molecule gas (N2) and intermittent heating on the CO2 replacement were quantitatively investigated. And the enhancement mechanism of N2 and intermittent heating on CO2 replacement were deeply analyzed. The results show that as the proportion of N2 increases, the CH4 recovery rate gradually increases, but the CO2 sequestration rate exhibits a pattern of initial increase followed by a decrease. In addition, the intermittent application of heat has been shown to effectively enhance the replacement performance of pure CO2 in porous media. A thicker quasi-liquid layer forms when the temperature of hydrate reservoir approaches the freezing point, making it easier for CO2 gas to form hydrates. Additionally, when intermittent heating is combined with CO2 + N2 replacement, it results in a more significant promotion of CH4 recovery.

Low-Carbon Economic Dispatch of an Integrated Electricity–Gas–Heat Energy System with Carbon Capture System and Organic Rankine Cycle

Low-Carbon Economic Dispatch of an Integrated Electricity–Gas–Heat Energy System with Carbon Capture System and Organic Rankine Cycle

Carbon nanotube microbeads for enhanced gas heating in a fluidized bed solar air collector

A novel approach utilizing vertically-aligned carbon nanotube (VACNT) as solar heat absorbers is proposed for efficient gas heating in a concentrated fluidized bed solar air collector (FBSAC). The VACNT powder was fabricated into CNT beads suitable for fluidized bed applications through macronization and densification. The CNT bead showed an increase in size and a 6.8 times increase in apparent density. The increase in sphericity and a significant decrease in the repose angle indicated improved particle fluidity. The prepared CNT beads demonstrated an absorptivity similar to VACNT, along with increased thermal conductivity and specific heat capacity, indicating superior thermophysical properties compared to conventional CNTs. Moreover, the reduced electrostatic charge generation minimizes the issue of particle attachment on the transmission window. The heat absorption characteristics of air in FBSAC (50 mm i.d. × 150 mm height) with CNT microbeads were determined. The FBSAC achieved a maximum gas temperature of approximately 150 °C. The CNT bead achieved a higher temperature difference of the gas per irradiance and a more comprehensive operating range of gas velocities up to 0.16 m/s than VACNT. The FBSAC with CNT beads exhibited a maximum thermal efficiency of 30.3 % and higher efficiency of 8–21 % than CNT powders at gas velocity of 0.11 m/s. A correlation was proposed to predict the thermal efficiencies of the FBSACs with different particles from dimensionless numbers considering particles dynamics and thermophysical properties.

Performance investigation and mass transfer enhancement of a novel cone-type solar seawater still

There are some disadvantages in the operating process of the basin solar seawater still (BSSS), such as long mass transfer distance, large heat indolence, huge floor space, and poor bearing pressure ability. A novel cone-type solar seawater still (CTSSS) is presented to overcome the weaknesses of the BSSS in this study. The CTSSS has the characteristics of seawater liquid film evaporation, short mass transfer distance, the condensation sleeve is parallel to and above the evaporation sleeve, and the condensation area is larger than the evaporation area. In order to clarify the performance of the CTSSS, the influence mechanism of feed seawater mass flow rate, heating power and heating temperature on the fresh water yield of the CTSSS was analyzed, the method of enhancing the mass transfer of the binary mixed gas in the CTSSS was explored, and the law of heat and mass transfer of the binary mixed gas in the annular enclosed small space was investigated. The results indicated that the maximum fresh water yield of the CTSSS is 62.7 g/20 min at the feed seawater mass flow rate of 400 g/h when the input power is 200 W, which is 4.5% higher than that when the feed seawater mass flow rate is 300 g/h. The performance ratio (PR) of the CTSSS is increased as the heating power, the PR of the CTSSS is 0.65 when 180 W heating power is employed. The steady state fresh water yield of the CTSSS with mirror condensation sleeve at 85°C is 84.6 g/20 min, which is 12.1% higher than that with non-mirror condensation sleeve Compared with the CTSSS with non-mirror condensation sleeve, the value of proportions of radiative heat transfer in the total heat transfer of the CTSSS with mirror condensation sleeve decreased by 6.6%, and the value of proportions of evaporative heat transfer increased by 6.4%. This study would provide a reference for small-scale decentralized application of solar desalination in remote areas.

Freeze range of a condensing gas propagating in a liquid helium-cooled tube

Understanding air propagation and condensation following a catastrophic vacuum break in particle accelerator beamlines cooled by liquid helium is crucial for maintaining the operational safety of these facilities. Previous experimental investigations on nitrogen gas propagation in both normal liquid helium (He I) and superfluid helium (He II) cooled copper tubes unveiled a nearly exponential deceleration of the gas propagation. A comprehensive theoretical model incorporating gas dynamics, heat transfer, and condensation mechanisms has been developed, which effectively reproduces various key experimental observations. An intriguing phenomenon uncovered in our model simulation is that the gas propagation appears to nearly stop beyond a certain distance from the location where condensation starts. We refer to this distance as the freeze range. In this paper, we present our systematic study of the freeze range at various inlet mass fluxes and tube diameters. We show that the results can be well described by a simple correlation. The underlying physical mechanism that supports this useful correlation is explained. Knowing the freeze range may allow accelerator engineers to develop protocols for controlling frost-layer contamination in the beamline tubes, which is of great practical importance.

Molecular simulation of the adsorption and diffusion properties of CH4 and CO2 in the microporous system of coal

Micropores are the main adsorption sites for gases in coal. The research of the adsorption and diffusion pattern of gases in micropores is important for CO2-ECBM engineering and other measures to improve production. In this study, a multiscale microporous system with intramolecular pores, intermolecular pores, and slit pores is proposed. Adsorption and diffusion characteristics of CH4 and CO2 in different microporous systems were investigated. The results show that the adsorption of different microporous systems is basically consistent at low pressures (<2 MPa). Upon further increase in pressure, adsorption increases with increasing slit pore size. Gas molecules in coal are preferentially adsorbed in the intramolecular and intermolecular pores, and gas molecules in the slit pores are preferentially adsorbed in the slit pore walls. The increase in gas pressure and slit pore size decreases the proportion of gases adsorbed in the intramolecular and intermolecular pores and also increases the proportion adsorbed in the slit pores. Increase in size of the slit pores and decrease in adsorption will result in an increase in self-diffusion coefficients of gases. The results of self-diffusion coefficients of pores with different scales indicate that slit pores have the largest self-diffusion coefficients, followed by the intermolecular pores, and the smallest for the intramolecular pores. The isosteric heat of gases tends to decrease and then increase with increasing adsorption. The increase of slit pore size will decrease interaction energy. This study gives a reference for adsorption and diffusion mechanisms of gases in microporous systems, as well as a basis for gas injection displacement studies.

Biochar gasification: Insights from pyrolysis atmospheres and gasification heating rates

Gasification is a promising technology for the synthesis of syngas and hydrogen, with char reactivity being a pivotal factor in the design of industrial gasifiers. Despite extensive studies on the gasification characteristics of biochar, the influence of the pyrolysis atmospheres on the evolution of biochar pore structure and its reactivity in gasification remains poorly understood. This study aims to bridge this gap by comprehensively investigating the effects of char preparation atmospheres (i.e., CO2, H2O, and N2) on ensuring gasification reactivities at varied heating rates. Biochars were synthesized in a horizontal tube furnace at 700 °C with a low heating rate (10 °C min−1) under three different atmospheres: N2, CO2, and H2O. Subsequent gasification reactivities were investigated using i) a thermogravimetric analyzer (TGA) at a low heating rate (10 °C min−1) and ii) a wire mesh reactor (WMR) at a high heating rate (1000 °C s−1), both under CO2 atmosphere at 950 °C. The results showed that the presence of an active atmosphere (CO2 and H2O) during pyrolysis significantly impacts the biochar’s aromaticity, crystalline structure, and surface morphology. The functional group concentration and surface area trends indicated that CO2 and H2O atmospheres during pyrolysis enhance biochar reactivity compared to the N2 atmosphere, with the highest reactivity observed for biochars produced under H2O. Furthermore, biochar gasification reactivity was markedly higher using the WMR compared to TGA, underscoring the pronounced effects of heating rate on gasification behavior. The high heating rate in WMR preserved the biochar’s porous and amorphous structure, whereas the TGA gasification encountered diffusional limitations and thermal annealing effects. These insights underscore the need to consider pyrolysis atmosphere and heating rate in gasification studies, offering a more comprehensive understanding of biochar’s behavior under practical gasification conditions.

ДОСЛІДЖЕННЯ ВИКОРИСТАННЯ АЛЬТЕРНАТИВНИХ ВИДІВ ПАЛИВА НА ПОЛТАВЩИНІ

The possibilities of using energy-resource solid household waste, agricultural waste, logging waste from forestry enter-prises, green waste from landscaping and growing energy crops as alternative renewable fuels to meet the goals of small-scale heat and power generation in Poltava Oblast are investigated. To study this issue, the specialists from the Departments of Applied Ecology and Nature Management and Heat and Gas Supply, Ventilation and Heat Power En-gineering of National University "Yuri Kondratyuk Poltava Polytechnic" were invited to join the project and a new specialization "Renewable Heat and Power Engineering, Alternative Fuels and Environmental Protection" was opened in the specialty 183 "Environmental Protection Technologies". The problem was included in the strategic development plan of Poltava region and included in the development of the Action Plan for Sustainable Energy Development and Climate of Poltava City Territorial Community until 2030 in accordance with the European initiative "Covenant of Mayors for Climate and Energy". The assessment of the bioenergy potential may become a significant environmental and economic basis for improving the regional bioenergy sector in Poltava Oblast in the future. A complex of methods of system analysis and the method of data analysis has been applied to achieve the goal of the research. An analysis of modern international literary sources, an analysis of the morphological composition of municipal and green waste, and an analysis of the energy potential of plant biomass were reviewed. As a result of research, the scientific and applied task of using local energy resources at the level of each individual community of the Poltava region, taking into account ecological, economic and social development, has been formulated and substantiated. Ref. 10, figure. Keywords: energy security, environmental security, alternative fuels, renewable energy sources, energy crops, solid household waste, small-scale energy, environmental impact.

Gas heating by inductively coupled low-pressure chlorine process plasmas

The mechanism of gas heating in low-pressure inductively coupled chlorine plasma is analyzed using a self-consistent two-dimensional axisymmetric fluid plasma model that is coupled with the compressible Navier–Stokes equations. For gas pressures of 10 and 20 mTorr and the discharge power in the range 0.1–1.3 kW, the main reactions contributing to gas heating were the ion–ion recombination reactions and the quenching of electronically excited chlorine atoms. At the same time, the energy released by the electron impact dissociation reaction of molecular chlorine is negligible due to its high degree of dissociation within the plasma bulk. The comparison between the results of our simulations and the fitting equation proposed in the literature show qualitative agreement, although there is significant quantitative discrepancy.

Benefit allocation of electricity–gas–heat–hydrogen integrated energy system based on Shapley value

Abstract The integrated energy system is an important development direction for achieving energy transformation in the context of the low-carbon development era, and an integrated energy system that uses renewable energy can reduce carbon emissions and improve energy utilization efficiency. The electric power network and the natural gas network are important transmission carriers in the energy field, so the coupling relationship between them has been of wide concern. This paper establishes an integrated energy system considering electricity, gas, heat and hydrogen loads; takes each subject in the integrated energy system as the research object; analyses the economic returns of each subject under different operation modes; applies the Shapley value method for benefit allocation; and quantifies the contribution value of the subject to the alliance through different influencing factors to revise the benefit allocation value. Compared with the independent mode, the overall benefits of the integrated energy system increase in the cooperative mode and the benefits of all subjects increase. Due to the different characteristics of different subjects in terms of environmental benefits, collaborative innovation and risk sharing, the benefit allocation is reduced for new-energy subjects and increased for power-to-gas subjects and combined heat and power generation units after revising the benefit allocation, to improve the matching degree between the contribution level and the benefit allocation under the premise of increased profit for each subject. The cooperative mode effectively enhances the economic benefits of the system as a whole and individually, and provides a useful reference for the allocation of benefits of integrated energy systems. The analysis shows that the revised benefit distribution under the cooperative model increases by 3.86%, 4.08% and 3.13% for power-to-gas subjects, combined heat and power generation units, and new-energy units, respectively, compared with the independent function model.

On abnormal noise generated from steam gas heater

When a steam gas heater set up in a town was operated, an abnormal noise with a sound pressure level (SPL) of 120 dB was generated at 32% of the rated flow rate. In order to solve this problem, We conducted a field survey to investigate the relationship between the operating conditions and the noise. First, I identified the source of noise and next, the noise level and the mode of sound pressure level (SPL) in a duct were measured and the FFT analysis was carried out to determine the dominant frequency. The results revealed that the abnormal noise was not a mere resonance but rather a self-sustained tone due to the interference of the vortex and the sound field. Furthermore, we measured the SPL outside the gas heater duct and found that the SPL was highest at the center of the gas heater duct. Typically, the first pressure mode should be minimum at the center and maximum at both ends, but the reason for this deviation was clarified in this paper. To address the issue, multiple baffle plates were inserted in a tube array and as a result, the abnormal noise completely disappeared. It was also found that the baffle plate should be inserted at the position where the particle velocity exceeds half of the maximum value.

HI decomposition over the HI-100 test apparatus at a hydrogen production rate over 100 L/h

Studies on the iodine-sulfur (IS) thermochemical cycle for hydrogen production has been carried out since about 2005 by the Institute of Nuclear and New Energy Technology, Tsinghua University, China. The HI decomposition occupies the important position of hydrogen generation in the IS cycle. In this paper, the HI-100 test apparatus with a H2 production rate of 100 L/h was constructed and the HI decomposition was tested. First, the process and components for HI decomposition were designed. Then, the key components, including the feed tank, evaporator, gas heater, adiabatic reactor, condenser, and gas-liquid separator were made of industrial materials. After building this apparatus, the sealing test, heating water test, and HI decomposition have been conducted. The stable hydrogen production operation of more than 100 L/h had been achieved for 5 h, the maximum hydrogen production reached approximately 130 L/h, and the hydroiodic acid decomposition rate maintained about 22 %. The test results provide the design and experimental guidance for further amplification of HI decomposition for hydrogen production by the IS cycle.

A Dirigible Heliostatic Solar Concentrator Array for Martian Industrial Applications

A spherical inflatable solar concentrator is proposed for use on the Martian surface with potential for high mobility and convenient sun tracking as well as high peak temperatures. A rover inside the inflatable concentrator is able, by moving along the floor, to cause the structure to roll such that the interior concentrator mirror can be aligned with the sun (sun tracking) over the course of the Martian day. Comparison is made to conventional solid mirror heliostats suggesting the investigated approach may offer significant advantages in flexibility as well as lower system mass and size. Applications for early stage processes well suited to the proposal are suggested, its strengths being in processes requiring high power consumption and maintenance of elevated temperatures for sustained periods, such as carbochlorination, zeolite manufacture and pneumatic gas heating. Presently unsolved issues are then examined and future directions for research suggested.

Efficiency and stability of seawater electrolysis through flat-tube solid oxide cell stack without air

Efficiency and stability are critical for solid oxide electrolysis cell (SOEC) applications. In this study, the effect of airless on the efficiency and stability of electrolysis seawater in a flat-tube SOEC stack is investigated. Considering gas heating loss, the maximum electrolysis efficiency of the stack with airless is 94.7 %, while that of the stack with air is 69.8 %. The 2-cell SOEC stack is operated for 500 h in airless at 300 mA/cm2 with an efficiency of 89.2 %. The degradation rate of Cell 1 and Cell 2 is 2.5 %/kh and 4.8 %/kh, respectively. The overall degradation of the stack is less than that of cell, which could be attributed to the improved interfacial contact between interconnect and cell inside the stack. The results show that the flat-tube SOEC stack has high efficiency and excellent stability for seawater electrolysis with airless, which provides a reference for efficient conversion and storage of offshore power.

In-situ TEM study from the perspective ofholders.

During the in situ transmission electron microscopy (TEM) observations, the diverse functionalities of different specimen holders play a crucial role. We hereby provide a comprehensive overview of the main types of holders, associated technologies and case studies pertaining to the widely employed heating and gas heating methods, from their initial developments to the latest advancement. In addition to the conventional approaches, we also discuss the emergence of holders that incorporate a micro-electro-mechanical system (MEMS) chip for in situ observations. The MEMS technology offers a multitude of functions within a single chip, thereby enhancing the capabilities and versatility of the holders. MEMS chips have been utilized in environmental-cell designs, enabling customized fabrication of diverse shapes. This innovation has facilitated their application in conducting in situ observations within gas and liquid environments, particularly in the investigation of catalytic and battery reactions. We summarize recent noteworthy studies conducted using in situ liquid TEM. These studies highlight significant advancements and provide valuable insights into the utilization of MEMS chips in environmental-cells, as well as the expanding capabilities of in situ liquid TEM in various research domains.

Stochastic optimal dispatch of offshore-onshore regional integrated energy system based on improved state-space approximate dynamic programming

The offshore-onshore regional integrated energy system (OORIES), which includes offshore gas production platforms and wind farms, along with the onshore gas-fired combined cooling, heating, and power supply campus, can effectively improve economic and environmental benefits by the complementary and coupling operation of multiple energies. In this paper, multi-energy coupling elements and multiple energy networks in the OORIES are modeled in detail. Considering the stochastic fluctuation of the offshore gas source and wind power output, a stochastic optimal dispatch (SOD) model of OORIES with multiple energy storages, including associated gas storage, hydrogen and heat storage tanks is proposed. Furthermore, a carbon trading mechanism is introduced to ensure the environmental benefits. An improved state-space approximate dynamic programming (SSADP) algorithm is proposed to solve the SOD model. By using the approximate value functions, the multi-period SOD model is decoupled into a series of single-period optimization models which are recursively solved period by period. The approximate analytical expression of the value function concerning states of each period is obtained based on the polynomial approximation, and combined with the transition probability matrices of stochastic quantities, an accurate and efficient solution for each single-period optimization model is obtained. A case study on an OORIES, and compared with the scenario-based algorithm, chance-constrained programming algorithm and traditional SSADP algorithm, demonstrates the effectiveness and high efficiency of the proposed method.

Heat integration, process design and techno-economic assessment of post-combustion carbon capture using piperazine for large-scale ethylene plant

With the development of increasingly larger ethylene plants and the associated requirement to reduce carbon emissions effectively, there is a growing need to explore approaches that reduce the cost and energy consumption in carbon capture from ethylene plants. In this study, the flue gas heat recovery (FHR) strategy was proposed and implemented for different configurations of piperazine (PZ)-based post-combustion carbon capture (PCC) process applied to an ethylene plant with a capacity of 60,000 t/year. Four different cases of the PZ-based PCC process with or without FHR were simulated in Aspen Plus® V11 to explore the cost reductions and energy saving potential. The advanced flash stripper (AFS) configuration with FHR and absorber inter-cooling achieves a minimum regeneration energy requirement of 2.28 GJ/tonCO2, a reduction of 37.71 % compared to standard PCC configuration using MEA solvent. The economic evaluation was carried out using Aspen Process Economic Analyzer® (APEA). The results show that the carbon capture cost using AFS configuration with FHR and inter-cooling can reduce to 47.27 $/tonCO2, a reduction of 36.76 % against the standard PCC process using MEA. The proposed technology presents significant technical and economic benefits for the large-scale deployment of carbon capture for ethylene plants.

On the design of a hydrogen micro-rectangular combustor for portable thermoelectric generators

Micro-combustion based thermoelectric generators have been proposed to power micro-electromechanical units. The present study aimed to optimize the thermal design of micro-combustor to best suit the requirement of thermoelectric generators. An equivalent heat transfer coefficient was used to consider the arranged thermoelectric generators and its effect was elucidated. Increasing the coefficient enhances combustor wall heat loss, reducing flame stability and uniformity index of temperature. It is thus impossible to constrain combustor outer wall temperature below the maximum allowable temperature of commercial thermoelectric generators (623K) simply through increasing equivalent heat transfer coefficient. To address this issue, three simple strategies of combustor channel modification, adding copper layer and using flue gas heat recirculation were developed. A notable improvement in uniformity index of temperature over 6.5% is achieved for the latter two strategies. Nevertheless, none of these three strategies can ensure outer wall temperature below 623K. Motivated by the different mechanisms to improve temperature uniformity and reduce wall temperature for the two simple strategies of adding copper layer and using flue gas heat recirculation, a hybrid strategy combining them was proposed. The hybrid strategy can maintain flame stability, improve uniformity index of temperature approach to 100% and control combustor outer wall temperature below 623K, making it a qualified strategy for designing high-performance micro-combustors.