Fired heaters start

In extremely cold environments, engines can quickly become difficult, sometimes nearly impossible, to start. If ordinary gasoline- or diesel-oil-fired heaters are used, the coolant circulation pump, air fan, etc, must be powered from the vehicle s batteries, thus curtailing the time the system can be used, especially at very low temperatures when it is needed the most. By adding PbTe thermoelectrics to such heater systems, about 2% of their thermal output can be turned into electricity to mn the heater s electronics, fuel pump, combustion fan, and coolant circulation pump, with stiH sufficient power left over to keep the vehicle s battery fliUy charged. The market for such units is in the hundreds of thousands if manufacturing costs can be reduced. 

Inappropriate positioning of combustible or flammable items in close proximity to heaters and parts of heating systems may prevent air circulation, causing a heat build-up, or if these materials are in direct contact or within range of any radiated heat a fire may start. 

In an emergency the control systems will shut down the reactors by inserting control rods into the core (this is known as a scram ). Unfortunately, this action does not immediately stop the nuclear reaction. Heat continues to be generated in the nuclear core even after shutdown, so it is essential that all three of the water systems continue to operate so that heat can continue to be removed for many hours. This need for on-going cooling is in contrast to most process plants in the hydrocarbon industry—a shutdown will immediately remove sources of heat, and temperatures will immediately start to fall to a safe value. Hence, the continued operation of cooling systems is not likely to be so critical (except maybe with respect to the high temperature firebrick on the inside of fired heaters). 

The first instantaneous water heaters which started appearing in the 1890s when gas or liquid fuels started becoming available, were un-pressurized. The first models had no automatic controls and vei"y limited safety features. Some early models were more efficient than standard modern gas-fired water heaters. 

With hot water units, time clock control can operate satisfactorily as automatic bypass valves built into the distribution system will help the heater to achieve its working temperature quickly. With steam boilers, it is important that the boiler reaches a reasonable working pressure before steam is allowed into the distribution system. For example, if boilers are left open to a system for an extended length of time while not firing they will quickly lose their pressure. This is not only wasteful of energy but eventually creates a problem on start-up. To... 

When the combustion air was cut back this time, fire started to come out of the stack. Now Operator A was forced to admit that they would have to increase the combustion air again. The problem they then faced was that the amount of draft in the heater seemed to be less than before and they were not quite able to reestablish the same airflow. The reason for the restricted airflow was that they had caused afterburn in the... 

Armed with the thermodynamic fundamentals of heat management, we now take a closer look at the unit operation control loops for heat exchangers. We start with utility exchangers. These are used when heat is supplied to, or removed from, the process. Examples are steam-heated reboilers, electric heaters, fuel-fired furnaces, water-cooled condensers, and refrigerated coolers. 

A barrel of 12°API resid takes perhaps 10% more furnace duty than a barrel of 8°API resid for identical heater inlet and outlet temperatures. Thus, a heater maintaining a constant outlet temperature will start firing much harder when it receives a slug of light feed. If overfiring results, the heater run length will be abbreviated. 

Low-pressure feed heater, the deaerator and the high-pressure feed heaters Three main feedwater pumps Two start-up feedwater pumps Switchgear rooms Electrical equipment room Lube oil storage tanks Motor-driven fire pumps Air compressors... 

The fire was supposed to start on the steel platform at the electrical oil heater. The evolution of the fire was considered as being linear over time. The characteristic time to reach 1 MW heat release rate was varied from 250 s to 700 s (see Table 1). In the upper layer cable tray, the cable targets were exposed to hot smoke and radiation. 

A 103-MWe conunercial demonstration plant was installed on a coal-fired boiler at Illinois Power s Wood River Power Station, Unit 4 (Jamgochian and Miller, 1974). Since this was a retrofit application, it was necessary to include equipment for reheating the flue gas to 8S0°-900°F before feeding it to the sulfuric acid converter. After start-up in September 1972, natural gas was used as fuel for the in-line heaters to reheat the feed gas. The plant operated successfully for 444 hours. 

A discussion of the types of heaters used for start-up of ammonia synthesis converters (fired vs. electrical heaters) is given in [910]. 

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