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GTL

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pmover

pmover

Mechanical
Sep 7, 2001
1,507
fyi . . .

Will Gas-to-Liquid Reach Flood Stage?
With the price disparity between natural gas and oil at an all-time high, gas-to-liquid (GTL) conversion plants are on the upswing. High capital costs — a recent plant cost $19 billion — limit them to areas with reliable, long-term feedstock availability and high regional demand for transportation fuels. Another market leveler is new restrictions on sulfur levels in conventional crude products, improving demand and prices for GTL products. According to GasWorld.com, even the lowest octane GTL products, such as naptha, are in high demand as an oil sand diluent. This video describes the "world's largest GTL plant."


enjoy!
-pmover
 
Don't forget that at best, a GTL plant converts 1/4 of the carbon in the feedstock to useable hydrocarbons. The other 3/4 end up in the atmosphere. From that perspective, coal looks pretty attractive.
 
People keep adjusting the "original gas in place" (OGIP) numbers in the Shale, but there is at least 20,000 TCF of gas (a REALLY big number in case TCF doesn't mean much to you) in the shales around the world. In the U.S. and Canada current natural gas prices are at 1970's levels because of new shale-gas supplies. At the current natural gas prices, capital is rapidly leaving the gas side of the industry. So far this year I've heard of over 1,000 wells that were budgeted for gas fields in the U.S. for 2012 that have been canceled in favor of liquids projects. The gas is there. The market isn't.

Enter GTL (and to a lesser extent LNG) and if you can put 1970's priced energy into a 2012 priced motor-fuel market you can make a LOT of money. Even with the "carbon effeciency" hit mentioned above, with $10/MCF gas (five times first-of-month March, 2012, price) you can sell GTL diesel at $3/U.S. gallon (75% of current market) nd have a 25% rate of return in an industry that rarely sees 5% return on capital. Putting a GTL plant in Pittsburgh and another in Baton Rouge or Little Rock looks to me to be the biggest no-brainier I've ever come across.

Enter the EPA and the e-NGO's. Current estimates are that the permitting process for a GTL plant is on the order of 10 years. Just filing a permit form guarantees that someone will file a lawsuit. EPA won't even open a permit application until the day before their response deadline, and then they'll find a typo and reject it.

GTL has the potential to return the gas side of Oil & Gas to profitability in North America, significantly reduce the cost of all goods that rely on ground transportation (i.e., all goods), significantly lower the trade deficit, and create a few million high paying jobs. No one is excited about it because the permitting, engineering, and construction of a GTL plant takes longer than the term of one president.

David
 
In an era where the whole carbon tax/carbon credits thing is up in the air, don't hold your breath on seeing any mega-GTL projects permitted.

A far quicker and smarter change without the permitting problems would be to convert a lot of coal-fired electric plants to NG. Nowhere nearly as efficient as building new gas turbines, but still WAY more efficient than GTL...

With gas so cheap, I'd bet on CNG becoming a commuter motor fuel, which to me makes quite a lot of sense. It already has become one to some degree in California.

Not that GTL doesn't have a place: lots of people are trying to develop small GTL units to go after gas which is currently being flared. 25% efficiency of converting a fuel to useful products makes a fair bit of sense when compared to 0%.
 
There is a CGN Station being built at the gas station a few miles from where I work in Colorado. I don't know if it is for cars or semis but it is under construction at the gas station. I am betting that it is govt funded as I don't see a gas staion going out on a limb like that to install the system.

Regards
StongCold
 
Ever driven a dual fuel gasoline/CNG vehicle? It is way less fun than you think. Engine hp in the CNG mode is about 35% of hp in the gasoline/petrol mode. If you started from the ground up and build an engine with the proper compression ratios, for-purpose fuel delivery, proper heads, cams, valves, etc then you might get enough power to pull away from a stop light. On top of that, the CNG tank takes a LOT of space.

We had a fleet of CNG trucks in the San Juan Basin of Northern New Mexico in the early 90's and gave bonuses to anyone who ran their truck on CNG more than 50% of the time. After 3 months we lowered that to 20% and didn't find many takers. Performance was unacceptable.

The 25% effeciency number has been quoted a couple of times above and it didn't sound right to me so I looked around. I found the Natgas.inro site and the linked article shows the big Sasol Plant uses 97 MMCF/day to generate 10,000 bbl/day of motor fuel if the gas is 1000 BTU/SCF (0.037 MJ/L) and the motor fuel is diesel with an energy content of 38.6 MJ/L, then the Energy Out divided by the energy in is 60% which is in the range of conventional crude refineries. The article uses the average of three plants and gets 58% of the input energy gets out the tailgate as motor fuel. The author's conclusion about rising feedstock prices makes me think the article is a few years old, but the math still seems to be more than twice the 25% efficiency quoted above. Any idea where the disconnect is? I saw a California site that mentioned that GTL was 1/4 as effecient as burning the natural gas directly, but it was a non-technical article that was kind of garbled and it looked like they were comparing apples to Volkswagen's.

David
 
I was just thinking, and this may be simpler than I thought. Natural gas sells for $2.50/MCF. 100 MMCF would sell for $250k.

Diesel sells for $4/gallon. There are 42 bbl in a gallon so 10,000 bbl would sell for $1,680 k.

So the feedstock price is 15% of sales price. That leaves a fair margin for capital recovery.

David
 
David: the Pearl plant takes 1.6 billion cf/d of gas (~ 320,000 bbl/d oil equivalent) and produces 140,000 bbl/d of "middle distillates, naphtha and base oil". That's nowhere nearly the same thing as 140/320 of "motor fuels".

You are correct that the energy efficiency on a feed to product is higher than 25%, but that's not the stat I stated. Unfortunately the carbon efficiency isn't nearly as high as the energy efficiency- my 25% estimate is probably low, but not too far off the mark once the fuel gas is figured in. Remember that what you're doing is partially combusting the fuel to make CO (and CO2), or directly combusting it to fuel a reformer, then hydrogenating the CO to make -CH2- and water. Unfortunately most of the energy you generate in the hydrogenation step is at too low a temperature to make beneficial heat recovery possible. At the end of the day, most of the carbon ends up in the atmosphere, not in product fuel.

You're comparing a retail price which includes excise taxes to a feedstock price which doesn't, but I'm not doubting there'd be a return on investment IF NG prices stay that low for that long. Unfortunately, at present the scale has to be absolutely titanic (i.e. like Pearl) and the feedstock basically free to make it worth the investment. There's the gamble.

 
I'm not sure what "middle distillates, naphtha, and base oil" is (are?). Sometimes engineers are our own worst enemy. The article that I linked was talking about motor fuels out the tailgate unless I completely misunderstood.

You are right about the $4/gallon being after middlemen, retailer profit, and taxes. Call the tailgate price $2 and you spend $250k to make $840k, still room for the wellhead gas price to go to $6/MCF which is a win-win.

"Carbon efficiency" is a term I struggle with. I don't want to get into the whole AGW/GHG thing yet again, but I guess that's what you are talking about. The only "efficiency" number that has ever made since to me is "in" vs. "out" at the skid (or plant) edge. If it takes me 400 BTU of input fuel to do the work that should require 100 BTU at 100% efficiency then I have 25% efficiency--I really don't care that one of the components in the process is 98% efficient if the pre- or post- process is 2%, the important number is useful work per unit of input fuel (or feed stock).

David
 
Yeah, I know, I'm boring you by bringing up the CO2 issue again, but it's a significant unresolved issue which will affect this kind of investment.

Fundamentally my concern is also one of the same kind of efficiency you're talking about David. Natural gas is the very best fuel we have in environmental terms, with both the lowest carbon emissions and the lowest toxic emissions per J of heat liberated. If you use gas that would otherwise be flared for GTL, I'm not going to complain- but using on-shore North American NG as a GTL feed is essentially wasting at least half of it just to make it into a "drop in" replacement for a petroleum-derived liquid fuel. That's a waste, even if there's money in it.

As to your concerns about CNG as a motor fuel, take a look at this:


8 gallons gasoline equivalent storage at 3600 psig, 31 mpg and a very impressive range. HP and torque stats are given, and I don't think they're just the stats for the gasoline version re-stated. If I were permitted to compress NG at home to fuel it, and they built a hybrid version to boost the fuel economy even further, this would probably be my next car.
 
The specs on that Honda look like it was designed for purpose and should have good power. A few hundred thousand of those on the road should cause people to start building CNG stations along the interstates. Maybe by a 1 million vehicles, stations off the interstate might install "pumps". That is the sequence that got diesel nozzles into most "gas" stations.

As to home refueling stations, going from 7 inH2O to 3600 psig is 253 compression ratios (at sea level) that you are going to want to do in 5 stages of compression. 8 gallons of gasoline have about the same energy content as 1 MCF of CNG. To compress 1 MCF in one hour would require 25 hp of compression--would need to be a 3-phase, probably 480V which you don't have in your home. If you can tolerate that noisy beast running all night then you could do it in 10 hours with a 2.5 hp motor that you can get in 220V single phase with reasonable energy efficiency, but even if you use water-cooling, 4 stages of inter-cooling and an after-cooler will be pretty big and take a lot of space. Oh yeah, you probably won't have enough residual pressure in your home NG system to run a home-heater or hot water heater while the compressor is running.

My home NG price last month was $0.9/therm, so 1 MCF is $9, not bad for a fill-up. 2008 prices before the collapse in the economy were $4/therm so filling up an 8 gallon equivalent tank would be $40 or $5/gallon equivalent. Like converting coal plants to NG, this idea only works if Supply and Demand don't work.

David
 
The Fuelmaker guys make a very nice little package for this purpose- a 4 stage compressor unit driven by a common shaft. Think it'd be more like 24 hrs at 1.5 hp, which you could do in the garage without annoying the neighbours too much.

I don't refuel daily. Suspect there'd be a storage tank or two involved to make that practical, which of course wouldn't impress the local fire authorities (any more than if you, say, had a couple drums of gasoline in your garage for a rainy day or the apocalypse or the like. From a purely technical perspective (i.e. rules aside) it wouldn't be too much of a stretch.
 
We put a quick-fill reservoir in the system for the fleet we operated, but to get reasonable fill performance (I don't remember the criteria, but quick-fill was pretty quick because we were paying the guy that was filling up his truck $30/hour) we had to go to 6,500 psig on the reservoir tanks. This was an industrial application so we had code vessels, tested PSV's with overpressure scenarios defined, etc. As I recall this quick-fill portion of the system was pretty expensive and added a stage of compression.

I don't know what the requirements for a home system would be, but I'm pretty sure that boiler inspector would get more excited about it than the fire marshal.

David
 
All you would have to have is a couple of idiots launch a storage tank or compressor unit through his garage roof and out onto some toddler's head and the do-gooders will put a stop to this great idea.

rmw
 
Didn't Honda already develop an in your garage refueling station?

Just a quick Google appears to show they 'spun it off' or some such.

Posting guidelines faq731-376 (probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​
 
At the end of the day you really can't fool mother nature. It takes a certain amount of energy imparted to the gas to get it up to CNG pressures. You can do this really slowly with little compressors, faster with medium-sized compressors, and really fast with big compressors. The bigger the compressor, the less idiot proof it is. The more compression ratios, the less idiot proof it is.

Now you take a fancy Honda refueling station and bust a second stage discharge valve (inevitable within 1,000 hours of operation that a valve will come apart) and the third stage discharge temp goes to 500F. Now, how many home owners are going to know how to replace a compressor valve? A vanishingly small number. How many will attempt is so that they can get their vehicle fueled and get to work? A non-trivial number. How many will die? A few. How many will kill their family with the leaking valve repair? Too many.

This is just a really high risk proposition.

David
 
Hey, I've got this great idea: we'll let people drive around in vehicles powered by a low flash-point liquid hydrocarbon mixture. Let's add some carcinogenic benzene to give it an extra kick. Oops: I wonder how many of them will try to re-fuel them at home from a jerrycan while holding a lit cigarette between their lips, to avoid being late for work? A non-trivial number of the very dumbest of them will die, along with some innocent victims as well...And then there's the thought of what happens if they get REALLY popular and we have to prop up a bunch of tin-pot dictatorial regimes to keep the supply taps open and the prices low enough to keep the politicians in power- a really non-trivial fraction of the population will die as a result of that too, and a great many of them will be innocent victims.

On 2nd thought, let's just forget the whole thing. Too idiotic and dangerous. Hitch up old Bessie, dear, or we'll be late for church!

I know full well that CNG at 3600 psig represents a whole lot more risk as a motor fuel for the average idiot than gasoline does. I acknowledged that in my post. But even with that considered, it makes a whole hell of a lot more sense than the 7,000 psig onboard hydrogen storage systems people were pitching 10 years ago! And it makes a hell of a lot more sense to me than building massive, capital-intensive GTL plants which will waste a large fraction of the source fuel in order to make diesel!
 
It really is a good thing that the nanny society hadn't yet been invented when the early decisions were being made on transportation fuels, we would still be riding Bessie (isn't that a reference to a cow instead of a horse?).

Hydrogen as a fuel has some amazingly difficult engineering challenges. It can work, but it would definitely thin the herd (those molecules are ACTIVE and keeping them in their designated locations pretty tough).

My concern about CNG is that everyone thinks it is easy. We've all been around air compressors at some time or other and methane at 3600 psig is exactly like air at 100 psig, just more so, right?. I can buy a single stage air compressor for a couple of hundred bucks. A 4 or 5 stage natural gas compressor is a bit tougher. A consumer unit won't have variable volume pockets or stage unloaders or any of that esoteric stuff. That is the right decision, but it doesn't take much of a glitch in the process for it to go entirely pear shaped.

While the guy that mops his garage floor with gasoline has earned his place in the Darwin awards, someone who replaces a valve on a compressor and reuses the gasket hasn't really reached the level of stupidity that earns a death sentence for him and his family (and maybe a neighbor or two).

We have enough trouble with trained compressor techs killing themselves with this stuff (we probably burn down a natural gas compressor somewhere in the world at least once a month). Putting 25 million of them in homes near me makes me more than slightly nervous.

David
 
David,

"...a vanishingly small number." Is that a play on words or what?

I agree with you. As hard as it is for even us technolgically astute engineering types to embrace all the latest technology (does anyone on this board over 60 like texting?) how is some single Mom going to refuel her CNG vehicle while bouncing 2 kids on each hip? She can do that while refueling from a gasoline pump at the corner gas station, but that system is pretty simplistic - even though "X" number of people world wide manage to screw it up each day. I share your trepidation about the compressor risks.

I am also a big fan of GTL and when comparing fuels, always look at the "well to wheel" efficiency.

rmw
 
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