Pyrolytic gases

The gasification of the char issued from the pyrolysis of different waste streams is shown in Table 10.28. From the ash content of the char, it is possible to evaluate the quantity of syngas produced by steam gasification of the chars issued from the pyrolysis of the different waste streams. The combination of the syngas and the pyrolytic gases allows evaluation of the total potential energy recovered by gasification. 

Carbon residue may be present in the diesel fuel in suspended form. The carbon residue can be removed by ultracentrifuging. In the Smuda process some of the light layered clays can be carried out of the pyrolysis vessel with the hot pyrolytic gases and can be entrained in the condensed fuel. 

The core technology of the Thermofuel process is the catalytic reaction tower (or catalytic converter, Figure 15.7). The catalytic reaction tower contains a system of plates made from a special catalytic metal alloy. The metal plates are positioned so that the hot pyrolytic gases must travel a tortuous path, in order to maximize contact area and time. The catalyst chamber is heated to 220°C using the exhaust gases (not pyrolysis gases) from the furnace of the pyrolysis chamber. 

The Likun Process (China) uses a two-stage cracking process under normal pressures where the waste plastics are first pyrolyzed at 350-400°C in the pyrolysis reactor and then the hot pyrolytic gases flow to a catalyst tower where they undergo catalytic reforming over zeolite at 300-380°C. By having the catalyst in the second stage this overcomes the problems of rapid catalyst deactivation from coke deposits on the surface of the catalyst. 

Ozmotech have developed a Thermofuel process whereby waste plastic is converted into diesel by thermal degradation in the absence of oxygen. In this process the plastic waste is first melted and then cracked in a stainless steel chamber at a temperature of 350-425°C under inert gas (nitrogen). The catalytic reaction tower is designed in such a way that hot pyrolytic gases take a spiral or zigzag path to maximize contact area and time with the metal catalyst. The metal catalyst cracks hydrocarbon chains longer than C25 and reforms chains shorter than Ce. This leads to the formation of saturated alkanes. 

The compositions of the samples of produced gases from the pyrolysis furnace are as shown in Table II. The compositions of pyrolytic gases given in Table II are, as mentioned above, experimental values when the calorific value of the refuse is in the range of Hu = 1,265 1,330 kcal/kg. 

The composition of pyrolytic gases given in Table VI are experimental values mixed with 30 % of scrap tires. 

There are literature claims that phosphorus acts not only as a char promoter but also in the vapor phase, leading to a decrease in the effective heat of combustion (EHC). This activity could be either flame inhibition [i.e. incomplete combustion due to scavenging of radicals like H- or HO by phosphorus radicals in the vapor phase) or a change in the pyrolytic gases. If the decrease in the EHC is generally well observed, very few articles provide evidence of flame inhibition. 

Solution Polymers. Acryflc solution polymers are usually characterized by their composition, solids content, viscosity, molecular weight, glass-transition temperature, and solvent. The compositions of acryflc polymers are most readily determined by physicochemical methods such as spectroscopy, pyrolytic gas—liquid chromatography, and refractive index measurements (97,158). The solids content of acryflc polymers is determined by dilution followed by solvent evaporation to constant weight. Viscosities are most conveniently determined with a Brookfield viscometer, molecular weight by intrinsic viscosity (158), and glass-transition temperature by calorimetry. 

The only product obtained by the copolymerization of styrene and maleic anhydride in acetone was the alternating copolymer even in the presence of more than equimolar quantities of either styrene or maleic anhydride. However, as shown by the data in Table I, larger quantities were obtained than could be accounted for by the formation of the alternating copolymer when excess styrene was used for the copolymerization in benzene solutions. In addition to the precipitates, there was also a trace of benzene-soluble product, which was shown to be polystyrene by infrared spectrometric (28) and pyrolytic gas chromatographic techniques (26). 

The formation of block copolymers from styrene-maleic anhydride and acrylic monomers was also indicated by pyrolytic gas chromatography and infrared spectroscopy. A comparison of the pyrograms of the block copolymers in Figure 7 shows peaks comparable with those obtained when mixtures of the acrylate polymers and poly(styrene-co-maleic anhydride) were pyrolyzed. A characteristic infrared spectrum was observed for the product obtained when macroradicals were added to a solution of methyl methacrylate in benzene. The characteristic bands for methyl methacrylate (MM) are noted on this spectogram in Figure 8. 

Macroradicals obtained by the heterogeneous copolymerization of styrene and maleic anhydride in poor solvents such as benzene were used to initiate further polymerization of selected monomers. This technique was used to produce higher molecular weight alternating copolymers of styrene and maleic anhydride and block copolymers. Evidence for the block copolymers was based op molecular weight increase, solubility, differential thermal analysis, pyrolytic gas chromatography, and infrared spectroscopy. 

Pyrolysis produces three principal products - pyrolytic gas, oil, and char. Char is a fine particulate composed of carbon black, ash, and other inorganic materials, such as zinc oxide, carbonates, and silicates. Other by-products of pyrolysis may include steel (from steel-belted radial tires), rayon, cotton, or nylon fibers from tire cords, depending on the type of tire used. 

The gas remaining after oil recovery, called pyrolytic gas, or pyro-gas, is typically composed of paraffins and olefins with carbon numbers from one to five. Depending on the process, the heat value of the gas can range from 170 to 2,375 Btu per cubic foot, and averages 835 Btu per cubic foot.4 (Natural gas averages around 1000 Btu per cubic foot.) Most processes use the pyrolytic gas as fuel to heat the reactor. Any surplus gas can be flared or used to replace natural gas as boiler fuel. Emissions from burning... 

Table 8-4. Chromatographic Analysis of Pyrolytic Gas from Shredded Automobile Tires with Bead Wire In2...

Table 8-5. Chromatographic analysis of light oil condensed from pyrolytic gas at O C using shredded tires with bead vire4...

NOTE These light oils comprise only about 2 percent of the total pyrolytic gas volume. 

Whiting P, Goring DAI (1982) Phenolic hydroxyl analysis of lignin by pyrolytic gas chromatography Pap Puu 64 592-599... 

A selective method for quantitatively determining povidone, even in traces, uses pyrolytic gas chromatography [130]. 

Table III shows the results of analyses of harmful gaseous elements etc. in the pyrolytic gas and the exhaust gas.

PRODUCED PYROLYTIC GAS ANALYSES (CO-DISPOSAL OF SCRAP TIRE AND REFUSE)... 

TGA/DSC Delaminations Contamination Dispersion Dynamometer tests SAE J661, FAST, full scale Chemical composition as needed Pyrolytic gas chromatography Infrared analysis X-ray diffraction TGA/DSC Electron microprobe analysis (EMPA) SEM... 

In the gas treatment phase, the pyrolytic gas is normally separated by cooling into one or more oil fractions with different boiling ranges and the permanent gas with the main components H2, CO, CO2, and CH4. The condensable oils are chemically unstable and require treatment, for example hydrogenation or direct conversion in combination processes. 

The area is dominated by nuclear magnetic resonance, NMR. Valuable information can be obtained also by means of infrared spectroscopy and pyrolytic gas chromatography. However, the quantification of data obtained by the latter method is often difficult. 

Some Na dissolved in a soln. of ferf-butyl a-benzylacetoacetate and alcohol, then acrylonitrile added during 40 min. below 45°, the crude product treated with a little p-toluenesulfonic acid and heated in an oil bath at 165-170° until a constant pressure indicates completion of the pyrolytic gas evolution, then distilled 4-acetyl-5-phenylpentanenitrile. Y 98%. F. e. s. G. Naslund, A. Senning, and S.-O. Lawesson, Acta Ghem. Scand. 16, 1324 (1962). 

In the pyrolytic gas chromatographic analysis (PGCA) of aciylonitrile polymer under an inert atmosphere at 500-900 deg.C, lower nitriles, including methyl cyanide, HCN, and aciylonitrile were the main degradation products, but lower hydrocarbons, e.g. methane and ethylene, resulting from secondary decomposition, were also detected. Thermo-... 

The first is a pyrolytic approach in which the heat dehvered by the laser breaks chemical bonds in vapor-phase reactants above the surface, allowing deposition of the reaction products only in the small heated area. The second is a direct photolytic breakup of a vapor-phase reactant. This approach requires a laser with proper wavelength to initiate the photochemical reaction. Often ultraviolet excimer lasers have been used. One example is the breakup of trimethyl aluminum [75-24-1] gas using an ultraviolet laser to produce free aluminum [7429-90-5], which deposits on the surface. Again, the deposition is only on the localized area which the beam strikes. 

---