Exhaust Gas Boiler Research Articles

Modeling and Performance Analysis of Combined-Cycle Based Ship Power Plant

For combined-cycle power plant performance analysis, a ship power plant mathematical model is developed, including diesel engine, controllable pitch propeller, exhaust gas boiler, turbine generator and shaft generator models. The simulation performance characteristic curves of diesel engine under various loads are given. Comparison of simulation results and experimental data shows the model can well predict the performance of diesel engine in various operating conditions. The specific fuel oil consumption contours of combined-cycle power plant and the relations between engine operating conditions and steam cycle parameters are given. The influence of diesel engine operating conditions to the overall performance of combined-cycle power plant is discussed.

Optimization of the Heat Exchangers of a Thermoelectric Generation System

The thermal resistances of the heat exchangers have a strong influence on the electric power produced by a thermoelectric generator. In this work, the heat exchangers of a thermoelectric generator have been optimized in order to maximize the electric power generated. This thermoelectric generator harnesses heat from the exhaust gas of a domestic gas boiler. Statistical design of experiments was used to assess the influence of five factors on both the electric power generated and the pressure drop in the chimney: height of the generator, number of modules per meter of generator height, length of the fins of the hot-side heat exchanger (HSHE), length of the gap between fins of the HSHE, and base thickness of the HSHE. The electric power has been calculated using a computational model, whereas Fluent computational fluid dynamics (CFD) has been used to obtain the thermal resistances of the heat exchangers and the pressure drop. Finally, the thermoelectric generator has been optimized, taking into account the restrictions on the pressure drop.

Removal of Fine Particulate Matter (PM) from Boiler Exhaust Gas in Electrostatic Water Spraying Scrubber

Removal of Fine Particulate Matter (PM) from Boiler Exhaust Gas in Electrostatic Water Spraying Scrubber

Ageing mechanisms on PdO x-based catalysts for natural gas combustion in premixed burners

The ageing effect induced by S-compounds over 2%Pd/CeO 2·2ZrO 2, 2%Pd/LaMnO 3·2ZrO 2 and 2%Pd/BaCeO 3·2ZrO 2 catalysts for CH 4 combustion was investigated; S-compounds are in fact added as odorants in the natural gas network for safety purposes. Pd-based catalysts were prepared by solution combustion synthesis (SCS), starting from metal nitrates/glycine mixtures. Basic characterization (XRD, BET, FESEM analysis), FT–IR studies and catalytic activity tests were performed on powders and after accelerated ageing carried out up to 2 weeks (hydro-thermal treatment at 900 °C under a flow rate with typical domestic boiler exhaust gas composition, 9% CO 2, 18% H 2O, 2% O 2 in N 2, containing also 200 ppmv of SO 2 to emphasize any poisoning effect). Over fresh catalysts, IR analysis of CO adsorption evidenced the formation of highly dispersed Pd metal clusters and Pd ions. With ageing, 2%Pd/CeO 2·2ZrO 2 increased its CH 4 combustion half-conversion temperature ( T 50, regarded as an index of catalytic activity) from 382 °C—recorded for fresh sample—to 421 °C, attained with the same sample aged two weeks. An unexpected improvement was found instead in the overall performance of 2%Pd/LaMnO 3·2ZrO 2 and 2%Pd/BaCeO 3·2ZrO 2: the T 50 in fact lowered from 570 to 450 °C for the first one, and from 512 to 443 °C for the second one, after two weeks ageing. S-hydro-thermal treatment provoked bulk and surface sulfates formation on all aged samples, with a concentration increasing with the exposure time. Prevailing ageing mechanisms seemed to be Pd metallic clusters coalescence, detected over the Ce–Zr system, and surface-bulk sulfates formation, the latter destroying the initial crystallographic structure. In 2%Pd/LaMnO 3·ZrO 2 and 2%Pd/BaCeO 3·ZrO 2 powders the amount of the perovskite phase strongly decreased during ageing, in favor of the formation of bulk sulfate and of oxides.

Evaluation of dual-bed pressure swing adsorption for CO2 recovery from boiler exhaust gas

Abstract Dual-bed CO2 adsorption using zeolite was studied experimentally and theoretically. Boiler exhaust gas (13 vol% CO2, 79 vol% N2 and 8 vol% O2) was used as a feed gas for the eight-step four-bed PSA process. Na-X type zeolite (NaX) and Na-A type zeolite (NaA) were selected in the break-through test. NaX has higher CO2 adsorption capacity than other adsorbents. NaA has the highest selectivity among all adsorbents tested. In the simulations, a NaX-to-NaA ratio affected the recovery efficiency and the concentration of recovery gas. Moreover, in the dual-bed PSA process of NaX-to-NaA ratio=2/1, the recovery efficiency and CO2 concentration of recovery gas were higher than those in a single-adsorbent PSA process. Simulated results by the dynamic model agreed well with the PSA experimental results.

A Study on the Heat Recovery from Boiler Exhaust Gas with Multi-stage Water-fluidized-bed Heat Exchanger

Heat recovery from boiler exhaust gas with multi-stage water-fluidized-bed heat exchanger is analyzed in this study. The recovered energy here is not only sensible heat but also latent heat contained in the exhaust gas. In this system direct contact heat transfer occurs while exhaust gas passes through water bed and the thermal energy recovered this way is again delivered to the water circulating through heat exchanging pipes within the bed. Thus the thermal energy of exhaust gas can be recovered as a clean hot water. A computer program developed in this study can predict the heat transfer performance of the system. The results of experiments performed in this study agree well with the calculated ones. The heat and mass transfer coefficients can be fecund through these experiments. The performance increases as the number of stage increases. However at large number of stages the increasing rate becomes very low.

Operation optimization of an industrial cogeneration system by a genetic algorithm

Large process plants need energy in several forms (mechanical energy, electricity, steam, hot water etc.), which very often come from a variety of sources such as gas-turbine generators, steam-turbine generators, exhaust gas boilers, fuel-burning boilers etc. In addition, the utility network serves as a source of supplementary electricity if needed, or as a sink when excess electricity is produced. The cost of energy is one of the major contributors to the total operating cost of a process plant. Consequently, minimization of this cost is of utmost importance. Due to the variety of energy sources, the interdependency between sources and the variation of technical and economic conditions with time (e.g. change of load, deterioration of equipment, change of fuel and electricity prices etc.), the task of minimizing energy cost is far from trivial. Methods and algorithms to solve these types of problems are still a subject of research because of the following reasons: the problems are usually nonlinear with multimodal objective functions that may contain both discrete (e.g. integer) and continuous variables. No single method has been successful with every problem of this type. In the present work, a genetic algorithm (GA) is applied for the operation optimization of a cogeneration system, which supplies a process plant with electricity and steam at various pressure levels. A mathematical simulation model of the system has been developed, taking into consideration the real condition of main equipment, as it is revealed by an appropriate set of measurements. The GA is combined with the simulation model, in order to solve the optimization problem under specified constraints.

Analysis of the flame formed during oxidation of pulverized coal by an O 2CO 2 mixture

Pulverized coal combustion with oxygen and recycled flue gas constitutes a promising system to recover CO 2 from the exhaust gases of boilers. Our previous combustion tests on this system suggest emissions of smaller amounts of NO x than in conventional combustion and reduced ignition stability of the burner. In order to improve the combustibility of the O 2/CO 2-pulverized-coal burner, numerical simulations and combustion tests were performed. An oxygen-injection nozzle was added to the burner. Simulation results predicted the effectiveness of direct oxygen injection and were confirmed qualitatively by bench-scale combustion tests on gas temperatures.

Thermoeconomic operation optimization of the Hellenic Aspropyrgos Refinery combined-cycle cogeneration system

Abstract Hellenic Aspropyrgos Refinery (HAR) is a state-owned petroleum refinery with a capacity of 130,000 barrels per day. The electric and part of the thermal loads of HAR are covered by a combined-cycle cogeneration plant of 54 MWe capacity, which is interconnected with the utility grid. The plant consists of two gas-turbine generators, two exhaust-gas boilers, four fuel-oil boilers and one steam-turbine generator. Steam is produced at four levels; high, medium, low and very low pressure. Low-sulphur fuel oil is burned in the boilers, while the gas turbines can operate in any one or in a combination of (a) diesel oil, (b) process-generated fuel gas. (c) a mixture of propane and propylene (LPG). Connection to the utility network allows for importing additional electricity, if there is need, or for exporting excess electricity. Due to the variety of sources which can be used to cover the loads, the interdependency between sources and the variation of technical and economic conditions with time, questions such as the following arise. Given the technical (e.g. needs in electricity and heat), environmental and economic conditions at any instant of time, what source and at what load should be used? Which is the quantity of electricity bought from or sold to the utility grid? In order to answer these questions, an optimization procedure has been developed which is supported by a thermoeconomic analysis of the system and modelling of the performance of the main components. The minimization of the operation expenses has been selected as the objective function. A computer program has been developed for the numerical solution of the optimization problem. In the present work, the optimization procedure and the computer program are described, numerical results are presented which show the importance of applying such a procedure to real-world complex systems, a sensitivity analysis with respect to important parameters is performed and conclusions are drawn regarding the usefulness and further improvements of the program.

95/00944 Separation system of CO2 from boiler exhaust gas

95/00944 Separation system of CO2 from boiler exhaust gas

Application of the thermoeconomic functional approach to the CGAM problem

A gas-turbine cogeneration system with a regenerative air preheater and a single-pressure exhaust gas boiler serves as an example for application of three different analysis and optimization procedures: 1. (i) direct use of a nonlinear programming algorithm, 2. (ii) thermoeconomic functional approach, and 3. (iii) modular simulation and optimization of the system. The results obtained with the three methods are compared with each other. The sensitivity of the optimal solution to certain parameters and of the objective function to the independent variables is studied. Conclusions are drawn regarding the applicability of each procedure to more complicated optimization problems.

Two case studies of cogeneration systems design and economic feasibility

Cogeneration is an ideal method of power production for applications which require both heat and power simultaneously, hence the name combined heat power (CHP). In this paper, design studies of cogeneration systems for two specific applications are presented. The results indicate the economic feasibility of such installations and how much energy can be saved, especially if the system is analysed on a long-term basis. It is shown that an essential requirement for cogeneration is the proper matching of power and heat demands. The first design study is of a combined power and heating system for a small suburban hospital which requires both steam and power for its various needs. The cogeneration system which was designed for this application consisted of a conventional turbo-charged spark ignition engine with heat exchange from its exhaust and engine cooling systems, coupled with an existing boiler. When the cogeneration system is inadequate to meet the electricity demands, the excess power would be bought from the grid supply. For an initial outlay of approximately $250,000 (1990 prices), an annual saving of $140,000 was conservatively predicted, with an internal rate of return of some 40% over 15 yr. The second design study is for the energy system of a large sugar confectionery factory with power and heat requirements, mainly for lighting, air conditioning and several manufacturing processes. The hardware which was chosenfor the cogeneration system for this case comprises a diesel engine converted for use with natural gas connected to a vertical shell and tube exhaust gas boiler. For an initial investment of approximately $700,000, an annual saving of about $130,000 (1991 prices) is predicted for a 10–15 yr project. The savings and the payback period depend on the electricity buy-back tariffs and the company's plans for future expansion.

Creating an indoor environmental problem from a nonproblem: a need for cautious evaluation of antibodies against hapten-protein complexes.

An epidemic of illness in three schools in New York State occurred in early 1983. An epidemiological review of the problem led to the conclusion that some of the symptoms could have been explained by irritant reactions to boiler exhaust gases but that a major factor was likely public concern about environmental contamination and heightened awareness of common minor symptoms and of exacerbations of chronic illnesses. Diphenylmethane diisocyanate (MDI) from polyurethane insulation had previously been suspected as a potential cause. An earlier investigation had found low levels of anti MDI-human serum albumin in a small number of subjects who did not have typical symptoms of identified MDI or other hypersensitivity syndromes. Similar antibodies were found in two of nine unaffected children in Chicago, who served as a comparison group. The identification of these antibodies, however, was inappropriately used to support the idea of a school contaminated with MDI in spite of the absence of detectable MDI in the environment. The availability of highly sensitive immunoassays should not be inappropriately used to accelerate the fear of environmental toxins when there is no clinical correlation.

Operating Results of Exhaust Gas Desulfurization Plant at Nippon Kokan's Fertilizer Division (Koyasu Works)

Exhaust gas from the Lurgi type contact sulfuric acid plant is treated by a desulfurizing plant based on the lime-qygsum process in the Koyasu Works, Fertilizer Division, Nippon, Kokan. The exhaust gas, discharged in an amount of approximately 60, 000 Nm3/hr contains sulfur oxides consisting of 2, 000-3, 000 ppm of SO2 and about 400 ppm of SO3, which decreases to less than 300 ppm after treatment. This exhaust gas desulfurizer, installed in July 1964, has an object to convert SO2 absorbed by lime milk into calcium sulfite and to obtain high quality gypsum through air oxidation. Initial difficulties in operation caused by the trouble in treating slurry were solved by the modifications and improvements made in the plant and the operating practices, and in January 1966, the plant was successfully brought into continuous operation under stable conditions. Further improvements in facilities and automation have been made in an attempt to save labor.With a view to developing the exhaust gas desulfurization process applicable to ordinary emissions, a pilot plant of 2, 000Nm3/hr based on the use of boiler exhaust gas was constructed in the Koyasu works with reference to the exhaust gas desulfurizing technique and the experience acquired in operating this sulfuric acid plant. Experiments were started in October 1971, and the results permitted establishment of a exhaust gas desulfurizing technique applicable to ordinary exhaust gas.