The Heat Is On

If you need heat, you need us. With that said, let’s dive right in on this very hot topic. Starting off with the star of the show, fuel gas. Fuel gas conditioning systems typically consist of a scrubber vessel or knock-out drum, filter-separator, heaters, pressure reduction, emergency/operational valves, and (flow) metering. The systems are often placed downstream of the production header or glycol contactor/separator.

It is commonly used in the power generating industry as an energy source for turbines. Before the fuel gas is burned in the turbines it needs to be treated to ensure the removal of solid, liquid and gas contaminants. A fuel gas conditioning system commonly consists of the following components: a pre-heater, a pressure regulation valve, two high efficiency coalescing filter elements and a super heater.

Types of Heaters

With that said, there are three common basic types of heaters that are available, each with its own advantages and disadvantages.

Electrical Heaters

Electrical heaters are the most convenient type of process in which electrical energy is converted to heat energy. Common applications include space heating, cooking, water heating and industrial processes. An electric heater is an electrical device that converts an electric current into heat. The heating element inside every electric heater is an electrical resistor, and works on the principle of Joule heating, an electric current passing through a resistor will convert that electrical energy into heat energy. Most modern electric heating devices use nichrome wire as the active element, the heating element, depicted on the right, uses nichrome wire supported by ceramic insulators. Methods of heating is to be studied in each application required

Electric infrared radiant heating uses heating elements that reach a high temperature. The element is usually packaged inside a glass envelope resembling a light bulb and with a reflector to direct the energy output away from the body of the heater. The element emits infrared radiation that travels through air or space until it hits an absorbing surface, where it is partially converted to heat and partially reflected. This heat directly warms people and objects in the room, rather than warming the air. This style of heater is particularly useful in areas through which unheated air flows.

In a convection heater, the heating element heats the air in contact with it by thermal conduction. Hot air is less dense than cool air, so it rises due to buoyancy, allowing more cool air to flow in to take its place. This sets up a convection current of hot air that rises from the heater, heats up the surrounding space, cools and then repeats the cycle. These heaters are sometimes filled with oil or thermal fluid. They are ideally suited for heating a closed space. They operate silently and have a lower risk of ignition hazard if they make unintended contact with furnishings compared to radiant electric heaters.

Thermal conduction is the transfer of internal energy by microscopic collisions of particles and the movement of electrons within a body. The colliding particles, which include molecules, atoms, and electrons, transfer disorganized microscopic kinetic and potential energy, jointly known as internal energy. Conduction takes place in all phases: solid, liquid, and gas. Heat spontaneously flows from a hotter to a colder body. For example, heat is conducted from the hotplate of an electric stove to the bottom of a saucepan in contact with it. In the absence of an opposing external driving energy source, within a body or between bodies, temperature differences decay over time, and thermal equilibrium is approached, temperature becoming more uniform.

The efficiency of any system depends on the definition of the boundaries of the system. For electrical energy, the efficiency of electric space heating is 100% because all purchased energy is converted to heat. The cost is the lowest of the three types, but the operating expense is, therefore, the highest, whereas maintenance costs are relatively low. The electrical heater is simple in construction, compact, and requires a smaller foundation. Heating elements can be easily replaced and no intermediate heat transfer fluid is required.

Gas or Oil-fired Heaters

Gas- or oil-fired heaters are readily available and already in use throughout the world. Fuel Fired Heaters are heat generation units consisting of gas or oil-fired duct furnaces, unit heaters, radiant heaters, direct fired heaters, indirect fired heaters and gas fired make up air units. They are self-contained, automatically controlled, and designed to operate and transfer heat by using a burner, fan and heat exchanger. In colder climates, a mixture of ethylene glycol and water or equivalent prevents freezing, elevates the boiling temperature of the water, and reduces the heat exchanger surface area. The thermal efficiency of these units is reasonably high; about 80% of the heat generated is transferred to the gas and the remainder is discharged in the flue gas. Heat added to the gas fuel, however, reduces the quantity of fuel required by the gas turbine and offsets the fuel required by the heater to some extent.

Fuel Fired Heaters can be mounted in an elevated position from which the heated air is directed downward into installed ducts and used in conjunction with a supply fan and mounted in an elevated position, radiating heat downwards. Typical applications include warehouses, manufacturing areas, or any space that only requires heating not serviced by a building`s main HVAC system. Larger foundations are required for this type of heater, and several burners may be required in order to provide improved thermal response and turndown capabilities. Operating costs are significantly lower than an electrical heater, but maintenance and capital costs are higher. Difficulty in tracking rapid fuel demand changes of the gas turbine may be an issue for peaking units or during start-up.

Waste-heat-fired Fuel Heaters

Waste-heat-fired fuel heaters are an option for combined cycle units where recover the heat from exhaust streams emitted by gas turbines, waste incinerators, CO boilers or any other fired equipment. They can be integrated into a complete process heat transfer system. These units can be installed in tandem with heaters and can be used to heat organic thermal fluids or other liquid or gaseous media. With the high cost and environmental impact of fossil fuels, heat energy is a precious commodity that cannot be wasted. Any exhaust gas stream with temperatures above 250°F has the potential for significant waste heat recovery. Common of waste heat energy can be found in almost any facility and are easy to locate. Typical examples include plant process heating, combustion air pre-heating, boiler feedwater pre-heating, and building heat.

These systems can also be used for the incineration of organic waste, solvents, process off-gases containing hydrogen and salt-laden wastewater. The exhaust gases are used in waste-heat trains to heat and partially vaporise crude oil in several tube bundles connected in series, and also to heat process water or steam. Low-grade heat (hot water) may be readily available. The advantage of this type of heater is that no fuel penalty happens and the overall thermal efficiency may be increased. The disadvantages include having a higher capital cost, increased maintenance, and installation costs for larger foundations. This type of a system is more suited for base-loaded units because of lack of heating during start-up. Usually, a small supplementary boiler is used for start-up conditions. Construction is of the tube and shell type and is heavier than the indirect-fired heater to accommodate the 400 + psia/28 + bar pressurized water supply.

Dpstar Group
No 35, Jalan OP ½, Pusat Perdagangan One Puchong,
Off Jalan Puchong, 47160 Puchong,
Selangor Darul Ehsan, Malaysia.
Email: [email protected]

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