Heater-treaters coalescing section

Fig. 9—Graph establishes dimensional ranges of horizontal heater-treater an example problem Diameter and coalescing section dimensions must fall outside shaded area for adequate treatment tame...

The most commonly used single-well treater is the vertical heater-treater, which is shown in Figure 1.7. The vertical heater-treater consists of four major sections gas separation, FWKO, heating and water-wash, and coalescing-settling sections. Incoming fluid enters the top of the treater into a gas separation section, where gas separates from the liquid and leaves through the gas line. Care must be exercised to size this section so that it has adequate dimensions to separate the gas from the inlet flow. If the treater is located downstream of a separator, the gas separation section can be very small. The gas separation section should have an inlet diverter and a mist extractor. 

As shown in Figure 1.14, a vane-type mist extractor removes the hq-uid mist before the gas leaves the treater. The gas liberated when crude oil is heated may create a problem in the treater if it is not adequately designed. In vertical heater-treaters the gas rises through the coalescing section. If a great deal of gas is liberated, it can create enough turbulence and disturbance to inhibit coalescence. Equally important is the fact that small gas bubbles have an attraction for surface-active material and hence water droplets. Thus, they tend to keep... 

For most multi-well flow streams, horizontal heater-treaters are normally required. Figure 1.16 shows a simplified schematic of a typical horizontal heater-treater. Design details vary from manufacturer to manufacturer, but the principles are the same. The horizontal heater-treater consists of three major sections front (heating and water-wash), oil surge chamber, and coalescing sections. 

Most horizontal heater-treaters built today do not use fire-tubes. Heat is added to the emulsion in a heat exchanger before the emulsion enters the treater. In these cases the inlet section of the treater can be fairly short because its main purpose is to degas the emulsion before it flows to the coalescing section. 

Some heater-treaters are designed with only the coalescing section. In these cases the inlet is pumped through a heat exchanger to a treater that operates at a high enough pressme to keep the oil above its bubble-point. Thus, the gas will not evolve in the coalescing section of the treater. 

Some horizontal heater-treaters add an electrostatic grid in the coalescing section. Figure 1.25 illustrates a simplified schematic of a typical horizontal electrostatic treater. The flow path in an electrostatic heater-treater is basically the same as in a horizontal heater-treater, except that an electrostatic grid is included in the coalescing-settling section, which helps to promote coalescence of the water droplets. 

Figure 1.28 shows one variation of the electrostatic heater-treater where the vessel only contains the coalescing section with the electrostatic grid. Units configured in this manner are called "oil dehydrators." They are capable of higher handling volumes and use separate... 

The above procedure allows the production facility engineer to choose the major sizing parameters of heater-treaters when little or no laboratory data are available. This procedure does not give the overall dimensions of the treater, which must include inlet gas separation and FWKO sections. However, it does provide a method for specifying a fire-tube capacity and a minimum size for the coalescing section (where the treating actually occurs) and provides the engineer with the tools necessary to evaluate specific vendor proposals. 

---