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 mm² /sec (CSt))

§  30-34 (Viscosity @ 100 C mm² /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 (h_fg@ 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.