Steam Generation

Chapter from the Miscellaneous Design Guide.

PROCESS UNIT STEAM GENERATION SYSTEMS

Steam System Overview for Process Units

Many process units include waste heat steam generation systems that recover heat from hot process streams to generate steam. Common configurations:

1. Waste Heat Boiler (WHB): generates steam from hot flue gas, reactor effluent, or FCC regenerator flue gas
2. Heat Recovery Steam Generator (HRSG): recovers heat from gas turbine exhaust
3. Process Steam Generator: shell-side boiling exchanger using hot process stream as heat source
4. Reboiler Condensate Flash: flash high-pressure condensate to generate low-pressure steam

Steam System Hierarchy (typical refinery):
• 600 psig (superheat): turbine drives, process heating
• 150 psig (saturated): medium-pressure process heating, turbine exhaust
• 50 psig (saturated): low-pressure heating, tracing, deaerator
• 15 psig (saturated): lowest pressure, tank heating, winterizing

Boiler Feedwater Quality Requirements

Parameter	600 psig	150 psig	50 psig	Units	Consequence of Violation	Standard
Total Dissolved Solids	<500	<1,500	<3,500	ppm	Foaming, carryover	ASME/ABMA
Hardness (as CaCO3)	<0.3	<1.0	<5.0	ppm	Scale formation	ASME
Dissolved Oxygen	<7	<7	<20	ppb	Corrosion (pitting)	ASME
Iron	<50	<100	<300	ppb	Deposit formation	ASME
Silica	<20	<50	<100	ppm	Silica deposits in turbines	ASME
pH (at 25°C)	8.5-9.5	8.5-9.5	8.5-9.5	—	Corrosion (low) or caustic (high)	ASME
Phosphate (if treated)	2-5	5-15	5-30	ppm	pH control, scale prevention	ASME

Source: Miscellaneous_Design_Guide_v1.xlsx · sheet “Steam Generation”

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