Thermodynamic analysis, energy integration and flowsheet improvement of a methanol absorption acid gas removal process

This paper analyses the thermodynamic performance and proposes different energy integration schemes for a methanol absorption based acid gas removal process, namely the Rectisol® process specifically designed for the selective removal of H2S and CO2 from coal derived syngas. The study consists of three major tasks: 1. Calibrating the PC-SAFT equation of state for MEOH-CO2-H2S-H2-CO mixtures at conditions relevant for the Rectisol® process. 2. Evaluating the thermodynamic performances and optimising the energy integration of the "Reference" scheme by means of "heat-cascade" based optimisation methodology. 3. Identifying attractive process modifications on the basis of Process Integration principles

Multi-objective Optimization of a Rectisol® Process

This work focuses on the design, simulation and optimization of a Rectisol®-based process tailored for the selective removal of H2S and CO2 from gasification derived synthesis gas. Such task is quite challenging due to the need of addressing simultaneously the process design, energy integration and utility design. The paper, starting from a Rectisol® configuration recently proposed by the authors, describes the models and the solution strategy used to carry out the multi-objective optimization with respect to exergy consumption, CO2 capture level and capital cost

Retrofitting partial oxyfuel and Integrated Ca-Looping technologies to an existing cement plant: a case study

The present document describes the potential retrofit of an existing cement plant with carbon capture technologies applied in two sequential steps. The pathway proposed consists in a first retrofit through partial oxyfuel followed by the integrated calcium looping (CaL) technology. This kind of applications may represent a promising strategy for the decarbonization route in the cement sector without introducing chemical solvents or special components, in particular for existing cement kilns that may need to be revamped. The cement plant selected for this study is the 0.5 Mtcem/y Colleferro facility owned by Italcementi-HeidelbergCement. This study analyses the mass & energy balances of the partial oxyfuel, and the integrated CaL process retrofitted to the existing cement plant. The results of the two CCS technologies are then compared in terms of CO2 emission reduction and energy consumption with the reference plant without CO2 capture. The scope of this analysis is to evaluate the impact of carbon capture technologies on the cement production process. The process simulation software Aspen Plus V10.0® has been employed to develop the model for the three different plant configurations (i.e., the base case w/o carbon capture, the partial oxyfuel mode, and the integrated CaL). The base case has been validated using field measurements coming directly from the Colleferro plant. From this process flow model, the two CCS technologies have been developed according to the specific process requirements. Results show that a maximum reduction in CO2 emissions of 92.4% is possible with the integrated CaL, while the partial oxyfuel enables to capture 71.7% of the CO2 generated in the plant

Techno-economic analysis of calcium looping processes for low CO2 emission cement plants

The scope of this work is to perform a techno-economic analysis of two Calcium Looping processes (CaL) for CO 2 capture in cement plants. Both tail-end CaL system with fluidized bed reactors and integrated CaL system with entrained flow reactors have been considered in the analysis. The calculation of the heat and mass balances and the economic analysis are consistent with the methodology defined in the framework of the H2020 Cemcap project. The analysis shows that the assessed CaL systems (especially the tail-end configuration) involve a significant increase of fuel consumption compared to a reference cement kiln without carbon capture. However, a large part of this additional energy input is exploited in a heat recovery steam cycle, which generates the electric power required to satisfy the consumption of the CO 2 capture auxiliaries (i.e. the power absorbed by the air separation and CO 2 compression and purification units). The integrated CaL process features a lower rise of equivalent fuel consumption (+59% compared to the reference) and a larger reduction of direct CO 2 emission (-93% compared to the reference). The specific primary energy consumption for CO 2 avoided (SPECCA), which takes into account also the indirect fuel consumption/savings and indirect emissions/avoided emissions due to electricity exchange (import/export) with the grid, ranges between 3.17–3.27 MJ LHV /kg CO2 for the integrated system vs. 3.76–4.42 MJ LHV /kg CO2 for tail-end cases, depending on the scenario considered for the grid electricity mix. The economic analysis highlights that CaL processes are capital intensive, which involve, roughly, a doubling of the Capex of the whole cement plant with CCS compared to a greenfield conventional cement plant. However, the obtained cost of CO 2 avoided is competitive with alternative technologies and ranges between about 52 €/t CO2 of the tail-end configuration and 58.6 €/t CO2 of the integrated one

Rate Based Model and Techno-Economic Assessment of a Post-Combustion Co2 Capture Unit Operating With Potassium Lysinate for NGCC Decarbonisation

The present work reports the results of process design and techno-economic assessment carried out on a CO2 capture unit operating with an aqueous solution of potassium Lysinate (LysK) at 43.7%w/w, in post-combustion arrangement for natural gas combined cycle (NGCC) decarbonisation. A dedicated rate-based model of the absorption unit has been defined and programmed in Matlab®. The techno-economic assessment of the reference natural gas combined cycle (frame-F gas turbine technology, 829.9 MWe without capture unit) coupled with a CO2 capture unit with the low-maturity LysK-based solvent has been carried out in order to estimate the energy penalty due to capture, the specific primary energy consumption per unit of CO2 avoided as well as economic indicators, such as overall capital costs, cost of electricity and the cost of CO2 avoided. The results are compared against a case study envisaging the same reference NGCC coupled with a commercial post-combustion capture solution working with 30%w/w aqueous monoethanolamine (MEA)

Thermodynamic analysis and numerical optimization of the NET Power oxy-combustion cycle

This paper presents a thorough thermodynamic analysis and optimization of the NET Power cycle (also called Allam cycle), a natural-gas-fired oxy-combustion cycle featuring nearly 100% CO2 capture level, very high net electric efficiency, and potentially near-zero emissions level. The main goals of this study are the systematic optimization of the cycle for the maximum efficiency, and the quantification of the effects of the modelling assumptions and equipment performance on the optimal cycle variables and efficiency. An Aspen Plus flow-sheet featuring accurate first-principle models of the main equipment units (including cooled turbine) and fluid properties (equation of state) has been developed. The influence of the cycle variables on the thermodynamic performance of the cycle is first assessed by means of sensitivity analyses. Then, the cycle variables, which maximize the net electric efficiency, are determined with PGS-COM, a black-box numerical optimization algorithm, linked to the simulation software. The corresponding maximum cycle efficiency is equal to 54.80% (with 100% CO2 capture), confirming the outstanding performance of the NET Power cycle. Moreover, the optimization indicates the existence of promising combinations of the cycle variables which lead to reduced component costs (due to the lower operating pressures and temperatures) of the most critical components, without considerably affecting the net electric efficiency. The analysis also indicates that the cooling medium temperature, the power consumption of the air separation unit, the effectiveness of the regenerator and the effectiveness of the turbine cooling system are the main factors influencing the cycle efficiency

Thermodynamic Optimization and Part-load Analysis of the NET Power Cycle

This paper performs the thermodynamic optimization and part-load analysis of the NET Power cycle (also called Allam cycle), a natural-gas-fired oxy-combustion cycle featuring 100% CO2 capture level, very high net electric efficiency, and potentially near-zero emissions level. To determine the maximum achievable cycle efficiency and optimal cycle variables, an Aspen Plus flowsheet including accurate first-principle models of the main equipment units has been developed and combined with a black-box optimization algorithm. The corresponding maximum cycle efficiency is equal to 55.35% (with 100% CO2 capture). Optimization-based sensitivity analyses are performed to explore the neighborhood of the maximum efficiency cycle design with the aim of finding combinations of the cycle variables which lead to reduced costs and thermo-mechanical stress of the most critical components. Finally, the part-load performance of the optimized NET Power cycle has been analyzed. Results indicate that in the load range 100-40% the cycle (excluding the ASU) features a considerably lower efficiency decrease compared to a standard combined cycle. This result, showing the possibility of efficiently operating the cycle also at part-loads, further increases the attractiveness of the NET Power cycle

Application of CCUS to the WtE sector

Waste management is a very scattered and complex system made up by different plants and facilities that treat / recover / valorize/ dispose different types of waste, e.g. Municipal Solid Waste (MSW) or Special Waste, based on the policies adopted in each country and the available technologies. While the management of MSW is the result of public planning, the management of special waste is typically dispersed and depends, for a large extent, on the initiatives of waste producers and private waste management companies. As a result, plants for MSW recovery are relatively large plants equipped with energy recovery facilities, whereas special waste is often incinerated in medium-small plants that feature energy recovery only in very limited cases. Therefore, an initial investigation on the potential integration of Waste to Energy (WtE) facilities with Carbon Capture Utilization and Storage (CCUS) should be focused on MSW and plants devoted to its treatment. Only in existing European WtE plants, there is a potential capture of 60-70 millions of tonnes of CO2 per year, and current large- scale projects prove the technical viability of carbon capture technologies in WtE environments. The paper summarizes the outcome of a study addressing all the opportunities and challenges related to the application of CCUS to the WtE sector. This study is executed by Wood, with the support of LEAP, and commissioned by IEAGHG . The main objective of the work is to carry out an initial overview of this CCS/CCU opportunity before proceeding to more detailed evaluations. The study is based on both literature information available in the public domain and results of surveys with WtE plants owners. Before evaluating a possible Carbon Capture application to the WtE sector, the study reviews the current status and diffusion of the WtE business and the plants distribution worldwide, focusing on ten representative countries: South Africa, USA, India, Japan, Germany, Italy, The Netherlands, UK, Norway, Australia. The selection considers several parameters: the urbanization level, the branching of the electricity/heat network, the presence of large scale WtE plants, the potential for CCS/CCU applied to WtE plants and the availability of potential destinations for the captured CO2. The main challenges in this kind of plants, focusing particularly on reliability, are also identified. The link between WtE and CO2 emissions is then investigated: firstly, the trends and the tools adopted by WtE plants in reducing CO2 emissions are analyzed; secondly, a lifecycle assessment approach is described and applied to the local contexts of the ten selected countries. The objective is to estimate the CO2 savings achievable through energy/materials recovery in a WtE plant, potentially leading to negative lifecycle emissions. The study then focuses on the possible integration of Carbon Capture within WtE facilities, collecting the information relevant to ongoing projects/initiatives aiming at this integration and identifying its potential challenges and opportunities in the design and the operation of the plants, based on the available literature. The most interesting aspects identified by this analysis are the energy integration and how the introduction of CO2 capture alters the energy balance of the WtE plant. There are also risks (related for example to financing, public acceptance, need for technology development) and opportunities (e.g. negative CO2 emissions, effective energy integration) that may arise from a WtE-CCUS integration. Considering that the presence of a regulatory framework on WtE and CCS can be an important driver for this kind of applications, a literature research is also carried out to provide an overview of the regulations applicable to the WtE and CCS sectors in the ten selected countries. Based on the various aspects analyzed throughout the course of the study, a tool is developed to estimate the potential of the CCUS/WtE integration, focusing on the local context of the ten selected counties. This presentation will include the methodology developed in this study, which aims to be a guide for future CCS projects in WtE plants