Natural Gas Power and LNG Plant With Onsite CO2 Sequestration
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Solution Overview
Problem
Natural gas power plants emit greenhouse gases, primarily carbon dioxide, contributing to global warming, and existing solutions do not effectively capture and sequester these emissions close to the power generation sites, leading to high transportation costs and inefficiencies.
Innovation Solution
The implementation of a natural gas power plant system that utilizes turbo-expanders, solid oxide fuel cells (SOFCs), and heat exchangers to generate electricity and hydrogen while sequestering carbon dioxide by compressing and injecting it back into geological formations near the gas fields, minimizing emissions and transportation costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If carbon dioxide is captured and transported to distant sequestration sites, then greenhouse gas emissions are reduced, but transportation costs and energy consumption increase significantly
Solution Approach 1:
The system segments the carbon dioxide stream from the natural gas flow using a separator, allowing independent handling of CO2. This enables CO2 to be compressed and injected into nearby geological formations without requiring long-distance transportation, thus reducing transportation energy while still achieving emission reduction
Solution Approach 2:
The patent introduces an intermediary compression system that processes CO2 locally at the power plant site. This intermediary device (compressor) enables CO2 to be transported short distances to nearby sequestration sites, avoiding the need for long-distance pipelines and reducing overall transportation energy requirements
2Quantity of substance
If natural gas is processed through heat exchangers to produce LNG, then liquid natural gas product is obtained, but system complexity and equipment requirements increase
Solution Approach 1:
The heat exchanger system performs multiple functions: it cools natural gas to produce LNG, preheats the combustion air for the power generation cycle, and recovers heat from exhaust gases. This multi-functionality reduces the need for separate heating equipment, thereby offsetting the complexity added by the heat exchanger system
Solution Approach 2:
The system utilizes phase transition of natural gas from gaseous to liquid state through controlled cooling in the heat exchanger. This phase change enables compact storage and transport of LNG while the recovered cold energy is used to preheat combustion air, improving overall system efficiency and justifying the equipment complexity
3Object-generated harmful factors
If turbo-expanders are used to compress carbon dioxide for sequestration, then CO2 compression is achieved, but the system requires additional equipment and increases complexity
Solution Approach 1:
The patent merges the CO2 compression function with the existing power generation infrastructure by using the turbo-expander that is already part of the natural gas processing system. The turbo-expander serves dual purposes: generating power from the pressure drop of natural gas and compressing CO2 for sequestration, thereby reducing the need for separate compression equipment
Solution Approach 2:
The system uses its own internal resources to achieve CO2 compression. The turbo-expander, which processes the natural gas flow anyway, is utilized to provide the compression work for CO2. This self-service approach eliminates the need for external power sources or separate compression systems, offsetting the added complexity
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 system achieves zero atmospheric emissions of greenhouse gases, efficiently processes natural gas with varying carbon dioxide content, and produces pure liquid natural gas (LNG) and potable water as by-products, enhancing energy efficiency and reducing environmental impact.
Implementation Method 1
the natural gas received from the wells in the gas field is at an elevated pressure and temperature and is subjected to one or more heat exchangers in order to reduce the temperature sufficiently so that a stream of liquid natural gas (LNG) may be obtained
Implementation Method 2
reduce the temperature sufficiently so that a stream of liquid natural gas (LNG) may be obtained
Implementation Method 3
the non-LNG stream may be expanded through one or more turbo-expanders as described above which have shafts which share or are mechanically coupled to the shafts or one or more compressors. Thus, the energy given up by the natural gas in the turbo-expanders is used to run compressors which compress carbon dioxide
Implementation Method 4
some of the natural gas is reheated in the heat exchangers and then utilized in conjunction with one or both of the other embodiments. Thus, the non-LNG stream of natural gas may be eventually forwarded to a solid oxide fuel cell (SOFC) and used to generate electricity
Data Source
AI summary
A zero-emissions power plant receives natural gas from wells at elevated pressure and temperature. Gas is expanded through one or more turbo-expanders, preferably reformed, and sent to a fuel cell where electricity, heat, carbon-dioxide, and water are generated. The carbon-dioxide is compressed by at least one compressor and piped downhole for sequestration. The turbo-expanders have shafts which preferably share the shafts of the compressors. Thus, energy given up by the natural gas in the turbo-expanders is used to run compressors which compress carbon dioxide for downhole sequestration. In one embodiment, the natural gas is applied to heat exchangers in order to generate a stream of liquid natural gas. The remainder of the gas is expanded through the turbo-expanders and processed in the reformer prior to being sent to the fuel cell. A shifter may be used between the reformer and fuel cell. A solid oxide fuel cell is preferred.