Reactor external fire

The hydrocarbon gas feedstock and Hquid sulfur are separately preheated in an externally fired tubular heater. When the gas reaches 480—650°C, it joins the vaporized sulfur. A special venturi nozzle can be used for mixing the two streams (81). The mixed stream flows through a radiantly-heated pipe cod, where some reaction takes place, before entering an adiabatic catalytic reactor. In the adiabatic reactor, the reaction goes to over 90% completion at a temperature of 580—635°C and a pressure of approximately 250—500 kPa (2.5—5.0 atm). Heater tubes are constmcted from high alloy stainless steel and reportedly must be replaced every 2—3 years (79,82—84). Furnaces are generally fired with natural gas or refinery gas, and heat transfer to the tube coil occurs primarily by radiation with no direct contact of the flames on the tubes. Design of the furnace is critical to achieve uniform heat around the tubes to avoid rapid corrosion at "hot spots."... 

The external events PSA was based on standard methods used for commercial reactor PSAs, Fire risk was estimated from commercial nuclear power plant data combined with industrial fire information. The seismic hazard was evaluated using a combination of the EPRI and LLNL ( UREG/CR-.3250) databases. Wind hazards were analyzed by EQE, Inc., using NRC-based nicihodulogy. 

External fire could cause an emergency by overloading the normal reactor systems that are operating properly. 

The experiments were conducted at ambient temperatures up to 200°C. Hence, they do not relate to the high temperatures encountered if the reactor were exposed to an external fire. 

The hydrogen producing reactions are limited by thermodynamic equilibrium. The reactions must take place under carefully controlled external firing, with heat transfer taking place from the combustion gas in the firebox to the process gas in the catalyst-filled tubes. Carbon monoxide in the product gas is converted almost completely to hydrogen in the downstream catalytic reactor. 

This example uses the same relief sizing problem as has been presented in 6.5.1. A relief system is to be sized for a relief pressure of 2.0 bara and a maximum accumulated pressure of 2.6 bara with a 793 kg charge in a 2 m3 reactor. However, in this case, the runaway is expected to be caused by external fire. Also, vapour/ liquid disengagement is not expected. 

Steam reforming refers to the endothermic, catalytic conversion of light hydrocarbons (methane to gasoline) in the presence of steam [see Eq. (5.1)]. The reforming reaction takes place across a nickel catalyst that is packed in tubes in an externally-fired, tubular furnace (the Primary Reformer). The lined chamber reactor is called the secondary reformer , and this is where hot process air is added to introduce nitrogen into the process. Typical reaction conditions in the Primary Reformer are 700°C to 830°C and 15 to 40 bar46. 

Description The fresh paraffin feedstock is combined with paraffin recycle and internally generated steam. After preheating, the feed is sent to the reaction section. This section consists of an externally fired tubular fixed-bed reactor (Uhde reformer) connected in series with an adiabatic fixed-bed oxyreactor (secondary reformer type). In the reformer, the endothermic dehydrogenation reaction takes place over a proprietary, noble metal catalyst. 

Rupture disks are often used upstream of relief valves to protect the relief valve from corrosion or to reduce losses due to relief valve leakage. Large rupture disks are also used in situations that require very fast response time or high relieving load (for example, reactor runaway and external fire cases). They are also used in situations in which pressure is intentionally reduced below the operating pressure for safety reasons. 

Because of the large restricted area around the facilities and the remote location of the site, no industrial facility accidents are credible. The hazards associated vrith military accidents (i.e., expiosions, aircraft crash) are considered separately in the discussions of Aircraft Impacts, Chemical/Toxic Releases, External Explosions, and Missiles. Accidents in adjacent facilities in TA-V, such as the adjacent reactor fadlities, could have limited impact on the HCF as those faciiities are in separate buildings or physically separated from the HCF in an adjoining building. The nuciear faciiities have been designed to prevent accidents with the hazardous material in one faciiity from affecting the material in another facility. Thus, the impact of those adjacent faciiities on the HCF would likely be the same or less than External Fires. 

In the case of a bush or forest fire, there is generally sufficient time for the operators to bring the reactor into a safe state and to take appropriate protection measures. The potential impacts of external fires are the intake of smoke via the ventilation system and a loss of offsite power. 

Flue Gas Discharge. As outlined in the section Application of Synthesis Gas, the combustion management of a synthesis gas reactor is of paramount importance. The heat flux required is, in externally fired units, supplied by hot flue gas, resulting from combustion. The flow of this flue gas in the combustion... 

Seo ct al. reported on the development and operation of a 100-kW natural gas fuel processor, tvhich tvas developed for a molten carbonate fuel cell [609]. The molten carbonate fuel cell does not require any carbon monoxide clean-up (see Section 2.3.2), and thus the system consisted merely of a burner to supply the steam reformer, a compressor, heat-exchangers, the desulfurisation stage and the reformer itself. The reformer was built by relying on conventional technology with tubular reactors top-fired externally from the natural gas burner. The 16 steam reformer tubes shown in Figure 9.33 were operated at a S/C ratio of 2.6 and 3-bar pressure, while the design operating temperature was 700 °C. Seo et al. reported that the efficiency of their system was still too low. Therefore, an improved version of the fuel processor is under development. 

The external events considered in this report include both natural hazards and human induced hazards from sources external to the site or external to the safety related buildings. Explicit reference is made to the most common external event scenarios considered in the design of research reactors (earthquake, wind, precipitation (snow, rain, hail), flood, explosions and aircraft crash, external fire), for which special recommendations are provided. However, the approach to the safety evaluation discussed in the present publication can be applied to any scenario included in the facility s safety analysis report. 

External fire Ventilation system Reactor in shutdown state Low Monitoring system warning... 

The third research line deals with reforming the reactor configuration. In particular, three major areas are being developed (1) transferring from a fixed-bed reactor to a fluidized-bed reactor (2) use of membrane technology and (3) changing from external firing to internal heat supply. 

FIG. 23-1 Heat transfer to stirred tank reactors, a) Jacket, (h) Internal coils, (c) Internal tubes, (d) External heat exchanger, (e) External reflux condenser. if) Fired heater. (Walas, Reaction Kinetics for Chemical Engineers, McGraw-Hill, 1959). 

Figure 17.13. Multibed catalytic reactors (a) adiabatic (b) interbed coldshot injection (c) shell and tube (d) built-in interbed heat exchanger (e) external interbed exchanger (f) autothermal shell, outside influent-effluent heat exchanger (g) multishell adiabatic reactor with interstage fired heaters (h) platinum-catalyst, fixed bed reformer for 5000 bpsd charge rate reactors 1 and 2 are 5.5 ft dia by 9.5 ft high and reactor 3 is 6.5 x 12.0 ft.

Figure 17.33. Heat transfer to stirred-tank reactors (a) jacket (b) internal coils (c) internal tubes (d) external heat exchanger (e) external reflux condenser (f) fired heater (Walas, 1959).

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