EFFECTS OF SCALING ON PRESSURE DROP AND TUBE WALL TEMPERATURE OF STEAM INJECTION BOILERS REUSING OIL FIELD PRODUCED WATER

Reusing produced water in steam boilers can save fresh water. However, because of the strong scaling characteristics of produced water, the operation condition of a steam injection boiler varies after reusing the produced water. A computing program is developed to theoretically study the effects of scaling on the pressure drop and the tube wall temperature of a steam injection boiler, and to finally find a key parameter used to monitor the operation safety of a steam injection boiler. The calculation results show that the thermal conductivity of water scale has almost no effect on the pressure drop and that the flow rate has a small effect on the wall temperature. The pressure drop is increased with increase of the scale thickness and flow rate and with decrease of the feed water pressure. While the wall temperature increases when the water scale thickness and feed water pressure increase, the thermal conductivity of water scale decreases. The maximal allowable pressure drop as a key parameter used to guide the boiler cleaning is obtained in this paper. It is not constant but depends on the thermal conductivity of water scale, the feed water pressure, and the flow rate. Once the pressure drop reaches the allowable value, the water scale must be removed by chemical cleaning to ensure the safe operation of a steam injection boiler.