Integrated Cold Box Heat Exchange 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 integration of heat exchange processes, leading to increased utility usage and operating costs in petroleum refineries.
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 with a primary and secondary refrigerant loop, utilizing a mixture of hydrocarbons as refrigerants to enhance heat transfer and reduce energy consumption through optimized heat exchange across multiple process streams.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If traditional heat exchange processes are used in natural gas liquid recovery systems, then heat recovery is achieved, but energy consumption is high and utility usage increases
Solution Approach 1:
The patent combines multiple heat exchange processes into an integrated system where the cold box serves as both a heat exchanger and a refrigeration component. The refrigeration system is merged with the natural gas liquid recovery process, allowing heat to be transferred from hot process streams to cold process streams and refrigerants within the same equipment, thereby reducing energy consumption and improving heat recovery efficiency.
Solution Approach 2:
The cold box is designed to perform multiple functions simultaneously: it acts as a heat exchanger for process-to-process heat transfer, a heat exchanger for refrigerant-to-process heat transfer, and a condensation vessel. This multi-functionality eliminates the need for separate equipment and reduces overall energy consumption in the natural gas liquid recovery system.
2Loss of energy
If multiple separate heat exchangers are used for heat transfer, then heat exchange is achieved, but the total heat transfer area required increases
Solution Approach 1:
The patent merges multiple heat exchange functions into a single cold box unit with integrated plate-fin heat exchangers. Instead of using separate heat exchangers for refrigerant-to-process heat transfer and process-to-process heat transfer, the system combines these functions in one compact unit, reducing the total heat transfer area required while maintaining efficient heat transfer.
Solution Approach 2:
The refrigeration system is nested within the cold box structure, with refrigerant heat exchangers positioned inside or integrated with the process heat exchanger compartments. This nesting arrangement allows multiple heat transfer surfaces to be contained within a compact volume, reducing the overall heat transfer area footprint.
3Temperature
If conventional refrigeration systems are used, then refrigeration is provided, but power consumption in refrigerant compression is high
Solution Approach 1:
The system uses waste heat from hot process streams to pre-cool the refrigerant before compression and to condense the refrigerant vapor after evaporation. This self-service approach utilizing process heat reduces the workload on the compression system and significantly lowers power consumption while maintaining the required refrigeration temperatures.
Solution Approach 2:
The patent employs a two-stage refrigeration system with different refrigerants optimized for different temperature ranges. The first stage uses a refrigerant optimized for lower temperatures, while the second stage uses a different refrigerant for higher temperatures, allowing each stage to operate at optimal efficiency and reducing overall power consumption.
4Ease of operation
If process streams are not integrated, then operational flexibility is maintained, but maintenance and operational costs increase
Solution Approach 1:
The patent integrates the refrigeration system with the natural gas liquid recovery process streams, allowing heat to be exchanged between refrigerant loops and process streams within the same cold box. This integration reduces operational costs by eliminating the need for separate utility systems while maintaining operational flexibility through independent control of each process stream.
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 the total heat transfer area required, decreases power consumption in refrigerant compression, and integrates process streams to lower maintenance and operational costs, resulting in a more efficient and cost-effective natural gas liquid recovery process.
Implementation Method 1
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 primary refrigerant loop includes a primary refrigerant including a first mixture of hydrocarbons
Implementation Method 3
The refrigeration system includes a subcooler configured to transfer heat between the primary refrigerant of the primary refrigerant loop and the secondary refrigerant of the secondary refrigerant loop
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.