Submucosal tunneling endoscopic resection of an exogenic esophageal mass in the mediastinum(with video)

Introduction Submucosal tunneling endoscopic resection(STER)for the treatment of upper gastrointestinal submucosal tumors originating from the muscularis propria was first introduced by Xu et al.[1]in 2012.It has been demonstrated to be safe and effective for treating small(<3.5 cm)esophageal leiomyoma.However,sometimes the esophageal leiomyoma may be a giant mass and protrude into the mediastinum.

Industrial-scale investigations on effects of tertiary-air declination angle on combustion and steam temperature characteristics in a 350-MW supercritical down-fired boiler

Industrial-scale experiments were conducted to study the effects of tertiary air declination angle(TDA)on the coal combustion and steam temperature characteristics in the first 350-MW supercritical down-fired boiler in China with the multiple-injection and multiple-staging combustion(MIMSC)technology at medium and high loads.The experimental results indicated that as the TDA increased from 0°to 15°,the overall gas temperature in the lower furnace rose and the symmetry of temperature field was enhanced.The ignition distance of the fuel-rich coal/air flow decreased.In near-burner region,the concentration of O2 decreased while the concentrations of CO and NO increased.The concentration of NO decreased in near-tertiary-air region.The carbon in fly ash decreased significantly from 8.40%to 6.45%at a load of 260 MW.At a TDA of 15°,the ignition distances were the shortest(2.07 m and 1.73 m)at a load of 210 MW and 260 MW,respectively.The main and reheat steam temperatures were the highest(557.2℃ and 559.4℃ at a load of 210 MW,558.4℃ and 560.3℃ at a load of 260 MW).The carbon in fly ash was the lowest(4.83%)at a load of 210 MW.On changing the TDA from 15°to 25°,the flame kernel was found to move downward and the main and reheat steam temperatures dropped obviously.The change of TDA has little effect on NO_(x) emissions(660–681 mg/m^(3) at 6%O_(2)).In comprehensive consideration of the pulverized coal combustion characteristics and the unit economic performance,an optimal TDA of 15°is recommended.

Influence of mass air flow ratio on gas-particle flow characteristics of a swirl burner in a 29 MW pulverized coal boiler

In a gas/particle two-phase test facility, a three-component particle-dynamics anemometer was used to measure the characteristics of gas/particle two-phase flows in a 29 megawatt (MW) pulverized coal industrial boiler equipped with a new type of swirling pulverized coal burner. The distributions of three-dimensional gas/particle velocity, particle volume flux, and particle size distribution were measured under different working conditions. The mean axial velocity and the particle volume flux in the central region of the burner outlet were found to be negative. This indicated that a central recirculation zone was formed in the center of the burner. In the central recirculation zone, the absolute value of the mean axial velocity and the particle volume flux increased when the external secondary air volume increased. The size of the central reflux zone remained stable when the air volume ratio changed. Along the direction of the jet, the peak value formed by the tertiary air gradually moved toward the center of the burner. This tertiary air was mixed with the peak value formed by the air in the adiabatic combustion chamber after the cross-section of x/d = 0.7. Large particles were concentrated near the wall area, and the particle size in the recirculation zone was small.

Numerical simulation of bituminous coal combustion in a fullscale tiny-oil ignition burner： Influence of excess air ratio

The progression of ignition was numerically simulated with the aim of realizing a full-scale tiny-oil ignition burner that is identical to the burner used in an 800 MWe utility boiler. The numerical simulations were conducted for four excess air ratios, 0.56, 0.75, 0.98 and 1.14 （corresponding to primary air velocities of 17, 23, 30 and 35 m/s, respectively）, which were chosen because they had been used previously in practical experiments. The numerical simulations agreed well with the experimental results, which demonstrate the suitability of the model used in the calculations. The gas temperatures were high along the center line of the burner for the four excess air ratios. The flame spread to the bumer wall and the high- temperature region was enlarged in the radial direction along the primary air flow direction. The O2 concentrations for the four excess air ratios were 0.5%, 1.1%, 0.9% and 3.0% at the exit of the second combustion chamber. The CO peak concentration was very high with values of 7.9%, 9.9%, 11.3% and 10.6% for the four excess air ratios at the exit of the second combustion chamber.