Low-temperature Stream Research Articles

Tin and lanthanum modified Ni/CeO2 catalyst systems for low temperature steam reforming of ethanol

This work examines the Ni–Sn/Ce–La–O catalyst systems for low-temperature stream reforming of ethanol. Catalysts of 5 and 20 wt% metal loading, and different Ce:La ratios are prepared by ultra-sonication assisted solution combustion synthesis method. Catalysts at total metal loading 5 wt% with 33 and 67 at. % La and optimum Sn (Ni:Sn = 14:1) demonstrate better efficiency compared to the Ni/CeO2 catalysts. At 20 wt% metal loading and Ni:Sn = 1:1 atomic ratio, catalytic activity degrades. The best activity and stability are revealed for the N14S1(5)/CL21 catalyst with 5 wt.% total metal loading, Ni:Sn = 14:1, and Ce:La = 2:1 mol ratio. Physico-chemical characterizations (XRD, H2 -TPR, NH3-TPD, Raman, FESEM, TEM, XPS, N2 adsorption-desorption, DTA/TGA, etc.) are performed to understand the role of the metal loading, Sn, and La in the catalytic activity and coke deposition behavior.

A strategic sampling design revealed the local genetic structure of cold-water fluvial sculpin: a focus on groundwater-dependent water temperature heterogeneity.

A key piece of information for ecosystem management is the relationship between the environment and population genetic structure. However, it is difficult to clearly quantify the effects of environmental factors on genetic differentiation because of spatial autocorrelation and analytical problems. In this study, we focused on stream ecosystems and the environmental heterogeneity caused by groundwater and constructed a sampling design in which geographic distance and environmental differences are not correlated. Using multiplexed ISSR genotyping by sequencing (MIG-seq) method, a fine-scale population genetics study was conducted in fluvial sculpin Cottus nozawae, for which summer water temperature is the determinant factor in distribution and survival. There was a clear genetic structure in the watershed. Although a significant isolation-by-distance pattern was detected in the watershed, there was no association between genetic differentiation and water temperature. Instead, asymmetric gene flow from relatively low-temperature streams to high-temperature streams was detected, indicating the importance of low-temperature streams and continuous habitats. The groundwater-focused sampling strategy yielded insightful results for conservation.

Mainstream-sidestream wastewater switching promotes anammox nitrogen removal rate in organic-rich, low-temperature streams

ABSTRACT The main issues with mainstream anammox application are loss of bacterial activity by low temperatures and by a high organic content of wastewater. We demonstrate a novel switching method between sidestream and mainstream wastewater. The wastewater flow was switched between sidestream (reject water at >22°C) and mainstream (municipal wastewater at 16.5°C), so that the anammox biomass activity and biomass growth could benefit from sidestream conditions. Real sidestream wastewater (biogas plant effluent) (≈1000 mg NH+ 4-N L−1) and synthetic mainstream (municipal wastewater-like source) (≈100 mg NH+ 4-N) wastewater were used for 20 L biofilm reactor feeding. The highest total nitrogen removal rate (TNRR) of 527 g N m−3 d−1 (average TNRR 180 (±140) g N m−3 d−1) was achieved with sidestream wastewater at a low chemical oxygen demand (COD)/TN ratio of 1.1/1. For reactor feeding with mainstream, the highest TNRR achieved was 61 g N m−3 d−1. Average TNRR for mainstream of 20 (±15) g N m−3 d−1 was low due to a higher COD/N ratio of 3.2/1. The highest TNRR in a batch test was achieved at the COD concentration of 480 mg L−1, reflecting a TNRR of ≈5 mg N g−1 TSS h−1. With a high COD concentration of 2600 mg L−1 (TOC/TN = 8/1), TNRR decreased similarly in both feeds to 1.6 mg N g−1 TSS h−1. The anammox microorganism's genus Candidatus Brocadia enrichment in deammonification biofilm reactor was higher in the mainstream operation (7.6% of all bacteria) than in sidestream operation period (<0.7% of all bacteria).

Experimental investigation on a novel pressure-driven heating system with Ranque–Hilsch vortex tube and ejector for pipeline natural gas pressure regulating process

In this work, a novel pressure-driven heating system with a Ranque–Hilsch vortex tube and ejector to recover pressure losses and absorb energy from the ambient environment to heat pipeline natural gas (PNG) is proposed to take the place of the conventional heating system with a boiler. A vortex tube to produce the high-temperature and low-temperature streams simultaneously with its energy separation effect and an ejector to drive the internal subcycle within the system to heat the low-temperature stream by the ambient air are installed. They regulate the PNG pressure and absorb heat from the ambient air while maintaining simplicity and reliability. To study the performance of this new system, an analogical experimental rig was established with pressurised air as the working fluid. The experimental results verified the heating capacity of the system, in which a significant temperature rise greater than 9 K was obtained with a small pressure drop of approximately 1.0 MPa. Compared with a sole throttling valve, an energy-saving ratio of no less than 0.35 was achieved.

Experimental study on air-stream gasification of biomass micron fuel (BMF) in a cyclone gasifier

Based on biomass micron fuel (BMF) with particle size of less than 250μm, a cyclone gasifier concept has been considered in our laboratory for biomass gasification. The concept combines and integrates partial oxidation, fast pyrolysis, gasification, and tar cracking, as well as a shift reaction, with the purpose of producing a high quality of gas. In this paper, experiments of BMF air-stream gasification were carried out by the gasifier, with energy for BMF gasification produced by partial combustion of BMF within the gasifier using a hypostoichiometric amount of air. The effects of ER (0.22–0.37) and S/B (0.15–0.59) and biomass particle size on the performances of BMF gasification and the gasification temperature were studied. Under the experimental conditions, the temperature, gas yields, LHV of the gas fuel, carbon conversion efficiency, stream decomposition and gasification efficiency varied in the range of 586–845°C, 1.42–2.21Nm3/kg biomass, 3806–4921kJ/m3, 54.44%–85.45%, 37.98%–70.72%, and 36.35%–56.55%, respectively. The experimental results showed that the gasification performance was best with ER being 3.7 and S/B being 0.31 and smaller particle, as well as H2-content. And the BMF gasification by air and low temperature stream in the cyclone gasifier with the energy self-sufficiency is reliable.

Seawater distillation from low-temperature streams: a case history

The paper describes the objectives and the operational results of an experimental project aimed for the exploitation of very low temperature differences (associated with many waste streams commonly available in industrial environments) for the distillation of seawater. The case described is relevant to the engineering, construction and operation of a seawater desalination plant, called LTF, able to utilize as prime energy source the cooling seawater discharged by a turbine condenser, at only 8°C above ambient seawater temperature. The project was developed in the early 1990s by the Italian company Sowit, with a grant from the European Community. The desalination plant is presently in operation at the Piombino power station (owned by ENEL, the Italian Electricity Board) for the production of high-purity distillate for boiler make-up. Plant operational results confirmed the feasibility and the technical-economical convenience of this process. From the design point of view, the most critical aspect is related to the vent system of non-condensible gases released in the evaporator, while plant operation showed various advantages, such as a good reliability, a very high purity of produced distillate, reduced environmental impact and a competitive operation cost.