Combustion heat, distribution

Cracking reactions are endothermic, 1.6—2.8 MJ/kg (700—1200 BTU/lb) of hydrocarbon converted, with heat supplied by firing fuel gas and/or fuel oil in side-wall or floor burners. Side-wall burners usually give uniform heat distribution, but the capacity of each burner is limited (0.1—1 MW) and hence 40 to 200 burners are required in a single furnace. With modem floor burners, also called hearth burners, uniform heat flux distribution can be obtained for coils as high as 10 m, and these are extensively used in newer designs. The capacity of these burners vary considerably (1—10 MW), and hence only a few burners are required. The selection of burners depends on the type of fuel (gas and/or liquid), source of combustion air (ambient, preheated, or gas turbine exhaust), and required NO levels. 

The advantages of thermal incineration are that it is simple in concept, has a wide application, and results in almost complete destruction of pollutants with no liquid or solid residue. Thermal incineration provides an opportunity for heat recovery and has low maintenance requirements and low capital cost. Thermal incineration units for small or moderate exhaust streams are generally compact and light. Such units can be installed on a roof when the plant area is limited. = The main disadvantage is the auxiliary fuel cost, which is partly offset with an efficient heat-recovery system. The formation of nitric oxides during the combustion processes must be reduced by control of excess air temperature, fuel supply, and combustion air distribution at the burner inlet, The formation of thermal NO increases dramatically above 980 Table 13.10)... 

The temperature plots presented here are only a small portion of the data collected for heat distribution calculations. Generally, the heating rate Is slow up to 100 C (due to water vapourization) and thereafter becomes faster, on average approaching 0.5°C/mln, and the combustion temperature usually exceeds 1200 C. 

The heat liberated by combustion is distributed in one of three ways ... 

We analogously define the relaxation time of the heat distribution in the c-phase. We give a numerical example relating to combustion of a powder at atmospheric pressure. 

Furnace coils heated a flowing combustible heat-transfer oil before this hot oil is distributed and routed through the shells of four heat exchangers (reboilers) (see Figure 5—1). One of the four heat exchangers required considerable repairs and was shut down. The system pump continued to circulate hot transfer oil at about 460° F (240° C) through the other three reboilers while repairs were underway on the faulty exchanger. [2]... 

The MTU MCFC provides catalysed 600 °C anode reform capability, with flat anode temperature distribution. In contrast the 1000 °C SOFC encounters difficulties with anode reform, in which excessive reaction rates lead to unacceptable, thermally stressed, local anode cool zones. The title direct fuel cell (DFC) is used, to highlight the absence of a separate combustion-heated 800 °C reformer and its pre-reformer. The balance of plant flow sheet is shown in Figure 5.3. 

In the side-fired reformers the burners are located in the wall, and the box accomodates one or two rows of tubes, which receive their heat mainly by radiation from the walls of the furnace box. This is claimed to provide a very uniform heat distribution, which may additionally be adjusted by control of the individual burners. The larger number of burners makes fuel and preheated combustion air distribution more complicated and more expensive. As the heigth and width of the reformer are fixed by the radiation geometry of the tubes and furnace box walls, it is only possible to... 

Figures 12.4 and 12.5 show the distribution of OH and CH in swirl-stabilized propane-air flames using 25%/75% combustion air distribution in the inner and outer annulus of the burner, respectively. The results show that the reaction zone moves upstream towards the burner with high-shear, see Fig. 12.4. The distribution of CH shows a measure of the heat-release rate in flames. The heat-release rate is slow with the low-shear case to give a wider and longer flame (see Fig. 12.5). Figure 12.6 shows the distribution of OH in a kerosene flame with 55 /30 swirl distribution and 25%/75% combustion air (a) and 75%/25% combustion air distribution (b) in the two annular passages of the burner. Stronger...

Of great importance with in situ combustion process is also the rate of heat distribution on the rear side of the burning zone. If in zone I and II this rate is greater than the rate of advance of the burning front, then the heat of oxidation reaction will be shifted into the zone situated ahead of the burning front. However, when the opposite is true, then the heat of oxidation reaction will remain behind the zone of combustion. 

Furnace (Residential) - A combustion heating appliance in which heat is captured from the burning of a fuel for distribution, comprised mainly of a combustion chamber and heat exchanger. 

Thus, tangential firing is a method of firing a fuel to heat air in thermal power stations in which the flame envelope rotates ensuring thorough mixing within the furnace, providing complete combustion and uniform heat distribution. 

Flux rate is influenced by combustion characteristics and heat distribution. While the combustion characteristics can be described by combustion intensity, the heat distribution is explained by heat flux. The heat flux is defined as the heat transferred to the process feed, while combustion intensity is the heat released firom flame divided by the flame s external surface area. Clearly, combustion intensity is related to combustion flame, while heat flux is related to process. Another difference is that combustion intensity is inevitably an average value, while heat flux is either average or local values. Local heat flux requires more attention in design and operation. 

Wang, S. and Wang, S. (2007) Distribution optimization for plate-fin catalytic combustion heat exchanger. Chem. Eng. J., 131, 171-179. 

Various models are used for computing the heat flux of individual types of fire. In general, every model contains calculation of following quantities mass flow, duration of the gas release, shape of the gas cloud, heat generated due to combustion, heat flux. Meteorological conditions are taken into account in limited extent in models of jet fire and flash fire. Uncertainty in calculation of heat flux, selection of particular meteorological conditions and their influence on distribution of heat flux in time and space are main uncertainties of this part of the QRA. 

This chapter comprises three parts wherein we will examine the specifications of motor and heating fuels imposed by combustion, storage and distribution, and protection of the environment. 

In a plasma, the constituent atoms, ions, and electrons are made to move faster by an electromagnetic field and not by application of heat externally or through combustion processes. Nevertheless, the result is the same as if the plasma had been heated externally the constituent atoms, ions, and electrons are made to move faster and faster, eventually reaching a distribution of kinetic energies that would be characteristic of the Boltzmann equation applied to a gas that had been... 

The primary difference in shale oils produced by different processing methods is in boiling point distribution. Rate of heating, as well as temperature level and duration of product exposure to high temperature, affect product type and yield (28). Gas combustion processes tend to yield slightly heavier hquid products because of combustion of the lighter, ie, naphtha, fractions. 

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