Safety First- SCBA Refresher

SRE’s conventional on-site SRU testing work almost always involves sour work. Whether analyzing SRU feed stream samples, which contain 98 percent H2S at several clients’ facilities in the Middle East, to lower ppm level streams downstream in the process, while the risks may not appear equal on the surface- the potentially fatal conclusion is common to each and every sour situation.

Conventional training and awareness programs teach us how to best mitigate the risks associated with H2S. Here, knowledge of wind direction and appropriate body positioning needs to be at the forefront when planning and executing sour-related work. Based on our vast experience, being on-site conducting SRU Performance Evaluations, air flow can be quite limited out in the unit. Furthermore, it seems counterintuitive, but it is important to always remember that it’s a ‘good’ thing if we can smell it! H2S impairs our ability to smell/detect as its concentration increases and, at that point, it is most likely already too late. For these reasons, at many facilities, sour work is left to SRE- the professionals.

As was highlighted in a previous SRE Newsletter, PPE is our last line of defense! It is important to ensure that proactive safety controls are also always in place. These can include: Administrative controls (safety training, worker rights, etc.); Engineering controls (signage, guard rails, etc.); and Plant-level protection (H2S detection, SCBA, etc.).

The focus for the remainder of this particular article is the importance of conducting periodic SCBA checks to serve as a personal refresher and to protect/provide learning opportunities for all stakeholders: your colleagues, site visitors, safety equipment providers, and yourself! Another thing that is guaranteed in this world- you never do know when you may be called into action. Whether doing rounds out in the plant or waiting at a traffic light, we need to ensure that we are always prepared!

About a year ago, an SRE team member was getting ready to conduct work at a Refinery in California. It really makes no difference here, but the SCBA’s were provided by an outside supplier. Upon thorough inspection, it was determined that the air line’s connection at the regulator was jeopardized. The important takeaway here is that the connection was indeed made; however, only by way of thorough inspection could one actually determine that the integrity of the connection was jeopardized. While the on-site work was delayed, having to wait for a new SCBA to be delivered, this find was truly invaluable!

For most, donning SCBA is not a routine, day-to-day activity. When was the last time that you donned SCBA? If it’s been a while, the following listing will serve as an excellent refresher and resource to ensure that this critical piece of safety equipment is truly ready to protect the lives of everyone, when called upon!

• Check all of the SCBA-related straps to ensure no fraying (mask included)

• Verify air lines and associated connections

• Check the back plate to ensure no damage

• Verify that the cylinder is properly tagged, full, has not expired, and in good condition

• Mask up, confirm seal, and take a breath off of the cylinder

• Are the cylinder and regulator pressures equal?

• Verify the regulator’s by-pass mechanism

• Confirm regulator alarm points by shutting in the cylinder and releasing the remaining air

Enhance Your Process Understanding, Evaluate Parameter Changes, and Improve Your Bottom Line With Dynamic SRU Modeling!

Process simulation is a model-based representation of a process plant such as a Sulfur Recovery Unit, in software. Basic prerequisites are a thorough knowledge of chemical and physical properties of pure components and mixtures, of reactions, and of mathematical models which, in combination, allow the calculation of a process in computers.

In general, process simulation uses models which introduce approximations and assumptions but allow the description of a property over a wide range of temperatures and pressures which might not be covered by real data, however; VMGSim™ has implemented onsite testing data of various plant configurations collected by SRE from more than 15 years of on-site process stream sample collection and analysis, which also allow interpolation and extrapolation – within certain limits – and enables the search for conditions outside the range of known properties.

Initially process simulation was used to simulate steady state processes. Steady-state models perform a mass and energy balance of a stationary process (a process in an equilibrium state) however do not depend on time. In a steady state Process simulation software, such as VMGSim™, describes processes in flow diagrams where unit operations, such as Reaction Furnace(RF), Catalytic Convertors and Condensers, are positioned and connected by material and/or energy streams. The software has to solve the mass and energy balance to find a stable operating point. The goal of a process simulation is to find optimal conditions for an examined process. This is essentially an optimization problem which has to be solved in an iterative process.

Dynamic simulation is an extension of steady-state process simulation whereby time-dependence is built into the models via derivative terms (i.e. accumulation of mass and energy). The advent of dynamic simulation means that the time-dependent description, prediction and control of real processes in real time has become possible. This includes the description of starting up and shutting down a plant, changes of conditions during a reaction, holdups, thermal changes and more. Dynamic simulations require increased calculation time and are mathematically more complex than steady state simulations. It can be seen as a steady state simulation repeated multiple times (based on a fixed time step) with constantly changing parameters.

Dynamic simulation can be used in both an online and offline fashion. The online case being model predictive control, where the real-time simulation results are used to predict the changes that would occur for a control input change, and the control parameters are optimized based on the results. Offline process simulation can be used in the design, troubleshooting and optimization of Sulfur plants as well as the conduction of case studies to assess the impacts of process modifications. Dynamic simulation is also used for operator training.

VMGSim™ Dynamics Benefits

VMGSim™ is a powerful tool which can be used for both steady state and dynamic simulations.
The following studies and troubleshooting can be performed using a high fidelity Dynamic VMG™ model.

1. Can implement or study as an off-line virtual SRU
2. Evaluate extreme upset conditions without affecting the Integrity of the process
3. Study bottlenecks like under-sized or oversized equipment and the overall effects on the SRU and sulfur recovery rates for any given scenario.
4. Turndown study under various scenarios.
5. Can perform Co firing study.
6. Blower performance and pressure drop analysis for various scenarios.
7. Duty analysis of Waste Heat boilers and Condensers.
8. Plant upset study.
9. Tuning parameters and set point study.
10. Alternative process modification such as Acid Gas vs Fuel Gas firing at Aux burners and Direct Fired heaters vs Indirect fired heater.
11. Most Effective and Efficient Controller for the Application can be determined
12. Evaluate different control strategies
13. Perform regulatory control system studies
14. Introduce a wide variety of upset conditions
15. OPC Server and Client Compatible
16. On-line Process Monitoring
17. Evaluate various operating process inputs
18. Pressure Profiling and tuning
19. Determine Pinch Points in a System
20. Max out duties of exchangers
21. Valve saturations
22. Evaluate relief loads from causes such as blower, pump, and/or power failures

SOGAT Presentation: Causes of the Latest SRU Failings

SRE’s Inshan Mohammed presented a paper at SOGAT 2017 that focused on three SRUs failing to meet expected overall recovery efficiencies due to:

Apparent first converter catalyst deactivation;

Reduced recovery efficiency due to poor Amine Unit operation; and

Lower than expected Carbonyl sulfide and Carbon disulfide hydrolysis rates for full Titania catalyst.

This paper summarizes each of these case studies by providing a description of the problem, a review of the possible causes, and recommendations for improvement. If you were unable to attend Inshan’s presentation, and want to receive a copy of the paper, please contact us.

The Benefits of Baseline SRU Evaluation

The typical lifecycle of a new unit is to go from design basis to simulations and data sheets and then from construction and commissioning to startup.  In the case of the Sulfur Recovery Unit (SRU), an additional step may be taken after startup in the Performance Guarantee of the unit where the Operating Company ensures the Licensor has designed and built a unit which meets the BoD.  Most of the time, though, Operators choose to forego the Performance Guarantee (budget, timing, incapable of meeting testing conditions, etc.).  Beyond the money-back aspect, what Operators are foregoing is the crucial sample set illustrating how the unit truly performs: an operating baseline.
Real analytical results are better than a simulated material balance.

Long after the unit is operational and just about when problems start to arise, recently SRE was brought in by an SRU Operator to determine the problems with their SRU.  As we’ve mentioned in our webinars, SRE starts any troubleshooting with analytical results of the unit’s current performance.  However, this snapshot in time is meaningless without something to which to compare it.  Once the current performance was determined and the BTEX breakthrough was obvious, we asked “has the unit always been like this?”  And that’s when the Operator will bring out the material balance in the SRU’s As Built drawings – we’re now trying to compare apples with oranges – and better yet, the simulation never took into consideration any aromatics in the whole design.

Although troubleshooting exercises can be solved without reference data, having something to compare to always helps.  Solving a problem fast means less downtime and more production.  Even better is data on a regular basis.  Trends can provide leading indicators to potential problems and to future catastrophes, saving big money down the road.

Having a baseline set of analytical results, benchmarks the performance of the SRU.  It’s an invaluable reference which will be far more accurate than the material balance provided by the Licensor.  Further, if you’re lucky, the test results will show areas for improvements or at the least, confirm that your unit is healthy.