Effect of occurrence mode of heavy metal elements in a low rank coal on volatility during pyrolysis

The harmful trace elements will be released during coal utilization, which can cause environment pollution and further endangering human health, especially for heavy metal elements. Compared to combustion, the release of heavy metal elements during coal pyrolysis process, as a critical initial reaction stage of combustion, has not received sufficient attention. In the present paper, a low rank coal, from Xinjiang province in China, was pyrolyzed in a fixed bed reactor from room temperature, at atmospheric pressure, with the heating rate of 10 °C/min, and the final pyrolysis temperature was from 400 to 800℃ with the interval of 100℃. The volatility of heavy metal elements (including As, Hg, Cd and Pb) during pyrolysis process was investigated. The results showed the volatility of all heavy metal elements increased obviously with increasing temperature, and followed the sequence as Hg > Cd > As > Pb, which was mainly caused by their thermodynamic property and occurrence modes in coal. The occurrence modes of heavy metals were studied by sink-andfloat test and sequential chemical extraction procedure, and it can be found that the heavy metal elements were mainly in the organic and residual states (clay minerals) in the raw coal. And most of the organic heavy metals escaped during the pyrolysis process, the remaining elements were mainly in the residual state, and the elements in Fe-Mn state also tended to remain in the char.

Morphology and Function of the Aortic Valve after Transcatheter Closure of Ventricular Septal Defect with Aortic Valve Prolapse

Objective:This study aims to evaluate the morphology and function of the aortic valve after transcatheter closure of ventricular septal defect(VSD)with aortic valve prolapse(AVP)abased on clinical and radiological outcomes.Methods:From January 2013 to November 2014,164 consecutive patients(97 males,59.1%)with VSD and AVP were treated by transcatheter closure.The patients were divided into the mild AVP group(n=63),moderate AVP group(n=89)and severe AVP group(n=12).The clinical and radiological outcomes of these patients were analyzed retrospectively.Results:In total,146(89.0%)patients were successfully treated with VSD occluders,including 59/63(93.7%)with mild AVP,80/89(89.9%)with moderate AVP and 7/12(58.3%)with severe AVP.The degree of AVP was ameliorated or disappeared in 39(26.7%)patients,and remained unchanged in 103(70.5%)patients after the intervention.In the 35 patients who initially had trivial-to-moderate aortic regurgitation(AR),the degree of AR was ameliorated or disappeared in 25(71.4%)patients,aggravated from trivial to mild AR in 1(2.9%)patient,and remained unchanged in 9(25.7%)patients.In 111 patients without AR,1(0.9%)patient had mild AR and 24(21.6%)patients had trivial AR after intervention.The depth and width of the prolapsed aortic valve decreased after transcatheter closure of VSD in all three groups.During the 70-month(range,54–77)follow-up period,no patients with AVP and AR needed an aortic valve intervention.Conclusions:Transcatheter closure of VSD with AVP is feasible.The morphology and function of the prolapsed aortic valve improved and remained stable for a long period after intervention.