Heat removal system

FGG Gatalyst Goolers. Heat-removal systems have been used in commercial FCCUs since the early 1940s. The three basic designs are internal regenerator bed coils, external cods with ddute-phase upflow, and external cods with dense-phase downflow. 

Functional and hardware relationships between systems are considered in selecting the order of event tree headings. Systems that depend on the operation of other systems in order to perform their function should be listed after the other systems. For example, the decay-heat removal system... 

Manifold barriers confine the radioactivity to the 1) ceramic fuel pellet 2) clad 3) cooling water, as demonstrated by the TMI-2 accident 4) primary cooling loop 5) containment and 6) separation from the public by siting. Further protection is provided by engineered safety systems pressurizers, depressurization, low pressure injection, high pressure injection and residmil heat removal systems. 

Prevent containment ova-pressure Residual heat removal system Shutdown cooling system Containment spray system... 

The AP600 passive safety system includes subsystems for safety injection, residual heat removal, containment cooling, and control room habitability under emergency conditions. Several of these aspects are in existing nuclear plants such as accumulators, isolation condensers as natural-circulation closed loop heat removal systems (in early BWRs), automatic depressurization systems (ADS - in BWRs) and spargers (in BWRs). 

Reactions occurring in FTS are essentially bond forming, and they release a large amount of heat. This requires an efficient heat removal system. 

As with other oxidation reactions, ammoxidation of propylene is highly exothermic, so an efficient heat removal system is essential. 

Narrow range of coke yields unless some heat removal system is incorporated... 

Polymerization of methyl methacrylate to Plexiglas is done in the bulk process. High pressure polymerization of ethylene is done this way also. But other addition polymerizations frequently become too exothermic and without adequate heat removal system, the reaction tends to run away from optimum conditions. 

During normal operation, the main circulator transports hot helium at 1266°F (686°C) from the bottom of the core to the steam generator which, in turn, produces superheated steam at I005°F (541 °C) and 2500 psia. The cold helium at 496°F (258°C) is returned to the top of the reactor core. During normal shutdown and refueling, the non-safety auxiliary shutdown heat removal system removes core afterheat if the main heat transport system is not operational. 

The setpoint of the temperature control SP is ramped from 300 to 340 K over a period of time. The effect of this ramp rate is investigated below. If the ramp rate is too fast, the reactor temperature may run away because the heat removal system may not be able to remove the heat generated with the high initial concentrations of reactant A. If the ramp rate is too slow, the batch time will be long and therefore reduce productivity. 

The digestion and hydrolysis temperatures are controlled between 110 and 125°F. During hydrolysis, approximately 2 parts of water per 100 parts of reaction product are added to convert acid anhydrides to sulfonic acid. Both the oleum and S03 sulfonation processes are quite exothermic and almost instantaneous. In order to prevent decomposition and maintain optimum product color, an efficient reactor heat removal system is necessary. 

For a reactor operating with constant output, the criterion for optimal performance is for the cooling medium to have the highest possible temperature in the heat removal system. For a working example of the nonadiabatic reactor, there are 4631 cylindrical tubes with inner diameters of 7 mm packed with a catalyst and surrounded by a constantly boiling liquid at 703 K. Sulfur dioxide and air are fed into the reactor at a total pressure PT, in volume fractions of > s,, 2 =0.11 and >v,2 =0.10. The empirical expression oftakes into account diffusion and reaction kinetics, and we have... 

Failure of the utilities and ancillary systems occurs when one or more of tlie following is lost electric power, cooling water or other heat removal systems, steam or other heat supply systems, fuel, air, inert gas, or effluent disposal facilities. 

Sulfonation of LAB. The sulfonation of alkylbenzenes leads to sulfonic acid tyre product, which is then neutralized with a base such as sodium hydroxide to produce sodium alkylbenzene sulfonate. The sulfonation reaction is highly exothermic and instantaneous. An efficient reactor heat removal system is used to prevent the decomposition of the resultant sulfonic acid. The sulfonation reaction takes place by using oleum (SO3H2SO4) or sulfur trioxide (SO3). Although, the oleum sulfonation requires relatively inexpensive equipment, the oleum process has major disadvantages compared to sulfur trioxide. The need for spent acid stream disposal and the potential corrosion owing to sulfuric acid generation increased the problems related to oleum process [1]. 

The primary coolant circuit of a water-cooled reactor (including BWRs and PWRs) has several loops, including the main coolant loop, a core heat removal system, and a reactor water cleanup system. However, it is convenient, for computational purposes, to differentiate between the main loop, which has a high flow fraction, and the secondary loops, for which the flow fractions are small. The species concentrations and electrochemical potential (ECP) are solved for in the main loop and the values at the entrance to the secondary loop are used as the initial conditions for solving the system of equations for the secondary loops of interest. Mass balance is applied at each point where more than one section comes together. 

The primary coolant circuit of a PWR is shown in schematic form in Fig. 36. In this particular circuit, there are four loops between the reactor and the steam generators. The pressurizer is also shown, which maintains the pressure in the primary loop at a sufficiently high value (typically 150 bar) such that sustained boiling does not occur and maintains the desired concentration of hydrogen in the coolant. The reactor heat removal system (RHRS) and the reactor water cleanup system are not shown. The general operating conditions in a PWR primary loop are summarized in Table 2. 

Fig. 39 Schematic of the primary coolant circuit of a PWR, showing the three principal loops (1) the main loop (SI -SI 2), (2) the reactor heat removal system (RHRS, SI 7-SI 9), (3) the reactor water cleanup unit (RWCU,...

A Recirculating Inert Liquid Heat Removal System. While standard inert atmosphere gloveboxes may be used to perform ambient temperature reactions, the lack of a facility for localized heat removal (as provided externally be running tap water) precludes all syntheses requiring reflux, distillation, or sublimation. This limitation may be eliminated by the installation of a recirculating liquid heat exchange system. 

For energy exchange equipment Supply sufficient excess of heat transfer area in reboilers, condensers, cooling jackets, and heat removal systems for reactors to be able to handle the anticipated upsets and dynamic changes. Sometimes extra area is needed in overhead condensers to subcool the condensate to prevent flashing in the downstream control valves. Too frequently, overzealous engineers size the optimum heat exchangers based on an economic minimum based on steady-state conditions and produce uncontrollable systems. 

When stirred-tank reactors are operated in the batch mode, all ingredients are added at or near the beginning of the reaction cycle, the reaction is allowed to proceed to a desired end point, and the product latex is removed for further processing. Strict batch operation has a number of disadvantages. First, the heat load on the cooling system can be very nonuniform. The production rates from such reactors can be limited by the capability of the heat removal system during the peak in the exotherm. The use of mixed initiator systems (fast and slow) and the continuous addition of a fast initiator are two ways of trying to deal with this problem. 

Thermal loads upon the process heat exchanger do not allow rapid temperature change rates. Therefore in case of the demand for a decay heat removal system after a fast shutdown of the reactor, an auxiliary cooling system should be used rather than the main cooling system. In addition, much of the decay heat would be removed via the core surfaces to the liner cooling system [10]. 

In 1982, the Research Center Jiilich presented the conceptual design of a 50 MW(th) nuclear process heat plant with a pebble-bed HTGR, named AVR-II, for which a safety-related study has been conducted [29]. Its characteristic features are a slim steel pressure vessel, no separate decay heat removal system, shutdown and control system via reflector rods, surface cooling system, and a simplified containment. The safety of the reactor is principally based on passive system feamres. 

The AHTR 500 is a further development of the HTR-MODUL design with 500 MW(th). The helium coolant is heated up from 330 to 950 °C. The system pressure is 2 MPa. The new feature of this reactor design is a central graphite column to provide an additional heat sink. It contains a passive decay heat removal system on the basis of natural convection which runs also during normal operation. No intermediate circuit is foreseen for the connection with a coal gasification system [41]. 

Two concepts of a He - He intermediate heat exchanger for a heat rating of 125 - 170 MW have been selected. For both, a 10 MW test plant has been operated in the KVK loop verifying the operation of reformers with convective helium. A 10 MW decay heat removal system cooler, hot gas ducts including insulation and liner, hot gas valves, and a steam generator were other components of the KVK loop. Furthermore, a helium purification system was operated in a bypass of the main system. Starting in 1982, the KVK facility was operated for 18,400 h with approx. 7000 h above 900 C [28]. Hot gas duct with internal insulation was operated at temperatures up to 950 °C. The KVK experimental loop has demonstrated reliability and availability even of newly developed components. 

Tests in the EVA-II plant have shown that its operation at the same load is possible even if up to 30 % of the reforming tubes were blocked, meaning that isolation of single tubes would not disturb the operation thus increasing the plant s flexibility. Analytical studies have been conducted at JAERI to investigate the steam generator as a passive heat sink in case of a failure of the heat removal system of the reformer to ensure its coolability. 

FLOW INDICATION. An electromagnetic flow meter is used on the primary heat-removal system of the submerged EBR-II reactor model. Figure 11 schematically shows the manner of jacketing the two electrodes of the flowmeter to bring them through the sodium and top of the reactor tank. The permanent magnet is surrounded by sodium. The electrodes are canned with a thin stainless steel sleeve concentric with the 4-inch sodium pipe. Inside the stainless steel can and sand-... 

The safe industrial oxidation of furanics using the Co/Mn/Br catalyst system needs a similar heat removal system as FDCA, like TA, is a very insoluble diacid, preventingthe use of jacketed cooling. In contrast to para-xylene, HMF, MMF, and AcMF are already partially oxidized on the benzylic positions, and consequently less heat is formed in their oxidation to FDCA, and reactor temperature may be... 

---