Solid fuels properties

Aho, M.J., HSmalainen, J.P., Tummavuori, J.L. (1993) Importance of Solid Fuel Properties to Nitrogen Oxide Formation Through HCN and NHj in Smalt Particle Combustion. Combust. Flame, 95, 22-30. 

Aho, M, HamSleinen, J. Tummavuori, J. (1993) Importance of solid fuel properties to nitrogen oxide formation through HCN and NHj in small particle combustion. Combustion and Flame, 95, pp. 22-30. 

Table 15.7 Typical properties of some solid fuels...

The condensed phase (solid or liquid) is considered as a general phase that will vaporize to a gaseous fuel with a mass fraction TFo, and can possibly form char with properties designated by ()c. The virgin fuel properties are designated without any subscript. 

The physical properties of solid fuels can be modified to a certain extent. It is the size, shape and density which are easy to change. Solid biofuels which are modified are here referred to as refined solid biofuels, see Figure 30. 

The preheating of solid fuel and the ash cooling are not included in the thermochemical conversion process. The basic criteria for these four thermochemical conversion reactions are that the solid-fuel convertibles (or moisture, char, volatiles) are converted from the solid phase into the interstitial gas phase and finally to the offgases (Figure 16 and Figure 19). The part of the solid-fuel convertibles that is converted into the interstitial gas phase is defined as the conversion gas [3]. The conversion gas is associated with two important physical properties, namely the empirical stoichiometry [CxHyOz] and the mass flux [kg/m s]. 

Complex pyrolysis chemistry takes place in the conversion system of any conventional solid-fuel combustion system. The pyrolytic properties of biomass are controlled by the chemical composition of its major components, namely cellulose, hemicellulose, and lignin. Pyrolysis of these biopolymers proceeds through a series of complex, concurrent and consecutive reactions and provides a variety of products which can be divided into char, volatile (non-condensible) organic compounds (VOC), condensible organic compounds (tar), and permanent gases (water vapour, nitrogen oxides, carbon dioxide). The pyrolysis products should finally be completely oxidised in the combustion system (Figure 14). Emission problems arise as a consequence of bad control over the combustion system. 

J.R. Gibson J.D. Weber, Handbook of Selected Properties of Air- and Water-Reactive Materials , NAVAMMODEP RDTR 144 (1969), 21-22 25) L. Greiner, Solid Fuel and... 

From the basic properties of gas-continuous impinging streams and the burning models derived in the last section, impinging streams intensify the combustion processes of atomized liquid and powdery solid fuels by the following mechanisms ... 

A fluidized bed is produced by passing a stream of gas vertically through a bed of solid particles at sufficient velocity to suspend the particles. In this state, the bed takes on many of the properties of a fluid. Solid fuel injected into the bed will also be fluidized until combustion is complete or until the solid fuel... 

As can be seen from Equation 3.20, the short-time solution for the pyrolysis time, tPi is independent of the total heat-transfer coefficient term, hT = (h, + h,). Thus, the pyrolysis time tp is only a function of the energy absorbed aq" due to radiation from the radiant panel and the properties (k, p, Cp) of the solid fuel sample. 

Figure 5.4 Schematic of the geometrical configuration for hydrogen-air flame and solid fuel. The geometry corresponds to the experimental setup. The initial shape of the HED fuel was a circular arc segment as shown above. The relevant material properties air density = 1.91 kg/m3, hydrogen density = 0.0898 kg/m3. For the turbulent quantities at the inlet k = (0.03f7iniet)2 = 9.59 (m/s)2, = CM3/4fc3/2/(0.03Liniet) = 6360 m2/s3, /Lit = C pk2/e = 0.00248 kg/ms. For the fuel sample, m.p. is 450 K, latent heat of fusion is 72.7 J/g. Dimensions in mm. Air inlet velocity 103.3 m/s, hydrogen injection velocity 800 m/s...

Hydroxyl-terminated polydiene resins gelled by the reaction with orthosilicate esters have increased thermal stability. These polymeric gels, like silicone rubbers, exhibit outstanding electrical properties. The polymeric gels crosslinked at ambient temperature are castable as self-curing liquids. For example, they are used as binders for rocket solid fuels, in coatings for pipes, tanks, etc. They can be mixed with rubbers. 

So far boundary conditions for gas phase calculations are taken from measurements or empirical correlation, limiting the application only to specific cases. Therefore the aim of the current project is to develop a numerical model, which predicts the conversion of the solid fuel in the packed bed. The model should take different operating parametors and main fuel properties, such as size and humidity of the fuel particles, into account. 

Two test rigs have been built for investigation of the combustion processes in a bed of solid fuels and particularly the influence of primary airflow and of particle properties (size, density and thermal conductivity) on the rate and temperature of the ignition front. Also the gas composition downstream of the bed has been investigated. The following conclusions can be drawn from the results ... 

Densification of solid wastes and biomass to produce solid fuels with more desirable physical properties is the subject of the fourth section. 

Table 2 Physical, chemical, and fuel properties of biomass, coal, and municipal solid waste...

R. P. Hensel, D. A. Harris, "Properties of Solid Fuels and Their Impact on Boiler Design and Performance," TIS-5889, September 10-13, 1978. 

These problems indicate the pressing need for methods to predict the deposition properties of solid fuels. This is required for operation and control of existing plants. However, this information is also significant in the planning of new plants to use difficult fuels or fuels on which little experience is available. 

Carbon forms a nitride, cyanogen, which is related to hydrogen cyanide. Both cyanogen and hydrogen cyanide are potential fuels, but both are extremely toxic and can be rejected based on the third criterion. Carbon disulfide is a room temperature liquid with fuel properties. It is less toxic than cyanogen, but is sufficiently toxic to be rejected because of the third criterion. When it bums, it produces large amounts of toxic sulfur dioxide. Nitrogen sulfide is an explosive solid. 

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