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%.
Evaluation of an energy supply system with air separation
A high performance energy supply system (HiPESS) by use of liquefied natural gas (LNG) is proposed, which is one of the promising electric energy supply systems to accomplish less pollutant emissions in the exhaust. By using methane as the fuel and high purity oxygen as the oxidizer, neither NOx nor SOx are ideally generated. In addition, to control the combustion temperature, carbon dioxide is recycled from the flue gas as the dilution gas. As the exhausted gas consists of only carbon dioxide and water, it is easy to separate, isolate, and treat carbon dioxide. To produce high purity oxygen economically, a cryogenic air separation system is applied by introducing the cold energy of LNG and modifying the conventional process. The electric power consumption is potentially reduced by 66%, compared with the conventional system. By installing the air separation system, the efficiency of HiPESS is also lowered by around 10% (if compared with a conventional power plant). However, this is not necessarily negative because HiPESS will make a great contribution towards preservation of the global environment.
Analysis of Macro and Micronutrients in Soils from Palestine Using Ion Exchange Membrane Technology
Ion Exchange membrane technology (IEM) is a method that allowed a single extraction process and a single subsequent measurement of different elements that are available in soil. The values of the available forms of the different macro- and micronutrients obtained by IEM extraction were compared with the values of the soluble form obtained by conventional extraction methods. In surface soil sample, the concentrations of available potassium, nitrate, phosphate, iron and boron were 37.7 mg kg–1, 17.5 mg kg–1, 3.6 mg kg–1, 171.0 μg kg–1, and 4.2 μg kg–1 respectively were greater than that of soluble forms of the same elements which were 7.0 mg kg–1, 9.2 mg kg–1, 0.4 mg kg–1, 109.0 μg kg–1, and 1.9 μg kg–1 respectively.