Plasma fixed bed gasification using an Eulerian model
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
Authors: Ismail, Tamer M.; Ramos, Ana; Abd El-Salam, M.; Monteiro, Eliseu; Rouboa, Abel
Abstract
Gasification of solid waste is considered as a green and sustainable solution to perform energy recovery from several waste streams. This work aims to adapt an Euler-Euler multiphase mathematical model to understand the effects of physical and chemical factors, i.e. equivalence ratio (ER), steam to fuel ratio (SFR), and input plasma power of municipal solid waste (MSW) fixed bed gasification. The model is capable of simulating temperature and velocity fields, as well as gas and solid composition variations inside the reactor. A two-step pyrolysis model is used considering the pyrolysis mechanism of cellulose and plastic components. Drying, pyrolysis, homogeneous gas reactions, and heterogeneous combustion/gasification reactions were also included in the model. It was shown that the proposed model could provide accurate predictions against experimental data with a deviation generally lesser than 10%. Conclusion could be drawn that an ER of 0.3 and an SRF of 0.5 seems to be the most favourable conditions in order to obtain a high- quality syngas. Higher plasma power is favourable to obtain a high-quality syngas. However, the high electric power required penalizes the process efficiency and may compromise the economic viability of a plasma gasification project. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
Sulphur hexafluoride (SF6) intravitreal injection combined with argon laser photocoagulation for treatment of optic disc pit maculopathy
EYE
Authors: Elmohamady, Mohamed Nagy; Khalil, Mohamed Taha Ibrahim; Bayoumy, Ahmed Sherin Mustafa; Rateb, Mahmoud; Faramawi, Husam Mustafa
Abstract
Purpose To evaluate clinical efficacy of combined sulphur hexafluoride (SF6) gas tamponade and laser photocoagulation for optic disc pit maculopathy (ODPM). Methods Eleven eyes of nine patients with optic disc pit maculopathy were treated with intravitreal injection of 0.6 ml 100% sulphur hexafluoride (SF6) combined with laser photocoagulation treatment. Patients were followed up for a mean of 28.54 months (range of 14-57 months) after treatment. The anatomical success was shown by optical coherence tomography (OCT) and the functional outcome was judged by best corrected visual acuity. Results Treatment with SF6 gas tamponade followed by laser photocoagulation in OPDM patients resulted in resolution of subretinal fluid (SRF) in 82% of eyes after single injection. Repeated injection was needed in two eyes to achieve resolution of SRF. Visual acuity improved significantly from a mean of 0.83 +/- 0.14 logMAR preoperatively to a mean of 0.26 +/- 0.11 logMAR postoperatively. Visual acuity stayed stable throughout the follow-up period. Conclusions SF6 gas tamponade combined with laser photocoagulation represents simple, effective, minimally invasive treatment option for ODPM without vitreomacular traction. Repeated injection was required in some patients.