Fired heaters temperature

When the column is reboiled by a fired heaters, temperature pinches rarely (if at all) occur (60). 

Rgur 9.5 Fired-heater temperature controls, (a) Temperature controller will increase heat input upon pump failure. (6) Temperature controller will lower heat input upon pump failure. 

Fresh reducing gas is generated by reforming natural gas with steam. The natural gas is heated in a recuperator, desulfurized to less than 1 ppm sulfur, mixed with superheated steam, further preheated to 620°C in another recuperator, then reformed in alloy tubes filled with nickel-based catalyst at a temperature of 830°C. The reformed gas is quenched to remove water vapor, mixed with clean recycled top gas from the shaft furnace, reheated to 925°C in an indirect fired heater, and injected into the shaft furnace. For high (above 92%) metallization a CO2 removal unit is added in the top gas recycle line in order to upgrade the quaUty of the recycled top gas and reducing gas. 

Fired Heater as a Heat-Exchangee System. Improved efficiency in fired heaters has tended to focus on heat lost with the stack gases. When stack temperatures exceed 150°C, such attention is proper, but other losses can be much bigger when viewed from a lost-work perspective. For example, a reformer lost-work analysis by Monsanto gave the breakdown shown in Table 2. 

Simple heat losses through the furnace walls are also significant. This follows from the high temperatures and large size of fired heaters, but these losses are not inevitable. In an optimized system, losses through insulation (1) are roughly proportional to... 

Equipment Tests. Procedures for rigorous, detailed efficiency determination are available (ASME Test Codes) but are rarely used. For the objective of defining conservation potentials, relatively simple measurements are adequate. For fired heaters, stack temperature and excess O2 ia stack should be measured for turbiaes, pressures (ia and out) and temperatures (ia and out) are needed. 

In extremely cold environments, engines can quickly become difficult, sometimes nearly impossible, to start. If ordinary gasoline- or diesel-oil-fired heaters are used, the coolant circulation pump, air fan, etc, must be powered from the vehicle s batteries, thus curtailing the time the system can be used, especially at very low temperatures when it is needed the most. By adding PbTe thermoelectrics to such heater systems, about 2% of their thermal output can be turned into electricity to mn the heater s electronics, fuel pump, combustion fan, and coolant circulation pump, with stiH sufficient power left over to keep the vehicle s battery fliUy charged. The market for such units is in the hundreds of thousands if manufacturing costs can be reduced. 

Petroleum products may be treated with various solvents for the removal by selective solubility of undesirable constituents or for the recovery of by-products. The solvent and solute must be separated to yield the desired product and to recover the solvent for reuse. The solvents normally boil at a lower temperature than the products from which they are to be removed and so are generally distilled off as overhead products. The pipe stills used for this service may be single-stage or multi-stage units, depending on the service involved. Some solvents can be removed by the use of steam heated stills. In other cases, the high temperature required necessitates the use of fired heaters and vacuum towers. 

The next chapter discusses the use of LTX units to melt the hydrates as they form, and the use of indirect fired heaters to keep the gas temperature above the hydrate formation temperature. Chapter 8 describes processes and equipment to dehydrate the gas and keep free water from forming. 

Indirect fired heaters (sometimes called line heaters) heat the gas stream before and/or after the choke so that the gas is maintained above the hydrate temperature. Indirect fired heaters can also be used to heat crude oil for treating, heat a hot fluid circulating medium (heat medium) that is used to provide process heat, etc. 

Where gas or oil appliances are used for heating and installed within the heated space, between 70 per cent and 90 per cent of the total energy content of the fuel input will be converted into useful heat. Table 27.15 gives particulars of some gas-fired equipment types and Table 27.16 gives similar details for some oil-fired heaters. The first three types of equipment detailed in Table 27.15 and the first two in Table 27.16 are usually used for local warming of individuals rather than to provide a particular temperature throughout the space. 

The main stationary sources of NO are gas turbines, fired heaters, power generation plants, and, of course, the FCC. The amount of NO produced is a function of residence time and combustion temperature. Combustion temperature is influenced by fuel composition. 

Fired heaters radiant rate, 12,000 Btu/(hr)(sqft) convection rate, 4000 cold oil tube velocity, 6 ft/sec approx equal transfers of heat in the two sections thermal efficiency 70-75% flue gas temperature 250-350°F above feed inlet stack gas temperature 650-950°F. 

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

When high temperatures and high flow rates are required, fired-heaters are used. Fired heaters are directly heated by the products of combustion of a fuel. The capacity of fired heaters ranges from 3 to 100 MW. 

Modem fired heaters operate at thermal efficiencies of between 80 to 90 per cent, depending on the fuel and the excess air requirement. In some applications additional excess air may be used to reduce the flame temperature, to avoid overheating of the tubes. 

In practice, the efficiency of a fired heater is controlled by monitoring the oxygen concentration in the combustion products in addition to the stack gas temperature. Dampers are used to manipulate the air supply. By tying the measuring instruments into a feedback loop with the mechanical equipment, optimization of operations can take place in real time to account for variations in the fuel flow rate or heating value. 

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