EOR Once Through Steam Generator

ENHANCED OIL RECOVERY

The EN-FAB Steam Generator is a "Once Through" forced circulation type. Designed to supply wet, saturated or superheated steam discharge conditions, Once Through Steam Generators are favored for any installation where low life-cycle costs, high reliability, and or high-purity steam is desired. Pressure ratings are supplied to customer's specifications and are normally furnished in 1000, 1500, or 2500 PSIG working pressure.

 

The horizontal design is utilized for easier transportation, field installation and repair, use of either gas or liquid fuels, and elimination of vertical flow and entrained liquid fall back problems associated with vertical type heaters.

 

The horizontal serpentine straight tube design simplifies tube and refractory repair if required as compared to helical wound or vertical type installations. Drainage of the heater for non-operating periods in freezing weather is simplified in the single tube serpentine design.

 

Feed water Pump and Prime Mover

The feed water pump is normally a positive displacement pump to provide the necessary feed water pressure and flow rate required for the generator.

 

Feed water Preheater

This is normally a double pipe hair pin type heat exchanger used to raise the feed water temperature above the flue gas dew point to prevent condensation of water in the flue gas and the resulting acid corrosion and deposits.

 

Radiant Section

The radiant section is cylindrical with horizontal tubes transposed around the radiant section for equalized heat pick up. The tubes are supported with high alloy tube supports and are free to expand with temperature changes. The radiant section also provides large furnace volume for flexibility in combustion fuel and firing changes. The heat transfer surface in the radiant section normally picks up about 60% to 65% of the overall heat transfer duty. The refractory lined wall provides for reflective heat transfer to the tubes and insulation to reduce heat loss through the chamber wall.

 

Convective Section

The convection section is fabricated from both bare and extended surface tubes. Flue gases from the radiant section enters the convective section flowing across the bare or shock tubes first and then across the extended surface tubes. The convective section normally picks up 35% of 40%, or more, of the overall heat transfer duty. These convective sections are designed to give the desired efficiencies. Mechanically they are designed for easy tube replacement and maintenance. Side covers may be supplied with lay down doors for cleaning if desired.

 

Burner

Burners may be supplied for natural gas, butane, propane, or liquid fuels. Liquid fuels include crude oil. Heavy viscous oils need preheating to provide a viscosity at the burner of 100 to 150 SSU's at the burner nozzle.

 

Controls

The feed water flow rate is controlled by the generator discharge pressure. The burner firing rate is controlled by a metered flow rate signal. This allows the generator to be adjusted to give the desired steam discharge quality. Standard and optional safety limit devices allow unattended operation of the Generator. Certain limits are standard with annunciator lights to indicate reason of shutdown. Other limits are optional along with additional annunciator devices.

 

Water Treatment for Steam Generation

Successful operation of steam generation equipment depends primarily upon a good source of feed water combined with an effective produced water treatment system.

 

Quality of steam generator feed water is of critical importance in steam injection projects. Field experience indicates that most steamer downtime is caused by water treating problems.

 

Although a once-through steam generators can tolerate relatively high amounts of total dissolved solids (TDS), strict adherence to feed water quality requirements is essential. Operating outside a design quality range can result in scale deposition in the water sides of steam generator tubes.

 

Deposition of scale reduces heat transfer, reduces flow though the tubes, and results in tube failure through formation of localized hot spots on the tube walls. Corrosive components of the water also may cause tube failure. Therefore, it is imperative that the feed water be properly conditioned to minimize downtime and costly maintenance.