REACTOR LIQUID COOLDOWN METHOD

A reactor liquid cool down method is provided. The method includes obtaining a warm recycle stream (102) from a reactor (101) and compressing the warm recycle stream (102), thereby producing a compressed warm recycle stream (104); mixing a compressed warm recycle stream (104) with a controlled liquid cryogen stream (110) in a stainless steel mixing zone (107), thereby producing a cool recycle stream (112), wherein the cool recycle stream has a mean fluid temperature, monitoring the mean fluid temperature and comparing the mean fluid temperature to a predetermined control valve set point, thereby defining a temperature deviation; modulating a temperature control valve (109) to vary the controlled liquid cryogen stream (110) in order to produce a temperature deviation that is less than a predetermined value, and returning the cool recycle stream (112) to the reactor (101).

DESCRIPTION OF PREFERRED EMBODIMENTS

The proposed solution may include a stainless piping skid that may be mounted on a non-DOT trailer (capable of being pulled by non-DOT pickup trucks). The customer's entire recycle stream is redirected through temporary piping into the skid, where liquid nitrogen could be injected without risk to the customer's piping.

The skid would include automatic bypass and isolation valves as well as a temperature control valve and multiple thermocouples (for voting purposes). The customer's stream would enter the skid through the first isolation valve. After a sufficient length of pipe to ensure adequate mixing, the combined stream would pass over three thermocouples before exiting the skid through the second isolation valve back Into the customer's piping.

The thermocouples would be used to isolate and bypass the skid in the event a predetermined low temperature limit was reached (to be agreed upon with the customer—2 out of 3 voting). The liquid nitrogen would enter the piping via a temperature control valve—the thermocouples would also be used as the control point (also to be agreed upon with the customer). Liquid nitrogen pressure would be provided by a small mobile nitrogen pumping and vaporization unit or simply the centrifugal pump on the liquid nitrogen transport. The skid would be controlled by a simple PLC. Power and air would be provided by the transport or pumper. In this manner, customers with incompatible piping in their existing system would be able to enjoy the benefits of liquid cooldown.

Turning toFIG. 1, reactor101is to be cooled down. In one embodiment of the present invention, warm recycle stream102is removed from reactor101and introduced into compressor103. Compressed warm recycle stream104may pass through first isolation valve106, after which it enters stainless steel mixing zone107. Liquid cryogen stream108enters temperature control valve109, thus generating controlled liquid nitrogen stream110, which then enters stainless steel mixing zone107. Liquid cryogen stream108may be any compatible cryogen known in the art. Liquid cryogen stream108may be liquid nitrogen.

Compressed warm recycle stream104and controlled liquid nitrogen stream110are mixed within stainless steel mixing zone107, thereby producing cool recycle stream112, which exhibits a mean fluid temperature. If the temperature of warm recycle stream102deviates from a predetermined temperature, compressed warm recycle stream104may be bypassed through line115and normally closed valve105.

Temperature sensor111senses the mean fluid temperature, and transfers this temperature information to temperature control valve109. In one embodiment of the present invention, three temperature sensors (111A,111B,111C) are used, thereby allowing the voting of two out of three, in order to improve reliability and accuracy. The mean temperature is compared to a predetermined temperature control valve set point. Temperature control valve109then adjusts controlled liquid nitrogen stream110in order to bring the mean temperature closer to the predetermined temperature control valve set point.

Stainless steel mixing zone is of sufficient length to obtain the proper mixing of controlled liquid nitrogen stream110and compressed warm recycle stream104. For example, if natural turbulence is the sole mixing mechanism, as many as 100 diameters of mixing length may be necessary. If one or more static mixer is used, then less than 10 diameters will be necessary, preferably between 4 and 6 diameters, more preferably 5 diameters. Once the mixing is complete, cool recycle stream112passes through second isolation valve113and is returned to reactor101.

A reactor liquid cool down method, comprising;obtaining a warm recycle stream (102) from a reactor (101) and compressing the warm recycle stream (102), thereby producing a compressed warm recycle stream (104),mixing the compressed warm recycle stream (104) with a controlled liquid cryogen stream (110) in a mixing zone (107), thereby producing a cool recycle stream (112), wherein the cool recycle stream has a mean fluid temperature,monitoring the mean fluid temperature and comparing the mean fluid temperature to a predetermined control valve set point, thereby defining a temperature deviation,modulating a temperature control valve (109) to vary the controlled liquid cryogen stream (110) in order to produce a temperature deviation that is less than a predetermined value, andreturning the cool recycle stream (112) to the reactor (101).

The reactor liquid cool down method as described above, further comprising;monitoring a first mean fluid temperature of the warm recycle stream (102),closing the temperature control valve (109), closing a first valve (106), a closing second valve (113), and opening a bypass valve (105) if the first mean fluid temperature is less than a predetermined minimum temperature,
wherein the first valve (106) and the second valve (113) isolate the stainless steel mixing zone, and
wherein the bypass valve (105) allows the warm recycle stream (102) to return to the reactor (101).

The reactor liquid cool down method as described above, wherein the mixing zone (107) is stainless steel.

The reactor liquid cool down method as described above, wherein the mean fluid temperature is monitored by temperature indicators.

The reactor liquid cool down method as described above, further comprising at least three temperature indicators, wherein a two out of three voting protocol is utilized.

The reactor liquid cool down method of as described above, wherein the liquid cryogen is liquid nitrogen.