In order to solve the problem where the traditional intelligent inspection robot only has a single inspection function, we studied the use of a dry powder (including an ultra-fine dry powder) as a fire-extinguishing medium for the first time. In fire-extinguishing robots, the spray pressure is difficult to control, and there are several other issues. For integrated inspection, an intelligent, nitrogen-driven fire-extinguishing robot using a dry powder in a pressure-controlled spray was developed. On this basis, in order to investigate nitrogen-driven dry powder particle spraying as a gas–solid two-phase mechanism, as well as the flow characteristics and the influence of relevant parameters on the spraying effect, a nitrogen-driven dry powder particle spraying system was established as part of a gas–solid two-phase computational fluid dynamics model. The flow field of the spraying system and the particle motion characteristics were analyzed to explore the micro-mechanisms of the influence of different driving pressures, pipe diameters, and nozzle configurations on the spraying of the dry powder. In order to investigate the macroscopic effect of dry powder spraying where the gas–solid two-phase micro-mechanisms could not be revealed, an experimental platform was set up, and the experiments verified the accuracy of the numerical simulation results. We also investigated the dry powder spraying effect under different driving pressures, pipe diameters, nozzle configurations, and loading ratios. Finally, an orthogonal test was designed based on the results of the single-factor experiments to find the best combination of parameters required to achieve the optimal spraying effect. The research results can provide a theoretical and technical reference for the design and development of nitrogen-driven dry powder spraying systems.

In order to ensure the safe and economic operation of waxy crude oil transportation process, the micro-dynamic mechanism and thermodynamic characteristics of wax precipitation process at nanoscale are necessary to be revealed. Here, we established the molecular dynamics model to characterize the phase transition and precipitation behavior of waxy molecules in multiphase system (including oil, asphaltene and water), the relative error between simulated results and experimental data measured by Dutour et al. (2002) is less than 5%. Under the coupling effect of different operation parameters, the molecular dynamics simulation was employed, the simulated results showed that the spherical paraffin crystals underwent the process of dissolution, diffusion and aggregation, then the waxy cluster crystals with larger amount but smaller volume would form, and it would deposit on the outer wall under the concentration gradient. The influence mechanism of different operating parameters on wax precipitation was analyzed, of which the increase of temperature and water cut will decrease the wax precipitation, while the increase of pressure will enhance the wax precipitation rate, furthermore, by means of the hydrogen bonding and the effect of similar dissolution, the water and asphaltene molecules also affect the wax precipitation process at molecular-scale. The researches of this paper provide the theoretical support for the paraffin removal and control in waxy crude oil pipeline transportation process.

In order to ensure efficiency of Trans-Asia Gas Pipeline, engineers in Sino-Petroleum International Company optimized pipeline operation from a whole view through simulated optimization and unit control optimization. The network model of ABC line is established using TGNET, and the error of model is adjusted to the acceptable range by using the practical data. Flow distribution of AB line and C line is optimized to ensure the minimum fuel cost. Principle of gas pack control is built in different working conditions. And the compressor unit is controlled according to the simulation results. Performance of compressor unit is monitored and control mode is regulated to a better way on the basis of data analysis and investigation. After more than one year of exploration and practice, the operation optimization methodology of the Trans-Asia Gas Pipeline has been established. Energy-saving effect is remarkable.