14. Syngas Quality Parameters.

Parameter	Boilers		Internal combustion engines	Gas turbines
	Combustion	Co-combustion
Lower heating value (kJ/Nm3)	> 4000	-	> 4000	> 4000
Particulates (mg/Nm3)	-	-	< 5-50	< 5-7
Tars (mg/Nm3)	-	-	< 0.5	< 0.1-0.5
alkali metals (ppm)	-	-	< 1-2	< 0.2-1

Pyrolysis is the most efficient process of biomass conversion producing combustible materials with high fuel-to-feed ratios (about 95.5%) [20]. The process can be guided in the direction of generating the desired product: char, oil or gas. Temperature is the most important factor that influences the proportion of products (Table XV). Production of combustible gas is maximized at high temperature, low heating rate and long gas residence time. Production of char is maximized at low temperature and low heating rate and production of oils is maximized at low temperature, high heating rate and short residence time.

Catalytic pyrolysis takes place at moderate temperature (775 K) in the absence of air and produce oils that can be used as fuel or as feedstock for chemical production. In order to maximize process production high heating rates and short residence times are required [20].

The pyrolysis process can be classified into: conventional pyrolysis, fast pyrolysis and flash pyrolysis. Conventional pyrolysis has slow heating rate and produces mainly char. fast pyrolysis takes place at high temperature with high heating rates and produces (60-75)% liquid, (15-25)% char and (10-20)% gas.

The pyrolysis oil is known as bio-oil, wood liquid, liquid smoke, wood distillates or pyroligneous tar.

15. Operating Parameters of Pyrolysis Processes.

Technology	Residence time of solid (s)	Heating rate (K/s)	Particle size (mm)	Temperature (K)
Conventional	450-550	0.1-1	5-50	550-950
Fast	0.5-10	10-200	< 1	850-1250
Flash	< 0.5	> 1000	< 0.2	1050-1300

Fast pyrolysis is used for production of chemicals and liquid fuels. The produce liquid fuels have can be storable and transportable. Fast pyrolysis could be more energy efficient and could have lower investments costs than other conversion process.

Flash pyrolysis is used for bio-oil production with an efficiency of up to 70%. The bio-oil can be used in internal combustion engines and gas turbines paying attention to poor thermal stability and corrosivity or as feedstock for refinery.

The use of bio oils in boilers, internal combustion engines and gas turbines may cause problems due to properties of bio-oils such as: poor volatility, high viscosity, acidity, poor thermal stability, high coking and deposition.

fig. 19 shows schematically a pyrolysis reactor.

energyfromwasteandwood.weebly.com

Figure 19. Pyrolysis system.

Ion V. Ion, associate professor, mechanical engineering: “Dunarea de Jos” University of Galati, Faculty of Mechanical Engineering, Thermal Systems and Environmental Engineering Department, 111, Domneasca St., off. G102, Galati, 800201, Romania, tel. +40 740566214, e-mail: ion.ion@ugal.ro

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Ion V. Ion, associate professor, mechanical engineering: “Dunarea de Jos” University of Galati, Faculty of Mechanical Engineering, Thermal Systems and Environmental Engineering Department, 111, Domneasca St., off. G102, Galati, 800201, Romania, tel. +40 740566214, e-mail: ion.ion@ugal.ro