Process units fired heaters

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. 

Most FCC units use fired heaters for FCC feed final preheat. The feed preheater provides control over the catalyst-to-oil ratio, a key-variable in the process. In units where the air blower is constrained. 

J. Use of fired heaters the presence of boilers or furnaces, heated by the combustion of fuels, increases the probability of ignition should a leak of flammable material occur from a process unit. The risk involved will depend on the siting of the fired equipment and the flash point of the process material. The factor to apply is determined with reference to Figure 6 in the Dow Guide. 

The most logical place to begin is to size the furnaces and direct-fired heaters. Often the chemistry of the process has dictated the conditions, but frequently they can be modified in order to conserve energy usage. The burning of waste materials should also be considered as a means of both disposing of unwanted by-products and reducing fuel requirements. For each of these units, the amount of fuel needed per pound of product should be determined. 

There are distinct differences between Mahoney s and Instone s data (Table 21) concerning fired heaters and boilers. A possible reason for this is that Instone has analysed the process units involved in large losses and Mahoney has analysed the primary causes of large losses. It is known that heaters and boilers are the... 

Fired equipment will have penalties, if the material in process unit near the air intake of fired heater could be released above its boiling point, if the material is a combustible dust, or if the material could be released above its boiling point. The penalty depends on the distance from the possible leak source and it varies between 0.1 and 1.0. For instance the distance of 15 m gives the penalties 0.27 (above the flash point) and 0.60 (above the boiling point). Any situation involving a material processed below its flash point receives no penalty. 

Fired heaters are extensively used in the oil and gas industry to process the raw materials into usable products in a variety of processes. Fuel gas is normally used to fire the units which heat process fluids. Control of the burner system is critical in order to avoid firebox explosions and uncontrolled heater fires due to malfunctions and deterioration of the heat transfer tubes. Microprocessor computers are used to manage and control the burner system. 

A major fire erupted in a nonflammable solvents manufacturing unit in a U.S. Gulf Coast chemical complex. A furnace tube in a natural-gas-fired heater ruptured due to overheating. At least 1,800 gallons (6,800 liters) of a combustible heat transfer fluid spilled and burned intensely. Within about 25 minutes, the intense hot fire damaged four levels of structure and associated process equipment. The plant on-site emergency squad quickly and properly responded. However, the price tag for short-lived incident was over 1.5 million in direct property damage and over 4 million in business interruption (U.S. 1979). Fortunately, there were no injuries. [2]... 

Within 20 to 35 minutes after the heater was fired, a fire-water sprinkler system tripped. A heater flame failure alarm occurred a short time later. Witnesses stated flames were over 50-ft. (15 m) high in approximately five seconds after the tube ruptured. The fire damages were the greatest on the third and fourth levels of the process unit as 10- to 12-mph winds carried flames and destructive heat into the unit. There was an excellent response by the emergency squad with eight hose lines reinforcing the fixed fire-water deluge systems. 

The first methanol was vaporised and reacted to produce hydrocarbons in the first conversion reactor as anticipated. However, the hi(J> prepane production due to high initial catalyst activity was not simulated. The actual unit heat balance was therefore not as predicted with the result that the process fired heater duty was significantly higher than expected. The startup heater which was in service to provide additional methanol superheat upstream of the DME reactor during startup was not taken off-line towards the end of startup as predicted. 

Based on the tuned models, equipment performance could be evaluated and compared with design. The models could then be readily adapted to simulate an additional process fired heater (to unload the methanol superheater) and to evaluate it s inpact on the overall MTG unit performance. Multiple case studies were performed to determine optimum heater size with regard to maximising heat recovery and providing unit heat balance flexibility. The additional heat balance flexibility allows the ZSM-5 catalyst outlet temperature to be reduced hence maximising gasoline yield. 

Direct Fired Process Heaters 1 -Final Stage Process Units... 

A fired heater or furnace is a device used primarily to heat large quantities of hydrocarbons. These systems are very expensive and complex and require a well-trained and dedicated staff. A process technician assigned to these units studies the basic components of the system, traces out each major flow path, and works closely with senior technicians until he or she is qualified to operate the equipment. Modern control instrumentation and high-tech control rooms are designed to monitor and control all vital processes. 

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