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Steam Generation and distribution, 22BCM0029 SAI VARSHINI - Coggle Diagram
Steam Generation and distribution
Importance of Steam in industries
Saturated steam is typically preferred in industrial applications for heating, drying, and cooking due to its superior heat transfer characteristics and consistent temperature profiles.
In heat exchangers, saturated steam induces a thin layer of condensate on the heating surface, enhancing heat transfer efficiency.
Applications of Steam
Propulsion and Drive Applications Steam turbines are commonly used for electricity generation in thermal power plants, utilizing superheated steam to avoid equipment damage from condensate.
High-pressure saturated steam is often used in nuclear power plants, necessitating the installation of separators in supply piping to eliminate entrained condensate
Typical applications also include turbine-driven compressors and pumps, such as gas compressors and cooling tower pumps.
Steam Types
Wet Steam: A two-phase mixture of water and steam, which includes both water molecules and steam.
Dry Steam: Dry saturated steam that exists at saturation temperature with no water molecules present.
Superheated Steam: Steam that has been heated beyond its saturation vapor temperature at a constant pressure, typically used to prevent equipment damage in steam turbines.
Boiler and Steam Generation
Water tube boilers operate under pressures from 7 bar to 250 bar, producing steam temperatures between saturated states to superheated states (600-650°C). The performance of a boiler is measured in tons of steam produced per hour for water tube boilers this can range from 1.5 t/h to 2500 t/h.
Process of Steam Creation: The heat energy required for steam generation involves both sensible and latent heat. As the water reaches its boiling point (saturation temperature), it undergoes vaporization, with additional heating leading to superheated steam that follows gas laws.
Boiler Mountings
Definition: Safety devices attached to the boiler.
Examples: Pressure gauge, water level indicator, safety valves, fusible plug.
Purpose: Ensuring safe and controlled operation.
Boiler Accessories
Definition: Devices that improve boiler efficiency.
Examples: Superheaters, economizers, air preheaters.
Purpose: Enhancing boiler performance and reducing fuel consumption.
Performance Evaluation of Boilers
Boiler Blowdown**
Removes dissolved solids
Prevents scale formation
Prevents foaming and carryover
Maintains TDS level
TDS limits in boilers
Boiler Efficiency
Percentage of fuel heat converted to steam
Direct Method
Ratio of output (steam) to input (fuel)
Parameters: Steam quantity, fuel quantity, pressure, temperature, fuel GCV
Formula: Efficiency = (Q
(hg - hf)) / (q
GCV)
Advantages: Quick, few parameters, few instruments
Disadvantages: No loss analysis
Efficiency = 100% - (Sum of heat losses)
Losses: Dry flue gas, moisture in fuel/air, hydrogen combustion, radiation, unburnt fuel
AAS (Actual mass of Air Supplied)
Boiler Evaporation Ratio (BER)
Steam generated per kg of fuel
Higher BER = better efficiency (generally)
Example (Indirect method, BER calculation)
Condensate Recovery and Utilization
Condensate*
Water from condensed steam
Contains sensible heat
Recovery Benefits
Energy savings (10-30% of steam heat)
Reduced fuel costs (10-20%)
Lower water expenses
Positive environmental impact (reduced emissions)
Improved safety
Reduced boiler blowdown
Less corrosion
Utilization
Heated feed water (deaerator)
Pre-heat for other systems
Flash steam reuse
Hot water for cleaning
Condensate Recovery vs. No Recovery
No recovery: Wasted energy, water, and chemicals
Recovery: Reduced costs and environmental impact
22BCM0029 SAI VARSHINI