Hydroprocessing Power-Recovery Turbines for Hydrogen Cooling
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Solution Overview
Problem
In hydroprocessing units, the conventional method of recycling hydrogen is inefficient due to unnecessary energy wastage and temperature control challenges, limiting reactor throughput and causing catalyst deactivation and runaway reactions.
Innovation Solution
The integration of power-recovery turbines in the quench hydrogen lines allows for energy recovery and temperature control, enabling more efficient hydrogen cooling and increased feed capacity by generating electricity from the turbine system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If all recycle hydrogen is compressed to required pressure to pass through heating equipment and reactor, then hydrogen is available for reactions and temperature control, but energy is wasted in compressing hydrogen that bypasses heating sections as quench gas
Solution Approach 1:
The hydrogen recycle stream is divided into two separate compression paths: one for reactor inlet hydrogen requiring full pressure, and another for quench hydrogen requiring only partial pressure. This segmentation allows each compressor to be sized and operated optimally for its specific pressure requirement, eliminating the waste of compressing quench hydrogen to full reactor pressure.
Solution Approach 2:
The pressure parameter for quench hydrogen is changed from full reactor pressure to a lower intermediate pressure sufficient for its quench function. By adjusting the pressure parameter to match actual process needs rather than maximum requirements, energy consumption is reduced while maintaining effective temperature control in the reactor.
2Productivity
If quench hydrogen is used to control reactor temperature, then safe operating temperatures are maintained, but throughput is limited by available cooling capacity
Solution Approach 1:
The cold quench hydrogen, which was previously serving only as a cooling medium and wasting its thermal energy difference, is now used to drive a turbine. The temperature and pressure differential of the quench hydrogen is converted into beneficial electrical power, while the cooling function is maintained through alternative means or optimized quench strategies.
Solution Approach 2:
The quench hydrogen stream is given multiple functions: it continues to provide necessary temperature control in the reactor while simultaneously serving as a power generation resource. This multi-functionality increases overall system productivity by generating electricity that can offset operational costs and potentially increase net throughput.
3Power
If power-recovery turbines are added to quench hydrogen lines, then electricity is generated and cooling efficiency is enhanced, but device complexity and initial cost increase
Solution Approach 1:
The quench hydrogen stream, which already exists in the system with significant pressure and temperature differential, is utilized to generate power for the hydroprocessing unit itself. The system serves its own power needs using its own process streams, reducing external power requirements and improving overall energy self-sufficiency.
Solution Approach 2:
The pressure and temperature parameters of the quench hydrogen are exploited as driving forces for turbine power generation. By changing the operational parameters to enable turbine expansion, the system converts thermal and pressure energy into electrical power, enhancing overall energy 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
This approach enhances cooling efficiency, increases hydroprocessing reactor feed capacity by 5%, and pays for itself through electricity generation while maintaining safe reactor temperatures, thus addressing energy wastage and throughput limitations.
Implementation Method 1
directing a second portion of the hydrogen stream through a power-recovery turbine
Implementation Method 2
a first portion of the hydrogen stream is combined with a hydrocarbon feed stream to form a combined feed stream. The combined feed stream is heated and the heated combined feed stream is introduced into a hydroprocessing reaction zone
Data Source
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AI summary
Methods and apparatus for recovering power in a hydroprocessing process are described. The method involves the use of a power-recovery turbine in place of, or in addition to, a control valve. A hydrocarbon feed stream is combined with a portion of a hydrogen stream. The combined stream is heated, and the heated stream is introduced into a hydroprocessing reaction zone having at least two beds. The heated stream is contacted with a first hydroprocessing catalyst to form a first hydroprocessed stream. At least part of a portion of the hydrogen stream is combined with the first hydroprocessed stream to form a first quenched hydroprocessed stream. The first quenched hydroprocessed stream is contacted with a second hydroprocessing catalyst to form a second hydroprocessed stream. At least a portion of the second portion of the hydrogen stream is directed through a power-recovery turbine to generate electric power.