To facilitate large-scale green hydrogen production, manufacturers are moving towards pressurized and strongly coupled topologies where multiple electrolyzers share the same processing equipment. This coupling increases the control challenges regarding temperature and safety-critical gas purity constraints. In this paper we develop two advanced regulatory control elements aimed at these constraints and embed them in a plantwide control structure for such systems. We show in dynamic simulations that our approach achieves nearly the same production efficiency as with an explicit optimization layer, while being inherently safer compared to reference control structures. We further show that it can extend the operating limits by up to 50% compared to simpler regulatory control layers, allowing for significant increases in flexibility and thereby profitability in the day-ahead electricity market.

CCS is a well investigated and fairly promising technology for reducing the emission of carbon dioxide (CO2) to the atmosphere. However, it is rarely implemented in the industry due to its high cost. Therefore, this work proposes a cost optimized CCS chain which can be operated flexibly and safely. For the capture process a post combustion chemical absorption technology is chosen due to its retrofitting possibility to already existing power plants and its low capture cost. In order to find a cost efficient absorption process for different scenarios, the five most promising process configurations from previous work are combined into a superstructure in a rigorous rate based reactive Aspen Plus model. This in turn is optimized by a two-stage stochastic programming approach in Matlab. The optimal supply chain network is identified by a tailor made transshipment model implemented in GAMS, which accounts for the most promising transportation units, storage sites as well as direct utilizatio... [more]

For this year’s EURECHA challenge we have made our report with two very different segments in mind. One is technical and is based on verifiable data, calculations and of course computer simulations, while the other segment is more illustrative, and serves only to give better representations. Of course bigger emphasis was put on the technical part. The computer simulations done for technical part of this report cover electrical provision from the light ends of the crude oil, fertilizer production using ammonia, which is produced taking heavy oil as a raw material. Furthermore, water recycling at the refinery and of course provision of potable water for the growing city is also considered. The simulation results showed that using suitable technologies and process integration it is possible to obtain a sustainable development of the Sheikhdom. The illustrative part is basically a city of 20,000 made in a computer game called “CITIES:Skylines”. The game allows the user to import real life... [more]

The escalating urgency to address climate change has driven carbon capture (CC) technologies into the spotlight, particularly for large-scale emitters, which benefit from economies of scale. However, small-scale emitters account for a significant share of CO2 emissions, yet such applications remain largely overlooked in the literature. While CC cost is often used as a key performance indicator (KPI) for CC technologies, the lack of standardized cost estimation methods leads to inconsistencies, complicating comparisons, and hindering the deployment of CC systems. This study addresses these challenges by developing flexible short-cut correlations for selected CC technologies, providing estimates of the total equipment cost (TEC) and energy consumption specific to small-scale applications across various CO2 inlet concentrations (mol%) and capture scales (10 – 100 kt/y). The flexibility of the correlations enables the integration of various cost estimation methods available in the literatu... [more]

Shipping is the backbone of global freight. However, due to its currently strong reliance on fossil fuels, it accounts for 3 % of global greenhouse gas emissions, highlighting both the need and challenge of achieving the required rapid decarbonization. Over the past decade, Onboard carbon capture and storage (OCCS) has gained interest as a potential mitigation strategy while alternative fuels continue to develop. However, several capture technologies could be considered to capture the resulting CO2. In order to identify the most promising ones, this study performs a screening of different capture technologies (including absorption, membrane-assisted liquefaction, adsorption-assisted liquefaction, calcium-looping) through the case of a combination carrier under retrofit and newbuilding scenarios.
Overall, the results indicate that retrofit installations can reduce CO2 emissions by at least 45 %, even when using the existing ship power system. Once the utility (heat and power) is assum... [more]

While he was trapped in a Shell oil refinery for weeks during a 1973 plant strike, Charles R. Cutler (1936-2020) used the opportunity to try out his untested theories on a new method for controlling chemical plants on the actual refinery. They worked spectacularly, and the resulting Dynamic Matrix Control method later became a standard part of control engineering practice. However, DMC was kept a trade secret at Shell until 1980 when it was first made available to the public. This book uncovers the history behind the theory by publishing Cutler’s writings and letters, including his 1969 thesis proposal letter to Prof. Huang at the University of Houston outlining his theories, and a more developed draft paper from 1975 that was never published. Science historians and control engineers alike can trace the development of the theory over time from its earliest origins.