Diesel

dan92677 wrote:How about using either a small Thorium liquid heat producing pile or a L.E.N.R (cold fusion) "Nanor" heat producer along with a condenser and stick with steam?

I don't know about cold fusion but Thorium is certainly an option down the road. Not real soon because it requires the use of electricity, especially for the smaller applications and the use of technologies that are many years away. Thorium is particularly attractive to me since it avoids the Plutonium cycle that is inherent in Uranium use and therefore that temptation is removed.

Tenshinai wrote:

"Where steam shines(and why it´s still used today) is when you put it in a fixed largescale system that includes a secondary system for exploiting waste heat, as well as using very very extended running cycles, at that point you can achieve something like 40-50% for steam engines."

Today, combined cycle plants routinely have efficiencies in the low 60% range. This is only exceeded by a modern,computer controlled diesel which can reach efficiencies in the mid 60% range. On the surface, it doesn't look like much but when one is burning hundreds of gallons of fuel per hour or more, it adds up. A quick rule of thumb used to be 1 gallon per minute per MW. That was for a reasonably modern steam plant built in the sixties or seventies which had an efficiency in the low 30% range. So, just scaling it up and neglecting everything else, the most efficient plants now produce twice as much with the same amount of fuel.

Air Tech wrote:
"Efficiency can be judged by the temperature of the exhaust against the combustion temperature of the fuel and diesels have a much higher exhaust temperature than an efficient boiler. Other tweaks include running a Kalina cycle in the boiler to drop the steam exhaust closer to ambient by running a mixture of water and ammonia (which obviously requires a closed circuit condenser), higher steam pressures (2000psi super-critical with air and water preheaters, superheater and inter-stage reheaters to extract the maximum heat from the flue gas) and the use of a turbine power plant (although a 4 stage piston engine comes close). (Kalina cycle systems also are faster to bring on line due to the higher pressures of the ammonia)."

While it is true that efficiency may be judged by the exhaust temperature, there are technical limitations on how low one can drive the exhaust temperatures. While there is no problem with extracting all the energy down to very near ambient from the exhaust of both steam and diesel plants, the problems arise with what happens when they go up the steel lined stacks. When one sees that nice tall stack in a steam plant, few people realize that that is just window dressing. The real exhaust is a steel liner that fits inside that fancy shell. The plant is engineered (its exhaust gas temperature recovery mechanisms, both internal and external to the boiler) so that at minimum load, the exhaust leaving the top of the stack is above 212 degrees F. This ensures that sulfuric acid is unable to form and eat out the liner. Diesel exhaust is kept above that temperature for the same reason.

A supercritical boiler is one that has a pressure of 3200 lbs/sq in or higher measured at the outlet of the boiler. It must in fact be run at least several hundred pounds higher in order to prevent phase changes due to losses in the piping and valves. The main advantage of these types of boilers is the high heat transfer rates and resultant efficiencies that are possible. 2000 lbs is a common pressure in modern boilers. Special and more expensive metallurgical considerations must be taken into account if pressure is run much above that although some utilities feel the additional efficiency is worth the expense. I should add the caveat that is has been a fair number of decades since I was involved in that kind of stuff and it is probable that the metallurgy has evolved to the point where that expense involved are relatively minor.

The thing about a LFTR (Thorium powered), is that it is self regulating, based on the containment vessel design. You do have to heat it up to get it liquified to get it started tho...

dan92677 wrote:The thing about a LFTR (Thorium powered), is that it is self regulating, based on the containment vessel design. You do have to heat it up to get it liquified to get it started tho...

And the problem is that it needs a particle beam accelerator to generate neutrons to make it run - no electricity remember?

Dutch46 wrote:Air Tech wrote:
"Efficiency can be judged by the temperature of the exhaust against the combustion temperature of the fuel and diesels have a much higher exhaust temperature than an efficient boiler. Other tweaks include running a Kalina cycle in the boiler to drop the steam exhaust closer to ambient by running a mixture of water and ammonia (which obviously requires a closed circuit condenser), higher steam pressures (2000psi super-critical with air and water preheaters, superheater and inter-stage reheaters to extract the maximum heat from the flue gas) and the use of a turbine power plant (although a 4 stage piston engine comes close). (Kalina cycle systems also are faster to bring on line due to the higher pressures of the ammonia)."

While it is true that efficiency may be judged by the exhaust temperature, there are technical limitations on how low one can drive the exhaust temperatures. While there is no problem with extracting all the energy down to very near ambient from the exhaust of both steam and diesel plants, the problems arise with what happens when they go up the steel lined stacks. When one sees that nice tall stack in a steam plant, few people realize that that is just window dressing. The real exhaust is a steel liner that fits inside that fancy shell. The plant is engineered (its exhaust gas temperature recovery mechanisms, both internal and external to the boiler) so that at minimum load, the exhaust leaving the top of the stack is above 212 degrees F. This ensures that sulfuric acid is unable to form and eat out the liner. Diesel exhaust is kept above that temperature for the same reason.

A supercritical boiler is one that has a pressure of 3200 lbs/sq in or higher measured at the outlet of the boiler. It must in fact be run at least several hundred pounds higher in order to prevent phase changes due to losses in the piping and valves. The main advantage of these types of boilers is the high heat transfer rates and resultant efficiencies that are possible. 2000 lbs is a common pressure in modern boilers. Special and more expensive metallurgical considerations must be taken into account if pressure is run much above that although some utilities feel the additional efficiency is worth the expense. I should add the caveat that is has been a fair number of decades since I was involved in that kind of stuff and it is probable that the metallurgy has evolved to the point where that expense involved are relatively minor.

You only need to be above 212F if you are running a boiler with crappy high sulfur coal and no acid scrubber (like most American and other third world coal fired plants). Most of the civilized world has scrubbers and dust collectors on their large boilers and exhaust temperatures of 120F are common (as are stainless steel stack liners). No sulfur in the exhaust gas saves a lot of hassle....(lower inlet temperatures in the scrubber make life easier for the scrubber too).
Most multistage generators have steam superheaters on the inlets (to ensure dry steam) and between each turbine stage (for the same reason) as for peak efficency you want the steam to be almost condensing at the exhaust pressure of each stage. (I've designed and commissioned the controls on a number of coal fired power plants...)

AirTech wrote:(SNIP)

A bigger issue is fuel availability, with no fossil fuel oil production infrastructure in existence, I doubt anyone could organize the thousand tons of fuel oil needed for an ocean crossing, and any number of coal mines would have that level of inventory on hand.

(SNIP)

I'll just chip in here, as this is the biggest point in the arguement so far.


Personally I believe that once the OBS is out of the way, diesel is definitely the way to go.

Until then, steam is really the only option, both because of the OBS, and because coal is that much more readily available.


At this point in time, fire vine/petroleum oil production is almost certainly small scale, limited to a few tons per week. Conversely, coal production has increased dramatically in the past few years (mainly due to the increase industrialisation of Charis), and so coal is available by the thousands of tons.

Based on this alone, coal fired steam engines are the only realistic option.

MWadwell wrote:Until then, steam is really the only option, both because of the OBS, and because coal is that much more readily available.


At this point in time, fire vine/petroleum oil production is almost certainly small scale, limited to a few tons per week.

Why can't Petroleum/bio-fuels production be stepped up the same way Coal has been? The high-pressure triple expansion engines Charis is building can't be lubricated with tallow lard, and Kraken oil alone. So production of some source of lubricants is going to have to be ramped up whether Diesels are developed or not.

Coal is one of the "hidden costs" of Steam; it takes more manpower to extract from the ground than oil; all but the very best grades require exhaust scrubbers to prevent acid rain and smog; etc.

"Clean Coal" is a PR myth perpetrated by the Coal Industry and Safehold has more options than the real world for alternative fuels for steam engines. Every fuel option for Diesel can be applied to Steam plus a few that can't be applied to ICEs.

"Clean Oil" is pretty much an oxymoron as well. Except for large installations that can afford the mass penalties of efficient exhaust scrubbers, fossil fuels of any type produce the same acid rain and smog problems that hamper Coal use.

Safehold has the opportunity to build an infrastructure that bypasses the worst pollution excesses of the industrial revolution, and I don't see any reason they wouldn't do so with the historical lessens available through Merlin and OWL.

dan92677 wrote:The thing about a LFTR (Thorium powered), is that it is self regulating, based on the containment vessel design. You do have to heat it up to get it liquified to get it started tho...

One must still be able to regulate the power level of the reactor. The best means to do that differ for different reactor sizes. Just dumping the moderator into a pool of neutron poison is not desirable unless it is an emergency because in order to get a restart, enough of the poison to get to criticality must be removed and that is a lengthy and expensive process even if the poison can be recovered and reused.

Weird Harold wrote:Why can't Petroleum/bio-fuels production be stepped up the same way Coal has been? The high-pressure triple expansion engines Charis is building can't be lubricated with tallow lard, and Kraken oil alone. So production of some source of lubricants is going to have to be ramped up whether Diesels are developed or not.

Coal is one of the "hidden costs" of Steam; it takes more manpower to extract from the ground than oil; all but the very best grades require exhaust scrubbers to prevent acid rain and smog; etc.

"Clean Coal" is a PR myth perpetrated by the Coal Industry and Safehold has more options than the real world for alternative fuels for steam engines. Every fuel option for Diesel can be applied to Steam plus a few that can't be applied to ICEs.

"Clean Oil" is pretty much an oxymoron as well. Except for large installations that can afford the mass penalties of efficient exhaust scrubbers, fossil fuels of any type produce the same acid rain and smog problems that hamper Coal use.

Safehold has the opportunity to build an infrastructure that bypasses the worst pollution excesses of the industrial revolution, and I don't see any reason they wouldn't do so with the historical lessens available through Merlin and OWL.

Charis is likely increasing its production of oils and lubricants. I believe that the main error that will not be repeated is the historic dumping of gasoline in rivers because there was no market for it (jump straight to catalytic cracking and reformulation). Kraken oil is currently used for illumination and lubrication, but once "rock oil" distillation reaches commercial through put, it will rapidly cease to be used.

As for the problems with sulpher is oil, remember that there is little to no sulpher in Gasoline, and only small amounts in the diesel you buy at gas stations. Ships and power plants use a very heavy grade of sludge that contains a lot of sulpher and needs to be preheated to be burned. http://en.wikipedia.org/wiki/Fuel_oil