Suspension mechanism and application of sand-suspended slurry for coalmine fire prevention

North and west China has abundant coal resources, however, such resources make these regions prone to serious mine fire disasters. Although the copious sand and fly ash resources found in these areas can be used as fire-fighting materials, conventional grouting is expensive because of water shortage and loess particles. A new compound material(i.e., a sand-suspended colloid), which comprises a mineral inorganic gel and an organic polymer, is developed in the current study to improve the quality of sand injection and reduce water wastage when grouting. The new material can steadily suspend the sand, through the addition of a small amount of colloid yielding steady sand-suspended slurry. The process of producing the slurry is convenient and quick, overcoming the shortage of sand-suspending thickeners which need heat and are difficult to produce. The space work model based on the theory of the double-electric layer is established to study the suspended mechanism of the solid particles in the sand-suspended colloid.The dispersion effect of the sand-suspended colloid is demonstrated by the incorporation of the electrostatic effect by the double-electric layer and the steric hindrance effect on the sand particles, ensuring the stability of the colloid system and the steady suspension of sand particles in the sand-suspended colloid.Mechanical analysis indicates that the sand is suspended steadily under the condition that the rock sand particles stress on the lower part of the fluid is less than the yield stress of the colloid. Finally, the fireprevention technology of sand suspension was applied and tested in the Daliuta Coal Mine, achieving successful results.

Study on the Effect of Catalyst Properties on Residue Hydroconversion

The effect of catalyst properties on residue oil hydroconversion was studied at moderate operating conditions(at a temperature of 400 ℃, an initial hydrogen pressure of 10 MPa, and a reaction time of 4 h) in a batch mode slurry phase with different catalyst samples. The results showed that the catalyst acidity had a good effect on residue conversion and MCR(micro carbon residue) conversion but brought about higher coke yield. Residue conversion was thermally induced but the catalyst acidity changed its conversion route. A catalyst with higher metal loading, higher hydrogenation activity and appropriate pore size had higher sulfur and metal removal rate, higher MCR conversion and also a lower coke formation. The activity of spent commercial catalyst AS1 and DS1 was slightly lower than the corresponding fresh ones but was still high enough for residue oil hydroconversion. It assumes that the role of the catalyst is to activate hydrogen species toward reaction with an aromatic carbon radical to yield a cyclohexadienyl type intermediate which will turn into liquid and also to absorb the mesophase which can easily aggregate to form coke.

Planarization mechanism of alkaline copper CMP slurry based on chemical mechanical kinetics

The planarization mechanism of alkaline copper slurry is studied in the chemical mechanical polishing （CMP） process from the perspective of chemical mechanical kinetics.Different from the international dominant acidic copper slurry,the copper slurry used in this research adopted the way of alkaline technology based on complexation. According to the passivation property of copper in alkaline conditions,the protection of copper film at the concave position on a copper pattern wafer surface can be achieved without the corrosion inhibitors such as benzotriazole（BTA）,by which the problems caused by BTA can be avoided.Through the experiments and theories research,the chemical mechanical kinetics theory of copper removal in alkaline CMP conditions was proposed. Based on the chemical mechanical kinetics theory,the planarization mechanism of alkaline copper slurry was established. In alkaline CMP conditions,the complexation reaction between chelating agent and copper ions needs to break through the reaction barrier.The kinetic energy at the concave position should be lower than the complexation reaction barrier,which is the key to achieve planarization.