Operation Of Chemical Plants Research Articles

Generating optimal overlapping subsystems for distributed statistical fault detection subject to constraints

Fast and accurate detection of faults is essential for the safe and cost-effective operation of chemical plants. Large scale process systems can potentially be affected by a wide variety of faults. An effective approach for detecting faults in such systems is to first divide or decompose the system's sensors into subsystems and to then implement a statistical monitoring method in each of the subsystems. The detection performance of such distributed multivariate statistical process monitoring methods depends strongly on the decomposition of the system's sensors into subsystems. In our previous work, we developed a simulation optimization method, called Performance Driven Agglomerative Clustering, which uses a greedy search strategy, based on clustering algorithms from graph theory, to find a decomposition of the system's sensors into subsystems for which the detection performance of a distributed monitoring method is near optimal. It is possible that the detection performance can be further improved by allowing a sensor to be part of multiple subsystems in the decomposition. User defined requirements may also place constraints on the decomposition of the sensors into subsystems. In this work, we propose the Extended Performance Driven Agglomerative Clustering method which allows to incorporate constraints and sensors to be allocated to multiple subsystems. To demonstrate its effectiveness, the proposed method is applied to the benchmark Tennessee Eastman Process.

Ecological and toxicological assessment of the influence of the chemical enterprise on soil

Technogenic pollution of the territory firstly leads to decrease of productivity of the land, since the main part of the technogenic loading, as a result of such pollution, assumes to the soil and vegetation. Soils those have been contaminated are characterized by changed structural and physical-and-chemical properties, which does not allow them to be used for economic purposes. To detect the technogenic loading on the soil as a result of the chemical plant operation, soil quality studies were carried out using the bio-testing method. The most informative data towards ecological danger of ecosystem pollution is the results of the determination of phytotoxicity for soil organisms. Such information can be obtained by an integral assessment of the biological usefulness of the habitat of organisms using the bio-testing method, which provides registration in controlled, standard conditions of the corresponding reactions of test organisms to the toxic effects of ecologically hazardous chemical compounds and their mixes. The following higher plants were selected as test cultures: Raphanus sativus L., Hordeum vulgare L. and Triticum aestivum L. As the test-response of higher plants, the energy of seed germination, the length of the sprout and the length of the root were taken into account. Four zones were selected for the research. The largest difference between the values of germination energy between control and experiment was observed on the results of a test-response to Hordeum vulgare L. in a sample of soil from zone Nr 4. The indicator of the toxic effect detected on the territory of zone Nr 4 - 43,64% reduction in the length of the roots relative to the control; 33.81% reduction in the length of the germs relative to the control based on the results of the test-response to Hordeum vulgare L. The soil sample from the zone Nr 1 showed no toxic properties in any test reaction (6.32% decrease in root length relative to control one, 5.68% reduction length of germs relative to the control one based on the results of the test reaction on Raphanus sativus L. Sample of soil from zone Nr 2 did not show toxicity (-45.26% decrease in root length relative to control one and 8.61% decrease in germination length relative to control one revealed by the results of the test-response to Raphanus sativus L. Soil samples from zone Nr 3 also showed no toxicity (3.83% decrease in root length relative to control and 11.02% reduction in germination length relative to control revealed by test-reaction results on Raphanus sativus L. The table value of the Student's criterion for the probability level is P = 0.5 and the number of measures of freedom 58 is 2.01. The calculation of the actual value of Student's criterion for the length of the roots (2.68) and the germs (2.05) showed an excess of the table value based on the results of the test-response on Hordeum vulgare L. in the soil sample from zone Nr 4, what confirms the presence of toxic properties of the soil. In order to assess the risk of soil contamination, the "measure of soil contamination" indicator was used in accordance with defined levels of inhibition of growth processes, the quantitative characteristics of which are expressed by the soil contamination coefficient, while the soil contamination coefficient is differentiated according to the levels of inhibition of growth processes. According to the calculated data, in the sample Nr 4, the phytotoxic factor or percentage reduction in the length of the roots relative to the control is 43.64% based on the results of the test-response to Hordeum vulgare L. By level of contamination, the soil is moderately polluted, belongs to the III class of quality and shows the measure of contamination of 1,3. Soil samples №1, №2 and №3 showed no toxicity (А˂20), i.e., they are non-contaminated and belong to the I class of quality. Therefore, for the integrated assessment of soil quality, in addition to chemical indicators, it is recommended to use integral indicators, in particular phytotoxicity of the soil, which characterizes the biological usefulness of the habitat of organisms.

STUDENTS BUILDING DIDACTIC EXPERIMENTS AS A TOOL FOR TEACHING UNIT OPERATIONS AND PROCESS CONTROL FOR CHEMISTRY TECHNICIANS

The qualified preparation of technician chemistry students who will act directly in the operation and control of industrial chemical plants is a permanent challenge in the teaching-learning process, since such activities require a broad view of the process and a sum of knowledge’s areas such as unit operations, instrumentation and industrial process control. An alternative to better understand these chemical engineering subjects within the technician chemistry course is the use of didactic experiments, which aims to provide an approximation of the taught content in the classroom with practical operation in a dynamic way, facilitating the teaching-learning process. In this sense, this work aimed to propose to the students of the technician chemistry course integrated to high school to use their creativity, combined with the technical concepts studied in the classroom, to build didactic experiments of unit operations within the following topics: heat exchanger, adsorption, humidification and drying. The results were evaluated in the form of performance technical data and qualitative questionnaire. Results have evidenced the positive character in the teaching-learning process of the operating principles of the unit operations, besides allowing the students a direct contact with process control and industrial instrumentation.

The “projectness” of MOC

The safety community, bolstered by the PSM regulations, has emphasized the importance of proper management of change, “MOC,” to ensure safe, reliable and economic operation of chemical plants, refineries and increasingly, on‐ and off‐shore pipelines, and installations.The majority of MOCs involve physical changes to facilities—a much smaller fraction of MOCs addresses procedure‐only changes, document‐only changes or organizational changes. Physical changes to facilities are implemented in different contexts such as maintenance work orders, project work orders, small capital projects, and large capital projects. Each of these contexts has its own notion of a “work process,” and the larger ones are very project‐centric.Changes to facilities always involve BOTH an MOC and a “work process.” Some sites emphasize the work process aspects, driven by the existence of Enterprise Resources Planning systems, and handle the MOC essential elements poorly. Other sites burden the MOC process with many capital‐projects aspects and create a very complex change management environment. Surely there must be a happy medium?This article analyzes data from case studies from actual implementation projects, identifies gaps and makes recommendations on the best practice for conjoining MOC and other work processes. © 2018 American Institute of Chemical Engineers Process Process Saf Prog 38:e12021, 2019

Scheduling‐informed optimal design of systems with time‐varying operation: A wind‐powered ammonia case study

The time‐varying operation of chemical plants offers economic advantages, particularly in the presence of time‐sensitive electricity markets and renewable energy generation. However, the uncertainty and short‐timescale variability associated with renewable energy production, as well as the nonconvex process and cost models typically associated with chemical processes, make finding the optimal design of such systems challenging. In this work, a new approach is presented to finding the optimal design of systems with time‐varying operation, called scheduling‐informed design, whereby the optimal operation of many designs is determined and the resulting cost correlations into the optimal design problem are embedded. This method is applied to a case study of wind‐powered ammonia generation and showed that it greatly improves the computational tractability of the optimal design problem and predicts with greater accuracy operating costs realized because of uncertainty in forecasting. © 2018 American Institute of Chemical Engineers AIChE J, 65: e16434 2019

Packed Bed Performance Analytics Based on Gamma Scans

Refinery and chemical plant operations depend heavily on distillation and separation towers. Tower gamma scanning is well established in the process industries as a qualitative tool to help troubleshoot towers. Advancements in data analysis have led to a quantitative approach in expressing gamma scan data in numerical terms easily understood by process and operations engineers.For packed towers, a grid-scan of 3 or 4 equal-distant scans crossing through the beds of packing would typically be used to investigate the quality of liquid distribution. The conventional approach to “analyzing” a gamma scan has been to visualize how well the scan data from the individual scans matched each other or how well they “overlaid” with each other. This is a totally subjective analysis lacking consistency, open to varying interpretation and does not translate well from tower-to-tower. Therefore, the resulting conclusions from this approach can be very ambiguous regarding the magnitude of any detected liquid mal-distribution.An alternative analytical approach, termed PackView™, has been developed whereby a relative density scale is calculated from data that the grid-scan provides. The density scale begins at the density of the dry or non-operating packing. The density scale displays the calculated density of liquid retained in the bed of packing based on the scan data results.Another calculation by which to put the liquid distribution into perspective and to get a measure on the useful capacity of the packing is to calculate the liquid holdup fraction or liquid volume fraction. If the measured liquid retention density is divided by the process liquid density at bed conditions (the liquid density at the actual operating temperature and pressure), liquid holdup or liquid volume fraction can be established. A comparison of the liquid holdup fraction to the packing operating capacity curves provides an objective appraisal of current operating capacity.It is always easier to understand and discuss technical issues when quantitative information can be used to compare operational parameters with engineering design. This advanced analysis provides a new method of extracting quantitative information from gamma scan data to diagnose and characterize the operation of distillation and separation towers. It is our goal that using the advanced analytics presented will improve the value of gamma scan data and facilitate improvements in the operation of mass transfer equipment.

Process Modeling, Simulation and Optimization: From Single Solutions to a Multitude of Solutions to Support Decision Making

AbstractBesides experimentation process simulation is a key technology in process development. Process simulation supports design, analysis and operation of chemical processes and plants. A systematic use of process simulation and optimization in the process development workflow is beneficial for both the process model and experiments and enables to be more efficient and effective in process design. In the following it will be discussed how the application of process simulation and optimization has to be broadened to provide decision support for process development.

Impact of chemical plant start-up emissions on ambient ozone concentration

Flare emissions, especially start-up flare emissions, during chemical plant operations generate large amounts of ozone precursors that may cause highly localized and transient ground-level ozone increment. Such an adverse ozone impact could be aggravated by the synergies of multiple plant start-ups in an industrial zone. In this paper, a systematic study on ozone increment superposition due to chemical plant start-up emissions has been performed. It employs dynamic flaring profiles of two olefin plants’ start-ups to investigate the superposition of the regional 1-hr ozone increment. It also summaries the superposition trend by manipulating the starting time (00:00–10:00) of plant start-up operations and the plant distance (4–32 km). The study indicates that the ozone increment induced by simultaneous start-up emissions from multiple chemical plants generally does not follow the linear superposition of the ozone increment induced by individual plant start-ups. Meanwhile, the trend of such nonlinear superposition related to the temporal (starting time and operating hours of plant start-ups) and spatial (plant distance) factors is also disclosed. This paper couples dynamic simulations of chemical plant start-up operations with air-quality modeling and statistical methods to examine the regional ozone impact. It could be helpful for technical decision support for cost-effective air-quality and industrial flare emission controls.

The Study on Degradation of Stainless Steel Clad Plate Used for a Shift Reactor in Coal Chemical Plant

Shift reactors are widely used in the petroleum and chemical industries, and especially in the coal chemical plants. The degradation of the reactor is critical to the safe operation of coal chemical plant. In this paper, a shift reactor after 8 year service was chosen. The test block taken from the reactor cylinder with the stainless steel clad plate was used and the test samples from the test block were prepared. And then, chemical composition analysis, metallographic examination, tensile and hardness tests were performed. The scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) method were used to study the degradation and degradation mechanism of the reactor. The metallographic analysis results show that there were a large number of carbides segregated in the grain boundary and the intergranular cracks were observed for the samples in the weld zone of the stainless steel clad plate. The SEM and EDS results indicate that the corrosion medium (i.e. polythionic acid) was found in the fracture surface of the samples from the weld zone of the stainless steel clad plate. The XRD test results show that the tensile residual stress occurred for the welding of the stainless steel clad plates. It is found that the degradation mechanism of the shift reactor was due to the polythionic acid stress corrosion cracking.

Design of Integrated Solar Thermal Energy System for Multi-period Process Heat Demand

This paper presents a new methodology for integrating renewable energy sources such as solar with chemical process utility demand. In chemical plant operations, the demand for utilities, as well as available process heat loads, are sometimes seasonal or multi-period in nature. Also, the availability of renewable energy such as solar, is time of day dependent as well as seasonal, i.e. time of year dependent. Therefore, in order to fully harness the economic and environmental benefits associated with the use of solar thermal energy, an approach which systematically integrates solar thermal radiation with process heat demand and other sources of utilities in chemical plants, while considering the multi-period profile of both the utility sources and the process streams need to be developed. The approach adopted in this paper, entails the use of the multi-period version of the stage-wise superstructure with an objective function involving a simultaneous minimisation of the annualised investment costs and annual operating cost of the network. The utility sources considered include solar and fossil fuel. The fossil fuel is included as a back-up depending on how much of the process heat demand is satisfied by solar energy. For the solar energy source, concentrated solar thermal collector is considered for both direct and indirect Heat Integration including thermal energy storage. In the example considered, a reasonable amount of cost savings was obtained when compared to the case without solar thermal integration.

Life‐safety concerns in chemical plants

The safety and health standards of the Occupational Safety and Health Act do not specifically address life safety in chemical plants, other than requiring owners and operators to “provide a safe place to work” and to ensure that “employees may evacuate the workplace safely.” NFPA 101 would classify chemical plants as high‐hazard industrial occupancies, and a primary concern is to ensure “minimal danger to occupants in case of fire or other emergency before they have time to use exits to escape.” NFPA 1 also requires that the design and operation of buildings and facilities “provide an environment for the occupants that is reasonably safe from fire and similar emergencies, for the amount of time needed to evacuate.” Thus, most life‐safety requirements are concerned with safe exit.There are, however, other life‐safety hazards that should be of concern to chemical plant owners and operators. They include many single‐exit locations, such as the upper levels on distillation/fractionation columns, scrubbers, and other tall equipment; elevated work platforms as atop multistory buildings and smokestacks; platforms above tank cars, tank trucks, and hopper cars; at the head of bucket elevators; work spaces above false ceilings; and ladder‐access roofs over operating areas. Also, chemical‐plant life‐safety hazards include flash fire (flammable vapors and combustible dusts); releases of toxic gases and vapors; and vessel rupture from runaway reaction or other causes of overpressure. This article presents practical countermeasures for these life‐safety hazards. © 2016 American Institute of Chemical Engineers Process Saf Prog 35: 18–25, 2016

Does Global Climate Change Affect Air Pollution in Illinois?

This policy brief provides an overview of research on climate change and air pollution, and it discusses the implications for Illinois. The researchers first describe the effects of pollution and then look at trends in Illinois relative to the whole United States. They then describe estimates of the effects of climate change on local pollution, and the effects of pollution on health. Focusing on ground-level ozone—which is projected to rise in the future—they use those estimates to calculate the effects of climate change on the number of “life-years lost” for the three million residents around Chicago. They calculate that the social costs of the mortality increase associated with increased ozone levels in the Chicago area could exceed $250 million annually. The clear scientific consensus is that the Earth’s climate is changing. These changes include an increase in global average temperatures, a rise in the sea level, and an increase in weather extremes such as floods and droughts in the coming decades. Air pollution is believed to have large negative effects on human health. Fortunately, with the exception of ozone, air pollution levels have been declining in Illinois over the past 15 years. However, climate change and atmospheric pollution models predict that ozone levels will increase over the next several decades, especially in densely populated areas like Chicago. It therefore may be beneficial to take steps now to discourage activities that contribute to ground level ozone, such as the operation of chemical plants, power plants, and cars. Doing nothing, by contrast, risks incurring significant costs in the future.

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The emulation and real-time simulation in the teaching and learning processes or the development of process control research, allows controlled experimentation without having the real system. This paper shows the emulation of one of the most significant operations in chemical plant operations: distillation columns. The emulator development is performed on the columns model in an application platform based on real-time Linux composed of RTAI, RTAI-Lab, and RTAI-XML projects. In response, emulation product composition under disturbances in the supply is obtained. Emulation results are compared with the simulation results obtained in MATLAB and show that the response of change composition inputs or the perturbation changes are close to the response obtained with MATLAB simulation

Development of Operating Instructional System Using AR Technology in Chemical Plants

In recent years, Japan's industrial accident rate has shown an increasing trend. This is especially remarkable due to chemical industrial complexes. As is well-known, many kinds of hazardous materials are being controlled in chemical facilities. If a serious accident occurs, there is the potential for severe damage to employees and the residents of local communities. A primary factor in these accidents is the lack of safety awareness, safety knowledge, safety management system deficiencies, and insufficiency of safety ethics. In addition, industrial technology is highly diversified and complicated. As a result, operators cannot grasp the whole situation of the abnormalities and potential crises present. In other words, operators are unable to take the appropriate safety measures to prevent accidents. In some cases, equipment failure shave developed into serious accidents due to incorrect operation by the operator. This paper presents systems that provide information to operators by using augmented reality (AR) technology in chemical plants. AR can enhance real-world environments using virtual objects such as computer graphics. This system can help plant operators to confirm procedures in order to ensure proper operation. Furthermore, the operator can recognize the equipment to be operated properly using a tablet PC with a built-in camera. The proposed system can provide the plant information based on the dynamic simulator (DS). In an emergency, chemical plant operators are required to make quick decisions to prevent the escalation of an accident. To convey accurate indication information of the work, it is useful to recognize target equipment using AR marker in addition to the output information by individual voice from control room. Our developed systems can support chemical plant operators to make quick decisions and to follow correct operating procedures.

Neighbouring-Extremal Control for Steady-State Optimization Using Noisy Measurements

Optimal operation of chemical plants is usually accomplished by finding the optimal steady state using the nominal set of disturbances and model parameters. The optimization is in most cases model based and therefore subject to uncertainties. This may lead to sub optimal control actions with significant economical losses. One idea to tackle this problem is to use the available measurements to adapt the inputs during operation in a feedback control scheme. This can be achieved by a neighbouring extremal controller that updates the inputs based on the deviation of the measured outputs from their nominal value. In this paper we generalize the neighbouring extremal control design that has been presented in the literature to explicitly handle measurement noise and implementation errors. The benefits of our method are illustrated in a case study where we show that the sensitivity of the controller performance to measurement noise is considerably reduced.

NDT Reliability in the Organizational Context of Service Inspection Companies

AbstractThe focus of NDT reliability research in the past was in the field of two high risk industries: (atomic) power plants and aircrafts. The responsible organizations have been well aware of the risks and founded projects to understand and optimize critical steps during production, operation and maintenance. But the use of NDT is not limited to these two fields. The risks during operation of chemical plants, trains or windmills are different from the area above but evident. The coverage by legal regulations is relatively low. Instead of this owner responsibility, product liability and financial issues are the driving forces to do inspections and to use non-destructive testing. The different targets and financial issues influence the practice of NDT-inspections. A survey of this practice and its results are shown.

A mathematical programming model for optimal layout considering quantitative risk analysis

Safety and performance are important factors in the design and operation of chemical plants. This paper describes the formulation of a mixed integer nonlinear programming model for the optimization of plant layout with safety considerations. The model considers a quantitative risk analysis to take safety into account, and a bowtie analysis is used to identify possible catastrophic outcomes. These effects are quantified through consequence analyses and probit models. The model allows the location of facilities at any available point, an advantage over grid-based models. Two case studies are solved to show the applicability of the proposed approach.

Application of partially diabatic divided wall column to floating liquefied natural gas plant

The offshore operation of chemical plant requires the compactness of process equipments due to its harsh environment. A DWC (divided wall column), a compact ternary separator, is a good candidate for distillation process in the offshore operation. In this study the DWC is applied to the offshore FLNG (floating liquefied natural gas) plant, but high utility cost is required in the application because of the large difference of boiling points among feed components. A partially diabatic DWC is proposed for the reduction of the operating cost here, and its design procedure is presented along with performance and economic evaluations and the examination of thermodynamic efficiency as well. The heating duty of the proposed DWC including tray heat transfer is 35% less than that of the conventional system, and the cooling duty is 18% less. The evaluation indicates that some 16% less utility cost is used in the DWC compared with the conventional system, though 7% more investment is required. The exergy loss is reduced by 12%, and the thermodynamic efficiency is improved by 3.3 percentage point over the conventional system.

Quality assurance and quality control of pressure relief systems

Pressure relief systems are important for the safe operation of refineries and chemical plants. They are generally considered to be the last line of defense against abnormal operation which could lead to serious accidents, resulting in loss of life and property. To ensure that the system provides proper protection for the range of potential process deviations, it is important to properly size the pressure relief systems considering all the possible applicable overpressure scenarios. Quality Assurance (QA) and Quality Control (QC) are important work processes which help to ensure that relief systems are properly designed and documented. This article discusses best practices regarding QA and QC protocols for pressure relief systems. Definitions are given for the terminology used for the QA/QC process of pressure relief system studies. A sample workflow of a typical pressure relief system analysis is also provided. Different steps of the pressure relief analysis process are briefly discussed, and sample work instructions are given for each step. An example set of documentation required for a pressure relief system study, as well as a recommended sequence of documents therein, are described. Work instructions are given for the QA/QC process in the different sections of the studies—system information, overpressure contingency analysis, relief rate calculation and relief device sizing, deficiency identification, and final documentation. Lastly, some common mistakes which have been observed during the QA/QC of numerous studies of pressure relief systems from commercial refineries and chemical plants are reviewed. © 2014 American Institute of Chemical Engineers Process Saf Prog 33: 136–142, 2014

Online Detection of Shutdown Periods in Chemical Plants: A Case Study

In process industry, chemical processes are controlled and monitored by using readings from multiple physical sensors across the plants. Such physical sensors are also supplemented by soft sensors, i.e. adaptive predictive models, which are often used for computing hard-to-measure variables of the process. For soft sensors to work well and adapt to changing operating conditions they need to be provided with relevant data. As production plants are regularly stopped, data instances generated during shutdown periods have to be identified to avoid updating these predictive models with wrong data. We present a case study concerned with a large chemical plant operation over a 2 years period. The task is to robustly and accurately identify the shutdown periods even in case of multiple sensor failures. State-of-the-art methods were evaluated using the first half of the dataset for calibration purposes and the other half for measuring the performance. Results show that shutdowns (i.e. sudden changes) can be quickly detected in any case but the detection delay of startups (i.e. gradual changes) is directly related with the choice of a window size.