Cooled-type reactor

The Hanford N Reactor. The Hanford N reactor was built in 1964 for purposes of plutonium production during the Cold War. It used graphite as moderator, pierced by over 1000 Zircaloy 2 tubes. These pressure tubes contained slightly enriched uranium fuel cooled by high temperature light water. The reactor also provided 800 MWe to the Washington PubHc Power Supply System. This reactor was shut down in 1992 because of age and concern for safety. The similarity to the Chemobyl-type reactors played a role in the decision. 

Uranium and mixed uranium—plutonium nitrides have a potential use as nuclear fuels for lead cooled fast reactors (136—139). Reactors of this type have been proposed for use ia deep-sea research vehicles (136). However, similar to the oxides, ia order for these materials to be useful as fuels, the nitrides must have an appropriate size and shape, ie, spheres. Microspheres of uranium nitrides have been fabricated by internal gelation and carbothermic reduction (140,141). Another use for uranium nitrides is as a catalyst for the cracking of NH at 550°C, which results ia high yields of H2 (142). 

Chlorination of Hydrocarbons or Chlorinated Hydrocarbons. Chlorination at pyrolytic temperatures is often referred to as chlorinolysis because it involves a simultaneous breakdown of the organics and chlorination of the molecular fragments. A number of processes have been described for the production of carbon tetrachloride by the chlorinolysis of various hydrocarbon or chlorinated hydrocarbon waste streams (22—24), but most hterature reports the use of methane as the primary feed. The quantity of carbon tetrachloride produced depends somewhat on the nature of the hydrocarbon starting material but more on the conditions of chlorination. The principal by-product is perchloroethylene with small amounts of hexachloroethane, hexachlorobutadiene, and hexachloroben2ene. In the Hbls process, a 5 1 mixture by volume of chlorine and methane reacts at 650°C the temperature is maintained by control of the gas flow rate. A heat exchanger cools the exit gas to 450°C, and more methane is added to the gas stream in a second reactor. The use of a fluidi2ed-bed-type reactor is known (25,26). Carbon can be chlorinated to carbon tetrachloride in a fluidi2ed bed (27). 

The reaction section consists of the high pressure reactors filled with catalyst, and means to take away or dissipate the high heat of reaction (300-500 Btu/lb of olefin polymerized). In the tubular reactors, the catalyst is inside a multiplicity of tubes which are cooled by a steam-water condensate jacket. Thus, the heat of reaction is utilized to generate high pressure steam. In the chamber process, the catalyst is held in several beds in a drum-type reactor with feed or recycled product introduced as a quench between the individual beds. 

Cold-Wall Reactors. In a cold-wall reactor, the substrate to be coated is heated directly either by induction or by radiant heating whi 1 e th e rest of the reactor remains cool, or at least cooler. Most CVD reactions are endothermic, i.e., they absorb heat and deposition takes place preferentially on the surfaces where the temperature is the highest, in this case the substrate. The walls of the reactor, which are cooler, remain uncoated. A simple laboratory-type reactor is shown... 

It is assumed that all the tank-type reactors, covered in this and the immediately following sections, are at all times perfectly mixed, such that concentration and temperature conditions are uniform throughout the tanks contents. Fig. 3.10 shows a batch reactor with a cooling jacket. Since there are no flows into the reactor or from the reactor, the total mass balance tells us that the total mass remains constant. 

A tubular type reactor was used in this experiment as shown in Fig. 2. Two copper electrodes with an area of 100 cm2 each were set in parallel with a gap of 3.5 cm. In order to diminish the eddy current in the gas flow, Teflon inserts were set in a tubular reactor as shown in Fig. 2. The bottom electrode was cooled by circulating water. The temperature of water was almost 19 °C throughout this experiment. 

The next simplest reactor type is a sequence of adiabatic reactors with interstage heating or cooling between reactor stages. We can thus make simple reactors with no provision for heat transfer and do the heat management in heat exchangers outside the reactors. 

This suggests immediately the definition of autocatalysis. A reactive intermediate or heat can act as catalysts to promote the reaction. However, in contrast to conventional catalysis, we do not add the catalyst from outside the system, but the catalyst is generated by the reaction (autocatalysis). We may add promoters or heat to initiate the process, which then accelerates by autocatalysis. Conversely, we may add inhibitors or cool the reactor to prevent both types of autocatalysis. 

Highly exothermal reactions can be applied by external heat exchange (1,39). If a CSTR-type reactor is not desired, the horizontal reactor with interstage cooling is an attractive alternative. 

One of the three options considered in Chapter 5 was a cooled tubular reactor with a coolant temperature that is the same down the length of the bed. With this type of system, the temperature of the coolant can be used as the manipulated variable to control some variable in the reactor. We will illustrate the control of the peak temperature by using several temperature measurements at different locations and selecting the highest to feed to a temperature controller as the process variable PV signal. The output signal OP of this controller will be the coolant temperature. 

The Cu-CI thermochemical cycle has been under development for several years. The goal is to achieve a commercially viable method for producing hydrogen at a moderate temperature ( 550°C). This chemical process, if successfully developed, could be coupled with several types of heat sources, e.g. the supercritical water reactor, the Na-cooled fast reactor or a solar heat source such as the solar power tower with molten salt heat storage. The use of lower temperature processes is expected to place less demand on materials of constmction compared to higher ( 850°C) temperature processes. 

In the Lurgi process a cooled tube reactor is applied. The catalyst particles are located in the tubes and cooling takes place by boiling water. The most important difference between the two reactor types is the temperature profile. In the Lurgi reactor it is much flatter than in a quench reactor. 

Only Westerterp [15] up to now also took the required selectivity into account in a reactor stability study, but only for tank reactors. We will use his study as a starting point and extend it to multiple reactions in a cooled tubular reactor. Recently Westerterp, Ptasinsky [16,17] and Overtoom [18,19] published studies on multiple reactions in this reactor type. 

Description Ethylene is compressed (6) and introduced to a bubble-column type reactor (1) in which a homogenous catalyst system is introduced together with a solvent. The gaseous products leaving the reactor overhead are cooled in a cooler (2) and cooled in a gas-liquid separator for reflux (3) and further cooled (4) and separated in a second gas-liquid separator (5). 

Actinide nitrides are known for Th through Cm. All of the nitrides are high melting compounds with melting points of 2630 °C, 2560 °C, and 2580 °C for Th, Np, and Pu, respectively. The actinide nitrides can decompose to give N2. Thorium, uranimn, and plutonium nitrides are well known and can be used as nuclear fiiels. Fuels of this type, especially uranium and mixed uranium plutonium nitrides, can be used in lead-cooled fast reactors, which have been proposed as a possible next-generation nuclear reactor and for use in deep-sea research vehicles. 

For this heat recovery, continuous operation with the use of heat exchangers between the inlet flow and outlet flow of the reactor is needed. With a batch-type reactor, solid particles can be handled rather easily, but it is difficult to achieve heat recovery at a high efiiciency. This is because the reactor has to be cooled down and depressurized for placement of the feedstock and recovery of the ash and char. Without continuous operation, the hydrothermal process would be inappiopiiate for an energy conversion process. 

The water cooled tubular reactor (WCTR) represents the optimal solution for the etherification because it is the best compromise between kinetics and thermodynamics [7]. The Snamprogetti (now Saipem) WCTR (Figure 11.5) is a bundle-type heat exchanger with the catalyst in the tube side and the tempered cooling water flowing co-current or counter-current in the shell side. The catalyst is self-supporting in the bottom shell of the reactor, in the tubes and above the upper tube sheet. 

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