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Extended Membrane Pressure Measurements

IP.com Disclosure Number: IPCOM000243462D
Publication Date: 2015-Sep-23
Document File: 6 page(s) / 201K

Publishing Venue

The IP.com Prior Art Database

Abstract

IP piping pressure measurements historically have a dead pocket where accumulation of waxes or other substances can occur which impacts the pressure measurement accuracy. Extended membrane pressure measurements resolve these issues as the membrane is flush with the ID of the IP pipe. These measurements are used on the Low Pressure Separator off gas line, on the line from the High Pressure separator to the HP recycle and for leak gas flow monitoring in buffered packing stacks on reciprocating compressors.

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Extended Membrane Pressure Measurements

Abstract:

IP piping pressure measurements historically have a dead pocket where accumulation of waxes or other substances can occur which impacts the pressure measurement accuracy. Extended membrane pressure measurements resolve these issues as the membrane is flush with the ID of the IP pipe. These measurements are used on the Low Pressure Separator off gas line, on the line from the High Pressure separator to the HP recycle and for leak gas flow monitoring in buffered packing stacks on reciprocating compressors.

Background


1. General process description :

A process flow block diagram Low Density Polyethylene (LDPE Process) is provided in figure below :

High purity polymerization grade ethylene is supplied to the battery limit and is boosted by the primary compressor. In the suction manifold of the secondary compressor, the gas from the high pressure recycle system is combined with the ethylene from the primary compressor. The secondary compressor will then boost the pressure from the primary compressor discharge pressure to the reactor operating pressure.

After polymerization, the reaction fluid is decompressed through the high pressure letdown valve. The mixture is then fed to the high pressure separator where polymer is separated from


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unreacted ethylene. The offgas from the high pressure separator goes to the high pressure recycle system and returned to the secondary compressor suction. The molten polymer is decompressed through the low pressure letdown valve and fed to the low pressure separator and then to the extruder.

The purge gas compressor boosts the low pressure separator offgas along with the primary and secondary compressors cylinder leak gas to the suction pressure of the primary compressor (ethylene pipeline pressure).

The polymer melt from the low pressure separator is fed to the hot melt extruder.

The polymer strands leaving the die of the extruder are underwater cut into pellets. The pellets are cooled, dried and transferred to weigh bins or blenders.


2. Pressure measurement details

a) Pressure measurements in the IP piping...