Can silica gel provide wick effect to burn waste oil/Bunker C oil?

cowdog

Silica gel is the most absorbent inert material, being able to absorb liquid 20% of its own weight. It is used as "crystal cat litter".

Silica gel also has a large surface area -- around 800 m2/g.

If we drip oil onto red hot silica gel, it will be absorbed onto silica gel's surface. 800m2/g surface area, means 160m2/g surface area for the oil to attach to, which translate to equivalent droplet size of 15nm.

I know this cannot directly compare with sprayed oil fog, but even if the tradeoff of effective surface area is 1/100, the oil/silica gel surface is still equivalent to 1.5um droplets, which is pretty good even for diesel engines.

Silica gel bead are not clumping and could pass air around them. As cat litter, once dirty, they can be regenerated by high temperature oxidative atmosphere, such as lean propane flame.

So, I know dogs don't give a damn, but can we really use red hot silica gel bed as oil burner?

Jamie Hall

I suppose... for a small enough burner... but you have to get the oil onto it in the first place... so... um... why not spray it to begin with? And burn the mist directly?

I might point out, too, that emissions controls for any of the heavy oils are difficult. A big power boiler, the expense is manageable. Marine diesels aren't too bad -- but there is a good reason they switch to lighter grades (distillate marine gas oil or diesel) for maneuvering or close to shore.

cowdog

Jamie Hall said:

you have to get the oil onto it in the first place... so... um... why not spray it to begin with? And burn the mist directly?

Because it requires high pressure fuel pump and spray nozzle, both of which are expensive, the nozzle is prone to clogging, especially with waste oil and residual oil.

A low pressure fuel pump and a drip tube is much easier.

Emission is a separate issue though. Right now DPF is the standard solution, but being fixed installation, we might be able to utilize bulkier filter structures that have unclogging built in, such as building in some internal pipelines for pressure washing.

If we can build EPA wood stoves, there is no reason we cannot build EPA heavy oil stoves.

retiredguy

My question to you is, "Just what type of fuel oil are you asking about", waste oil or bunker C. Bunker C oil or #6 oil as it is commonly called, must be heated to get it to drip or be pumped through a pipe. #6 oil at room temperature is almost as thick as roofing tar. Burning #6 oil would not be recommended for anything less than a commercial or industrial setting. Waste oil, depending on the type, could possibly be burnt in a typical heating unit with certain added changes to the system. Using any of these products in a home would probably be a "fools errand". I have never had any experience with a wick type heater and I don't think that waste oil or #6 could be used in a wick type heater. My 2 cents.

cowdog

retiredguy said:

My question to you is, "Just what type of fuel oil are you asking about", waste oil or bunker C. Bunker C oil or #6 oil as it is commonly called, must be heated to get it to drip or be pumped through a pipe. #6 oil at room temperature is almost as thick as roofing tar. Burning #6 oil would not be recommended for anything less than a commercial or industrial setting. Waste oil, depending on the type, could possibly be burnt in a typical heating unit with certain added changes to the system. Using any of these products in a home would probably be a "fools errand". I have never had any experience with a wick type heater and I don't think that waste oil or #6 could be used in a wick type heater. My 2 cents.

Think of candles made of paraffin, which is thicker than tar in room temperature, but still combustible with a consumable wick.

I believe if a boiler could use bunker C and waste oil, it can use pretty much anything. I listed Bunker C and waste oil to emphasize on the "compatibility" factor.

I have tried using a wick to combust waste motor oil, it only works with a floating plug (the flame must be nearby the motor oil-air interface, cannot lift the WMO high like kerosene in a wick-type heater.

You can drip oil to keep the oil-air interface always on the top. I guess a pump and an electric throttle valve is a bit over the cheap wick-type heater's sales price though.

Jamie Hall

"If we can build EPA wood stoves, there is no reason we cannot build EPA heavy oil stoves."

As I used to say to my students, if you give an engineer enough money he can design and build you anything you want. And this is true of the above quote. Leaving out the little problems associated with moving heavy oil around, which @retiredguy just commented on, you have then the problem of just what kind of pollution are you trying to control? Wood stoves are easy to manage. It's mostly a matter of making sure that combustion is always or at least almost always reasonably complete, even when the person firing the stove mishandles it -- which they will, guaranteed. Heavy oil is another matter altogether, and the associated scrubbers, condensers, and filters -- while completely do able -- require maintenance and capital cost -- and bulk.

There is a very good reason that the marine industry is shifting away from using heavy oils in diesels and steam power plants. It costs too much to meet the emission requirements, plain and simple.

If I may ask, @cowdog , what problem or problems are you trying to solve? You have listed an interesting array of potential solutions to things, but what is it you are actually trying to do?

cowdog

Jamie Hall said:

If I may ask, @cowdog , what problem or problems are you trying to solve? You have listed an interesting array of potential solutions to things, but what is it you are actually trying to do?

Thank you for asking, I believe there is much potential of biomass pyrolysis oil to replace propane and No.2 heating oil, and probably also transportation fuel (see drive on wood forum), from recent progresses in small to medium scale pyrolysis (yes, because biomass is scattered in nature).

Especially in rural areas without natural gas service.

The technology to make biomass oil is there, there is federal renewable fuel credit to help with costs, the only roadblock is how to use it. I am looking for solutions that can burn a broad spectrum of liquid fuel with high thermal efficiency.

Jamie Hall

Certainly a worthy endeavour. The problem, though, as has sort of been mentioned here and there in various comments in this and your other thread, is that the fuel -- as it might be pyrolysis oil -- and the equipment in which it is burned are parts of the same system. As a general rule, the equipment -- particularly more recent equipment -- and the fuel to be used in it are closely matched to each other, with the result that the fuel requirements are surprisingly stringent. As an example from the transportation field, carburetted engines can be adapted to run on pretty much any liquid fuel, provided it is already vapour (e.g. propane) or vapourizes at the temperatures expected in the engine (which, for gasoline for example, means the atmospheric vapour temperature must be below around -20 F). The only other condition is the tendency of some fuels to preignition; to utilize them the compression ratio of the engine must be reduced. During World War II -- which, I dare say, you are too young to remember -- the use of fuel from wood pyrolysis was quite common in parts of Europe for motor vehicles. It didn't work awfully well -- as you note, the energy content is low with a reduction in power output, and there were many problems with coking and so on in engines -- but it was better than nothing. The Germans, at the same time, developed processes to utilize fuels derived from the pyrolysis of coal. After considerable refining, this gave fuels which could be used in aircraft engines, though again with much lower power than corresponding petroleum based fuels (somewhat to the detriment of the Luftwaffe, but that's another story).

So for transportation, the use of pyrolysis derived fuels is not new. It is interesting however that even with the prowess of the German chemical industry, and the exigencies of war, it was never possible to develop a fuel and the engines to run on it which were the equal of petroleum based fuels.

In the early days of gas turbines -- say the '50s -- considerable effort was put into designing and building gas turbines which had high power output and which could use heavy oils such as #6 or Bunker C. So far as I know, these efforts did not extend to using pyrolysis derived fuels. In any event these efforts were abandoned due primarily to difficulties in getting consistently clean enough combustion to avoid coking on the turbine blades; fuel handling was not an issue as these units were designed to start and initially run on light oils (primarily #2 diesel or the corresponding JP4) which provided enough excess heat to warm the heavy oil to the point where it was pumpable. One outstandingly successful aircraft engine (a modified Pratt & Whitney afterburning J58) was developed which ran on JP7, a slightly more viscous equivalent of JP4 but with much higher vapour temperatures and flash point. Unfortunately, starting this engine required the use of a very toxic borane starter fuel -- and a whopping total of 800 horsepower starter motors (two Buick 401 nailhead V8s, for the curious). This is hardly practical for routine use, however.

For domestic use of pyrolysis oil in place of propane, the two fundamental problems are getting the vapour pressure high enough at the coldest temperatures likely to be found (this is a problem already, of course, with using LP in cold temperature settings) and the lower energy content. The latter problem can be addressed by refitting all the equipment to burn roughly twice as much fuel; a somewhat significant undertaking, but one which, in principle, is manageable. The vapour pressure problem, however, is somewhat intractable, since that is related to the chemical makeup of the fuel. Preheating is a solution to that, of course, but presumes that there an energy source available to accomplish the preheating. That is also feasible -- again -- with such expedients as a liquid fuel fired preheater, but one is beginning to get into complications which are well beyond any commercial practicality. Using it as a direct replacement for #2 diesel is actually a little more practical, as all that is required is a complete replacement of the existing oil burner and the addition of suitable equipment to ensure adequate fuel storage and handling.

There is also the problem of availability of enough wood. If we presume that roughly 50% of the heat content of the wood is recoverable in pyrolysis oil, then very roughly for each 200 gallons of diesel you will need a cord of good quality high grade hardwood. As has been noted, with good management you can expect to get a cord of wood per acre as a fuel wood crop. A residence burning 1,000 gallons of oil a year -- not an unreasonable amount -- would need a 5 acre would lot to support it -- and the time and effort on someone's part to harvest and process that wood. Or another view, a gas station processing a reasonable 5,000 gallons per day would need to be supported by a 10,000 acre wood lot.

Even in rural areas, this kind of acreage is simply not available. It is, for a small scale operation -- homesteading, perhaps, in a remote area, or a determined (and young) alternative life style practitioner, but on any reasonable scale? Hmm... never mind, of course, the environmental impact of logging on that scale...

cowdog

Jamie Hall said:

carburetted engines can be adapted to run on pretty much any liquid fuel,

Actual carburetors are PITA to accommodate a different fuel, because they are intertwined with vacuum pressure (which changes over throttle and rpm), viscosity, boiling point etc. Intake port injection or cylinder direct injection engines are easier to modify for new fuel because you only need to design the injection system instead of considering the engine as a whole.

If it atomizes outside the engine, it will atomize inside the engine.

I am aware that biomass pyrolysis oil cannot replace all fossil fuel, but currently there are much biomass that is just left to rot in the field and forest. Harvesting them has low impact to the environment, and even reduces fuel of wild fires. Even replacing 5% of all fossil use generates much revenue for rural America (and pulls federal subsidy from big oil companies to rural families)

Jamie Hall

Most of us rural folk plow the biomass from, say, corn back into the field. It's better for the soil. And tops and the like from lumbering are great for habitat and regeneration of timber -- particularly hard woods. The fire hazard from a professionally lumbered area is minor compared with unmaintained forests -- as California is finding out the hard way.

And about the last thing we want is Federal subsidies, which come with strings and rules devised by people whose closest contact to nature and timber and agriculture is their lawns and Lowe's...

cowdog

Jamie Hall said:

Most of us rural folk plow the biomass from, say, corn back into the field. It's better for the soil

better for the soil and also better for the worms. Piling up the stalk (for feed or fuel) and burning the roots eliminate the worms. The stalk is good biomass.

Jamie Hall said:

their lawns and Lowe's...

Urban landscape waste is an important , year round source of biomass. Also, paper and food waste in the municipal solid waste are biogenic, they can also be processed into biomass oil.