METHOD FOR LEAKAGE-PROOF STORAGE OF LIQUEFIED CHLORINE

Abstract

The invention relates to a method for the leakage-proof storage of liquefied chlorine under increased pressure in pressure tanks, in which up to 20 wt. % polyvinyl chloride (PVC) or chlorinated polyvinyl chloride (cPVC) is placed in the pressure tank prior to filling the pressure tank with liquefied chlorine.

Claims

1.-4. (canceled)

5. A method for the leakproof storage of liquefied chlorine under increased pressure in pressure vessels, comprising charging the pressure vessel with up to 20% by weight of polyvinyl chloride (PVC) or chlorinated polyvinyl chloride (cPVC) before the filling the pressure vessel with liquefied chlorine.

6. The method as claimed in claim 5, wherein the pressure vessel is charged with from 1 to 20% by weight of PVC or cPVC.

7. The method as claimed in claim 5, wherein the molecular weight Mn of the PVC or cPVC is from 20 000 to 250 000.

8. The method as claimed in claim 5, wherein the pressure in the pressure vessel after pressurizing with chlorine is 2 to 15 bar.

Description

EXAMPLE FOR PVC/CPVC

[0014] The measurements were performed in an assembly for the measurement of phase equilibria. The assembly comprises a high-pressure view cell, pumps for filling the view cell with chlorine, and a vacuum vessel. The high-pressure view cell consists of a sapphire glass cylinder and stainless steel flanges (material stainless steel 316, volume 325 cm.sup.3, maximum pressure: 10 MPa).

[0015] The temperature is measured by a calibrated Pt-100 platinum resistance thermometer and the pressure by a calibrated precision pressure transmitter (Keller PA-25 HTC), which is directly coupled to the cell. Compressed chlorine is added by means of a screw pump (Sitec). The upper flange of the view cell is provided with openings, through which it is possible to simulate a sudden fall in pressure in the vessel by operating a valve.

[0016] For this, the high-pressure view cell is connected, via the valve, to a vacuum vessel (volume 20 L) in which the escaping gas is collected.

[0017] During each experiment, the pressure and temperature in the vacuum vessel, the pressure and temperature in the high-pressure view cell, and the time taken to reach a pressure of 1 bar abs. in the vacuum vessel were measured.

Example 1: Chlorine Release from Liquid Chlorine

[0018] For this example, liquid chlorine (Linde, 99.999%) was added to the cell until the level of the liquid chlorine was about 2 centimeters. The pressure in the cell was equal to the vapor pressure of chlorine: 7.1 bar at 22 C. The pressure in the cell was then released abruptly against vacuum by opening a valve. The valve was closed once the pressure in the vacuum vessel had reached 1 bar abs. The time taken to reach this pressure was 69 s.

Example 2: Chlorine Release from a Mixture of Chlorine and cPVC (13% by Weight)

[0019] In a first step, the high-pressure view cell was charged with 48 g of polyvinyl chloride, PVC (Aldrich Chemistry, product number 189588-1 kg, having a number-average molecular weight Mn of 35 000). Liquid chlorine (Linde, 99.990%) was added to a pressure of 7.1 bar abs. and a temperature of 22 C., so as to form a liquid PVC/chlorine solution. The resulting proportion of PVC in the solution was 13% by weight. After addition of the chlorine, the PVC is first converted to cPVC with liberation of HCl. The cell was accordingly allowed to stand for a period of 2 h and the HCl evolved released from the cell.

[0020] The pressure in the vessel was then released abruptly against vacuum by opening a valve. This released chlorine to an end pressure in the vacuum vessel of 1 bar abs. On opening, a froth developed that rose to a height of several centimeters and persisted even after closing the valve.

[0021] The time taken to reach the pressure of 1 bar abs. in the vacuum vessel was 145 s.

Example 3: Chlorine Release from a Mixture of Chlorine and cPVC (16% by Weight)

[0022] The cell was again charged with polyvinyl chloride and chlorine added until the proportion of PVC in the solution was 16% by weight. After addition of the chlorine, the PVC is first converted to cPVC with liberation of HCl. The cell was accordingly allowed to stand for a period of 2 h and the HCl evolved released from the cell.

[0023] The pressure in the vessel was then released abruptly against vacuum by opening a valve. This released chlorine to an end pressure in the vacuum vessel of 1 bar abs.

[0024] On opening, a froth developed that rose to a height of several centimeters and persisted even after closing the valve.

[0025] The time taken to reach the pressure of 1 bar abs. in the vacuum vessel was 179 s.

[0026] Examples 2 and 3 show a slowing of chlorine release by a factor of 2-2.5 relative to example 1.