Methodology for the optimal design of an integrated sugarcane distillery and cogeneration process for ethanol and power production

The application of systematic methodologies for the optimal design of integrated processes has seen increased interest in literature, namely for bioprocesses. The development and application of such a methodology to ethanol and power production from sugarcane and leaves, in a combined distillery and cogeneration plant is investigated in this article. The methodology breaks down as follows: process simulation, heat integration and thermo-economic evaluation, bi-objective multi-variable evolutionary optimization, and process selection. The objective functions are exergy efficiency and capital cost, whereas the selection criterion is the maximization of the Net Present Value (NPV). This choice was motivated by the variation in process related market parameters and their impact on profitability. Optimization generated 31 optimal trade-off solutions with better results than literature. Exergy efficiency ranged between 37.6% and 41.7% and capital costs between 155 M $and 210 M$ . Process selection led to a single configuration maximizing NPV for four economic scenarios. The configuration's exergy efficiency and capital costs were equal to 40.63% and 163 M$. This point presented an optimal compromise between heat integration and capital costs. This article provides a breakthrough in the application of this methodology, to the investigated process specifically. (C) 2016 Elsevier Ltd. All rights reserved.

Methodology for the optimal design of an integrated first and second generation ethanol production plant combined with power cogeneration

Rami Bechara, François Maréchal, Jean-Marc Schweitzer

The application of methodologies for the optimal design of integrated processes has seen increased interest in literature. This article builds on previous works and applies a systematic methodology to an integrated first and second generation ethanol production plant with power cogeneration. The methodology breaks into process simulation, heat integration, thermo-economic evaluation, exergy efficiency vs. capital costs, multi-variable, evolutionary optimization, and process selection via profitability maximization. Optimization generated Pareto solutions with exergy efficiency ranging between 39.2% and 44.4% and capital costs from 210 M

to 390 M

. The Net Present Value was positive for only two scenarios and for low efficiency, low hydrolysis points. The minimum cellulosic ethanol selling price was sought to obtain a maximum NPV of zero for high efficiency, high hydrolysis alternatives. The obtained optimal configuration presented maximum exergy efficiency, hydrolyzed bagasse fraction, capital costs and ethanol production rate, and minimum cooling water consumption and power production rate.

2016

Methodology for the design and comparison of optimal production configurations of first and first and second generation ethanol with power

Rami Bechara, François Maréchal, Jean-Marc Schweitzer

This article applies a systematic methodology to the optimization and comparison of two sugarcane conversion processes of great potential: the production of first generation ethanol and electricity in an integrated distillery and cogeneration plant (1G+COGEN), and the production of first and second generation ethanol and electricity in an integrated distillery, hydrolysis and cogeneration plant (1G+2G+COGEN). The employed method consisted of rigorous process simulation, heat integration, thermo-economic evaluation, bi-objective, exergy efficiency vs. capital cost, optimization and selection via profitability maximization. The exergy efficiency of optimal 1G+COGEN and 1G+2G+COGEN configurations ranged from 37.5% to 41.7% and from 41.8% and 44.42% respectively. Fixed capital increased with exergy efficiency from USD 155 million to USD 209 million and from USD 252 million to USD 393 million respectively. Ethanol production rate averaged at 81.4 L/ton cane (TC) for 1G+COGEN configurations whereas it increased with exergy efficiency to 106 L/TC for 1G+2G+COGEN schemes. Electricity production increased for the first from 122 to 188 kW h/TC and decreased for the second from 180 kW h/TC to 92 kW h/TC. 1G+COGEN schemes presented higher NPV values with a minimum difference of $45 million than 1G+2G+COGEN schemes, with the maximum at an exergy efficiency of 40.65%. Equal profitability was obtained when second generation ethanol selling prices were set at values two to four times greater than the standard, with the most profitable 1G+2G+COGEN configuration having the greater efficiency at 44.4%. A comparison of the two schemes displayed key similarities relating to vapor bleeding, heat integration, backward integrated distillation, high boiler pressure and superheating temperature, but also witnessed discrepancies in the evaporators and steam turbines. This work provides a stepping stone in the design of sustainable sugarcane conversion processes, and serves as an example for the efficiency of such methods for the conception of sustainable energy systems.

2016

Evaluation of a Combined Cycle Setup for Solar Tower Power Plants

James Spelling

As our awareness of the dangers of global climate change grows, the development of new renewable energy technologies is of primary importance in the effort to reduce emissions of carbon dioxide and other greenhouse gases. Rapid increases in the price of oil and worries about the stability and security of the extraction of fossil fuels have lead to renewed interest in the development of local energy sources, thereby reducing dependence on foreign sources. Amid the plethora of option available, one of the more promising solutions is the increased use of concentrating solar thermal power. Solar thermal power generation shows great potential for supplying the base electricity needs of numerous countries in the sun-belt regions, stretching from the tropics to the Mediterranean. This has lead to a recent renewal in the development of such systems, most notably with the construction of the PS10 and PS20 central receiver power plants in Spain. However, all currently existing solar thermal power plants have been based around the use of Rankine or steam turbine cycles, which are limited in the efficiencies they can achieve. In order to make better use of the Sun’s energy, higher efficiency cycles should be used. Recent developments in the field of high temperature solar receivers [13] have made it possible to imagine the use of solar thermal energy to drive gas turbine units, potentially allowing the use of combined cycle setups in solar thermal power plants. In order to evaluate the potential improvement in efficiency that can be achieved by using combined cycles in solar thermal power plants, a detailed simulation of such a setup will be performed. By taking into account the requirements of thermal energy storage and the design of the necessary heat exchangers, an objective evaluation of the performance of the combined cycle can be obtained. As a key element in the energy conversion process, particular attention will be given to the modelling and simulation of the high temperature receiver. Due to the highly variable nature of the solar flux, the performance of the receiver will be evaluated over a range of operating points. In order to obtain a detailed breakdown of the sources of losses and irreversibilities within the system, a complete exergy balance will be performed on the power plant. Combined with the standard energy balance, this analysis will allow identification of the key areas for improvement in the design of solar thermal power plants. Finally, in order to determine whether such a setup is economically viable, the construction, operation and maintenance costs will be evaluated in order to predict the levelised energy cost associated with electricity production in a combined cycle plant.

2008

Methodology for the design and comparison of optimal production configurations of first and first and second generation ethanol with power

Rami Bechara, François Maréchal, Jean-Marc Schweitzer

2016

Evaluation of a Combined Cycle Setup for Solar Tower Power Plants

James Spelling

2008

Methodology for the optimal design of an integrated first and second generation ethanol production plant combined with power cogeneration

Rami Bechara, François Maréchal, Jean-Marc Schweitzer

to 390 M

2016