**4. Process development with oil venturi condenser**

As an imperfection of the first plant the steam was condensed with pyrolysis oil together and steam water after its gravity or centrifugal separation from the oil it was contaminated with different benzene and other low-temp aromatic fractions of the tire pyrolysis oil as well soluble with water. Such of contaminated steam water has become a regulation problem for its normal cycling to steam boiler again and so for the new process to be certificated in Taiwan and elsewhere, including some other operating problems considered in [36, 37] and being all the problems resulted simply from the water tube condensers applied and operated with water at 35-40°C. Moreover, operating by this way it was resulted in a lowquality of pyrolysis oil fuel in terms of the flash point temp which was about 40°C correspondingly.

With reference to [36, 37] in project for ALPHA RECYCLAGE FRANCHE COMTE (France) in 2009-2010 the tire-steam pyrolysis system has been developed and modernized so as a new condenser of venturi type with steam too is used (Fig.2), being first and only one referenced as without steam but namely for such of application in [2]. The new steam pyrolysis system is operating with oil condensing at near 100°C, proposing so way its quality in terms of the flash point temp to be high as near 80°C. Steam is not condensing and all piping with residual off-gas to furnace by which way only the oil condenser 4 is required (see Fig.2). And so way the furnace gas flow is rather enhanced with steam for heating reactor and next boiler where steam is acting in a new manner as a heating agent too which analyzed here.

Waste Tire Pyrolysis Recycling with Steaming:

per 1 kg tire is obtained:

above.

1 *<sup>s</sup>*

<sup>Δ</sup> Δ =≥

is also obtained by the analytical heat-mass balance as following:

Δ <sup>2</sup>

*a a G G*

*<sup>G</sup> STEAM*

*s*

*G*

*g*

*T*

*a t*

difference of the flow between the reactor inlet-outlet as follows:

*<sup>G</sup> AIR G* =

Heat-Mass Balances & Engineering Solutions for By-Products Quality 223

provided simply by air injection into boiler (similar to its injection into furnace in Fig.1) that

3 () 2

<sup>−</sup> ≥ ⋅ <sup>−</sup> <sup>−</sup> <sup>−</sup> − +

*g a ps g*

where the total air injection rate (with combusting air and relatively to tire pyrolysis rate)

Due to the more off-gas afterburning rate as *GAS* = 17-18% instead of around 10% before, including all the steam used and air injected as above, now it is a rather more furnace gas flow available for heating the pyrolysis reactor which results in rather less acting temp

*T T g g* 1 2 <sup>−</sup> ( ) ( )

*T T c T*

200 0.15

(min)

( )

() () 1 [ ]( ) 100 *n gas f n pa ps g a*

() ()

− ++ − <sup>=</sup> <sup>+</sup>

*f r ps pa*

Calculating data on the modernized process by (10)-(14) with max 1% iterating discrepancy and max 5% calculating accuracy are presented in Table 3, where these are compared to operating data on the first steam pyrolysis system in Taiwan. Shortly it can be concluded as the new system is rather more capable for convective heating the pyrolysis reactor first by factor of the furnace gas flow than by its high temperature (i) in which accordance the reactor is also developed properly as a triple-screw design of a long heating surface (see Fig.2). In second, by more heating and 1.5 times longer process way the carbon black quality is proposed to be surely high as 1% and less of the tire residual matters. In third, steam boiler is correspondingly also heating much more and steam producing rate is proposed to be well enough as for feeding the reactor, as for injecting into the oil Venturi condenser (iii) as it is considered in the next p.5, including the oil quality is to be also high as noted yet

The numerical data on steam limitation with air injection by (13) are presented in the Table 3 so as the low-calorific heat value of the off-gas with steam mixture can be well increased as 5.5 MJ/m3 (1300 kcal/m3). In this connection and with the same reference to [36, 37] the special flow-vortex burner for the low-calorific gas fuel condition is proposed to be applied, being that well appropriated namely in the similar steam process with carbon black pyrolysis recycling from coal in Russia in commercial scale in 70-80-ths, where the similar off-gas was also much diluted by 80% with both steam and nitrogen as 3.3–3.8 MJ/m3 (800– 900 kcal/m3), i.e. even bellow the critical value above. The burner is operating by the gas

() () *<sup>p</sup> <sup>t</sup> <sup>p</sup> a t <sup>p</sup> <sup>s</sup> <sup>p</sup> <sup>s</sup>*

*STEAM*

*c TT hc TT AIR EE c c*

( 200) <sup>1</sup> ( )

*p ws a s*

*c TT h*

*AQ E GAS*

*Ac c T T* <sup>=</sup> + − , (13)

 − − 

1 *gas <sup>s</sup> gas gas*

*Q GAS Q STEAM* ρ

ρ

, (11)

, (12)

. (14)

With furnace flue gas together steam is piping to scrubber and condensing therein simply with water, being so way water is far from the oil and nothing of oil-water separating equipment is required.

Fig. 2. Diagram of the modernized steam pyrolysis system: 1- reactor, 2 – furnace, 3 – steam boiler, 4 – venturi condenser, 5 – exhaust scrubber, 6 – cooling tower, 7 – water cooler for scrubber , 8 – oil fuel burner, 9-12 – air blowers and gas fans, 13-17 – water and oil pumps, 18-19 – scrap tire feeding system.

Basing and referencing to the data on the tire pyrolysis oil distillation with temp in [1, 2] and with the same reference to [36, 37] it is analytically obtained that the new process is characterized as *OIL* = 40-45% pyrolysis oil to be condensed at 100°C and correspondingly *GAS* = 17-18% incondensable off-gas to be residual (relatively to tire mass), being the latter well enough for the process heating without oil at all. By the analytical heat-mass balance it is resulted in the next formulation on the steam self-producing rate:

$$\text{STEAM} = \frac{G\_s}{G\_t} = \frac{Q\_{gas}E\_f}{[A\_n c\_{p(a)} + c\_{p(s)}](T\_{g1} - T\_a)} \frac{GAS}{100} \,\text{}\,\text{}\,\tag{10}$$

where the complex *An* is for the math compaction too:

$$A\_n = \frac{G\_a}{G\_s} = \frac{c\_{p\{w\}}(T\_s - T\_a) - c\_{p\{s\}}(T\_{g2} - 200) + h\_s}{c\_{p\{a\}}(T\_{g2} - 200)} \,. \tag{10'}$$

By this way it is rather more steam self-producing rate then before in Taiwan and to avoid the off-gas would be diluted with steam too much as no ignition by [34] with reference to [36, 37] the steam self-producing rate is to be limited and reduced by Δ*STEAM* ≥ 15% which is formulated and calculated as follows:

With furnace flue gas together steam is piping to scrubber and condensing therein simply with water, being so way water is far from the oil and nothing of oil-water separating

Fig. 2. Diagram of the modernized steam pyrolysis system: 1- reactor, 2 – furnace, 3 – steam boiler, 4 – venturi condenser, 5 – exhaust scrubber, 6 – cooling tower, 7 – water cooler for scrubber , 8 – oil fuel burner, 9-12 – air blowers and gas fans, 13-17 – water and oil pumps,

Basing and referencing to the data on the tire pyrolysis oil distillation with temp in [1, 2] and with the same reference to [36, 37] it is analytically obtained that the new process is characterized as *OIL* = 40-45% pyrolysis oil to be condensed at 100°C and correspondingly *GAS* = 17-18% incondensable off-gas to be residual (relatively to tire mass), being the latter well enough for the process heating without oil at all. By the analytical heat-mass balance it

> () () 1 [ ]( ) 100 *gas f n pa ps g a*

*Q E GAS*

*Ac c T T* <sup>=</sup> + − , (10)

−− − + <sup>=</sup> <sup>−</sup> . (10')

is resulted in the next formulation on the steam self-producing rate:

*<sup>G</sup> STEAM G*=

where the complex *An* is for the math compaction too:

*<sup>a</sup> <sup>n</sup> s*

*<sup>G</sup> <sup>A</sup>*

is formulated and calculated as follows:

*s t*

*<sup>G</sup>* <sup>=</sup> ( ) () 2

() 2

*pa g*

*c T*

By this way it is rather more steam self-producing rate then before in Taiwan and to avoid the off-gas would be diluted with steam too much as no ignition by [34] with reference to [36, 37] the steam self-producing rate is to be limited and reduced by Δ*STEAM* ≥ 15% which

( ) ( 200) ( 200) *p ws a p s g s*

*c TT c T h*

equipment is required.

18-19 – scrap tire feeding system.

$$
\Delta STEAM = \frac{\Delta G\_s}{G\_s} \ge 1 - \left(\frac{Q\_{\text{gas}}}{Q\_{\text{gas(min)}}} - 1\right) \frac{\rho\_s}{\rho\_{\text{gas}}} \frac{GAS}{STEAM} \,\,\,\,\tag{11}
$$

provided simply by air injection into boiler (similar to its injection into furnace in Fig.1) that is also obtained by the analytical heat-mass balance as following:

$$\frac{\Delta G\_a}{G\_a} \ge \frac{T\_{\S^2} - 200}{T\_{\S^3} - T\_a} \cdot \frac{0.15}{1 - \frac{c\_{p(s)}(T\_{\S^2} - 200)}{c\_{p(w)}(T\_s - T\_a) + h\_s}}\text{ }\tag{12}$$

where the total air injection rate (with combusting air and relatively to tire pyrolysis rate) per 1 kg tire is obtained:

$$AIR = \frac{G\_a}{G\_t} = \frac{A\_n Q\_{gas} E\_f}{[A\_n c\_{p(a)} + c\_{p(s)}](T\_{g1} - T\_a)} \frac{GAS}{100} \,\text{,}\tag{13}$$

Due to the more off-gas afterburning rate as *GAS* = 17-18% instead of around 10% before, including all the steam used and air injected as above, now it is a rather more furnace gas flow available for heating the pyrolysis reactor which results in rather less acting temp difference of the flow between the reactor inlet-outlet as follows:

$$T\_{\mathcal{S}^1} - T\_{\mathcal{S}^2} = \frac{c\_{p(t)}(T\_p - T\_a) + h\_t + c\_{p(s)}(T\_p - T\_s)}{E\_f E\_r \left(c\_{p(s)} + c\_{p(a)} \frac{AIR}{STEAM}\right)} \tag{14}$$

Calculating data on the modernized process by (10)-(14) with max 1% iterating discrepancy and max 5% calculating accuracy are presented in Table 3, where these are compared to operating data on the first steam pyrolysis system in Taiwan. Shortly it can be concluded as the new system is rather more capable for convective heating the pyrolysis reactor first by factor of the furnace gas flow than by its high temperature (i) in which accordance the reactor is also developed properly as a triple-screw design of a long heating surface (see Fig.2). In second, by more heating and 1.5 times longer process way the carbon black quality is proposed to be surely high as 1% and less of the tire residual matters. In third, steam boiler is correspondingly also heating much more and steam producing rate is proposed to be well enough as for feeding the reactor, as for injecting into the oil Venturi condenser (iii) as it is considered in the next p.5, including the oil quality is to be also high as noted yet above.

The numerical data on steam limitation with air injection by (13) are presented in the Table 3 so as the low-calorific heat value of the off-gas with steam mixture can be well increased as 5.5 MJ/m3 (1300 kcal/m3). In this connection and with the same reference to [36, 37] the special flow-vortex burner for the low-calorific gas fuel condition is proposed to be applied, being that well appropriated namely in the similar steam process with carbon black pyrolysis recycling from coal in Russia in commercial scale in 70-80-ths, where the similar off-gas was also much diluted by 80% with both steam and nitrogen as 3.3–3.8 MJ/m3 (800– 900 kcal/m3), i.e. even bellow the critical value above. The burner is operating by the gas

Waste Tire Pyrolysis Recycling with Steaming:




steam boiler temp, *T2* – steam temp after the throttle effect,

2 1

(max)

*s*

*w*

specific heat value at the normal (atmospheric) pressure.

**5.1 Spraying water specific flow rate** 

*T T*

Inlet point A:

Mixing point B:

Condensing point C:

wetting as follows:

Heat-Mass Balances & Engineering Solutions for By-Products Quality 225

With steam the oil condensing temp is well provided as near 100°C for the flash point to be at near 80°C. Moreover, the Venturi tube part is actively cleaning against the carbon soot by the same steam jet for spraying. There are three acting specific points with pyrogas-steam reactor flow mixing with steam-water jet and resulting in condensed oil droplets with incondensable

Proposing a simple sonic type of steam nozzle for spraying water, initially a self-cooling and wetting effect with steam jet discharged at near the sonic velocity (throttle effect) to be considered, which can be maximally estimated by [40] under the next steam min pressure and temp conditions to be: min *p* = 0.4 MPa – steam pressure (abs), *T =1* 142°C = 415 K –

> 2 2 <sup>415</sup> 1 14 1

Due to steam jet after its discharge is really cooling down only to 100°C and next a few steam is condensing at the same temp and normal pressure, it is acting for steam self-

() 2

*s c ( T)*

*h*

where *p s*( ) *c* = 0.5 kcal/kg·C is steam specific heat capacity, *<sup>s</sup> h* = 540 kcal/kg is steam

With author's reference to [35-37] the tire (rubber) pyrolysis specific heat required for its thermal destruction at near to steady pyrolysis temp 400-450°C is experienced

100 *p s*

72 °C. (15)

<sup>−</sup> = ≅ 3%, (16)

*k .* = =⋅ ≅ + +

pyrolysis off-gas and all steam residual flow in venturi tube as shown in Fig.3:


pre-mixing and ignition with air in a vortex-flame tunnel just before the furnace (see Fig.3) by which way there is an area in the tunnel where the gas flame is every moment torching and so igniting just near from the furnace.

Table 3. Modern Process Calculation in Comparison With Operating Process in Taiwan-2008
