Fired heaters capacity

Fired heater capacity for critical processes is usually pushed hard for more production and thus the fired heaters are operated near or at the operation limits. It is essential to make sure the fired heater is running in a safe and reliable manner with the following key operating reliability parameters within acceptable limits ... 

This investigation showed there are a number of options that can effect a significant increase in acetone production. A 50% increase in capacity can be obtained from the reactor. All options require an increase in fired heater capacity. 

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. 

Process furnace or direct-fired heater Design type, absorbed heat duty, pressure, tube material, capacity... 

The inlet pressure of 27 bar into the HP turbine was selected as a compromise. The largest pressure for closed cycle gas turbines with air was 40 bar at that time. Conditions for a nuclear heated plant provided with a helium-turbine were foreseen as about 60 bar, a helium-temperature of 850 C and a plant capacity of 300 MWe. The low pressure turbine was selected to deliver power at a frequency of 50 Hz or 3000 rpm and is connected by a gear arrangement to the high pressure turbine shaft that rotates at 5500 rpm. It has dimensions and stress loadings for the rotor shaft for the blades and for the mrbine housing which are very similar to those of a 300 MW helium-turbine plant considered at the time as the reference size. In addition to optimization requirements a reason for the limitation of the primary pressure was the permissible stresses for the material of the mbes of the fossil-fired heater. 

A fired heater is not operated uniformly over the entire run as it eould run light in turndown operation and harder in full capacity and toward the end of run for reaction heaters. To estimate the effects of changing tube wall temperature, corrosion rates, and pressure, a metaUurgic examination can be applied to estimate the remaining life of tubes. Knowing the tube life not only prevents premature tube failure, but also identihes the need for metal upgrade if the operating skin temperature increases over time. 

In general, fired heaters are revamped for capacity expansion, process conversion changes, energy efficiency, and NO reduction. For capacity expansion revamps, the type of limitation for the revamp is usually the same as for the original design. In conversion revamps, one type of process technology is converted to another. Thus, in conversion revamps, a heater designed for one service may be used in a new service. Therefore, the type of heater limitation may be different for the new service. 

All options to increase acetone production require an increase in capacity of the fired heater (or addition of a new fired heater). Therefore, the fired heater is likely to represent a bottleneck to increased production. Fired heaters are expensive, and it is not likely that the current heater was oversized enough to provide a 50% increase in heat duty. Until this bottleneck is removed, the additional acetone production required cannot be obtained. 

The maximum allowable superheat coil outlet temperature is 700°F to protect the carbon steel tubes from failure. At low steam generation rates, I have seen furnace firing rates and thus heater charge rates reduced to keep from overheating the steam above 700°F. If the steam is not used eventually to drive turbines, or as a reactant in a catalytic process (steam-methane reformer for or NHj production), then the heater capacity is being limited for no logical reason. 

The above procedure allows the production facility engineer to choose the major sizing parameters of heater-treaters when little or no laboratory data are available. This procedure does not give the overall dimensions of the treater, which must include inlet gas separation and FWKO sections. However, it does provide a method for specifying a fire-tube capacity and a minimum size for the coalescing section (where the treating actually occurs) and provides the engineer with the tools necessary to evaluate specific vendor proposals. 

Fig. 14. Production diagram of vinyltrichlorosilane 1,3- tanks 2 -evaporator 4, 5 - rotameters 6, 12 - towers with CaCl2 7 - heater 8 - reactor 9 - expander 10, 13 - coolers 11- fire-resistant apparatus 14 - buffer capacity 15 - absorber 16 -collector.

Shut down burners when the heater is firing at reduced rates. Burners work more efficiently when operating close to their design capacity. Don t forget to shut the air registers on the idle burners. 

This heat transfer method is mainly used to enhance the drying capacity in coaters when the web is wet Infrared heaters are usually gas fired. The gas heats a mesh to a temperature of about 900 to 1100 °C. The low thermal inertia of the mesh allows fast control of the mesh temperature and the heating rate as well as preventing fires in the case of sheet breaks. In some cases electrical heaters are in use with temperatures up to about 700 °C, exhibiting a fast cool down of the emitter plates. Infrared drying units need sufficient air flow in order to carry off the evaporated water and to prevent coat quality problems. 

Figure 1.44 provides standard dimensions, pressure ratings, and fire-box ratings for vertical and horizontal heater-treaters. Figure 1.45 is a typical horizontal heater-treater table supplied by an equipment manufacturer. Figure 1.46 is a typical vertical heater-treater capacity table supplied by an equipment manufacturer. 

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