A coal-fired power plant integrated with biomass co-firing and CO2 capture for zero carbon emission

A promising scheme for coal-fired power plants in which biomass co-firing and carbon dioxide capture technologies are adopted and the low-temperature waste heat from the CO₂ capture process is recycled to heat the condensed water to achieve zero carbon emission is proposed in this paper. Based on a 660 MW supercritical coal-fired power plant, the thermal performance, emission performance, and economic performance of the proposed scheme are evaluated. In addition, a sensitivity analysis is conducted to show the effects of several key parameters on the performance of the proposed system. The results show that when the biomass mass mixing ratio is 15.40% and the CO₂ capture rate is 90%, the CO₂ emission of the coal-fired power plant can reach zero, indicating that the technical route proposed in this paper can indeed achieve zero carbon emission in coal-fired power plants. The net thermal efficiency decreases by 10.31%, due to the huge energy consumption of the CO₂ capture unit. Besides, the cost of electricity (COE) and the cost of CO₂ avoided (COA) of the proposed system are 80.37 $/MWh and 41.63 $/tCO₂, respectively. The sensitivity analysis demonstrates that with the energy consumption of the reboiler decreasing from 3.22 GJ/tCO₂ to 2.40 GJ/ tCO₂, the efficiency penalty is reduced to 8.67%. This paper may provide reference for promoting the early realization of carbon neutrality in the power generation industry.     

下吸式固定床的生物质H2O/CO2气化数值模拟研究

利用Aspen Plus 软件建立干桦木屑在下吸式固定床气化炉中的气化模型,模拟值与文献实验值吻合良好。利用Aspen Plus的灵敏度分析模块模拟分别以水蒸气（H₂O）和二氧化碳（CO₂）为气化剂时气化剂/生物质碳比（GC值）对气化结果的影响,并结合H₂O、CO₂各自的特点研究其复合气化。结果表明,H₂O气化时可获得富氢煤气,但其净CO₂排放量较高;CO₂气化时碳转化率及冷煤气效率较低,但净CO₂排放量较低;H₂O、CO₂复合气化使碳转化率及冷煤气效率略有降低,但可有效减少气化系统中的净CO₂排放量。     

Multi-objective optimization of an advanced combined cycle power plant including CO2 separation options

This paper illustrates a methodology developed to facilitate the analysis of complex systems characterized by a large number of technical, economical and environmental parameters. Thermo-economic modeling of a natural gas combined cycle including CO₂ separation options has been coupled within a multi-objective evolutionary algorithm to characterize the economic and environmental performances of such complex systems within various contexts.

The method has been applied to a case of power generation in Germany. The optimum options for system integration under different boundary conditions are revealed by the Pareto Optimal Frontiers. Results show the influence of the configuration and technical parameters on the electrical efficiencies of the Pareto optimal plants and their sub-systems. The results provide information on the relationship between power generation cost and CO₂ emissions, and allow sensitivity analyses of important economical parameters like natural gas and electricity prices. Such a tool is of interest for power generation technology suppliers, for utility owners or for project investors, and for policy makers in the context of CO₂ mitigation schemes including emission trading.     

Short-term impact of green certificates and CO2 emissions trading in the Swedish district heating sector

Swedish district-heating (DH) systems use a wide range of energy sources and technologies for heat-and-power generation. This provides the DH utilities with major flexibility in changing their fuel and technology mix when the economic conditions for generation change. Two recently introduced policy instruments have changed the DH utilities’ costs for generation considerably; the tradable green-certificate (TGC) scheme introduced in 2003 in Sweden, and the tradable greenhouse-gas emission permit (TEP) scheme introduced in the EU on January 1, 2005. The objective of this study is to analyse how these two trading schemes impact on the operation of the Swedish DH sector in terms of changes in CHP generation, CO₂ emissions, and operating costs. The analysis was carried out by comparing the most cost-effective operation for the DH utilities, with and without, the two trading schemes applied, using a model that handles the Swedish DH-sector system-by-system. It was found that the volume of renewable power generated in CHP plants only increased slightly owing to the TGC scheme. The TGC and the TEP schemes in force together, however, nearly doubled the renewable power-generation. CO₂ emissions from the DH sector may either increase or decrease depending on the combination of TGC and TEP prices. The overall CO₂ emissions from the European power-generation sector would, however, be reduced for all price combinations assuming that increased Swedish CHP generation replaces coal-condensing power (coal-fired plants with power generation only) in other European countries. The trading schemes also lower the operational costs of the DH sector since the cost increase owing to the use of more expensive fuels and the purchase of TEPs is outweighed by the increased revenues from sales of electricity and TGCs.     

Environmental,social, and economic assessment of energy utilization of crop residue in China

This paper aims to discuss an environmental, social, and economic analysis of energy utilization of crop residues from life cycle perspectives in China. The methodologies employed to achieve this objective are environmental life cycle assessment (E-LCA), life cycle cost (LCC), and social life cycle assessment (S-LCA). Five scenarios are developed based on the conversion technologies and final bioenergy products. The system boundaries include crop residue collection, transportation, pre-treatment, and conversion process. The replaced amounts of energy are also taken into account in the E-LCA analysis. The functional unit is defined as 1 MJ of energy produced. Eight impact categories are considered besides climate change in E-LCA. The investment capital cost and salary cost are collected and compared in the life cycle of the scenarios. Three stakeholders and several subcategories are considered in the S-LCA analysis defined by UNEP/SETAS guidelines. The results show that the energy utilization of crop residue has carbon emission factors of 0.09–0.18 kg (CO₂ eq per 1 MJ), and presents a net carbon emissions reduction of 0.03–0.15 kg (CO₂ eq per 1 MJ) compared with the convectional electricity or petrol, but the other impacts should be paid attention to in the biomass energy scenarios. The energy utilization of crop residues can bring economic benefit to local communities and the society, but the working conditions of local workers need to be improved in future biomass energy development.     

Mitigation assessment results and priorities for China''s energy sector

Energy-related CO₂ emission projections of China up to 2030 are given. CO₂ mitigation potential and technology options in main fields of energy conservation and energy substitution are analyzed. CO₂ reduction costs of main mitigation technologies are estimated and the multi-criteria approach is used for assessment of priority technologies.

The results of this study show (1) Given population expansion and high GDP growth, energy-related CO₂ emissions will increase in China. (2) There exists a large energy conservation potential in China. (3) Adjustment of industry structure and increase of shares of products with high added value have and will play a very important role in reducing energy intensity of GDP. (4) Energy conservation and substitution of coal by natural gas, nuclear power, hydropower and renewable energy will be the key technological measures in a long-term strategy to reduce GHG emission. (5) Identification and implementation of GHG mitigation technologies is consistent with China's targets of sustainable development and environmental protection. (6) Energy efficiency improvement is a “no-regret” option for CO₂ reduction, whereas an incremental cost is needed to develop hydropower and renewable energy.     

Does environmental infrastructure investment contribute to emissions reduction? A case of China

Environmental infrastructure investment (EII) is an important environmental policy instrument on responding to greenhouse gas (GHG) emission and air pollution. This paper employs an improved stochastic impact by regression on population, affluence and technology (STRIPAT) model by using panel data from 30 Chinese provinces and municipalities for the period of 2003–2015 to investigate the effect of EII on CO₂ emissions, SO₂ emissions, and PM_2.5 pollution. The results indicate that EII has a positive and significant effect on mitigating CO₂ emission. However, the effect of EII on SO₂ emission fluctuated although it still contributes to the reduction of PM_2.5 pollution through technology innovations. Energy intensity has the largest impact on GHG emissions and air pollution, followed by GDP per capita and industrial structure. In addition, the effect of EII on environmental issues varies in different regions. Such findings suggest that policies on EII should be region-specific so that more appropriate mitigation policies can be raised by considering the local realities.     

Cost effective integration of hydrogen in energy systems with CO2 constraints

The integration of hydrogen in national energy systems is illustrated in four extreme scenarios, reflecting four technological mainstreams (energy conservation, renewables, nuclear and CO₂ removal) to reduce C emissions. Hydrogen is cost-effective in all scenarios with higher CO₂ reduction targets. Hydrogen would be produced from fossil fuels, or from water and electricity or heat, depending upon the scenario. Hydrogen would be used in the residential and commercial sectors and for transport vehicles, industry, and electricity generation in fuel cells. At severe (50–70%) CO₂ reduction targets, hydrogen would cost-effectively supply more than half of the total useful energy demands in three out of four scenarios. The marginal emission reduction costs in the CO₂ removal scenario at severe CO₂ reduction targets are DFL 200/tCO₂ (ca $ 100/t). In the nuclear, renewable and energy conservation scenarios these costs are much higher. Whilst the fossil fuel scenario would be less expensive than the other scenarios, the possibility of CO₂ storage in depleted gas reservoirs is a conditio sine qua non.     

A comparison of electricity and hydrogen production systems with CO2 capture and storage—Part B: Chain analysis of promising CCS options

Promising electricity and hydrogen production chains with CO₂ capture, transport and storage (CCS) and energy carrier transmission, distribution and end-use are analysed to assess (avoided) CO₂ emissions, energy production costs and CO₂ mitigation costs. For electricity chains, the performance is dominated by the impact of CO₂ capture, increasing electricity production costs with 10–40% up to 4.5–6.5 €ct/kWh. CO₂ transport and storage in depleted gas fields or aquifers typically add another 0.1–1 €ct/kWh for transport distances between 0 and 200 km. The impact of CCS on hydrogen costs is small. Production and supply costs range from circa 8 €/GJ for the minimal infrastructure variant in which hydrogen is delivered to CHP units, up to 20 €/GJ for supply to households. Hydrogen costs for the transport sector are between 14 and 16 €/GJ for advanced large-scale coal gasification units and reformers, and over 20 €/GJ for decentralised membrane reformers. Although the CO₂ price required to induce CCS in hydrogen production is low in comparison to most electricity production options, electricity production with CCS generally deserves preference as CO₂ mitigation option. Replacing natural gas or gasoline for hydrogen produced with CCS results in mitigation costs over 100 €/t CO₂, whereas CO₂ in the power sector could be reduced for costs below 60 €/t CO₂ avoided.     

CO2 sequestration in Ontario, Canada. Part II: cost estimation

As the Kyoto target set for Canada is to reduce GHG emission by 6% of the 1990 level by 2008–2012, several options are being considered to achieve this target. One of the possible options in Ontario is geological sequestration of captured CO₂ in saline aquifers, where CO₂ is expected to be stored for long geological periods, from 100 to several thousand years depending on the size, property and location of the reservoir. The preferred concept is to inject CO₂ into a porous and permeable reservoir covered with a cap rock located at least 800 m beneath the earth's surface where CO₂ can be stored under supercritical conditions. This paper evaluates the capital and operating cost for CO₂ sequestration in southwestern Ontario from a 500 MW coal fired power plant. The main focus is on the cost of sequestration (CO₂ transport and injection), and thus, the cost of capturing and pressurizing the CO₂ from the plant flue gas is not considered here.

A significant amount of capital investment is necessary to transfer CO₂ from a 500 MW fossil fuel power plant to the injection location and to store it underground. Major components of the cost include: cost of pipeline, cost of drilling injection wells and installing platforms, since the more plausible injection area is under Lake Erie. Many uncertainties are associated with cost estimation; several are identified and their impacts are considered in this paper. The estimated cost of sequestration of 14,000 ton/day of CO₂ at approximately 110 bar in southwestern Ontario is between 7.5 and 14 US$/ton of CO₂ stored.     

Nuclear power and the environment: comparative assessment of environmental and health impacts of electricity-generating systems

This paper deals with comparative assessment of the environmental and health impacts of nuclear and other electricity-generation systems. The study includes normal operations and accidents in the full energy chain analysis. The comparison of environmental impacts arising from the waste-management cycles associated with non-emission waste are also discussed. Nuclear power, while economically feasible and meeting 17% of the world's demand for electricity, is almost free of the air polluting gases that threaten the global climate. Comparing nuclear power with other sources for electricity generation in terms of their associated environmental releases of pollutant such as SO₂, NOX, CO₂, CH₄ and radioisotopes, taking into account the full fuel chains of supply option, nuclear power will help to reduce environmental degradation due to electricity generation activities. In view of CO₂ emission, the ranking order commences with hydro, followed by nuclear, wind and photovoltaic power plants. CO₂ emissions from a nuclear power plant are by two orders of magnitude lower than those of fossil-fuelled power plants. A consequent risk comparison between different energy sources has to include all phases of the whole energy cycle. Coal mine accidents have resulted in several 1000 acute deaths over the years. Then came hydropower, also resulting in many catastrophes and loss of human lives, followed by the oil and gas energy industries, last in the list is commercial nuclear energy, which has had a “bad” press because of the Chernobyl accident, resulting officially in 31 acute fatalities, and at least 145 latent fatalities. The paper offers some findings and conclusions on the role of nuclear power in protecting the global environment.     

利用水合物法分离捕集二氧化碳研究进展

我国是以煤炭为主要能源的国家,面临着严峻的碳减排挑战。相对于传统气体分离技术,水合物法CO₂分离捕集技术具有环境友好、工艺简单、能耗低等特点,被认为是具有应用前景的CO₂分离捕集技术,因而被广泛研究。综合调研了国内外水合物法分离捕集CO₂的研究,从热力学、动力学、微观分析、分离工艺及分离装备、成本比较等方面对相关研究进行了系统分析及综合评价,并详细讨论了水合物平衡条件和不同类型添加剂对水合物平衡条件的影响。为进一步开发水合物法CO₂分离捕集技术的研究提供指导。     

Integrated resource planning in the power sector and economy-wide changes in environmental emissions

This paper analyzes the roles of key factors (i.e., changes in structure, fuel mix and final demand) on total economy-wide changes in CO₂, SO₂ and NO_x emissions when power sector development follows the integrated resource planning (IRP) approach instead of traditional supply-based electricity planning (TEP). It also considers the rebound effect (RE) of energy efficiency improvements in the demand side and analyzes the sensitivity of the results to variations in the values of the RE. A framework is developed to decompose the total economy-wide change in the emission of a pollutant into four major components, i.e., structural change-, fuel mix- , final demand- and joint-effects. The final demand effect is further decomposed into three categories, i.e., construction of power plants, electricity final demand and final demand related to electricity using equipments. The factor decomposition framework is then applied in the case of the power sector in Indonesia. A key finding in the case of Indonesia is that in the absence of the RE, there would be total economy-wide reductions in CO₂, SO₂ and NO_x emissions of 431, 1.6 and 1.3 million tons respectively during the planning horizon of 2006–2025 under IRP as compared to that under TEP. The decomposition analysis shows that the final demand effect would account for 38% of the total CO₂ emission reduction followed by the structural change effect (35.1%) and fuel mix effect (27.6%) while the joint effect is negligible. The study also shows that economy-wide CO₂ emission reduction due to IRP considering the RE of 45% would be 241 million tons as compared to 333 million tons when the RE is 25%.     

Carbon dioxide emission rates for conventional and synthetic fuels

With rising concern about the increasing atmospheric concentration of CO₂ and its potential impact on global climate, there have been suggestions that the CO₂ emission rates be considered in selecting among fuel-producing technologies. Many previous comparisons have been inadequately drawn. We discuss criteria for carefully drawn comparisons and compute CO₂ emission rates in kgC/10⁹ joules for a variety of conventional or synthetic fuel processes. Although the total CO₂ release per joule is on the order of 1.8 (±0.2) times as much for burning liquid fuels from coal as for liquid fuels from crude oil, useful comparisons among synthetic fuel processes are not easy and the results are subject to changes in boundary conditions of resource availability, plant location, environmental requirements, output slate desired, economics, etc.     

Natural gas fired combined cycle power plant with CO2 capture

A natural gas (NG) fired power plant is designed with virtually zero emissions of pollutants, including CO₂. The plant operates in a gas turbine-steam turbine combined cycle mode. NG is fired in highly enriched oxygen (99.7%) and recycled CO₂ from the flue gas. Liquid oxygen (LOX) is supplied by an on-site air separation unit (ASU). By cross-integrating the ASU with the CO₂ capture unit, the energy consumption for CO₂ capture is significantly reduced. The exergy of LOX is used to liquefy CO₂ from the flue gas, thereby saving compression energy and also delivering product CO₂ in a saleable form. By applying a new technique, the gas turbine efficiency is increased by about 2.9%. The net thermal efficiency (electricity out/heat input) is estimated at 45%, compared to a plant without CO₂ capture of 54%. However, the relatively modest efficiency loss is amply compensated by producing saleable byproducts, and by the virtue that the plant is pollution free, including NO_x, SO₂ and particulate matter. In fact, the plant needs no smokestack. Besides electricity, the byproducts of the plant are condensed CO₂, NO₂ and Ar, and if operated in cogeneration mode, steam.     

The impact of CHP generation on CO2 emissions

The combined generation of heat and power (cogeneration) is praised by many as a technique for reducing the emissions of CO₂ in industrialized nations. This is generally true but not always. In this article we discuss the impact of some major variables on the CO₂ emission reduction capacity of cogeneration. Two sets of variables are predominant: the characteristics of the CHP process and the composition of the electricity generation sector. We highlight the interaction between the two sets of variables with the help of diagrams.     

铁系无机材料用于新能源电催化硝酸盐还原制氨

硝酸盐是一类普遍存在的环境污染物,而其对应的还原态氨却是重要的化工原料和农业肥料。因此,探索将两者直接结合的化学转化具有重大的技术及经济战略意义,尤其是对当今“双碳”战略驱动下的高碳排放合成氨的工艺变革以及氨可能成为下一代载氢燃料。通过电催化技术,将硝酸盐还原合成氨过程与可再生能源电力结合,构建绿色低碳的含氮化学品人工“氮循环”的新循环技术与经济体系,是解决目前合成氨工业对化石能源高度依赖、高碳排放问题以及开发新氢能的有力途径。借鉴传统合成氨催化广泛应用、具有成本优势的铁系催化机制,分别选取单质Fe、Fe₂O₃和Fe₃O₄作为电催化材料,探索并揭示电催化硝酸盐还原合成氨催化反应的化学形态。结果表明：在相对于可逆氢电极电势为-0.53～-0.93 V区间内,Fe₂O₃表现出了最优异的催化活性,其生成氨的法拉第效率■最高可达88%,对应的生成氨电流密度■为43.1 mA/cm²、氨生成速率■为0.20 mmol/(cm²     

Hydrogen no longer a high cost solution to global warming: New ideas

This paper contains brief statements about three new low-cost methods of obtaining clean hydrogen in massive amounts.

In the first method, new technology for converting solar energy and water to hydrogen at a price of $2.50 for an amount of hydrogen equal in first law energy to that in a gallon of gasoline seems to follow from a company's announcement of their new technology, already working, in one fully industrialized plant, producing electricity at a price corresponding to that from coal.

In the second method, pure hydrogen (no accompanying CO₂) can be obtained from natural gas and heat. The cost would be a little less than that of the low-cost hydrogen from water decomposition (and avoid storage of hydrogen for the 18 h/day of zero solar light).

In the third method, CO₂ is extracted from the atmosphere and combined chemically with the low-cost hydrogen to produce methanol. On being used to produce heat or electricity (fuel cell), CO₂ is left over. However, the amount of CO₂, thus added to the atmosphere is just equivalent to the amount removed. The presence of low-cost hydrogen from water means that the resulting methanol will also be of low cost and be a cure for global warming without a radical change of distribution method.     

Transaction costs of unilateral CDM projects in India–results from an empirical survey

Recently, transaction costs in the context of the Clean Development Mechanism (CDM) gained considerable attention as they were generally perceived to be significantly higher than for the other Kyoto Mechanisms. However, empirical evidence on the amount of transaction costs of CDM projects is very scarce. This paper presents the results from an empirical survey designed to quantify transaction costs of potential non-sink CDM projects in India. The definition of transaction costs of CDM projects was derived from recent literature and observations made in the current market for Certified Emission Reductions (CERs). During the survey, parts of transaction costs of 15 projects were quantified. An assessment of the results showed that specific transaction costs depend, to a large extent, on economies of scale in terms of total amount of CERs generated over the crediting period. Total transaction costs were quantified for seven projects. The costs range from 0.07 to 0.47 $US/t CO₂. As the projects have an emission reduction between 0.24 Mt CO₂ and 5.00 Mt CO₂ over the crediting period, the results support the assumption of Michaelowa et al. (Climate Policy 3 (2003) 273) that projects with emission reductions smaller than 0.20 Mt CO₂ are not economically viable at current CER prices.     

CO2 utilization options, Part I: An emission assessment framework

The utilization of CO₂ in various products and services must be carefully assessed in order to achieve reduced CO₂ emissions and simultaneously to add to the net economic benefit of society. In this paper, a framework for the assessment of CO₂ utilization options in the chemical industry is outlined in which the total CO₂ emission is estimated in four steps. First, the processes under study are surveyed to establish the consumption of different raw materials (reactants). Second, the CO₂ emission due to the content of fossil carbon in the reactants is determined, i.e. the material-related emission. Third, the CO₂ emission related to energy consumption in the studied processes is estimated, i.e. the direct energy-related emission. Fourth, the CO₂ emission related to energy consumption in the reactant production processes is estimated, i.e. the indirect energy-related emission.