Fe-doped olivine and char for in-bed elimination of gasification tars in an air-blown fluidised bed reactor coupled with oxidative hot gas filtration

Gasification experiments were carried out in a pilot scale fluid bed reactor operated under allothermal mode and low fluidisation regime with iron-doped olivine and char as catalyst for in-situ tar abatement.The catalyst combination resulted in a reduction of 50%in the overall tar yield with respect to the reference values.Furthermore,the integration of an oxidative Hot Gas Filtration unit downstream the gasification reactor led to a further reduction in overall tar yield and relatively clean gas was obtained(approx.1 g/Nm3,benzene-free).The tar dew point of the resulting producer gas was estimated to 80℃,only 40℃ above the threshold value recommended for its valorisation in standard internal combustion engines.Moreover,catalyst elutriation and char hold-up took place to a large extent inside the reactor.The analysis of catalyst samples at different Time-On-Stream(TOS)revealed:(i)a considerable loss of iron oxides during the first hour of test because of the interparticle mechanical attrition(mostly surface abrasion)and partial reduction of hematite to magnetite and wustite but,stable composition at higher TOS,(ii)the loss of the iron oxide coverage of Fe/olivine particles and the formation of agglomerates with increasing TOS and,(iii)the amount of carbon deposited in the surface of the Fe/olivine particles increased with TOS,but in any case,these carbon deposits can be completely oxidized above 650℃.

NEW MODEL OF GAS FLOW PROBLEM IN MULTI-LAYERED GAS RESERVOIR AND APPLICATION

In this paper, the new model of the real gas filtration problem has been presented multi-layered gas reservoir, when a gas well output and wellbore storage may be variable, and have obtained the exact solutions of pressure distribution for each reservoir bed under three kinds of typical out-boundary conditions. As a special case, according to the new model have also obtained the qxact solutions of presssure distribution in homogeneous reservoir and is given important application in gas reservoir development.

Recovery of zinc from Zn-Al-Fe alloys by gas pressure filtration

The recovery of zinc from galvanizing dross and the removal of iron contained dross particles by gas pressure filtration were investigated using the model of Zn-Fe-Al alloys.The majority of molten zinc was separated after filtration,and the residue intercepted by the filter consisting mostly of dross particles.The effects of the pressure differential(p),separation temperature(T)and alloy composition on the zinc recovery and iron removal were investigated.At p=0.30 MPa and T=723 K,86.2 wt.%zinc was recovered from the Zn-4Al-2Fe alloy,and up to 99.9 wt.%of the iron was concentrated in the residue.Applying a higher pressure differential led to the improved filtration efficiency,and the desired separation temperature was about 723 K.The aluminum content in the Zn-Al-Fe alloy had little effect on separation efficiency,whereas increasing the iron content led to a decrease in the separation efficiency.Our findings demonstrate the potential of the gas pressure filtration method for the recovery of zinc from galvanizing dross.

Effect of Gas Bubbling Filtration Treatment on Microporosity Variation in A356 Aluminium Alloy

In the present study, the contribution of the gas bubbling filtration （GBF） process to the microporosity variation, microstructural characteristics and tensile properties of A356 aluminium alloy was investigated. The test specimens were fabricated through gravity casting in terms of the process variables： the degassing time, the impeller rotation and the aperture size of gas inlet hole. The density measurement and scanning electron microscope fractography analyses were conducted to evaluate the variation of the volumetric porosity and fractographic porosity with the GBF process, respec- tively. The fractographic porosity of the specimens can be minimised under specific GBF conditions in terms of the buoyant velocity and the absorbing capacity of gas bubbles, the inclusion of oxide films, whereas the volumetric porosity can be wholly reduced on the lapse of degassing time. The ultimate tensile strength （UTS） and elongation at optimal conditions were improved to approximately 30 MPa and 1.5% compared with no GBF treatment. Even though an extension of the degassing time and/or excessive stirring action of the melt may induce the inclusion of bifilm oxides and the increase of fractographic porosity, the tensile properties of over-treated specimens were maintained to a level which is similar to those that did not undergo GBF treatment due to the grain refinement accompanying with the GBF process. In addition, the defect susceptibility of UTS and elongation to microporosity variation could be remarkably improved at an optimal GBF condition.