Chenwei Liu,Chongrui Zhang,Chenru Zhou,Yongfei Mi,Zhiyuan Wang
The presence of unconverted water drops in bulk hydrocarbon is likely to bridge hydrate particles and cause hydrate agglomeration, leading to hydrate accumulation or bedding in oil and gas pipelines. The knowledge of the interaction forces between hydrate particles and water drops can provide critical insights into hydrate agglomeration as well as potential prevention strategies. At high subcooling, the frequent solidification of the capillary bridge between hydrate particles could significantly affect the interaction force. However, the existing classic pendular liquid bridge model with a fixed liquid volume is not adequate for this unique case. A new interaction force model is required. Based on the pendular liquid bridge model and hydrate shell theory, a modified interaction force model was developed by considering the solidification of capillary bridges. Furthermore, using a self-built micromechanical force apparatus, the cyclopentane (CyC5) hydrate–droplet adhesion forces at a temperature range from 0.5 to 6 °C were measured to verify the proposed model. The experiments suggest that as the temperature was increased from 0.5 to 6 °C, the adhesion forces first increased and then decreased. Solidification could enhance the strength of the already formed liquid bridge. However, at lower temperatures (0.5–3 °C), the quick solidification led to smaller particle/bridge initial contact areas and weaker adhesion forces. By accurately predicting the evolution of the capillary bridge shape/outline, the predicted adhesion forces agree well with the experimental measurements. This study can provide more insights into hydrate agglomeration. The proposed model is an important supplement to hydrate adhesion theory and could more accurately evaluate hydrate plug risks in gas–oil flowlines.
Lu Jing,Zhiguo Yu,Lihua Peng,Yongsheng Ji,Deren Yang,Xuegong Yu
Micro and nano bubbles assisted mineral particle flotation can effectively improve the surface hydrophobicity of mineral particles, increase the probability of collision and adhesion between particles and air bubbles. Meanwhile, selecting suitable flotation combination collectors can also enhance the selectivity of mineral particles for further improving the flotation recovery of minerals. In this study, under the presence of micro bubbles, a high quartz flotation recovery of 98.3 % was obtained by a combination collector of DTAC/SDS with the molar ratio of 1: 1 and the dosage of 700 mg/L at pH 9. According to the extended DVLO theory, the relationship between Van der Waals interaction energy ( E v ), hydrophobic interaction energy ( E h ), electric double-layer interaction energy ( E e ) and flotation factors such as the type and concentration of flotation reagents, pH of solution and micro bubble treatment was the deeply investigated. The mechanism of micro bubbles enhancing quartz flotation behavior is regarded as the generated strong capillary bridge attraction between the air bubbles on the surfaces of two hydrophobic particles, which promotes large amounts of fine particles aggregating and forming larger hydrophobic particles. Thereby, the probability of collision and adhesion between bubbles and particles significantly increases and flotation efficiency improves. The experimental results are also evidenced by the calculation of total interaction energy ( E t ) and energy barrier.
Polyaniline-based conductive polymers are promising electrochemical sensor materials due to their unique physical and chemical properties, such as good gas absorption, low dielectric loss, and chemical and thermal stabilities. The sensing performance is highly dependent on the structure and dimensions of the polyaniline-based conductive polymers. Although in situ oxidative polymerization combined with the self-assembly process has become one of the main processes for the preparation of flexible polyaniline-based gas sensors, how to prepare polyaniline materials into uniformly arranged microwire arrays is still an urgent problem. In this paper, an in-depth study was conducted on the preparation of polyaniline microwire arrays by combining a wettability interface dewetting process and a liquid-film-induced capillary bridges method. The factors influencing the preparation of polyaniline microwire arrays, including solution concentration, template width, evaporation temperature, and evaporation time, were investigated in detail. The wire formation rates were recorded from the results of SEM images. 100% microwires formation rate can be obtained by using a 1.0 mg mL–1 concentration of polyaniline solution and a 10 μm silicon template at an evaporation temperature of 80 °C for 18 h. The prepared microwire arrays can realize sulfur dioxide sensing at room temperature with a response speed of about 20 s and can detect sulfur dioxide gas as low as 1 ppm. Thus, the liquid-film-induced capillary bridge method shows a new possibility to prepare gas sensor devices for insoluble polymers.
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