Integral Multiphase Turbulence Compressible Jet Expansion Model for Accidental Releases from Pressurized Containments

The accurate prediction of the conditions of a pressurized jet upon its expansion to atmospheric pressure is of fundamental importance in assessing the consequences associated with accidental releases of hazardous fluids from pressurized containments. An integral multiphase compressible jet expansion model which for the first time accounts for turbulence generation is presented. Real fluid behavior is accounted for applying a suitable equation of state. By use of the accidental release of two-phase CO2 from a pressurized system as an example, the proposed model is shown to provide far better predictions of the fully expanded jet momentum and hence its downstream flow characteristics as compared to existing integral models where the impact of turbulence generation is ignored

Assessing the potential of utilisation and storage strategies for post-combustion CO2 emissions reduction

The emissions reduction potential of three carbon dioxide handling strategies for post-combustion capture is considered. These are carbon capture and sequestration/storage (CCS), enhanced hydrocarbon recovery (EHR), and carbon dioxide utilization (CDU) to produce synthetic oil. This is performed using common and comparable boundary conditions including net CO2 sequestered based on equivalent boundary conditions. This is achieved using a “cradle to grave approach” where the final destination and fate of any product is considered. The input boundary is pure CO2 that has been produced using a post-combustion capture process as this is common between all processes. The output boundary is the emissions resulting from any product produced with the assumption that the majority of the oil will go to combustion processes. We also consider the “cradle to gate” approach where the ultimate fate of the oil is not considered as this is a boundary condition often applied to EHR processes. Results show that while CCS can make an impact on CO2 emissions, CDU will have a comparable effect whilst generating income while EHR will ultimately increase net emissions. The global capacity for CDU is also compared against CCS using data based on current and planned CCS projects. Analysis shows that current CDU represent a greater volume of capture than CCS processes and that this gap is likely to remain well beyond 2020 which is the limit of the CCS projects in the database

Kinetic and economic analysis of reactive capture of dilute carbon dioxide with Grignard reagents

Carbon Dioxide Utilisation (CDU) processes face significant challenges, especially in the energetic cost of carbon capture from flue gas and the uphill energy gradient for CO2 reduction. Both of these stumbling blocks can be addressed by using alkaline earth metal compounds, such as Grignard reagents, as sacrificial capture agents. We have investigated the performance of these reagents in their ability to both capture and activate CO2 directly from dried flue gas (essentially avoiding the costly capture process entirely) at room temperature and ambient pressures with high yield and selectivity. Naturally, to make the process sustainable, these reagents must then be recycled and regenerated. This would potentially be carried out using existing industrial processes and renewable electricity. This offers the possibility of creating a closed loop system whereby alcohols and certain hydrocarbons may be carboxylated with CO2 and renewable electricity to create higher-value products containing captured carbon. A preliminary Techno-Economic Analysis (TEA) of an example looped process has been carried out to identify the electrical and raw material supply demands and hence determine production costs. These have compared broadly favourably with existing market values

Flexible operation of post-combustion CO2 capture at pilot scale with demonstration of capture-efficiency control using online solvent measurements

Flexible post-combustion carbon capture and storage (CCS) has the potential to play a significant part in the affordable decarbonisation of electricity generation portfolios. PCC plant operators can modify capture plant process variables to adjust the CO2 capture level to a value which is optimal for current fuel cost, electricity selling price and CO2 emissions costs, increasing short-term profitability. Additionally, variation of the level of steam extraction from the generation plant can allow the capture facility to provide additional operating flexibility for coal-fired power stations which are comparatively slow to change output. A pilot-scale test campaign investigates the response of plant operating parameters to dynamic scenarios which are designed to be representative of pulverized coal plant operation. Online sensors continuously monitor changes in rich and lean solvent CO2 loading (30%wt monoethanolamine). Solvent loading is likely to be a critical control variable for the optimisation of flexible PCC operation, and since economic and operational boundaries can change on timescales 30mins or shorter, the development of methods for rapid, continuous online solvent analysis is key. Seven dynamic datasets are produced and insights about plant response times and hydrodynamics are provided. These include power output maximization, frequency response, power output ramping and a comparison between two plant start-up strategies. In the final dynamic operating scenario, control of CO2 capture efficiency for a simple reboiler steam decoupling and reintroduction event is demonstrated using only knowledge of plant hydrodynamics and continuous measurement of solvent lean loading. Hot water flow to the reboiler is reduced to drop the capture efficiency. The “target” value for the minimum capture efficiency in the scenario was set at 30%, but a minimum CO2 capture efficiency of 26.4% was achieved. While there remains scope for improvement this represents a significant practical step towards the control of capture plant using online solvent concentration and CO2 measurements, and the next steps for its further development are discussed

Gas storage

International audienceThe continuous increase of energy demands based on fossil fuels in the last years have lead to an increase of greenhouse gases (GHG) emission which strongly contribute to global warming. The main strategies to limit this phenomenon are related to the efficient capture of these gases and to the development of renewable energies sources with limited environmental impact. Particularly, carbon dioxide (CO2) and methane (CH4) are the main constituents of greenhouse gases while hydrogen (H2) is considered an alternative clean energy source to fossil fuels. Therefore, tremendous research to store these gases has been reported by several approaches and among them the physisorption on activated carbons (AC) have received significant attention. Their abundance, low cost and tunable porous structure and chemical functionalities with an existing wide range of precursors that includes bio-wastes make them ideal candidates for gas applications. This chapter presents the recent developments on CH4, CO2 and H2 storage by activated carbons with focus on biomass as precursor materials. An analysis of the main carbon properties affecting the AC's adsorption capacity (i.e. specific surface area, pore size and surface chemistry) is discussed in detail herein

Science and the stock market: Investors' recognition of unburnable carbon

This paper documents the stock market's reaction to a 2009 paper in the Nature journal of science, which concluded that only a fraction of the world's existing oil, gas, and coal reserves could be emitted if global warming by 2050 were not to exceed 2 °C above pre-industrial levels. This Nature article is now one of the most cited environmental science studies in recent years. Our analysis indicates that this publication prompted an average stock price drop of 1.5% to 2% for our sample of the 63 largest U.S. oil and gas firms. Later, in 2012-2013, the press "discovered" this article, writing hundreds of stories on the grim consequences of unburnable carbon for fossil fuel companies. We show only a small negative reaction to these later stories, mostly in the two weeks following their publication. This limited market response contrasts with the predictions of some analysts and commentators of a substantial decline in the shareholder value of fossil fuel companies from a carbon bubble. Our paper discusses possible reasons for this discrepancy

A novel sub-seabed CO₂ release experiment informing monitoring and impact assessment for geological carbon storage

Carbon capture and storage is a mitigation strategy that can be used to aid the reduction of anthropogenic CO2 emissions. This process aims to capture CO2 from large point-source emitters and transport it to a long-term storage site. For much of Europe, these deep storage sites are anticipated to be sited below the sea bed on continental shelves. A key operational requirement is an understanding of best practice of monitoring for potential leakage and of the environmental impact that could result from a diffusive leak from a storage complex. Here we describe a controlled CO2 release experiment beneath the seabed, which overcomes the limitations of laboratory simulations and natural analogues. The complex processes involved in setting up the experimental facility and ensuring its successful operation are discussed, including site selection, permissions, communications and facility construction. The experimental design and observational strategy are reviewed with respect to scientific outcomes along with lessons learnt in order to facilitate any similar future