JPH0314527A - Thermal decomposition of 1,2-dichloroethane - Google Patents

Abstract

PURPOSE:To control thermal decomposition temperature by calculating thermal decomposing rate from pressure and temperature of column top part of quenching column immediately after thermal decomposing furnace and temperature of refluxing solution returning to the column top part in obtaining vinyl chloride monomer and HCl with decomposing the subject substance. CONSTITUTION:1,2-dichloroethane (EDC) is supplied to thermal decomposing reaction tube 106-1 in thermal decomposing furnace 106-2 and a part of the EDC is thermally decomposed, then vinyl chloride monomer (VCM), HCl and undecomposed EDC are sent to quenching column 107. A part of distillate at column top is condensed by condenser 108 and stored in tank 109, then uncondensed gas is sent to hydrochloric acid column 110. A part of condensed solution in the tank is refluxed to the quenching column and residual part is introduced to the hydrochloric acid column Then HCl is recovered from the column top, thus VCM and EDC are sent to the vinyl chloride column 11 from bottom of the hydrochloric acid column. Thermal decomposing rate of EDC is calculated by pressure gauge PI 107 and thermometer TI 107 at the column top of the quenching column and thermometer of refluxing solution TI 109 or flow meter of refluxing solution FI 107. Then thermal decomposing temperature is changed in referring to difference with desired thermal decomposing rate, thus thermal decomposing rate is controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for thermally decomposing 1,2-dichloroethane (hereinafter abbreviated as EDC). For more information, see EDC
When thermally decomposing vinyl chloride monomer (hereinafter abbreviated as VCM) and hydrogen chloride, the thermal decomposition rate of EDC is quickly and continuously calculated, and this value is used to stably calculate the thermal decomposition rate of EDC. Concerning methods for controlling decomposition.

[Conventional technology] Conventionally, as a method for producing VCM, purified wavy EDC is evaporated in an evaporator, and this vapor is led to a pyrolysis furnace to produce 470
Methods are known for pyrolyzing EDC at temperatures of ~530<0>C. A flowchart of this process is shown in FIG.

Pyrolysis reaction tube (206-1) of pyrolysis furnace (206-2)
The high temperature decomposition gas flowing out from the
M, hydrogen chloride, and undecomposed EDC are included, but usually after removing a large amount of heat from the cracked gas in a quenching tower (207), hydrogen chloride is removed in a hydrochloric acid tower (210), and hydrogen chloride is removed in a PVC tower (2+1). VCM and undegraded EDC are separated and collected.

Heat removal in the quenching tower is carried out by a condenser (
20B), the heat is discharged to the outside of the yarn using cooling water, but EDC and VCM, which are relatively easy to condense in the cracked gas, become liquid during this heat removal. This liquid is returned as a reflux liquid from the tank (209) to the quenching tower, and the remainder is sent to the subsequent hydrochloric acid tower together with uncondensed hydrogen chloride and VCM. Generally, ED introduced into a pyrolysis furnace
The thermal decomposition rate of C is determined in relation to the quality of VCM finally obtained from the PVC tower, the amount of solid coke generated in the thermal cracking reaction tube, etc.

Industrially, attempts have been made to operate at a high thermal decomposition rate in order to increase VCM production and improve the energy efficiency required for thermal decomposition.
When polymerizing M, the amount of impurities produced in VCM increases due to side reactions of decomposition of butanoene, methyl chloride, etc., which causes a problem, and the quality of the obtained VCM deteriorates. Furthermore, the production of coke in the pyrolysis reaction tube is promoted, and the pressure loss gradually increases, making it necessary to stop the operation of the pyrolysis furnace in a relatively short period of time to remove coke, which results in direct and indirect This would result in an increase in manufacturing costs and a shortening of the stable operation period of the pyrolysis furnace.

Although it is desirable to maintain the thermal decomposition rate as high as possible, in consideration of these problems and the fact that the thermal decomposition rate is usually subject to relatively large fluctuations, it is difficult to maintain the thermal decomposition rate in actual operation. Pyrolysis rate of 50-60%, most commonly 53
A thermal decomposition rate of ~56% has been adopted.

The thermal decomposition rate of EDC is usually controlled by the thermal decomposition reaction temperature in the thermal cracking furnace.
It is known that the purity of C is affected by the impurities it contains. For example, carbon tetrachloride has the effect of promoting the thermal decomposition reaction of EDC, and when the thermal decomposition reaction temperature is constant, the thermal decomposition rate increases as the carbon tetrachloride content increases.

On the other hand, chlorobrene, oxygen-containing chlorinated hydrocarbons, etc. have the opposite effect and suppress the thermal decomposition reaction, so the thermal decomposition rate decreases as the content of these impurities increases.

EDC to be supplied to the pyrolysis furnace is purified in advance in a pretreatment step, and its purity is usually 99 to 99.7%, and the concentration of impurities also varies. The thermal decomposition rate is controlled by the thermal decomposition reaction temperature, but in reality, the above-mentioned conditions are added to the thermal decomposition reaction temperature, and the thermal decomposition rate fluctuates by about 2 to 3% with respect to the predetermined value. The reality is that it is difficult to constantly operate stably at the same thermal decomposition rate.

The thermal decomposition rate is generally calculated by the amount of VCM finally recovered from the PVC tower relative to the amount of EDC supplied to the thermal cracking furnace. Therefore, there is a time difference of 2 to 3 hours between the two measured values due to the difference in the position of the process, so that the relationship between the quality of EDC supplied to the pyrolysis furnace and the operating conditions of the cracking furnace can be quickly determined. It is difficult to maintain a stable decomposition rate because it cannot be determined.

One of the methods proposed to solve these problems is to keep the purity of the EDC supplied to the sweetfish cracking furnace, that is, the composition and amount of impurities, as constant as possible, but the operation in the previous process is complicated. , and also increases energy costs, which is not practical.

On the other hand, as a method for calculating the pyrolysis rate, there is a known method that does not involve time delay in analyzing and measuring the cracked gas leaving the pyrolysis furnace, but the cracked gas is at a high temperature and contains a large amount of hydrogen chloride. It is not practical because continuous sampling and analysis from points etc. is difficult.

[Problem to be solved by the invention] Under the constraints of increasing the pyrolysis rate as described above to avoid an increase in impurities in the VCM and promotion of coking in the pyrolysis reaction tube, and when supplied to the pyrolysis furnace. In order to stably pyrolyze EDC at the highest possible pyrolysis rate under the condition that the pyrolysis rate easily fluctuates depending on the quality of EDC and the operating conditions of the pyrolysis furnace, the pyrolysis rate must be determined quickly and accurately. It was strongly desired to find a method to control the pyrolysis temperature by calculating and feeding back the results.

[Means for Solving the Problems] As a result of intensive studies to solve the problems of the prior art as described above, the inventors of the present invention have developed a method for solving the problems of the prior art without using the amount of VCM recovered from the PVC tower in the subsequent process. It was discovered that the thermal decomposition rate can be easily and accurately calculated from the measured values of the pressure and temperature at the top of the quenching tower immediately after the pyrolysis furnace, and the measured values of the temperature or flow rate of the reflux limb returned to the top of the tower, and as a result. found that EDC can be thermally decomposed with a stable and high thermal decomposition rate.

That is, the present invention thermally decomposes EDC in a thermal decomposition furnace to produce VCM.
In an EDC thermal decomposition method in which decomposition products including hydrogen chloride and undecomposed EDC are quenched in a quenching tower located immediately after the pyrolysis furnace, the material balance and heat balance around the quenching tower and the top of the quenching tower are Based on the vapor-liquid equilibrium relationship in ED using
An EDC characterized in that the thermal decomposition rate of EDC is controlled by calculating the thermal decomposition rate of C and changing the thermal decomposition temperature based on the deviation between the calculated thermal decomposition rate and a desired thermal decomposition rate.
Provides a method for thermal decomposition of. In the present invention, the actual measurements of pressure, temperature, and flow rate used to calculate the thermal decomposition rate are as follows:
Any measuring device and method commonly used in industry may be used. The method of calculating and controlling the thermal decomposition rate of EDC in the present invention will be explained in detail with reference to FIG.

First, the thermal decomposition rate of EDC is calculated.

Now, assuming that the quenching tower that quenches the cracked gas from the pyrolysis furnace and the tank that stores the quenched liquid are operating in a steady state, we will look around the quenching tower (part A surrounded by the dashed-dotted line in Figure 1). Consider the mass balance and heat balance at

In material balance, the sum of the amount of cracked gas supplied to the quench tower and the amount of reflux returned from the tank is equal to the amount of gas distilled from the top of the quench tower.

Similarly, in the heat balance, the sum of the enthalpy of the cracked gas supplied to the quench tower and the enthalpy of the reflux liquid returned from the tank is equal to the enthalpy of the gas distilled from the top of the quench tower.

Such material balance and heat balance are calculated for each component, namely VC
This holds true for M, EDC and hydrogen chloride. Therefore,
The following six independent equations are obtained:

(Material balance) Vl + V2 = V3 (1) HI +
H2=H3 (2) E1+E2=E
3 (3) [wherein, V is V CM
, H is the flow rate of hydrogen chloride, E is the flow rate of EDC, the number 1 is the cracked gas supplied to the quenching tower, 2 is the reflux, and 3 is the gas to be distilled. ] t&ffi of the cracked gas supplied to the quenching tower is uniquely determined by the thermal decomposition rate (X) of the cracking furnace. Therefore, the formula (1
) to (3) are the thermal decomposition rate (X), the flow rate of each fraction of the reflux liquid and the gas distilled from the top of the quenching tower (V2, H2, E2
, V3, H3 and E3).

(Heat balance) Q (Vl) + Q (V2) = Q (V3) (4) Q
(Hl)+Q([2)=Q(H.3)
(5)Q(El)+Q(E2)=Q(E3)
(6) [wherein Q means the enthalpy of the component in parentheses. Regarding the specific ripeness of each component, by applying an approximation equation as a function of appropriate temperature, equations (4) to (6) can be calculated based on the temperature of the cracked gas (TI) supplied to the quenching tower, the temperature of the reflux liquid (T2 ), quenching tower top temperature (T3) and flow rate of each component (V2, H2, E
2, V3, H3 and E3 and the thermal decomposition rate (X).

Furthermore, a vapor-liquid equilibrium relationship is established at the top of the quenching tower. That is, the gas distilled from the top of the column is in equilibrium with the liquid phase present at the top of the quenching tower under the top temperature (T3) and the top pressure (P0).

Regarding the gas-liquid equilibrium relationship of the three-component system of EDC, hydrogen chloride, and VCM, La Houle's law can be applied, and there is no industrial problem even if the law of partial pressure and the ideal gas law are applied. It is known that. Furthermore, since the saturated vapor pressure of each fraction is generally given as a function of temperature, the equilibrium ratio K (mole fraction in the gas phase/mole fraction in the liquid phase) can be calculated based only on the top temperature (T3). Can be expressed as a function.

Now, each component in the distillate gas (VCM, hydrogen chloride and E
Let the molar fractions of DC) be VM3, HM3 and EM3,
If the mole fractions of the liquid phase at the top of the quenching tower are VLM, HLM, and ELM, then K(V)=P(V)/PO=VM3/
VLM (7) K(H)=P(H)/PO=HM3/
HLM (8) K(E)=P(E)/Po=EM3/
ELM (9) [where K is the equilibrium ratio of the components in parentheses (
mole fraction in gas phase/mole fraction in liquid phase), P is the saturated vapor pressure of the component in parentheses (function of tower top temperature T3). ] are obtained. Since the mole fraction of each component in the distillate gas can be calculated from the flow rates (V3, H3, and E3), equations (7) to (9) can be calculated for each fraction of the distillate gas flow 3.
1 (V 3 , H 3 and E 3 ), the tower top temperature (T 3 ), the tower top pressure (P 0 ), and the nominal mole fractions of the liquid phase at the top (VLM, HLM, and ELM). Furthermore, VLM+HLM+ELM=1 (1 0).

To summarize the above, the lO
The formulas (!) to (lO) are obtained. The variables in these equations are the thermal decomposition rate (X), the temperature of the cracked gas supplied to the quenching tower (T1), the flow rate (V2, H2, and E2) and temperature (T2) of each component of the reflux liquid, and the quenching The flow rate (V3, H3 and E3) and temperature (T
3), the quench tower overhead pressure (P o) and the mole fraction of the liquid phase at the top of the quench tower (VLMSHLM and ELM), with a total of 14 variables.

Therefore, an equation is obtained that includes any five of these variables (one is the target thermal decomposition rate (X)). It is preferable to select data that can be easily obtained, such as the degree of travel, pressure, or flow rate. In particularly preferred embodiments, the temperature and pressure are selected. That is, the temperature of the cracked gas supplied to the quenching tower (TI), the temperature of the reflux liquid to the quenching tower (T2), the temperature of the distillate gas from the top of the quenching tower (T3), and the tower top pressure (Po). be.

Therefore, in the most preferred embodiment of the invention, the thermal decomposition rate (X) of EDC is a function of temperature (T1, T2 and T3) and overhead pressure (PG). That is, X = fn(T
I, T2. T 3 , Po)E In the formula, rn means a function. ] Therefore, if the above-mentioned measured values of temperature and pressure are available, the thermal decomposition rate can be calculated.

One of the preferred aspects of the present invention is the temperature of the cracked gas (T
By fixing I) to an average value, in this case, the thermal decomposition rate can be calculated from the actual measured values of other temperatures (T2 and T3) and pressure (PQ). Immediately X=fn'(T2.T
3. Po) [In the formula, rn° means a function. ] Therefore, if the thermal decomposition rate (X) is calculated in advance for the assumed tower top temperature (T3), reflux liquid temperature (T2), and tower top pressure (P0), as shown in Figure 3, the thermal decomposition rate (X) is calculated in advance. (Temperature (TI) of cracked gas is 480℃,
The tower top pressure (P.) is 9. 7 ATM).

Based on this chart, conversely, the tower top temperature (T
3) and tower overhead pressure (PO) and reflux temperature (T2
) can be used to determine the thermal decomposition rate.

As is clear from FIG. 3, the thermal decomposition rate (X) can be approximated by a straight line. That is, the thermal decomposition rate is determined by the general formula: The slope of the straight line C at each temperature of the quenching tower reflux liquid in the relationship between the tower top temperature and the thermal decomposition rate is a constant. ], it can be calculated instantly with an accuracy that is industrially satisfactory.

The above method is the easiest method to calculate the thermal decomposition rate, but it is also possible to apply measured data without applying La Houle's law to the vapor-liquid equilibrium relationship, or to use measured data for specific heat, vapor pressure, etc. However, it is also possible to calculate the thermal decomposition rate with higher accuracy by numerical calculation.

In another aspect of the present invention, it is also possible to calculate the thermal decomposition rate (X) using the actual measured value of the reflux amount (R=V2+H2+E2) instead of the temperature of the reflux liquid returned to the quenching tower. . That is, X = rn'' (T 2 , T 3 , R) [where r
n'' means a function.] Since flow meters commonly used industrially are generally somewhat less accurate than thermometers, it is most preferable to use the actual measured value of the temperature of the reflux liquid as described above. However, depending on the required accuracy of the thermal decomposition rate to be calculated, or when using a more accurate flow meter, it is also possible to use the actual value of the reflux amount instead of the temperature of the reflux liquid. In this embodiment as well, the thermal decomposition rate can be calculated with higher accuracy by numerically calculating as described above.

The thermal decomposition rate can basically be determined from the chart in FIG. 3 as described above, but industrially it can be calculated easily and quickly by numerical calculation using a computer.

Next, a new EDC thermal decomposition temperature at which the deviation should be eliminated is determined from the deviation between the thermal decomposition rate calculated as described above and the desired thermal decomposition rate.

This determination can be made, for example, by proportional control, integral control, differential control, or an appropriate combination thereof; however, in the present invention, the formula: Y=-Kl)[Z+(
1/T) SZdtl [where Y is the amount of change in pyrolysis temperature, K
p is the proportional gain, Z is the deviation signal of the thermal decomposition rate, T is the integration time, and t is the time. This is done based on the following.

That is, this is performed by determining the amount of change in the thermal decomposition temperature from the deviation signal of the thermal decomposition rate. The proportional gain and q integral time can be determined based on the correlation between the reaction temperature and the thermal decomposition rate obtained from dynamic characteristic analysis of process operating variables, thermal decomposition reaction analysis, etc., and the response characteristics obtained from the actual equipment. can. A new pyrolysis temperature is set using the amount of change in the pyrolysis temperature calculated in this manner.

In an embodiment of the present invention, the above-mentioned calculation of the thermal decomposition rate and determination of a new thermal decomposition temperature are performed by calculating the thermal decomposition rate, and the new thermal decomposition rate is determined based on the difference between the calculated value and a predetermined thermal decomposition rate. Thermal decomposition rate indicating controller (X
Most preferably, the pyrolysis temperature setting value of the pyrolysis temperature indicating controller (TICl06) is automatically changed to the new pyrolysis temperature by the output signal from this controller.

Practical changes in the pyrolysis temperature are particularly preferably carried out by changing the amount of fuel supplied to the pyrolysis furnace;
It is preferable to change to a new pyrolysis temperature by interlocking the pyrolysis temperature indicator controller (TIC 106) and the fuel supply amount indicator controller (FIC 106).

As the thermal decomposition temperature, a temperature at an arbitrary position selected for monitoring plant operation can be used. For example, the temperature may be near the outlet or near the center of the pyrolysis reaction tube.

In the present invention, the pyrolysis rate can be calculated in the quenching tower immediately after the pyrolysis furnace, and fluctuations in the pyrolysis rate that change depending on the quality of EDC supplied to the pyrolysis furnace, the operating conditions of the pyrolysis furnace, etc. can be quickly and accurately calculated. It can also be calculated continuously. Therefore, if the thermal decomposition rate differs from a predetermined value, the thermal decomposition temperature can be automatically changed to quickly correct the thermal decomposition rate.

The method of the invention will be explained in more detail with reference to the accompanying drawings.

Figure 1 shows a VCM to which the EDC thermal decomposition method of the present invention is applied.
An example of a manufacturing process is shown below.

The EDC is connected to the pyrolysis reaction tube (1) of the pyrolysis furnace (106-2).
06-1), is partially thermally decomposed to become VCM and hydrogen chloride, and is sent to the quenching tower (107) along with undecomposed EDC.
is rapidly cooled. The quenched decomposition products and undecomposed EDC are distilled out from the top of the quenching tower, a part of which is condensed in a condenser (1 0 B) and stored in a tank (1 0 9). On the other hand, the entire amount of uncondensed gas containing hydrogen chloride and VCM as main components is supplied to the hydrochloric acid column 010). A portion of the condensate in the tank is refluxed to the quenching tower, and the remainder (is supplied to the hydrochloric acid tower).

Hydrogen chloride is recovered from the top of the hydrochloric acid tower, and VCM and EDC extracted from the bottom of the tower are sent to the PVC tower (12).

In this process, the outlet pressure of the condenser is determined by the flow rate of uncondensed gas supplied to the hydrochloric acid tower using a tank gas phase pressure indicating controller (P
The condenser outlet temperature is controlled by adjusting the amount of cooling water supplied to the condenser using a condensate temperature indicating controller (TIC108).

In addition, in this process, the EDC thermal decomposition rate (X) is determined by the quench tower top pressure indicator (PI107), the quench tower top temperature indicator (TIl07), the quench tower reflux liquid temperature indicator (TI109), or the quench tower top temperature indicator (TI109). Reflux liquid level indicator (FIl)
07) from the indicated value of the thermal decomposition rate indicating controller (XICl06
), and the pyrolysis temperature indicating controller (TIC10
6).

[Effects] According to the EDC pyrolysis method of the present invention, it is possible to calculate the pyrolysis rate of EDC with little time delay, and by controlling the pyrolysis temperature based on the deviation between this value and the desired pyrolysis rate. , the desired thermal decomposition rate can be stably maintained, and even if fluctuations occur, it is possible to return to the desired thermal decomposition rate in a short time.

As a result, it is possible to significantly improve the efficiency of fuel consumption required for pyrolysis of EDC, stabilize the quality of VCM, and further suppress the progress of coking in the pyrolysis reaction tube.

Next, the present invention will be specifically explained using Examples and Comparative Examples.

Example 1 In the VCM manufacturing process shown in FIG. 1 incorporating the instrumentation required for the EDC pyrolysis method of the present invention, 50% of EDC with a carbon tetrachloride concentration of 500 ppm was placed in a pyrolysis furnace.
3t/hr supply, the thermal decomposition temperature (TIC106) is 4
After setting the temperature to 75°C and stabilizing the thermal decomposition rate at 55%, the thermal decomposition rate indicating controller (X I C106) and the thermal decomposition temperature indicating controller (TICIO6) were automatically controlled. For several hours thereafter, the thermal decomposition rate remained at about 55±0.5%.

Next, the carbon tetrachloride concentration in EDC was set to 500 ppa.
When the temperature was increased from + to 1500+) pl1, the set value of the pyrolysis temperature was automatically changed downward by approximately 4°C (from 475°C to 471'C), and the pyrolysis rate temporarily increased to 56%. , it returned to 55% after about an hour.

At this time, the fuel supply amount and the 1.3-butanoene concentration in the VCM varied only slightly.

Comparative Example 1 As shown in Fig. 2, a conventional method was used using the measured values of VCMli (:F I 2 1 0) separated in the PVC distillation column (211) and EDCil (F I C 2 0 5) to be supplied. In an EDC pyrolysis process incorporating instrumentation to calculate the pyrolysis rate of EDC, the pyrolysis temperature (TIC206) was set at 475% under the same conditions as in Example 1.
℃, and the thermal decomposition rate was stabilized at 55%.

Afterwards, when the thermal decomposition rate varied by more than 1% after several hours of operation, attempts were made to change the thermal decomposition temperature using normal methods to suppress the fluctuation in the thermal decomposition rate. The decomposition rate fluctuated by 2% against a predetermined value of 55%.

Next, when the carbon tetrachloride concentration in EDC was increased from 500 ppm to 1500 ppII1, the thermal decomposition rate suddenly increased by about 3%. Therefore, the set value of the thermal decomposition temperature was gradually changed, and finally it was set to 471° C., thereby returning the thermal decomposition rate to the predetermined value. At this time, ED supplied to the pyrolysis furnace
The operation was carried out while calculating the thermal decomposition rate from the amount of VCM separated and recovered from the C and PVC tower, and it took about 5 hours to return and stabilize the thermal decomposition rate to 55%.

During this period, the fuel supply amount changed from 990k9/hr to 1150k
It fluctuated greatly at 9/hr, and 4. The concentration of 1.3 butadiene in VCM, which was around 0 ppm, temporarily decreased to 5 ppm.
．． increased to 5 ppm.

The results of Example 1 and Comparative Example 1 are shown in Table 1 and FIG. 4.

Table 1 Example 2 In a process employing the method of the present invention as in Example 1, the thermal decomposition temperature was set at 478°C and the thermal decomposition rate was 58°C.
After stabilizing the temperature at
) and pyrolysis temperature indicator controller (TICl06) are automatically controlled, and the EDC supply amount is increased from 48t/hr to 53t/hr.
increased to r.

The thermal decomposition rate temporarily dropped to 56%, but after about 1 hour,
The set value of the pyrolysis temperature was automatically changed from 478°C to 482°C, and the pyrolysis rate returned to 58%.

During this period, the fuel supply amount increased from 1000 ky/hr to 1hr, but the fluctuation was large during this time, and it took about 6 hours to stabilize it.

The results of Example 2 and Comparative Example 2 are shown in Table 2 and FIG. 5.

Table 2 Example 3 In a process employing the method of the present invention in the same manner as Examples 1 and 2, EDC supply amount was 53 t/hr and thermal decomposition rate was 5.
In order to observe the coke formation in the pyrolysis reaction tube under 8% conditions, the pressure loss in the pyrolysis reaction tube was measured for about 3 months after coke was removed from the pyrolysis reaction tube.

The pressure loss after 1 month is 1. 8 kg/c
Although it temporarily increased to m”1 0 0 kfF/hr,
Thereafter, the fluctuations were slight. Also, 1.3 in VCM
- There was also a slight variation in the concentration of putadiene.

Comparative Example 2 In a process employing the conventional method as in Comparative Example 1, after the thermal decomposition temperature was stabilized at 58%, the EDC supply rate was increased from 48 t/hr to 53 t/hr.

Although the pyrolysis temperature temporarily decreased from 478°C to 474°C, the pyrolysis temperature automatically returned to 478°C after about 1 hour using the conventional pyrolysis temperature control method.

However, the thermal decomposition rate decreased from 58% to 54%, so we gradually increased the thermal decomposition temperature setting manually and finally changed it to 483°C, thereby reducing the thermal decomposition rate to 54%.
It returned to 8%.

During this time, while calculating the thermal decomposition rate using the same method as in Comparative Example 1, it took about 6 hours to return it to a predetermined value and stabilize it. Note that the fuel supply amount is 1 0 0 0 as in Example 2.
It was finally 1100k9/hr from k9/hr,
Another month later, 2. 0 5 k9/ax", 2
2 months later. 3 kg/ax”, 2 after 3 months
．． 55 kg/ax”.

The average increase rate for 2 months is 0.0083k9/Ql
”・It was day.

Comparative Example 3 In a process employing the conventional method as in Comparative Examples 1 and 2, the EDC supply amount was 53 t/hr, and the thermal decomposition rate was 5.
The pressure drop in the pyrolysis reaction tube was measured under the condition of 6%.

After the coke was removed, the operation started and the pressure loss was 1.75k9/cm after one month as in Example 3.
However, after another month, it was 2. 1 k97cm
``2 months later, it was 2.35 kg/ax.''

The average rate of increase for 2 months is 0.0 1k9/cm”
・It was day.

Next, when we increased the thermal decomposition rate to 58% and operated it for one month, the pressure loss was 2. 35 kg/cm” to 2.
71 kg/c1. The average rate of increase for the past 1 months has been 0. 0 1 2 k9/cm”·day.

The conditions and results of Example 3 and Comparative Example 3 are shown in Table 3 and FIG. 6.

Table 3

[Brief explanation of drawings]

Fig. 1 is a flow sheet of the VCM manufacturing process applying the EDC pyrolysis method of the present invention, and Fig. 2 is a flow sheet of the vCM manufacturing process applying the conventional EDC pyrolysis method.
FIG. 3 is a chart showing the relationship between the thermal decomposition rate, the top temperature of the quenching tower, and the reflux liquid temperature, and FIGS. 4 to 6 are graphs showing the results of Examples and Comparative Examples. 106-1... Pyrolysis reaction tube, 106-2... Pyrolysis furnace, 107... Quenching tower, 10
8... Condenser, l09... Tank,! 10... Hydrochloric acid tower, txt... PVC tower, 206-1... Pyrolysis reaction tube, 206-2... Pyrolysis furnace, 207... Quenching tower, 20
8... Condenser, 209... Tank, 210... Hydrochloric acid tower, 211... PVC tower, FICI05... EDC
Supply flow rate indicator controller, FIC106... Fuel supply rate indicator controller, PI107... Quenching tower top pressure indicator, T
IC106...Pyrolysis temperature indicator controller, FI107.
... Quenching tower reflux liquid amount indicator, Tl 107... Quenching tower top temperature indicator, xtctos... Thermal decomposition rate indicating controller, TIC108... Condensate temperature indicating controller, TIl
09...Quieting tower reflux liquid temperature indicator, PICl09...
・Tank gas phase pressure indicator controller, prtio...VCM
Product flow rate indicator, FIC205...EDC supply flow rate indicator controller, FIC:206...Fuel supply amount indicator controller, TIC206...Pyrolysis temperature indicator controller, TI20
B...Condensate temperature indicator, FI210...VCM product flow rate indicator.

Claims (1)

[Claims] Vinyl chloride, in which 1,1,2-dichloroethane is pyrolyzed in a pyrolysis furnace and the decomposition product containing undecomposed 1,2-dichloroethane is quenched in a quenching tower located immediately after the pyrolysis furnace. In the method for producing monomers and hydrogen chloride, the temperature and pressure at the top of the quenching tower and the distillation of the quenching tower are determined based on the material balance and heat balance around the quenching tower and the gas-liquid equilibrium relationship at the top of the quenching tower. The thermal decomposition rate of 1,2-dichloroethane is calculated using three measured values of the temperature of the reflux liquid, which is a part of the gas condensate and is returned to the quenching tower, and the calculated thermal decomposition rate and the desired thermal decomposition rate are calculated. 1, characterized in that the thermal decomposition rate of 1,2-dichloroethane is controlled by changing the thermal decomposition temperature based on the deviation from the
A method for thermally decomposing 2-dichloroethane. 2. The method for thermally decomposing 1,2-dichloroethane according to claim 1, characterized in that a measured value of the reflux amount is used instead of the temperature of the reflux liquid.