Tracing electric heaters

Consequently traces of these unstable peroxides are present in samples of all the lower aliphatic ethers unless the samples have been freshly distilled. If these ethers when being distilled are heated on, for example, an electric heater, the final residue of peroxide may become sufficiently hot to explode violently. The use of a water-bath for heating, as described above, decreases considerably both the risk of the ether catching fire and of the peroxide exploding. 

Electric Tracing An electric tracing system (see Fig. 10-178) consists of an electric heater placed against the pipe under the thermal insulation, the supply of electricity to the tracer, and any control or monitoring system that may be used (optional). The supply of electricity to the tracer usually consists of an electrical panel and electrical conduit or cable trays. Depending on the size or the tracing system and the capacity of the existing electrical system, an additional transformer may be required. 

A reactor was cooled by a molten salt. At startup the salt was heated to reaction temperature by an electric heater. During one startup the temperature of the salt rose at only half the usual rate. Obviously one of the heaters was faulty, but no fault could be found. The problem was finally traced to a nitrogen valve, which had been left open. The flow of nitrogen through the reactor was taking away half the heat. 

Fig. 5. Time variations of the main converter bed temperature predicted with electric heater of different volumes (20 s heating at 2500 W). Also shown is the bed temperature trace with the 0.4 cm-long inert electric heater.

A selection of components surface-mounted to carrier plates is shown in Figure 4.34. The carrier plates support the internal fluidic pipes and can also be equipped with electrical heaters to permit trace heating of the fluid. The surface-mounted components of this system are compatible with the backbone concept introduced in the following. 

Apart from such requirements for head pressure control, winter precautions are needed to prevent freezing of the water while the plant is not rejecting heat to it. These commonly take the form of an electric immersion heater in the water tank, together with lagging and possible trace heating of exposed pipes. In some systems, the evaporative condenser itself may be within the building, with air ducts to the outside. In severe climates, external tanks need to be lagged to conserve the heat provided by the immersion heater. 

Often it is necessary to heat transfer lines to ensure that products do not gel in the line during cold weather. Both electrical heating and steam heating can be used to trace lines. Only explosion proof electrical heat tape and thermostats can be used on fuel systems. Immersion heaters are not recommended for fuel and fuel additive applications. 

Miscellaneous includes heater stacks, winterizing, insulation, steam or electrical tracing of lines, heat exchanger tubing size standardization, instrument locations. 

The feed pump was a positive-displacement, piston-type metering pump. All liquid transfer lines in the system were traced with electric resistance heaters which allowed us to process heavy SRC solutions. 

Because glacial acetic acid freezes at about 16°C, exceptional care must be taken for melting tke product in cool weather. Electrical or steam heaters may be employed Tank cars or tank wagons must be fitted witk heating coils, which can be attacked to a steam line and trap. Tank vents must be traced with electrical or steam lines to prevent crystallization. Acetic acid sublimes so that a single, large crystal can appear and completely fill an otherwise adequate vent. 

Partial oxidation ammonia plants have the same emission sources except for the primary reformer flue gas. The plants have an auxiliary boiler to generate steam for power production and fired heaters, which on account of the sulfur content of the fuel oil release a flue gas containing S02 (< 1500 mg/m3). Other possible emissions are H2S (< 0.3 ppmv), CO (30 ppmv) and traces of dust. The NO, content of the flue gas depends on the configuration of the auxiliary boiler and on the extent electric power generation on the site as opposed to outside supply. The total NO, emission per tonne of product may be somewhat lower than for steam reforming plants. 

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