Single column nitrogen rejection unit with side draw heat pump reflux system and method
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Solution Overview
Problem
Current nitrogen removal processes from natural gas or liquid natural gas streams, particularly using nitrogen rejection units, face inefficiencies and high power requirements, necessitating improved methods for purification and refrigeration.
Innovation Solution
A system incorporating a heat pump system with a distillation column and heat exchanger configuration that includes reflux compression, cooling, and separation stages to efficiently remove nitrogen, utilizing refrigeration recovery and multiple reflux streams for enhanced refrigeration and reduced energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional nitrogen rejection units are used to remove nitrogen from natural gas streams, then nitrogen purification is achieved, but power requirements and energy consumption increase
Solution Approach 1:
The patent utilizes phase transitions of natural gas components through controlled heating and cooling cycles. The heat pump system cycles between heating mode (to vaporize liquid natural gas and separate nitrogen) and cooling mode (to condense vapors and recover refrigeration), leveraging the phase change properties of hydrocarbons to achieve nitrogen rejection while recovering energy
Solution Approach 2:
The system dynamically changes temperature and pressure parameters through the heat pump's heating and cooling cycles. By varying these parameters, the system controls the vaporization and condensation points of different gas components, enabling selective nitrogen separation while optimizing energy consumption through parameter optimization
2Measurement precision
If conventional nitrogen rejection processes are used, then nitrogen removal is achieved, but refrigeration efficiency decreases
Solution Approach 1:
The heat pump system incorporates feedback through its cycling operation, where the condensed vapors from the cooling phase provide refrigeration that feeds back into the system. This recovered refrigeration is used to pre-cool incoming feed or maintain condensation temperatures, creating a self-sustaining thermal cycle that reduces external energy input and improves overall refrigeration efficiency
Solution Approach 2:
The system recovers thermal energy that would otherwise be discarded. The heat pump captures waste heat from the condensation process and the warmed nitrogen vapor, redirecting it to provide refrigeration for subsequent cycles. This energy recovery mechanism significantly reduces the net energy loss and improves refrigeration efficiency
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system effectively removes nitrogen from natural gas streams while providing additional refrigeration, improving efficiency and reducing power requirements, thereby enhancing the overall nitrogen rejection process.
Implementation Method 1
A reflux compressor is configured to receive and compress fluid from the withdrawn vapor warming passage of the main heat exchanger
Implementation Method 2
cooling and partially condensing the compressed withdrawn vapor to form a first mixed phase reflux stream
Implementation Method 3
a main heat exchanger including a main feed cooling passage, a withdrawn vapor warming passage, main reflux stream cooling passage, a reflux vapor cooling passage
Implementation Method 4
A distillation column includes a feed inlet, a return vapor outlet, a side vapor outlet port, first and second reflux inlet ports and a bottoms liquid outlet
Data Source
AI summary
A system for removing nitrogen from a natural gas fluid feed stream includes a main heat exchanger that receives the natural gas fluid feed stream. A distillation column receives a cooled fluid stream from the main heat exchanger and features a return vapor outlet and a side vapor outlet port. The return vapor outlet provides nitrogen vapor to the main heat exchanger which is warmed therein. The side vapor outlet port provides vapor to the main heat exchanger and a reflux compressor receives and compresses the resulting fluid from the main heat exchanger. A reflux aftercooler receives and cools fluid from the reflux compressor, directs cooled fluid to the main heat exchanger and the resulting fluid is directed to a reflux separation device. The reflux separation device has a vapor outlet and a liquid outlet. The vapor outlet of the reflux separation device directs fluid to the main heat exchanger so that fluid is directed to the first reflux inlet port of the distillation column. The liquid outlet of the reflux separation device directs fluid to a second reflux inlet port of the distillation column.