Lidia Lombardi

Life cycle assessment comparison of technical solutions for CO2 emissions reduction in power generation

An exergetic life cycle assessment (ELCA) and a classical environmental life cycle assessment (LCA) have been performed for three carbon dioxide low emission power cycles. The configuration of the power cycles are: a semi-closed gas turbine combined cycle with CO2 reduction from the exhausts by means of amine solution chemical absorption; an integrated gasification combined cycle with CO2 reduction from the synthesis gas by means of amine solution chemical absorption; and O2/CO2 innovative cycle where, burning methane in oxygen, CO2 becomes the cycle working fluid, and the CO2 excess, produced in the combustion, is removed in liquid phase without any additional system. The LCA is mainly focussed on CO2 production during the three phases of construction, operation and dismantling of the plants. This is necessary to verify if the process is effective in terms of CO2 reduction. Besides the classic LCA, also an ELCA was performed, whose aim is to assess the cost, in terms of exergy losses, of the life cycle of the plants. The CO2 reduction is effective during the lifetime, and a sort of classification of the studied plant is obtained.

A review of technologies and performances of thermal treatment systems for energy recovery from waste

The aim of this work is to identify the current level of energy recovery through waste thermal treatment. The state of the art in energy recovery from waste was investigated, highlighting the differences for different types of thermal treatment, considering combustion/incineration, gasification and pyrolysis. Also different types of wastes - Municipal Solid Waste (MSW), Refuse Derived Fuel (RDF) or Solid Refuse Fuels (SRF) and some typologies of Industrial Waste (IW) (sludge, plastic scraps, etc.) - were included in the analysis. The investigation was carried out mainly reviewing papers, published in scientific journals and conferences, but also considering technical reports, to gather more information. In particular the goal of this review work was to synthesize studies in order to compare the values of energy conversion efficiencies measured or calculated for different types of thermal processes and different types of waste. It emerged that the dominant type of thermal treatment is incineration associated to energy recovery in a steam cycle. When waste gasification is applied, the produced syngas is generally combusted in a boiler to generate steam for energy recovery in a steam cycle. For both the possibilities--incineration or gasification--co-generation is the mean to improve energy recovery, especially for small scale plants. In the case of only electricity production, the achievable values are strongly dependent on the plant size: for large plant size, where advanced technical solutions can be applied and sustained from an economic point of view, net electric efficiency may reach values up to 30-31%. In small-medium plants, net electric efficiency is constrained by scale effect and remains at values around 20-24%. Other types of technical solutions--gasification with syngas use in internally fired devices, pyrolysis and plasma gasification--are less common or studied at pilot or demonstrative scale and, in any case, offer at present similar or lower levels of energy efficiency.

Life cycle assessment of biogas upgrading technologies

This article evaluates the life cycle assessment (LCA) of three biogas upgrading technologies. An in-depth study and evaluation was conducted on high pressure water scrubbing (HPWS), as well as alkaline with regeneration (AwR) and bottom ash upgrading (BABIU), which additionally offer carbon storage. AwR and BABIU are two novel technologies that utilize waste from municipal solid waste incinerators - namely bottom ash (BA) and air pollution control residues (APC) - and are able to store CO(2) from biogas through accelerated carbonation processes. These are compared to high pressure water scrubbing (HPWS) which is a widely used technology in Europe. The AwR uses an alkaline solution to remove the CO(2) and then the solution - rich in carbonate and bicarbonate ions - is regenerated through carbonation of APC. The BABIU process directly exposes the gas to the BA to remove and immediately store the CO(2), again by carbonation. It was determined that the AwR process had an 84% higher impact in all LCA categories largely due to the energy intensive production of the alkaline reactants. The BABIU process had the lowest impact in most categories even when compared to five other CO(2) capture technologies on the market. AwR and BABIU have a particularly low impact in the global warming potential category as a result of the immediate storage of the CO(2). For AwR, it was determined that using NaOH instead of KOH improves its environmental performance by 34%. For the BABIU process the use of renewable energies would improve its impact since accounts for 55% of the impact.

Life cycle assessment (LCA) and exergetic life cycle assessment (ELCA) of a semi-closed gas turbine cycle with CO2 chemical absorption

Abstract An exergetic life cycle assessment (ELCA) and a classical environmental life cycle assessment (LCA) has been performed for a carbon dioxide low emission power cycle. The configuration of the power cycle is a semi-closed gas turbine combined cycle (SCGT/CC) which allows increasing of the CO 2 concentration in the flue gases. The decreasing CO 2 Plant (DeCO 2 Plant) achieves a CO 2 reduction of 85% by means of chemical absorption with a blended solution of amines. The LCA is mainly focussed on CO 2 production during the three phases of construction, operation and dismantling of the complete SCGT/CC + DeCO 2 plant. This is necessary to verify if the process is effective in terms of CO 2 reduction. Besides the classic LCA, an ELCA was also performed, whose aim was to assess the cost of the life cycle of the plant in terms of exergy losses. The results are quite encouraging: the CO 2 reduction is effective during the life time.

Analysis of energy recovery potential using innovative technologies of waste gasification

In this paper, two alternative thermo-chemical processes for waste treatment were analysed: high temperature gasification and gasification associated to plasma process. The two processes were analysed from the thermodynamic point of view, trying to reconstruct two simplified models, using appropriate simulation tools and some support data from existing/planned plants, able to predict the energy recovery performances by process application. In order to carry out a comparative analysis, the same waste stream input was considered as input to the two models and the generated results were compared. The performances were compared with those that can be obtained from conventional combustion with energy recovery process by means of steam turbine cycle. Results are reported in terms of energy recovery performance indicators as overall energy efficiency, specific energy production per unit of mass of entering waste, primary energy source savings, specific carbon dioxide production.

Pilot scale evaluation of the BABIU process – Upgrading of landfill gas or biogas with the use of MSWI bottom ash

Biogas or landfill gas can be converted to a high-grade gas rich in methane with the use of municipal solid waste incineration bottom ash as a reactant for fixation of CO2 and H2S. In order to verify results previously obtained at a laboratory scale with 65-90 kg of bottom ash (BA), several test runs were performed at a pilot scale, using 500-1000 kg of bottom ash and up to 9.2 Nm(3)/h real landfill gas from a landfill in the Tuscany region (Italy). The input flow rate was altered. The best process performance was observed at a input flow rate of 3.7 Nm(3)/(htBA). At this flow rate, the removal efficiencies for H2S were approximately 99.5-99%.

The Recuperative Auto Thermal Reforming and Recuperative Reforming Gas Turbine Power Cycles With CO2 Removal—Part II: The Recuperative Reforming Cycle

The relatively innovative gas turbine based power cycles R-ATR and R-REF (recuperative-auto thermal reforming GT cycle and recuperative-reforming GT cycle) here proposed, are mainly aimed to allow the upstream CO 2 removal by the natural gas fuel reforming. The second part of the paper is dedicated to the R-REF cycle : the power unit is a gas turbine (GT), fuelled with reformed and CO 2 cleaned gas, obtained by the addition of several sections to the simple GT cycle, mainly: ○ reformer section (REF), where the reforming reactions of methane fuel with steam are accomplished: the necessary heat is supplied partially by the exhausts cooling and, partially, with a post-combustion, ○ water gas shift reactor (WGSR), where the reformed fuel is, shifted into CO 2 and H 2 with the addition of water, and ○ CO 2 removal unit for the CO 2 capture from the reformed and shifted fuel. No water condensing section is adopted for the R-REF configuration. Between the main components, several heat recovery units are applied, together with GT cycle recuperator, compressor intercooler, and steam injection into the combustion chamber. The CO 2 removal potential is close to 90% with chemical absorption by an accurate choice of amine solution blend: the heat demand for amine regeneration is completely self-sustained by the power cycle. The possibility of applying steam blade cooling (the steam is externally added) has been investigated: in these conditions, the R-REF has shown efficiency levels close to 43-44%. High values of specific work have been observed as well (around 450-500 kJ/kg). The efficiency is slightly lower than that found for the R-ATR solution, and 2-3% lower than CRGTs with CO 2 removal and steam bottoming cycle, not internally recuperated. If compared with these, the R-REF offers higher simplicity due to absence of the steam cycle, and can be regarded as an improvement to the simple GT In this way. at least 5-6 points efficiency can be gained, together with high levels of CO 2 removal. The effects of the reformed fuel gas composition, temperature, and pressure on the amine absorption system for the CO 2 removal have been investigated, showing the beneficial effects of increasing pressure (i.e., pressure ratio) on the specific heat demand.

Performance of a biogas upgrading process based on alkali absorption with regeneration using air pollution control residues

This work analyzes the performance of an innovative biogas upgrading method, Alkali absorption with Regeneration (AwR) that employs industrial residues and allows to permanently store the separated CO2. This process consists in a first stage in which CO2 is removed from the biogas by means of chemical absorption with KOH or NaOH solutions followed by a second stage in which the spent absorption solution is contacted with waste incineration Air Pollution Control (APC) residues. The latter reaction leads to the regeneration of the alkali reagent in the solution and to the precipitation of calcium carbonate and hence allows to reuse the regenerated solution in the absorption process and to permanently store the separated CO2 in solid form. In addition, the final solid product is characterized by an improved environmental behavior compared to the untreated residues. In this paper the results obtained by AwR tests carried out in purposely designed demonstrative units installed in a landfill site are presented and discussed with the aim of verifying the feasibility of this process at pilot-scale and of identifying the conditions that allow to achieve all of the goals targeted by the proposed treatment. Specifically, the CO2 removal efficiency achieved in the absorption stage, the yield of alkali regeneration and CO2 uptake resulting for the regeneration stage, as well as the leaching behavior of the solid product are analyzed as a function of the type and concentration of the alkali reagent employed for the absorption reaction.

The Recuperative-Auto Thermal Reforming and the Recuperative-Reforming Gas Turbine Power Cycles With CO2 Removal—Part I: The Recuperative-Auto Thermal Reforming Cycle

The relatively innovative gas turbine based power cycles R-ATR and R-REF (Recuperative-Auto Thermal Reforming GT cycle and Recuperative-Reforming GT cycle) here proposed are mainly aimed to allow the upstream CO 2 removal by the way of natural gas fuel reforming. The power unit is a gas turbine (GT), fueled with reformed and CO 2 cleaned syngas produced by adding some basic sections to the simple GT cycle: ○ auto thermal reforming (ATR) for the R-ATR solution, where the natural gas is reformed into CO, H 2 , CO 2 , H 2 O, and CH 4 ; this endothermic process is completely sustained by the heat released from the reactions between the primary fuel (CH 4 ), exhausts and steam. ○ water gas shift reactor (WGSR), where the reformed fuel is, as far as possible, shifted into CO 2 and H 2 by the addition of water. ○ water condensation, in order to remove a great part of the fuel gas humidity content (this water is totally reintegrated into the WGSR). ○ CO 2 removal unit for the CO 2 capture from the reformed fuel. Among these main components, several heat recovery units are inserted, together with GT cycle recuperator, compressor intercooler, and steam injection in combustion chamber. The CO 2 removal potential is close to 90% with chemical scrubbing using an accurate choice of amine solution blend: the heat demand is completely provided by the power cycle itself. The possibility of applying steam blade cooling by partially using the water released from the dehumidifier downstream the WGSR has been investigated: in these conditions, the R-ATR has shown an efficiency range of 44-46%. High specific work levels have also been observed (around 450-550 kJ/kg). These efficiency values are satisfactory, especially if compared with ATR combined cycles with CO 2 removal, more complex due to the steam power section. If regarded as an improvement to the simple GT cycle, R-ATR shows an interesting potential if directly applied to a current GT model; however, partial redesign with respect to the commercially available version is required. Finally, the effects of the reformed fuel gas composition and conditions on the amine CO 2 absorption system have been investigated, showing the beneficial effects of increasing pressure (i.e., pressure ratio) on the thermal load per kg of removed CO 2 .

The R-ATR and the R-REF Gas Turbine Power Cycles With CO2 Removal: Part 1 — The R-ATR Cycle

The relatively innovative gas turbine based power cycles R–ATR and R–REF (Recuperative – Auto Thermal Reforming GT cycle and Recuperative–Reforming GT cycle) here proposed are mainly aimed to allow the upstream CO2 removal by the way of natural gas fuel reforming. The power unit is a Gas Turbine (GT), fuelled with reformed and CO2 cleaned syngas produced by adding some basic sections to the simple GT cycle: • Auto Thermal Reforming (ATR) for the R-ATR solution, where the natural gas is reformed into CO, H2 , CO2 , H2 O and CH4 ; this endothermic process is completely sustained by the heat released from the reactions between the primary fuel (CH4 ), exhausts and steam. • Water Gas Shift Reactor (WGSR), where the reformed fuel is, as far as possible, shifted into CO2 and H2 by the addition of water. • Water Condensation, in order to remove a great part of the fuel gas humidity content (this water is totally reintegrated into the WGSR). • CO2 removal unit for the CO2 capture from the reformed fuel. Among these main components, several heat recovery units are inserted, together with GT Cycle recuperator, compressor intercooler and steam injection in combustion chamber. The CO2 removal potential is close to 90% with chemical scrubbing using an accurate choice of amine solution blend: the heat demand is completely provided by the power cycle itself. The possibility of applying steam blade cooling by partially using the water released from the dehumidifier downstream the WGSR has been investigated: in these conditions, the R-ATR has shown an efficiency range of 44–46%. High specific work levels have also been observed (around 450–550 kJ/kg). These efficiency values are satisfactory, especially if compared with ATR combined cycles with CO2 removal, more complex due to the steam power section. If regarded as an improvement to the simple GT cycle, R-ATR shows an interesting potential if directly applied to a current GT model; however partial redesign with respect to the commercially available version is required. Finally, the effects of the reformed fuel gas composition and conditions on the amine CO2 absorption system have been investigated, showing the beneficial effects of increasing pressure (i.e. pressure ratio) on the thermal load per kg of removed CO2 .Copyright