Fired heaters analysis

Table 2. Lost-Work Analysis for a Fired Heater...

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. 

The fuel gas to a fired heater is controlled by a BPCS control function (function TIC-1), which throttles a fuel control valve, CV-1, as shown in Figure F-3. A hazard analysis was performed to identify process hazards and to determine whether the safeguards were sufficient to mitigate the process hazards. The team determined that when the heater was firing hard, a low-pass flow through the tubes could result in a high firebox temperature with the potential for tube rupture, furnace fire and structural damage to the furnace. 

Once a decision is made to eliminate these two bottlenecks (fired heater and separation system), the analysis of reactor behavior could be modified to consider a number of secondary effects. The case study did not consider the effect of increasing reactor flowrates on the heat transfer coefficient (gas-phase resistance dominates). The inpact of the increased pressure drop over the reactor was not examined. These options were not necessary to confirm that the reactor is capable of providing a 50% increase in acetone production. The option of increasing the HTM flowrate was not appraised. 

Orsat analysis A measurement of the oxygen, carbon dioxide, and carbon monoxide in a mixture of gases, usually from the exhaust of combustion processes such as boilers, furnaces, fired heaters, and combustion engines. Named after its inventor H. Orsat in 1873, it involves absorption of the gases onto materials contained in pipette tubes. The method has been largely replaced by other techniques. 

Many of the conservation measures require detailed process analysis plus optimization. For example, the efficient firing of fuel (category 1) is extremely important in all applications. For any rate of fuel combustion, a theoretical quantity of air (for complete combustion to carbon dioxide and water vapor) exists under which the most efficient combustion occurs. Reduction of the amount of air available leads to incomplete combustion and a rapid decrease in efficiency. In addition, carbon particles may be formed that can lead to accelerated fouling of heater tube surfaces. To allow for small variations in fuel composition and flow rate and in the air flow rates that inevitably occur in industrial practice, it is usually desirable to aim for operation with a small amount of excess air, say 5 to 10 percent, above the theoretical amount for complete combustion. Too much excess air, however, leads to increased sensible heat losses through the stack gas. 

Low—Temperature Processes. A r esidential water heater provides a striking example of how a simplified availability analysis of efficiency can be applied. Typically, a gas- or oil-fired water... 

The analysis concerns potential hazardous scenario in vacuum heater which can lead to serious accident in case of inadequate or erroneous hmnan reactions to event occurred. This scenario assmnes malfunction of the control system what will result in sudden and undesirable shutdown of the one of the valves supplying the burner with fuel due to its low flow. This simation indicates the threat of fuel temperature rise. The outcome in a worst case is fire inside the heater what can leads to its destruction. 

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