Low-Temperature Waste Heat Steam Generation with Pressure Compression
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Solution Overview
Problem
Existing systems for generating steam from internal combustion engines waste heat are inefficient, leading to excessive fuel consumption and emissions due to the utilization of low-temperature secondary heat rejection streams, which are typically wasted.
Innovation Solution
A system that recovers low-temperature waste heat from the secondary heat rejection circuit of internal combustion engines to generate low-pressure steam, which is then compressed using mechanical or thermal compression methods to achieve usable pressure levels, reducing the need for additional fuel consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If low-temperature waste heat from secondary heat rejection is utilized to generate steam, then fuel consumption is reduced, but the steam pressure and temperature are insufficient for direct use by heat consumers
Solution Approach 1:
The system segments the steam generation process into two distinct stages: first generating low-pressure steam from low-temperature waste heat, then compressing it to high-pressure steam for heat consumers. This segmentation allows each stage to operate optimally for its specific function, resolving the contradiction between fuel efficiency and steam quality.
Solution Approach 2:
The system changes the pressure parameter of the steam through compression while maintaining the thermal energy content. By increasing pressure through compression, the steam transitions from a low-quality state (insufficient for heat consumers) to a high-quality state (suitable for heat consumers), without requiring additional fuel input for temperature increase.
2Stress or pressure
If low-pressure steam is compressed to high pressure using mechanical or thermal compression, then steam pressure is improved, but additional energy input is required for compression
Solution Approach 1:
The system merges the compression function with the existing steam generation system by using the waste heat steam itself as the working fluid for compression. The low-pressure steam generated from waste heat is compressed to high pressure, and the system integrates this compression process into the overall waste heat utilization scheme, eliminating the need for separate high-pressure steam generation.
Solution Approach 2:
The system uses the waste heat steam to compress itself, effectively using the thermal energy already present in the low-pressure steam to drive the compression process. This self-service approach eliminates the need for external energy input for compression, as the system leverages its own waste heat resources to achieve the desired pressure increase.
3Productivity
If conventional steam generation systems are used to meet increased steam demand, then steam supply is improved, but fuel consumption and emissions increase
Solution Approach 1:
The system recovers waste heat that would otherwise be discarded to secondary heat rejection sources (engine cooling systems). By capturing and utilizing this previously wasted thermal energy for steam generation and compression, the system meets increased steam demand without requiring additional fuel combustion, thereby reducing emissions.
Solution Approach 2:
The system makes the waste heat recovery system multi-functional by using the same waste heat steam for both generation purposes and compression purposes. This universal approach allows a single system to address multiple needs (steam supply and pressure increase) without requiring separate systems, thereby avoiding additional fuel consumption and emissions.
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 system effectively generates high-pressure steam with reduced fuel consumption by utilizing waste heat, thereby decreasing overall fuel usage and emissions compared to conventional methods.
Implementation Method 1
a waste heat recovery boiler (25) is used to cool down the exhaust gas stream (5) while generating high-pressure steam (28) by heating up, evaporating and superheating high pressure condensate (32)
Implementation Method 2
a low-pressure boiler (15) is used to generate low-pressure steam (17) by heating up and evaporating low-pressure condensate (16) with the hot engine cooling fluid (7)
Implementation Method 3
an expander (36) which extracts thermal energy from the high-pressure steam (28) by expansion of it and uses it to do mechanical work
Implementation Method 4
a compressor (38) which increases the pressure and consequently the thermal energy of the low-pressure steam (17) by reducing its volume
Data Source
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AI summary
The invention relates to a system of generating steam at usable pressure level, in particular by compressing the low-pressure steam which is generated by recovering the low temperature waste heat rejected from an internal combustion engine, whereas the motive steam at high pressure required to compress the low- pressure steam is generated by the recovery of the high temperature exhaust waste heat of the same internal combustion engine. The amount of low temperature reject heat from the internal combustion engine is of significance when compared with total heat input to the internal combustion engine, and comparable to the high temperature exhaust waste heat. With the proposed system, utilization of the low temperature waste heat and generating steam at usable pressure level decreases the total fuel consumption when compared with generating the same amount of steam with conventional systems consuming fuel.