Nano-polydopamine-graphene oxide-TiO₂ (nano-PDA@GO-TiO₂) composites were prepared by dopamine modified graphene oxide (GO) and loaded nano-TiO₂ on the surface of GO. The structure and morphology of nano-PDA@GO-TiO₂ composites were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Raman, X-ray photoelectron spectroscopy (XPS), Scanning electron microscope (SEM), and Transmission electron microscope (TEM) Results demonstrate that the introduction of dopamine to functionalize the GO could self-polymerize polydopamine (PDA) on the surfaces of the GO and endow abundant chemical groups reduce the GO. The interaction between the GO and nano-TiO₂ particles could prevent graphene nanosheets from restacking and nano-TiO₂ particles from agglomeration. Nano-PDA@GO-TiO₂ composite material was used as the nano-filler, and nano-PDA@GO-TiO₂ composites waterborne epoxy resin coatings (PGT/WEP) were prepared by dispersing a different content of nano-PDA@GO-TiO₂ composites into waterborne epoxy resin with the help of ultrasonic dispersion and mechanical agitation. The physical properties of PGT/WEP coatings, such as hardness, impact resistance, and adhesion, were tested and the electrochemical performance was evaluated. The results show that dispersing 2% nano-PDA@GO-TiO₂ composites in waterborne epoxy resin could significantly improve the physical properties and corrosion resistance of waterborne epoxy resin coating when compared with pure waterborne epoxy coating.

The main difficulties in applying technologies based on hydrate formation are the slow hydrate formation rate, low storage capacity, severe formation conditions and environmentally devastating promoters. Nano-sized graphene oxide has special microstructure features such as its functional groups and a large specific surface area, which can lead to high heat and mass transfer efficiency, large gas dissolution, fast nucleation and formation rate. In this work, CO₂ hydrate formation with and without graphene oxide nanoparticles was investigated. Herein, the promoting mechanism and effects of graphene oxide concentrations in different initial pressures ranging from 3 to 5 MPa at 279 K on CO₂ hydrate formation process were studied experimentally. The experimental results showed that graphene oxide can shorten the induction time by 53–74.3% and increase the gas consumption up to 5.1–15.9% under different system pressures. Based on the results, the optimum concentration was ascertained as 50 ppm under which condition, the induction time and the reaction time were the shortest while the pressure drop and the gas consumption reached the maximum.

Hydrate generation promotion and kinetic models are key issues in the hydrate utilization technology. The formation kinetics of CO₂ hydrates in a graphene oxide (GO) and sodium dodecyl sulfate (SDS) compounding accelerator system was studied experimentally, and the influences of different concentrations on the hydrate formation time and gas consumption were revealed. The results show that with the combination of GO and SDS, the formation rate of CO₂ hydrates was accelerated, the induction time and generation time were shortened, and the gas consumption increased. The optimal compounding concentration was 0.005% GO and 0.2% SDS. Compared with the observations for pure water and a single 0.005% GO system, the hydrate formation time was shortened by 69.7% and 12.2%, respectively, and the gas consumption increased by 11.24% and 3.2%. A chemical affinity model of CO₂ hydrate formation was established for this system. The effects of the GO and SDS compound ratio, temperature and pressure on the chemical affinity model parameters were studied from the model point of view. On using Matlab to program the model and compare it with the experimental results, very good agreement was achieved. Through research, the chemical affinity model can accurately predict the formation of hydrates in complex systems.

The gas–liquid contact area can be increased by the gas–liquid swirl flow, and the heat and mass transfer efficiency between gas and liquid can be enhanced by the gas–liquid swirl flow. The gas hydrate formation can be promoted by the swirl flow. The swirl flow can ensure the safety of the natural gas hydrate slurry. The flow pattern and conversion law of gas–liquid swirl with a twist tape should be investigated, and numerical simulation has been carried out by using the Reynolds stress model and the level set model. As a result, four different flow patterns are obtained, namely, swirl-stratified flow, swirl bubble flow, swirl slug flow, and swirl annular flow. The influence of gas–liquid-phase velocity on the flow pattern is investigated. The drag force generated by the two-phase slip velocity can change the gas form. At the same time, the flow pattern at different positions of the pipe will also change because of the attenuation of the swirl flow. Finally, the flow pattern map of the gas–liquid swirl flow is accomplished, and it is compared with the Mandhane flow pattern map. The flow boundary of the swirl bubble flow and the swirl annular flow is predicted.

The natural gas hydrate plugging problems in the mixed pipeline are becoming more and more serious. The hydrate plugging has gradually become an important problem to ensure the safety of pipeline operation. The deposition and heat transfer characteristics of natural gas hydrate particles in the spiral flow pipeline have been studied. The DPM model (discrete phase model) was used to simulate the motion of solid particles, which was used to simulate the complex spiral flow characteristics of hydrate in the pipeline with a long twisted band. The deposition and heat transfer characteristics of gas hydrate particles in the spiral flow pipeline were studied. The velocity distribution, pressure drop distribution, heat transfer characteristics, and particle settling characteristics in the pipeline were investigated. The numerical results showed that compared with the straight flow without a long twisted band, two obvious eddies are formed in the flow field with a long twisted band, and the velocities are maximum at the center of the vortices. Along the direction of the pipeline, the two vortices move toward the pipe wall from near the twisted band, which can effectively carry the hydrate particles deposited on the wall. With the same Reynolds number, the twisted rate was greater, the spiral strength was weaker, the tangential velocity was smaller, and the pressure drop was smaller. Therefore, the pressure loss can be reduced as much as possible with effect of the spiral flow. In a straight light flow, the Nusselt number is in a parabolic shape with the opening downwards. At the center of the pipe, the Nusselt number gradually decreased toward the pipe wall at the maximum, and at the near wall, the attenuation gradient of the Nu number was large. For spiral flow, the curve presented by the Nusselt number was a trough at the center of the pipe and a peak at 1/2 of the pipe diameter. With the reduction of twist rate, the Nusselt number becomes larger. Therefore, the spiral flow can make the temperature distribution more even and prevent the large temperature difference, resulting in the mass formation of hydrate particles in the pipeline wall. Spiral flow has a good carrying effect. Under the same condition, the spiral flow carried hydrate particles at a distance about 3–4 times farther than that of the straight flow.