Efficient waste heat recovery in a cryogenic distillation air separation plant using heat pumps
The separation of the air in its components by cryogenic distillation has a high electric consumption due to the required air compression process. This work analyses the energy recovery of the heat dissipated at the intercooling stages of the main compressor by the integration of two types of heat pumps: an Absorption Heat Transformer (AHT) and a Vapour Compression Heat Pump (VCHP). The upgraded heat from the compressor is used in the regeneration of a Molecular Sieve used to eliminate some undesirable components before the distillation process. Real operation data from an air separation plant in Tarragona (Spain) is used to compare the two configurations using both types of heat pumps. The results show that the present consumption of thermal energy for the regeneration of the Molecular Sieve could be reduced up to 50%, when an AHT is coupled in series with the existing heating system and using first the waste heat at the desorber of the AHT and later at the evaporator of the AHT system with a Tcon=20°C. For the second configuration, the basic VCHP with a Teva=55°C and Tcon=120°C could reduce the thermal energy consumption almost up to 72% with a reduction of about 14% in the heat rejected to the ambient with respect to the current situation but with an additional expense in mechanical work for the heat pump of about 4%.
Industrial Gas Handbook: Gas Separation and Purification
“The molecular chemistry of gases is well known and it seems nlikely that any new discoveries will cause Lavoisier, the father of odern chemistry, to turn in his grave. On the other hand, there are lways new applications to discover, or to develop some of which ill require phenomenal quantities of well known industrial gases.” o ends this book, written by a mechanical engineer based on his ifetime experience of 60 years—and I might add, well written. The book has 14 chapters covering virtually every aspect of the opic offering “. . . detailed discussions and up-to-date approaches o process cycles for cryogenic separation of air, adsorption proesses for front-end air purification, and related process control nstrumentation.” In addition, the book “. . . covers topics such as hronological development, industrial applications, air separation echnologies, noble gases, front end purification systems, insulaion, non-cryogenic separation, safety, cleaning for oxygen systems, conomics, and product liquefaction, storage and transportation.” One feature I appreciated was a historical review (at approriate points) of discoveries and developments of gases and their ses. This historical review starts with a discussion of the Eigheenth Century work of French physicist Guillaume Amontons in hermometry and mathematics which led to the supposition of bsolute zero. This discussion of the historical background of the opic being reviewed provides the reader with some understanding f the development of the field. The book has the following 14 chapters:
Techno-economic analysis of chemical looping combustion with humid air turbine power cycle
Abstract Power generation from fossil fuel-fired power plant is the largest single source of CO2 emission. CO2 emission contributes to climate change. On the other hand, renewable energy is hindered by complex constraints in dealing with large scale application and high price. Power generation from fossil fuels with CO2 capture is therefore necessary to meet the increasing energy demand, and reduce the emission of CO2. This paper presents a process simulation and economic analysis of the chemical looping combustion (CLC) integrated with humid air turbine (HAT) cycle for natural gas-fired power plant with CO2 capture. The study shows that the CLC–HAT including CO2 capture has a thermal efficiency of 57% at oxidizing temperature of 1200 °C and reducer inlet temperature of 530 °C. The economic evaluation shows that the 50 MWth plant with a projected lifetime of 30 years will have a payback period of 7 years and 6 years for conventional HAT and CLC–HAT cycles respectively. The analysis indicates that CLC–HAT process has a high potential to be commercialised.