Tesi sul tema "Heat recovery turbines"

Since the late 19th century, the average temperature on Earth has risen by approximately 1.1 °C because of the increased carbon dioxide (CO2) and other man-made emissions to the atmosphere. The transportation sector is responsible for approximately 33% of the global CO2 emissions and 14% of the overall greenhouse gas emissions. Therefore, increasingly stringent regulations in the European Union require CO2 emissions to be lower than 95 gCO₂/km by 2020. In this regard, improvements in internal combustion engines (ICEs)must be achieved in terms of fuel consumption and CO2 emissions. Given that only up to 35% of fuel energy is converted into mechanical power, the wasted energy can be reused through waste heat recovery (WHR) technologies. Consequently, organic Rankine cycle (ORC) has received significant attention as a WHR technology because of its ability to recover wasted heat in low- to medium-heat sources. The Expansion machine is the key component in ORC systems, and its performance has a direct and significant impact on overall cycle efficiency. However, the thermal efficiencies of ORC systems are typically low due to low working temperatures. Moreover, supersonic conditions at the high pressure ratios are usually encountered in the expander due to the thermal properties of the working fluids selected which are different to water. Therefore, this thesis aims to design an efficient radial-inflow turbine to avoid further efficiency reductions in the overall system. To fulfil this aim, a novel design and optimisation methodology was developed. A design of experiments technique was incorporated in the methodology toexplorethe effects of input parameters on turbine performance and overall size. Importantly, performance prediction modelling by means of 1D mean-line modelling was employed in the proposed methodology to examine the performance of ORC turbines at constant geometries. The proposed methodology was validated by three methods: computational fluid dynamics analysis, experimental work available in the literature, and experimental work in the current project. Owing to the lack of actual experimental works in ORC-ICE applications, a test rig was built around a heavy-duty diesel engine at Brunel University London and tested at partial load conditions due to the requirement for a realistic off-high representation of the performance of the system rather than its best (design) point, while taking into account the limitation of the engine dynamometer employed. Results of the design methodology developed for this projectpresented an efficient single-stage high-pressure ratio radial-inflow turbine with a total to static efficiency of 74.4% and an output power of 13.6 kW.Experimental results showed that the ORC system had a thermal efficiency of 4.3%, and the brake-specific fuel consumption of the engine was reduced by 3%. The novel meanlineoff designcode (MOC) was validated with the experimental works from three turbines. In comparison with the experimental results conducted at Brunel University London, the predicted and measured results were in good agreement with a maximum deviation of 2.8%.

Executive Summary This investigation aimed to assess the true technical and environmental potential, plus economic feasibility of the ORC technology as bottoming cycles for Gas turbines and IC Engines power applications. The assessment started by creating a modeling tool using the software EES in order to model several bottoming cycle configurations and match them with the mentioned power generation technologies. This model used as inputs the operational data of small range (5.5V 50 MW) Siemens Gas Turbines and power plant recommended Wärtsila IC Engines. Thus, adding practical reliability to the model. The simulation also defined 5 control parameters: organic working fluid, operative high pressure of the cycle, minimum temperature difference in the heat exchange, degree of superheating and amount of regeneration. These 5 factors were selected because their role in defining not only the power output, but also the economical cost of an eventual application. Six different organic fluids ranging from Alkanes, Aromates and Siloxanes were analyzed in particular ranges for each of the other 4 mentioned control parameters. After the simulation a preliminary analysis was performed through comparative matrixes. This contrast intended to outstand the configuration with the highest power output and the smallest capital investment cost. Although no costs were inserted in the model, this last factor was analyzed through the cycle’s components size. Three different configurations were selected from this analytic process. The two better preforming cycles and a third option that ideally balanced the two examined factors. Further study quantified the fuel and emission reductions per unit of power when the selected ORCs were implemented and the mild environmental impacts that this additions would have were also quantified. Finally a Cost Benefit Analysis was implemented in which it was reached that although feasible, economically ORC implementation is not more attractive that Business as Usual scenario, implementation of the mentioned equipment without bottoming cycle. This investigation concluded that although ORC implementation could be a major technical improvement for IC Engine and Gas Turbine based power plants, increasing the power output up to 20% and 44% respectively, it suffers from high capital prices due to the novelty of the commercial applications and a lack of balance between output, size and reduction of its production costs. It finalizes by recommending that in order to achieve a more positive situation, a strategy towards a higher economy of scale and increased researched in component cost reduction should be performed.

Thesis (MEng)--Stellenbosch University, 2014.
ENGLISH ABSTRACT: The potential benefits from saving energy have driven most industrial processing facilities to pay more attention to reducing energy wastage. Because the industrial sector is the largest user of electricity in South Africa (37.7% of the generated electricity capacity), the application of waste heat recovery and utilisation (WHR&U) systems in this sector could lead to significant energy savings, a reduction in production costs and an increase in the efficiency of industrial processes. Turbines are critical components of WHR&U systems, and the choice of an efficient and low cost turbine is crucial for their successful implementation. The aim of this thesis project is therefore to validate the use of a turbine for application in a low grade energy WHR&U system. An experimental turbine kit (Infinity Turbine ITmini) was acquired, assembled and tested in a specially designed and built air test bench. The test data was used to characterise the turbine for low temperature (less than 120 Celsius) and pressure (less than 10 bar) conditions. A radial inflow turbine rotor was designed, manufactured and then tested with the same test bench, and its performance characteristics determined. In comparison with the ITmini rotor, the as-designed and manufactured rotor achieved a marginally better performance for the same test pressure ratio range. The as-designed turbine rotor performance characteristics for air were then used to scale the turbine for a refrigerant-123 application. Future work should entail integrating the turbine with a WHR&U system, and experimentally determining the system’s performance characteristics.
AFRIKAANSE OPSOMMING: Die potensiële voordele wat gepaard gaan met energiebesparing het die fokus van industrie laat val op die bekamping van energievermorsing. Die industriële sektor is die grootse verbruiker van elektrisiteit in Suid-Afrika (37.7% van die totale gegenereerde kapasiteit). Energiebesparing in die sektor deur die toepassing van afval-energie-herwinning en benutting (AEH&B) sisteme kan lei tot drastiese vermindering van energievermorsing, ‘n afname in produksie koste en ‘n toename in die doeltreffendheid van industriële prosesse. Turbines is kritiese komponente in AEH&B sisteme en die keuse van ‘n doeltreffende lae koste turbine is noodsaaklik in die suksesvolle implementering van dié sisteme. Die doelwit van hierdie tesisprojek is dus om die toepassing van ‘n turbine in ‘n lae graad energie AEH&B sisteem op die proef te stel. ‘n Eksperimentele turbine stel (“Infinity Turbine ITmini”) is aangeskaf, aanmekaargesit en getoets op ‘n pasgemaakte lugtoetsbank. Die toetsdata is gebruik om die turbine te karakteriseer by lae temperatuur (minder as 120 Celsius) en druk (minder as 10 bar) kondisies. ‘n Radiaalinvloeiturbinerotor is ook ontwerp, vervaardig en getoets op die lugtoetsbank om die rotor se karakteristieke te bepaal. In vergelyking met die ITmini-rotor het die radiaalinvloeiturbinerotor effens beter werkverrigting gelewer by diselfde toetsdruk verhoudings. Die werksverrigtingkarakteristieke met lug as vloeimedium van die radiaalinvloeiturbinerotor is gebruik om die rotor te skaleer vir ‘n R123 verkoelmiddel toepassing. Toekomstige werk sluit in om die turbine met ‘n AEH&B sisteem te integreer en die sisteem se werksverrigtingkarakteristieke te bepaal.

Combined Cycle power plants have recently become a serious alternative for standard coal- and oil-fired power plants because of their high thermal efficiency, environmentally friendly operation, and short time to construct. The combined cycle plant is an integration of the gas turbine and the steam turbine, combining many of the advantages of both thermodynamic cycles using a single fuel. By recovering the heat energy in the gas turbine exhaust and using it to generate steam, the combined cycle leverages the conversion of the fuel energy at a very high efficiency. The heat recovery steam generator forms the backbone of combined cycle plants, providing the link between the gas turbine and the steam turbine. The design of HRSG has historically largely been completed using thermodynamic principles related to the steam path, without much regard to the gas-side of the system. An effort has been made using resources at both UK and Vogt Power International to use computational fluid dynamics (CFD) analysis of the gas-side flow path of the HRSG as an integral tool in the design process. This thesis focuses on how CFD analysis can be used to assess the impact of the gas-side flow on the HRSG performance and identify design modifications to improve the performance. An effort is also made to explore the software capabilities to make the simulation an efficient and accurate.

A number of car engines operate with an efficiency rate of approximately 22% to 25% [1]. The remainder of the energy these engines generate is wasted through heat escape out of the exhaust pipe. There is now an increasing desire to reuse this heat energy, which would improve the overall efficiency of car engines by reducing their consumption of fuel. Another benefit is that such reuse would minimize harmful greenhouse gases that are emitted into the environment. Therefore, the purpose of this project is to examine how the wasted heat energy can be reused and/or recovered by use of a heat recovery system that would store this energy in a hybrid car battery. Green turbines will be analyzed as a possible solution to recycle the lost energy in a way that will also improve the overall automotive energy efficiency.

A combined cycle is one of the thermal cycles used in thermal power plants. It consists of a combination of a gas and a steam turbine, where the waste heat from the gas turbine is used for steam generation in the heat recovery steam generator. The aim of the diploma thesis was the conceptual design of a combined cycle electricity source and the balance calculation of the cycle. The calculation is based on the thermodynamic properties of the substances and the basic knowledge of the Brayton and Rankin-Clausius cycle. The result is the amount and parameters of air, flue gases, and steam/water in individual places and the technological scheme of the source, in which these parameters are listed.

This study examines five potential improvement projects that could be implemented at the Continental Tire manufacturing plant located in Mount Vernon, IL. The study looks at insulating of tire molds, installation of variable frequency drives on circulating pumps, pressure reduction turbines, waste heat utilization used for absorption cooling, and cogeneration using a gas turbine cycle. A feasibility study and cost analysis was performed for each project to determine recommendation for implementation. The two most appealing projects are the insulation addition and the installation of variable frequency drives. Adding insulation would produce energy savings in the range of 908 kJ/s (3,097 Btu/hr) to 989 kJ/s (3,374 Btu/hr) and annual savings between $13,390 and $14,591. Installation of variable frequency drives on two 200 hp circulating pumps would produce energy savings between 74.6 kW (100 hp) and (104.6 kW (140.2 hp) with annual monetary savings in the range of $41,646 to $58,384.

The main goal of my thesis is to carry out thermic calculations for adjusted conditions of electric and heat energy consumption. The power of the generator is 330 MW. In the proposal, you can find combustion trubines type GE 9171E. Steam-gas power plant is designed to combust metallurgical gases. Effort of the thesis focuses also on giving a new informations about trends in combinated production of electric and heat energy.

The main goal of my thesis is to carry out thermic calculations for adjusted conditions of electric and heat energy consumption. The power of the generator is 330 MW. In the proposal, you can find combustion trubines type GE 9171E. Steam-gas power plant is designed to combust metallurgical gases. Effort of the thesis focuses also on giving a new informations about trends in combinated production of electric and heat energy.

This thesis is an investigation of different strategies for efficient development and optimization of radial-inflow turbines (RIT) for small-scale ORC systems. A novel methodology based on mean-line modelling, multi-level optimization and experimental study was proposed and validated for a small-scale compressed air RIT. Extending the proposed approach to organic fluids necessitated the use of real-gas equations. Deficiencies of constant turbine efficiency assumption that was commonly used in the literature were highlighted. A novel approach for integrated modelling of organic RIT with ORC coupled with genetic algorithm optimization technique was developed to alleviate the errors during fluid selection and cycle analysis and also optimize the ORC performance. A novel dual-stage transonic RIT was developed to further improve the ORC performance. The efficiency of such turbine was improved further using 3-D CFD optimization technique. Such optimization proved to be very efficient as it substantially improved the turbine efficiency of both stages by about 10%. CFD results for the optimized dual-stage turbine at design point showed the turbine efficiency of 87.12% and ORC thermal efficiency of 13.19%. Such results were considerably higher than the reported values in the literature and highlighted the effectiveness of the combined mean-line and CFD optimizations developed in thesis.

This master´s thesis deals with two pressure heat recovery steam generator behind gas turbine. From the entered parameters steam and gas were designed heating surfaces, specifically their size and configuration. The overall design is then proposed in the drawing.

This thesis deals with a heat recovery steam generator for gas turbine. According to the given parameters of the flue and steam, thermal balance boiler was design and configuration of the heating surfaces. Furthermore, the parameters calculated in the thermal balance of the individual heat transfer surfaces designed and drawn in the drawing.

This master‘s thesis describes thermal calculation and design of proportions of calorific components of a heat recovery steam generator (HRSG) for given input parameters of flue gas and output parameters of steam. Part of the thesis is design proportions of boiler drums, irrigation and transfer pipes. On the end of the thesis is counting draught losses and design drawning of steam generator.

This thesis deals with thermal calculation and design of proportions and layout of calorific components of a heat recovery steam generator according to given output parameters of steam and input parameters of flue gas. Furthermore, the proportions of boiler drums and irrigation and transfer pipes are designed and draught losses are calculated.

The target of this diploma thesis is design of cogeneration unit with following requirements: • Installation of new unit instead of the old and used up one. • Electric energy supply within Supportive service – fast starts • Greening (replacement of coal with natural gas) At the beginning I deal with the current state of old unit. In the next part there is the design of new technological unit, which consists of design of boilers, gas engines, steam turbines. Final phase of the thesis includes economical analysis focused on setting of financial return.

This master’s thesis deals with the design of a heat recovery steam generator. The introductory part of the thesis is dedicated to waste heat boilers, their division and their utilization in combined cycles gas turbine. In the following chapter, an analysis of the existing combined heat and power plant operation is performed. In the next part of the thesis, the conceptual layout of the new source is designed. Subsequently, the thermal calculation of the boiler is carried out as well as the design of individual heat exchanging surfaces. The sixth chapter deals with the strength calculation of the boiler and the outer piping, chambers and drum are designed here. At the end of the thesis there are described off-design states of the new combined cycle gas turbine.

The topic of thesis is condensing turbine in gas-steam cycle, which can be divided into four basic parts. A history of gas-steam cycle is described in the beginning. Second part is all about calculation of heat recovery steam generator. Penultimate section deals with calculations of steam turbine parameters and reaction blading type. Last part contains electric power and steam turbine efficiency.

This thesis deals with the design of a Heat Recovery Steam Generator (HRSG). Theintroductory part is devoted to a brief description of the boiler, the specified parametersand the compilation of the temperature profile. The main computational part of thiswork is divided into 6 parts. The first contains preparatory calculations, including thecalculation of boiler eiciency. In the second part, a flue gas duct is designed. This isfollowed by a thermal calculation of the boiler for all heat exchange surfaces. The last 3parts deal with the design of the drum, piping and the loss of boiler draft calculation.

Der integrierte Gas-Dampf (GiD-) Prozess mit Wasserrückgewinnung ist ein flexibler Kraft-Wärme-Kopplungsprozess, der die gleichzeitige Bereitstellung von Strom und Wärme teilweise entkoppeln kann. Der effiziente und sparsame Einsatz von fossilen Brennstoffen ist aus ökonomischer wie auch ökologischer Sicht geboten. Die Kraft-Wärme-Kopplung (KWK), die gleichzeitige Erzeugung von Strom und Wärme, ist eine Möglichkeit dafür. Allerdings erfordert die KWK auch eine gleichzeitige Abnahme von Strom und Wärme beziehungsweise deren Speicherung. Sowohl Strom als auch Prozessdampf lassen sich nur aufwendig und damit relativ teuer speichern, weshalb Alternativen gefragt sind. Der GiD-Prozess besteht aus einer Gasturbine mit nachgeschaltetem Abhitzedampfkessel. Die Gasturbine verfügt als Besonderheit über eine Dampfinjektion, die vor, nach oder direkt in die Brennkammer erfolgen kann. Der Abhitzekessel hat zusätzliche Wärmeübertragerflächen um das Abgas bis unter den Taupunkt abzukühlen. Somit kann ein Teil des injizierten Dampfes aus dem Abgas zurückgewonnen und wiederverwendet werden. Der in die Gasturbine injizierte Dampf führt dieser weitere Energie zu. Diese kann entweder zur Leistungssteigerung der Anlage oder zur Reduzierung des fossilen Brennstoffbedarfes genutzt werden. Die erste Option der Leistungssteigerung ist auch als Cheng-Prozess bekannt. Diese Arbeit widmet sich der weniger untersuchten zweiten Möglichkeit der Brennstoffreduzierung. Beim Vergleich des GiD-Prozesses mit verschiedenen anderen Kraftwerks-Prozessen zeigt sich, dass dieser besonders gut für industrielle Anlagen mit Prozessdampfbedarf und einer elektrischen Leistung kleiner 20 MW el geeignet ist. Im Rahmen dieser Arbeit wurde der GiD-Prozess mittels einer Versuchsanlage auf Basis einer Industriegasturbine mit 650 kW el untersucht. Die Arbeit dokumentiert verschiedene Versuchsfahrten und Untersuchungen an dieser Anlage. Die Injektion von Dampf reduziert die Schadstoffemissionen in den zulässigen Bereich und kann sehr flexibel zu einer Steigerung des Anlagenwirkungsgrades von bis zu zwei Prozent führen. Dabei wird der Dampf sehr gleichmäßig in die Versuchsanlage eingebracht, so dass keine signifikanten Änderungen der Abgastemperaturverteilung erkennbar sind. Die Überhitzung des Dampfes kann zu einer weiteren Steigerung des Anlagenwirkungsgrades führen. Die Rückgewinnung des eingebrachten Dampfes ist mit den entsprechenden Wärmeübertragern möglich. Das zurückgewonnene Wasser ist durch die Stickoxide des Abgases verunreinigt und muss entsprechend aufbereitet werden.

Master’s thesis deal with the design of waste to energy plant of municipal waste. The design of technology is to build the component parts of plant and basic calculation of individual apparatus. Overall technology concists of pretreatment of municipal waste, which is then stored in the bunker. Pretreatment municipal waste is fed into the counterflow rotary kiln. Flue Gates from the kilns are routed through multicyklony in the heat recovery steam generators (HRSG). The multicyklon separates the pollutants. The HRSG generates steam required properties from the feedwater from the heat kontent of gas. Superheated steam is driven to the condensing turbine with extract steam for distrikt rating and for power generation. The flue gas from the HRSG are passed through purification section, in which are separand pollutants the dry method purification. The left heat content of flue gas is used in heat exchanger with twist tube for preheating feed water for the HRSG. The flue gas are fed to the stack.

La récupération de chaleur dans les véhicules est une solution prometteuse permettant de réduire la consommation du moteur et de ses émissions. Les fortes contraintes de poids, compacité et coût présentes dans le domaine automobile empêchent l’intégration d’un système de récupération de chaleur dans le véhicule. Une solution proposée dans ce travail consiste en un système de multi-génération appelé ReverCycle. Ce dernier fonctionne avec trois modes: climatisation à compression de vapeur, cycle de Rankine Organique (ORC) et cycle de réfrigération à éjecteur. Le système peut assurer un seul mode de fonctionnement à la fois. Les avantages du système sont sa compacité et son coût réduit étant donné la possibilité d’exploiter les composants du système de climatisation déjà présents dans le véhicule. En effet, le compresseur scroll de la climatisation peut être converti en machine réversible compresseur/turbine et le condenseur peut être mutualisé pour les trois modes de fonctionnement. Une double démarche de modélisation et d’expérimentation a été menée pour évaluer le potentiel de réduction de la consommation de ReverCycle et pour vérifier sa faisabilité technique. Un modèle global du véhicule a été développé pour reproduire les conditions de fonctionnement dynamique du véhicule et pour décrire l’interaction entre ses différents sous-systèmes. Le modèle a ensuite permis de calculer le gain en consommation moyenné sur une année pour différentes régions climatiques. Deux différentes architectures de véhicules ont été étudiées : un véhicule conventionnel et un véhicule hybride série. Pour un véhicule conventionnel, le gain en consommation maximal est obtenu dans un climat océanique (e.g. Paris) avec une valeur de 2,1% avec un démarrage à chaud du moteur et 1,3% avec un démarrage à froid. Le cycle de conduite de référence pour l’évaluation du gain est le cycle WLTC (Worldwide harmonized Light vehicles Test Cycles). Dans le cas du véhicule hybride série, le gain en consommation maximal est obtenu dans un climat continental (e.g. Moscou) avec une valeur de 2,2% avec un démarrage à chaud du moteur et 1,2% avec un démarrage à froid. La réalisation d’une preuve de concept de ReverCycle a permis de valider sa faisabilité technique. Les essais se sont focalisés surtout sur le mode de fonctionnement en ORC. Les résultats des essais ont montré un rendement maximal de récupération pour le cycle de 3,9% sur un point de fonctionnement stabilisé. Le rendement maximal moyenné sur un cycle dynamique, représentatif des conditions opératoires sur un véhicule conventionnel, a été de 3,3%
In a light duty vehicle, waste heat recovery is a promising solution for reducing engine fuel consumption and emissions. The strong compactness, weight and cost requirements of the automotive sector are preventing the integration of waste heat recovery systems in vehicles. This work is proposing as a possible solution a multi-generation system called hereafter ReverCycle. ReverCycle is a system with three operating modes: vapor compression air conditioning, Organic Rankine Cycle (ORC) and ejector refrigeration cycle. The system can provide one function at a time. ReverCycle advantages are its compactness and cost since it is possible to exploit the vehicle air conditioning components. This means that the air conditioning scroll compressor is converted into a reversible compressor/expander machine and the condenser is mutualized for the three operating modes. The calculation of the fuel economy and the technical feasibility of the system are investigated combining a modeling approach with experimental activity. A global vehicle model reproduces the vehicle dynamic working conditions and the interaction between the different vehicle sub-systems. The model estimates the annual average fuel economy for different climatic regions. Two different vehicle architectures are investigated: a conventional vehicle and a series hybrid vehicle. For a conventional vehicle the maximum fuel economy is obtained in an oceanic climate ( e.g. Paris) with a 2.1% improvement at a hot start initial condition for the engine and 1.3% improvement at a cold start initial condition. The reference driving cycle for the fuel economy evaluation is the WLTC (Worldwide harmonized Light vehicles Test Cycles). For a series hybrid vehicle the maximum fuel economy is obtained in a continental climate ( e.g. Moscow) with a 2.2% improvement at a hot start initial condition for the engine and 1.2% improvement at a cold start initial condition. The realization of ReverCycle proof of concept has allowed validating its technical feasibility. Experimental tests have mainly focused on the ORC operating mode. The experimental results show that the maximum cycle efficiency is 3.9% for a steady-state point. The average maximum cycle efficiency over a dynamic cycle, equivalent to a typical conventional vehicle operating mode, is 3.3%

La finalità di questo lavoro di tesi è la valutazione quantitativa delle prestazioni dei cicli Brayton a CO2 supercritica. Per dare fondamento alle motivazioni che spingono ad un tale studio, il punto di partenza è stato analizzare la statistica riguardante le potenzialità del calore di scarto. Un passo ulteriore è stato non solo quantificare l’energia recuperabile, ma anche avere tabulati con le temperature alle quali tali energie sono disponibili in un panorama industriale che coinvolge diversi settori produttivi. Per ogni settore produttivo è stato possibile anche associare, ad un suo j-esimo processo, una fascia di temperatura alla quale il fluido viene scartato, come liquido o come gas. Successivamente, è stato necessario mettere in luce le proprietà della CO2 . Esso si mostra infatti compatibile con un utilizzo all’interno di un ciclo Brayton, e può anche presentare dei vantaggi rispetto ai fluidi dei cicli tradizionali: la sua densità è grande a tal punto da ottenere impianti con potenze in uscita elevate e ingombri particolarmente ridotti. Si è passati poi ad una rassegna di tre layout, uno semplice e due più complessi, studiati da più autori, con conclusioni complementari. Il capitolo successivo, quello della simulazione dei cicli di potenza in ambiente Aspen Hysys, è stato suddiviso in due parti. Nella prima parte sono presenti istruzioni più di carattere operativo per l’utilizzo del software. Nella seconda parte vengono invece mostrati i risultati delle simulazioni, con l’obiettivo di massimizzare il rendimento totale di recupero termico ηtot . Tale obiettivo è stato conseguito al variare di alcuni parametri, come temperatura di ingresso dei fumi nello scambiatore principale (Tfumi), temperatura di ingresso in turbina ( TIT ), pressione massima di ciclo (pmax), e potenza netta erogata dall’impianto ( Pnet ).

Many reactions carried out in the chemical industry are exothermic. The heat liberated by the reaction is often transferred to another medium such as steam by heat exchange. This heat can then be used elsewhere or be used to generate power via a steam cycle. In this work the focus is on another method of reaction heat recovery. When an exothermic reaction is conducted at elevated pressures, a turbine expander can be placed directly behind the reactor. The hot, high-pressure product gas from the reactor can then be expanded in the turbine. During the expansion process the physical energy of the product gas is converted to kinetic energy (or electricity if the turbine is connected to a generator). Three chemical processes were studied to determine the feasibility of turbine integration into the processes. They are ethylene oxide production, phthalic anhydride production and the hydrodealkylation of alkylaromatic compounds. The chosen processes differ in terms of reactor operation, reactant conversion as well as the presence or absence of recycle loops. Simulation models were developed for the mentioned processes with the process simulator Aspen Plus®. Results from the simulations show that, without the turbine, the processes require power from external sources. They can however operate independently from external power sources when a turbine is present. Excess power can be exported or used for electricity generation. It is therefore feasible• to incorporate turbine expansion units in all the processes considered. The operating conditions of some unit operations have to be changed to accommodate the turbine expander. With the additional product namely power, a re-evaluation of all the operating conditions and tradeoffs in the process is necessary. Further investigation into the impact of turbine integration on the optimal operating conditions of the process is therefore recommended. Traditional definitions used to evaluate the performance of a process generating or consuming power, were found to be inadequate for use in processes where power and chemicals are produced together. New performance parameters are required for the evaluation of processes where power and chemicals are produced simultaneously. An exergy analysis was performed for one of the cases. This analysis method provides insight as to where thermodynamic losses occur in a process. The exergy analysis was useful to quantify the losses occurring in an isenthalpic expansion valve, and the savings obtained by replacing such a valve with an expansion turbine.
Dissertation (MEng (Chemical Engineering))--University of Pretoria, 2006.
Chemical Engineering
unrestricted

博士
國立成功大學
機械工程學系碩博士班
90
In Taiwan, many existing simple-cycle gas turbine generation sets (GENSET) that were originally designated as peak load units can be started up in a very short time(say 15 minutes), but suffer from very low efficiency (around 26%). Unfortunately, the simple-cycle units are forced to operate entire summer daytime due to the power shortage in Taiwan. In addition, the power generation of gas turbine degrades significantly during summer peaking hours (when electricity is most needed) due to the hot ambient temperatures. The aim of this research is to evaluate the feasibility of retrofitting these simple-cycle units into more advanced cycle with higher power output and efficiency. A computer code was developed to evaluate the performance improvement of different modifications for simple cycle GENSETs. The accuracy of our developed code was validated by simulating the actual GE Frame 6B and 7B simple-cycle GENSETs. The results from computer simulation indicated that the steam injection gas turbine (STIG) cycle with regenerator was found to be the most effective in boosting both the power output and thermal efficiency among many proven technologies. From thermoeconomic analysis, the retrofitting project with STIG and regeneration features also has the best rate of return. In the consideration of local hot/humid weather and the complication of retrofitting, the integration of STIG and inlet air cooling (IAC) was also proposed in this study. This integrated system can boost 60% of power output under hot and humid weather condition and greatly depress the emission of NOx. The performance of this system is less sensitive to ambient temperature, and its heat-to-power ratio can be swiftly adjusted to meet the actual demand.

Der integrierte Gas-Dampf (GiD-) Prozess mit Wasserrückgewinnung ist ein flexibler Kraft-Wärme-Kopplungsprozess, der die gleichzeitige Bereitstellung von Strom und Wärme teilweise entkoppeln kann. Der effiziente und sparsame Einsatz von fossilen Brennstoffen ist aus ökonomischer wie auch ökologischer Sicht geboten. Die Kraft-Wärme-Kopplung (KWK), die gleichzeitige Erzeugung von Strom und Wärme, ist eine Möglichkeit dafür. Allerdings erfordert die KWK auch eine gleichzeitige Abnahme von Strom und Wärme beziehungsweise deren Speicherung. Sowohl Strom als auch Prozessdampf lassen sich nur aufwendig und damit relativ teuer speichern, weshalb Alternativen gefragt sind. Der GiD-Prozess besteht aus einer Gasturbine mit nachgeschaltetem Abhitzedampfkessel. Die Gasturbine verfügt als Besonderheit über eine Dampfinjektion, die vor, nach oder direkt in die Brennkammer erfolgen kann. Der Abhitzekessel hat zusätzliche Wärmeübertragerflächen um das Abgas bis unter den Taupunkt abzukühlen. Somit kann ein Teil des injizierten Dampfes aus dem Abgas zurückgewonnen und wiederverwendet werden. Der in die Gasturbine injizierte Dampf führt dieser weitere Energie zu. Diese kann entweder zur Leistungssteigerung der Anlage oder zur Reduzierung des fossilen Brennstoffbedarfes genutzt werden. Die erste Option der Leistungssteigerung ist auch als Cheng-Prozess bekannt. Diese Arbeit widmet sich der weniger untersuchten zweiten Möglichkeit der Brennstoffreduzierung. Beim Vergleich des GiD-Prozesses mit verschiedenen anderen Kraftwerks-Prozessen zeigt sich, dass dieser besonders gut für industrielle Anlagen mit Prozessdampfbedarf und einer elektrischen Leistung kleiner 20 MW el geeignet ist. Im Rahmen dieser Arbeit wurde der GiD-Prozess mittels einer Versuchsanlage auf Basis einer Industriegasturbine mit 650 kW el untersucht. Die Arbeit dokumentiert verschiedene Versuchsfahrten und Untersuchungen an dieser Anlage. Die Injektion von Dampf reduziert die Schadstoffemissionen in den zulässigen Bereich und kann sehr flexibel zu einer Steigerung des Anlagenwirkungsgrades von bis zu zwei Prozent führen. Dabei wird der Dampf sehr gleichmäßig in die Versuchsanlage eingebracht, so dass keine signifikanten Änderungen der Abgastemperaturverteilung erkennbar sind. Die Überhitzung des Dampfes kann zu einer weiteren Steigerung des Anlagenwirkungsgrades führen. Die Rückgewinnung des eingebrachten Dampfes ist mit den entsprechenden Wärmeübertragern möglich. Das zurückgewonnene Wasser ist durch die Stickoxide des Abgases verunreinigt und muss entsprechend aufbereitet werden.