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) with a mean temperature; mixing a compressed warm recycle stream (104) with a controlled liquid nitrogen stream (110) in a stainless steel mixing zone (107), thereby producing a cool recycle stream (112), 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 nitrogen 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. Temperature sensor119senses the mean fluid temperature of compressed stream104, and transfers this temperature information to temperature control valves109,116,117, and105as needed. In one embodiment of the present invention, three temperature sensors (119A,119B,119C) are used, thereby allowing the voting of two out of three, in order to improve reliability and accuracy.

Compressed warm recycle stream104may pass through first isolation valve106and first control valve116, after which it enters stainless steel mixing zone107. Liquid nitrogen stream108enters temperature control valve109, thus generating controlled liquid nitrogen stream110, which then enters stainless steel mixing zone107.

The mean temperature of compressed stream104is 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.

The mean temperature of compressed warm recycle stream104is compared to a predetermined minimum temperature control valve set point. If the mean temperature is less than this predetermined minimum temperature control valve set point, temperature control valves116,117close, and normally closed temperature control valve105opens, thereby allowing the compressed, warm recycle stream to bypass the stainless steel mixing zone.

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), where said compressed warm recycle stream (104) has a mean fluid temperature,

monitoring the mean fluid temperature and comparing the mean fluid temperature to a predetermined minimum temperature,

closing the temperature control valve (109), closing a first control valve (116), a closing second control valve (117), and opening a bypass control valve (105) if the first mean fluid temperature is less than the predetermined minimum temperature,wherein the first control valve (116) and the second control valve (117) isolate the stainless steel mixing zone, andwherein the bypass valve (105) allows the warm recycle stream (102) to return to the reactor (101),

comparing the mean fluid temperature to a predetermined control valve set point, thereby defining a temperature deviation,

mixing a compressed warm recycle stream (104) with a controlled liquid nitrogen 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,

modulating a temperature control valve (109) to vary the controlled liquid nitrogen 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).

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

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

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