Oil Processing Unit

The purpose of the oil processing unit is to provide free water removal and coalescence of entrained water particles to allow the oil to meet pipeline specifications for that area in which the unit is recommended and installed. Hetaer treater uses method of heating, chemical action, electrical coalescing and settling for de-emulsifications of oil. All heater treaters utilize the law of gravity to separate the lighter from the heavier components; gas is the lightest, oil is next, then water.

The plant has 6 no of heater treaters and 2 bath heaters with overall annual consumption of about. scm Natural gas which constitutes of about INR annually. Bath heaters are use to preheat the emulsion to ease the mixing and initiation of the de-emulsifying agent. Heated liquid is treated in heater treater to reduce water content. Crude oil with traces of water is dispatched to Mehsana CTF plant for further treatment to meet the specifications of refinery and effluent with traces of oil is sent to ETP where remaining oil is scavenged and water is re pumped into earth for filling up the space thus created.

Heater treater consists of four parts for performing the demulsification process:

1. Inlet degassing section: The produced fluid enters the processing unit above the fire tubes in the inlet degassing section. Free gas is librated from the flow stream and is equalized across the entire degassing and heating areas of the heater treater. Degassing section is separated from the heating section by baffles. The fluid travels downward from degassing area and enters the heating section.
2. Heating section: Heater treater consists of 2 fire tubes which are connected to burners. These fire tubes should be immersed in liquid when the burners are in operation to avoid any damage to the fire tubes due to excessive heating. This is ensured by micro float fitted above the fire tubes. The micro float through an ON-OFF switch the cuts off gas supply to burners whenever the liquid level goes below the fire tubes and switches on the gas supply when the liquid level rises above the fire tubes. The desired temperature is maintained in heater treater by automatic temperature controller.
3. Mechanical section: The clean effluent water discharge valve controller float is fitted in this chamber. This float activates the dump control valve whenever the liquid rises above the level setting. The gas pressure in the inlet and heating sections of the vessel is utilized to move the fluid from the mechanical section into the coalescing section
4. Coalescing section (Electrical section): Electrical heater treater uses high voltage potential on electrodes for coalescing of water droplets in the final phase. Liquid enters this chamber through a distributor tube. As the emulsion passes through the electrical field the water droplets in the emulsion become electrically charged and they move about rapidly and collide with one another. As they collide the droplets grow in size forming larger droplets, until they become large enough to settle.

There are two grids in this chamber which are connected to a transformer which provides 440volts supply. One grid is connected to +Ve and another one is to –Ve which is the body of vessel In this chamber constant level of water is maintained so that the oil coming from the previous chamber is washed before proceeding upwards, so in case there in free water droplets, they will settle. The interface float is connected to the water discharge valve by means of a pneumatic signal. The Clean oil continues to rise to the top of this chamber, where it enters a collector and is discharged through the clean oil outlet control valve.