PHOSPHORIC ACID HEATER
Galiakotwala Engineering’s Alloy Phosphoric Acid Heater achieved 23% higher heat transfer efficiency and zero damaged or plugged tubes compared to the replaced Graphite Heater.
Phosphoric acid (H₃PO₄) is commonly concentrated from a dilute solution (~25-30%) to a higher concentration (~50-54%) in fertilizer and chemical plants. This is done using evaporation systems which includes a Shell and Tube Heat Exchanger.
How It Works
The Shell and Tube Heat Exchanger is used to heat the phosphoric acid, causing water to evaporate, thereby increasing acid concentration. Steam or hot water flows through the shell, while phosphoric acid flows in the tube (or vice versa depending on design). The heat causes partial evaporation of water content, leading to a higher concentration of phosphoric acid in the outlet stream.
The key selection criteria for a new Phosphoric Acid Heater is material selection and design.
Challenge: Phosphoric Acid Impurities
Corrosion
Due to presence of Halides, Sulphuric / Phosphoric / Hydrochloric Acid and many more corrosive compounds.
Erosion
Due to Gypsum crystals, rock particles, Silica, etc. in turbulence and deposit formation.
Conventional technology uses Graphite to solve these problems. However, Graphite lacks mechanical strength. This leads to tube damage and failure of the Heat Exchanger and subsequent cleaning. This can further lead to plant shutdown and downtime.
A more advanced solution is a Phosphoric Acid concentrator using a special Metallic Alloy.
Comparison Between Graphite and Metallic Alloy Tubes
PARAMETER
GRAPHITE TUBES
ALLOY TUBES
Mechanical Strength
Resistance to Erosion-Corrosion
Tube Cleaning
Tube Wall Thickness
External Tube Diameter
Heat Transfer Efficiency
Brittle, prone to fracture during cleaning
Lower resistance compared to metallic alloys
Needs extreme caution to avoid fractures
Thicker walls required to avoid fracture
Larger diameter required for similar mechanical stability
Higher due to better thermal conductivity
Offers higher mechanical strength and greater resistance to erosion
Better resistance
Can handle high pressure water washing
Thinner walls possible due to higher strength
Smaller diameter possible due to higher mechanical strength
Can maintain efficiency with redesign (more tubes, thinner walls)
Advantages of Metallic Phosphoric Acid Heater
Based on the above comparison the advantages of Alloy Heat Exchangers over Graphite Heat Exchangers are:
Longer Life
- The life of Metallic heater is much longer than Graphite Heater.
Low Maintenance
- The maintenance cost of the Metallic Heater is much lower than that of the Graphite Heater.
Lesser Breakdown
- The efficiency of Graphite Heater goes down as damaged tubes have to be blocked, which affects production capacity.
Easier Tube Replacement
- Metallic Tubes can be replaced maintaining production capacity.
Advanced Design
Galiakotwala Engineering uses sophisticated modelling software to ensure customized design for each and every Heat Exchanger to ensure it performs as required.
Detailed Design Approach*
Study of Combined Stresses*
*Illustrations are for representation purposes only.
What Our Customers Say
“We have been using Graphite Heaters for a long time and faced the usual problems of damage of tubes during washing. We replaced the Graphite Heater with Alloy Heat Exchanger supplied by Galiakotwala Engineering and since installation we have no damage to any tubes and cleaning time has reduced significantly as we can increase the pressure of the cleaning fluid during the cleaning cycle. Heat transfer also has improved due to reduced thickness of the tubes carrying Phos Acid.”
Confidential Client
(International Fertilizer Plant)
