Help: Solution to heat bunker fuel tank 3

[lpfaustini]

Dear fellows,

I have a 19m DIA x 21m bunker fuel tank (HFO) and I need to heat it, but there are so many solutions that I myself got confused. Doing my research I found "suction heater" to be the most elegant choice, but is it economical worthy? Anyone has any suggestions or advice? What is the market trend? Thank you in advance!

 

[IFRs]

I see a lot of fin tube steam coils

 

[fegenbush]

I agree with IFRs that steam coils are quite common for this application. Is this a new or an existing tank? In what size nozzle do you plan to install this heater?

 

[lpfaustini]

Hi there!

It's a new tank. I intend to install it in a 24" NPS nozzle.

 

[LittleInch]

lpfaustini,

This is why you do concept studies and employ experienced design engineers to work out what is the most economic in your circumstances.

There are so many variables to this that no one can say with any certainty that a particular method is the right one for you.

such issues include:
New tank or old tank?
How many times a month / year do you need to heat it up?
Is the tank insulated?
Are there any other tanks close to you that need heating?
What temperature do you need to reach?
What level of redundancy do you need?
Is there any steam / hot water / waste heat in the near vicinity
How much does each fuel cost you (gas, diesel, electricity)?
What is the volume of your tank contents on average?
Do you have to heat it up within a certain amount of time or is it to "keep it warm"
Wha tis most important to you - CAPEX or OPEX?

I'm sure if I put my mind to it I could come up with several more issues which would impact the final most economic choice.

That's why you do a study looking at all the aspects and estimating the CAPEX and OPEX cost of all these items. There is no point normally in buying a low CAPEX heater, but then spending 3 x the cost on electricity than some other locally sourced fuel.


My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[lpfaustini]

Hi LittleInch,

Nice to talk with you. You're right: there are many variables to consider. That's why I'm here, as in Brazil the information is very hard to find. Wish I could "google" in portuguese and get what I'm looking for. Lucky me I did some english courses.

Here is what I found about HFO:

Bunker fuel needs to be heated at 40°C to achieve a certain viscosity and be pumped out of the tank. (Its pour point is 30°C). Keep the tank warm 24h/day is one solution, the other one is to heat only the portion that is going out (that's why I'm inclined to use a suction heater like this one). Local average temperature is about 28°C, minimum winter 16°C. Tank will be painted black, no insulation.

About the "heating element":

Steam: I could use a portion of the water from the fire protection tank to generate the steam to heat the tank. (note: fire protection tank is way over the design capacity).

Oil: The other idea is to use the same HFO that goes to the tank and send it to the boiler.

Am I getting the idea or am I absolutely wrong?

 

[LittleInch]

NO, you're starting to get there.

I can't quite make out the details, but what you seem to have is a glorified steam heater which can be inserted into a tank via an entry nozzle. This is typically what you would do if you needed to retrofit a heater rather than cut holes in the shell for new steam tubes.

It certainly looks like you need to heat the tank on a continuous basis to stop getting a tank of solid HFO.

How you keep the HFO hot in in the pipeline is another story but can be easily accomplished with insulated pipe and electric trace heating.

If this is a new tank then you have more options available, but if you need to build a steam plant / hot oil burner then you might want to look at electric heating.

I would also look very closely at the economics of insualting the floor and walls. This will significantly reduce your heating load and reduce CAPEX and OPEX of your system.

Is this just one tank?

There is no easy answer so you just need to come up with a few options and then cost the entire package with CAPEX and OPEX costs and try and talk to some operators about their experience of different heating types. Anything inside the tank becomes difficult and expensive to clean or maintain if it leaks or scales up, but is commonly the cheapest option although you need to consider where the steam or hot oil is going to come from if its only use is this tank.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[MJCronin]

LittleInch gives good advice... as always......

HFO is always cheaper than other forms of distillate....... MBAs therefore are attracted to it.

The MBA romance with this cheap fuel ends with the realization that significant CAPEX and OPEX must be considered in order to store and heat this nasty fuel. (Don't forget the cost of a boiler operator 24/7 if you decide to use steam)

As world oil prices decline, wouldn't an alternate fuel tank make more sense ?

Perhaps No. 2 fuel oil or Kerosene ?

MJCronin
Sr. Process Engineer

 

[lpfaustini]

MJCronin,

Unfortunately, this kind of power is not in my hands. I'm simply a mere mortal.

LittleInch, MJCronin,

Thanks, I got the information about CAPEX or OPEX, and the reply was: low CAPEX, high OPEX (in the first years).

 

[Duwe6]

low CAPEX = steam bayonet heaters bracketing the outlet nozzle.

Easy steam bayonet heater: 8"NPS pipe set thru a 12" Class 150 blind flange. Pipe sticks out about 1-foot and is flanged - 8NPS using a slip-on flange. The 8NPS blind flange is bored for a 2"NPS inner steam supply pipe.
8" bayonet extends about 2/3rds of the way across the diameter of the tank, and is closed with a pipe cap. Inner 2NPS inner pipe is the steam supply, and extends into the 8NPS bayonet to about 3-feet from the endcap. 2NPS pipe has a set of centering brackets welded to it to keep it from flopping around inside the bayonet. Put a 3/4 or 1NPS coupling in the bottom of the 8NPS pipe that sticks out about 1-ft, to allow the condensate to drain. While welding up this assembly, keep it level or slightly sloped to the outside of the tank. Build a support bracket for the bayonet, seal-welded to the tank floor. Support to be at least half-way along the bayonet, inward from the tank shell.

Extend your outlet nozzle about 6-ft into the tank [keeps nozzle's inlet away from cold tank walls]. Build two of the above bayonet assy's, and install them parallel to the extended nozzle, about 3-ft center-to-center, on either side of the outlet nozzle.

CHEAP -- all pipe and cheap pipe fittings; can be built by your second-team pipe crew. Hydrotest it at Full-Flange rating x 1.5; thus Class 150 = 420 psi // Class 300 = 1080 psi. All the welding problems will be revealed by that hydro; there may be defects & flaws in the welds, but if it passes a Full-Flange hydro the flaws are not "problems". how 'bout a star if you use this free engineering?

Later, think about insulating this tank, it'll save enough money to have a good Return on Investment.

 

[IFRs]

A single bayonet heater may not to do a good job. You'll need to do a heat balance to determine the steam or hot oil quality. You can still use a 20" nozzle to bring 2 or 3 steam lines in and 2 or 3 condensate lines out but why not just do it the traditional way with new shell nozzles, steam traps, sloped condensate lines, etc?

 

[LittleInch]

Low APEX, high OPEX to me implies electric heaters. You could rig up a simple pump and heater loop (probably two or three for a tank that size) out side the tank and run cables to you nearest (large) substation with low CAPEX, but then watch the electricity meter wiz round like it's about to take off..... If you need to build a steam boiler / hot oil heater then that will take time and money, but will be more efficient I the long run. Trace heating under decent insulation on the walls is another option.

If this a new tank I would install heating coils now or at least allow for the nozzles so you can easily retrofit when the electricity bill comes in. The piping is quite cheap - it's the boiler house and pumps that cost the money.

Only you can determine the most efficient base don local availability and costs of all these different elements.

Good luck and let us know which one you chose in the end - we like feedback on this site.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[lpfaustini]

Dear fellows,

Thank you all for sharing the knowledge here placed. There are some many things to put in the balance. As I noticed, each one has its own solution (heat tracing, steam bayonet heaters, eletric heaters, heating coils). I did not get to the decision yet, but I already contacted suppliers here in Brazil. One thing I was already informed though: boiler will be big and expensive.

Thank you for wishing me good luck. And sure I will get back here to give you a feedback.

 

[Compositepro]

Yes, if you do not already have steam available you do not want to use steam for heat. The main advantage to steam is that it inherently avoids any possibility of overheating the viscous oil and causing coking. With direct electric heat you can use a low Watt-density heaters (Watts per square cm of heater surface). It is even possible to use electric immersion heaters in a large water-filled pipe which is inserted into the side of the storage tank,like a stream bayonnet heater.

With any solution, appropriate controls and safety devices are required.

 

[chicopee]

Even steam has its perils. I have seen a boiler completely destroyed when the heat exchanger sprang a leak and bunker C followed the steam path into the boiler.

 

[lpfaustini]

chicopee

This is actually no good.

 

[lpfaustini]

As I promissed, I'm back to inform that investigations are going on and I received quotation from suppliers of Eletric Trace Heating and Eletric Immersion Flanges (bayonets). The price is the almost the same for the two options. Of course, trace heating requires thermal insulation, the other one doesn't need it.

I'm still waiting one final quotation to make the decision.

 

[LittleInch]

Don't know if you're adding / factoring in OPEX costs, but no insulation will significantly increase that...., but correct, external trace heating is a waste of time of you've no insulation.

Insulation normally has a 3-5 year payback time, maybe less if it's electric.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[lpfaustini]

Dear group fellows,

As I promissed, I came back and I'd like to share what I found.

First of all, things in Brazil are different and technology is hard to find. Suppliers are in a few number and my options to heat the tank were reduced. I did a checklist, but in the end, only 4 items were checked. According to our previous conversation here in this topic, with low OPEX/high CAPEX, I decided to go "eletric".

My first choice checked was eletric bayonet heaters without thermal insulation. Supplier said that 7 bayonet heaters were enough to rise the temperature within 168 hours and 2 bayonets to keep the temperature. To ensure homogeneity, I also quoted 2 sided mixers. Overall, the price was good, but energy comsumption was a problem.

Second choice was electric heat tracing. The supplier, a company named THERMON, got here in Brazil this year. The material had to be imported from US. And it required thermal insulation. Rising the temperature was not good for heat tracing (almost 15 days), but the advantage of this system is to keep the temperature. Overall, price was higher than eletric heat tracing, but not so much. The energy comsuption is very low and, compared to the first choice, it compensates the investment in less than 1 year.

Third choice was eletric bayonet heaters with thermal insulation. With higher investment, the price matched trace heating, but nevertheless, energy comsuption was more than heat tracing.

Fourth choice was eletric suction heater. The worst choice of all. The suction heater working alone was insufficient. So I needed to add trace heating to the tank (+ thermal insulation) in order to make the suction heater functional. Price was very high in the end, and even the suction heater only working 4 times a month, energy consumption matched third choice.

 

[LittleInch]

Ipfaustini,

Thanks for getting back to us - it's always good to see what happened later on.

I think you meant low CAPEX/High OPEX in your first para, but I get the drift.

Insulation and keep it warm tends to work best for electric trace heating systems otherwise the energy to warm it up is HUGE or it takes a long time.

Would be interesting to know if the pain of all this is worth it in terms of reduced fuel cost from a fuel which didn't need heating like MJCronin said above....

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way