Optimization of the flue gas-flow controlling devices of the electrostatic precipitator of unit A4 in TPP "Nikola Tesla"

Homogeneity of the flue gas-flow through the chamber of an electrostatic precipitator is one of the basic influencing parameter on dedusting efficiency. This paper presents results of a multiobjective optimization study of the flue gas controlling devices of electrostatic precipitator of 324 MWe lignite fired Unit A4 of TPP "Nikola Tesla" in Serbia. The aim was to achieve better flow homogeneity in the cross-section of the precipitator compared to the original design. Additional constraints were to maintain the minimum as possible overall weight of the proposed design as well as pressure drop through the precipitator. Numerical simulations based on CFD were used to investigate dependence of the velocity distribution in the ducts and precipitator’s chamber with respect to the geometrical parameters of tested concepts of turning blades. A series of 22 detailed full-scale numerical models of the precipitator with different concepts of turning vanes designs were developed. Assessment of the flow field uniformity for each tested design was performed based on the analysis of several homogeneity parameters calculated for selected vertical cross-sections of the precipitator. After the reconstruction according to optimized design, results of measurements confirmed significant improvements of the velocity distribution in the vertical cross-sections of the precipitator, increase of dedusting efficiency and reduction of PM emission

Gas-liquid separation using axial flow cyclones.

Work to improve the oil-gas extraction processes from the wellhead to basic saleable product has been a consistent area of study for over 50 years. In this project, it is aimed to develop high capacity plant to obtain low liquid entrainment levels by separating oil droplets from the dispensed gas. Commonly used gas cleaning equipment has disadvantages that inhibit its use in separating oil droplets from gas including excess bulk, too low gas handling capacities, poor separation efficiencies and the need for sophisticated maintenance. The objective of this research is to focus on one of the more recent manifestations of a basic separation technology, the axial flow gas cyclone incorporating drainage slots in the barrel. The work enables quantitative understanding of the performance of the axial flow cyclone separating liquid droplets as an aid to intensifying oil and gas extraction processes. Experimental work was carried out to obtain the pressure drop - flowrate characteristics, data on the onset of re-entrainment and the droplet separation efficiency of the cyclone tested. Modelling work was also carried out using Computational Fluid Dynamics (CFD) and published analytical models to investigate the feasibility of modelling the pressure drop - flowrate characteristics and the grade efficiency of the tested cyclone. The methodologies to integrate individual tubes into a separating vessel and cyclone optimisation have also been covered. It was noticed that with the centre body swirler as the swirling device, a frothing zone occurred at low air flowrates. With the occurrence of this zone, re-entrainment was bound to occur. This was the deficiency of this sort of inlet design because the airflow was not strong enough to swirl the liquid. Instead it was only enough to prevent the liquid from falling backwards and this increased the system pressure drop significantly. Therefore, tangentially oriented inlet swirl vanes with four of the slots used as additional drainage was employed. The frothing zone was then eliminated at low air flowrates. However, at very high air flowrates re-entrainment still occurred which was due to a liquid creeping mechanism and the stripping of liquid film on the cyclone wall. CFD and the other analytical models were able to predict the cyclone’s pressure drop - flowrate characteristics well, however, the agreement of the grade efficiency curves with the experimental data was poor. Comparison of the developed axial flow cyclones with the commercially available cyclone indicated that the Sheffield design performs better in terms of droplet separation efficiency, but at the expense of pressure drop

Combustion 2000

This report is a presentation of work carried out on Phase II of the HIPPS program under DOE contract DE-AC22-95PC95144 from June 1995 to March 2001. The objective of this report is to emphasize the results and achievements of the program and not to archive every detail of the past six years of effort. These details are already available in the twenty-two quarterly reports previously submitted to DOE and in the final report from Phase I. The report is divided into three major foci, indicative of the three operational groupings of the program as it evolved, was restructured, or overtaken by events. In each of these areas, the results exceeded DOE goals and expectations. HIPPS Systems and Cycles (including thermodynamic cycles, power cycle alternatives, baseline plant costs and new opportunities) HITAF Components and Designs (including design of heat exchangers, materials, ash management and combustor design) Testing Program for Radiative and Convective Air Heaters (including the design and construction of the test furnace and the results of the tests) There are several topics that were part of the original program but whose importance was diminished when the contract was significantly modified. The elimination of the subsystem testing and the Phase III demonstration lessened the relevance of subtasks related to these efforts. For example, the cross flow mixing study, the CFD modeling of the convective air heater and the power island analysis are important to a commercial plant design but not to the R&D product contained in this report. These topics are of course, discussed in the quarterly reports under this contract. The DOE goal for the High Performance Power Plant System ( HIPPS ) is high thermodynamic efficiency and significantly reduced emissions. Specifically, the goal is a 300 MWe plant with > 47% (HHV) overall efficiency and {le} 0.1 NSPS emissions. This plant must fire at least 65% coal with the balance being made up by a premium fuel such as natural gas. To achieve these objectives requires a change from complete reliance of coal-fired systems on steam turbines (Rankine cycles) and moving forward to a combined cycle utilizing gas turbines (Brayton cycles) which offer the possibility of significantly greater efficiency. This is because gas turbine cycles operate at temperatures well beyond current steam cycles, allowing the working fluid (air) temperature to more closely approach that of the major energy source, the combustion of coal. In fact, a good figure of merit for a HIPPS design is just how much of the enthalpy from coal combustion is used by the gas turbine. The efficiency of a power cycle varies directly with the temperature of the working fluid and for contemporary gas turbines the optimal turbine inlet temperature is in the range of 2300-2500 F (1260-1371 C). These temperatures are beyond the working range of currently available alloys and are also in the range of the ash fusion temperature of most coals. These two sets of physical properties combine to produce the major engineering challenges for a HIPPS design. The UTRC team developed a design hierarchy to impose more rigor in our approach. Once the size of the plant had been determined by the choice of gas turbine and the matching steam turbine, the design process of the High Temperature Advanced Furnace (HITAF) moved ineluctably to a down-fired, slagging configuration. This design was based on two air heaters: one a high temperature slagging Radiative Air Heater (RAH) and a lower temperature, dry ash Convective Air Heater (CAH). The specific details of the air heaters are arrived at by an iterative sequence in the following order:-Starting from the overall Cycle requirements which set the limits for the combustion and heat transfer analysis-The available enthalpy determined the range of materials, ceramics or alloys, which could tolerate the temperatures-Structural Analysis of the designs proved to be the major limitation-Finally the commercialization issues of fabrication and reliability, availability and maintenance. The program that has sought to develop and implement these HIPPS designs is outlined below

Development and Application of Optimal Design Capability for Coal Gasification Systems

The basic objective of this research is to develop a model to simulate the performance and cost of oxyfuel combustion systems to capture CO{sub 2} at fossil-fuel based power plants. The research also aims at identifying the key parameters that define the performance and costs of these systems, and to characterize the uncertainties and variability associated with key parameters. The final objective is to integrate the oxyfuel model into the existing IECM-CS modeling framework so as to have an analytical tool to compare various carbon management options on a consistent basis