Operation Of Process Plants Research Articles

Study of radioactive contamination in silts and aerosols at Aldama City, Mexico, due to the operation of a yellow-cake processing plant

The city of Aldama, Chihuahua, Mexico is located 30 km NNE of Chihuahua city. Three high-volume collectors with PM10 heads were placed in specific locations in Aldama during the year 2011 to measure radioisotope concentrations in the air. The city area of 16 km2 was divided into 64 squares of 500 × 500 m. At the vertices of the grid, silt samples were taken between January and June 2011, before the rains began. The concentrations of natural, cosmogenic, and anthropogenic radioactive isotopes were calculated in both filters and silts samples. The isotopes selected for the measurement were 238U, 232Th, 7Be, 137Cs, and 40K. Measurements of PM10 and silts were performed during 2011, coinciding with the accident at Fukushima, Japan, on March 11. For this reason, we could see the 137Cs in PM10 increase between April and July; with the arrival of the rains, the 137Cs concentration began to decrease in the air. The concentration of PM10 measured by the equipment located at the Mexican Uranium plant (URAMEX, initials in Spanish) that was processing radioactive ores exceeded the standard values in February and March, when the air velocity increases. At City Hall, the concentration of PM10 surpassed the value of the standard between May and July. This increased concentration is likely due to increased automobile traffic because City Hall is located in the city center. At a private home, the concentration of PM10 surpassed the standard on several days during the year because the home is located on the outskirts of the city, where most of the streets are not paved. Due to the high concentrations of PM10, especially at the collection point located at the private home, it is necessary to start taking steps to mitigate their spread before they cause health problems in the younger population and in older adults.Implications: The radioisotope content found in the PM10 confirms that the decision to place the Mexican Uranium plant (URAMEX, initials in Spanish) processing radioactive ores near the town of Aldama was not well thought out. Because the monitoring work was carried out in 2011 and coincided with the Fukushima accident, an increased concentration of 137Cs could be detected in the PM10. We made recommendations to the municipal authorities of the city to mitigate the concentration of particles in the air.

Increasing the Efficiency of the Fuel Use for Industrial Furnaces

The comparison data of different options of the internal use of the heat of effluent combustion products during the operation of high temperature thermal process plants (HTTP) have been given. The main factors that affect the efficiency of the heat use during the operation of HTTP have been defined. On the bases of balance equations the methods of the computation of the fuel saving at the preliminary material heating and the heating of burning components due to the regeneration of heat of effluent combustion products have been given. The influence of a coefficient of heat regeneration and a coefficient of the efficiently used heat of the working chamber on the value of the relative heat of effluent combustion products (appropriate diagrams and design ratio are given) was shown. The conclusion section gives the recommendations for the selection of the efficient method for the internal use of the heat of combustion products effluent from the working chamber from the standpoint of an increase in the HTTP productivity and fuel saving.

Reliable and Safe Operation of Process Plants

AbstractEine wettbewerbsfähige Herstellung chemischer Produkte erfordert größere Anlagen mit höheren Raum‐Zeit‐Ausbeuten, wofür häufig keine Erfahrungen zur Prozess‐ und Anlagentechnik vorliegen. Ein wirtschaftlicher Betrieb ist nur möglich, wenn mit einem stabilen Verfahren und einer robusten Ausrüstung Ausfälle und ungeplante Stillstände vermieden werden und hohe Betriebssicherheit die Anforderungen des Gesundheits‐ und Umweltschutzes gewährleistet. Der vorliegende Beitrag zeigt am Beispiel von Rührwerksanlagen, wie diese Ziele über eine ganzheitliche Betrachtung zusammengefasst und umgesetzt werden können.

Optimal operation of process plants under partial shutdown conditions

A systematic strategy for optimal plant operation during partial shutdowns is proposed. We consider the situation where one or more process units are shut down due to failure or maintenance but where the remaining units are able to continue operation to some degree. The goal of the strategy is to manipulate the plant degrees‐of‐freedom—during and after the shutdown—such that production is restored in a cost‐optimal fashion while meeting safety and operational constraints. Optimal control trajectories are obtained through the solution of a dynamic optimization problem. A novel multitiered optimization approach allows the prioritization of multiple competing objectives and the specification of trade‐offs between them. Uncertainty in the downtime estimate, a crucial parameter in shutdown optimization, is addressed through reoptimization. We employ a transient predictive control algorithm for implementing the computed control policy under feedback. © 2013 American Institute of Chemical Engineers AIChE J, 59: 4151–4168, 2013

Industrial applications of plasma, microwave and ultrasound techniques: Nitrogen-fixation and hydrogenation reactions

The MAPSYN project (Microwave, Acoustic and Plasma assisted SYNtheses) aims at nitrogen-fixation reactions intensified by plasma catalysis and selective hydrogenations intensified by microwaves, possibly assisted by ultrasound. Energy efficiency is the key motif of the project and the call of the European Union behind (NMP.2012.3.0-1; highly efficient chemical syntheses using alternative energy forms). The material (catalysis) and process innovations given in the literature for the two demonstration examples (of the project) are reviewed and added by the project's own ones derived from the latest state of the art. From there still a gap to industrialization needs to be closed which needs innovation as well on the level of process control and plant operation, finally opening gates to new business models (distributed production and modular plant-numbering up instead of scale-up). Such systemic solution shall be developed under the supervision of energy and cost analysis as well as life-cycle analysis to ensure following a holistic approach. This demands for a new science management not focusing only on the key innovation, but as well as on other assisting enabling technologies needed and for the systemic vision with plant view and process control – all centered around industrial reaction equipment.

Knowledge-Based Global Operation of Mineral Processing Under Uncertainty

In this paper, a novel knowledge-based global operation approach is proposed to minimize the effect on the production performance caused by unexpected variations in the operation of a mineral processing plant subjected to uncertainties. For this purpose, a feedback compensation and adaptation signal discovered from process operational data is employed to construct a closed-loop dynamic operation strategy. It uses the signal to regulate the outputs of the existing open-loop and steady-state based system so as to compensate the uncertainty in the steady-state operation at the plant-wide level. The utilization mechanism of operational data through constructing increment association rules is firstly described. Then, a rough set based rule extraction approach is developed to generate the compensation rules. This includes two steps, namely the determination of the variables to be compensated based on the significance of attributes in the rough set theory and the extraction of the compensation rules from process data. Based upon the operational data of the mineral processing plant, relevant rules are obtained. Both simulation and industrial experiments are carried out for the proposed global operation, where the effectiveness of the proposed approach has been clearly justified.

Modeling limestone reactivity and sizing the dissolution tank in wet flue gas desulfurization scrubbers

Sulfur dioxide (SO2) is one of the pollutant gases that result from energy conversion by coal and oil combustion. Limestone slurries are widely utilized in wet flue gas desulfurization (WFGD) processes. The evaluation of the reagent's reactivity is fundamental for process design and plant operation. The comparison of different limestone and dolomite rocks through dissolution experiments was realized by applying a model for second‐order kinetics. And a total of 12 different samples were tested, at three different size fractions. A simulation model was developed to identify each sample's impact on sizing the dissolution tank of a WFGD scrubber. A second‐order model was applied within the scrubber's dissolution tank range of operation at pH values between 4 and 5. The regression coefficients for the second‐order model were higher than 0.98 in all cases. The dissolution tank volume estimation was done based on the reagent's overall chemical reaction constant in dissolution experiments. The limestone rocks, where the prevailing mineral was calcite (CaCO3), demonstrated higher chemical reactivity yielding smaller dissolution tank volumes than the dolomite rocks, where the prevailing mineral was dolomite (CaMg(CO3)2). The CaO and MgO content of a sample can be used to predict the dissolution rate; nevertheless more factors influence the rate and the tank sizing. The knowledge of the sample's composition and its reactivity is necessary for the design of a desulfurization scrubber; the reagent used is determinant for the economy and optimal operation of such scrubbers. © 2012 American Institute of Chemical Engineers Environ Prog, 32: 663–672, 2013

On the Stability of Pulse‐Jet Regenerated‐Bag Filter Operation

AbstractProblems with the pulse‐jet bag filter operation have a direct influence on process plant operation and may result in loss of production time. Therefore, long‐term stable operation of the plant is desirable for both the manufacturers and operators. The effects of operating parameters are studied experimentally on filter operation with regeneration between the upper and lower pressure drop limits. Many combinations were identified when the filter operation derailed from stable to unstable operation on changing one of the operating parameters. Filtration velocity, pulse pressure, and the upper limit of pressure drop had the potential of creating instability. A threshold detachment overpressure existed below which the operation led to unstable conditions at a certain filtration velocity and which increased with increasing velocity.

Coping with complexity: past, present and future

In 1981, a technical report was published with the somewhat enigmatic title ‘Coping with complexity.’ Its purpose was to discuss how computers could be used to assist process plant operators in coping with complex situations during plant disturbances. Today, coping with complexity is a problem not only for process plant operators but for everyone. And while computers in 1981 were looked upon as the solution, they are now seen as the source of the problem. This paper discusses why and how the meaning of ‘coping with complexity’ has changed over the years and speculate on what may lie ahead.

An intelligent supervision system for open loop controlled processes

On-line manufacturing systems for continuous production are traditionally checked by constant time-based inspection and statistical process control processes. In the monitoring operation of large scale process plants, it is important to detect and locate process variables as they can significantly modify the operation and quality of the products involved. The present paper explores an alternative for monitoring these systems that uses the open loop control paradigm. The proposed method is defined and presented as an application for one particular industrial process--rubber die extrusion. The advantages of this method for this particular application, including its implementation throughout a multi-agent system, compatible with the HoloMAS paradigm for managing, modeling and supporting complex systems, are also discussed.

Mercury concentrations at a historically mercury-contaminated site in KwaZulu-Natal (South Africa)

A mercury (Hg) processing plant previously operating in KwaZulu-Natal Province (South Africa) discharged Hg waste into a nearby river system causing widespread contamination since the 1980s. Although the processing plant ceased operation in the 1990s, Hg contamination (due to residual Hg) remains significant. Previous studies in the area since the plant's closure have found elevated Hg concentrations in fish, and that these concentrations were as a direct consequence of widespread contamination of the Hg processing plant operations conducted between the 1980s and 1990s. This study aimed at investigating the impacts of residual Hg almost 20years after the plant's closure. Water, sediment and biota (invertebrates and fish) were collected in water resources in the vicinity of the processing plant to determine the Hg concentrations in these compartments, as a proxy for assessing the extent to which residual Hg that is reintroduced to the water column becomes bioavailable to biota. For water and sediment samples, higher total mercury (TotHg) and methylmercury (MeHg) concentrations were measured at sampling sites immediately downstream of the Hg processing plant when compared to the upstream sites, while concentrations decreased with distance from the plant. Fish MeHg concentrations measured just below the US EPA guideline for Hg in fish muscle tissue. The results show that the historically Hg-contaminated river system is a potential Hg pollution source due to the residual Hg present in sediment. Any dredging of sediment as a form of remediation in the Mngceweni River is not recommended; however, a Hg monitoring programme is recommended for assessing the bioavailability of resuspended Hg from sediment.

The effect of acrylamide-co-vinylpyrrolidinone copolymer on the depression of talc in mixed nickel mineral flotation

Copolymers of acrylamide and vinylpyrrolidinone with varying compositions have been synthesised and employed to depress talc in a model flotation system with process plant operation conditions. Adsorption isotherms indicated that the hydrophilic acrylamide homopolymer has a very low affinity for the hydrophobic talc surface, whereas vinylpyrrolidinone homopolymer strongly adsorbs onto the talc surface. Micro-flotation experiments revealed that the copolymer system can induce stronger talc depression than the homopolymer variants, with the most effective copolymer depressant having 25–30% vinylpyrrolidinone incorporation. The copolymer system is observed to have inherited the strong talc affinity of vinylpyrrolidinone polymer and the strong hydrophilic property from polyacrylamide. This combined effect facilitates the desired strong talc depression in single mineral flotation. However, this copolymer system has similar adsorption affinity on both the talc and pentlandite, hence depressing both talc and pentlandite in the mixed mineral flotation system. This research shows that a sufficient hydrophobic balance on the polymer is necessary for the adsorption and subsequent depression for talc. However, polymer with high adsorption selectivity is required to be a successful synthetic talc depressant for mixed mineral system.

Process analysis for ammonia-based CO2 capture in ironmaking industry

Abstract In this work, low concentrated ammonia solution (up to ∼10 wt.%) was used to capture from blast furnace gas (BFG), compared to exhausted gas from power plant have a high CO2 concentration(up to ∼23 vol.%). Pilot plant with processing capacity of 50 Nm3-BFG/hr was built at POSCO in late 2008. Changing the operating conditions in pilot test with the absorption and regeneration temperature, circulating flow-rate of ammonia solution between absorber and stripper, the side stream ratio of columns for removing the slipped ammonia, and then collect the data such as gas flow rates, concentration of gas. Based on the collected data, we analyze the results such as CO2 removal efficiency, purity of recovered CO2 and consumed utilities (steam, cooling water, …). Through the analysis of results, we will find the main factors affecting the operation of ammonia-based CO2 capture process and design CO2 capture plant with the capacity of 1000 Nm3-BFG/hr.

Process Operator Skill Exploration by a Data Analysis Software

AbstractExperienced process operators have a key role in ensuring a smooth and high quality operation of process plants in many fields of industry. Consequently, there is a need to identify the skills and knowhow of the operators which leads to high performance, and educate new operators of this knowledge. To this end, an analysis software for comparing the performance of operators in a mineral processing plant has been developed for the plant management. The software implements methods that have been developed earlier for data-based analysis of the performance, and automatizes and streamlines the analysis procedure. The software, which is installed at the process plant for generating the analyses, enables the plant management to monitor the performance of the operator groups at the plant. The analysis results can serve as a starting point for identifying the most efficient operating principles. In addition, an efficient manner for sharing the operating knowhow between the operators is provided. An example case study of using the software is also given.

Use of carbonate rocks for flue gas desulfurization: Reactive dissolution of limestone particles

Sedimentary rocks, such as limestone, are widely utilized in flue gas desulfurization (FGD) processes because of their ability to form sulfur compounds. The most common system adopted for FGD is the wet scrubbing process, in which the dissolution rate of sedimentary rocks represents one of the most important factors. Evaluation of the dissolution and the reactivity of solid particles involved is therefore a key factor for FGD process design and plant operation. The rate of dissolution affects the cost of makeup and waste disposal. For this reason a method to test different qualities of raw materials can give us a better understanding of the desulfurization process and reasonable economical effects. In the present work the dissolution of carbonate rocks was investigated by utilizing hydrochloric acid and the mass transport phenomena involved in batch stirred tank reactors (BSTRs) were modeled. By evaluating the ratio of convective to diffusive mass transport and the ratio of momentum and mass diffusivity, it was possible to relate the quality of raw materials in terms of a defined Time Of Exposure (TOE). The model involved takes into account the variation of the particle size distribution derived from the allocation of the scattered light energy using the Fraunhofer diffraction theory. Improvements from previous studies were done [1].

A branch and bound method for isolation of faulty variables through missing variable analysis

Fault detection and diagnosis is a critical approach to ensure safe and efficient operation of manufacturing and chemical processing plants. Although multivariate statistical process monitoring has received considerable attention, investigation into the diagnosis of the source or cause of the detected process fault has been relatively limited. This is partially due to the difficulty in isolating multiple variables, which jointly contribute to the occurrence of fault, through conventional contribution analysis. In this work, a method based on probabilistic principal component analysis is proposed for fault isolation. Furthermore, a branch and bound method is developed to handle the combinatorial nature of problem involving finding the contributing variables, which are most likely to be responsible for the occurrence of fault. The efficiency of the method proposed is shown through benchmark examples, such as Tennessee Eastman process, and randomly generated cases.

A Branch and Bound Method for Fault Isolation through Missing Variable Analysis

Fault detection and diagnosis (FDD) is a critical approach to ensure safe and efficient operation of manufacturing and chemical processing plants. Multivariate statistical process monitoring (MSPM) has received considerable attention for FDD since it does not require a mechanistic process model. The diagnosis of the source or cause of the detected process fault in MSPM largely relies on contribution analysis, which is ineffective in identifying the joint contribution of multiple variables to the occurrence of fault. In this work, a missing variable analysis approach based on probabilistic principal component analysis is proposed for fault isolation. Furthermore, a branch and bound method is developed to handle the combinatorial nature of the problem involving finding the variables, which are most likely responsible for the occurrence of fault. The efficiency of the method proposed is shown through a case study on the Tennessee Eastman process.

Construction and demolition waste processing in Athens, Greece: a pilot demonstration

Construction and Demolition Wastes (CDWs) constitute a waste fraction, which is quantitatively at least as high as municipal solid waste in Greece and other countries. This paper presents the current situation on CDW management in Greece and focuses on the results from the operation of a pilot processing plant. CDW was collected from construction crews at several demolition sites, which included: the demolition of old residential buildings damaged due to an earthquake in September 1999 in Northwest Attica; the construction of 1000 new residential buildings. The operation of the plant is described and an analysis of its operation is provided.

Creating New Landscapes and Ecosystems

Extraction of oil from the Alberta Oil Sands through surface mining involves the removal of the overburden and oil sand to a depth of up to 100 m and over extremely large areas. While the operation of the bitumen processing plants has serious environmental impacts on downstream habitats, this article focuses on the reclamation of areas from which the oil sands have been removed, processed, and returned. This reclamation following closure of the mines will entail the complete re-creation of landforms and ecosystems at a landscape scale, with the goal of producing suitable habitats for plants, animals, and people. Such projects will require a reasonable understanding of the geophysical and ecological processes that operate at a wide range of scales. Some information is provided on the climate, hydrology, vegetation, and land use (past and current) of the Oil Sands area, situated within the Boreal Plain ecozone, to provide a framework for discussion of issues to be addressed in, and proposed guidelines for, such large-scale reclamation. Although none of the mines has yet closed, numerous consultant reports have been produced with recommendations for various aspects of such reclamation projects (e.g., wetland hydrology, vegetation, wildlife habitat). The scientific basis of such reports is found to vary with respect to depth of understanding of the relevant processes.

Quality and Safety Models and Optimization as Part of Computer‐Integrated Manufacturing

This article is part of a collection entitled “Models for Safety, Quality and Competitiveness of the Food Processing Sector,” published in Comprehensive Reviews in Food Science and Food Safety. It has been peer‐reviewed and was written as a follow‐up of a pre‐IFT workshop, partially funded by the USDA NRI grant 2005‐35503‐16208.ABSTRACT: Mathematical models are the basis of modern process engineering methods. Mathematical optimization is at the kernel of systematic and efficient tools for (1) experimental design, model development, and identification, (2) development of optimal operating procedures, and (3) implementation of those procedures by means of model‐predictive controllers. Here, we review and discuss how these model‐based optimization techniques can be used at the core of computer‐integrated manufacturing systems for the food industry. These systems will be able to bring the operation of food processing plants closer to the best possible product quality and safety, at a reduced cost and with minimal environmental impact.