Learning German Language – Deutsch lernen

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Do you already have some good reasons to learn German? Want to communicate with relatives, or to travel to Germany during your summer break, or to prepare yourself for study in a German-speaking country?!

Just in case you still have any doubts and need a final push toward taking the plunge, here are some more reasons why learning German may be a good choice for you. German is the most widely spoken language in Europe.

Image may contain: 1 person, standing, sky and outdoorGerman is the 3rd most popular foreign language taught worldwide and the second most popular in Europe and Japan.

Germany has the 3rd strongest economy and is the #1 export nation in the world. Which means, knowing German creates business opportunities.

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1 in 10 books in the world is published in German. In number of books published, Munich is second in the world only to New York.
German-speaking countries have a rich cultural heritage. Germany is often referred to as the land of poets and thinkers. Johann Wolfgang von Goethe, Thomas Mann, Franz Kafka, just to name a few.

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German language is not as hard as you think. If you already know English, then you already have an advantage when it comes to learning German. The two languages share many similarities in both vocabulary and grammar.

I have compiled learning videos more than 70 videos from https://www.germanwithjenny.com/

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Listening Comprehension for Beginners #1 – der Winter – A1/A2

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Listening Comprehension for Beginners #3 – der Geburtstag – A1/A2

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Start Deutsch 1 Oral Exam – Part 1 – Goethe Institute – Prep – A1

Start Deutsch 1 Oral Exam – Part 2 – Goethe Institute – Prep – A1

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Visit Budapest as Europe’s Best Destination 2019

Capital of Hungary Budapest has been just been named the the best Destination of Europe.

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Budapest voted as Europe´s Best Destination 2019

European Best Destinations – the aim of the award is to promote European tourism and culture worldwide – has been guided to world travelers for 10 years, working closely with the continent’s largest destination and tourist offices, and with the EDEN network (European Distance and E-Learning Network) set up by the European Commission to help tens of millions of tourists to choose the best destination.

No surprise it is very easy to turn this recognition into benefits, just think about the half a million voters from 153 different countries who followed the vote this year, where to book their next flight tickets.

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The best destination gets a year-round promotion of the European Best Destinations website, and in the most prestigious international travel, economic and lifestyle media outlets, numerous social media platforms and travel portals.

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Budapest first took part in the voting in 2018, and it won the 8th place, forewent many famous European cities. The Hungarian capital with 62 128 votes won European Best Destinations (EBD) in February 2019, overtook cities like London, Paris, Florence and many more breathtaking destinations. 77% of the Budapest-voters came from other countries, mainly from the UK, USA, Germany, France, Austria, and Italy. Thus, we can say that the city has earned an overwhelming victory.

Budapest, 13-24 April 2019

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Training Simulators for Offshore Oil and Gas Facilities

Nearly 50% of oilfield production workers in the Gulf of Mexico will retire in the next 10 years.  As energy companies struggle to replace an aging operator workforce, Operator Training Simulators (OTS) have become a key component of these efforts. The primary goal of companies which are replacing these workers is to retain the knowledge of experienced operations personnel, and to pass it on through the use of virtual simulation and other integrated training processes in order to develop a well-trained and competent workforce.

The lack of experienced personnel, potential for environmental consequences, regulatory requirements and litigation risks imposed by improper facilities operation have made operator training simulations a best practice for the startup and operation of any new oil and gas facility.

Training simulators used for oil and gas facilities operations training may be physical or virtual in nature. Physical simulators require multiple servers, each programmed for a specific application within the training simulations integration. Virtual training simulators are composed of only a few actual physical servers while the balance of components are simply emulations of servers and server processes.

A primary advantage of virtual servers is that upon failure of the emulated server, the program can be reloaded to the system while the failure of a physical server requires replacement of the server component.

Training simulators may be integrated systems that include the modeling of most facility operating processes-such as topsides, subsea and marine operations. Integrated OTS machines provide the most realistic simulations currently used for facility operations training. With an integrated OTS all facility simulation training processes are available on a single machine.

Operator training simulators are loosely described in two main groups, either low or high fidelity. 

Low fidelity simulators are simulators that do not mimic the actual design and function of an integrated production control system. The simulations also may not model the state of the physical processes that will be performed. Low fidelity simulators:

  • Cannot be used for automation testing, procedure validations or design verification processes.
  • May not include an emulation of the actual control systems used by the oil and gas facility personnel being trained.

Low fidelity simulators are used primarily by oil and gas operations for situational awareness training and to provide trainees with a basic understanding of the process work flows of generic oil and gas operations. Low fidelity training simulators should not be used as the basis for the competency assessment of control room operator trainees-particularly if the control system has not been accurately mimicked.

On the other hand, high fidelity simulators attempt at varying degrees of complexity-to model all of the interactions contained within a complex integrated control system. Modeling processes may include the actual functions of the process equipment and their interfaces, as well as emulations of the physical flow modeling and flow assurance complexities.

Dedicated physical or virtual servers are provided for each aspect of the control dynamics inclusive of:

  • Operating system software such as Siemens, Yokogawa and Honeywell distributed control systems (DCS) (or Wonderware PLC based systems)
  • Control software and equipment emulations for pump, compressor and generator controllers, valves and process controllers
  • Safety and shutdown systems emulations (i.e.: MCS, PSS, SSI, SPS and other systems)
  • Topsides flow modeling
  • Subsea flow modeling -if applicable
  • Marine processes modeling-for active ballast control systems
  • Network interfaces and communications such as OPC, optical, TCP/IP and hardwire emulations

High fidelity simulators are best built after the cause and effect and operating procedures for an oil and gas facility have been developed but well enough in advance of the startup of the facility to allow for an effective operator training program to be completed. The advantages of building a high fidelity operator training simulator include:

  • The possibility of design criteria and cause and effect verifications
  • Validation of operating, startup and intervention procedures (topsides and subsea)
  • Training of engineering staff, and training and competency assessment of operations personnel
  • Automation controls troubleshooting process, control revisions testing and debottlenecking
  • Reduced downtime during startup and turnaround operations because of more detailed shutdown and startup processes.

The disadvantages include greater development costs, additional upfront planning and testing requirements and the costs associated with maintaining and updating the OTS for ongoing brownfield modifications.

Once a company decides and contracts to build a training simulator, the OTS builder will work with the customer to define the project scope. The builder will likely request project documentation packets to include:

  • Design specs and lists of equipment, choke curves and etc.
  • P&ID’s and/or PFD’s for the project
  • Cause and effects documentation, equipment control narratives and integrated control systems specifications and narratives
  • Flow assurance and flow guidance documents
  • Any available flowback performance documentation
  • Operating procedures (once developed)

The physical and virtual servers are built, packaged and programmed per the facility specs. The topsides and subsea models are developed to mimic the physical characteristics of the process flow and the flow assurance guidance. The Model Acceptance Test (MAT) is performed for acceptance of the topsides, subsea and/or marine models.

Once the MAT test(s) is accepted by the customer, final integration and calibration of the high fidelity simulator package and model is performed.

A Factory Acceptance Test (FAT) of the integrated simulator is then scheduled and performed with the customer. This FAT is actually the first time a new build operator training simulator is operated as an integrated package.

Operations personnel or customer contractors should perform additional testing and fine tuning after FAT acceptance-in association with the builders programming specialists-to ensure that the training simulator performs according to modeled expectations and realistically represents the operations being simulated.  The simulator may also be linked to the customer’s PI System-(data historian) to further tune and initialize the integrated operations model(s). After the OTS performance is deemed satisfactory, the customer will then decide how best to use the training simulator.

An Exercise Training Manager software package allows for competency testing process records that are not affected by the independent competency review provided by the OTS trainer.

Once the simulator has been properly configured and calibrated and sufficient design criteria, cause and effects documents and flowback data have been provided by the customer, the following data can be obtained through testing:

  • Verification of the equipment design and validation of the cause and effects
  • Validation of startup, operations and intervention procedures
  • Operating characteristics of the facility inclusive of hydrate formation, choke performance slugging issues, well productivity and flow characteristics at min through max flowrates
  • Unusual or unexpected conditions which may create startup issues
  • Initial competencies of the control room operators who will operate the facility via built in Exercise Manager tools and instructor provided operator competency assessments.

The future for operator training simulations is exciting. In addition to virtual servers, expect the rise of more enterprise simulators which bundle all of a company’s facility training simulators into a single OTS package. Expect magnitudes of higher fidelity simulations development that will likely change the use of training simulators into more of an engineering and asset development tool. Finally, the growth of remote login features allows trainer and trainee access to the OTS from any location where sufficient bandwidth and a remote plugin is available.

Source : https://www.linkedin.com/pulse/training-simulators-offshore-oil-gas-facilities-richard-raffield/

 

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Processing of Heavy Crudes – Challenges and Opportunities to the Downstream Industry

The continuous supply of adequate crude oil to the refining hardware is one of the assumptions adopted by the refiners to the installation of refining assets or economic analysis of already installed units. However, according to the installed geopolitical scenario, the supply of adequate crude oil to the refining hardware can be seriously threatened, mainly to refiners that operate with lighter and high-cost crudes.

In this sense, more flexible refining hardware in relation of the processed crude slate is an important competitive advantage in the downstream sector, mainly the processing of heavy and extra-heavy crudes due to his lower acquisition cost when compared with the lighter crude oils. The difference in the acquisition cost between these oils is based on in the yield of high added value streams which these oils present in the distillation process, once the lighter crudes normally show higher yields of distillates than the heavier crudes, his market value tends to be higher.

The processing of heavy crudes shows some technologic challenges to refiners once, due to his lower yield in distillates, it’s necessary the installation of deep conversion technologies aiming to produce added value streams that meet the current quality and environmental requirements, furthermore the concentration of contaminants like metals, nitrogen, sulfur, and residual carbon tends to be high in the heavier crudes, making the processing of his intermediate streams even more challenger.

The challenge in the processing of heavy crude oil starts in the desalting step before the sent to the distillation unit. The desalting process consists basically in the water addition to the crude aiming to promote the salt removal from the oil phase that tends to concentrate in the water phase, Figure 1 presents a simplified process flow diagram for a crude oil desalting process with two separation stages.

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Figure 1 – Crude Oil Desalting Process with two Separation Stages

The separation of oil and water phases in the separation drums occurs through the sedimentation process, due to the density gap between the water and the crude oil. Considering that the sedimentation process can be theoretically described by the Stokes Law, according to equation 1.

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According to equation 1, the sedimentation velocity is proportional the density gap, in the case of heavier crudes, this gap is lower leading to a lower sedimentation velocity and the need of higher residence times to an adequate separation. Another complicating factor in the case of heavy crudes is the higher viscosity of the oil phase that hinders the mass transfer in this phase. Due to these factors, refining hardware designed to process heavy crude oils needs more robust desalting sections taking account the trend of higher salt concentration in the crude and a harder separation process. Table 1 presents an example of crude oil classification based on the API Grade.

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After the desalting process, the crude oil is sent to the atmospheric distillation tower, according to presented in Figure 2.

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Figure 2 – Atmospheric Distillation Process of Crude Oil

To heavier crudes, the yield of distillates by simple distillation is relatively reduced and the bottom section in the atmospheric distillation units tends to be overload. Table 2 presents a comparative analysis of the yields of different crude oils.

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Where, VGO = Vacuum Gas Oil

Normally, heavy crude oils have a higher concentration of metals, sulfur, and nitrogen. These contaminants tend to be distributed in the intermediates streams concentrating in the heavier streams, making necessary more robust conversion processes and tolerant to these contaminants.

Aiming to avoid damage to the catalysts of deep conversion processes as FCC and hydrocracking, normally refineries that process heavier crudes promotes a better fractionating of bottom streams of the vacuum distillation tower. When the crude oil presents high metals content, it’s possible to include a withdraw of fraction heavier than the heavy gasoil called residual gasoil or slop cut, this additional cut concentrates the metals in this stream and reduce the residual carbon in the heavy gasoil, minimizing the deactivation process of the conversion processes catalysts as aforementioned. Normally, the residual gasoil is applied as the diluent to produce asphalt or fuel oil.

Due to the high asphaltenes content in the heavier crudes, the residual carbon in the bottom barrel streams is also higher than observed in the lighter crudes, this characteristic reinforces, even more, the necessity of installation process units with high conversion capacity.

Available technologies to processing bottom barrel streams involve processes that aim to raise the H/C relation in the molecule, either through reducing the carbon quantity (processes based on carbon rejection) or through hydrogen addition. Technologies that involves hydrogen addition encompass hydrotreating and hydrocracking processes while technologies based on carbon rejection refers to thermal cracking processes like Visbreaking, Delayed Coking and Fluid Coking, catalytic cracking processes like Fluid Catalytic Cracking (FCC) and physical separation processes like Solvent Deasphalting units.

Due to the high content of contaminants in the crude oil and consequently in the intermediary chains, refining equipment destined to the processing of heavy crudes requires high hydrotreatment capacity. Usually, the feed streams of deep conversion units like FCC and hydrocracking go through hydrotreatment processes aiming to reduce the sulfur and nitrogen contents as well as the content of metals. Higher metals and asphaltenes content lead to a quick deactivation of the catalysts through high coke deposition rate, catalytic matrix degradation by metals like nickel and vanadium or even by the plugging of catalyst pores produced by the adsorption of metals and high molecular weight molecules in the catalyst surface. By this reason, according to the content of asphaltenes and metals in the feed stream are adopted more versatile technologies aiming to ensure an adequate operational campaign and an effective treatment.

Figure 3 presents a scheme of reactants and products flows involved in a heterogeneous catalytic reaction as carried out in the hydroprocessing treatments.

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Figure 3 – Reactants and Products Flows in a Generic Porous Catalyst (GONZALEZ, 2003)

In order to carry out the hydroprocessing reactions, it’s necessary the mass transfer of reactants to the catalyst pores, adsorption on the active sites to posterior chemical reactions and desorption. In the case of bottom barrel streams processing, the high molecular weight and high contaminants content require a higher catalyst porosity aiming to allow the access of these reactants to the active sites allowing the reactions of hydrodemetallization, hydrodesulfurization, hydrodenitrogenation, etc. Furthermore, part of the feed stream can be in the liquid phase, creating additional difficulties to the mass transfer due to the lower diffusivity. To minimize the plugging effect, in fixed bed reactors, the first beds are filled with higher porosity solids without catalytic activity and act as filters to the solids present in the feed stream protecting the most active catalyst from the deactivation (guard beds).

Due to the higher severity and robustness of the processes, the installation cost of the refining hardware capable to process heavier crudes tends to be higher when compared with the light and medium oils as well as the operating costs. Figure 4 shows a possible refining configuration to be adopted by refiners to add value to heavy crudes.

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Figure 4 – Process Arrangement to a Refinery Operating Under Coking/Hydrocracking Configuration

The refining scheme presented in Figure 4, normally called Coking/Hydrocracking configuration, is capable of ensuring high conversion capacity, even with extra-heavy crudes. The presence of hydrocracking units gives great flexibility to the refiner, raising the yield of middle distillates. Figure 5 presents a basic process flow diagram for a typical hydrocracking unit designed to process bottom barrel streams.

This configuration is adopted when the contaminants content (especially nitrogen) is high, in this case, the catalyst deactivation is minimized through the reduction of NH3 and H2S concentration in the reactors. Among the main hydrocracking process technologies available commercially we can quote the process H-Oil™ developed by Axens Company, the EST™ process by ENI Company, the Uniflex™ Processes by UOP, and the LC-Fining™ technology by Chevron Company.

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Figure 5 – Typical Hydrocracking Unit Dedicated to Treat Bottom Barrel Streams

Although the higher processing cost, to process heavy crudes can present high refining margin. As described earlier, the reduced acquisition cost in relation of lighter crudes, as well as the ease of access and reliability of supply, can make the heavy crudes economically attractive, mainly in countries like Canada, Venezuela, and Mexico that have great reserves of heavy and extra-heavy crude oils.

The flexibility of the refining hardware is a fundamental factor to ensure the competitiveness of the refiner in the refining market. Normally, the refineries are designed to process a range of crudes, and wider the range, according to the technical limitations, more flexible is the refinery related the processed crude slate, this characteristic is relevant and strategic taking into account the possibility to enjoy the processing of low-cost crude oils by opportunity besides giving more resilience to refiner in scenarios of restricting access to the petroleum market, mainly face geopolitical crisis.

The current scenario of the downstream industry indicates the tendency of reduction in the transportation fuels demand and the raising in the demand by petrochemical intermediates creating the necessity of growing the conversion capacity by the refiners in the sense of raising the yield of light olefins in the refining hardware. Furthermore, the new regulation over the marine fuel oil (Bunker), IMO 2020, should create even more pressure over the refiners with reduced conversion capacity.

In a first moment, aiming to comply with the new bunker specification, noblest streams, normally directed to middle distillates should be applied to produce fuel oil with low sulfur content what should lead to a shortage of intermediate streams to produce these derivatives, raising the prices of these commodities. The market of high sulfur content fuel oil should strongly be reduced, due to the higher prices gap when compared with diesel, his production will be economically unattractive, leading refiners with low conversion capacity to opt to carry out larger capital investment in order to give their refining hardware more robustness for the processing of heavier crudes.

The market value of the crude oil with higher sulfur content, normally the heavier crudes, tends to reduce after 2020. In this case, refiners with refining hardware capable to add value to these crudes can have a great competitive advantage in relation of the other refiners taking into account the lower acquisition cost of the crude oil and higher market value of the derivatives, raising then the refining margins.

As briefly described, heavy crude processing offers technological challenges to refiners, however, according to the geopolitical and the downstream industry scenarios, processing heavier oils can be a competitive advantage. The current scenario of the refining industry indicates a strong tendency to add value through the production of lighter products, mainly petrochemical intermediates. This fact, coupled with the need to produce bottom streams with lower contaminants after 2020 (IMO 2020), increases even more the pressure on refineries with low bottom barrel conversion capacity under risk of loss of competitiveness in the market, in this scenario it is possible to have a strong tendency of resumption in the capital investments in the preparation of these refiners to the processing of petroleum residues and heavier crudes.

References:

SPEIGHT, J.G. Heavy and Extra-Heavy Oil Upgrading Technologies. 1st ed. Elsevier Press, 2013.

ROBINSON, P.R.; HSU, C.S. Handbook of Petroleum Technology. 1st ed. Springer, 2017.

GONZALEZ, G. S. Junior Engineer’s Training Course – Kinetics and Reactors. Oxiteno Company, 2003.

GARY, J. H.; HANDWERK, G. E. Petroleum Refining – Technology and Economics.4th ed. Marcel Dekker., 2001.

Source : https://www.linkedin.com/pulse/processing-heavy-crudes-challenges-opportunities-da-silva-mba/

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Improving the Yield of High-Added Value Derivatives – Crude Oil Vacuum Distillation

Written by Dr. Marcio Wagner da Silva, MBA, Process Engineer and Project Manager at Petrobras.   Source : https://www.linkedin.com/pulse/improving-yield-high-added-value-derivatives-crude-da-silva-mba/.

To achieve the condition of marketable products and useful to the society, the crude oil needs to pass by processing steps aiming to add value through separation and conversion processes. The entrance gate of the crude oil in a refinery is the crude oil distillation unit that aims to separate the crude into process streams which, after adequate treatment, will be commercialized like derivatives as transportation fuels, petrochemical intermediates, etc. Figure 1 presents a scheme of a typical atmospheric crude oil distillation unit.

Figure 1 – Typical Atmospheric Crude Oil Distillation Unit

The bottom stream of the atmospheric column (Atmospheric Residue) still contains recoverable products capable to be converted into high added value derivatives, however, under the process conditions of the atmospheric unit, the additional heating lead to thermal cracking and coke deposition.

Aiming to minimize this effect, the atmospheric residue is pumped to the vacuum distillation column where the pressure reduction leads to a reduction in the boiling point of the heavy fractions allowing the recovery while minimizing the thermal cracking process. Figure 2 shows a typical process arrangement for a vacuum crude oil distillation unit dedicated to producing intermediates streams to transportation fuels.

Figure 2 – Vacuum Crude Oil Distillation to Transportation Fuels Production

The heavy and light gasoil streams are normally directed to conversion units like hydrocracking or fluid catalytic cracking (FCC), according to the adopted refining scheme. The fractionating quality achieved in the crude oil vacuum distillation column has a direct impact upon the reliability and conversion units operation lifecycle, once which in this step is controlled the metals content and the residual carbon (CCR) concentration in the feedstock to these processes, high values of these parameters lead to a quickly catalyst deactivation raising operational costs and reducing profitability.

The vacuum generated in the column can be humid, semi-humid and dry. Humid vacuum occurs when is applied steam injection in the fired heater and in the column aiming to reduce the partial pressure of the hydrocarbons improving the recovery while in the semi-humid vacuum the steam is injected only in the fired heater minimizing the residence time reducing the coke deposition. The dry vacuum does not involve the steam injection, in this case, is possible to achieve pressures between 20 to 8 mmHg while in the humid vacuum the column operates under pressures varying between 40 to 80 mmHg, however, it’s possible to achieve comparable yields through the injection of stripping steam. Figure 3 presents a process arrangement for a typical vacuum generation system in a vacuum crude oil distillation unit.

Figure 3 – Process Arrangement for a Typical Vacuum Generation System for a Vacuum Crude Oil Distillation

Some refiners include additional side withdraws in the vacuum distillation column. When the objective is to maximize the diesel production, it’s possible to add a withdraw of a stream lighter than light vacuum gasoil that can be directly added to the diesel pool or after hydrotreating, according to the sulfur content in the processed crude oil. When the crude oil presents high metals content, it’s possible to include a withdraw of fraction heavier than the heavy gasoil called residual gasoil or slop cut, this additional cut concentrates the metals in this stream and reduce the residual carbon in the heavy gasoil, minimizing the deactivation process of the conversion processes catalysts as aforementioned. Normally, the residual gasoil is applied as the diluent to produce asphalt or fuel oil.

When the refinery is focused to produce lubricants, the vacuum column has better fractionating quality while in the column dedicated to producing fuels the internals are designed mainly to promote the heat exchange between the streams. The better fractionation in the case of lubricants is due to the necessity to produce the lubricants cuts, as presented in Figure 4.

Figure 4 – Process Arrangement for a Vacuum Column to Produce Lubricants

Vacuum residue is normally directed to the asphalt production or, in refineries with higher conversion capacity, to bottom barrel conversion units like delayed coking and solvent deasphalting aiming to improve the yield of high added value derivatives.

According to the refining scheme, the installation of vacuum distillation units can be dispensed. Refiners that rely on residue fluid catalytic cracking units (RFCC) can sent the atmospheric residue directly to feed stream of these units, however, it’s necessary to control the contaminants content (metals, sulfur, nitrogen, etc.) and residual carbon (CCR) aiming to protect the catalyst, this fact restricts the crude oil slate that can be processed, reducing the refiner operational flexibility. On the other hand, in refineries that process extra heavy crudes, normally the crude oil distillation unit is restricted to the vacuum unit once the yields of the atmospheric column would be very low and the coking risk very high.

The processing of residual streams and the residue upgrading have key role to the economical performance of the downstream industry and this protagonism trends to grow after 2020 due to the start of IMO 2020 that establishes the reduction of the sulfur content in the bunker (Marine Fuel Oil) from the current 3,5 % (m.m) to 0,5 % (m.m), this regulation should restrict the use of high contaminants content streams as diluents to the production of fuel oils like adopted nowadays, this fact would lead to apply high added value streams (diesel, as example) as diluent which can pressure the refiners profitability, in this scenario refineries with higher complexity should have competitive advantage over the competitors. This fact can lead these refiners to carry out capital investments aiming to improve his bottom barrel conversion capacity.

References:

SPEIGHT, J.G. Heavy and Extra-Heavy Oil Upgrading Technologies. 1st ed. Elsevier Press, 2013.

ROBINSON, P.R.; HSU, C.S. Handbook of Petroleum Technology. 1st ed. Springer, 2017.

GARY, J. H.; HANDWERK, G. E. Petroleum Refining – Technology and Economics.4th ed. Marcel Dekker., 2001.

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Basic Control Loops Performance Monitoring

Advanced control strategies are often organized hierarchically, with multi variable controllers that provide the set-points to low-level controllers, which are typically of the proportional-integral-derivative (PID) type. Thus, it has to be recognized that the overall process performance relies in any case on the performance of the PID controllers. In fact, despite the presence of many effective automatic tuning methodologies based on identification methods suitable for being applied in industry, in many practical cases, PID controllers are poorly tuned, because of the lack of time/operator skill or because of operating conditions changes. Obviously, especially in large plants where there are hundreds of control loops, it is important to have techniques able to automatically assess the performance of a PID controller and, in case it is not satisfactory, to retune the controller in order to optimize the performance. Some features are particularly appreciated in this context:

  • Employment of routine operation data, so that no special (possibly time and energy consuming) experiments are needed
  • Demanding low computational effort, so that it can be applied to hundreds control loops without significantly affecting the controllers CPU/memory (no complex identification methods requiring large array/matrix operations)
  • Capability to address both setpoint following (r(t), in figure 1) and load disturbance rejection(d(t) in figure 1)
  • Robustness to the measurement noise, typical in the industrial applications
Figure 1. Single loop controlFIGURE 1. SINGLE LOOP CONTROL

Methodology

Simplified first order or integrating plus dead-time (FOPDT, IPDT) models are representative of 90% of the dynamics in the process industry; furthermore, it can represent a reasonable approximation for higher order dynamics thanks to the well-known so-called “half rule”, according to which the largest neglected (denominator) time constant is distributed evenly to the effective dead time and the smallest retained time constant.

The model parameters (gain, lag, dead-time) can be estimated in many ways, typically already implemented in some function blocks available in the DCS libraries. Alternatively, when it’s worth saving the CPU memory and computation load, one single function block can be created for estimating the parameters of any PID Tagname of which is supplied as an input to it. An example of such kind of function block is reported in the next section, based on the theory presented in the reference paper.

For such a simplified FOPDT model the integral of the absolute error (or deviation, i.e. the difference between the process variable and the reference signal) at the end of the transient time after a setpoint step change can be analytically obtained as IAE=As (θ+λ), where As is the setpoint step amplitude, θ the process dead time and λ the desired time constant of the closed loop response, which is reasonable to be expected not lower than θ. Therefore the performance of the setpoint following task can be evaluated by the index SFPI indicated in Table 1.

With regards to the load disturbance rejection the target IAE has to be set as the one achievable through a tuning rule specifically designed for this task. In the referenced papers it is shown how such a worth choice leads to the performance index LRPIindicated in Table 2.

Industrial Application

The proposed algorithm has been applied to the temperature control loop shown in Figure 2 as TIC3206. The plant is dedicated to the production of energy from renewable sources, in particular by using palm oil as a fuel. The control task consists of keeping the palm oil pipes at the required (warm) temperature to avoid its solidification, which would cause serious damage to the plant. During routine operations, the system has to keep the steady-state value, but during the start-up phase, the controller must follow a set-point step signal effectively.  One function block has been developed for performing the process parameters estimation on the PID Tag-name that is passed to it as input variable. The core of the computation is expressed by the following code:

Yokogawa Loop Tuning & Performance Monitoring

It is worth underlining that the model parameters have been obtained making use of integral variables, which can be incrementally computed (no arrays in the memory) and are inherently robust to measurement noise.

The controller was initially tuned with a proportional band PB = 70% (note that the proportional band is equal to 100/Kp) and an integral time constant equal to Ti = 70 (s) (Td = 0). After the application of the step signal to the set-point, the process parameters have been determined as delay = 94 (s), gain = 0.285 and 184.3 s as the sum of lags and delay. The corresponding values of SFPI has been determined as 0.545, indicating the need for a retuning. After retuning, the new values of the PID controller have been determined as PB = 82.78%, Ti = 64.82 (s) and Td = 24.45 (s), with a corresponding value of SFPI = 0.973. The set-point step responses before and after the retuning procedure are shown in Figure 3, where a clear improvement in the performance appears (note the different time range in the two figures). In particular, the settling time has been considerably reduced, which is obviously appreciated in the start-up phase.

Figure 2. Overview of part of the renewable energy plant used for experimental results.

FIGURE 2. OVERVIEW OF PART OF THE RENEWABLE ENERGY PLANT USED FOR EXPERIMENTAL RESULTS.

Figure 3. Set-point step responses in the temperature control loop. Left: initial; right: retuned.

FIGURE 3. SET-POINT STEP RESPONSES IN THE TEMPERATURE CONTROL LOOP. LEFT: INITIAL; RIGHT: RETUNED.

Conclusions

Methodologies for the deterministic performance assessment and retuning of PID controllers have been reviewed and presented in a unified way in this paper. The basic idea, developed for different contexts, is to exploit the final value theorem to estimate the process parameters based on the integral of appropriate signals that results from a set-point or a load disturbance step response. This makes the technique suitable for implementing in industry, as it uses routine operating data, and is inherently robust to measurement noise and the result is almost independent of the tuning of the initial controller (on the contrary, standard least squares techniques assume an input signal that significantly excites the dynamics of the system to be estimated). The methodologies analyzed can be implemented with standard Distributed Control Systems software and can also be extended to more complex control techniques, like cascade control, dead time compensators and feedforward control.

Despite the enhanced multivariable control available algorithms, which computation complexity typically needs to be implemented at upper level, PID control is still the primary component of any basic loop and through clever PID-based architectures many “DCS-enabled” solutions can be built up and standardized in the industry. Therefore PID control will still be used for long time; its knowledge will still be a key for any control/process engineer, and any contribution for improving the effectiveness of PID control will always be welcome both in research and in the industry.

Source : Yokogawa’s Blog

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Simulation Solutions Inc, Simulators

Since 1980, Simulation Solutions and its predecessor, Atlantic Simulation, pioneered the field of microcomputer process training simulators by using low cost, readily available computer hardware. Since then, the power and speed of these low cost machines have substantially increased, allowing us to exploit the tremendous capabilities of today’s technology.

From the beginning, their focus has centered around cost effective simulator packages utilizing a wide range of available Standard Process Models and Emulated Distributed Control System (DCS) operator training stations.  Low cost hardware solutions coupled with readily available Standard Process Models permits clients to implement simulator technology in the face of budget constraints. Today, advanced programming methods allow Simulation Solutions to stress model fidelity and control system realism that others find difficult to duplicate.

In 2001, Simulation Solutions created a major breakthrough in simulator training technology. Our new Hands On Training System contains a broad range of high fidelity process models and realistic DCS system emulations which have been integrated into a network based, fully automated training system that includes detailed training exercises, comprehensive on-line help, self and graded evaluations, and the recording of test scores and results.

Clients using this newly developed technology are able to deliver hands on training on shift and around the clock. Automated system frees up available simulator Instructors for more coaching and advising, and/or allows for complete self-paced, self-study and practice. Immediately after taking a classroom or network based course on theory, operators can see this theory put into action through the use of dynamic and realistic simulator training exercises.

Operator Training Simulators

Simulation Solutions offers a wide variety of Process Simulators which include both a DCS component and a Virtual Reality Outside Operator. This Outside Operator is fully integrated with the DCS side of the Simulator. Trainees will explore the Virtual Reality Outside Operator and be able to operate all pieces of equipment that are represented on the DCS. Actions performed in the Outside Operator (Opening of Valves, Pumps, Controllers) are reflected in real time on the DCS schematics, and vice versa.

Some of their most popular Modules as below :

Flash Drum

Often utilized as a “warm-up” for our Distillation Simulator, a Flash Drum separates a binary feed made up of butane and hexane. The Feed is under flow control and the temperature is controlled with a hot oil exchanger. The temperature controller and overhead pressure controller determine the compositions of the overhead and bottoms streams. A mass balance of the two components is displayed in mass per time units to allow trainees to develop a clear understanding of mass balance. A Virtual Reality Outside Operator accompanies the program.

Pump & Valve

Water enters a series of tanks in a unit that features feed, level and pressure controllers. Specifically, the pressure on each tank is controlled using a split-range controller utilizing a nitrogen blanket, and vent valve. The first tank in the system features a level controller managing feed entering the tank, while the second tank in the system has a level controller managing feed out of the tank. A series of pumps can be swung during exercises. A Virtual Reality Outside Operator accompanies the program.

You can check link detail for More Featured Demonstration Videos

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