11 replies to this topic

[adeliry]

Dear Professionals,

in our new plant ( start up of new plant) procedures indicated that to produce MPS( 4.6 barg and T=161 oC) from HPS( 40barg and T=390 oC), HPS pressure after passing a Control valve droped to 4.6bar and to decrease the temperature we must inject Condensate( 14bar and 100 oC) .

maximum steam flowrate in high usage is 130 ton/hr and to decrease temperature of it we must use maximum 12 ton/hr condensate.

but todays that we began to start up this section of our unit, injecting of 12 ton/hr of condenstae (FT is callibrated and also we checked flowrate with time needed to rise the level in a barrel ) can't drop the temperature of 40ton/hr of steam and we can only decrease temperature to 256 oC.

we Checked the injection nuzzles and there is not any problem.

can you advice me?/


Thanks

Edited by adeliry, 08 September 2009 - 07:07 AM.

[herrani]

Hi Aderly

I just made a quick check of your problem using Hysys:

1. Feed is HPS, which is expanded in a control valve to 4.6 bar g
2. HPS flow is 130 tn/h
3. The expanded HPS is mixed with steam condensate, at a rate of 12 ton/h

At those conditions, the temperature of the MPS is 249 C, which is what you have seen in reality.

I would say your best option would be to increase the condensate flowrate to 24 ton/h. This should reduce the temperature to 161 C. This sounds like a design mistake to me.

If that is not possible due to the capacity of the control valve or condensate line, you will need to make some changes in your process.

Let me know if this help!

[siretb]

130 tonne/hr 40barg and 12 tonnes/hr condensates 100°C yield 249°C . Please check you enthalpy balance. You need more condensates, your team is still superheated.

[herrani]

130 tonne/hr 40barg and 12 tonnes/hr condensates 100°C yield 249°C . Please check you enthalpy balance. You need more condensates, your team is still superheated.

130 ton/hr @ 4.6 bar g and approx. 380 C + 12 ton/hr condensate yield 249 C.

I have attached my Hysys simulation for your reference.

Attached Files

•  steam calcs.pdf   7.43KB   147 downloads

[ankur2061]

Dear Professionals,

in our new plant ( start up of new plant) procedures indicated that to produce MPS( 4.6 barg and T=161 oC) from HPS( 40barg and T=390 oC), HPS pressure after passing a Control valve droped to 4.6bar and to decrease the temperature we must inject Condensate( 14bar and 100 oC) .

maximum steam flowrate in high usage is 130 ton/hr and to decrease temperature of it we must use maximum 12 ton/hr condensate.

but todays that we began to start up this section of our unit, injecting of 12 ton/hr of condenstae (FT is callibrated and also we checked flowrate with time needed to rise the level in a barrel ) can't drop the temperature of 40ton/hr of steam and we can only decrease temperature to 256 oC.

we Checked the injection nuzzles and there is not any problem.

can you advice me?/


Thanks

Adeliry,

I did not require HYSYS to do a enthalpy and mass balance for your case. My results are done on an excel sheet and here is what I get for your conditions:

MP Steam flow: 130 T/h @4.6 barg, 161 degC
Superheated Steam: 110.466 T/h @40 barg, 390 degC
Sub-cooled Condensate: 19.534 T/h @14 barg, 100 degC

Try doing the calculations yourself:

Basic equations:

M1 + M2 = M3

M1H1 + M2H2 = M3H3

where
M1 = mass flow rate of superheated steam
M2 = mass flow rate of sub-cooled condensate
M3 = mass flow rate of MP Steam, 130 T/h
H1= enthalpy of superheated steam @pressure, temp.
H2 = enthalpy of sub-cooled condensate @pressure, temp.
H3 = enthalpy of MP steam @pressure, temp.

Solve the equations for either M1 or M2 to get your answer.

Hope this helps.

Regards,
Ankur.

[adeliry]

Dear Professionals,

in our new plant ( start up of new plant) procedures indicated that to produce MPS( 4.6 barg and T=161 oC) from HPS( 40barg and T=390 oC), HPS pressure after passing a Control valve droped to 4.6bar and to decrease the temperature we must inject Condensate( 14bar and 100 oC) .

maximum steam flowrate in high usage is 130 ton/hr and to decrease temperature of it we must use maximum 12 ton/hr condensate.

but todays that we began to start up this section of our unit, injecting of 12 ton/hr of condenstae (FT is callibrated and also we checked flowrate with time needed to rise the level in a barrel ) can't drop the temperature of 40ton/hr of steam and we can only decrease temperature to 256 oC.

we Checked the injection nuzzles and there is not any problem.

can you advice me?/


Thanks

Adeliry,

I did not require HYSYS to do a enthalpy and mass balance for your case. My results are done on an excel sheet and here is what I get for your conditions:

MP Steam flow: 130 T/h @4.6 barg, 161 degC
Superheated Steam: 110.466 T/h @40 barg, 390 degC
Sub-cooled Condensate: 19.534 T/h @14 barg, 100 degC

Try doing the calculations yourself:

Basic equations:

M1 + M2 = M3

M1H1 + M2H2 = M3H3

where
M1 = mass flow rate of superheated steam
M2 = mass flow rate of sub-cooled condensate
M3 = mass flow rate of MP Steam, 130 T/h
H1= enthalpy of superheated steam @pressure, temp.
H2 = enthalpy of sub-cooled condensate @pressure, temp.
H3 = enthalpy of MP steam @pressure, temp.

Solve the equations for either M1 or M2 to get your answer.

Hope this helps.

Regards,
Ankur.

Dears,

Thanks for your reply

But i said that now we inject 12ton/hr condensate to 40ton/hr HPS and it can't decrease the temperature. in unit manual said that this amounth of condensate can decrease the temperature of HPS in maximum rate 120 ton/hr that it seems mistake, but now we use maximum rate of condensate to only 40 ton/hr HPS.

I also must be say that when we check the MPS line and open drain of line , we have alot of condensate in line and it seems that injected condensate couldn't vaporize and we have two phase in line , above is steam and down of line is condensate that couldn't vaporize.

i said before that we checked nuzzels and it can spray condensate very well.

[Homayun]

Adeliry,

I think 12 T/hr of Condensate is simply too mych for 40 T/hr HP-steam. According to my calculations, you need only 7 T/hr of codnensate. That's probably the reason why you are having 2 phase in your pipe.

Regards

Homayun

[shan]

Dear Professionals,

in our new plant ( start up of new plant) procedures indicated that to produce MPS( 4.6 barg and T=161 oC) from HPS( 40barg and T=390 oC), HPS pressure after passing a Control valve droped to 4.6bar and to decrease the temperature we must inject Condensate( 14bar and 100 oC) .

maximum steam flowrate in high usage is 130 ton/hr and to decrease temperature of it we must use maximum 12 ton/hr condensate.

but todays that we began to start up this section of our unit, injecting of 12 ton/hr of condenstae (FT is callibrated and also we checked flowrate with time needed to rise the level in a barrel ) can't drop the temperature of 40ton/hr of steam and we can only decrease temperature to 256 oC.

we Checked the injection nuzzles and there is not any problem.


can you advice me?/


Thanks

Please check your MPS pressure. If the saturation temperature (both water and steam exist) is 256 oC, the saturation pressure should be 43 barg not 4.6 barg.

[vahidforughi]

Salam jenabe mohandes .mikhastam bebinam darbareye steam system desig yani bishtar rooye
mohasebate size equipment hash mitunid komakam konid.alal khosus ruye deareator,boiler,pumphava condensate drum ha.mikhastam mostaghiman behetun email bezanam moteasfane nafashtam emailetuno .majbur shodam edameye hamiin topic azatun beporsam.
Mamnoonam

[GS81Process]

For 130 t/h of your HPS you will need roughly 23.65 t/hr of your condensate.
For 40 t/h of your HPS you will need roughly 7.8 t/hr of your condensate.

Source: mass and energy balance using steam tables. Let down of your HPS is an isenthalpic (constant enthlapy) process.

Edited by GS81Process, 11 January 2012 - 01:32 PM.

[S.AHMAD]

1. Based on PRO-II simulation. For 40 t/h of HP steam with 12 t/h of condensate. The MP steam will be of mixed flow with 47.2 t/h MPS and condensate of 4.8 t/h at saturated temperature of 156.5C.
2. The above finding is consistent with field observation that the MP steam contains a lot of condensate.
3. However temperature of MP steam is 256C. Therefore I suspect that the temperature sensor is not correct thus it gives wrong signal to you temperature controller.
4. Letting down 40 t/h HPS to MPS at temperature of 161C, requires 6.8 t/h condensate
5. Propose - calibrate temperature sensor

Edited by S.AHMAD, 10 January 2012 - 10:35 PM.

[GS81Process]

I reviewed adeliry's original post and believe that S. Ahmad's answer is correct. Your MP Steam temperature sensor is likely giving wrong measurements.