Pyrolysis, flash liquids

Flash-liquid Liquid obtained from flash pyrolysis accomplished in a time of < 1 s Flash-gas Gaseous material obtained from flash pyrolysis within a time of < 1 s Hydropyrolysis Pyrolysis with water Methanopyrolysis Pyrolysis with methanol Ultrapyrolysis Pyrolysis with very high degradation rate... 

GC = gas chromatography, Py = pyrolysis (flash or hydrous heating), MS = mass spectrometry (HR = high resolution), IRMS = isotope ratio mass spectrometry, HPLC = high-pressure liquid chromatography, EC = electron capture. Cl = chemical ionization, NMR = nuclear magnetic resonance spectrometry. X-ray = X-ray crystallography. 

Fig. 10. Liquid-fuel production by flash pyrolysis usiag char recycle.

Table 17. Properties and Analysis of Liquid Fuel and No. 6 Fuel Oil Liquid fuel produced by flash pyrolysis using char recycle (Fig. 10).

The results of low-temperature matrix-isolation studies with 6 [41a] are quite consistent with the photochemical formation of cyclo-Cif, via 1,2-diketene intermediates [59] and subsequent loss of six CO molecules. When 6 was irradiated at A > 338 nm in a glass of 1,2-dichloroethane at 15 K, the strong cyclobut-3-ene-1,2-dione C=0 band at 1792 cm in the FT-IR spectrum disappeared quickly and a strong new band at 2115 cm appeared, which was assigned to 1,2-diketene substructures. Irradiation at A > 280 nm led to a gradual decrease in the intensity of the ketene absorption at 2115 cm and to the appearance of a weak new band at 2138 cm which was assigned to the CO molecules extruded photo-chemically from the 1,2-diketene intermediates. Attempts to isolate cyclo-Cig preparatively by flash vacuum pyrolysis of 6 or low-temperature photolysis of 6 in 2-methyltetrahydrofuran in NMR tubes at liquid-nitrogen temperature have not been successful. 

Samolada, M.C., Baldauf, W., Vasalos, I.A., Production of bio-gasoline by upgrading biomass flash pyrolysis liquids via hydrogen processing and catalytic cracking, Fuel, 1998, 77, 1667. 

Efficient technology could also be developed based on catalytic biomass pyrolysis for the conversion of biomass into clean and renewable liquid bio-oil. This would facilitate its introduction into the energy market as a renewable fuel or as source of high value chemicals. It is possible to produce stable liquid biofuels from biomass flash pyrolysis, in a single stage catalytic process, although further developments are necessary. 

The main drawback with the thermochemical route for biomass utilization is the strong dependence on scale-up. To be competitive, the capacity has to be of the order of a small oil refinery (approx. 1 million tonnes per year), but there then exists the problem of the cost of transporting the biomass relatively long distances to this production capacity. Pyrolysis or related technologies ( flash or fast ) could transform biomass into liquid products that are more easily transported, and these liquid products could then be the input for a large, centralized... 

With respect to partial conversion by flash pyrolysis, the principal consideration in a choice between otherwise equivalent coals is the fact that liquid yields tend to increase with rank up to high volatile bituminous coals and thereafter to fall off sharply. 

The parent azocine (91) was isolated at —190 °C from flash vacuum pyrolysis of diazabas-ketene (90) (71JA3817). The compound, which must be handled in KOH-coated glassware, decomposes at -50 °C to colored tarry material. Characterization was by mass spectrum (m/e 107), NMR spectrum (see 91) and conversion with potassium in liquid ammonia to a dianion, which on quenching and hydrogenation gave azocane in low yield. 

A report on the continuous flash pyrolysis of biomass at atmospheric pressure to produce liquids indicates that pyrolysis temperatures must be optimized to maximize liquid yields (36). It has been found that a sharp maximum in the liquid yields vs temperature curves exist and that the yields drop off sharply on both sides of this maximum. Pure cellulose has been found to have an optimum temperature for liquids at 500°C, while the wheat straw and wood species tested have optimum temperatures at 600°C and 500°C, respectively. Organic liquid yields were of the order of 65 wt % of the dry biomass fed, but contained relatively large quantities of oiganic acids. 

Thermochemical Liquefaction. Most of the research done since 1970 on the direct thermochemical liquefaction of biomass has been concentrated on the use of various pyrolytic techniques for the production of liquid fuels and fuel components (96,112,125,166,167). Some of the techniques investigated are entrained-flow pyrolysis, vacuum pyrolysis, rapid and flash pyrolysis, ultrafast pyrolysis in vortex reactors, fluid-bed pyrolysis, low temperature pyrolysis at long reaction times, and updraft fixed-bed pyrolysis. Other research has been done to develop low cost, upgrading methods to convert the complex mixtures formed on pyrolysis of biomass to high quality transportation fuels, and to study liquefaction at high pressures via solvolysis, steam—water treatment, catalytic hydrotreatment, and noncatalytic and catalytic treatment in aqueous systems. 

Pyrolysis of biomass is divided into slow pyrolysis, which is well known to produce charcoal, for example, fast pyrolysis, which produces a high yield of liquid biofuels and other chemicals (Bridgwater, 2000) and flash pyrolysis. Slow pyrolysis (or carbonisation) requires low temperatures and very long residence time. In the carbonisation process the amount of char is maximised. 

Liquids from the flash pyrolysis of coal are heavy and viscous. The hydrogen-to-carbon atomic ratio is about 1.1. They are high in asphaltenes and preasphaltenes, which render them only partially distillable. 

The liquids require a hydrorefining step to stabilize their reactive properties, to reduce the asphaltenes and preasphaltenes, to reduce sulfur, nitrogen, and oxygen, and to make the liquids more distillable. The extent of hydrorefining depends on the end use of liquids—fuel oil or chemical feedstocks. The objective of this work is to evaluate the hydrorefining processibility of ORC flash pyrolysis coal tar as a part of the tar characterization task. Results of the initial phase of catalyst screening tests are reported in this chapter. 

The formation of gas was low. From the carbon balance, only 3% of the total carbon formed gaseous products. The hydrogen consumption was approximately 3100 scf/bbl, of which nearly 80% was consumed in liquid hydrogenation. This preliminary result demonstrated that the flash pyrolysis coal tar derived from a subbituminous coal is amenable to hydrorefining. 

Flash Pyrolysis Coal is rapidly heated to elevated temperatures for a brief period of time to produce oil, gas, and char. The increase in hydrogen content in the gases and liquids is the result of removing carbon from the process as a char containing a significantly reduced amount of hydrogen. Several processes have been tested on a rela-... 

During the slow pyrolysis of polyethylene, for a temperature increase from 400 to 700° C, the yield in liquid phase remains higher than 80% with a very small increase in the yield of gas phase (less than 20%). On the other hand, in flash pyrolysis of polyethylene, an increase of temperature from 550 to 700°C leads to a decrease of the yield in the liquid phase to less than 40% with an increase in the yield of the gas phase up to 60%. 

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