4 replies to this topic

[Valeriacortez11]

Good morning.
I would like to consult, when I already have an accumulator installed, how can I diagnose the recharge time of this one. I have sized an accumulator to supply for 10 minutes. It is 20m3, but in the quotation I have from ATTSU it does not mention any time limit to recharge it. I understand that it is based on the period where the demand is low but for an accumulator of this size and a boiler that can deliver 10,000 kgv/h is it ok to assume that the recharge time is about 15 minutes or less?

Another query if you can help me, the accumulator understands that it must lower the pressure inside to change phase and generate steam by means of valves or is there any programming with programmable logic?

And if you allow me another question, I have tried to analyze how to find the savings of this accumulator, at first I had related it to the fuel, that if my accumulator produced 4,000 kgv/h was equivalent to a certain amount of fuel (this was found from SCADA values of the company, when a boiler generated 4,000 a certain volume of GLP was consumed, then that was the savings GLPx $/GLP when the accumulator was operating.

Another analysis is if I have the boiler cycling per hour suppose that those cycling losses if decreased translates to accumulator savings.

Can you help me please, I do not have any experienced advisor on these issues.

Edited by Valeriacortez11, 26 June 2024 - 09:23 AM.

[katmar]

You have given the boiler steaming rate, but you must also know the pressure at which the boiler delivers the steam and the pressure at which the steam is delivered to the process in order to determine the recharge time.

The usual control strategy is simple. If the pressure in the steam range that is supplied from the accumulator goes below the set point a valve will open and draw steam from the accumulator. Drawing steam from the accumulator like this will lower the pressure in the accumulator and the hot water will flash to create more steam.

The purpose of the accumulator is not really to save fuel. The aim is to smooth out the draw from the boiler by supplying steam to the process when the demand is higher than the boiler can deliver, and to store energy (steam) when the demand is low. This would enable you to use a boiler with a lower peak capacity i.e. a smaller, cheaper boiler, You may get some fuel savings through improved efficiencies by running the boiler more steadily but this is a minor effect.

[Valeriacortez11]

Hello,
The boiler will operate at 13 bar g and deliver steam at 10 barg in the accumulator inlet line.
It was mentioned to me that, when the pressure drop occurs in the boiler line due to over demand it is possible to go as low as 9 barg. And the other boiler in line takes at least 7 minutes to be able to supply the required steam.

Is it possible that the steam recharge in the accumulator takes minutes?

Ok, I have a better understanding of the operation thank you.

Edited by Valeriacortez11, 26 June 2024 - 11:19 AM.

[katmar]

Let's take some very approximate numbers. Assume that the accumulator cycles between 5 barg and 10 barg. At 5 barg the condensate holds 670 kJ/kg and at 10 barg 781 kJ/kg. If the heat of condensation of the steam used to recharge the accumulator is 2000 kJ/kg you would need to condense (781 - 670)/2000 = 0.056 kg of steam to heat up each kg of condensate. If the accumulator held 14 tonne of condensate it would need 14000 x 0.056 = 780 kg of steam.

There would also be be some steam required to fill the vapor space. Assume 4 m3 of steam with a density of 5.6 kg/ms. That is only another 22 kg and basically negligible.

So you need to supply about 800 kg of steam and based on your boiler size this could indeed take minutes.

But note that in the discharge cycle you can only take out the 800 kg that you put in - actually slightly less because of heat losses.

[breizh]

Hi,

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Breizh