Variable Flow Centrifugal Compressor Load Management
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Solution Overview
Problem
Centrifugal compressors face challenges in efficiently compressing gas with a variable flow rate, particularly when powered by renewable energy sources, leading to instability and increased electricity consumption due to frequent shutdowns and excessive recycling.
Innovation Solution
A multistage compression system is operated by dynamically adjusting the load of centrifugal compressors and minimizing recycling, by sequentially shutting down or putting compressors in low power mode, while maintaining the load above anti-surge control points using the main recycle system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If centrifugal compressors are operated at maximum capacity continuously to maximize net compressed gas output, then productivity is improved, but energy consumption increases and adaptability to variable flow rates deteriorates
Solution Approach 1:
The patent implements dynamic load adjustment by sequentially shutting down compressors or putting them in low power mode based on real-time gas feed flow rates. The system transitions from static maximum capacity operation to dynamic operational modes (full load, minimum load, low power, shutdown) that adapt to varying renewable energy availability and gas production rates, thereby reducing energy waste during low-demand periods while maintaining high productivity during peak periods.
Solution Approach 2:
The patent divides the compressor fleet into multiple individual units that can be independently controlled. By segmenting the compression capacity across N compressors that can be selectively activated or deactivated, the system achieves flexible load matching to variable gas feed rates from renewable sources, optimizing the balance between productivity and energy consumption through selective operation of individual compressor units.
2Adaptability or versatility
If compressors are frequently shut down and restarted to match variable flow rates, then adaptability to renewable energy sources is improved, but reliability deteriorates due to increased wear on dry gas seals
Solution Approach 1:
The patent implements periodic sequential shutdowns of compressors based on sustained flow rate conditions rather than continuous operation or frequent on/off cycling. By establishing periodic action as a controlled strategy - shutting down compressors sequentially based on predetermined flow rate thresholds and maintaining them in low power mode during transition periods - the system achieves adaptability to variable renewable energy input while minimizing the harmful effects of frequent startup/shutdown wear on dry gas seals through planned, threshold-based operational transitions.
Solution Approach 2:
The patent applies preliminary action by transitioning compressors to low power mode before complete shutdown, and by pre-establishing shutdown sequences based on anticipated flow rate changes. This preliminary preparatory action allows the system to adapt to variable flow rates from renewable sources while reducing mechanical stress on dry gas seals by avoiding abrupt shutdowns and restarts, thereby maintaining reliability during the transition to and from operational changes.
3Reliability
If anti-surge controls are activated to prevent compressor surge, then reliability is improved, but stability of net compressed gas flow deteriorates due to disturbances in the flow
Solution Approach 1:
The patent applies preliminary action by maintaining compressor load above anti-surge control activation points through proactive load management. By ensuring compressors operate at sufficient load levels before surge conditions occur, and by using the main recycle system to prevent load drops that would trigger anti-surge controls, the system proactively prevents surge events while maintaining stable net compressed gas flow to downstream processes, thereby achieving both reliability and flow stability.
4Reliability
If the main recycle system is used excessively to maintain compressor load, then reliability is improved by preventing anti-surge activation, but energy consumption increases
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the operational parameters of individual compressors (full load, minimum load, low power mode, shutdown) based on real-time gas feed flow rates from renewable sources. By changing compressor operating parameters rather than relying excessively on recycle system flow adjustments, the system maintains compressor reliability through appropriate load management while minimizing energy waste associated with excessive recycling operations.
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 reduces electricity consumption, prolongs the lifetime of dry gas seals, and maintains stable output of net compressed gas, thereby improving compressor reliability and efficiency.
Implementation Method 1
Centrifugal compressors are a type of dynamic compressor, in which gas is compressed by mechanical action of rotating vanes or impellers which impart velocity to the gas. Gas typically enters at the center of the impellers and is propelled out to the radial edges under rotary motion to deliver gases at high velocity which impact the casing. The velocity of the gas is converted to a static pressure to deliver high pressure gases.
Implementation Method 2
These dry gas seals contain two opposed seal faces or rings which are separated during normal operation of the centrifugal compressor to compress gas.
Implementation Method 3
a main recycle system for recycling gas through the plurality (N) of centrifugal compressors
Implementation Method 4
dynamically adjusting the load of centrifugal compressors and minimizing recycling, by sequentially shutting down or putting compressors in low power mode, while maintaining the load above anti-surge control points using the main recycle system.
Data Source
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AI summary
Energy efficiency and/or operational stability of a multistage compression system (100, 200, 300) comprising a plurality (N) of centrifugal compressors (10, 12, 14, 50, 52, 54) that is compressing a gas feed having a variable flow rate is improved by adjusting reversibly the load on each compressor (10, 12, 14, 50, 52, 54) in response to changes in the flow rate of the gas feed using a main recycle system (32, 34) to enable operation of the centrifugal compressors (10, 12, 14, 50, 52, 54) at turndown capacity during periods when the flow rate is below total turndown capacity for all of the compressors (10, 12, 14, 50, 52, 54), and if necessary, using the local recycle systems (16, 18, 20, 22. 24, 26) in order to avoid activation of anti-surge control, and switching one or more centrifugal compressors (10, 12, 14, 50, 52, 54) into low power mode or shutdown mode as required.