ExxonMobil Refinery Explosion in Torrance CA 2015

Subtitle:  Increased Fines For Violations Is A Better Solution

The basic facts:  the 155,000 BPD oil refinery owned by ExxonMobil and located in Torrance, California (suburb of Los Angeles) had a large but non-fatal explosion in February, 2015 when hydrocarbon vapors that had flowed into an electrostatic precipitator system ignited and exploded.  Four workers were injured.   The refinery has been operating at reduced-capacity ever since, with the fluid catalytic cracker (FCC) unit shut down until adequate repairs are made and government regulatory agencies are satisfied that the refinery can operate safely again. 

Just two days ago (13 January, 2015), a public meeting was held in Torrance at which the Chemical Safety Board presented its findings on the explosion.  A newspaper account of that meeting can be read here (see link). 

As a former practicing, and consulting refinery process engineer for many years, and much experience in dozens of similar refineries world-wide, I take keyboard under fingers here to offer some insights.   First, a word of my background and qualifications that I have never before shared in public. 

Many years ago, in approximately 1994 or '95, 1990 (verified) the People's Republic of China's national oil company, refining division, surveyed and analyzed all of the country's refineries to determine what could be done to modernize, improve, and make the refineries more efficient.   First, the effort was internal, using the best Chinese engineers and professors.   Following that effort, the Chinese government wanted an outside expert opinion on the matter.   They solicited bids for the work from consultants around the world, including (as I recall) from Japan, the UK, the US, and other nations.  Within the US, the little consulting company where I worked (20 engineers), received an invitation to bid.  To make a long story short, my company won the award and my boss and I were soon on a plane to Beijing for a three-week consulting trip. 

We had (and still have, in my case  (note: sadly, Dick Moriarty passed away)  ) extensive knowledge of oil refineries, and had performed many such operating and profit improvement studies on refineries world-wide.  We looked at refineries from start to finish, crude storage and distillation, to products blending and all off-sites units.   What we did not know was that the Chinese national television station brought a full crew with cameras, lights, and microphones to record our introductions on our first morning of the Chinese refinery improvement consulting project.   The head Chinese dignitary made a speech on camera, and a few others made speeches, then a translator told my boss that he was next.   Just before my boss spoke, the last speaker spoke Chinese first, then English for our benefit. He described the process just above of the Chinese effort to improve their refineries and their need for an outside opinion.   He ended by saying, "And now our distinguished foreign consultants will make their comments."   (I will never forget that phrase, Distinguished Foreign Consultants.)

My boss looked at me, and said to the camera something very short, thanked our hosts for selecting us, and ended by saying, "and now my associate Roger Sowell will describe the approach we take in our refinery profit improvement studies."   I was caught with no time to prepare, or think of what to say.   The lights were bright, the microphone was now in front of me, and the camera lens was aimed right at me. 

Richard "Dick" Moriarty and Roger Sowell
with Chinese refinery management
at Yanshan Refinery
Beijing, People's Republic of China, 1990

So, I echoed my boss' sentiments on how happy I was to be in China, for our company to be selected after a world-wide bidding process, and delighted to have the opportunity to work with the wonderful Chinese engineers and managers to study their petroleum refineries.   I described briefly the process we used, first to go over each process unit with the management to gain an understanding, then take the operating data back to the States for analysis using our proprietary computer software and our engineering experience.   

I seldom relate this story of the Chinese refinery consulting at Yanshan Petrochemical Corporation near Beijing. My point in relating this now is that I have the background to offer a considered opinion on events such as refinery explosions like the one at Torrance in February 2015.   (The Chinese company was not the only major international oil company that hired us, as we also consulted for PetroCanada, AGIP in Italy, Total in France, and many others).  

There are calls presently in California to tighten the regulatory scheme on safety in oil refineries.   As can be seen on the Chemical Safety Board's web pages, the CSB is comparing the Torrance refinery explosion to the earlier Chevron refinery fire and explosion in Richmond, California.   There is a concerted effort to have oil refineries redesigned and built in what is referred to as an inherently safe manner, or to use "inherently safer design."   One example of inherently safer design is to use non-corrodible materials of construction so that piping and vessel wall thickness does not decrease over time, leading to a rupture, leak, fire, or explosion.  Another example is to provide safety interlocks so that a fluid cannot flow because a valve cannot be opened when it is unsafe.    There is a great body of literature on inherently safer design.    It should be noted, and I make this point in my speeches on the matter, that requiring non-corrodible materials is extremely costly, as for example using titanium for all wetted piping and vessels instead of carbon steel or stainless steel.  

What occurred in Torrance at the refinery was a combination of bad human judgement and equipment failure.   Essentially, the FCC has three sections, a reactor section, a main column, and a vapor recovery unit.   The reactor section itself has two sections, the reactor and regenerator.  All of these are connected by various pipes.  In normal operation, feed oil enters the reactor, contacts catalyst and reacts, the products are separated from the spent catalyst, and the products flow into the main column for separation into various streams.  Vapor products from the main column are routed to the vapor recovery unit, where valuable products are separated from light gases.  The light gases are generally burned in the refinery as fuel. Spent catalyst from the reactor is sent to the regenerator, where the catalyst is contacted with hot air that burns carbon off of the catalyst.  The regenerated catalyst is recycled back to the reactor.  Combustion gases from the regenerator are sent to a power recovery turbine and from there to an air pollution control system, the electrostatic precipitator that exploded in Torrance.   This description is necessarily simplified, as there are many more items of equipment in an FCC unit.  

I worked in and with dozens of FCC units in my operating and consulting career.   They are fascinating units with many challenges and great opportunities for profit.  

The problem in Torrance occurred when part of the FCC unit was shut down for repairs, the reactor section.  However, and this is crucial, the main column was not shut down.   It is always required that flammable hydrocarbons be kept away from any work area, and the ExxonMobil team tried to do that.  They closed the correct valves, and injected steam into the reactor to form a barrier or seal against the hydrocarbons in the main column.   However, according to the CSB report released on 14 January 2016, (yesterday as this is written), steam leaked out of the power recovery turbine, or expander as it is also known, into the work area.  This interfered with the workers and may have been unsafe in itself, since a cloud of steam in a refinery obscures visibility and may make it difficult to breathe.   The steam rate was reduced so the workers could perform their tasks.  see link to CSB report. 

Meanwhile, and unknown to the personnel, a critical valve leaked and allowed hydrocarbon vapors to pass from the main column, through the reactor, pass the leaking valve (spent catalyst slide valve), through the regenerator and power recovery system and into the electrostatic precipitator.   A spark ignited the vapors, and an explosion resulted.    All of this is explained in great detail in the CSB report. 

For further context, there are more than 100 FCC units in the US today, with many more world-wide.  Almost every modern refinery has an electrostatic precipitator to meet the stringent air pollution requirements.   These FCC units operate approximately 3 years before being shut down for planned maintenance.   There are of course many other unplanned shutdowns, also.   But, using just 100 FCC units, and 3 years between shutdowns, there are approximately 33 units shut down each year, or roughly 3 every month.  Yet, there are very few explosions that result from these shutdowns, and subsequent startups.   One could argue that most planned shutdowns do not leave the main column full of hydrocarbons, so there is no need to insert a steam blanket to keep the hydrocarbons away from the workers.  Yet, there have been other occasions during which the procedure was performed with no harm or damage.   Clearly, then, the procedures are acceptable but something was different in this case.  

It appears, based on the CSB description of events, that the problem would not have occurred if the spent catalyst slide valve had not leaked, or if the steam had not leaked out of the expander, or a combination of both.   

It would be an over-reaction for regulating agencies to enact new, burdensome rules on the entire industry in an attempt to prevent an accident that almost never occurs.  Yet, there are calls for exactly that, to make the refining industry be subjected to inherently safer design.  

A better approach is to increase the penalties and fines for those who violate the existing safety regulations, so that a violation will be so costly that the workers, and managers, exercise extreme caution.    One example, was a refinery management that was interested in the impact on their US refinery of an explosion similar in scope and damage to the one in March, 2005 at BP's Texas City Refinery.   That explosion killed 17 people and hospitalized more than 100 others.   The injuries, deaths, and damage occurred after human error caused flammable liquids to overflow a vent pipe, vaporize, reach an ignition source and explode.   In that case, the equipment was fine but the humans made errors.   That explosion cost BP several billion dollars in fines, repairs, and legal settlements.   Such a sum would bankrupt many smaller companies.  That sobering fact was what was brought home to a different company.  Safety is vital, not only for the safety and lives of the employees, but surrounding communities, and also the ongoing viability of the company in many cases.  see link to BP Texas City Explosion of 2005. 

In the Torrance explosion, a combination of human decisions and equipment malfunction were at fault.  In retrospect, it would have been better to shut down the main column, and insert a blind flange in the line at the spent catalyst slide valve.  In short, make it almost impossible for any hydrocarbons to leak into an area where an ignition source could create a fire or explosion.  

UPDATE 1:  16 January 2016 - The Chair of the Chemical Safety Board wrote a letter to the editor opining that California refineries need more regulations to force them to operate safely (my paraphrase).  see link to the letter to editor. 

Chairperson Sutherland wrote:  

"If finalized as currently written, California’s new safeguards (i.e. regulations) for oil refineries would strengthen the state’s oversight by requiring management to take steps to reduce risks to the greatest extent feasible. And the draft regulations include some important safeguards on the forefront of refinery safety, such as requiring incident monitoring and tracking data.

I eagerly support Gov. Brown and the state Department of Industrial Relations (DIR) for initiating these changes. I believe the actions being taken here in California are some of the most substantial positive safety changes happening right now."    

Chairperson Sutherland added that "California can lead the nation in refinery safety," an indication that the new California regulations would, or should, be extended to all US refineries.   

I note in passing that Chairperson Sutherland has zero technical education, as her biographical sketch available online states she holds a BA in Political Science/Art History, as well as an MBA (in Information Technology) and a JD.  She is an attorney licensed in Maryland.  Her only brush with non-computer technology appears to be a brief stint at Department of Transportation's Pipeline and Hazardous Materials Safety Administration.  She has been Chair of CSB since August, 2015, a total of six months as of this date.  

 -- (end update 1)

Here ends this article for today.   There may be additional updates.  

Roger E. Sowell, Esq.
Marina del Rey, California
copyright (c) 2016 by Roger Sowell, all rights reserved. 

Unexpected Results From Computers

Subtitle: If A Human Can't Find It, The Result Is Unexpected

Computers are sometimes discussed as slaves to their programmers; that is, they produce only the results the programmer wanted when he (or she) wrote the software that runs in that computer.   I have discussed this before on other forums, and this article addresses some of my experience in this arena. 

My qualifications to discuss computers and software programming are as follows: software development, design, debugging, and various sorts of computer programming since 1971 (44 years at this time), from simple BASIC, Hewlett-Packard's programming on HP-35 pocket calculator, FORTRAN of various vintages (starting with FORTRAN 66 on IBM mainframes), Artificial Intelligence software in LISP and neural networks, Lotus 123 and MS Excel (tm), to html and similar programming on modern internet applications.   Computing platforms covered a variety, such as IBM mainframes, CDC machines, programmable pocket calculators, desktop PC (personal computers), and modern laptops. 

The primary purpose of my programming efforts has been related to chemical engineering tasks, where very large databases from a process plant running 24/7 provide information that must be retrieved, analyzed, processed, and results returned in a timely manner for appropriate decision-making.   Also, very complex oil refining, petrochemical, and inorganic chemical process unit simulations (including kinetics in reactor systems) were developed and enhanced - including various forms of optimizers (e.g. LP, successive LP,  and open-equation).   In short, computers and software are merely tools to the chemical engineer, not our reason for living.  We have real problems to solve in the real world, with (at times) hundreds of millions of dollars at stake (or more).  There are almost always time constraints in the problems that require a quick solution, such that a program that runs too long is totally useless even if it provides the correct answer.   The process unit conditions will have changed far too much for an answer to be useful.   Time frames for computer solution can be measured in hours, but often a few minutes is required, and on rare occasions, a few seconds.  

So, do the computers we use provide predictable, unsurprising results?  Are they truly slaves to their programmers?  No.   Chemical engineers know very well that our software provide unexpected results on many occasions.   This is a hard concept for many to grasp, perhaps because they have been conditioned to believe that a computer merely adds 1 plus 1 to obtain 2, but does it very, very quickly.  And, I agree that computers can and (sometimes) do add 1 plus 1 to obtain 2.  And, they do that very, very quickly.  

Examples of unexpected results follow.  One arena is in optimization of complex process units.  Another is recognition of patterns, such as "this event X always happens after that event Y occurs, but only after Z time passes from event Y."  

Complex process unit optimization.  

Process modeling and optimization is sufficiently important in chemical engineering that, for example, a session at an AIChE conference was held recently (see link), with the session description as:

"Modeling is the art of simplification of complex physics underlying the chemical processes to account for observed phenomena and make falsifiable predictions. A good predictive model provides the basis for optimization of objective function in a multi-parameter space. This session invites talks that elucidate the practice of model building, the challenges involved in optimizing validated models and reduction of optimized results to practice."

In addition, a major division of AIChE is devoted to computing and optimization, the CAST division (Computing And Systems Technology Division) (see link).  Their description reads:

"The CAST division provides relevant programs for AIChE members who share interests in computing and systems technology, especially in the analysis, design, and control of process and management systems. CAST also coordinates the Institute's activities with other societies active in this field."

Many other conferences, seminars, webinars, books, etc. are devoted to optimization in chemical engineering (see link). 

The unexpected results occur when the process model, or process model with an optimizer produce a solution that a human could not have produced, especially within the timeframe required.  Some may argue (and many have) that this is a matter of semantics, that the computer's results are within the realm of possible outcomes that the programmer allowed the computer to explore.   The argument appears to be that, given enough time, even a human could have found the same solution.  However, that defeats the purpose when, by definition, a solution is worthless if not produced within the required time constraints.  

One personal experience follows, of an unexpected result in a simulation of a petroleum refining process unit; a vapor-recovery process for a Fluid Catalytic Cracker (FCC) unit in a large, integrated and complex refinery in the US.  There was no chemical reaction in this process, merely five inter-connected towers with vapor-liquid equilibria, mass-transfer, heat-transfer, mass recycles, heat recycles, and absorption, all constrained by the typical issues of pumping capacity, compression capacity, heat exchanger capacity, and tower diameters.  The goal, or objective function, was to maximize unit throughput without undue loss of valuable components to a fuel gas system.   The process unit was simulated on an industry-standard process flowsheet software, then optimized with the internal optimizer.  Manipulated variables included the lean oil flow rate into the primary absorber, sponge oil flow rate into the sponge absorber, total feed rate, pressures, temperatures, and various heat inputs and removals.  

In this particular case, conventional, prior "wisdom" held that the lean oil flow rate was to be minimized - reduced to zero - because the lean oil material consumed energy due to being recycled.  However, the simulation and optimizer showed that the energy savings were very small while the value of increased feed rate due to a non-zero lean oil rate was many times greater, indeed, extremely valuable.   The solution was implemented with the predicted results being measured and then confirmed.  (note the "... falsifiable predictions" wording above; this lean oil optimization certainly qualified).   So, was this an "unexpected result?"   I maintain that it was, because the then-existing management believed the path they had followed was optimal until the new operating paradigm was presented and implemented.  They were quite impressed when the FCC unit was able to process a significant increment of feed (approximately 10 percent more per day).  

Other examples of unexpected results are very common, almost too many to mention.  Another refinery used a computerized kinetic simulation and optimizer on their FCC plant and found they could increase feed rate and conversion to a much more profitable state.  The same has been done many times on other process units.  

Pattern Recognition 

As mentioned above, process plants, including oil refineries, have databases with large amounts of data.  A process engineer routinely extracts data from the database and performs analyses to follow the progress of the unit.  There may be catalyst deactivation, heat exchanger fouling, distillation efficiency reduction, among many other parameters that change rather slowly over time.  Other changes are more rapid, sometimes requiring only minutes or even seconds to appear in the data.   Where a pattern can be recognized, a good engineer can and should determine the cause.   Indeed, it is fairly simple in these days to use a data-mining software to rapidly evaluate thousands of variables in pairs and other combinations to determine the extent of any correlation.  In engineering, especially chemical engineering, linear fits are possible, but the physics of the process dictate that many times, a log or exponential, or quadratic fit are indicated.  

An example from personal experience follows.  In a complex oil refinery that processed heavy oils in a Delayed Coker Unit (DCU), and processed the virgin and cracked gasoils in a FCC, data analysis found a pattern:  the cyclical production of heavy coker gasoil created an undesirable cyclical change in FCC operation.  Simulation and optimization on the FCC showed that a better operating strategy was to store the coker gasoil for a short time rather than pump the coker gasoil as it was produced into the FCC system (note, there was a gasoil hydrotreater upstream, as usual).  A steady flow of coker gasoil allowed the FCC controls to more easily optimize the unit; in effect, the control system was always "hunting" for the optimum as the coker gasoil rate fluctuated.   This result was contrary to the established "wisdom" that it was more profitable to minimize all storage, and run intermediate streams between process units right away rather than into storage and back.  The solution was presented, then implemented with great success.  The result was unexpected in the eyes of the then-existing refinery management.    

(Note: this is entirely consistent with my career as a process consultant; many times the conventional "wisdom" was false, based on invalid original assumptions, or the previously valid  assumptions had changed materially.  One refinery with a Hydrocracking Unit told me and my colleagues that their unit was optimized, thus there was no need for us to examine it.  I asked when the latest optimization had been performed, and the reply was "a few years ago after startup."  That refinery made a substantial increase in profit after being shown why a Hydrocracker Unit optimization should be performed on a periodic basis.)

Conclusion

It has been shown that unexpected results from computer software indeed exist, both for complex process unit optimization and for pattern matching.  Other categories also exist, which may be the subject of future articles.  

Roger E. Sowell, Esq. 
Marina del Rey, California

copyright (C) 2015 by Roger Sowell