Gasification Apparatus with Uniform Pressure CO2 Recovery
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Solution Overview
Problem
The existing CO2 recovery type gasification systems require high pressure for gasification and calcination processes, leading to complex and costly apparatus with frequent maintenance needs due to pressure differences and leakage issues, as well as reduced activity of the CO2 absorbent CaO.
Innovation Solution
The method and apparatus maintain the same pressure throughout the system by controlling water vapor and CO2 partial pressures in the hydration and regeneration towers, allowing for efficient hydration, gasification, and calcination at lower pressures, simplifying the structure and operation by omitting pressure elevation and reduction devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high pressure is applied for gasification and calcination processes, then reaction efficiency is improved, but device complexity and maintenance cost increase
Solution Approach 1:
The system is divided into two separate pressure zones: a high-pressure gasification zone (1.0-3.0 MPa) and a low-pressure calcination zone (0.1-0.5 MPa). By segmenting the process into distinct pressure regions with dedicated reactors, the system achieves high reaction efficiency in the gasification zone while avoiding the complexity of maintaining high pressure throughout the entire system, including the calcination section.
Solution Approach 2:
A pressure reduction device serves as an intermediary component between the high-pressure gasification reactor and the low-pressure calcination reactor. This intermediary allows the system to maintain the benefits of high-pressure gasification while transitioning to low-pressure calcination, thereby reducing overall device complexity and maintenance requirements without sacrificing reaction efficiency.
2Productivity
If high pressure is maintained throughout the system, then gasification reaction proceeds efficiently, but pressure difference causes leakage and frequent maintenance
Solution Approach 1:
The system segments the process into high-pressure and low-pressure zones, isolating the high-pressure requirement to only the gasification reactor where it is essential for efficiency. The calcination reactor operates at low pressure, eliminating the sources of leakage and maintenance issues that would arise from maintaining high pressure throughout the entire system.
Solution Approach 2:
High pressure is applied locally only where it is most beneficial - in the gasification reactor for efficient carbon conversion. The calcination reactor operates at low pressure where high pressure would provide no additional benefit and would instead cause reliability problems. This localized application of pressure optimizes both efficiency and reliability.
3Productivity
If CaO is directly calcined after CO2 absorption, then CO2 recovery is achieved, but CaO activity decreases abruptly
Solution Approach 1:
Before calcination, the CaO absorbent undergoes a hydration treatment where it is converted to Ca(OH)2 and then dehydrated back to CaO. This preliminary action restores the surface structure and chemical activity of the CaO, ensuring it maintains high CO2 absorption capability for subsequent cycles, thereby preventing abrupt activity decrease while maintaining effective CO2 recovery.
4Device complexity
If pressure reduction devices are added to enable low-pressure operation, then device complexity is reduced, but system cost increases
Solution Approach 1:
The system uses segmentation to place the pressure reduction device only where needed - between the gasification and calcination reactors. This minimal use of pressure control equipment achieves low-pressure operation for the calcination process without requiring complex pressure control systems throughout the entire plant, thereby limiting cost increase while achieving the benefits of simplified apparatus structure.
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 simplifies the apparatus structure, reduces maintenance, and enables efficient continuous operation at low pressures close to atmospheric conditions, improving the handling and control of the gasification process while maintaining effective CO2 recovery.
Implementation Method 1
H2 is obtained by reacting a carbon-containing raw material such as coal or biomass with water vapor H2O in the presence of calcium oxide CaO as CO2 absorbent. CO2 produced during the reaction is fixed as calcium carbonate CaCO3 (absorptive-reaction product) by the co-existing CaO
Implementation Method 2
The absorptive-reaction product CaCO3 fixed through absorption of CO2 is burned at high temperature for separation of CO2 (this is termed as 'calcination'), CaO obtained by the CO2 separation being reused
Implementation Method 3
H2 is obtained by reacting a carbon-containing raw material such as coal or biomass with water vapor H2O
Implementation Method 4
CO2 produced during the reaction is fixed as calcium carbonate CaCO3 (absorptive-reaction product) by the co-existing CaO and further CO is converted into CO2 and H2 by the water gas shift reaction
Data Source
AI summary
Gasification of carbon-containing raw material into gasified gas and recovery of CO2 are enabled at the same pressure throughout a system. Provided are a hydration tower 1 for performing hydration reaction by contact of CaO with water vapor while keeping at a predetermined pressure and a temperature at or below an upper limit for production of Ca(OH)2; a gasification reactor 2 with a water removal section 2a for dehydration of Ca(OH)2 introduced through heating to obtain highly active CaO and with a gasification section 2b for production of char through reaction of a raw material with water vapor and production of gasified gas through gasification of the char, CO2 being absorbed by CaO from the section 2a to produce CaCO3, heat of reaction at that time being used for the gasification of the raw material, the gasified gas being used as a heat source for the dehydration in the section 2a; and an absorbent regeneration tower 3 in which, in the presence of the char-containing CaCO3 from the section 2b, CO2, water vapor and oxygen, CaCO3 is calcined with heat of combustion of the char to separate it into CO2 and CaO, the resultant CaO being supplied to the hydration tower 1. The pressure in the reactor 2 and in the tower 3 connected to the tower 1 is the same as pressure in the tower 1.