But because the alkylation process is catalyzed by one of two strong acids either sulfuric or hydrofluoric-and because light, volatile hydrocarbon streams are involved, it is the focus of much attention by regulatory and environmental groups and refiners.
Refiners have spent millions of dollars in recent years implementing sophisticated, effective safety systems on these units. At Oil & Gas Journal's recent seminar on alkylation in the new fuels era, held in Houston on Oct. 31 and Nov. 1 this past year, these safety systems were a frequent topic of discussion.
The following questions, answers, and comments from the meeting transcript reveal how refiners are coping with the increased attention focused on the safety of their alkylation plants.
John Felten, Senior Consultant, Arthur D. Little Inc., Cambridge, Mass.: Do you see anything that would indicate that the regulations in Southern California on HF could be extended to other areas in California or anywhere else in the United States?
Urvan Sternfels, President, National Petroleum Refiners Association, Washington, D.C.: Well, I'll be honest to tell you I don't know a lot about it. If I were a politician up here, I'd give you a long speech about it. I do think the concern hasn't completely gone away, in all honesty, about HF.
There will probably be a recurrence of some initiatives somewhere. Some of the environmentalists aren't going to let this sit still. I just don't, at this point, see great enthusiasm for doing something more than keeping an eye on it and being watchful. EPA's report, I think, satisfied a lot of folks who are more objective than some of the more ardent enemies of HF in the environmental community.
It's an area, obviously, of great concern if there is a release and, frankly, that's what might trigger something. If there is a significant release and it results in some bad things happening to people in an area, I think that's going to trigger more activism than anything else. So that's the thing to watch for. I might add, that's the thing to avoid as well.
Anne Rhodes, Refining/Petrochemical Editor, Oil & Gas journal, Houston: Correct me if I'm wrong, but don't you have HF sensors that are hard-wired to the air quality management district (AQMD)?
Joel Maness, West Region Manager, Mobil Oil Corp., Torrance, Calif.: We do. We have 29 sensors scattered about our unit. They are hard-wired to the AQMD. The alarm goes off as quick as the sensor goes off. We have to notify the AQMD anytime we're doing calibration on our sensors.
We've got all the devices. All the mitigation devices that AQMD was requiring us to put in place, to a large degree, we'd already agreed with the city through the risk management and prevention program (RMPP) process to have in place. It's business as usual for us.
Anne Rhodes, OGJ: Can you make comment about the general outlook for HF alkylation in California?
Joel Maness, Mobil Oil Corp.: Let me let you draw your own conclusions. I feel very, very good about it. I feel very good about the technology that's been developed. I feel very, very good about our ability to demonstrate that, with the modified acid technology, we'll be able to operate in such a manner that we represent less of a risk to our community than if we switched to a sulfuric process.
You're going to hear a paper on it. You're going to see a presentation on it. Reach your own judgment. I can tell you, we're not rushing out to build a new unit because I feel extremely good about this new process.
John Felten, Arthur D. Little Inc.: Can you say anything about what the cost of these systems has been for that refinery?
Joel Maness, Mobil Oil Corp.: We've probably invested between $30 and $50 million altogether in the different mitigation devices: water deluge, acid evacuation, a lot of the different devices that we've put in place. Quite a lot of that is because, in some cases, it was serial number 001, and had it not been, it would have been a whole lot less.
We've also invested, as a corporation, a huge bucket of money in this modified HF research that we've been doing. I don't know the exact number on that, but I suspect it's in excess of $50 million.
Vincent D'Amico, Process Design Manager, ABB Lummus Crest, Bloomfield, N.J.: What are the economics-capital and operating-for HF mitigation (deluge and HF modifiers) relative to those for conversion to H2SO4? A follow-up: have any non-licensers evaluated such a switch?
Anne Jezak, Marketing Engineer, Stratco Inc., Leawood, Kan.: Stratco published a paper at the 1994 NPRA annual meeting on a low-cost conversion technology that we're offering. We had a third-party engineering and construction company do a cost estimate for this process on an existing 10,000 b/d alkylation unit, and the cost for making the conversion was approximately $15 million. In many cases, this conversion would also allow you to expand the capacity of the alkylation unit, which is a nice additional benefit.
In talking to folks in the industry, I have heard very wide ranges for costs for mitigation, from anywhere from, say, $2 million for a very, very basic mitigation-which isn't much-all the way up to, Mobil Torrance yesterday gave us a figure of $50 million, which probably includes things other than strictly HF mitigation, but maybe you can use the $30 million that they spent at Mobil Torrance.
So there's a very wide range of costs I myself have heard for HF mitigation. This does not include any of the HF modifiers that are yet to come to market.
Bob Puschinsky, President, Bob Puschinsky Inc., Seabrook, Tex.: I want to say that I know of at least one very large refinery that came in at $18 million. That was not on the West Coast.
John Felten, Arthur D. Little Inc.: Of the various numbers I've heard tossed around, $20 million for a full-size unit seems to be in the ballpark.
Henry Hachmuth, Senior Staff Advisor, Phillips Petroleum Co., Bartlesville, Okla.: It depends on who's doing it. We have a system that comes in quite a bit less than that, that works well.
Ralph Harris, Group Leader-Process Engineering, Citgo Petroleum Corp., Corpus Christi, Tex.: What is the most effective type of water mitigation system-curtains or cannons?
Henry Hachmuth, Phillips Petroleum Co.: That's a good question. I don't think anybody really knows. I think what you have to do is figure on your situation-it's a case-by-case basis.
If you're in a very cold climate, the water cannons are much better. You can't really handle the curtains. There's a lot of modeling on the curtains and we know that they're pretty good.
The problem with the cannons is they're very, very difficult to model. So to write the programs to figure out how good they are is hard. But they are effective also.
I really think it's just a matter of your situation and what's best for your location.
Bob Puschinsky, Bob Puschinsky Inc.: I would reinforce that. But I'll give a specific example of one refiner on the Gulf Coast who, with extensive Wind tunnel testing of the exact configuration of his unit so be knew pretty well what the winds were going to do on a very localized basis, feels very confident that he has 95% water curtain efficiency.
I don't think you're going to reach that same number with a monitor. Of course, the water curtain has to really be running in association with a monitor, also in case you have a jet that wants to punch its way through the curtain. That is, a small hole or a hole that you have the HF-bearing material just overwhelming the curtain in one spot. You have to knock it back.
So you need a combination of the two, really, to get the extremely high efficiencies.
Henry Hachmuth, Phillips Petroleum Co.: You need something to break up the jet if you had one.
Bob Puschinsky, Bob Puschinsky Inc.: That's what you're using the monitor for.
Don Graffy, Technical Coordinator - Cracking, Uno-ven Co., Lemont, Ill.: I've heard several speakers over the last 2 days make statements suggesting that sulfuric acid alkylation is safer than HF operation. Would the panel care to comment on this matter, citing statistics where possible.
Bob Puschinsky, Bob Puschinsky Inc.: I'd like to quote from page 10 of the EPA's hydrogen fluoride study: "Hydrogen fluoride IDLH [immediately dangerous to life or health level], 30 ppm; sulfur dioxide, 100 ppm; sulfuric acid in the form of sulfuric acid mist, 20 ppm. Emergency response planning guidelines (ERPG): sulfuric acid (as in sulfuric acid mist), 7 ppg; hydrogen fluoride, 50 ppm; sulfur dioxide, 15 ppm."
At least in part, that says that some of the sulfur compounds are competitive for toxicity with HF, and maybe win the battle.
Henry Hachmuth, Phillips Petroleum Co.: We at Phillips feel that the two processes are more or less equivalent on a safety basis and they're both needed and both viable processes and both can be operated safely.
Anne jezak, Stratco Inc.: There always has to be another opinion in the crowd.
Stratco would feel that sulfuric acid is safer to operate than HF acid. One of the things that often gets lost in this debate between sulfuric and HF is, when you look at one of the real hazards of operating an alkylation unit, it's actually very large volumes of LPG.
If you look at the accidents that occur, really not very many of them occur with either acid. And I think sometimes we lose sight of this.
LPG is, far and away, the largest hazard within an alkylation unit. If you're running and operating an alkylation unit, I myself would pay a lot of attention to that.
That having been said, Stratco's Position would be, if you were to have a release or a spill of either of the acids, it would be much easier to contain and to safely neutralize, and to hopefully not have any problem with the surrounding community, if you had a spill of sulfuric acid-which, falls to the ground as a liquid and does not vaporize-vs. HF, which is a vapor or actually an aerosol.
Bob Puschinsky, Bob Puschinsky Inc.: The question is, can you get a cloud from the two different processes.
And the answer is, adamantly, "Yes, from both."
You get an aerosol from the HF by blowing it out through a hole in the side of a vessel or a blown gasket. But you get a cloud from a sulfuric acid alkylation unit or sulfuric acid regeneration unit by, in the case of the acid regeneration unit, a leak of either S02 or S03 and, in the case of the sulfuric alky, from a foam-over.
Foam-overs do occur, much more frequently in the sulfuric case than they do in the HF case because you have to run much closer to your runaway point. You're running at 90%, or thereabouts, and you're going to have a runaway somewhere in the order of a couple or three percent away from that. In the case of HF, you run in the 90% realm and your runaway occurs much lower than that.
In the case of the sulfuric, once you've had the runaway, you've got a foaming, polymerizing mess on your hands that frequently ends up in tanks. The way people like to get it out of their tanks is put it in rail cars or barges.
Very recently, a significant amount of that material was put into some rail cars, the rail cars get out in the open, ruptured their disks, and spewed forth both a white noxious cloud and an S02 cloud. The white noxious cloud being S03, then going into the form of sulfuric acid mist, is capturable by water mitigation, as is the HF. Unfortunately, the SO, is not appreciably capturable by this and 1 believe, if you remember the numbers on IDEH and ERPG, S02 is not without risk.
Copyright 1995 Oil & Gas Journal. All Rights Reserved.
