Thesis topic MECHANICAL department Applied Thermodynamics. Design of a humidification tower for a typical microgasturbine

Transcription

1 Thesis topic MECHANICAL department Applied Thermodynamics Design of a humidification tower for a typical microgasturbine Promotor: prof. dr. ir. Jacques De Ruyck Copromotor: More information: wdepaepe@vub.ac.be (+32) Abstract Microturbines are small, compact electricity generators with rated capacities in the kw range. They typically use a high- speed generator/turbo alternator, resulting in high frequency AC electricity. The high frequency electricity is converted into useful electric power via power electronics. The microturbines differ from the industrial sized gas turbines in the way waste heat is recuperated to boost (electrical) efficiency and its ability to combine heat and power generation. Typical microturbines incorporate a recuperator, using heat from the exhaust gases to preheat the combustion air, resulting in significant efficiency gains compared to non- recuperated machines. Continuous combustion at limited temperature and high excess air found in microturbine combustors results in low emissions of air pollutants. This is particularly true for NO x emissions as compared to diesel engines. Microturbine manufacturers also claim advantages in terms of fuel flexibility and service and maintenance costs due to their relatively simple mechanical design. Figure 1: Typical Microgasturbine Layout A typical microturbine (MGT) has an electrical efficiency, limited to about 30-33%, depending on the model and the manufacturer. Many investigations are currently being done to see how that electrical efficiency can be raised to match its direct competitors, being Internal Combustion Engines (ICE).

2 Problem statement Microturbines offer new perspectives in small- scale heat and power production however their profitability depends strongly on the yearly amount of running hours. The non- continuous heat demand often leads to a reduction in running hours. An alternative is recuperating the lost thermal power through the injection of heated water in the microgasturbine. Water injection is considered a successful way to increase power and efficiency in industrial gas turbines and similar effects are expected for microturbines. Past experiments with steam injection on the T100 demonstrated the potential of introducing steam/water in the microturbine cycle. Simulations showed that most of the microgasturbine exhaust heat can be recovered through injection of heated water after the compressor, resulting in 18% decrease in fuel consumption and an absolute increase in electrical efficiency of 7%. Figure 2: Water injection system for microgasturbine with the saturation tower to design Goal of the thesis This thesis will focus on the design of a humidification tower for the T100 microgasturbine, installed in the mechanical. The main boundary conditions of the humidification tower are known, however the technical implementation is still unknown. The goal of this thesis is to design different specific lay- outs of humidification towers for the Turbec T100 microgasturbine. The student will have to make different designs of humidification towers, using two- phase flow theory. Many humidification techniques can be found in literature. Final goal of the thesis is to select a final design, taken into account different specifications which are small pressure drop, limited volume and easy to implement. Content of thesis Literature study on the topics of o Micro gas turbine o Humid air turbine o 2- phase flow Simulation and design of a saturation tower Validation through literature

3 Thesis topic MECHANICAL department Applied Thermodynamics Dynamic simulation of the water injection in a microgasturbine Promotor: prof. dr. ir. Jacques De Ruyck Copromotor: More information: wdepaepe@vub.ac.be (+32) Abstract Microturbines are small, compact electricity generators with rated capacities in the kw range. They typically use a high- speed generator/turbo alternator, resulting in high frequency AC electricity. The high frequency electricity is converted into useful electric power via power electronics. The microturbines differ from the industrial sized gas turbines in the way waste heat is recuperated to boost (electrical) efficiency and its ability to combine heat and power generation. Typical microturbines incorporate a recuperator, using heat from the exhaust gases to preheat the combustion air, resulting in significant efficiency gains compared to non- recuperated machines. Continuous combustion at limited temperature and high excess air found in microturbine combustors results in low emissions of air pollutants. This is particularly true for NO x emissions as compared to diesel engines. Microturbine manufacturers also claim advantages in terms of fuel flexibility and service and maintenance costs due to their relatively simple mechanical design. Figure 1: Typical Microgasturbine Layout A typical microturbine (MGT) has an electrical efficiency, limited to about 30-33%, depending on the model and the manufacturer. Many investigations are currently being done to see how that electrical efficiency can be raised to match its direct competitors, being Internal Combustion Engines (ICE).

4 Problem statement Microturbines offer new perspectives in small- scale heat and power production however their profitability depends strongly on the yearly amount of running hours. The non- continuous heat demand often leads to a reduction in running hours. An alternative is recuperating the lost thermal power through the injection of heated water in the microgasturbine. Water injection is considered a successful way to increase power and efficiency in industrial gas turbines and similar effects are expected for microturbines. Past experiments with steam injection on the T100 demonstrated the potential of introducing steam/water in the microturbine cycle. Simulations showed that most of the microgasturbine exhaust heat can be recovered through injection of heated water after the compressor, resulting in 18% decrease in fuel consumption and an absolute increase in electrical efficiency of 7%. Figure 2: Water injection system for microgasturbine Goal of the thesis This thesis will focus on the dynamic simulation of the water injection in a T100 microgasturbine. Steady state simulations have indicated the positive effect of water injection in the microgasturbine. The control system of the T100 microgasturbine however is not adapted to water injection and possible issues may rise through the water injection. For his thesis, the student needs to build a dynamic simulation model of the T100 microgasturbine, the control system and the water injection systems in Matlab Simulink. Possible issues with instabilities through the injection of water need to be studied. In a final step, the student can adapt the control system to the water injection, in order to increase the potential for water injection. Content of thesis Literature study on the topics of o Micro gas turbine o Humid air turbine o Control systems Simulation of the control system and the dynamic behavior of the machine and Validation through measurements

5 Thesis topic MECHANICAL department Applied Thermodynamics Residential Post- Combustion Carbon Capture Promotor: prof. dr. ir. Jacques De ruyck Co- promotor: dr. ir. Frank Delattin More information: (+32) Abstract Post- combustion carbon capture is based on capturing CO2 from flue gas by using a reactive chemical solvent to absorb CO2 in a scrubber. The gases pass through the absorption column, chemically binding CO2 to the solvent before being released into the atmosphere. After absorption, the scrubber needs to be heated to release CO2 which then can be stored for transport (Figure 9). Fig. 9: Simplified overview of post- combustion carbon capture Typically, in power plants, heat from the steam turbine is used to heat the solvent, resulting in a loss of efficiency of typically 15-25%. The main idea of the thesis, is to apply the concept on residential heating installations, where the heat is available and can be recuperated after its use on the

6 scrubber. The CO2 could be stored and transported every time the fuel tank is replenished or on a scheduled basis (for natural gas fired heating installations). This innovative idea, raises many questions, such as: - Overall cost and payback time depending on GHG mitigation subsidies - Power required by the CO2 compressor - Storage limitations - Technical feasibility - Heat Exchanger design (Composite Curve application) - Total potential for GHG mitigation - The main concept behind the idea is that, whereas in power plants, heat is converted into electrical power, and diverting part of it results in loss of efficiency and profitability, in residential heating installations, the heat is available and should be relatively easy to recuperate. However, because of its very decentralized character, the storage and transport of carbon dioxide together with the techno- economic feasibility are of great concern. The thesis, in short, would involve a techno- economic feasibility study, combining a process analysis of its possible efficiency and estimated cost, with a suggestion for allocating the captured CO2 to the appropriate sink.

7 Thesis topic MECHANICAL department Applied Thermodynamics Mapping the potential of biogas utilization on the Cuban island and its power generation infrastructure Promotor: prof. dr. ir. Jacques De ruyck Co- promotor: dr. ir. Frank Delattin More information: (+32) Anaerobic digestion An introduction to anaerobic digestion will be given to jumpstart the research required for the current thesis proposal. Cuban-Belgium Exchange The student will need to gather all the required information, numbers and charts to map Cuba s biogas resources and demographic/power production (and demand) characteristics. Belgium, as European capital, will serve to gather the required technological information of biogas plants and digesters, required to make a detailed analysis of the best suited technology and its allocated costs. The focus of this thesis proposal can be split up into the following parts: - Chart the potential for biogas production in Cuba, and this for the various feedstock/organic waste/animal manure/wastewater influents useful to biogas production facilities Chart the best locations for decentralized production units in Cuba Investigate and select the best biogas plant technology for the available influents and local conditions Setup a detailed techno- economic evaluation of two scenarios: o Biogas used to replace a certain part of the fossil fuel consumption used in the current Cuban power infrastructure o Biogas used in dedicated, new plants Summarize the whole into an actual project proposal if biogas plants turn out to be profitable, convince the jury of its (financial, ecological, socio- technological) merits Influents

8 In terms of the useful influents for biogas production, the following streams may be the most important to investigate (location and transport required, energetic value, C/N content, scale of the stream, certitude of long term delivery and consistent, ): - animal waste (manure) from chicken and other food production facilities - organic waste (and sewage slurry) from hotel complexes surrounding the cities and coastline of the Cuban island - organic 2 nd generation feedstocks (residue from agricultural crops) - Sugar cane (over)production: sugar cane that was overproduced with respect to price setting on the international sugar market; and its residues (vinasse, bagasse) Others could be identified and should be investigated along the process of the proposed thesis. For each of the streams and their combination, the potential biogas production (rate) should be estimated, and the best combinations of available influents and their potential magnitude in terms of plant size, should be investigated and summarized. Technology identification The Cuban climate, the available influents and the required maintenance and level of management/operation will dictate the best suitable technology for the proposed biogas plants. All these factors should be analyzed in detail in order to make a well argumented decision. Visit an actual biogas plant of the various technologies considered and report on the experience, problems and opportunities the operator has had throughout its running hours. The two or three appropriate digester types should be compared in the technoeconomic part to select the definitive type. Biogas plant location One of the most important factors in the success and profitability of biogas plants (besides a consistent, certain and constant uptake of influents), is the location of the plant. The generated power needs to be transported over a certain distance (preferably close to its consumption, i.e. at the outskirt of cities and hotel clusters), the influents need to be transported at a certain frequency and stored on-site, and the wet/dried digestate needs to be transported to the agricultural fields to be used as fertilizer. Investigate the potential benefit of drying the digestate in order to optimalize transport. Keep in mind the odor hazard of biogas plants, due to the process of organic/animal waste and the storage of digestate volumes. This odor typically limits the location close to urban regions. Finally, hurricanes are one of Cuba s constant perils and hazards. In terms of electricity production, this translates in the favor for several smaller plants rather than one big, central plant. All these factors need to be investigated in order to select the best position(s) for biogas plants of a certain magnitude on the Cuban island. Techno-economic evaluation Once the influents and locations have been mapped, make a detailed economic analysis of the capital costs and operation costs associated to the different appropriate influent streams and digester types. Include transport, storage, maintenance and operating costs (CAPex and OPex). Analyze the Cost of Electricity (CoE) with and without available the subsidies of Clean Development Mechanism (CMD projects). Make a realistic (or even pessimistic) analysis of the profitability of the proposed plant(s) throughout their lifetime, using financial tools such as Net Present Value, Internal Rate of Return, Simple Payback Time with a realistic depreciation and indexation value. This Techno-economic evaluation should be made for two scenarios:

9 - - Use of biogas to replace fossil fuel where possible/suited in the existing Cuban power infrastructure (ICE engines suited for combustion of natural gas and biogas after appropriate treatment of the biogas) Development of dedicated, new biogas power plants in the chosen location and of the best suited type Project proposal As an engineer, all projects in your near future will have to be proposed to a jury. Summarize your findings in an attractive and to the point project proposal (presentation of 15 minutes, maximum) that should convince any jury and financiers of your findings.

10 Thesis topic MECHANICAL department Applied Thermodynamics Chemical looping to limit exergy destruction in a typical microturbine combustor Promotor: prof. dr. ir. Jacques De ruyck Co- promotor: dr. ir. Frank Delattin More information: frank.delattin@vub.ac.be (+32) Abstract Microturbines are small, compact electricity generators with rated capacities in the kw range. They typically use a high-speed generator/turbo alternator, resulting in high frequency AC electricity.the high frequency electricity is converted into useful electric power via power electronics. The microturbines differ from the industrial sized gas turbines in the way waste heat is recuperated to boost (electrical) efficiency and its ability to combine heat and power generation. Typical microturbines incorporate a recuperator, using heat from the exhaust gases to preheat the combustion air, resulting in significant efficiency gains compared to non-recuperated machines. Continuous combustion at limited temperature and high excess air found in microturbine combustors results in low emissions of air pollutants. This is particularly true for NOx emissions as compared to diesel engines. Microturbine manufacturers also claim advantages in terms of fuel flexibility and service and maintenance costs due to their relatively simple mechanical design. A typical microturbine (MGT) has an electrical efficiency, limited to about 30-33%, depending on the model and the manufacturer. Many investigations are currently being

11 done to see how that electrical efficiency can be raised to match its direct competitors, being Internal Combustion Engines (ICE). In order to raise this efficiency, many improvements in terms of the typical recuperator are being proposed, and a ceramic turbine, capable of withstanding (much) higher temperatures than the typical 900 C 1000 C is a second viable (but possibly not very economic) option. Chemical looping has been applied to industrial processes in the past, where a certain chemical compound is used to dope the combustion regime and limit the exergy destruction. The research group of Applied Thermodynamics has, for example, used this concept to steam reform the natural gas feed into a hydrogen and carbon monoxide containing partially reformed fuel mixture, which is then combusted in the original gas turbine combustor thus limiting exergy destruction in this GT component. The current thesis aims at investigating the application of this chemical looping technique on the microturbine combustion regime in order to limit exergy destruction and raise efficiency while keeping the original installation completely intact. A certain doping of the combustion air or the fuel mixture, could possibly result in a seemingly costefficient raise in electrical efficiency, thus strengthening the MGT position vis a vis its main ICE competitors. This research will be done mainly through detailed process analysis, using the Aspen process simulation tool and the black-box methodology, developed at the Applied Thermodynamics Research Group.