Anton Alexandru Kiss

This research presents a novel framework for the surrogate-based dynamic optimization of control schemes within chemical separation and purification processes such as the biorefinery downstream processing. The current study investigated the downstream of an enzymatic bioreactor responsible for the synthesis of 5-hydroxymethylfurfural value-added derivatives, focusing on the critical balance between operational costs and productivity. Two high-fidelity long short-term memory neural network-based surrogate models were developed to predict energy consumption and economic gain, both achieving a coefficient of determination (R2) exceeding 0.97. These models were subsequently integrated into a multi-objective optimization architecture to address an operating efficiency testing scenario characterized by stepwise inflow parameter changes. By exploring the resulting Pareto front, an optimal set of operational (control) settings was identified and validated. The results demonstrate that while energy consumption remained nearly constant, the total economic benefit increased by approximately 20% over the whole studied timeframe. Critically, during the transient period between steady-states, the economic benefit surged by nearly 60%, highlighting the potential of surrogate-based dynamic optimization. The high computational efficiency of the developed models (optimal solution obtained in less than three minutes) suggests significant real-time process control application possibilities. Unlike computationally expensive first-principles models, the developed neural architectures allow for virtually instantaneous setpoint adjustments. This paves the way for their integration into model predictive control or real-time process control layers, enabling industrial plants to respond adaptively to feed fluctuations, minimize off-spec product during transitions, and maximize profitability.

Small-scale, renewable-powered Haber–Bosch (HB) synthesis is constrained by inefficient ammonia separation at reduced operating pressures, where conventional condensation removes less than 10% of NH₃ per pass due to vapor–liquid equilibrium limitations. Sorption-based separation offers a potential alternative by selectively removing NH₃ from the synthesis loop, enhancing equilibrium conversion.This work develops an integrated framework combining sorbent screening, dynamic cycle simulation, and process-level energy assessment for distributed ammonia production.Five sorbent classes (activated carbons, zeolites, metal halides, hydrides, and borohydrides) were evaluated using a multi-criteria decision methodology based on working capacity, regeneration requirements, kinetics, stability, cost, and safety. Zeolite 13X was identified as the most suitable candidate and implemented in a three-step pressure swing adsorption (PSA) cycle simulated in Aspen Adsorption® V14 under representative HB effluent conditions (220 °C, 150 bar, 24 mol% NH₃).The PSA cycle reduced the recycle NH₃ concentration from 2.4 mol% to 0.033 mol%, corresponding to a ~70-fold improvement in recycle cleanup. However, the desorption stream contained only 37 mol% NH₃, significantly below the 99.99 mol% purity achieved by conventional condensation.A shortcut screening framework linking sorbent properties to process-level energy demand was developed and benchmarked against the conventional separation requirement of 0.21 kWh kg⁻¹ NH₃. Although the PSA cycle satisfies the benchmark in terms of recycle cleanup and nominal separation energy, product dilution remains the dominant limitation. The proposed framework identifies the sorbent targets required for sorption-enhanced HB systems to become energetically competitive, providing a generalizable methodology for process–material integration studies.

Steel mill off gas fermentation presents a promising green alternative to petrochemical isopropyl alcohol (isopropanol, IPA) and acetone production while potentially reducing greenhouse gas emissions. A pilot-scale study stated negative global warming potential (GWP) at 85% gas conversion and 90% product selectivity. However, industrial-scale plant design including detailed techno-economic assessment (TEA) and life cycle assessment (LCA) remain undescribed. Therefore, this study modelled a heat-integrated 47.5 kton/ year gas fermentation process to IPA and acetone, based on pilot-scale data. The downstream processing was designed using vacuum distillation and heat-pump integrated (extractive) distillation to purify the 50 gproduct/ L broth with biomass and acetate as byproducts, to obtain 41.8 kton/ year of 99.6 wt. % IPA and 5.64 kton/ year of 99.0 wt. % acetone. Notably, no steam is consumed and 2.6 MWh of electricity is generated by utilising the energy from the steel mill off gas. The estimated unit production cost (UPC; 0.57 $/kgproduct) is significantly below market prices (1.65 $/ kgIPA and 1.45 $/ kgacetone). Moreover, the cradle-to-gate LCA gave GWPs of -1.42 kgCO2-eq/ kgIPA and -1.25 kgCO2-eq/ kgacetone, mainly due to avoided steel mill emissions. Other environmental impacts studied were also lower than for petrochemical production. Only the freshwater use is higher (70 L/ kgIPA and 62 L/ kgacetone) compared to petrochemical production (16 L/ kgIPA and 28 L/ kgacetone). Future research should study the impact of IPA and acetone selectivity and titer on the economic and environmental sustainability of steel mill off gas fermentation to IPA and acetone.

Acrylonitrile is a critical commodity chemical used to produce a variety of industrial polymers, such as carbon fibers, plastics, etc. Currently 90% of the global acrylonitrile production is based on propylene ammoxidation. However, there is no literature reporting the whole process holistically in detail, and which also looks into the energy utilization of the whole process including the reaction heat as well as the energy demands of the downstream separation. This original study provides a rigorous process design of the full process from a holistic viewpoint, covering 7 sections of acrylonitrile production (reaction, acid quenching, absorption-desorption, hydrogen cyanide recovery, acrolein recovery, acrylonitrile-acetonitrile-water separation, acetonitrile recovery sections). In order to further improve the energy efficiency, three energy integration strategies are proposed (1) Energy integrated downstream processing; (2) Systematic heat integration utilizing the heat of reaction; (3) Power generation by process surplus heat. Design 1 employs a direct heat exchanger network, recovering 30.1 MW heat through multiple heat exchanges, saving 86.91% fuel gas, 17.38% low pressure steam and 43.96% cooling utilities. Design 2 and 3 recovers 58.39 MW heat, and 12.20 MW low pressure steam is output as waste heat recovery in design 2, whereas 11.06 MW low pressure steam and 7.8 MW electricity are generated in design 3. The pro/con each options are also discussed for further guidance. As the first comprehensive description of the design of the entire acrylonitrile production process, this work highlights the potential for improved energy efficiency in the acrylonitrile production.

The electrification of chemical processes and carbon capture and utilisation represent two promising approaches to improve efficiency and decrease carbon emissions of the process industry. The development of electrolyzers has gathered momentum in the last decades, allowing for the possible introduction of renewable electrons into carbon dioxide-based chemicals manufacture. While the performance of the electrolyzers is subject to improvements driven by the experimental community, the generation of waste heat is unavoidable due to the electrical resistances and process inefficiencies within the electrochemical cells. The possibility of re-using this waste heat has not been investigated within the realm of carbon dioxide electrolyzers. Here we show the potential of upgrading this waste heat by means of a heat pump, for its utilisation in the downstream processing of formic acid obtained from carbon dioxide electroreduction. We found that the waste heat represents roughly 62% of the power input to the electrochemical cells and it can be upgraded from 35 °C to 112 °C to drive the extractive distillation of formic acid and water. For a system producing 25 kt/y of formic acid, this results in the electrification of 60% of the separation energy duty, yielding a decrease in carbon dioxide emissions of 39-58% for the downstream processing, while the addition of a heat pump has a payback period of ~4.4 years in the base case.