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Abstract: The air separation unit (ASU) plays a key role in improving the efficiency, availability, and operability of an oxygen-fed integrated gasification combined cycle (IGCC) power plant. An optimal integration between the ASU and the balance of the plant, especially the gasifier and the gas turbine (GT), has significant potential for enhancing the overall plant efficiency. Considering the higher operating pressure of the GT, an elevated-pressure air separation unit (EP-ASU) is usually favored instead of the conventional low-pressure air separation units (LP-ASU). In addition, a pumped liquid oxygen (PLOX) cycle is usually chosen if the operating pressure of the gasifier is high. A PLOX cycle helps to improve plant safety and availability and to decrease the capital cost by reducing the size of the oxygen compressor or by eliminating it completely. However, the refrigeration lost in withdrawn liquid oxygen must be efficiently recovered. This paper considers five different configurations of an ASU with PLOX cycle and compares their power consumptions with an EP-ASU with a traditional gaseous oxygen (GOX) cycle. The study shows that an optimally designed EP-ASU with a PLOX cycle can have similar power consumption to that of an EP-ASU with GOX cycle in the case of 100% nitrogen integration. In the case of an IGCC with pre-combustion CO2 capture, the lower heating value (LHV) of the shifted syngas, both on a mass and volumetric basis, is in between the LHV of the unshifted syngas from an IGCC plant and the LHV of natural gas, for which the GTs are generally designed. The optimal air integration in the case of a shifted syngas is found to be much lower than that of an unshifted syngas. This paper concurs with the existing literature that the optimal integration occurs when air extracted from the GT can be replaced with the nitrogen from the ASU without exceeding mass/volumetric flow limitations of the GT. Considering nitrogen and air integration between the ASU and the GT, this paper compares the power savings in an LP-ASU with a PLOX cycle to the power savings in an EP-ASU with GOX cycle and EP-ASU with PLOX cycle. The results show that an LP-ASU with a PLOX cycle has less power consumption if the nitrogen integration levels are less than 50–60%. In addition, a study is carried out by varying the concentration of nitrogen and steam in the fuel diluents to the GT while the NOx level was maintained constant. The study shows that when the nitrogen injection rate exceeds 50%, an EP-ASU with a PLOX cycle is a better option than an LP-ASU with a PLOX cycle. This paper shows that an optimal design and integration of an ASU with the balance of the plant can help to increase the net power generation from an IGCC plant with CO2 capture. [Copyright &y& Elsevier]

Abstract: Simultaneous combustion of biomass (wood or straw) with coal represents an alternative energy source with economic potential and smaller pollutant emission. Under the current environmental legislation, biomass is seen as a zero emitter of carbon dioxide emissions. The paper analyses the potential corrosion and the formation of adherent deposits in the coal–biomass co-combustion process at two pilot installations. Three types of experiments with a mixture of coal, straw and wood are conducted. For the slagging phenomena, two installations pilot (grate-fired furnace) were used: one of 55kW thermal power and other of 2MW. As a control sample, different types of steels were used. The results can lead to the implementation of measures to reduce the effects of corrosion. The final aim is to increase the boilers efficiency and life duration. Furthermore, the ash analyses allow their use as fertilizer in agriculture. [Copyright &y& Elsevier]

Abstract: One of the main advantages of biodiesel fuels is that almost eliminate carbon dioxide emissions based on the CO2 consumption during plant growth. However it is accepted for most researchers that when burned in diesel engines there is an increase of the NOx emissions when these are compared to the NOx emissions produced by mineral diesel fuel. HCCI with diesel fuel is being considered as an alternative combustion process in the internal combustion engine, mainly because of the huge potential for simultaneous reduction of NOx and soot emissions while fuel conversion efficiency is not compromised, in fact, it is usually increased. The HCCI combustion process can accept a variety of fuel types, like biodiesel and mixtures with mineral diesel fuel. The main reason for burning biodiesel fuel in HCCI combustion mode is that it enables the simultaneous reduction of NOx and soot emissions to current standard requirements, as well as the elimination of CO2. This paper shows a methodology for HCCI combustion mode of biodiesel mixtures based on a high swirl ratio and EGR rate combined with late injection where HRR, NOx, CO, HC and soot emissions have been analyzed. This strategy has reduced fuel wall impingement encountered when early injection is used. Bowl in piston geometry has been designed with a dedicated swirling flow model and a NOx emission of biodiesel fuel has been reduced. [Copyright &y& Elsevier]