Calrod^TM Heaters Application in Gas and Oil Industry
Starting from the past century, petroleum has gradually becoming a primary resource for human being. This valuation product is produced via multiple units from the oil refinery process. In overall, the crude oil is separated into valuable end-products via fractional distillation in a separation column under different multiple boiling points. In order to maximize the hydrocarbons heat transfer, the crude oil inlet usually enters near the bottom of the distillation column at a high temperature of over 350°C (Fig. 1).

Figure 1 - Fractional Distillation Unit for a Refinery Process
 

In order to feed this inlet at a high temperature, a furnace or a boiler is generally installed prior the distillation unit. A pump unit is required to transport the crude oil from the storage tank to the furnace. However, viscosity of the tank crude oil may change due to ambient weather condition. If the liquid viscosity increases, the pumping unit will require longer time than the regular operation time and this would cause an overall delay in the process. In order to avoid unnecessary delays and other related cost, pre-heating the crude oil is recommended prior the distillation processes.
Calrod^TM heater is the perfect solution for maintaining the temperature of the crude oil storing unit for any petroleum refinery. Calrod^TM type is an electric tubular heater which is normally used to heat tanks or equipment of various sizes. Calrod^TM heater composes of multiple compact and durable tubular elements that are clamped and immersed into a process unit (Fig. 2). One of the special characteristics of the tubular heater is the variability of its shape.



Figure 2 - Tubular Heating Elements immersed in a Liquid Tank

WATTCO^TM tubular heaters are manufactured to be compatible to nearly all type of applications while oil storage tank is no exception. For example, the variability of the sheath material, shape and size can be adjusted to fit any storage tank size whether it is for crude oil or end-product use (Fig. 3). Custom bending option is also available upon request.



Figure 3 - Calrod^TM Tubular Heater Manufactured by WATTCO^TM

Inside of each tubular element, it consists of a Nickel Chromium wire, as the resistor, enrobed with compacted Magnesium Oxide for insulation. These parts are protected by an enclosed sheath material which can be steel, stainless steel, copper, Incoloy^TM or Titanium depending on application (Fig. 4). For oil heating, steel sheath is recommended for the best performance. Once the heater is installed in the tank, and after starting the power, the radiant heat is generated from the resistance wire onto the surface of the tubular elements. The heat generated from the tubular heater spreads evenly around the liquid inside the tank. In order to ensure the heating to not initiate any unwanted chemical reaction inside the tank, a temperature controller is available to maintain a safe internal environment inside the unit.



Figure 4 - Tubular Elements - Features & Components
Calrod^TM tubular heaters are not limited to crude oil heating usage, they can be used for products after the distillation process as well. For example, heavier fuel oil residuals obtained at the lower section of the distillation tower (Fig. 1) require pre-heating before use in order to maintain the proper viscosity during the storage period ^[1]. For fuel oil type no. 5 and no. 6 (Classification according to the American Society for Testing and Materials), the viscosity gradually increases when storing at room temperature. This would cause a poor atomization during the applications such as generating power for an industrial plant ^[2]. A temperature range from 77 to 100 °C is recommended to maintain a proper viscosity for the appropriate atomization ^[1]. Calrod^TM tubular elements are suitable for this type of application. The bending and material type of the WATTCO^TM tubular heaters are adjusted to fit any tank size, for any storing chemical substance, in a cost effective way.
The tubular elements manufactured by WATTCO^TM are suitable for not only for oil but also for almost any liquid or gas. One of the popular applications with Calrod^TM heater is the water pre-heating process. There are many units in the petroleum process that requires pre-heated water as an utility, for example, the heat exchanger units. The tubular heaters can be used as pre-heating unit for the water reservoir (Fig. 5) and with a pump unit, the pre-heated liquid can be transported into the refinery process as a utility stream.

Figure 5 - Tubular Heater (with screw plug) Immersed in a Water Tank
The selection of sheath material, shape or rating for our Calrod^TM heater design are based on your target application. WATTCO^TM's technical consultants are always available for inquiries should you have any questions or concerns about the application of our Calrod^TM tubular heaters.
 
References
1. Perry, Robert H., Green, Don W. Perry's Chemical Engineers' Handbook 7th edition (1997) McGraw Hill, ISBN 978-0070498419, p.27(8)-27(10)
 
2. Schmidt, Paul F. Fuel Oil Manual3rd Edition (1986) Industrial Press Inc.,U.S., ISBN 978-0831130145, p. 23
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