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The application of existing gas transmission pipelines to deliver hydrogen-blended natural gas is the most operable method among many delivery methods. Hydrogen-blended natural gas with different hydrogen-blending ratios after passing through the throttling element is not the same. Using FLUENT to analyze the temperature variation after the Joule–Thomson effect for 0%, 5%, 10%, 20%, and 30% hydrogen mixing ratios. Workbench is used to analyze the soil temperature field around the pipeline and the stress displacement of the buried pipeline in the permafrost zone under different hydrogen mixing ratios. The analysis revealed that as the hydrogen mixing ratio increases, the temperature of the same point gradually increases after the Joule–Thomson effect, the low-temperature area around the buried pipe is gradually replaced by the high-temperature area, and the stress of the buried straight pipe also gradually decreases; while the maximum stress of the pipe initially decreases and then increases, and the displacement has no obvious change. Buried pipelines, which are generally accepted worldwide as one of the many forms of natural gas transmission, pass through permafrost areas during their laying, thus triggering freeze-ups and posing a potential hazard to the safe transportation of natural gas. Most of the existing methods to solve the frozen rise of buried pipelines in the permafrost zone have problems of high energy consumption and construction difficulties. Therefore, this paper, combined with the current trend of vigorous development of hydrogen-blending natural gas projects around the world, proposes a method to alleviate the purpose of freeze-ups by inputting a reasonable hydrogen-blending ratio before the regulator through the negative Joule–Thomson effect of hydrogen and using the phenomenon of temperature rise along the pipeline after the hydrogen passes through the regulator to neutralize the temperature drop of pure natural gas. In this paper, we applied finite element analysis software to simulate the effect of five mixing ratios of hydrogen gas, such as 0%, 5%, 10%, 20%, and 30%, on buried pipelines and also selected 0%–5% as the best mixing ratio to relieve freezing under the working conditions of the simulation environment. The feasibility of delivering hydrogen-blended natural gas at appropriate blending ratios to mitigate freeze-ups in buried pipelines in permafrost areas is demonstrated. It provides a new method for freeze-rise mitigation measures at gas transmission sites. [ABSTRACT FROM AUTHOR]

In order to investigate the effect of different nonionic surfactants on hydrate formation in oil-water emulsion systems, the hydrate formation experiments were carried out in a diesel water-in-oil emulsion system with a water cut of 40% using nonionic surfactants such as Span80, Tween80, Span20 and Tween20, respectively. The results show that under the experimental conditions of 275 K and 7 MPa, a certain concentration of nonionic surfactant can promote the growth of hydrates in diesel emulsion systems, shorten the hydration reaction time, and have a significant effect on the improvement of gas storage density. The combination of Span80 and Tween80 in a mass ratio of 1:1 was the most effective in promoting the formation of hydrate in the emulsion system. When the mass fraction was 0.5%, the hydration reaction time was the shortest and the hydrate gas storage density was the highest. Due to the addition of the nonionic surfactant, a stable interfacial film and interfacial charge are formed around the water droplets of the emulsion system, making it difficult for the droplets to approach and polymerize, which maintains the stability of the water-in-oil emulsion system and has great reference value for the study of hydrate storage and transportation. [ABSTRACT FROM AUTHOR]

It is great significant to explore the changes of compressor performance for hydrogen transportation. We found that a Gray-RBF neural network prediction model improved prediction accuracy. The prediction error of the model is 2.34 % by data verification. It was found that the hydrogen blending ratio was increased from 0 % to 30 %, the pipeline transmission power was reduced by 9.3 %. Simultaneously injecting hydrogen to natural gas causes the performance curve of the compressor to shift downwards. The pressure ratio decreases by 18.9 % and shaft power decreases by 28.6 % when the hydrogen blending ratio increases from 0 % to 30 %. The injection of hydrogen to natural gas causes the surge range of the compressor to increase, so the stable range to narrow. In general, this research may provide reference and guidance for the transportation research of hydrogen blended natural gas and compressor operation about gas industry. [Display omitted] • Creating a combination model improved the accuracy of performance prediction. • Injecting hydrogen into natural gas reduced the power of pipeline gas transmission. • Enlarging initial pressure caused the gas transmission power increase. • Injecting hydrogen into natural gas caused decreases of compressor performance curves. • Injecting hydrogen into natural gas increased the surge range of the compressor. [ABSTRACT FROM AUTHOR]

• Proposed a novel combined cooling, heating, and power system. • Applied exergoeconomic analysis to evaluate the economic performance. • Used multi-objective optimization to find the optimal working conditions. • Exhibited an exergy efficiency of 80.49% and a product unit cost of 48.04 $/GJ. With the increase of liquified natural gas trade, more and more attention has been paid to the liquified natural gas cold energy utilization. In order to better recover and utilize liquified natural gas cold energy, a novel combined cooling, heating and power system based on liquified natural gas cold energy utilization and exhaust gas waste heat recovery is proposed in this paper. The system consists of a three-stage organic Rankine cycle, a Kalina cycle and liquified natural gas direct expansion. To evaluate the performance of the combined cooling, heating and power system, a mathematical model was established, and through the thermodynamic analysis the net output power, thermal efficiency, and exergy efficiency of the system were 1257.708 kW, 43.43%, and 70.4%, respectively. The effects of the pump and compressor outlet pressure, n -hexane mass flow rate in the first Rankine cycle, turbine inlet temperature, and isentropic efficiency of the turbines on the system performance were analyzed. Moreover, exergoeconomic analysis is used to calculate the total product unit cost of the combined cooling, heating and power system, which was found to be 51.1 $/GJ. In addition, single- and multi-objective optimizations of the system were performed. The multi-objective optimization results show that the maximum exergy efficiency and minimum total product unit cost of this novel combined cooling, heating and power system were 80.49% and 48.04 $/GJ, respectively. This work shows a great potential in utilizing the liquified natural gas cold energy and waste heat of exhaust gas by a combined cooling, heating and power system. [ABSTRACT FROM AUTHOR]