Deaeration Systems: Acheiving a few Parts per Billion of Free Oxygen
Commercial and Industrial Boilers operate at their best when the incoming boiler feed water is free from dissolved gasses. In particular, dissolved oxygen will cause severe corrosive damage to the boiler internals. Dissolved oxygen also combines with any dissolved carbon dioxide to form carbonic acid which accelerates corrosion. Deaerators are designed to remove oxygen down to 7 parts per billion (ppb) by weight (0.0005 cm³/L) or less.
A properly operated and well maintained deaerator will dramatically improve boiler lifespan and performance as well as reduce the volume of chemical oxygen scavenger required, such as sodium sulfite (Na2SO3).
Cochrane offers a broad range of Uni-Pac Jet Tray deaerators in both Parallel Downflow and Counterflow configurations. The basic equipment is the Cochrane pre-engineered, standardized Uni-Pac design. The options make available additional pre-engineered features that permit custom deaerator design at pre-engineered prices.
A view from inside a deaerator under construction.
Parallel Downflow Deaerators (PDF)
The Uni-Pac Jet Tray Parallel Downflow Deaerator offered below is manufactured per the following specifications:
Deaerator Type: Jet Tray Parallel Downflow.
Pressure Vessel Construction: Fabricated and certified per ASME Code for Unfired Pressure Vessels (Design pressure is 30 psig with minimum corrosion allowance in standard design with options for increased design pressure and corrosion allowance advanced in modification tables) Formed type 430 stainless steel (22 gauge-standard design, 16 gauge in "Super" design).
Trays:
Vent Condenser: Direct contact design, type 304 stainless steel construction (304L in designs being post-weld heat-treated).
Water Distributor: Type 316 stainless steel spring loaded "Accu-Spray" nozzle(s). Full load pressure drop is 3 psig.
Oxygen Guarantee: 0.005 cc/l at feedwater temperatures 35 degree F and above.
Cochrane World Famous Pre-Engineered "T" Series Uni-Pac Jet Tray Parallel Downflow Deaerators
Tank Car model has deaerator section and storage section welded together as one unit while Double Shell model has deaerator section and storage section flanged together to form one unit.
Key Benefits:
- 0-100% Turndown Capable
- Best Selection for High Percentage of Make-Up Water Applications. (Counterflow DA's generally do not perform well under high make-up water applications)
- Employs Accu-SprayT Technology
World Renowned Chicago Heater Brand Counterflow Deaerators
Deaerator Type: Counterflow
Head & Shell Material: Carbon Steel, 516 Grade 70
Pressure Vessel Construction: Fabricated and certified per ASME Code for Unfired Pressure Vessels (Design pressure is 30 psig with minimum corrosion allowance in standard design with options for increased design pressure and corrosion allowance advanced in modification tables).
Trays: Pan type. 16 gauge 430 stainless steel
Vent Condenser: Direct contact design, type 304 stainless steel construction
Water Distributor: Type 316 stainless steel spring loaded "Accu-Spray" nozzles. Full load pressure drop is 3 psig.
Oxygen Guarantee: 0.005 cc/l at feedwater temperatures 55° F and above.
Key Benefits
- For Larger Capacity Applications
- Best Selection in Large Central Station Type Power Plants
- Employs Accu-SprayT Technology
Chicago Heater Brand Counterflow Spray-Tray Deaerators
The Chicago Heater Brand Series TC deaerator utilizes a vertical tray heater welded to a horizontal storage vessel resulting in a "tank car" configuration. Design and manufacture are in accord with the ASME Code for unfired pressure vessels. A water box assembly is welded in the top of the heater section and contains the Accu-Spray spray nozzles and vent piping system. Beneath the water box is the vent condensing chamber, which is contained in the upper third of the tray enclosure, and which provides for intimate steam-water contact and release of non-condensible gases to the vent system. The lower two-thirds of the tray enclosure houses and positions Crane Environmental's 16 gauge riveted tray assemblies. It is this arrangement that permits the two-stage counterflow heating and deaerating process to function fully contained within an enclosure that isolates all un-deaerated water and corrosive gases from the vessel. Unless otherwise specified, the Accu-Spray nozzles, valve mounting plate, vent condensing chamber, tray assemblies, tray enclosure walls, steam baffles and vent pipe systems are stainless steel. Vessel heads and shells are low carbon steel welded steel plate. Heavy support saddles, access openings and connections for piping and accessories, as proposed and purchased, are included.
Deaerator Top: Welded Steel Plate, ASME Stamped.
Storage Tanks: Welded Steel Plate, ASME Stamped.
Vent Condenser: Direct Contact Type with 304 Stainless Steel baffling
Trays: Type 430 Stainless Steel
Water Distributor: 316 Stn. Stl. Accu-SprayDesign
Pressure: As Required
Advantages of Counterflow Method:
Cost competitive for large capacity applications.
Highly reliable for attaining specified results over a varying load range.
Simplicity and rugged design offers cost savings for many applications, especially where a high percentage of condensate returns are introduced.
Good selection for applications with very high percentage of flashing condensate and for higher inlet temperature applications.
Easy access for spray nozzle inspection, even on smaller models.
Limitations:
Tray compartment area requirements become inwieldy as inlet temperature falls below 60°F.
Unable to deaerate condensate from flashing return lines during start-up and re-starts.
Requires 40°F. temperature to meet operating warranty.
Genuine Cochrane Replacement Parts:
Only genuine Cochrane Deaerator parts can guarantee the performance of your deaeration system. When scheduling system shutfdown and maintenance, it is always best to call your Cochrane representative to set up an inspection to be sure that your system is operating at peak efficiency.
Deaerators are sized according to boiler feedwater and operational requirements. They may be quite small or very large. A large deaerator leaves the factory by truck for final assembly on the job site.