Inherent Safety Analysis Research Articles

Energy-saving heat pump-assisted extractive-azeotropic dividing wall column with heat exchanger network for separating acetonitrile and water: A techno-economic and inherent safety investigation

In the present paper, a new extractive-azeotropic dividing wall column configuration is designed to recover acetonitrile from wastewater instead of the conventional two-column process. Although the performance of energetic and economic savings is enhanced in the dividing wall column, it is still characterised by high energy consumption. To this end, a methodical framework for designing energy-efficient intensified dividing wall columns is developed to gradually reduce the need for utilities. Results indicate that the reboilers of the extractive-azeotropic dividing wall column can be entirely replaced by the applications of vapour recompressed heat pump and heat exchanger network, which comprehensively improves the energy-saving performance. A multi-criteria evaluation of process sustainability, including energy consumption, total cost, environmental performance, energy efficiency, and inherent safety analysis, is performed among the designs. Results show that the heat-integrated extractive-azeotropic dividing wall column process is inherently safer than the conventional two-column process and reduces at most 51.95%, 89.96%, and 63.58% in total annual cost, CO2 emissions, and total energy consumption, respectively.

Economic, thermodynamic, environmental, and inherent safety investigation of heat pump-assisted extractive dividing wall column for separating binary azeotrope

Inherently safer design during the preliminary design stage is vital to reduce the potential risks and accidents of new process design. So far, little effort has been paid to incorporating inherent safety assessment into the techno-evaluation of heat-integrated extractive dividing wall column processes toward sustainable development. To this end, this paper proposes a systematic methodology for designing the energy-efficient extractive dividing wall column processes by applying heat pump and feed preheating techniques to separate binary azeotrope. The proposed approach gradually recovers the waste heat within the process, and the separation of acetonitrile and water is selected as a case. The results show that the total energy consumption, total annual cost, and the CO2 emissions of heat-integrated extractive dividing wall column processes are significantly reduced compared to conventional design, and the thermodynamic efficiency is simultaneously improved. In the process evaluation stage, the inherent safety analysis is performed regarding the Process Route Index and Process Stream Index. Such indices give insights into process safety performance in terms of the overall process and individual streams. The results of the inherent safety investigation show the intensified extractive dividing wall column by a single heat pump performs better than the dual heat pump-assisted process. This multi-criterion evaluation demonstrates a trade-off between inherent safety performance and energy saving in applying a heat pump system in conjunction with the distillation process.

Inherent Safety Analysis and Sustainability Evaluation of a Vaccine Production Topology in North-East Colombia

Influenza is a respiratory disease that may cause severe consequences to human health. Influenza caused between 99,000 and 200,000 deaths worldwide in 2019. Studies have reported the presence of this virus in Santander, Colombia, a region with a high humanitarian flow. An influenza vaccine production plant topology has been proposed previously. Nevertheless, the inherent safety and sustainably behavior of this topology is unknown. Process safety plays a crucial role in the evaluation of emerging technologies since it allows the identification of potential risks. Moreover, the current sustainability policies enforce the assessment of processes considering economic, social, and environmental aspects. For this reason, a safety and sustainability evaluation of a vaccine production topology is performed in this work. The inherent safety index (ISI) methodology was implemented to analyze the process. The sustainability evaluation was performed using the sustainability weighted return on investment metric (SWROIM), in which return on investment (ROI), output potential environmental impact (PEI output), total safety inherent index (ITI), and exergy efficiency were considered. The results showed that influenza vaccine production is inherently safe since the total inherent safety index was 11. The destroyed exergy was 378.69 MJ/h, the return on investment was 86%, and the SWROIM was estimated at 81%, which means slightly negative impacts on sustainability.

Inherent Safety Characteristics of Lead Bismuth Eutectic-Cooled Accelerator Driven Subcritical Systems

An accelerator driven subcritical system (ADS) is a new nuclear energy system which could not only produce clean energy but also incinerate nuclear waste. In this paper, inherent safety analysis of an ADS is performed with neutronics and thermal-hydraulics coupled code named ARTAP. Five typical accidents are carried out, including the cases of proton beam interruption, transient overpower, reactivity insertion, loss of flow, and loss of heat sink. The transient simulations are performed in the average channel and the hottest channel of the fuel pin in the ADS core. The simulation results for beam interruption show that the highest temperature of the pellet is in the middle of the fuel element in the average channel, while the peak temperature of the cladding is in the top of the fuel element. After the beam is interrupted for 20s, the maximum temperature drops at the fuel center, the cladding inner surface, and the outlet coolant in the hottest channel are 644.46K, 162.27K, and 136.42K respectively. For transient overpower accidents with the increase of beam intensity, the maximum temperature of the fuel and the cladding are below the safety limit. Concerning the reactivity insertion accident, it is found that the ADS has good inherent safety and its margin of criticality safety is large. The calculation results for loss of flow show that the power drop is small due to low sensitivity of the subcritical core to negative reactivity feedback, and the maximum temperature of the cladding reaches 1726K, which means the fuel element would rupture. However, the power and the temperatures of fuel, cladding, and coolant could decrease quickly to the safety level after the proton accelerator is cut off under a loss of flow accident. The results also show that the peak temperature of the cladding is lower than the safety limit under a loss of heat sink accident. The present simulation results reveal that the ADS has a remarkable advantage against severe accidents. It also implies that its inherent safety characteristics could ensure reactor shutdown by cutting off the proton beam after accidents occur.

Inherent Safety Assessment of Industrial-Scale Production of Chitosan Microbeads Modified with TiO2 Nanoparticles.

In this study, the inherent safety analysis of large-scale production of chitosan microbeads modified with TiO2 nanoparticles was developed using the Inherent Safety Index (ISI) methodology. This topology was structured based on two main stages: (i) Green-based synthesis of TiO2 nanoparticles based on lemongrass oil extraction and titanium isopropoxide (TTIP) hydrolysis, and (ii) Chitosan gelation and modification with nanoparticles. Stage (i) is divided into two subprocesses for accomplishing TiO2 synthesis, lemongrass oil extraction and TiO2 production. The plant was designed to produce 2033 t/year of chitosan microbeads, taking crude chitosan, lemongrass, and TTIP as the primary raw materials. The process was evaluated through the ISI methodology to identify improvement opportunity areas based on a diagnosis of process risks. This work used industrial-scale process inventory data of the analyzed production process from mass and energy balances and the process operating conditions. The ISI method comprises the Chemical Inherent Safety Index (CSI) and Process Inherent Safety Index (PSI) to assess a whole chemical process from a holistic perspective, and for this process, it reflected a global score of 28. Specifically, CSI and PSI delivered scores of 16 and 12, respectively. The analysis showed that the most significant risks are related to TTIP handling and its physical-chemical properties due to its toxicity and flammability. Insights about this process′s safety performance were obtained, indicating higher risks than those from recommended standards.

Evaluation of Algae-Based Biodiesel Production Topologies via Inherent Safety Index (ISI)

Increasing energy needs have led to soaring fossil fuel consumption, which has caused several environmental problems. These environmental aspects along with the energy demand have motivated the search for new energy systems. In this context, biofuels such as biodiesel have been developing into a substitute for conventional fuels. Microalgae are considered a promising option for biodiesel production due to their high lipid content. Therefore, it is important to analyze the technical aspects of the biodiesel production system. In this work, the inherent safety analysis of three emerging topologies for biodiesel production from microalgae was performed using the inherent safety index (ISI) methodology. Selected topologies include biodiesel production via lipid extraction and transesterification, in-situ transesterification, and hydrothermal liquefaction (HTL). The results revealed that the processes are inherently unsafe achieving total inherent safety index scores of 30, 29, and 36. The main risks in the cases were associated with the chemical safety index. Operating conditions represented no risk for topologies 1 and 2, while for topology 3 pressure and temperature were identified as critical variables. In general, topology 2 showed better performance from a safety perspective.

Inherent Safety Analysis and Sustainability Evaluation of Chitosan Production from Shrimp Exoskeleton in Colombia

Waste valorization strategies are key to achieve more sustainable production within the shrimp industry. The crustacean exoskeletons can be potentially used to obtain value-added products such as chitosan. A comprehensive analysis including both safety and sustainability aspects of chitosan production from shrimp shells is presented in this study. The inherent safety analysis and sustainability evaluation was performed using the Inherent Safety Index (ISI) methodology and the Sustainable Weighted Return on Investment Metric (SWROIM), respectively. The process was designed for a processing capacity of 57,000 t/year. The return on investment (%ROI), potential environmental impact (PEI output), exergy efficiency, and the total inherent safety index (ITI) were used as indicators to evaluate process sustainability. The total inherent safety index was estimated at 25 indicating that the process is inherently unsafe. The main process risks were given by handling of flammable substances, reactivity, and inventory subindices. The overall sustainability evaluation showed a SWROIM of 36.33% indicating that the case study showed higher weighted performance compared to the return on investment metric of 18.08%.

Evaluating the Sustainability and Inherent Safety of a Crude Palm Oil Production Process in North-Colombia

The African palm is the main source of vegetable oil worldwide, representing about 29.60% of the total oil and fat production around the world. The rapid expansion of this sector has faced several concerns related to environmental and social aspects that have driven the search for sustainable alternatives. In this work, the inherent safety analysis and sustainability evaluation for the crude palm oil production process was performed using the inherent safety index (ISI) method and the sustainable weighted return on investment metric (SWROIM), respectively. The process was designed for a processing capacity of 30 t/h of palm bunches and under North-Colombian conditions. Three technical indicators were considered to evaluate the process sustainability including exergy efficiency, potential environmental impacts output (PEI output), and the total inherent safety index (ITI). The economic factor is directly considered since the SWROIM is an extension of the conventional return on investment (ROI). The resulting ITI at 11 indicated an inherently safe process, and the highest risk was observed for the process equipment safety subindex. The SWROIM reached a higher value (53%) compared to the conventional ROI (49.39%), which suggests positive impacts on sustainability. The novelty of this work lies in detecting the inherent risks and providing a decision making criteria for this project through a complete evaluation that relates economic, energy, environmental, and safety criteria.

Process Analysis of Hydrogen Production via Biomass Gasification under Computer-Aided Safety and Environmental Assessments.

The growing awareness to advance new ways to transform renewable materials for producing clean fuels, under technical and sustainable viability, is evident. In this regard, hydrogen arises as one of the cleanest and energetic biofuels in the market. This work addresses the modeling and evaluation of a biomass gasification topology employing process simulation along with an environmental and inherent safety analysis. The presented pathway considered two renewable raw materials (cassava and rice waste) based on their vast availability in north Colombia regions. We employed Aspen Plus process simulation software to model the process, setting biomasses (and ash content) as nonconventional solids in the software and inclusion of FORTRAN subroutines for handling solid properties. Otherwise, the environmental evaluation was performed applying the waste reduction algorithm (WAR). At the same time, safety assessment involves a comprehensive approach based on the inherent safety index (ISI) and the process route index (PRI) methods. Data generated from the implementation of rigorous process simulation of biomass gasification allowed us to determine the needed aspect for performing process analysis methodologies. Results revealed that this topology generates a total flow of 3944.51 kg/h with more than 97% vol of H2, from the sustainable use of 19,243 kg/h of cassava waste and 15,000 kg/h of rice straw. From the environmental viewpoint, the process showed moderately to a high overall rate of potential environmental impacts (PEIs), with a higher contribution from process sources than energy sources. It indicates that most of the generated impacts would come from self-operation than from the energy supply generation. In the case of process safety, the topology obtained an ISI score of 35, which represents that modeled gasification would operate below 50% of the expected neutral standard for a physical–chemical process. Complementing the safety evaluation, the obtained PRI suggests that compared to other processes, the analyzed topology shows relatively adequate performance considering the nature of this type of process.

Inherent safety analysis of the UO2 fueled pebble lattice at the RDE using SRAC2006 module of PIJ

Reaktor Daya Eksperimental (RDE) is type of High Temperature Gas Cooled Reactor (HTGR) with nominal power 10 MWth that uses pebble bed type of sperical fuel. In the development of the RDE core design, as the earliest stage is to study characteristic of the fuel pebble latice cell, mainly related to the inherent safety. In this study, the inherent safety analysis to the transient effect of fuel temperature and water ingress in the pebble fuel lattice on RDE design core has been done by using Standard Reactor Analysis Code (SRAC2006) Probability I J (PIJ) module. In addition, the nuclide content in the spent pebble fuel lattice was also analyzed. PIJ is code based on the collision probability method applicable to analyze the change of k-inf value when transient occurs at certain fuel burn up point. The analysis was performed to the 17.00% and 8.50% enrichment of UO2 fuel pebble at varying levels of uranium heavy metal loading, i.e 3, 5, 7, and 9 gram. The k-inf value of the fuel pebble lattice has been calculated using branching burn up mode module PIJ through double heterogenity model. Calculation results showed that the higher loading level of heavy metal of uranium then the k-inf value will be smaller. The transient with increasing of the temperature at each particular burn up point or the occurrence of water ingress will also decreas in the k-inf value of fuel pebble lattice. From the analysis result, it can be concluded that pebble lattice fueled with 17% enrichment of UO2 on RDE has inherent safety properties i.e. the decreasing of k-inf value if transient temperature occurs. And when there is water ingress, the inherent safety characteristeic is shown by pebble lattice with maximum loading of 9 g uranium heavy metal.. The percentage of the nuclide content in spent fuel of pebble latice on RDE is similar to the PWR lattice, so it is not possible for a large number of plutonium production. At the transient by increasing of temperature, there are no significant increasing of gaseous fission product production (Xe-135, I-135, Sm-149, Pm-149).

Diffusion-Based Finite Element Method to Estimate the Reactivity Changes due to Core Deformation in an SFR

Thermomechanical effects, irradiation, and structural restrictions result in very tangled behavior of assemblies in sodium-cooled fast reactors (SFRs). Reactivity feedback caused by the assembly behavior (deformation or distortion) is one of the key parameters in the inherent safety analysis of fast reactor systems. However, to date there has been no accurate and efficient deterministic way to compute directly the reactivity changes by actual local perturbation. This paper evaluates the feasibility of applying the Galerkin finite element method (GFEM) based on linear shape functions to estimate reactivity changes due to local core deformations in SFRs. Assessment of reactivity changes is conducted for six types of deformation scenarios of the two-dimensional prototype Gen-IV SFR. Uniform expansions and local deformations are included in the scenarios. The results from the multigroup diffusion equation based on the GFEM are compared with references calculated by MCNP5. The study shows that diffusion analysis based on the GFEM with linear shape functions can properly estimate reactivity changes by core deformation in the fast reactor with ~13% relative error of Δρ.

Modeling of natural circulation for the inherent safety analysis of sodium cooled fast reactors

The paper discusses a set of developed integrated one-dimensional models of thermal-hydraulic processes that contribute to the removal of decay heat in a BN-type reactor. The assumptions and constraints involved in one-dimensional equations of unsteady natural convection in closed circuits have been analyzed. It has been shown that the calculated values of the primary circuit sodium temperature and flow rate in conditions with a loss of heat sink and with a forced circulation of the primary coolant are in a reasonable agreement with the results of a benchmark experiment in the PHENIX reactor. The model makes it possible to assess the effects general thermophysical and geometrical parameters and the selected technology have on the efficiency of passive heat removal by the natural coolant convection in the reactor tank and in the emergency heat removal system's intermediate circuit and by the heat transfer through the reactor vessel. The model is a part of an integrated algorithm used to assess the inherent safety level of advanced fast neutron reactors and is intended primarily to develop, at the early conceptual design stage, the recommendations and requirements with respect to the reactor equipment parameters leading to an increase in the reactor inherent safety. The model will be used to identify the set of quantitative thermal-hydraulic criteria that have an effect on the dynamics of emergency transients leading to a potential loss of integrity by the reactor safety barriers, and to formulate such limits for the defined criteria as would cause, if observed, the requirement for the safety barrier integrity to be met under any combination of the accident initiating events.

Моделирование естественной циркуляции для анализа внутренней самозащищенности быстрых натриевых реакторов

Моделирование естественной циркуляции для анализа внутренней самозащищенности быстрых натриевых реакторов

Design study of long-life small modular sodium-cooled fast reactor

Summary This paper presents a new design for a small modular sodium-cooled fast reactor core with an optimized lifetime and reactivity swing through the analysis of various breed-and-burn strategies and its neutronic analyses in terms of active core movements, isotopic mass balance, kinetic parameters, and inherent safety. The new core design aims at a power level of 260 MW with a long lifetime of 30 years without refueling and a reactivity swing smaller than 1000 pcm. Starting from five initial candidate cores with various breed-and-burn strategies, an optimum core was selected from a combination of the two candidates that shows a proper breeding behavior with the optimized uranium enrichment in the low-enriched uranium region and the optimized size of the blanket region. The depletion analysis of the new core provides various reactor design parameters such as the core multiplication factor, breeding ratio, heavy metal mass change, power distribution, and summary of neutron balance. In addition, the perturbation analysis provides the reactor kinetic parameters and reactivity feedback coefficients for the inherent safety analysis of the core. The integral reactivity parameters of the quasi-static reactivity balance analysis demonstrate that the new core is inherently safe in cases of unprotected loss of flow, unprotected loss of heat sink, and unprotected transient over power. Copyright © 2016 John Wiley & Sons, Ltd.

Multi-objective optimization of a cascade refrigeration system: Exergetic, economic, environmental, and inherent safety analysis

Inherently safer design is the new approach to maximize the overall safety of a process plant. This approach suggests some risk reduction strategies to be implemented in the early stages of design. In this paper a multi-objective optimization was performed considering economic, exergetic, and environmental aspects besides evaluation of the inherent safety level of a cascade refrigeration system. The capital costs, the processing costs, and the social cost due to CO2 emission were considered to be included in the economic objective function. Exergetic efficiency of the plant was considered as the second objective function. As a measure of inherent safety level, Quantitative Risk Assessment (QRA) was performed to calculate total risk level of the cascade as the third objective function. Two cases (ammonia and propane) were considered to be compared as the refrigerant of the high temperature circuit. The achieved optimum solutions from the multi–objective optimization process were given as Pareto frontier. The ultimate optimal solution from available solutions on the Pareto optimal curve was selected using Decision-Makings approaches. NSGA-II algorithm was used to obtain Pareto optimal frontiers. Also, three decision-making approaches (TOPSIS, LINMAP, and Shannon’s entropy methods) were utilized to select the final optimum point. Considering continuous material release from the major equipment in the plant, flash and jet fire scenarios were considered for the CO2/C3H8 cycle and toxic hazards were considered for the CO2/NH3 cycle. The results showed no significant differences between CO2/NH3 and CO2/C3H8 with respect to economic and exergy efficiency objectives. But the CO2/NH3 cycle was the inherently safer cascade system in comparison with the CO2/C3H8 one. This is mainly due to the jet fire scenario for the CO2/C3H8 cycle in which the effects are very severe in the farther distance as well as the areas close to the release point.

Incorporating Exergy Analysis and Inherent Safety Analysis for Sustainability Assessment of Biofuels

In the design of chemical/energy production systems, a major challenge is how to quantify the sustainability of the systems. Concerns on economic return and environmental impacts have been well received by researchers and practitioners. However, the irreversibility of the process has not been taken into consideration yet. Based on the first and second laws of thermodynamics, exergy analysis allows accounting for irreversibility in the process and provides a detailed mechanism for tracking the transformation of energy and chemicals. Sustainability assessment in the societal dimension is mostly a “soft” activity, as the aspects to be considered and the method of evaluation are frequently subjective. How to assess the societal impact of a process in the early design stage remains as a challenging issue. This paper will present a sustainability assessment method incorporating economic, environmental, efficiency, and societal concerns. The efficiency assessment is conducted through exergy analysis, while the s...

Selection of inherently safer process routes: a case study

Increased public concern about safety issues and stringent environmental standards has led plant designers to consider inherently safer design. The term ‘inherently safer’ implies that the process is safe by its very nature and not externally constrained to be safe by the use of add-on systems and devices. Such opportunities for developing inherently safer process are highest in the early stages of design. Constraints such as time, lack of knowledge and inadequate inherent safety analysis tools are often cited as obstacles to development and implementation of inherently safer design. In this paper, we describe an inherent safety analysis methodology that can be applied in the early stages of process development. The methodology is based on an inherent safety index for comparing process routes and heuristics for identifying hazards and generating alternative designs. This methodology has been implemented as one module in iSafe, an intelligent system that automates inherent safety analysis. One key benefit of iSafe is substantial reduction in the time and effort required to perform safety analysis. Automation of the inherent safety analysis also makes it more thorough and detailed, minimizes or eliminates human errors, facilitates documentation and makes the study results available online for detailed safety analysis and review in the later stages of process design. The details of inherent safety analysis at the route selection stage are discussed in this paper and illustrated by comparing competing processes for acetic acid manufacture.

Expert System for the Design of Inherently Safer Processes. 1. Route Selection Stage

In the past, the design and engineering of process plants has been driven by factors related to economics followed by operability, reliability, maintainability, and safety with an emphasis on engineering budget and time. Decisions concerning safety during the evaluation phase focused on risk reduction instead of reducing or eliminating hazards. Increased public concern on safety issues and stringent environmental standards have led plant designers to consider inherently safer and environmentally friendlier processes. Opportunities for developing such processes are highest in the early stages of design. Constraints such as time and lack of inherent safety analysis tools have been cited as hurdles to the development and implementation of an inherently safer design. We address the need for inherent safety support tools in this two-part series by developing a systematic methodology for automating inherent safety analysis in the route selection and flowsheet development stages of process design. In the first part, we describe how the knowledge required for inherent safety analysis during route selection can be formalized in the form of expert rules. We also present a new inherent safety index for ranking of process routes and a graphical method for analyzing reaction networks. We illustrate the methodology by using it to compare three routes for phenol manufacture. In the second part, we describe the methodology for inherently safer flowsheet design and the implementation of an expert system that automates the methodology.

Expert System for the Design of Inherently Safer Processes. 2. Flowsheet Development Stage

In part 1 of this series, we proposed a systematic methodology for inherent safety analysis during the process route selection stage. In this part, we present the methodology for inherent safety analysis during the flowsheet development stage. An expert system, called iSafe, that implements the methodology has also been developed. One key benefit of automation is substantial reduction in the time and effort required to perform safety analysis. The architecture of iSafe is described and illustrated using an acrylic acid process case study.