Effect of air-preheating on NOx emissions from a gas turbine combustor

A 76 mm diameter can combustor equipped with a 45° curved-blade radial swirler was used to study the effect of high inlet temperature gas turbine combustion on NOx emission characteristics. High inlet temperature combustion was simulated using preheat air at 400°K, 600°K, 740°K and 900°K. Natural gas was investigated using passage injection technique. It was demonstrated that increasing the inlet air temperature significantly widened the weak extinction limit and improved the NOx emission characteristics. An optimum NOx emission of less than 4.5 ppm at 15% oxygen, compatible with 99% efficiency was demonstrated at 900K inlet temperature. It was also demonstrated that with high inlet temperature operation lean well-mixed combustion required for an adequate control of NOx emissions could be achieved. The major conclusion reached is that high inlet temperature combustion could be a promising approach for low NOx emissions with high combustion efficiency and good flame stability

Simulation Studies of Gas-Solid in the Riser of a Circulating Fluidized Bed

A numerical parametric study was performed on the influence of various riser exit geometries on the hydrodynamics of gas-solid two-phase flow in the riser of a Circulating Fluidized Bed (CFB). A Eulerian continuum formulation was applied to both phases. A two fluid framework has been used to simulate fully developed gas-solid flows in vertical riser. A two dimensional Computational Fluid Dynamics (CFD) model of gas-particle flow in the CFB has been investigated using the code FLUENT. The turbulence was modeled by a k-e turbulence model in the gas phase. The simulations were done using the geometrical configuration of a CFB test rig at the Universiti Teknologi Malaysia (UTM). The CFB riser column has 265 mm (width), 72 mm (depth) and 2.7 m height. The riser is made up of interchangeable Plexiglas columns. The computational model was used to simulate the riser over a wide range of operating and design parameters. In addition, several numerical experiments were carried out to understand the influence of riser end effects, particle size, gas solid velocity and solid volume fraction on the simulated flow characteristics. The CFD model with a k-e turbulence model for the gas phase and a fixed particle viscosity in the solids phase showed good mixing behaviour. These results were found to be useful in further development of modeling of gas solid flow in the riser

Development of low liquid fuel Burnera

Recently, most of the gas turbine combustion research and development involves in lowering the emissions emitted from the combustor. Emission causes adverse affect to the world and mankind especially. Main concern of the present work is to reduce the NOx emission since the CO emission could be reduced through homogeneous mixing of fuel and air. Homogeneous mixing of fuel and air is also needed in order to reduce NOx emission. A liquid fuel burner system with radial air swirler vane angle of 30o, 40o, 50o and 60o has been investigated using 163mm inside diameter combustor. Orifice plates with three different sizes of 20mm, 25mm and 30mm were inserted at the back plate of swirler outlet. All tests were conducted using diesel as fuel. Fuel was injected at two different positions, i.e. at upstream and downstream of the swirler outlet using central fuel injector with single fuel nozzle pointing axially outwards. Experiment has been carried out to compare the three emissions NOx, CO and SO2. NOx reduction of about 53 percent was achieved for orifice plate of 20mm with downstream injection compared to orifice plate of 20mm with upstream injection. CO2 and SO2 was reduced about 26 percent and 56 percent respectively for the same configuration. This comparison was taken using swirler vane angle of 60o. The overall study shows that larger swirler vane angle produces lower emission results compared to the smaller ones. Smaller orifice plates produce better emission reduction. Meanwhile, downstream injection position significantly decreases the emission levels compared to upstream injection position. Combination of smallest orifice plate and largest swirler vane angle with downstream injection produce widest and shortest flame length

Characteristic properties of ceramic membrane derived from fly ash with different loadings and sintering temperature

Nowadays, ceramic membrane developed from wastes has gained attention, especially towards water separation applications. With abundant and high silica content of fly ash, low cost ceramic membrane was successfully prepared via phase inversion and sintering technique. Prior to both phase inversion and sintering process, ceramic suspension was prepared at different loadings, ranging from 40wt% to 50 wt% fly ash and subsequently sintered at temperature ranging from 1150°C to 1350°C. By varying fly ash content and sintering temperature, the morphology, mechanical strength and phase transformation characteristics of the prepared membrane were affected. The characterisation of prepared membrane were investigated by using scanning electron microscopy, three-point bending test, and X-ray diffraction (XRD). The mechanical strength of the membrane increased with increasing fly ash loading (up to 45 %), however too much fly ash loading resulted in decrease of its mechanical strength probably due the presence of unburnt at higher fly ash contents. This unburnt carbon contributed to the vacant space during sintering process and had the tendency to increase formation of pores, simultaneously reduced its mechanical strength. In addition, the SEM results also illustrated a cross-sectional image of the membrane which had become more elastic with increasing fly ash loading and denser as sintering temperature gradually increased. In addition, increasing the fly ash loading likely discouraged the formation of desired finger-like structure. The XRD results however showed continuous presence of mullite with the increasing sintering temperature which contributed higher mechanical strength. The preliminary performance tests indicated that the optimum conditions to produce hollow fibre ceramic membrane from fly ash were at 45 wt % fly ash loading sintered at 1350°C and has a pure water flux of 131 L/m2h

Fabrication and Characterization of Polyimide-CNTs Hybrid Membrane to Enhance High Performance CO2 Separation

This study investigates the CO2 separation performance of a hybrid membranes flat sheet based on polyimide incorporated with carbon nanotubes (CNTs) particles. CNTs was selected and its loading were a 1 wt% in total solid. The hybrid composite membranes were fabricated in order to increase their separation performance for the gaseous mixture of CO2 and CH4. Hybrid Composite membrane incorporated carbon nanotubes were mannufactured by the dry-wet phase inversion technique using flat sheet membrane casting machine system, in which the CNTs were embedded into the polyimide membrane and the resulting membranes were characterized. The results from the FESEM, DSC and FTIR analysis confirmed that chemical modification on carbon nanotubes surface had taken place. Sieve-in-a-cage\u27 morphology observed shows the poor adhesion between polymer and unmodified CNT. The results revealed that the good multi-wall carbon nanotubes dispersion leads to enhanced gas permeation properties. It is also concluded that addition of carbon nanotubes particles into the matrix of Polyimide polymer has significant effect on the membrane structure and properties

Improving boiler operation without additional capital investment

Boiler is the most widely - used combustion equipment as a steam generator in most of the energy intensive industries in Malaysia. As the cost of generating energy steadily increases, there is a need to operate a boiler properly so that the maximum amount of energy could be generated. In addition to that, less harmful polluting species discharged from the boiler could be achieved as nowadays there is an increasing concern of the environment degradation due to the inefficient operation of the combustion equipment. This paper gives a brief review on the simple and yet important practices that can be used to optimize the efficiency of the boiler performance without additional capital investment

Investigation of temperature profile for liquefied petroleum gas storage operations

The investigation of temperature profile of liquefied petroleum gas during discharging process as the initial step in a usage management of LPG, which is an essential part to evaluate the left over problem. Experiments have been conducted to predict the evaporation behavior of LPG in portable cylinder with 50k water capacity. In a parallel effort, a computer model has been developed based on the unsteady state of heat transfer concepts using MATCAB 2000 to simulate the evaporation process in the LPG portable cylinder under various conditions taking account such as discharging flow rate and surrounding temperatures. The objective of this paper is a description of the LPG evaporation process and performance of calculation model to investigate the temperature profile. A rather good agreement between the theoretical and experimental data was obtained

The effect of surrounding temperature on liquefied petroleum gas behaviour during exhaustion process

Liquefied petroleum gas (LPG) is considered to be a cleaner fuel because it has less impact on air quality. However, the potential benefit of LPG usage in domestic or residential sectors in Malaysia is hampered by LPG residue in cylinder. A few critical factors, such as LPG composition, exhaustion rate and surrounding temperature, have been identified to significantly contribute to the LPG residue problem. The present study will only report the effect of surrounding temperature on the behaviour of LPG inside the storage cylinder during exhaustion process. The investigation was experimentally carried out at the surrounding temperature of 10°C to 35°C. The results show that LPG exhaustion operation at the surrounding temperature of 25°C or higher exhibited significant temperature and pressure profiles which explained a considerable reduction of the LPG residue. Radial and axial thermal distribution analysis inside the cylinder indicates that sensible heat needed for evaporation process was derived mainly in the axial direction at the regions adjacent to the internal wall

Isothermal Modeling Study Of Concentration Fluctuations In Multi-Jet Turbulent Mixing

Water analogy flow visualisation and conductivity techniques with air bubbles and a salt solution as tracers are relatively simple and cost-effective techniques for the qualitative and quantitative studies of turbulent fuel and air mixing and yet give very useful information about aerodynamic patterns and mixing characteristics of the system concerned. These techniques have been used to study the fuel placement effects on the flow aerodynamics and mixing characteristics of a series of multi-jet grid cone stabilised non-swirl flow. The experimental results showed that the degree of fuel and air mixing was largely governed by the internally-generated flow aerodynamics and the turbulent energy available. The methods of direct-fuel- injection had a major influence on the mixing uniformity only in the high turbulence jet interaction zone near the cone exit plan