Engineering thermal physics research of carbon dioxide solid absorbent has progressed

At present, carbon capture technologies based on coal utilization mainly include CO2 capture technology in pre-combustion gas, CO2 capture technology in post-combustion flue gas, and chemical-chain combustion or pure oxygen combustion technology. The pre-combustion CO2 capture technology is applied to coal gasification, coal-based CH4, coal-to-hydrogen, and other gas conversion processes to achieve not only CO2 emission reduction, but also to increase the content of CH4 or H2 in the gas by increasing CO2 absorption in the gas. Think of it as a potential carbon capture technology. The Energy and Power Research Center of the Institute of Engineering Thermophysics, Chinese Academy of Sciences combined with the IGCC gasification process to study the pre-combustion dry CO2 capture technology.

For the pre-combustion CO2 capture technology, the development of absorbents with good absorption performance and stable cycle performance is the key to research. Calcium oxide-based CO2 absorbers are favored by researchers because of their wide range of sources and high theoretical CO2 absorption capacity.

However, the main problems in the application process of calcium-based absorbents are: the temperature required for CaCO3 calcination regeneration during the cycle is as high as 900oC, which can easily cause high-temperature sintering of the absorbent, and the absorption performance gradually decreases during the cyclic absorption process. In response to this problem, the Center for Energy and Power Research mainly conducted research on the following two aspects: 1) Research on the improvement of the activity of calcium-based substances; 2) Study on magnesium-based double salt CO2 absorbents with lower absorption and regeneration temperatures.

In terms of improving the activity of calcium-based substances, the Energy and Power Research Center recently studied the effect of the introduction of the inert substance MgO on the cyclic absorption performance of CaO-based absorbents, and determined the range of MgO content. The researchers found that MgO can be 31.5% to 38.7%. Effectively improve the cycle stability of CaO-MgO absorbent obtained by calcining natural dolomite.

In conjunction with the water vapor conversion process, the researchers studied the effect of H2O vapors on the absorption properties of CaO-MgO absorbers in coal gas. The absorption capacity of the CaO-MgO absorbent when circulated 30 times under water vapor conditions can be increased by 50% compared to the anhydrous steam condition. Water vapor not only enhances the absorption capacity of the absorbent during the rapid chemical reaction control stage, but also accelerates the reaction rate of the absorbent during the diffusion reaction control stage. With the increase of MgO content, the promotion of water vapor is more obvious. The conclusions of the study provide a theoretical basis for the use of CaO-MgO absorbers in water vapor conversion processes.

In response to the high regeneration temperature of calcium-based absorbents, the Energy and Power Research Center collaborated with the US Department of Energy's National Energy Technology Laboratory (NETL) and the Pacific Northwest National Laboratory (PNNL) to develop new types of carbon dioxide absorbents the study.

The synthesized magnesium-based double salt absorbent not only has stable absorption performance during the cyclic absorption regeneration process, but also has a regeneration temperature (about 400° C.) far lower than the regeneration temperature of the calcium-based absorbent (about 900° C.) and does not cause high-temperature sintering of the absorbent. And the attenuation of absorption performance can also effectively reduce the regeneration energy consumption of the absorbent.

Based on the research conclusions of the cooperation projects, the Energy and Power Research Center further uses alkali metal nitrates to modify natural calcium magnesium ores to prepare carbon dioxide absorbers, and analyzes the modification mechanism of alkali metal nitrates from the perspective of ion diffusion. The above research lays the foundation for the research on the application of magnesium-based double-salt carbon dioxide absorbent in the gas shift process.

The above research work was supported by a joint research project on carbon dioxide capture and storage technology between China and the United States. Some of the research results have been published in the International Journal Energy & Fuels, Asia-Pacific Journal of Chemical Engineering.

LWN Flange

ASME B16.5 has endorsed the design of long welding neck flange (LWN), which is also known as straight hub welding flange. The LWN flange is constructed by two sections: the upper section is a heavy-wall barrel, whilst the lower section is a disc-like Plate Flange with all dimensions conforming to ASME B16.5 standard flanges.

Application
The long welding neck flange is mainly applied to the construction of pressure vessel functioning as a nozzle (such as a thermowell nozzle). To attach a common welding neck flange to a pressure vessel, a piece of pipe is required with additional welding. A LWN flange on the other hand attaches directly to the vessel, hence, it can be viewed as an integrally reinforced nozzle. It avoids making a weld seam at pipe to flange and provides self-reinforcement.

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