Life cycle environmental impact assessment method for carbon capture technology of coal-fired power plant

Abstract

The invention belongs to the technical field of life cycle evaluation methods, and particularly relates to a method for evaluating the environmental influence of a post-combustion carbon capture technology of a coal-fired power plant. Firstly, a system boundary of a researched case power plant is determined; secondly, collecting material, resource and energy consumption data of each link in the operation and construction stages of the power plant, and performing list analysis; then establishing an LCA evaluation model by using Gabi 10.0 software, and quantitatively calculating the environmental influence by using a CML 2001 method; and then selecting a life cycle energy footprint, a carbon footprint and a blue water footprint, and carrying out result analysis on the environmental sustainability of the coal-fired power plant applying the carbon capture technology in combination with an environmental influence evaluation result. According to the method, environmental influences of different carbon capture technologies are compared and analyzed, and scientific reference can be provided for stakeholders to select and deploy the carbon capture technologies.

Description

Technical Field

[0001] The present invention belongs to the technical field of life cycle assessment methods, and specifically relates to a life cycle environmental impact assessment method for carbon capture technology in a coal-fired power plant. Background Art

[0002] Coal is the largest source of man-made carbon dioxide emissions. Therefore, carbon emission reduction in the thermal power generation industry has always been a hot topic of international concern and a major challenge faced by researchers. An important way to achieve carbon emission reduction in the power industry is the application of low-carbon technologies. Carbon capture and storage (CCS) technology is an important technology for reducing greenhouse gas emissions and achieving near-zero scenarios, especially for deep decarbonization of fossil fuel power plants.

[0003] For the power industry, according to the order of carbon capture and combustion process, it can be divided into three types of technologies: pre-combustion capture, oxygen-enriched combustion and post-combustion capture. Among them, post-combustion capture is the preferred technology for reducing CO2 emissions in coal-fired power plants, because this method directly separates carbon dioxide from post-combustion flue gas without changing the original combustion device, and can be directly retrofitted into existing power plants to achieve carbon emission reduction.

[0004] Amine absorption is currently the most mature and widely used post-combustion carbon capture technology. Scholars at home and abroad are also exploring many other CCS technologies to evaluate their feasibility for future use in coal-fired power plants. Current research on carbon capture technology focuses on environmental impact assessment, especially the greenhouse gas emission reduction effect. However, in addition to environmental impact, it is also important to evaluate the life cycle energy footprint and life cycle water footprint of different carbon capture technologies, because energy, carbon and water are inseparable from each other. The assessment of energy-carbon-water footprint will help evaluate the environmental sustainability of the system and provide scientific reference for decision makers to select and deploy carbon capture technology. Summary of the invention

[0005] To solve the above problems, the present invention proposes a method for comparing and evaluating the life cycle environmental impacts of different post-combustion carbon capture technologies. From the power plant level, a bottom-up life cycle assessment (LCA) method is used to quantitatively analyze the environmental impacts, energy and water consumption of different carbon capture technologies.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A method for life cycle environmental impact assessment of carbon capture technology for coal-fired power plants, the steps are as follows:

[0008] (1) Determination of objectives and scope: Determine the system boundary and select different post-combustion carbon capture technologies. The system boundary is set as the construction and operation process of the power plant, including the production, processing and transportation of energy and raw materials required in the process. It is divided into six stages: coal transportation, coal mining and processing, power plant operation, chemical production, chemical transportation and construction.

[0009] (2) Inventory analysis: Taking the net power output of 1MWh of power plant as the functional unit, the input and output of the system are converted proportionally based on the functional unit; various input and output data of different carbon capture power plants throughout their life cycle are collected, sorted and summarized.

[0010] (3) Environmental impact assessment: Gabi 10.0 software was used to construct an LCA environmental impact model for coal-fired power plants using different carbon capture technologies. The characterization and normalization results were quantified using the CML 2001 model. The values ​​in Jan. 2016, World, year 2000 were used as the baseline values ​​to calculate the environmental impacts of various environmental indicators including abiotic depletion potential, global warming potential, acidification potential, eutrophication potential, freshwater aquatic ecotoxicity potential, terrestrial ecotoxicity potential, marine aquatic ecotoxicity potential, human toxicity potential, and ozone depletion potential.

[0011] (4) Energy footprint indicator: The life cycle energy input indicator is selected to represent the energy footprint. The life cycle energy input is defined as the ratio of the total energy required for each process in the life cycle of the system to the net power generation. For coal-fired power plants without and with different CCS technologies, the direct and indirect energy inputs of different sub-processes and the total life cycle energy input required to produce 1MWh of net electricity can be determined by estimating the life cycle energy input. The calculation method of life cycle energy input is shown in formula (1):

[0012]

[0013] Among them, LCEI represents the life cycle energy input, NEG represents the net electricity generated in the whole life cycle, and E i,j represents the energy input required for the process, and i and j represent the type of energy (i.e., energy in the form of electricity or fuel, such as coal, natural gas, etc.).

[0014] (5) Carbon footprint indicator: For the carbon footprint assessment, the performance indicator selected is life cycle greenhouse gas emissions, also known as global warming potential (GWP). First, the greenhouse gas emissions associated with each process (including fugitive emissions) are calculated in kg CO2 eq (kilograms of carbon dioxide equivalent), and then the total greenhouse gas emissions for the entire life cycle (obtained by adding the greenhouse gas emissions of each process) are divided by the net electricity generated over the entire life cycle to obtain the global warming potential in kg CO2 eq / MWh, as shown in formula (2). The assessment of life cycle greenhouse gas emissions helps to gain a deeper understanding of the contribution of direct and indirect greenhouse gas emissions, as well as to identify the links that contribute the most to greenhouse gas emissions.

[0015]

[0016] Where: Em a represents the CO2 equivalent emitted by a particular process 'a', while greenhouse gases other than CO2 emitted at various stages (such as CH4 and N2O) are converted into CO2 equivalent by multiplying their original emissions by their global warming potentials (CH4 = 29.8, N2O = 273).

[0017] (6) Blue water footprint indicator: Blue water usually refers to surface water or groundwater, and water consumption refers to the amount of water that is not returned to the original water source from which it was originally drawn. Blue water consumption refers to the amount of surface water or groundwater that is permanently lost in the form of evaporation losses, as well as the amount of surface water or groundwater consumed in various direct and indirect processes that occur throughout the supply chain of a specific system / product. The life cycle blue water consumption can provide an in-depth understanding of the direct water consumption at each stage as well as the indirect water consumption (water consumption in the upstream or downstream stages). The life cycle blue water consumption is defined by formula (3):

[0018]

[0019] Where LCBWC represents the life cycle blue water consumption, W b Represents the amount of blue water consumed by process "b".

[0020] Beneficial effects of the present invention:

[0021] (1) Quantitatively analyze and compare the environmental impact, energy and water consumption of different carbon capture technologies from a life cycle perspective, providing a scientific reference for enterprises to select carbon capture technologies.

[0022] (2) Analyze the environmental sustainability of the technology by integrating energy footprint, carbon footprint and water footprint indicators; and analyze the contribution ratio of the six different stages of the power plant life cycle from the perspectives of energy consumption, carbon emissions and blue water consumption, so as to provide a scientific basis for improving the technology level in a targeted manner while reducing environmental impact and energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is the technical roadmap of the present invention.

[0024] Figure 2 This is a system boundary diagram of a coal-fired power plant in this embodiment. DETAILED DESCRIPTION

[0025] The specific implementation of the present invention is further explained in combination with the technical scheme and the accompanying drawings.

[0026] The system boundary of the present invention is as follows Figure 1 As shown. Four different post-combustion carbon capture technologies were selected, including ethanolamine-based chemical absorption, ammonia-based chemical absorption, membrane separation and calcium circulation. At the same time, a coal-fired power plant without a carbon capture unit was selected as a baseline power plant for comparison. It is assumed that the four technologies are all based on the same 660MW supercritical coal-fired power plant, using bituminous coal. The power plant uses a low-nitrogen burner and selective catalytic reduction (SCR), electrostatic precipitator (ESP) and limestone wet desulfurization (FGD) devices. On this basis, this study takes a coal-fired power plant without a carbon capture unit as a baseline power plant (Base-PC) and considers the application of four different carbon capture technologies:

[0027] (1): Power plant using 30%wt ethanolamine organic solution absorption (MEA-PC)

[0028] (2) Ammonia-PC coal-fired power plant

[0029] (3): Power plant using double membrane separation method for carbon capture (MEM-PC)

[0030] (4): Power plants using calcium ring post-combustion capture (CaL-PC)

[0031] At the same time, the case power plant in the study is located in an area with rich coal resources and geological conditions for carbon dioxide storage, and the carbon dioxide transportation distance is short. The relevant parameters of carbon transportation and storage are set based on the field survey. The operating life of the power plant and carbon capture, transportation and storage equipment is set to 30 years, with an annual operation time of 6574 hours. According to the operating years of the equipment, the building material consumption of all infrastructure is converted. In addition, the heat and power consumption of all internal equipment of the power plant, such as cooling towers, SCR, ESP, wet desulfurization and carbon capture units, are provided by the power plant itself, and the remaining power is exported to the power grid.

[0032] Based on the field survey and the simulation results of the integrated environmental control model, the operating performance and emission data of the power plant were obtained. The original data of the rest of the power plant construction phase were obtained from relevant literature, Gabi 10.0 software database, and Ecoinvent 3.1 database. Diesel trucks were used to transport construction materials, with an average transportation distance of 69 km. 70% of coal was transported by rail and 30% by road, with a transportation distance of 650 km. Other chemicals consumed in the operation phase were transported by road (diesel truck) with a distance of 150 km. The LCA environmental impact models of 5 different coal-fired power plants were constructed using Gabi10.0 software, and 10 different environmental impacts were discussed: abiotic depletion potential (ADP), global warming potential (GWP), acidification potential (AP), eutrophication potential (EP), freshwater aquatic ecotoxicity potential (FAETP), terrestrial ecotoxicity potential (TEP), marine aquatic ecotoxicity potential (MAETP), human toxicity potential (HTP), and ozone depletion potential (ODP).

[0033] Based on the results of the environmental impact assessment, the energy footprint, carbon footprint and blue water footprint of the case power plant are calculated, as shown in Table 1. From the perspective of specific indicators, the application of carbon capture technology has significantly reduced the GWP and AP indicators by 61.3%-77.6% and 66.2%-83.5% respectively, while other environmental impact categories have increased to varying degrees. e Other environmental impact indicators are the lowest among the four carbon capture power plants, and the EP and TETP indicators of CaL-PC are even lower than those of the baseline power plant. An in-depth analysis of the contribution of different life cycle stages to environmental impacts shows that coal mining and processing play a leading role in various environmental impacts, followed by power plant operation and coal transportation stages, which contribute more to various environmental impacts, accounting for more than 80% in total. Among the four carbon capture power plants, the calcium cycle coal-fired power plant has the lowest energy, carbon and blue water footprint. Compared with the baseline power plant without carbon capture equipment, the calcium cycle carbon capture power plant can achieve more than 75% greenhouse gas emissions reduction while ensuring the minimum increase in energy footprint and blue water footprint. Since the calcium cycle carbon capture equipment can output additional auxiliary power, the calcium cycle carbon capture technology can not only effectively reduce carbon dioxide emissions and increase the power generation capacity of the power plant, but also from the perspective of life cycle sustainability, the calcium cycle method is the most advantageous.

[0034] By quantitatively analyzing the environmental impacts and energy and water footprints of different post-combustion carbon capture technologies, the present invention can clarify the carbon footprint reduction and other environmental impact changes brought about by the application of carbon capture technology. It can also comprehensively compare different carbon capture technologies based on energy, carbon and water footprints, provide scientific advice to decision makers for technology selection and deployment, and help the thermal power industry achieve carbon emission reductions.

[0035] Table 1 Environmental impact assessment results and energy footprint and water footprint indicators of coal-fired power plants

[0036]

Claims

1. A method for life cycle environmental impact assessment of carbon capture technology in coal-fired power plants, characterized in that: Here are the steps: (1) Determination of objectives and scope: Different post-combustion carbon capture technologies are selected. The system boundary is the construction and operation process of the power plant, including the production, processing and transportation of raw materials required in the process. It is divided into six stages: coal transportation, coal mining and processing, power plant operation, chemical production, chemical transportation and construction stage; (2) Inventory analysis: Taking the net power output of 1MWh of power plant as the functional unit, the input and output of the system are converted proportionally according to the functional unit; various input and output data of different carbon capture power plants throughout their life cycle are collected, sorted and summarized; (3) Environmental impact assessment: Gabi 10.0 software was used to construct an LCA environmental impact model for coal-fired power plants using different carbon capture technologies. The characterization and normalization results were quantified using the CML 2001 model. The values ​​in Jan. 2016, World, year 2000 were used as the baseline values ​​to calculate the environmental impacts of various environmental indicators, including abiotic depletion potential, global warming potential, acidification potential, eutrophication potential, freshwater aquatic ecotoxicity potential, terrestrial ecotoxicity potential, marine aquatic ecotoxicity potential, human toxicity potential, and ozone depletion potential. (4) Energy footprint indicator: The life cycle energy input indicator is selected to represent the energy footprint. The definition of life cycle energy input is the ratio of the total energy required for each process in the life cycle of the system to the net power generation. The calculation method of life cycle energy input is shown in formula (1): Among them, LCEI represents the life cycle energy input, NEG represents the net electricity generated in the whole life cycle, and E i,j represents the energy input required for the process, i and j represent the type of energy, i.e., energy in the form of electricity or fuel; (5) Carbon footprint indicator: For carbon footprint assessment, the performance indicator selected is life cycle greenhouse gas emissions, also known as global warming potential (GWP). First, the greenhouse gas emissions associated with each process are calculated in kg CO2 eq. Then, the total greenhouse gas emissions over the entire life cycle are divided by the net electricity generated over the entire life cycle to obtain the global warming potential in kg CO2 eq / MWh, as shown in formula (2): Where: Em a represents the CO2 equivalent emitted by a specific process a, while greenhouse gases other than CO2 emitted at each stage are converted into CO2 equivalent by multiplying their original emissions by their global warming potential; (6) Blue water footprint indicator: Blue water usually refers to surface water or groundwater. Water consumption refers to the amount of water that is not returned to the original water source from which it was originally drawn. Blue water consumption refers to the amount of surface water or groundwater that is permanently lost in the form of evaporation, etc., as well as the amount of surface water or groundwater consumed in various direct and indirect processes throughout the supply chain of a specific system / product. Life cycle blue water consumption is defined by formula (3): Where LCBWC represents the life cycle blue water consumption, W b Represents the amount of blue water consumed in process b.

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