Influence of air-staging on the concentration profiles of NH3 and HCN in the combustion chamber of a CFB boiler burning coal

The characterisation of the concentration profiles of NH3 and HCN are of great importance for increasing the knowledge of the formation and destruction pathways of NO and N2O in a fluidized bed boiler. Further improvements of the sampling methods for the determination of both NH3 and HCN in the combustion chamber in full-scale CFB boilers are also needed. A gas-sampling probe connected to a Fourier Transform Infra Red (FTIR) instrument and a gas-quenching (GQ) probe in which the sample is quenched directly in the probe tip by a circulating trapper solution were used. The FTIR technique is based on analysis of hot combustion gases, whereas the trapper solutions from the GQ probe were analysed by means of wet chemistry. The tests were performed during coal combustion in a 12 MW CFB boiler, which was operated at three air-staging cases with the addition of limestone for sulphur capture. The concentration profiles of NH3 and HCN in the combustion chamber showed a different pattern concerning the influence of air-staging. The highest levels of NH3 were observed during reducing conditions (severe air-staging), and the lowest were found under oxidising conditions (no air-staging). The levels of HCN were much lower than those measured for NH3. The highest levels of HCN were observed for reversed air-staging and severe air-staging showed almost no HCN. The potential reactions involving NH3 and HCN in the combustion chamber as well as the potential measurement errors in each sampling technique are discussed for the three air-staging cases

Qubitless Quantum Logic

We discuss the implementation of quantum logic in a system of strongly interacting particles. The implementation is qubitless since ``logical qubits'' don't correspond to any physical two-state subsystems. As an illustration, we present the results of simulations of the quantum controlled-NOT gate and Shor's algorithm for a chain of spin-1/2 particles with Heisenberg coupling. Our proposal extends the current theory of quantum information processing to include systems with permanent strong coupling between the two-state subsystems.Comment: 2 figures. Corrected titl

The effect of oxygen and volatile combustibles on the sulphation of gaseous KCl

Sulphur/sulphate containing additives, such as elemental sulphur (S) and ammonium sulphate (NH4)(2)SO4), can be used for sulphation of KCl during biomass combustion. These additives convert KCl to an alkali sulphate and a more efficient sulphation is normally achieved for ammonium sulphate compared to sulphur. The presence of SO3 is thus of greater importance than that of SO2. Oxygen and volatile combustibles could also have an effect on the sulphation of gaseous KCl. This paper is based on results obtained during co-combustion of wood chips and straw pellets in a 12 MW circulating fluidised bed (CFB) boiler. Ammonium sulphate was injected at three positions in the boiler i.e. in the upper part of the combustion chamber, in the cyclone inlet, and in the cyclone. The sulphation of KCl was investigated at three air excess ratios (lambda = 1.1, 1.2 and 1.4). Several measurement tools were applied including IACM (on-line measurements of gaseous alkali chlorides), deposit probes (chemical composition in deposits collected) and gas analysis. The position for injection of ammonium sulphate had a great impact on the sulphation efficiency for gaseous KCl at the different air excess ratios. There was also an effect of oxygen on the sulphation efficiency when injecting ammonium sulphate in the cyclone. Less gaseous KCl was reduced during air excess ratio lambda = 1.1 compared to the higher air excess ratios. The optimal position and conditions for injection of ammonium sulphate were identified by measuring KCl with IACM. A correlation was observed between the sulphation of gaseous KCl and reduced chlorine content in the deposits. The experimental observations were evaluated using a detailed reaction mechanism. It was used to model the effect of volatile combustibles on the sulphation of gaseous MCI by SO3. The calculations supported the proposition that the presence of combustibles at the position of SO3 injection (i.e. AS) causes reduction of SO3 to SO2

Friction and wear studies of some PEEK materials

The friction and wear behavior of several types of PEEK polymers and composites were studied. The influence of carbon fiber, lubricant and thermally conductive fillers were evaluated, as well as the effects of contact load and temperature.  The tests were done using a reciprocating ball-on-disc set-up. The materials were tested under the load of 5 N and 15 N, at room temperature, 80°C, 120°C and 150°C. The difference between the materials was substantial, with a friction coefficient varying between 0.03 and 0.3 for the different materials at 120°C. PEEK with carbon fiber filler showed an improvement in both friction and wear compared to unfilled PEEK. When adding lubricant, PTFE, to the composite the friction and wear were improved even more. PEEK with thermally conductive filler on the other hand had both highest friction and wear. Increasing the temperature slightly decreased both friction and wear for most of the PEEK materials. At 150°C, only the composite with PTFE lubricant had a low friction and wear