Chemistry Reference
In-Depth Information
In the installations for studying linear pyrolysis described in the literature [2, 3,
4, 5], the temperature was set by a voltage supplied to the heater from the outputs
of a laboratory autotransformer. The main disadvantage of such a simple design is
a significant decrease in the experimental data accuracy due to the instability of the
heater temperature, which is caused by voltage fluctuations and convection currents
in the vicinity of the heater (which are especially high at
P
∞
>
0
.
1 MPa). To avoid
this problem, a point-to-point control system (Fig. 2.3) is used to stabilize the heater
at its point of contact with the sample in LP-1 and LP-2.
Potentiometer PP-69, used as a setter, is connected to the thermocouple. An error
signal amplified by the photogalvanic amplifier F-116 using relays R
1
(RP-4) and R
2
(MKU-48) controls the current passing through the heater by periodically engaging
a ballast resistance in the input circuit of the autotransformer. The heater is supplied
with power by a welding transformer T
R2
(12 V, 10 kW) connected to the outputs
of autotransformer T
R1
(LATR-1-9A) through its primary coil. Using the described
design, the temperature at the center of the heater was kept constant (
2
◦
C) up to
±
850-900
◦
C.
To conclude this section, let's consider a method for measuring the linear pyrol-
ysis rate based on the use of noncontact optical arrangements in combination with
all LP-type installations (LP-1, LP-2, LP-3, LP-4). During the study of “fast” linear
pyrolysis (
U
= 10
−
3
-10
−
5
ms
−
1
) (Fig. 2.3, left position of tumbler switch S
1
), the
photodiode signal moves directly to the input of the electronic potentiometer KVT-2,
potentiometer
4
V
R
2
1.5
V
F-116
R
1
1.5
V
V
power
supply
V
precision millivoltmeter
FD-3
V
TR
1
TR
2
KVT-2
FD-3
S1
V
Fig. 2.3
Schematic of the electric circuit for linear pyrolysis installations (see the text for
explanation)
