800 MW Boiler Reheater Outlet Steam Temperature Low

What's the usual reading at outlet state, what's the pressure?

Would it mean, that there's no heat transfer at constant temperature? Pls. review latent heat concept.

I observed Anonymous Post rise exponentially by 10am.

At Reheater outlet, We get 569 c, 53 Kg/cm2 at and Predicted Performance data shows 596 c, 58 Kg/cm2 @ 800 MW

Check draft fan, nozzle and Heat content of fuel. Air fuel ratio might not be optimal. If ok, see if there no steam leak at reheater.

What temperature are you looking for at the Reheater discharge/outlet?

If the Main Steam Pre/Temp is 568 C and you want a higher Reheater outlet temperature:

Either/Or;

The burner(s) are not providing enough heat for the process application? (Low BTU fuel, Low firing rate, bad Fuel-to-Air ratio, ?)

Poor Reheater section insulation resulting in large heat losses and excessive temperature differential?

We are supposed to get 596 c temperature at Reheater outlet

Why aren't you talking to the goobers that built this system instead of us?

Dear Friend,

The Low Temp. of Re-Heat Steam Temp. - Is it from the beginning of the operations of the boiler or it occurred after commissioning.?

The Low Temp. of Re-Heat Steam Temp. could be on 2 accounts.

On Design Aspects:

1. Pl. check for the Over-All Heat Transfer Co-Efficient for the Re-Heater.

2. Flow of Flue Gas Quantity and its Temperature before and after the Heater.

3. Heating Surface provided.

4. Temp. of Steam entering the Re-Heater.

5. Air Temperature assumed for the design from the Air Pre-Heater.

On Operational Aspects:

1. Cleanliness or fouling of the Heating Surface, by Soot.

2. Ingress of cold air before the Re-Heater.

3. Blockage of Flue Gas in the path.

4. Short Circuit of Flue Gas on account Baffle falling out.

5. Ineffective and Improper Soot Blowing.

6. Less Temp. of the Seam entering the Re-Heater for re-heating purpose, due to improper lagging.

7. Moisture/Wetness in the Steam instead of dry steam entering the Re-Heater.

8. Lesser Calorific Value of the Fuel than actually taken for combustion, and hence Lesser Temperature Gradient in the Flue Path.

9. More of Un-Burnt particles than permissible limits resulting in Lesser Heat Release in the Furnace.

10. Lesser Temperature of Air Leaving the Air Pre-Heater, than the design value.

11. Higher Ash content in the fuel, resulting in Lesser Heat Release in the Furnace.

12. Higher Air-Fuel Ratio - which dilutes the Temperature Gradient in the Flue Path.

Pl. post the information what was the cause of the problem.

DHAYANANDHAN.S

Dear Sir,

Thanks for your valuable suggestions, I will reply with all operating parameters as requested by you asap.

Dear Friend,

I for got to add one more point.

The Steam Flow Quantity for Re-Heating will much more than the designed value.

Under Identical Conditions, more steam flow means, the Temperature Rise will be LESS.

DHAYANANDHAN.S

Dear Sir,

Q:The Low Temp. of Re-Heat Steam Temp. - Is it from the beginning of the operations of the boiler or it occurred after commissioning.?

R:The problem is from beginning and the plant is in commissioning stage only. Boiler on/off service from last 7 months due to various reasons i.e. coal, water etc

Q: Temp. of Steam entering the Re-Heater

R: Ok.CRH temperature at Boiler inlet is 347 c and it's matching predicted performance data. But CRH pressure remains at lower side by 3-4 kg/cm2.

Q: Cleanliness or fouling of the Heating Surface, by Soot.

R: Unit is running on coal having Ash-30 % but heating surfaces are not heavily fouled by Soot.

Q: Ingress of cold air before the Re-Heater.

R: No

Q: Blockage of Flue Gas in the path

R: I'm not sure but inspection possible during next outage only.

Q: Short Circuit of Flue Gas on account Baffle falling out

R: Baffles are intact but minor Short Circuit of flu gas at Backpass frontwall screen tubes. Tons of ash accumulation above steam cooled floor panel area.

Q: Ineffective and Improper Soot Blowing

R: Unfortunately Wallblowers are still in early days of commissioning. No LRSB commissioned.

Q: Lesser Calorific Value of the Fuel than actually taken for combustion, and hence Lesser Temperature Gradient in the Flue Path.

R: Yes. 800 MW Predicted Data Coal Consumption: 350 TPH; Actual Coal Consumption: 390 TPH, Therefore Lower GCV fuel being fired.

Q: More of Un-Burnt particles than permissible limits resulting in Lesser Heat Release in the Furnace.

R: Data not available.

Q: Higher Air-Fuel Ratio - which dilutes the Temperature Gradient in the Flue Path.

R: Yes. As per Design Total Air Flow: 1950+610 TPH; Actual Total Air Flow: 2010+ 945 TPH. Individual Mill PA flow increased to get desired Mill outlet temperature=80 c

I dont have design parameters.

If any more data required, pls post.

Kindly provide your advice to improve HRH outlet temp.

Thank you

Most of the data that you provided in response to Mr. D's excellent set of questions points to a boiler designed for high quality, low ash content coal being operated with lower quality very high ash content Indian coal.

Here's why:

1. High ash fouling of radiative heating surfaces

2. Poor to non-existent sootblower performance

3. Need to increase pulveriser air flow and temperature (you didn't say why but probably to reduce the moisture content to reduce agglomeration of fines)

4. "Tons of ash accumulation"

5. 15% increase in coal consumption against design standards. This affects the performance every system in your boiler, effectively lowering your overall plant efficiency by at least that amount.

6. Total air flow at (no surprise) 15% over design standard.

More than likely your boiler was manufactured off of blueprints for a "generic" 800 MW plant, not for the fuel and ambient conditions of your particular location. Kind of like copying the plans for an anthracite plant in a temperate zone and firing it with lignite in the tropics.

Your best bet is to get each individual system working to its best possible level under the circumstances, and then tuning them to play together nicely. It is unlikely that you will ever get 800MW out on a sustained basis at any kind of economically justifiable overall plant heat rate.

Reminds me of an old saying "The lowest bidder is usually not the best bidder unless your engineers are much better than theirs".

Dear Sir: Could you please ask the gentlemen at the PF 800MW plant being commissioned if all inputs to the HMI have been thoroughly checked for assignment errors. The RHOT is suspiciously near the SHOT. That is what I have been vociferously attempting to convey to these rather hotheaded gentlemen.