Fired heaters refractories

Indirect-Fired Equipment (Fired Heaters) Indirect-fired combustion equipment (fired heaters) transfers heat across either a metallic or refractory wall separating the flame and products of combustion from the process stream. Examples are heat exchangers (dis-... 

Refractory bricks and cements are needed for equipment operating at high temperatures such as, fired heaters, high-temperature reactors and boilers. 

The MPG process preheats a gaseous feedstock with hot raw gas and an optional fired preheater. Preheat level and installation of the fired heater are determined by energy and cost optimization, which is based on the relative values of feed, fuel gas, and oxygen. Feed gas and oxygen enter the reactor with a minor amount of steam via the gas burner. Gasification occurs in a refractory-lined reactor at temperatures between 1200 and 1400°C.179... 

Indirect or direct fired heaters are widely used in the process industries. Heat loss is kept to a minimum by refractory coatings on the furnace wall. Any material in the fuel that is corrosive or forms excess soot has to be avoided. Usually 20-25% excess air is required for fuel oil vs. 5-10% for gaseous fuel, hence the latter is more economic. Energy in the exit flue gas not used to heat water or a product can be recovered by heat exchangers that generate additional steam or preheat the entering air. 

Camera approach Visually observe the waterwall or refractory wall directly to be certain flames are not touching the walls, causing potentially catastrophic leaks at sites like crude oil (fired) heaters. Besides spotting flames contacting the external tube surface inside the firebox, the camera can also spot other signs of impingement like tubes with a cherry-red color or bulges in the tube walls [12]. 

In another small fired heater, castable refractory was originally installed for a design refractory face temperature of 1,600° F and a furnace shell temperature of 220° F. After several years of operation, the original castable spalled and cracked resulting in a shell temperature of 300° F. A four-inch ceramic refractory blanket was installed that dropped the furnace shell temperature to less than 200° F and reduced heat losses 55 percent. 

Pyrolysis furnace. This unit also performs two operations It preheats the vapor to its reaction temperature, 500°C, and it carries out the pyrolysis reaction. The unit is constructed of refractory brick, with natural gas-fired heaters, and a large bundle of Nickel, Monel, or Inconel tubes, within which the reaction occurs. The tube bundle enters the coolest part of the furnace, the so-called economizer at the top, where the preheating occurs. 

A fired heater or furnace is used to heat large quantities of hydrocarbons for industrial use in a distillation system or reactor. Fired heaters are characterized by three basic designs cabin, cylindrical, and box. The basic components of a furnace include shell, refractory lining, burners, radiant tubes, convective tubes, damper, stack, and firebox. Air and fuel are proportionally balanced as temperatures in the furnace are held constant. Figure 7-12 shows the two standard symbols used for a fired heater or furnace and a boiler. 

When flow is first lost, the fuel to the heater is often automatically tripped off. But the refractory walls continue to radiate heat to the process tubes. It is rather like a large fly wheel. Even after we stop cranking the wheel, the rotational energy stored by the wheel keeps it spinning. Even when all the firing is stopped, the energy stored in the refractory walls continues to radiate heat to the process tubes. 

The crude oil and atmospheric residue are heated in tubular heaters. Oil is pumped through the inside of the tubes contained in a refractory combustion chamber fired with oil or fuel gas in such manner that heat is transferred through the tube wall in part by convection from hot combustion gases and in part by radiation from the incandescent refractory surfaces. 

At the ends of the heaters, tubesheets are provided through which the tubes pass outside the combustion chamber to a header compartment. Tubesheets are generally cast iron with plastic refractory facing on the fire side in sections holding five or six tubes and are bolted to the... 

Newer heaters typically have thin reflective tiles, rather than massive refractory brick walls. Such newer heaters will heat up more rapidly. Also, the process fluid outlet temperature responds more rapidly to changes in the firing rate. This improves the heater outlet temperature control. Perhaps for this reason, it seems that heaters with reflective refractory walls are less subject to process tube coking and shortened heater run lengths. There is also a process, called "alonizing," that increases the reflectivity of older brick refractory heater walls. 

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