Cold Box Process Integration for Natural Gas Liquid Recovery
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Solution Overview
Problem
Current natural gas liquid recovery systems face inefficiencies in energy consumption and heat recovery due to the lack of effective process integration, particularly in the heating and cooling processes required for transforming raw hydrocarbons into various petroleum products.
Innovation Solution
The implementation of a natural gas liquid recovery system that includes a cold box with a plate-fin heat exchanger and a refrigeration system using a primary refrigerant mixture of hydrocarbons, with LP and HP separators, and a subcooler, which transfers heat efficiently between hot and cold fluids, optimizing heat exchange across multiple compartments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If traditional natural gas liquid recovery systems are used without process integration, then the system structure is simple, but energy consumption is high and heat recovery is inefficient
Solution Approach 1:
The patent combines multiple heat exchange operations into a single integrated cold box system where hot and cold streams exchange heat through shared walls. This merging of heat exchange functions reduces the number of separate equipment units, minimizes heat loss to the environment, and improves overall energy efficiency while maintaining manageable system complexity through modular design.
Solution Approach 2:
The cold box system performs multiple functions simultaneously: it cools process streams, recovers heat from hot streams, condenses natural gas liquids, and pre-cools feed gas. This multi-functionality allows a single integrated structure to replace multiple separate equipment units, reducing energy consumption while providing comprehensive process integration.
2Loss of energy
If process integration with cold box is implemented, then heat recovery is enhanced and energy consumption is reduced, but the heat transfer area requirement decreases which may affect heat exchange efficiency
Solution Approach 1:
The cold box employs local quality optimization by configuring heat exchange walls with varying thermal conductivities and surface areas at different locations. Hot and cold streams are arranged to maximize temperature differences where most beneficial, and the shared walls are designed with specific thermal properties to optimize heat transfer in each local region, achieving high heat recovery efficiency with reduced total heat transfer area.
Solution Approach 2:
The system utilizes parameter changes by varying the temperature, pressure, and flow rates of hot and cold streams to optimize heat transfer conditions. By dynamically adjusting these parameters and arranging streams at different temperature levels within the cold box, the system maximizes the driving force for heat transfer, enabling effective heat recovery with compact heat exchange surfaces.
3Productivity
If multiple refrigerant separators are used for phase separation, then the refrigeration system efficiency is improved, but the device complexity increases
Solution Approach 1:
The refrigeration system is segmented into multiple separators operating at different pressure levels (high-pressure and low-pressure separators). This segmentation allows phase separation to occur at optimal conditions for each pressure level, improving refrigeration efficiency by ensuring proper liquid-vapor separation before compression and expansion stages, while the modular separator design keeps the complexity manageable.
Solution Approach 2:
The separators act as intermediary devices between different pressure levels and temperature stages in the refrigeration cycle. They mediate the phase transition and pressure adjustment processes, ensuring that refrigerant enters each stage of the cycle in the correct state. This intermediary function improves overall system efficiency by preventing liquid carryover to compressors and ensuring proper expansion conditions.
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
This configuration reduces energy consumption, enhances heat recovery, and decreases operating costs by allowing for the production of high-purity natural gas liquids and sales gas, while also minimizing the required heat transfer area and equipment costs.
Implementation Method 1
The cold box includes a plate-fin heat exchanger including compartments. The cold box is configured to transfer heat from hot fluids in the natural gas liquid recovery system to cold fluids in the natural gas liquid recovery system.
Implementation Method 2
The refrigeration system includes a primary refrigerant including a first mixture of hydrocarbons.
Implementation Method 3
The LP refrigerant separator is configured to receive a first portion of the primary refrigerant and configured to separate phases of the first portion of the primary refrigerant into a LP primary refrigerant liquid phase and a LP primary refrigerant vapor phase.
Implementation Method 4
The HP refrigerant separator is configured to receive a second portion of the primary refrigerant and configured to separate phases of the second portion of the primary refrigerant into a HP primary refrigerant liquid phase and a HP primary refrigerant vapor phase.
Implementation Method 5
The subcooler is configured to transfer heat between the first portion of the primary refrigerant and the LP primary refrigerant vapor phase.
Data Source
AI summary
This specification relates to operating industrial facilities, for example, crude oil refining facilities or other industrial facilities that include operating plants that process natural gas or recover natural gas liquids.