REACTION CHARACTERISTICS OF TWO WATER GAS SHIFT CATALYSTS IN A BUBBLING FLUIDIZED BED REACTOR FOR SEWGS PROCESS

Reaction characteristics of two WGS catalysts for SEWGS process were investigated in a bubbling fluidized bed reactor. The commercial low temperature WGS catalyst produced by Süd-chemie and new catalyst produced by spray-drying method were used as bed materials. Reaction temperature, steam/CO ratio, and gas velocity were considered as experimental variables. Moreover, long-term operation results of two WGS catalysts were compared as well

Surgical repair of descending thoracic and thoracoabdominal aortic aneurysm involving the distal arch: Open proximal anastomosis under deep hypothermia versus arch clamping technique

BackgroundSurgical repair of a descending thoracic and thoracoabdominal aortic aneurysm (DTA/TAAA) involving the distal arch is challenging and requires either deep hypothermic circulatory arrest (DHCA) or crossclamping of the distal arch. The aim of this study was to compare these 2 techniques in the treatment of DTA/TAAA involving the distal arch.MethodsFrom 1994 to 2012, 298 patients underwent open repair of DTA/TAAA through a left thoracotomy. One hundred seventy-four patients with distal arch involvement who were suitable for either DHCA (n = 81) or arch clamping (AC; n = 93), were analyzed. In-hospital outcomes were compared using propensity scores and inverse-probability-of-treatment weighting adjustment to reduce treatment selection bias.ResultsEarly mortality was 11.1% in the DHCA group and 8.6% in the AC group (P = .58). Major adverse outcomes included stroke in 16 patients (9.2%), low cardiac output syndrome in 15 (8.6%), paraplegia in 10 (5.7%), and multiorgan failure in 10 (5.7%). After adjustment, patients who underwent DHCA were at similar risk of death (odds ratio [OR], 1.14; P = .80) and permanent neurologic injury (OR, 0.95; P = .92) to those who underwent AC. Although prolonged ventilator support (>24 hours) was more frequent with DHCA than with AC (OR, 2.60; P = .003), DHCA showed a tendency to lower the risk of paraplegia (OR, 0.15; P = .057).ConclusionsCompared with AC, DHCA did not increase postoperative mortality and morbidity, except for prolonged ventilator support. However, DHCA may offer superior spinal cord protection to AC during repair of DTA/TAAA involving the distal arch

Effects of production parameters on microstructure and densification of iron/glass syntactic foam by conventional powder metallurgy

Iron and steel matrix syntactic foams have received a lot of attention owing to their high strength, temperature capability, and corrosion resistance. However, high melting point of the iron and steels complicates applications of some conventional production processes. Since few casting methods were proposed to fabricate iron and steel syntactic foams embedded with the ceramic and metal hollow spheres having macro diameters, most of the foams having micro ceramic and glass hollow spheres were fabricated through powder metallurgy (PM) process, which allows reduction of temperature levels by about 30~40% compared to the casting. Metal injection molding (MIM) was mostly used toward the iron and steel matrix foams because of requiring only limited adaptations for switching from making solid parts to syntactic foams and its capabilities for producing various geometries and sizes. However, if the shape allows the production of the part by conventional PM (pressing and sintering), MIM would in most cases be too expensive. To date, detailed fundamental researches on conventional PM process to fabricate the iron or steel syntactic foams have not been reported. Difficulties of the conventional PM process to fabricate the iron and steel syntactic foams are working pressures and temperatures. For compacting powders to make green bodies, high working pressures can assist the densification of the matrix during sintering while this can deform or fracture the hollow spheres embedded. In case of the foams with the glass hollow spheres, softening of the glass occurs at high temperature thus original shape of the hollow spheres cannot be preserved. Therefore, to overcome the difficulties and to produce sound sintered bodies, the investigation on the production parameters of the conventional PM to fabricate the iron and steel syntactic foams is necessary. In this study, the iron/glass hollow spheres syntactic foams were fabricated via the conventional PM process. Fabrications were conducted with considering different production parameters, which included the compaction pressures and sintering temperatures in conjunction with various volume fractions and particle sizes of the hollow spheres. The microstructures and densification behaviors of the fabricated syntactic foams were characterized by X-ray diffraction, optical microscope, scanning electron microscope and energy dispersion spectroscope

A Study of Solids and Gas Mixing in a Partitioned Fluidized Bed

A partitioned fluidized bed gasifier has been developed for improving coal gasification performance. The basic concept is to divide a fluidized bed into two parts, a gasifier and a combustor, by a partition. Char is burnt in the combustor and generated heat is supplied to the gasifier by solid mixing. Therefore, solid mixing should be maximized whereas gas mixing between syngas and the combusted gas should be minimized. In this study, gas and solid mixing behaviors were verified in cold model acrylic beds. For monitoring solid mixing behavior, transient temperature trends in the beds were analyzed. A heat source and a heat sink were installed in each bed. Dozens of thermocouples were used to monitor temperature distribution

Titanium Plate Fixation for a Dehisced Sternum Following Coronary Artery Bypass Grafting: A Case Report

Sternal dehiscence is one of the most troublesome complications following cardiac surgery. Treatment failure and consequent lethal results are very common, even with all the efforts to resolve sternal dehiscence such as removal of infectious tissue, muscle flap interposition, and sternal rewiring. We report on a case of sternal osteomyelitis following coronary artery bypass grafting that was successfully treated with wide sternal resection, titanium plate fixation, and pectoralis muscle flap interposition