Thursday, April 15, 2021

HOW TO SIZE THE BOILER


How To Size the Boiler:

To Select Boiler.

·         Density of the oil         =900 kg/m3
·         Process settling time     =45-60 min (consider 50 min )
·         final temperature of the oil = 600C
·         specific heat capacity values,
§  oil                    = 2 KJ/kg 0k
§  316 SS             =0.5 KJ/ kg 0C (Agitator)
§  Mild Steel        =0.62 KJ/ kg 0C (kettles)
We have three blending kettles such as 5m3,10m3,15m3.
·         Oil viscosity
§  550-700 (Viscosity @ 40 C mm/sec (CSt))
§  30-34 (Viscosity @ 100 C mm/sec (CSt))
·         weight  of kettles
§  5m3  kettle        = 855 kg without manhole weight
§  10m3 kettle      = 1460 kg without manhole weight
§  15m3 kettle      = 2072 kg without manhole weight
·         weight of agitators
§  5m3  kettle        = 51 kg
§  10m3 kettle      = 70 kg
§  15m3 kettle      = 130 kg


Oil processing industry need to select the boiler for their new expansion. Above detail has given by client. There are two demands in steam in process.
1.       Start up                         -              Steam jacketed kettle + Oil heating + Head loss
2.       Continuous operation    -              Oil heating + Heat Losses

Start up

Assumption
1.       temperature increase 30 °C to 60 °C
2.       Operating pressure of boiler considered as 6 bar(g) = 7 bar actual (hfg@ 7 bar = 2067 kJ/kg)
3.       Heat losses are neglected.

Calculation
Heat Requirement (kJ)
Steam Requirement (kg)
Steam jacketed kettles
4387 X 0.62 X 30
81,598.2
39.47
Oil heating
30 X 900 X 2 X 30
1,620,000
783.74
Agitators heating
251 X 0.5 X 30
3765
1.82
Total


825.03

Initial steam requirement is 825.03 kg at 6bar(g) operating pressure.
Calculating Steam Rate
They need to heat up the system within 50 min.
Steam flow rate                =             825.03 X (60 /50)
                                        =             990.03 kg/hr

Continuous Operation

In this time steam jacketed kettle has heated to 60 °C. Similar calculation

Calculation
Heat Requirement (kJ)
Steam Requirement (kg)
Oil heating
30 X 900 X 2 X 30
1,620,000
783.74
Total


783.74

Calculating Steam Rate
They need to heat up the system within 50 min.
Steam flow rate                =             783.74 X (60 /50)
                                        =             940.48 kg/hr
There is no big difference in star up and the continuous operation. So ideal steam requirement is 990kg/hr.
Multiply 10 % factor for losses of the system.
20% additional factor considers. This is due to feed water temperature and operating pressure of the boiler. This reduces the boiler capacity.

Final Estimated Boiler capacity   =             990 X 1.1 X 1.2
                                                 =             1306.8 kg/ hr

1500 kg/hr (F&A 100 °C) Boiler meet the client requirement.

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