Can we burn HFO sludge residues? 4

[MineAutomat]

Good day,

I am leading a project which will convert our existing power plant from running on diesel fuel to run on heavy fuel oil. Hence, we will install a complete HFO treatment plant.

There is a bauxite plant operation near our power station that also burn HFO in their kilns.

I am curious to know if they would be able to burn the HFO sludge we will produce from our HFO treatment ? I have read about certain operations that burn their waste oils... it got me thinking about our sludge.

Any insight will be appreciated.

Sophie Dufresne

 

[orenda1168]

Sophie:

How about a description of your HFO treatment plant so we can better judge the quantity, quality and content of the residual sludge, and whether or not it is consumable in a kiln operation.


Orenda

 

[MineAutomat]

Of course!

Our HFO is currently specified to have a density of 993g/l, viscosity between 636-680 cst@ 50oC. We plan on heating it up in the storage tank to be at 380 cSt for entry in the treatment plant (which is also the requirement from our equipment suppliers).

The fuel will be transfered to a 'buffer tank' supplied with heater. From there to the seperator unit which will clean the fuel of water and sediments.

The fuel then moves on to a 'day tank' and is fed to our engines via a heated booster and feeder unit. We are designing the system to 7300kg/hr of HFO, which would yield 146 kg/hr of sludge (2% of total HFO).

From the seperator mentioned, we collect the sludge and transfer it to tanks. We have the option to use an incinerator or not.

Also, there are filters throughout the process to catch particles. Our HFO supplier also specified Ash content of less than 0.05%, Ashphaltene less than 12%, 1% of Water, Sodium less than 100mg/kg, Vanadium less than 150mg/kg and sulfur less than 1%.

Would you like more details? I'd be happy to add more.

Sophie

 

[orenda1168]

Sophie:

Several observations.........

1) The recovered sludge will have a high water content, probably mostly emulsified and with a significant solids loading. Even with this, disposal via a kiln operation is commonly done when available, as these units can burn amazingly poor quality fuel if there is no issue of kilned product contamination.

2) The bauxite plant kiln may or may not have a spec for water/solids/BTU in their fuel.....assuming they do, they may still be able at some level to proportion in the sludge from your operation to their fuel handling system, although the BTU benefit from the sludge will be minimal.

3) Question....I assume from your comment about "engines" that you are running diesels. Are these slow or medium speed, and what are the engine fuel specs for sodium/vanadium? At the fuel spec maximum loading of 150 mg/kg of vanadium, a potential exists for valve deposits and corrosion, even though the sodium content should be low in the fired fuel.

Orenda

 

[MineAutomat]

Orenda,

Good tips. I will need to check with the operations folks at the bauxite plant with regards to fuel specs.

As far as the diesel engines specs for vanadium content. I will look into that also. They are medium speed.

A CIMAC recommendation did point to what you suggest with regards to corrosion/deposits. It is all in the sodium/vanadium ratio.

OK so I need to do some homework; also double-check if we deal with the sodium in the seperation phase.

Thank you for your insights.

 

[orenda1168]

Sophie:

It's fair to assume that your HFO treatment system will reduce the sodium content....the key insofar as engine valve deposition and burning is concerned is to get it low enough to minimize low-melting eutectic deposit formation. Be aware that medium speed engines, because of their higher internal metal temperature regimes (than low speed engines), are more subject to deposit formation and corrosion

Even with fairly low sodium levels, you may want to consider injection of a magnesium-based additive, probably best as an oil-soluble magnesium carboxylate (or similar), to mitigate formation of any corrosive deposits.

I have some fifteen years of HFO pre-treatment, additive treatment and combustion experience in marine and land-based diesel and steam boiler systems, and will be happy to give you any assistance desired or required.



Orenda

 

[MineAutomat]

Orenda,

Actually I have a printed copy of your post dated Sept 05 related to the use of magnesium! I was reasearching this just last week.

Thank you for your comments and I will surely need some assistance as we are moving along this project. I have an electrical background, therefore, bunker treatment is a nice challenge for me!

 

[taylorg]

Sophie,

A couple more questions regarding the interesting fuel that you want to use...

1) Can you tell us the conradson carbon residue, aluminium + silicon content, pour point and also the total sediment potential so that we have a full picture?

2) What make/model of engines do you have and are they old?

3) Have you given the fuel spec to the engine manufacturer and asked for their opinion and maximum limits on the various constituents?

Your fuel appears to be real bottom end stuff and so you really need to know the level of catalyst fines (al + si) that you may have to deal with. High levels will cause rapid abrasive wear of your pumps, injectors, rings and liners. Modern engines can deal with a combined value of Al+Si of about 80mg/kg.

At 100mg/kg the sodium level is about double what it needs to be, but good centrifuging should reduce it. A high level of sodium on its own will give rise to post-combustion deposits in the turbochargers rather than valve corrosion, and this can usually be removed by regular water washing.

Your vanadium level on its own is acceptable (modern medium speeds can take about 600 mg/kg), but it is essential to keep your exhaust valve temperatures below the level at which sticky low melting vanadium/sodium salts are formed. If you have an old engine without nimonic/stellite valves etc. a ratio of 3:1 (vanadium to sodium) is key as this is the ratio which causes the salt formation at lower temperatures. Based on this ratio your worst case scenario is a sodium content of about 30mg/kg.
It's extremely rare to come across a plant where the economics of injecting magnesium additives make it worthwile to use the fuel, and I would be extremely interested to hear some rough order costs from Orenda if you are able to provide?

Getting back to your original question...
You have a few options for getting rid of the sludge:

1) pay someone to take it away (expensive!)
2) install a small incinerator (many remote plants do this)
3) see if someone local can use it (i.e. your bauxite friends)
4) install a small treatment plant to recover 1-1.5% of the waste oil. This is becoming popular and environmentally friendly (started in the shipping world)

The option to go for is really one of economics. You don't produce vast quantites of sludge but if the bauxite plant wants to buy it then great! If not then go for the next least cost option.

Also, you are going to have to keep this fuel hot - will you be installing steam/electric heating?

The actual conversion of your engines is a whole topic in itself but I need to get back to work now...
Good luck and please do keep us up to date with your interesting project!

 

[MineAutomat]

Hi taylorg

Thanks for the reply. To answer your questions...

1) The Concarbon should be less than 15%(Wt), the Al+Si should be less than 80 mg/Kg and the pour point should be less than 41oF. Now, all these data point are given to me from the contract we have with the supplier. No data for the sediments.

I do have a report from the last 6 shipments of bunker to our port. From the 9 points tested for each batch, I know that the % of sediments (by extraction) has been less than 0.03%, all pour points are less than 32oF. There are no tests for catalyst fines, concarbon, sodium, ash or asphaltenes. I am not sure why they are not all tested for each batch (long sampling time? availability of testing tools? I have really no idea)

Just for your information too, the viscosity varied from 430 to 613 cSt @50oC. So as I read from this post, this is expected to vary.

2) The engines we have are Wartsila 9R32s, rated 3MWe. They all have more than 70,000 hours of operation; they were purchased new in 1992. The 3:1 ratio is also suggested by CIMAC for fuel quality.

3) I am working with Wartsila on this project and they have the fuel specs with them. We have not yet been talking about the fuel specs, as we have not started the detailed engineering yet. But I have my list of questions ready!

For the bunker heating, we are thinking of going with thermal fluid. Any experience with this?

I also need to pursue my work. I will be looking forward to your insights as well.

 

[jmw]

A number of diesel engine power plants are now converting to HFO due to cost which is catching some of the major oil companies off-guard and they are concerned how they will meet the changing marine industry demands for low sulphur HFO without a further call on the stocks from land based power plant.

HFO has a reputation for quality problems and it may be a good idea to take a hint from the marine industry and have all fuels sampled and analysed by the test houses such as Viswalab, DNV PS, SGS etc. A search on the internet should locate a test house convenient to you. The costs are not great but you may find that it takes a day or two to have the results back.

You may also wish to invest in a test kit for on site testing. (e.g. from Kittiwake)
The IBIA (International Bunker Industries Association) website has a guide on fuel quality and on sampling which may provide a benchmark for you, or you could approach companies such as Kittiwake or Jiskoot for drip samplers.

Visit

http://www.IBIA.net

for details of the tests conducted though Viswalab also maintain similar information on their website.
In fact, any of the marine fuels websites may prove a valuable resource. Also vist the CIMAC site for comments on the new fuel standards (ISO 8217 has just been re-released with much tighter controls over some parameters in an attempt to control the use of HFO as a dumping gorund for used lubricating oils, etc. and to account for the new marine sulphur legislation.)

The problem with HFO is to know what quality the fuel is when received.... what standard do you expect? ISO 8217? have you agreed to use a specific standard or are you negotiating a set of quality parameters with the supplier?

How consistenmt will they be and how will this change as the new demands for low sulphur fuel develop over the next few months as the first marine SECA becomes active?

Even before the new ISO standards and the new sulphur limits, one test house reports that 14% of fuel samples analysed are off spec according to the standard.

This doesn't account for sulphur.
Most HFO is usually below 4.5% sulphur but with the new marine legislation which requires only fuels with less than 1.5% sulphur are burned in SECAs (the Baltic in MAY and the North Sea soon, but with California enacting its own legislation) the demand for low sulphur fuel is going to add a premium to the current prices and no one is sure what that premium will be nor how well the suppliers will manage to meet demand.

I assume you are using a viscometer to control the fuel heaters, you may wish to use one to check fuel as it is received as this may be the only clue you have as to the quality during delivery. Alternatively you may wish to quarantine new fuels until they have been tested before using them.





JMW

http://www.ViscoAnalyser.com

 

[MineAutomat]

JMW,

There is a lab facility close to our power plant that can test most parameters in fuel; I asked them to look into finding the tools to be able to test them all. So we may be able to analyse all parameters within close proximity of the bunker delivery.

The contract we have with the fuel supplier was written over a year ago. If I look at the specs they are within the CIMAC fuel quality recommendation except for water (0.5% higher than CIMAC recommends) and the vanadium/sodium ratio. I am personally not aware the terms of this contract as this is handled in Guyana but I will certainly take a look into it.

We are using a viscometer to control heating and I was planning to order one at the entry point before our storage tanks.

Now I have 2 questions:

1) if fuel treatment equipment suppliers quote prices based on the fuel being at 380 cSt, can I simply ensure that it is at 380 cSt before it is delivered to them? (i.e. since our fuel is between 415-633 cSt I can heat it to reach 380 cSt)
I am wondering if the 380 cSt is the fuel 'qualifier' e.g. CIMAC G380, CIMAC H380 etc.

2) How can I find out what type of fuel I have? (aside from calling my supplier) Is there a way for me to find out?

Sophie

 

[jmw]

Sophie,
I think water content was just reduced in the ISO standard so your contract may have been based on the earlier standards, if on ISO 8217.

Your questions:
Fuel treatment suppliers specification:
It depends on who is supplying your fuel treatment system and what specification was given to them.

The objective isn't to heat the fuel to 380cst but to heat the fuel to the optimum viscosity for injection e.g. 11cst or 12 cst or something like this.

Modern engines rated for 380cst fuels are usually able to handle 500cst fuels without any problems because the fuel heaters are sized with sufficient capacity to raise the fuel temperatiure from the 140degC a 380cst needs to 150degC a 500cst fuel needs to reach the same injecttion viscosity.

However, if the fuel needs addittional heating because its viscosity is even higher, the problem may not be with the fuel heaters but the engine.
It is important not to heat the fuel to a temperature beyond the engines maximum limit. For some engines this is 150degC.
Others will handle higher temperatures.

So:
[ul][li] do the heaters have the design capacity to heat the fuel sufficiently to maintain the optimum viscosity (which in your case is what? 11cst 12cst?)even under worst case conditions i.e the fuel is out of spec or can you reject out off spec fuels during receiving?[/li]
[li] what is the maximum fuel temperature the engine is rated for?[/li]
[li]What is the expected quality variation in the fuel you are using?[/li][/ul]

What type of fuel do you have?
This link will take you to some current fuel specs:

https://www.fammllc.com/famm/publications/Comparison of ISO 8211.htm

you might be able to match your suppliers spec against the standards though in most cases the values quoted are maximum limits. A lot depends on who arranged the contract and if they made any concessions and why and what provisions they made to handle those concessions.

This link

http://www.viswalab.com/knowledgebase.htm

will demonstrate the normal tests performed.
These are no guarantee of quality just that the fuel complies with the standard.

Fuels can become contaminated such that forensic analysis is required to identify the problem.
Contamination can include simply adding water, adding waste chemicals, used lubricating oils etc.
Much can happen between the refinery and the engine. The supplier may, with justification, declare the fuel was fine when it left the site. It sounds as if your fuel is leaving a refinery and has a journey to reach you? if so the chances are that somewhere on route strange things may happen, if not now then in the future.

Many problems with fuels are not revealed by the sample analysis. You can see them illustrated at

http://www.viscoanalyser.com/badbunkers.html

Your plan to test the fuels as they are received is a very good one, be sure to chose the best instrument for the job, one that leaves no room for discussion.
You need for this instrument to measure the base kinematic viscosity (cst at 50degC) and for security you ought also to measure the density at 15degC. Niether are difficult measurements to make these days.
I would suggest that as each shipment is in transit you obtain a fuel analysis that you can test the fuel against as it is being unloaded. This not only tells you the fuel is to specification, it also tells you if this is the specific fuel that was shipped and if it has been adulterated. Density and viscosity will both vary if the fuel quality has changed and while it is relatively easy to manipulate one of these parameters, manipulating both is very difficult.

JMW

http://www.ViscoAnalyser.com

 

[MineAutomat]

Thank you JMW,
I know the viscosity at the engine needs to be at 19 cSt according to the manufacturer. With the viscosity-temp graph I have, this means heating between 125C-140C depending if my fuel is a 380 cSt or a 700 cSt.

Now I need to research more your other points as I do not know them off hand.

The links provided are very uselful. As always, your posts are informative and professional. Everyone's input has been quite helpful actually, I appreciate that!

Sophie

 

[taylorg]

Sophie,

If Wartsila will be carrying out the design and conversion then I wouldn't worry too much about the heater capacity and viscosity design issues etc. as this is 'bread & butter' stuff to them.

You mentioned thermal fluid for heating in an earlier post. This has been used quite successfully in many plants but is favoured more by Wartsila's rivals at MAN B&W and BWSC. I would be happy to use it.

The key thing to remember in your fuel deliveries is 'representitive sampling'. A quick google search will give you the details on this, as will jmw's useful links above.

I have been involved in the conversion of a few Wartsila plants (mainly the 32-series) to HFO and gas in the last few years, and my main advice to you doesn't actually relate to the design side of things, but the contractual:

Don't accept a 1-page contract which simply says "we will convert your engines for $xx". It should clearly specify:

1) full details of the work which they will carry out;
2) guarantee on time for conversion;
3) guarantees on the post-conversion performance, i.e. output, heat rate and lube oil consumption and the ambient conditions and fuel analysis to which they are linked;
4) full details of the performance testing to be carried out after the conversion (procedures, durations, method of correction of results to guarantee conditions etc);
5) Your rights to reject the work. Normally you can specify liquidated damages for a shortfall in ouput/heart rate figures up to 5%. Any more than 5% and you should retain the right to reject the plant.

Just before the performance tests you should take 3 fuel samples from the sevice tank. Give one to Wartsila for them to test, get one tested yourself, and keep the 3rd in case of any dispute.

As your fuel supply agreement seems to be in place already I assume you have similar guarantees in there for fuel spec guarantees, tolerances, criteria for rejection etc?

Having a tight contract in place doesn't just protect you if things go wrong, it will help to ensure that the contractor designs the plant properly in the first place. If you sign a weak contract any prudent contractor will seek to exploit it for its own benefit.

Finally for today, I would say your fuel spec looks to be Venezuelan HFO and closely resembles Grade RMK-700 of ISO-8217 (2005). Be careful with the density - modern centrifuges start struggling over about 1000kg/m3.
By the way you can buy good fuel test kits for power plants - always useful for doing your own on-site checks.

If you want some bed time reading try "A Practical Guide to Marine Fuel Oil Handling" (IMarEST MEP Series Vol 3 Part 19, ISBN: 0-907206-94-8) - great book!

Regards
taylorg

 

[jmw]

Glad to be of help.

One last link:

http://www.viscoanalyser.com/xls.html

The ASTM D341.xls spreadsheet may be useful to you but note that it is populated with the original CIMAC data.
According to this your viscosity of 19cst is achieved at 130degC if the base viscosity is 680 and 120degC for a 380/390cst oil.

The actual curve for your oil is not there, but if the viscosity is 680 at 50degC, I just itterate the viscosity at 100degC till I get good A & B values i.e. intermediate between those for a K45 and an H55 oil or about 49.3cst at 100degC as an approximation.

It may be a good idea, when obtaining fuel sample analyses, to request both the 50 and 100degC viscosities as this is invaluable in determining the injection temperatures.

PS. If you are investing in off line viscometers for spot sample testing, I would suggest a Stabinger viscometer.
This is very quick indeed and measurement is to ASTM D7042, equivalent to ASTM D445 but very fast.
I have no idea of the price compared to a falling ball type (of the sort usually used for plant measurement of fuel viscosity) but a lot less than a capillary for ASTM D445 I would guess.

If you are going to spend some money, spend it now while the change from diesel to HFO represents a significant potential cost saving.
It's funny how accountants minds adapt so quickly to a new order of costs; once you are running on HFO the term "savings" will be long gone from their vocabulary and with it, any chance of further expenditure.

JMW

http://www.ViscoAnalyser.com

 

[MineAutomat]

Great input! Especially your point on contractual agreement taylorg. I had not thought of that. I will let you know how things work out after our meeting.

JMW, the spreadsheet is great. I did have it already, along with the density one. I think you have posted that link on another thread so I looked at it.

I will research the Stabinger viscometer you mentioned as well.

Sophie

 

[MineAutomat]

Taylorg, I was thinking, as I am perusing over your last post, about the specifications of our contract.

I guess from your experience you have had exposure to this and I can't help but wonder if you did go through rough conversion projects. Would you be able to share some of that with me? I do not know if it would be suitable on this forum? Would it be un-professional?

I have also seeked help on the contractual agreement, as we are in this phase, but your insight would add some weight I am certain.

 

[0707]

“The quality of the various fuels in the market is changing, one reason being the increasing demand for low-sulphur fuel, generated by environmental protection restrictions, which increasingly limit the use of normal fuel types.

The most frequently discussed issues on fuel market in the last five years have been the dumping of polypropylene and the influence of the large amounts of waste organics which have been added to fuels. In addition, the engine design is also changing to meet the demand for higher power outputs, and thus the thermal condition in the combustion chamber changes as well.

In both situations, the issue concerns the dumping of waste in the fuel oil and, with regard to the polypropylene, fuel filter blocking was the main problem whereas organic waste can have an impact on the actual performance of the fuel pumps.”


“Heavy fuel oils require substantial preheating in order to be atomized properly. For example, No. 6 fuel oil normally has to be heated to the 225°F to 260°F range in order to obtain a viscosity of less than 200 SSU. Oils containing olefin hydrocarbons such as ethylene will have a tendency to polymerize and form gummy substances, which will detrimentally effect atomization. If excess preheat is applied the tar formed will harden in the fuel system causing maintenance problems. Care must be taken to maintain the proper preheat for a specific oil to prevent burner carbonization due to fuel polymerization.

The presence of sulfur, sodium and vanadium in heavy fuels can cause severe corrosion problems as well as pollutant emissions known as acid smuts. During the combustion process, sulfur is oxidized to sulfur dioxide (SO2). When high excess oxygen is present in the flame zone some SO2 will be converted to SO3, which leads to the formation of sulfuric acid (H2SO4). The dew point of sulfuric acid is around 270°F for most atmospheric conditions. Therefore, as a good rule, the stack exit temperature when firing oil should always be above 300°F to keep sulfuric acid attacks to a minimum.

Vanadium and sodium can cause metal attacks on lower temperature metal surfaces. Vanadium attacks are greatly enhanced in the presence of sodium (salts) and can occur at temperatures as low as 900°F. Vanadium, as low as 50 PPM, also can cause great harm to refractory.

The presence of asphaltenes in fuel oil causes increased particulate emissions and carbon carryover. Asphaltenes, which are heavy solid combustible substances (often containing some organic-metallic species) tend to be non-volatile, and therefore are hard to vaporize and burn. The presence of large amounts of asphaltenes will limit the minimum excess air levels at which burners can operate.”


In our power boilers and heaters we burn low sulphur fuel oil. We use magnesium-based additives with some benefits

Luis Marques

 

[jmw]

As Luis says,
fuel quality is changing and one reason is the low sulphur fuel requirement.

There is an advantage to this.
MARPOL Annex VI Regulation 18 requires the supplier to test and report the actual density at 15degC and the actual %mass sulphur.

That means that fuels supplied compliantwith MARPOL must have a valid analysis.
This is a change from ISO 8217 where compliance simply means certifying that the fuel is below certain limit values. This meant, for example, that several different batches of fuel were added into one storage tank and each batch was compliant, the assumption followed that any fuel drawn from that storage would thus be compliant. Sadlly not true. Too often fuels are not homogenised and stratification and separation can occur. One supplier advised that a top middle and bottom sample on 380cst storage revealed 150cst at the top and 450 cst at the bottom.

The advantage of MARPOL is that compliance can be tested because there is a specific analysis to test against.

The problem is that not all properties can be monitored online and this makes for problems in controlling quality.
Monitoring such fuel quality parameters as can be monitored, while fuel is being delivered, and comparing to a valid fuel analysis is invaluable.
I suggest that it is difficult to adulterate a fuel with impacting on either the density or the viscosity. One thing is for sure, if the fuel density and viscosity don't match the certificate, reject or quarantine the fuel until an analysis is received.
Yet to be proven though.

This doesn't protect against tramp contaminants...
Some problems, such as Polypropylen and ethylene are problems not normally tested for by the lab and need only be present in small quantities to be a problem (even a cumulative problem)
There are all sorts of adulterations and contaminations that can occur and a full spectrum of tests would be prohibitive. What happens instead is that when a serious problem emerges forensic testing is necessary to identify the cause and trace the source.

The new ISO 8217 does address issues such as adding used lubricating oil through limiting the contaminants that this brings to the fuel oil.

Anyone following the marine press and or te reports from the test houses (who issue bunker-alerts when offspec fuels are detected) will realise that the ingenuity of fraudulent suppliers has no bounds, and the potential for ethical suppliers to mess up is pretty wide ranging also.

The problem with HFO is both that it is both cheap and expensive at the same time: it is one of the cheapest fuels but bought in substantial quantities. The incentives for fraud are a major concern to legislators trying to limit environmental pollution, especially as low sulphur fuels will command a premium price which is really only guessed at so far (and some of the guess had neglected the potential of land based power generators swicthing to HFO because of the virtual doubling of fuel prices recently.)


JMW

http://www.ViscoAnalyser.com

 

[jmw]

This Article in Bunkerspot by Wanda Fabriek explains the new ISO 8217 fuels standard:

http://www.intertek-cb.com/newsitetest/news/documents/ISO8217released1Nov05.pdf

JMW

http://www.ViscoAnalyser.com