Condensate from the pyrolysis

Figure 3. Boiling behavior of the condensate from the pyrolysis of old tires (determined by DIN procedure 51751)...

Od condensed from the released volatdes from the second stage is filtered and catalyticady hydrotreated at high pressure to produce a synthetic cmde od. Medium heat-content gas produced after the removal of H2S and CO2 is suitable as clean fuel. The pyrolysis gas produced, however, is insufficient to provide the fuel requirement for the total plant. Residual char, 50—60% of the feed coal, has a heating value and sulfur content about the same as feed coal, and its utilisation may thus largely dictate process utdity. 

A typical ethane cracker has several identical pyrolysis furnaces in which fresh ethane feed and recycled ethane are cracked with steam as a diluent. Figure 3-12 is a block diagram for ethylene from ethane. The outlet temperature is usually in the 800°C range. The furnace effluent is quenched in a heat exchanger and further cooled by direct contact in a water quench tower where steam is condensed and recycled to the pyrolysis furnace. After the cracked gas is treated to remove acid gases, hydrogen and methane are separated from the pyrolysis products in the demethanizer. The effluent is then treated to remove acetylene, and ethylene is separated from ethane and heavier in the ethylene fractionator. The bottom fraction is separated in the deethanizer into ethane and fraction. Ethane is then recycled to the pyrolysis furnace. 

Mos of the solid carbonaceous material available to industry is derived from the pyrolysis of petroleum residues, coal, and coal tar residues. Understanding the reactions occurring during pyrolysis would be beneficial in conducting materials research on the manufacture of carbonaceous products. The pyrolysis of aromatic hydrocarbons has been reported to involve condensation and polymerization reactions that produce complex carbonaceous materials (I). Interest in the mechanism of pyrolysis of aromatic compounds is evidenced in a recent study by Edstrom and Lewis (2) on the differential thermal analysis of 84 model aromatic hydrocarbons. The study demonstrated that carbon formation was related to the molecular size of the compound and to energetic factors that could be estimated from ionization potentials. 

At higher temperatures, the intermediates, including levoglucosan and the condensation products further pyrolyze to give various products by fission of the carbohydrate units and rearrangement of the intermediate products. Table III shows the products obtained from the pyrolysis of cellulose and treated cellulose at 600° (8). The significant increase in the yields of water and char and decrease in the yield of tar in the acid treated cellulose verifies the previously mentioned promotion of dehydration and charring reactions by acidic additives. 

The semi-continuous type of reactor with the large capacity was comprised of a pyrolysis chamber, a catalytic cracking chamber and a separation and purifying section. The feed plastic material was melted and decomposed in the pyrolysis chamber held at the ambient pressure and at the temperature 723-783 K, and fed to the catalytic cracking chamber. A reflux condenser was used to separate and purify the products formed in the chamber and individual factors were obtained using fractional distillation apparatus [26]. Different types of reactors are being utilized depending on the type of feed and the expected products from the pyrolysis. 

Figure 15.6 Process flow for commercial pyrolysis plant (Thermofuel ) for converting waste plastics into diesel fuel. The plastic is heated to 375-425°C and the pyrolysis vapours are catalytically cracked and then selectively condensed. Note that the pyrolysis vessel is purged with nitrogen gas and that the hot pyrolytic vapours pass from the pyrolysis vessel to the catalytic reaction tower where they are cracked and reformed to give a high-purity diesel stream. (Reproduced by permission of Ozmotech Pty Ltd)...

Furthermore, the condensables from microwave pyrolysis contain less carcinogenic compounds than those produced in conventional pyrolysis [55] and the noncondensables have a higher concentration of CO and H2 (synthesis gas) after microwave pyrolysis than after conventional pyrolysis [56],... 

Data has been presented which suggests that moisture can enhance the production of tar from the pyrolysis of large wood particles using conditions that occur in a large scale reactor where the heat flux a particle experiences is quite constant. The most favorable conditions result in about 70% of the reacted biomass becoming tar. If one assumes that the mass balance discrepancy results from tar condensing on reactor surfaces, this is a conservative estimate. 

To assess applicability of the pyrolysis results to natural systems, C4-benzenes were quantified and thermal maturity ratios calculated for oils and condensates from the Fort Worth Basin (Fig. 5). The Fort Worth Basin hydrocarbons in this study were generated from a single source, the Mississippian Barnett Shale. The only molecular maturity indicator available for use for these oils and condensates was TAS. The steranes and hopanes had reached equilibrium and even TAS was no longer useful for the highest maturity condensates (Table 2). 

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