Exhuast Gases for Energy

Stability and control warrant some loss in energy.... unstable states can create greater loss of energy.

I can only speculate but I doubt that there is no single simple reason why they don't harness this waste energy. Since this is a business, it most likely boils down to the simple investment cost versus benefit return exchange.

Sounds like a good opportunity to subcontract it to a company with more motivation. It might be worth it for a small company to take the waste gasses being burned in the above image run them through a burner and either boil water or spin a turbine, would probably clean up the emissions too.

Drew

That flame isn't really very hot, so it will take an expensive (large) heat exchanger to recover much energy. If the exhaust gases are cooled below the dewpoint of any corrosives they contain (such as sulfuric acid), this condition (known as "wet-stacking") will soon corrode parts of the system. At any rate, these are two of the obstacles.

I was thinking of feeding the waste gasses into a natural gas turbine or boiler. That way you get a clean burn of the waste and extra heat for the boiler, or an extra kick for the turbine.

Drew

you would need to pipe somehwere and i suspect thats the problem cost, they can make more money from the oil than the gas.

I think the one point that may be missing in your explanation is that your industry has little incentive to operate as efficiently as possible.

Unlike the paper and pulp industry that needs to be as energy conscious as possible to be "competitive". That industry uses process wastes to fire boilers, turbines versus valves to reduce efficient high pressure boilers to usable process pressures. They also use heat in any form to reduce the process cost.

They aren't driven by a desire to do good or be acceptable, that is part of doing business in the paper industry otherwise you can't survive.

Your waste heat may not be of a reliable source or non corrosive in nature, it is in fact usable.

Bottom line it is the bottom line, which is driven by your industries environment.

What totally ignorant piffle.

Where do you come up with such insightful information? Mother Earth News or Sierra Club possibly?

When you are handling millions of tons per year the advantage of any small savings per ton becomes very clear - you are forced to chase the savings to the maximum extent possible.

If some company is not investing in such things they are most likely broke and going under soon.

You make many valid and good points, I wish you had registered so you could benefit from the cookie of the good answer.

So, a turbine would be difficult even if designed to handle the harsh fuels, what about a boiler? As I said above if I set up a small plant next door to generate electricity and had one (or more)furnace designed to deal with the harsh fuels and blended what was piped from the flare header with another fuel wouldn't I still be utilizing the btu's of the waste fuels and burning them cleaner than a the flare? I would also be moving the flare even farther away from the refinery. I know in many refineries there are many old pipelines that are not utilized, perhaps even one conveniently placed for a small power plant.

Drew

Drew,

Please read #15

The high levels of H2S in the flare gasses would also be extremely corrosive to a boiler. Pyrophoric Iron Sulfide formation in the lines that feed the gas to the boiler could also be a concern. You could send the gasses to a Sulfur Recovery Unit (Claus Reaction) and get the H2S down to a few ppm's. SRU's are extremely expensive to build - I was involved in a startup of one in the early 1980's - the cost was (if memory serves me) in the $60 to $70 million (US) dollar range. I have no idea what it would cost today. It would be very difficult to recover your investment even after selling the sulfur. SRU's can also be a very dangerous place to work in or live near - the H2S stream is nearly pure (900,000+ ppm's) - if you had one little whiff at these levels you would be dead before you hit the deck. Edmund

They probably don't because there is no way to control the Btu content and consistent continuous delivery.

When I was a little boy We took family vacations traveling through the new oil fields where my father worked(southwest US in the late 40's and early 50's).The night-times were spectacular with the flammable gases being burned off from well after well, all around us. When my brother and I asked my dad why they were burning off the gas, he told us that they were still installing pumps and pipelines to move the liquid crude oil, and the gas pipelines weren't built yet and not profitable since the market for large amounts of gas wasn't developed yet. The companies used diesel engines burning filtered crude for their energy needs. In other words, it doesn't pay them in profit to produce energy that way in a new field, and if their is enough gas to pay them to collect it, they do.

There is a possibility of using the heat of these exhaust gases to operate the Vapor absorption systems for air conditioning purpose id the facilities of the industries need to be provided with comfort condition. There is separate group CHP (Combined Hear Power) under CIBSE(U.K ). Chartered Institution of Building Service Engineers who perform many professional research work on CHP technologies.

I concur..... reuse of an unstable heat source for a supplementary lithium bromide cooling system would be ideal, in an certain environments.

28 years ago as a part of my graduate program I did a feasibility study to use the automobile exhaust to air condition a small car using Vapor absorption system . Later stage I could not proceed further on this study.

The flare is implemented to "burn" the methane , hydrogen sulfides etc present at the exhaust gasses of the process.

With a moderate cost of electricity it did not seem viable to tap into the energy.

It would also be expensive .Any obstruction to the natural burning may cause undesirable CO etc to form.

However with the sharp rise in costs SASOL applied to use the energy to produce steam and run a turbine to produce power. Thy aim for a substantial reduction of costs.

Maybe even earn carbon credits.

I have often wondered the same thing & can only assume that if they (the oil COs) generated electricity then the power company's wouldn't need to generate as much therefore they wouldn't need to purchase as much fuel oil can you see where I'm going with this,Governments should ban the oil company's from burning off & make them use the energy to produce power even on oil rigs, the pollution alone should make them do something about it.

Bazzer

Moot point (at least in the USA)- at least 80% of our power is generated from burning COAL - not OIL or NATURAL GAS. We also have cogeneration plants that are privately owned that sell power back to the grid - most of these run on natural gas and/or fuel oil (mostly ultra low sulfur #2). It would be virtually impossible to capture all of the flare gasses - especially considering the fact that most of the releases are unplanned -when a safety valve lifts it usually boils down to 2 choices - burn it at the elevated flare or burn down the plant. I vote for the flare.

GA!

Do you have any installed in a refinery? Any picture, presentation or case study that I could forward to my contacts at refineries? I would prefer that they contact you if interested.

Does it reduce the temperature of the flame needed to reduce the compounds that must be burned?

Hi, Marcot.

Installed in a refinery .. yes and no. Explanation below ...

The system that my firm markets is a combined (dual) cycle version of an Organic Rankine Cycle, and ORCs have been used extensively since the early 20th century. They're principally found throughout the hydrocarbon industry (refineries and pipelines, and possibly on platforms, among others).

ORCs themselves are identical to 'standard' Rankine Cycles, which are used to generate power from non-organic (hydrocarbon) heat-transfer fluids. For example, steam-driven PG is a Rankine Cycle where water is used instead of an organic fluid.

Rankine Cycles, whether Organic or 'standard' are closed systems that comprise the same elements:

- a boiler/vaporizer that vaporizes and pressurizes a fluid;

- a turbine that expands/depressurizes the vaporized fluid, and possibly condenses it partly;

- a condenser that condenses all of the fluid to liquid;

- a pump that pushes the condensed liquid back to the boiler/vaporizer.

Steam-based systems used water as a fluid; ORCs use organic fluids; the system that my form markets uses propane, which is an organic fluid.

The combined-cycle (dual cycle) system is essentially two ORCs configured so that the first feeds heat into the second, with both sharing a common pump and vaporizer. Functionally, they're like two separate ORCs in cascade. The result is a composite, integrated system that share a common section, and whose range of operating temperatures peaks out at 900-1,000 F, where their performance is very close to that of a steam-based system's.

So, to answer your question: yes, ORCs have been installed and run (especially in the hydrocarbon industry) since the beginning of the 20th century; and no, my firm's systems, which are composite 'dual' ORCs haven't been installed in refineries. ORCs have been installed, but the particular (innovative and patented) arrangement of ORCs hasn't. The reason is simply that this is a new twist on an old system and that it takes time to get the word out.

In refineries, ORCs are frequently used to drive big equipment such as compressors or other mechanical loads, which substitute for the gensets that would be used if power were to be produced.

MORE DETAILS

ORCs operate typically at temperatures less than 350-400 F. Most steam-turbine based systems typically operate at higher than 850 F because their efficiency drops like a stone below 800-850 F. Until the design of the system my firm markets, no other system could recover process heat at intermediate temperatures and use it to generate power without raising the temperature of the fluid wherein the heat resides (by burning some fuel or other) or cooling it (thus reducing the potential thermal efficiency for PG). My firm's dual-cycle system spans the low end, through the intermediate end, and on to the high end of temperature, at ever-increasing efficiency from low temperature to high.

Two other significant advantages of my firm's system: no water needed (no steam = no water ... great in dry places!); and no operators needed either (no steam = no steam-engineer crews needed = can be supervised remotely or by existing personnel at existing process plants where the system is added ... no need to hire anyone to operate.) No need to hire anyone for maintenance, when installed at an existing process plant; the system is low-maintenance and maintenance shutdowns can be few and far between.

Cheers!

DZ

More to the point do you have any of your turbines installed in a hot flare system in a refinery - that is using only gas going to a hot flare.

The world gets real exciting real quick if you ever back draft that flare - has a tendency to reorganize the scenery for a couple of kilometers or more all around.

That flare gas can be some of the nastiest stuff around - it is not methane a refinery flares.

russ123 said

"The world gets real exciting real quick if you ever back draft that flare - has a tendency to reorganize the scenery for a couple of kilometers or more all around"

Impossible beyond any rational belief

#1 There are no air registers anywhere near the ground on a flare. The design is more like the tip of a propane torch.

#2 It is not designed like a boiler or furnace firebox where it would be possible(but not very probable) to have a positive pressure in the firebox and pull air thru the stack and have the flames shoot out the air registers. This would apply mainly to a natural draft unit not a forced, induced or balanced draft one.

#3 I think you probably have watched way too many disaster movies. A couple of kilometers. Be real.

#4 What does your response have to do with the original post ?

Sorry Post 26 should have been in response to post 25 not post 24

@ Guest - Seen the aftermath of such a scenario - in Qatar some 35 years back.

Impossible? No and apparently you are not terribly rational.

I have been in meetings where some idiot thought too much valuable energy was going to waste in a flare so it should be possible to capture and use the flare gas. The guy was commercial - not real world.

That is exactly what the original post suggests doing.

Hhhhmmm ... concerning turbines running off a hot flare system: maybe there are ORCs running on gas that goes to flares, but none of our systems have been installed to run on those. So the answer is maybe yes, and no

Bear in mind that only our systems' the heat exchanger would be exposed to gas that would otherwise be flared. Plus, not all gases to be flared need pass through our system ... problem ones could be diverted straight to a flare, if need be.

As concerns backpressure in the flare line: we'd install induced-draft fans at the outlet of the heat exchangers.

Cheers!

DZ

P.S. Also, I forgot to mention that the special burners that we use would generate hot post-combustion gas of 2200-2300 F temperature; if hot hot heat is needed rather than electricity, that could serve for process use.

The burners consist of tuned pulse burners that create a standing sound wave that burns liquid and gaseous fuel (including syngas, so solid fuel indirectly) to generate very hot post-combustion gas. Think souped up B1 rockets. For syngas generation from solid fuels, including biomass, we have syngas-production (sublimator) systems, too.

You are correct I know little about refinery economics, I thought the flare offs were a constant sort of thing. My opinion was formed by casual observation of some stacks in New Jersey that are coincidently blowing off flame every time I drive by, and for the duration of any visits I make when working on their equipment.

The paper industry isn't that pure either. You can see enough steam blowing and leaking out of the average paper mill to power up good sized machines. Probably all relief valves.

Flaring should not be a constant thing. However, there is always a small flare (pilot flame) burning. This is to ignite the main flare in case of a release.

There are companies that manufacture igniter systems that only operate when a flow or pressure is detected in the flare header this saves the fuel gas that would be used by a standing pilot. Eliminating the pilot is probably more public relations oriented than cost savings driven. Failure to ignite would cause a large release of unburned hydrocarbons to the atmosphere - components such as H2S for example are heavier than air and would cause major health and safety issues if they settled over populated areas. Edmund

Doubt it is relief valves. If they leak all the time they can not be depended upon to function as required in an emergency - and they are an emergency device.

They are going to have a constant blow down to maintain water quality anyway.

Most of the flaring you see in a refinery is from safeties that have lifted due to over pressure. Safeties should not leak at all. A small amount of the flaring is from vessels being vented to the flare during startups and shutdowns. Flares usually have water seal legs (similar to a trap on a sewer line connection) of different heights. When a major event happens all of the water legs blow and all the flares light up big time. Some safeties have a "rupture disc" below them to protect the safety from contact with the process stream. These are a headache to maintain. Edmund

Dear Mr.mgb,

It will not be economical to recover that energy. But it cannot be let out in to atmosphere since it will contain CO and other NOXIOUS matter. Hence burnt out.

DHAYANANDHAN.S

I still think about this thread every now and then. I still don't know how it can't be economical. I visited a refinery in Borger, in the North Texas panhandle. They had a bunch of flares lighting up the night sky. I saw two powerplants about an hour's drive away and I imagine there is probably existing piping in the ground already where they could pump the flare gasses to the plant, and blow it into the boiler. The controls in the boiler would burn the gasses more cleanly reducing the NOx emissions and unburnt hydrocarbons that are present in the limited controlled flares.

I was told that the refinery used to have a small steam power plant where they could have burnt the flare gasses, and I forgot to ask why they didn't just burn them in the burners they use to heat the crude.

Drew K