Optimization of a Biomass Torrefaction Plant With Near Zero Emissions

2019 ◽  
Author(s):  
Mahmudul Hasan ◽  
Yousef Haseli
Keyword(s):  
Carbon Dioxide ◽  
Residence Time ◽  
Process Model ◽  
Energy Requirement ◽  
Air Separation ◽  
Working Fluid ◽  
Energy Yield ◽  
Total Energy Consumption ◽  
Design Data ◽  
Separation Unit

Abstract Recent studies have shown that the emissions from conventional torrefaction processes is the second largest contributor to the supply chain. This article presents a torrefaction unit that operates based on oxy-combustion concept, whereby preventing carbon dioxide and nitrogen oxides emissions. The oxygen required in the process is supplied from an Air Separation Unit (ASU) and the working fluid of the new system is carbon dioxide. The process model is implemented in Engineering Equation Solver (EES) and simulation is conducted using the design data of a conventional plant which torrefies wood at 553 K for 17.5 minutes. The overall efficiency of the plant which accounts for both thermal and electrical energy requirement of the process is found to be 88%. The total energy consumption of the system exhibits a minimum at an optimum torrefaction temperature. With willow as the feedstock, the optimum temperature is determined to be 536 K at a residence time of 20 minutes, at which the total equivalent thermal energy required is 2 MJ/kg dry biomass and the energy yield is as high as 91%. The results show that the optimum torrefaction temperature is feedstock dependent and it is lower for a longer residence time.

Thermodynamic Analysis of Zero-Atmospheric Emissions Power Plant

2004 ◽  
Vol 126 (1) ◽  
pp. 2-8 ◽  
Author(s):  
Joel Martinez-Frias ◽  
Salvador M. Aceves ◽  
J. Ray Smith ◽  
Harry Brandt
Keyword(s):  
Carbon Dioxide ◽  
Power Plant ◽  
Thermodynamic Analysis ◽  
Oil Recovery ◽  
Air Separation ◽  
Working Fluid ◽  
Atmospheric Emissions ◽  
Steam Turbines ◽  
Gas Generator ◽  
Separation Unit

This paper presents a theoretical thermodynamic analysis of a zero-atmospheric emissions power plant. In this power plant, methane is combusted with oxygen in a gas generator to produce the working fluid for the turbines. The combustion produces a gas mixture composed of steam and carbon dioxide. These gases drive multiple turbines to produce electricity. The turbine discharge gases pass to a condenser where water is captured. A stream of pure carbon dioxide then results that can be used for enhanced oil recovery or for sequestration. The analysis considers a complete power plant layout, including an air separation unit, compressors and intercoolers for oxygen and methane compression, a gas generator, three steam turbines, a reheater, two preheaters, a condenser, and a pumping system to pump the carbon dioxide to the pressure required for sequestration. This analysis is based on a 400 MW electric power generating plant that uses turbines that are currently under development by a U.S. turbine manufacturer. The high-pressure turbine operates at a temperature of 1089 K (1500°F) with uncooled blades, the intermediate-pressure turbine operates at 1478 K (2200°F) with cooled blades and the low-pressure turbine operates at 998 K (1336°F). The power plant has a net thermal efficiency of 46.5%. This efficiency is based on the lower heating value of methane, and includes the energy necessary for air separation and for carbon dioxide separation and sequestration.

scholarly journals Process and Carbon Footprint Analyses of the Allam Cycle Power Plant Integrated with an Air Separation Unit

2019 ◽  
Vol 1 (1) ◽  
pp. 325-340 ◽  
Author(s):  
Dan Fernandes ◽  
Song Wang ◽  
Qiang Xu ◽  
Russel Buss ◽  
Daniel Chen
Keyword(s):  
Carbon Dioxide ◽  
Power Generation ◽  
Sensitivity Analysis ◽  
Power Plant ◽  
Carbon Footprint ◽  
Exergy Analysis ◽  
Air Separation ◽  
Working Fluid ◽  
Separation Unit ◽  
Air Separation Unit

The Allam cycle is the latest advancement in power generation technologies with a high cycle efficiency, zero NOx emission, and carbon dioxide available at pipeline specification for sequestration and utilization. The Allam cycle plant is a semi-closed, direct-fired, oxy-fuel Brayton cycle that uses high pressure supercritical carbon dioxide as a working fluid with sophisticated heat recuperation. This paper conducted process analyses including exergy analysis, sensitivity analysis, air separation unit (ASU) oxygen pump/compressor option analysis, and carbon footprint analysis for the integrated Allam power plant (natural gas)/ASU complex with a high degree of heat and work integration. Earlier works on exergy analysis were done on the Allam cycle and ASU independently. Exergy analysis on the integrated plants helps identify the equipment with the largest loss of thermodynamic efficiency. Sensitivity analysis investigated the effects of important ASU operational parameters along with equipment constraint limits on the downstream Allam cycle. Energy efficiency and carbon footprint are compared among the state-of-the-art fossil-fuel power generation cycles.

Techno-Economic Evaluation of Pressurized Oxy-Fuel Combustion Systems

2010 ◽  
Author(s):  
Jongsup Hong ◽  
Ahmed F. Ghoniem ◽  
Randall Field ◽  
Marco Gazzino
Keyword(s):  
Carbon Dioxide ◽  
Carbon Dioxide Emissions ◽  
Power Plants ◽  
Carbon Dioxide Capture ◽  
Fuel Combustion ◽  
Economic Feasibility ◽  
Operating Conditions ◽  
Air Separation ◽  
Separation Unit ◽  
Coal Price

Oxy-fuel combustion coal-fired power plants can achieve significant reduction in carbon dioxide emissions, but at the cost of lowering their efficiency. Research and development are conducted to reduce the efficiency penalty and to improve their reliability. High-pressure oxy-fuel combustion has been shown to improve the overall performance by recuperating more of the fuel enthalpy into the power cycle. In our previous papers, we demonstrated how pressurized oxy-fuel combustion indeed achieves higher net efficiency than that of conventional atmospheric oxy-fuel power cycles. The system utilizes a cryogenic air separation unit, a carbon dioxide purification/compression unit, and flue gas recirculation system, adding to its cost. In this study, we perform a techno-economic feasibility study of pressurized oxy-fuel combustion power systems. A number of reports and papers have been used to develop reliable models which can predict the costs of power plant components, its operation, and carbon dioxide capture specific systems, etc. We evaluate different metrics including capital investments, cost of electricity, and CO2 avoidance costs. Based on our cost analysis, we show that the pressurized oxy-fuel power system is an effective solution in comparison to other carbon dioxide capture technologies. The higher heat recovery displaces some of the regeneration components of the feedwater system. Moreover, pressurized operating conditions lead to reduction in the size of several other critical components. Sensitivity analysis with respect to important parameters such as coal price and plant capacity is performed. The analysis suggests a guideline to operate pressurized oxy-fuel combustion power plants in a more cost-effective way.

Analytical Formulation of the Performance of the Allam Power Cycle

2020 ◽  
Author(s):  
Yousef Haseli
Keyword(s):  
Power Plants ◽  
Fossil Fuels ◽  
Air Separation ◽  
Working Fluid ◽  
Inlet Temperature ◽  
Separation Unit ◽  
Power Cycle ◽  
Functional Relationships ◽  
Oxyfuel Combustion ◽  
Co2 Flow

Abstract Thermal power plants operating on fossil fuels emit a considerable amount of polluting gases including carbon dioxide and nitrogen oxides. Several technologies have been developed or under development to avoid the emissions of, mainly, CO2 that are formed as a result of air-fuel combustion. While post-combustion capture methods are viable solutions for reduction of CO2 in the existing power plants, implementation of the concept of oxyfuel combustion in future power cycles appears to be a promising technique for clean power generation from fossil fuels. A novel power cycle that employs oxyfuel combustion method has been developed by NET Power. Known as the Allam cycle, it includes a turbine, an air separation unit (ASU), a combustor, a recuperator, a water separator, CO2 compression with intercooling and CO2 pump. (Over 90% of the supercritical CO2 flow is recycled back to the cycle as the working fluid, and the rest is extracted for further processing and storage. The present paper introduces a simplified thermodynamic analysis of the Allam power cycle. Analytical expressions are derived for the net power output, optimum turbine inlet temperature (TIT), and the molar flowrate of the recycled CO2 flow. The study aims to provide a theoretical framework to help understand the functional relationships between the various operating parameters of the cycle. The optimum TIT predicted by the presented expression is 1473 K which is fairly close to that reported by the cycle developers.

Optimization of Thermodynamically Efficient Nominal 40 MW Zero Emission Pilot and Demonstration Power Plant in Norway

2005 ◽  
Author(s):  
Carl-W. Hustad ◽  
Inge Trondstad ◽  
Roger E. Anderson ◽  
Keith L. Pronske ◽  
Fermin Viteri
Keyword(s):  
Power Plant ◽  
Gas Turbine ◽  
Phase 1 ◽  
Clean Energy ◽  
Air Separation ◽  
Working Fluid ◽  
Maintenance Cost ◽  
Thermodynamic Efficiency ◽  
Separation Unit ◽  
Zero Emission

In Aug 2004 the Zero Emission Norwegian Gas (ZENG) project team completed Phase-1: Concept and Feasibility Study for a 40 MW Pilot & Demonstration (P&D) Plant, that is proposed will be located at the Energy Park, Risavika, near Stavanger in South Norway during 2008. The power plant cycle is based upon implementation of the natural gas (NG) and oxygen fueled Gas Generator (GG) (1500°F/1500 psi) successfully demonstrated by Clean Energy Systems (CES) Inc. The GG operations was originally tested in Feb 2003 and is currently (Feb 2005) undergoing extensive commissioning at the CES 5MW Kimberlina Test Plant, near Bakersfield, California. The ZENG P&D Plant will be an important next step in an accelerating path towards demonstrating large-scale (+200 MW) commercial implementation of zero-emission power plants before the end of this decade. However, development work also entails having a detailed commercial understanding of the techno-economic potential for such power plant cycles: specifically in an environment where the future penalty for carbon dioxide (CO2) emissions remains uncertain. Work done in dialogue with suppliers during ZENG Project Phase-1 has cost-estimated all major plant components to a level commensurate with engineering pre-screening. The study has also identified several features of the proposed power plant that has enabled improvements in thermodynamic efficiency from 37% up to present level of 44–46% without compromising the criteria of implementation using “near-term” available technology. The work has investigated: i. Integration between the cryogenic air separation unit (ASU) and the power plant. ii. Use of gas turbine technology for the intermediate pressure (IP) steam turbine. iii. Optimal use of turbo-expanders and heat-exchangers to mitigate the power consumption incurred for oxygen production. iv. Improved condenser design for more efficient CO2 separation and removal. v. Sensitivity of process design criteria to “small” variations in modeling of the physical properties for CO2/steam working fluid near saturation. vi. Use of a second “conventional” pure steam Rankine bottoming cycle. In future analysis, not all these improvements need necessarily be seen to be cost-effective when taking into account total P&D program objectives; thermodynamic efficiency, power plant investment, operations and maintenance cost. However, they do represent important considerations towards “total” optimization when designing the P&D Plant. We observe that Project Phase-2: Pre-Engineering & Qualification should focus on optimization of plant size with respect to total capital investment (CAPEX); and identification of further opportunities for extended technology migration from gas turbine environment that could also permit raised turbine inlet temperatures (TIT).

scholarly journals Design of a Semiclosed Cycle Gas Turbine With Carbon Dioxide-Argon as Working Fluid

1997 ◽  
Author(s):  
Inaki Ulizar ◽  
Pericles Pilidis
Keyword(s):  
Carbon Dioxide ◽  
Gas Turbine ◽  
Pressure Ratio ◽  
Air Separation ◽  
Working Fluid ◽  
Optimum Pressure ◽  
Low Efficiency ◽  
Nozzle Guide ◽  
Main Engine ◽  
No Emissions

The main performance features of a semiclosed cycle gas turbine with carbon dioxide-argon working fluid are described here. This machine is designed to employ coal synthetic gas fuel and to produce no emissions. The present paper outlines three tasks carried out. Firstly the selection of main engine variables, mainly pressure and temperature ratios. Then a sizing exercise is carried out where many details of its physical appearance are outlined. Finally the off-design performance of the engine is predicted. This two spool gas turbine is purpose built for the working fluid, so its physical characteristics reflect this requirement. The cycle is designed with a turbine entry temperature of 1650 K and the optimum pressure ratio is found to be around 60. Two major alternatives are examined, the simple and the precooled cycle. A large amount of nitrogen is produced by the air separation plant associated with this gas turbine and the coal gasifier. An investigation has been made on how to use this nitrogen to improve the performance of the engine by precooling the compressor, cooling the turbine nozzle guide vanes and using it to cool the delivery of the low pressure compressor. The efficiencies of the whole plant have been computed, taking into account the energy requirements of the gasifier and the need to dispose of the excess carbon dioxide. Hence the overall efficiencies indicated here are of the order of 40 percent. This is a low efficiency by current standards, but the fuel employed is coal and no emissions are produced.

scholarly journals Thermodynamic evaluation of supercritical oxy-type power plant with high-temperature three-end membrane for air separation

2014 ◽  
Vol 35 (3) ◽  
pp. 105-116 ◽  
Author(s):  
Janusz Kotowicz ◽  
Adrian Balicki ◽  
Sebastian Michalski
Keyword(s):  
Carbon Dioxide ◽  
High Temperature ◽  
Power Plant ◽  
Fluidized Bed ◽  
Air Separation ◽  
Thermodynamic Evaluation ◽  
Separation Unit ◽  
Air Separation Unit ◽  
Combustion Technology ◽  
Steam Parameters

Abstract Among the technologies which allow to reduce greenhouse gas emissions, mainly of carbon dioxide, special attention deserves the idea of ‘zero-emission’ technology based on boilers working in oxy-combustion technology. In the paper a thermodynamic analysis of supercritical power plant fed by lignite was made. Power plant consists of: 600 MW steam power unit with live steam parameters of 650 °C/30 MPa and reheated steam parameters of 670 °C/6 MPa; circulating fluidized bed boiler working in oxy-combustion technology; air separation unit and installation of the carbon dioxide compression. Air separation unit is based on high temperature membrane working in three-end technology. Models of steam cycle, circulation fluidized bed boiler, air separation unit and carbon capture installation were made using commercial software. After integration of these models the net electricity generation efficiency as a function of the degree of oxygen recovery in high temperature membrane was analyzed.

Use of Ion Transport Membrane for Oxygen Generation to Enhance the Performance of the Integrated Gasification Fuel Cell System

2019 ◽  
Author(s):  
Ji Hun Jeong ◽  
Ji Ho Ahn ◽  
Tong Seop Kim
Keyword(s):  
Carbon Dioxide ◽  
Fuel Cell ◽  
Ion Transport ◽  
Carbon Capture ◽  
Air Separation ◽  
Target System ◽  
Separation Unit ◽  
Ion Transport Membrane ◽  
Integrated Gasification ◽  
The Impact

Abstract Carbon capture and storage (CCS) processes have been studied to reduce carbon dioxide in power generation, especially in coal plants because they have been highlighted as the main source of carbon dioxide emission. In this study, the impact of oxygen supply method on the performance of the integrated gasification fuel cell (IGFC) with carbon capture was compared. The target system is based on a solid oxide fuel cell and uses the syngas produced by coal gasification as a fuel. In the reference IGFC, the oxygen required for gasification and oxy-combustion is separated through an air separation unit (ASU). On the other hand, in the system proposed in this study, oxygen is separated through an ion transport membrane (ITM). The temperature and pressure conditions, as well as the purity of the oxygen separated from the ITM, were assumed to be the same as those of the oxygen separated from the ASU, and the composition of the syngas was kept constant. The proposed system indicated a 4.0% increase in output and a 1.6%p increase in efficiency compared to that of the reference IGFC. In addition, performance was analyzed according to the operating condition of the ITM, and the change in performance within its possible operating range was found to be less than 0.3%, which was insignificant.

Chemical-Looping Combustion of Hard Coal: Autothermal Operation of a 1 MWth Pilot Plant

2016 ◽  
Vol 138 (4) ◽  
Author(s):  
Peter Ohlemüller ◽  
Jan-Peter Busch ◽  
Michael Reitz ◽  
Jochen Ströhle ◽  
Bernd Epple
Keyword(s):  
Carbon Dioxide ◽  
Carbon Dioxide Capture ◽  
Oxygen Carrier ◽  
Air Separation ◽  
Capture Efficiency ◽  
Chemical Looping Combustion ◽  
Hard Coal ◽  
Chemical Looping ◽  
Separation Unit ◽  
Autothermal Operation

Chemical-looping combustion (CLC) is an emerging carbon capture technology that is characterized by a low energy penalty, low carbon dioxide capture costs, and low environmental impact. To prevent the contact between fuel and air, an oxygen carrier is used to transport the oxygen needed for fuel conversion. In comparison to a classic oxyfuel process, no air separation unit is required to provide the oxygen needed to burn the fuel. The solid fuel, such as coal, is gasified in the fuel reactor (FR), and the products from gasification are oxidized by the oxygen carrier. There are promising results from the electrically heated 100 kWth unit at Chalmers University of Technology (Sweden) or the 1 MWth pilot at Technische Universität Darmstadt (Germany) with partial chemical-looping conditions. The 1 MWth CLC pilot consists of two interconnected circulating fluidized bed reactors. It is possible to investigate this process without electrically heating due to refractory-lined reactors and coupling elements. This work presents the first results of autothermal operation of a metal oxide CLC unit worldwide using ilmenite as oxygen carrier and coarse hard coal as fuel. The FR was fluidized with steam. The results show that the oxygen demand of the FR required for a complete conversion of unconverted gases was in the range of 25%. At the same time, the carbon dioxide capture efficiency was low in the present configuration of the 1 MWth pilot. This means that unconverted char left the FR and burned in the air reactor (AR). The reason for this is that no carbon stripper unit was used during these investigations. A carbon stripper could significantly enhance the carbon dioxide capture efficiency.

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