Phase equilibria and methane enrichment of clathrate hydrates of mine ventilation air + tetrabutylphosphonium bromide

This paper reports the experimentally measured phase equilibrium conditions for the clathrate hydrates formed from simulated mine ventilation air (0.50 vol % CH + 99.50 vol % air) in the presence of 0, 5, 20, 37.1, and 50 wt % of tetrabutylphosphonium bromide (TBPB). These equilibrium conditions were measured at the temperature range of 281.62-292.49 K and pressure range of 1.92-18.55 MPa by using an isochoric equilibrium step-heating pressure search method. The results showed that addition of TBPB allowed the hydrate dissociation condition for mine ventilation air to become milder, and at a given temperature, the lowest hydrate dissociation pressure was achieved at 37.1 wt % TBPB, corresponding to the stoichiometric composition for TBPB·32H O. For each TBPB concentration tested, the semilogarithmic plots of hydrate dissociation pressure versus reciprocal absolute temperature can be satisfactorily fitted to two straight lines intersecting at 6.5 MPa. The slopes of these fitted straight lines are indifferent to changes in TBPB concentration. Gas composition analysis by gas chromatography also found that in the presence of 37.1 wt % TBPB, CH could be enriched approximately 3.5-fold in the hydrate phase

Growing Typhoon Influence on East Asia

Numerical model studies have suggested that the ongoing global warming will likely affect tropical cyclone activity. But so far little observed evidence has been detected to support the projected future changes. Using satellite-supported best-track data from 1965 to 2003, we show for the first time that over the past four decades the two prevailing typhoon tracks in the western North Pacific (WNP) have shifted westward significantly; the typhoon activity over the South China Sea has considerably decreased; and East Asia has experienced increasing typhoon influence. Our trajectory model simulation indicates that the long-term shifts in the typhoon tracks result primarily from the changes in the mean translation velocity of typhoons or the large-scale steering flow, which is associated with the westward expansion and strengthening of the WNP subtropical high

Development of Downhole Motor Drilling Test Platform

AbstractThe Downhole motor is a kind of important rotary or percussive power drilling tool driven by high pressure mud. Drilling using downhole motor can reduce the energy consumption caused by the friction between long drill string and borehole, and reduce drill pipe wear. In this paper, some important drilling simulation experimental devices around the world have been studied, especially, two kind of drilling simulation experimental devices, the conventional bottom hole experimental device and high temperature and high pressure experimental devices have been analyzed respectively. At home and abroad, the typical drilling simulation devices include ZM-35, LST-10, LMT-I, M150, and Terra Tek, etc.. The characters, structures, principles and experimental methods of these typical simulation devices had been introduced in detail, which provides a reference for developing downhole motor testing and drilling process testing

Changes in Tropical Cyclone Intensity Over the Past 30 Years: A Global and Dynamic Perspective

The hurricane season of 2005 was the busiest on record and Hurricane Katrina (2005) is believed to be the costliest hurricane in U. S. history. There are growing concerns regarding whether this increased tropical cyclone activity is a result of global warming, as suggested by Emanuel(2005) and Webster et al. (2005), or just a natural oscillation (Goldenberg et al. 2001). This study examines the changes in tropical cyclone intensity to see what were really responsible for the changes in tropical cyclone activity over the past 30 years. Since the tropical sea surface temperature (SST) warming also leads to the response of atmospheric circulation, which is not solely determined by the local SST warming, this study suggests that it is better to take the tropical cyclone activities in the North Atlantic (NA), western North Pacific (WNP) and eastern North Pacific (ENP) basins as a whole when searching for the influence of the global-scale SST warming on tropical cyclone intensity. Over the past 30 years, as the tropical SST increased by about 0.5 C, the linear trends indicate 6%, 16% and 15% increases in the overall average intensity and lifetime and the annual frequency. Our analysis shows that the increased annual destructiveness of tropical cyclones reported by Emanuel(2005) resulted mainly from the increases in the average lifetime and annual frequency in the NA basin and from the increases in the average intensity and lifetime in the WNP basin, while the annual destructiveness in the ENP basin generally decreased over the past 30 years. The changes in the proportion of intense tropical cyclones reported by Webster et a1 (2005) were due mainly to the fact that increasing tropical cyclones took the tracks that favor for the development of intense tropical cyclones in the NA and WNP basins over the past 30 years. The dynamic influence associated with the tropical SST warming can lead to the impact of global warming on tropical cyclone intensity that may be very different from our current assessments, which were mainly based on the thermodynamic theory of tropical cyclone intensity