Multistage Pump with Variable Specific Speed Impellers for Dense Phase CO2
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Solution Overview
Problem
There is a need for a subsea pump capable of efficiently injecting compressible fluids in the dense phase into a subterranean region, as existing technologies are inefficient in handling high-compressibility fluids with low viscosity and high density, typically requiring complex control algorithms and larger equipment.
Innovation Solution
A multistage pump with radial or semi-axial impellers, where at least two impellers have different specific speeds, configured for subsea installation, allowing efficient conveyance of compressible fluids in the dense phase without the need for complex control algorithms or additional equipment, and featuring a balance drum and center bush to manage axial thrust and rotor stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional pumps are used for compressible fluids in dense phase, then the equipment size and complexity increase, but the pumping efficiency and reliability decrease
Solution Approach 1:
The patent applies parameter changes by varying the specific speed of impellers along the pump stages. The first impeller has a higher specific speed than subsequent impellers, optimizing each stage for the local fluid conditions. This gradient in specific speed parameters enables efficient handling of compressible fluids in dense phase while maintaining a relatively simple single-subsea-unit configuration, thereby improving productivity without significantly increasing device complexity
Solution Approach 2:
The pump is segmented into multiple stages with impellers having different specific speeds. Each impeller stage is designed to handle the changing fluid properties as the fluid progresses through the pump, with the first impeller optimized for lower pressure conditions and subsequent impellers optimized for higher pressure conditions. This segmentation allows efficient compression of dense phase fluids while keeping each individual impeller design relatively simple
2Productivity
If separation and compression of CO2 is performed at topside, then processing capability is achieved, but space requirements and infrastructure complexity increase
Solution Approach 1:
The patent merges the separation and compression functions into a single subsea unit that operates directly on the dense phase CO2 as it is produced. By combining these functions at the source and utilizing the in-situ dense phase conditions, the system eliminates the need for separate topside separation facilities and compression equipment, thereby achieving the required processing capability while significantly reducing topside space requirements and infrastructure complexity
Solution Approach 2:
The system leverages the natural dense phase state of CO2 at subsea conditions to perform separation and compression without requiring additional topside processing equipment. The dense phase fluid is directly compressed and reinjected, allowing the system to serve itself by utilizing the inherent properties of the fluid at its production conditions, thus eliminating the need for extensive topside infrastructure
3Productivity
If multistage pump with different specific speed impellers is used, then pumping efficiency for dense phase fluids improves, but manufacturing complexity increases
Solution Approach 1:
While the patent does change the specific speed parameter of impellers across stages to optimize conveyance efficiency, each impeller remains a standard centrifugal impeller design that can be manufactured using conventional methods. The parameter change is achieved through variations in impeller diameter and rotational speed rather than fundamentally different impeller geometries, keeping manufacturing complexity at an acceptable level while significantly improving conveyance efficiency for dense phase fluids
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 multistage pump effectively conveys compressible fluids over the entire dense phase range, reducing equipment size and operational complexity, enhancing efficiency and reliability, and eliminating the need for topside processing and compression of CO2, thus optimizing energy efficiency and infrastructure requirements.
Implementation Method 1
The pump unit comprises a plurality of impellers for conveying a compressible fluid from a pump inlet to a pump outlet... each impeller is configured as a radial or semi-axial impeller... driven for a rotation about an axial direction so that all impellers are commonly rotated about the axial direction
Data Source
AI summary
A multistage pump for installation on a sea ground includes a common housing, a pump unit arranged in the common housing, a drive unit arranged in the common housing, and a coupling. The common housing includes a pump inlet and a pump outlet, the pump unit including a plurality of impellers to convey a compressible fluid from the pump inlet to the pump outlet, and a pump shaft, on which each impeller is mounted, each impeller being a radial or semi-axial impeller. The drive unit includes a drive shaft to drive the pump shaft, and an electric motor configured to rotate the drive shaft about an axial direction. The coupling couples the drive shaft to the pump shaft. The pump unit conveys the fluid in a dense phase at the pump outlet, and at least two impellers of the plurality of impellers have a different specific speed.