Heat to Hydrogen by RED—Reviewing Membranes and Salts for the RED Heat Engine Concept

The Reverse electrodialysis heat engine (REDHE) combines a reverse electrodialysis stack for power generation with a thermal regeneration unit to restore the concentration difference of the salt solutions. Current approaches for converting low-temperature waste heat to electricity with REDHE have not yielded conversion efficiencies and profits that would allow for the industrialization of the technology. This review explores the concept of Heat-to-Hydrogen with REDHEs and maps crucial developments toward industrialization. We discuss current advances in membrane development that are vital for the breakthrough of the RED Heat Engine. In addition, the choice of salt is a crucial factor that has not received enough attention in the field. Based on ion properties relevant for both the transport through IEMs and the feasibility for regeneration, we pinpoint the most promising salts for use in REDHE, which we find to be KNO3, LiNO3, LiBr and LiCl. To further validate these results and compare the system performance with different salts, there is a demand for a comprehensive thermodynamic model of the REDHE that considers all its units. Guided by such a model, experimental studies can be designed to utilize the most favorable process conditions (e.g., salt solutions).

Recovery of Spent Sulphuric Acid by Diffusion Dialysis Using a Spiral Wound Module

In this study, we assess the effects of volumetric flow and feed temperature on the performance of a spiral-wound module for the recovery of free acid using diffusion dialysis. Performance was evaluated using a set of equations based on mass balance under steady-state conditions that describe the free acid yield, rejection factors of metal ions and stream purity, along with chemical analysis of the outlet streams. The results indicated that an increase in the volumetric flow rate of water increased free acid yield from 88% to 93%, but decreased Cu2+ and Fe2+ ion rejection from 95% to 90% and 91% to 86%, respectively. Increasing feed temperature up to 40 °C resulted in an increase in acid flux of 9%, and a reduction in Cu2+ and Fe2+ ion rejection by 2–3%. Following diffusion dialysis, the only evidence of membrane degradation was a slight drop in permselectivity and an increase in diffusion acid and salt permeability. Results obtained from the laboratory tests used in a basic economic study showed that the payback time of the membrane-based regeneration unit is approximately one year.

Study on Emission Factors of FCC Flue Gas Pollutants in Petroleum Refineries

Fluid Catalytic cracking (FCC) unit is one of the means to lighten heavy oil in refineries, and its regenerated flue gas is also the main source of air pollutants from refinery. However, it is not clear about the type and amount of pollutants discharged from FCC units. The emissions of regenerated pollutants in the stack flue gases of three typical FCC units in China were investigated in this study, including a partial regeneration unit without a CO boiler (U1), a partial regeneration unit with a CO boiler (U2) and a full regeneration unit (U3). Different monitoring methods were used to analyze the concentration of sulfur dioxide (SO2) and nitrogen oxides (NOx), and the results showed that Fourier Transform Infrared Spectroscopy (FTIR) monitoring results of SO2 and NOx are approximately 10 times and 5 times larger than that of the Continuous Emission Monitoring System (CEMS) data, respectively. Also, the contents of characteristic pollutants such as NH3, C6H6, HCN, C8H8, C2H4, CH4 and CO were also monitored by FTIR, and the emission factors based on coke burn-off rate and throughput were investigated. The pollutants in U1 exhibited relatively higher contents with the NH3, HCN and C6H6 of 116.99, 71.94 and 56.41 mg/Nm3 in flue gas, respectively. The emission of regenerated pollutants in U2 and U3 are significantly different from U1. Regeneration processes (including coke properties, operating modes and presence or absence of CO boilers) affected pollutants emission factors in varying degree. At last, reasonable emission factors based on the different FCC regeneration processes contributes to the prediction, assessment and control for the pollutants emission.

Retrofitting recycled stripping gas in a glycol dehydration regeneration unit

Natural gas dehydration is essential in gas processing to avoid serious problems. As a pretreatment in a cryogenic Natural Gas Liquid (NGL) recovery process, it typically uses triethylene glycol (TEG) and followed by a Molecular Sieve dehydration to achieve 1 mg/Sm3 of water moisture in the dehydrated gas. This work studied the retrofitting of the existing dehydration unit to improve its performance in satisfying the gas moisture qualities. The retrofitted process uses recycled stripping gas schemes to achieve high purity TEG while minimizing the use of fresh stripping gas. The results revealed that the recycled stripping gas has provided sufficiently high purity TEG (>99.99%-wt), significantly reduced the heating and cooling duty by 80%, and reduced the electrical duty by 29% compared to the base case. The TAC was reduced by 38.1% from $ 725,245/year to $ 448,670/year. Through this study, the evaluated cases provide similar dehydration results with less equipment, simpler process, more energy-efficient, and better economic numbers. Therefore, a better process was obtained.

Toward the Biophilic Residential Regeneration for the Green New Deal

As climate changes and species extinction accelerate, the global community focuses on Green New Deal plans to promote economic development based on environmental sustainability. The Green New Deal should encourage sustainable resilience in the environment and strengthen the community’s innate ties with natural resources and biodiversity. This study describes biophilic design for sustainable and resilient residential regeneration from the perspective of the Green New Deal, and suggests potential possibilities for these approaches on a residential regeneration scale. A case study clarifies the applicable features of biophilic design in various fields, such as architectural planning and design, technology, and services, and is subdivided according to the scale of residential regeneration (unit, building, and complex). The results of this study suggest new values for existing Green New Deal policies and contribute to the segmentation of residential regeneration projects and the expansion of related industries.

FORMATION OF AZEOTROPIC MIXTURES OF N-METHYLPYRROLIDONE WITH HYDROCARBONS

Using the limiting activity coefficients of the components of binary systems of N-methylpyrrolidone with n-alkanes and the conditions for the formation of azeotropes, it is found that N-methylpyrrolidone forms azeotropic mixtures with n-alkanes С9 - С 15, with alkylbenzenes С 10 - С 12 and with naphthalene. The formation of azeotropes with saturated hydrocarbons with a boiling point of 230-270 ° C must be taken into account when developing a technological scheme for the N-methylpyrrolidone regeneration unit, and also not to use this extractant for extraction purification of raw materials with a boiling point below 230 ° C