Temperature preheater

Air preheat temperature requirements of 2250—2300 K are anticipated for natural gas-fired systems, and about 2000 K for oil or coal-fired systems (11). Use of 32—40% oxygen enrichment lowers the preheat temperature requirement to a moderate 900—1000 K, which can be attained with conventional metal-type tubular heat exchangers. Depending on the cost of oxygen, this is a viable alternative to the use of separately fired high temperature preheaters. 

It is believed that asphaltic compounds within these heavy oils may be better distributed by high-temperature preheating. Distribution of these compounds may interfere with the formation of an organized wax lattice throughout the oil matrix as the oil cools. The result would be a pour point which is lower than that for an unheated or mildly heated oil. 

For effective burning of refuse, coke must be added as a supplementary fuel and limestone as a flux. To melt the slag at high temperatures, preheated, oxygen-enriched air is blown into the furnace. Accordingly, iron, glass, ceramics and the like contained in the refuse are discharged from the furnace in a molten state. 

The process of HTST pasteurization (Figure 5.5) is described in detail in Section 5.3. The variables used here are four temperature measurements (°C) and two PID controller outputs (mA). The hot water temperature, preheater outlet temperature of raw product, holding tube inlet temperature of pasteurized product and holding tube outlet temperature of pasteurized product are the output variables of the process (variables 1-4, respectively). The input variables of the process are the PID controller output to the steam valve (variable 5) that regulates the holding tube inlet temperature of product and the PID controller output to preheater hot wa-... 

Small particles of coke made in the process circulate in a fluidized state between the vessels and are the heat transfer medium. Thus the process requires no high-temperature preheat furnace. Fluid coking is carried out at essentially atmospheric pressure and temperatures in excess of 485°C (900°F) with residence times on the order of 15-30 seconds. The longer residence time is in direct contrast to the delayed coking process, in which the eoking reactions are allowed to proceed to completion. This is evident... 

The plasma-catalytic effect in non-equilibrium methane CO2 reformation (10 ) by sustaining the process with a combination of plasma energy and low-temperature preheating was demonstrated by Mutaf-Yardimci (2001) using an atmospheric-pressure pulsed eorona discharge. 

In this process, PLA sheet is heated to soften the polymer, forced either pneumatic and/or mechanically against the mold, allowed to cool, removed from the mold, and then trimmed. The radiant heater of the thermoforming line for PLA must be adjusted to very low temperatures. Preheating is not absolutely necessary however, it has the general advantage that the sheet is homogeneously preheated. 

On the other hand, burning from the top down suffers from incomplete combustion, which sometimes necessitates introduction of secondary air above the bed, if there is not adequate bypassing of air through the bed. Combustion above the bed is promoted by excess air, turbulence, and high temperature. Preheating of the incoming coal also assists complete combustion. 

The key scientific principles associated with the operation of a heat exchanger system include Temperature—preheat, condenser, reboiler, conversions Heat transfer—conductive, convective Tube growth—expansion Pressure—delta, inlet, outlet Fouling Boiling points pH of water... 

Saito, K., Hatakeyama, M., Komaki, 1., and Katoh, K. Solid state NMR studies for a new carbonization process with high temperature preheating. J. Mol. Struct. 2002 602-603 89-103. 

For property changes directly related to product temperature, preheaters or coolers can be used in the incoming-feed hopper, and heating/cooling traces can be used on the conveyor s barrel. These systems provide a means of achieving optimum conveyor performance despite variations in incoming product. 

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