Specific Carbon Dioxide Emissions Research Articles

Thermo-economic analysis of conventional combined cycle hybridization: United Arab Emirates case study

Extensive investigations have been conducted to find a replacement for fossil fuels and natural gases in power generation industries. Solar energy is one of the most promising solution to a more environmentally friendly power production technology. In particular, concentrated solar power technologies are displaying significant potential for electricity production. United Arab Emirates hot and sunny climate is an indication of the great potential it possesses for hybrid and solar only power plant implementation. In this paper, power plant hybridization feasibility in the United Arab Emirates is taken under extensive investigation. Moreover, a thermo-economic optimization is performed for the installment of a new 50MWe hybrid conventional combined cycle power plant in the United Arab Emirates. In addition, hybridization of an already existing conventional combined cycle power plant is comprehensively investigated by utilizing levelized cost of electricity, payback period, life cycle saving, and net present value approaches. The hybrid conventional combined cycle power plant optimum levelized cost of electricity and net present value are 77.7US$/MWh and −34.918MUS$, respectively. Additionally, the plant solar share and specific carbon dioxide emission are 8.87% and 371.9kgCO2/MWh, respectively.

ECO-EFFICIENCY INDICATORS IN THE EVALUATION OF ENVIRONMENTAL PERFORMANCE OF THERMAL POWER PLANTS

Eco-efficiency is a key concept which brings together two essential aspects for economic progress and ecological aspect. Eco-efficiency indicators are very relevant and play an important role for environmental cost management. For a thermal power plant, which has a great impact on the environment, these indicators involve lower costs and efficient use of energy, water and fuel. The paper proposes a number of eco-efficiency indicators applicable to a thermal power plant, according with specific literature. Also, the carbon dioxide emissions generated from thermal power plants has been taken into consideration. CO2 is one of the greenhouse gases and the reduction of CO2 emissions is a important target according to Kyoto Protocol and may lead to slowing of global warming. The following indicators have been calculated for CHP Bacau, the power plant analyzed into the study case: core energy intensity, global efficiency, core waste intensity, core water intensity, water discharge, total generated waste and specific carbon dioxide emissions. Once these eco-efficiency indicators are determinate, it is possible to benchmark and compare two or more thermal power plants. Analysis of the proposed eco-efficiency indicators is a real support for any thermal power plant in order to optimize its performance and financial indicators, to increase efficiency and for recording environmental impact.

Determination of the specific carbon dioxide emission factor from thermal power plants Nikola Tesla A and B

Low-calorific lignite from Kolubara open-pit mines is mainly used for heat and power generation in PE 'Thermal Power Plants Nikola Tesla'. The IPCC methodology suggests that CO2 emissions by fossil fuel combustion shall be calculated as product of fuel mass and standardized (country or even region related) values of lower heating value, carbon emission factor and factor of oxidation of combusted fuel. This approach doesn't take into account the influences of unit thermal efficiency as well as fundamental characteristics of combustion process, the most important influencing factors on overall CO2 emission. This paper presents the results of calculation of specific CO2 emissions by three different approaches: (a) using the observed linear correlation for calculation of carbon emission factor of the raw lignite, (b) based on the level of CO2 in the flue gas measured at 6 different power plant thermal units 'Nikola Tesla' A and B, (c) based on the mass balance of carbon in the coal, flying ash and bot tom ash. Comparing all the results, we conclude that the best solution is obtained by using the observed linear correlation for calculation of the carbon emission factor of the raw lignite. The calculation of specific CO2 emissions based on the measured flow rate and the share of CO2 in the flue gas gives higher, while calculation based on the carbon mass balance gives less values for the specific CO2 emissions. Higher values for specific CO2 emissions and some dissipation of these results is obtained for units A1 and A2 at output power of about 200 MW, than in the case of units whose output power during the test was over 300 MW - units A4 and A6, or over 600 MW - units B1 and B2.

Optimization of an Integrated Steel Plant with Carbon Capturing and Utilization Processes

In this work, future perspectives of primary steelmaking integrated with carbon capturing and utilization processes are numerically studied with the aim to investigate fuel consumption and distribution in this industrial sector under different seasonal energy demand. The key options studied are an emerging blast furnace operation technology (oxygen blast furnace) combined with a polygeneration system producing district heat, electricity and methanol. A mathematical model is developed to find the optimal use of raw material and residual gases under specified operating costs, simultaneously considering the investment costs for the new process units in comparison of conventional steelmaking process. The results of the study provide guidelines on the distribution of the fuel in future integrated steel plant to increase sustainability and to make maximum use of available raw materials. The results reveal the optimal state of operation under periodic conditions, maximizing the net present value, minimizing specific carbon dioxide emissions and fuel consumption in the system.

Oxyfuel combustion in rotary kiln lime production

AbstractThe purpose of this article is to study the impact of oxyfuel combustion applied to a rotary kiln producing lime. Aspects of interest are product quality, energy efficiency, stack gas composition, carbon dioxide emissions, and possible benefits related to carbon dioxide capture. The method used is based on multicomponent chemical equilibrium calculations to predict process conditions. A generic model of a rotary kiln for lime production was validated against operational data and literature. This predicting simulation tool is used to calculate chemical compositions for different recirculation cases. The results show that an oxyfuel process could produce a high‐quality lime product. The new process would operate at a lower specific energy consumption thus having also a reduced specific carbon dioxide emission per ton of product ratio. Through some processing, the stack gas from the new process could be suitable for carbon dioxide transport and storage or utilization. The main conclusion of this paper is that lime production with an oxyfuel process is feasible but still needs further study.

A Thermo-Economic Study of Storage Integration in Hybrid Solar Gas-Turbine Power Plants

A thermo-economic simulation model of a hybrid solar gas-turbine (HSGT) power plant with an integrated storage unit has been developed, allowing determination of the thermodynamic and economic performance. Designs were based around two representative industrial gas-turbines: a high efficiency machine and a low temperature machine. In order to examine the trade-offs that must be made, multi-objective thermo-economic analysis was performed, with two conflicting objectives: minimum investment costs and minimum specific carbon dioxide (CO2) emissions. It was shown that with the integration of storage, annual solar shares above 85% can be achieved by HSGT systems. The levelized electricity cost (LEC) for the gas-turbine system as this level of solar integration was similar to that of parabolic trough plants, allowing them to compete directly in the solar power market. At the same time, the water consumption of the gas-turbine system is significantly lower than contemporary steam-cycle based solar thermal power plants.

Investigation of a Hybrid Photovoltaic-Biomass System With Energy Storage Options

A hybrid photovoltaic (PV)-biomass system with energy storage options is investigated based on energy and exergy analyses. The hybrid system consists of a photovoltaic system, an electrolyser, and a biomass gasifier, which is integrated with a biomass-based gas turbine. The PV system is accountable for 56% of the annual exergy destruction in the hybrid system, while 38% of the annual exergy destruction occurs in the biomass-gas turbine (GT) system. The overall energy and exergy efficiencies of the hybrid PV-biomass system with energy storage options are 34.8% and 34.1%, respectively. A 29% increase in both energy and exergy efficiencies is reported with an increase in the steam-to-carbon ratio (SC) in the range of 1–3 mol/mol. The related specific carbon dioxide emission reduction is 1441–583 g/kWh. In contrast to SC, an increase in gas turbine inlet temperature results in a negative effect on the overall energy and exergy efficiencies, and it does not make a significant contribution to the reduction in specific carbon dioxide emission.

Investigation of the residual heat recovery and carbon emission mitigation potential in a Chinese steelmaking plant: A hybrid material/energy flow analysis case study

Abstract As an energy intensive industry, China’s iron/steel industry faces the challenge of energy conservation and carbon emission reduction. Energy efficiency, especially residual heat recovery is a critical issue. China is promoting a circular economy strategy in the iron/steel industry, technology upgrading and industrial symbiosis make the material and energy flows more complicated. In order to quantify the energy flows and the related residual heat recovery and carbon emission mitigation potential, this study proposes a hybrid material and energy flow analysis approach at company level. We analyze the material based energy flow routes and the transformation rules. Then, we develop an evaluation index to evaluate the specific energy consumption (SEC) and direct carbon dioxide (CO2) emissions (DCE). Furthermore, a case study is conducted in a 10 million ton/year steelmaking plant in northern China. Results verified the effectiveness of the proposed approach. According to the results, the residual heat and carbon emission is mapped out graphically. Results highlight that the case company has 4.87 GJ/tons of crude steel residual heat recovery potential, equal to 26.08% of the total energy consumption. Finally, policy implications on the ever-improvement of residual heat utilization and the future research concerns are proposed and discussed.

Thermodynamic analyses of solar thermal gasification of coal for hybrid solar-fossil power and fuel production

Thermodynamic analyses are performed for solar thermal steam and dry gasification of coal. The selected types of coal are anthracite, bituminous, lignite and peat. Two model conversion paths are considered for each combination of the gasifying agent and the coal type: production of the synthesis gas with its subsequent use in a combined cycle power plant to generate power, and production of the synthesis gas with its subsequent use to produce gasoline via the Fischer–Tropsch synthesis. Replacement of a coal-fired 35% efficient Rankine cycle power plant and a combustion-based integrated gasification combined cycle power plant by a solar-based integrated gasification combined cycle power plant leads to the reduction in specific carbon dioxide emissions by at least 47% and 27%, respectively. Replacement of a conventional gasoline production process via coal gasification and a subsequent Fischer–Tropsch synthesis with gasoline production via solar thermal coal gasification with a subsequent Fischer–Tropsch synthesis leads to the reduction in specific carbon dioxide emissions by at least 39%.

An assessment of the potential for retrofitting existing coal-fired power plants in China

Abstract A consensus for the development of a low carbon economy in China is growing rapidly among Chinese energy stakeholders. But there is considerable uncertainty as to the role that carbon capture and storage (CCS) retrofit could play in this development. The State Council in China has set a target of cutting carbon dioxide emissions per unit of GDP by 40% by 2020 compared with the level for 2005. Although this provides some policy impetus for reducing carbon dioxide emissions in China, it is also important to note that over 350 GW of coal-fired power plant capacity has been built within the past five years and that these power plants are expected to operate for at least another 25 years. Because coal is an affordable and accessible fuel in China, both the China Electricity Council (CEC) and the International Energy Agency (IEA) estimates that another 300 GW of supercritical and ultra-supercritical new coalfired power plants will be constructed in the next decade to satisfy the growing energy demand of the country . But unless other options to reduce emissions can be implemented, a simple consideration of the emissions they produce suggests that some of these recently built power plants may be required to shut down within the next two decades to address Chinese and/or international climate policies. During the past five years, the national policy of ‘closing smaller and/or inefficient units to build large and more efficient units’ has been implemented not only to save energy, but also to reduce specific carbon dioxide emissions (i.e. reduced gCO 2 /kWh of electricity produced). Forcing early plant closure has, however, proved to be a difficult task under the institutional framework of the Chinese electricity sector, because these plants usually had not reached the end of their design lifetimes. Also it was only partially successful in the context of CO 2 reduction in the sense that companies wanted to build large plants to increase electrical output and strict rules meant they could only do this by closing a specified amount of older plant. But the end result was still that more coal was burnt and hence total CO 2 emissions to atmosphere increased. Retrofitting some of the existing power plants to capture CO 2 , which by contrast can achieve an absolute decrease in CO 2 emissions to atmosphere for an analogous loss in plant output (to the closures previously enforced) is therefore, an important option to address the threat of climate change while maintaining in the meantime the country’s electricity supply from coal. A preliminary investigation of over 100 large power plants in China was conducted to determine their potential for a retrofit with CO 2 capture, transport and storage. Factors assessed included geographic location, space on site, plant layout, water restriction, coal supply, efficiency, FGD status and potential access to storage sites. Based on these criteria, retrofitting prospects were evaluated and rated. It appears that about 45% of existing power plants may suffer from ‘carbon lock-in’ status, i.e. their emissions could not be abated using CCS technology, at least at ‘reasonable’ cost. Critical factors that would preclude capture retrofit are, not surprisingly, access to storage sites and unsuitable plant layout and/or space on site. Variations in other factors would affect the level of retrofitting cost, but this effect could be positive as well as negative. In principle, plants would be retrofitted in an order that reflects the extent to which these site specific factors would give higher or lower retrofit costs. The results aim to provide an overview of the potential issues that need to be considered by stakeholders, policy makers and manufacturing companies when deciding the market potential for CCS retrofit technology in China.

Comparative assessment of coal fired IGCC systems with CO2 capture using physical absorption, membrane reactors and chemical looping

The integrated gasification combined cycle (IGCC) as an efficient power generation technology with lowest specific carbon dioxide emissions among coal power plants is a very good candidate for CO2 capture resulting in low energy penalties and minimised CO2 avoidance costs. In this paper, the techno-economic characteristics of four different capture technologies, which are built upon a conventional reference case, are studied using the chemical process simulation package “ECLIPSE”. The technology options considered are: physical absorption, water gas shift reactor membranes and two chemical looping combustion cycles (CLC), which employ single and double stage reactors. The latter system was devised to achieve a more balanced distribution of temperatures across the reactors and to counteract hot spots which lead to the agglomeration and the sintering of oxygen carriers. Despite the lowest efficiency loss among the studied systems, the economic performance of the double stage CLC was outperformed by systems employing physical absorption and water gas shift reactor membranes. Slightly higher efficiencies and lower costs were associated with systems with integrated air separation units. The estimation of the overall capital costs was carried out using a bottom-up approach. Finally, the CO2 avoidance costs of individual technologies were calculated based on the techno-economic data.

Potentials for energy efficiency improvement in the US cement industry

This paper reports on an in-depth analysis of the US cement industry, identifying cost-effective energy efficiency measures and potentials. Between 1970 and 1997, primary physical energy intensity for cement production (SIC 324) dropped 30%, from 7.9 GJ/t to 5.6 GJ/t, while specific carbon dioxide emissions due to fuel consumption and clinker calcination dropped 17%, from 0.29 tC/tonne to 0.24 tC/tonne. We examined 30 energy-efficient technologies and measures and estimated energy savings, carbon dioxide savings, investment costs, and operation and maintenance costs for each of the measures. We constructed an energy conservation supply curve for the US cement industry which found a total cost-effective energy saving of 11% of 1994 energy use for cement making and a saving of 5% of total 1994 carbon dioxide emissions. Assuming the increased production of blended cement, the technical potential for energy efficiency improvement would not change considerably. However, the cost-effective potential would increase to 18% of total energy use, and carbon dioxide emissions would be reduced by 16%. This demonstrates that the use of blended cements is a key cost-effective strategy for energy efficiency improvement and carbon dioxide emission reductions in the US cement industry.

Vacuum treatment of molten steel— a new way of improving converter steel production

In this work, future perspectives of primary steelmaking integrated with carbon capturing and utilization processes are numerically studied with the aim to investigate fuel consumption and distribution in this industrial sector under different seasonal energy demand. The key options studied are an emerging blast furnace operation technology (oxygen blast furnace) combined with a polygeneration system producing district heat, electricity and methanol. A mathematical model is developed to find the optimal use of raw material and residual gases under specified operating costs, simultaneously considering the investment costs for the new process units in comparison of conventional steelmaking process. The results of the study provide guidelines on the distribution of the fuel in future integrated steel plant to increase sustainability and to make maximum use of available raw materials. The results reveal the optimal state of operation under periodic conditions, maximizing the net present value, minimizing specific carbon dioxide emissions and fuel consumption in the system.