Active solar distillation technology: A wide overview

Power generation from renewable resources has attracted increasing attention in recent years owing to the global implementation of clean energy policies. However, such power plants suffer from severe high-temperature corrosion of critical components such as water walls and superheater tubes. The corrosion is mainly triggered by aggressive gases like HCl, H2O, etc., often in combination with alkali and metal chlorides that are produced during fuel combustion. Employment of a dense defect-free adherent coating through thermal spray techniques is a promising approach to improving the performances of components as well as their lifetimes and, thus, significantly increasing the thermal/electrical efficiency of power plants. Notwithstanding the already widespread deployment of thermal spray coatings, a few intrinsic limitations, including the presence of pores and relatively weak intersplat bonding that lead to increased corrosion susceptibility, have restricted the benefits that can be derived from these coatings. Nonetheless, the field of thermal spraying has been continuously evolving, and concomitant advances have led to progressive improvements in coating quality; hence, a periodic critical assessment of our understanding of the efficacy of coatings in mitigating corrosion damage can be highly educative. The present paper seeks to comprehensively document the current state of the art, elaborating on the recent progress in thermal spray coatings for high-temperature corrosion applications, including the alloying effects, and the role of microstructural characteristics for understanding the behavior of corrosion-resistant coatings. In particular, this review comprises a substantive discussion on high-temperature corrosion mechanisms, novel coating compositions, and a succinct comparison of the corrosion-resistant coatings produced by diverse thermal spray techniques.

/pdf/advances-in-corrosion-resistant-thermal-spray-coatings-for-2a96fqpo3r.pdf

Advances in Corrosion-Resistant Thermal Spray Coatings for Renewable Energy Power Plants. Part I: Effect of Composition and Microstructure

The purpose of this article is to investigate the relationship among the material design, in situ synthesis, microstructure and mechanical properties of arc-sprayed Al-Ni-Ti amorphous coatings. The precursor reactants were designed by aluminium strip and low-purity industrial alloy powders. The results show that the Al-Ni-Ti coating displays a lamellar structure with porosity up to 1%. The volume fraction of the amorphous, crystallization temperature and hardness of the coatings are 85.9%, 365°C and 4.87 GPa, respectively. The microstructure analysis reveals that the grey region in the coating has a glassy structure and the white region has a crystalline structure of α-Al phase. In 0.6 M NaCl solution, compared with the crystalline structure of the arc-sprayed Al coating and 6061-Al alloy, the Al-Ni-Ti amorphous coating demonstrates an extraordinarily higher pitting potential (− 0.12 V) and lower corrosion current density (4.54 × 10−8 A/cm2). These investigations show that the present Al-Ni-Ti amorphous coating furnishes valuable guidance for expanding engineering applications with an inexpensive, high glass formation ability and prominent performance.

Development and Characterization of Al-Based Amorphous Coating

Gasification or combustion of coal and biomass is the most important form of power generation today. However, the use of coal/biomass at high temperatures has an inherent problem related to the ash generated. The formation of ash leads to a problematic phenomenon called slagging. Slagging is the accumulation of molten ash on the walls of the furnace, gasifier, or boiler and is detrimental as it reduces the heat transfer rate, and the combustion/gasification rate of unburnt carbon, causes mechanical failure, high-temperature corrosion and on occasions, superheater explosions. To improve the gasifier/combustor facility, it is very important to understand the key ash properties, slag characteristics, viscosity and critical viscosity temperature. This paper reviews the content, compositions, and melting characteristics of ashes in differently ranked coal and biomass, and discusses the formation mechanism, characteristics, and structure of slag. In particular, this paper focuses on low-rank coal and biomass that have been receiving increased attention recently. Besides, it reviews the available methodologies and formulae for slag viscosity measurement/prediction and summarizes the current limitations and potential applications. Moreover, it discusses the slagging behavior of different ranks of coal and biomass by examining the applicability of the current viscosity measurement methods to these fuels, and the viscosity prediction models and factors that affect the slag viscosity. This review shows that the existing viscosity models and slagging indices can only satisfactorily predict the viscosity and slagging propensity of high-rank coals but cannot predict the slagging propensity and slag viscosity of low-rank coal, and especially biomass ashes, even if they are limited to a particular composition only. Thus, there is a critical need for the development of an index, or a model or even a measurement method, which can predict/measure the slagging propensity and slag viscosity correctly for all low-rank coal and biomass ashes.

A critical review of ash slagging mechanisms and viscosity measurement for low-rank coal and bio-slags

The aim of the current investigation is to evaluate the erosion-corrosion (E-C) performance of wire arc sprayed Ni-20Cr and Ni-5Al coatings on T22 and SA516 boiler steels in a real boiler environme...

Erosion corrosion behaviour and mechanical properties of wire arc sprayed Ni-Cr and Ni-Al coating on boiler steels in a real boiler environment

In engineering applications, there are various types of boilers such as water tube boilers, fire tube boilers, packaged boiler, fluidized bed combustion boiler, pulverized fuel boiler and waste heat boilers. These boilers are used in different industries such as power plants, paper, and chemical. The present paper reports various problems (such as agglomeration, slagging, fouling, caustic embrittlement, fatigue failure and high temperature corrosion) related to boilers and their possible solutions. Some of the controlling parameters for high temperature corrosion has also been studied viz use of inhibitors, varying temperature and pressure, sol–gel coating and thermal spray coating. Thermal spraying has emerged as a main tool for improvement in surface. Problem of corrosion, wear resistance, electrical or thermal insulation can be altered using different coating techniques and materials. Deposition of ash in biomass-fired boilers also causes severe problems of agglomeration. The problem of agglomeration can be solved using kaolin or NH3 in the bed of boilers. Some important processes such as pulse detonation wave technology, intelligent soot blower, chemical treatment technology can be used to minimize the effects of fouling.

/pdf/an-overview-of-problems-and-solutions-for-components-1mhdu7wenv.pdf

An overview of problems and solutions for components subjected to fireside of boilers

The present work aims at improving the design of an energy conversion system operating on solar radiation harvesting and converting it into electricity with the help of thermopiles. Here, the major...

Parametric analysis of solar energy conversion system using parabolic concentrator and thermopile

Coatings can be defined as the application of one material on the other material usually known as substrate. They are mainly applied on the material to protect it from any degradation which occurs due to environmental conditions. They act as an interface between the substrate and the environment. Moreover, they are also used for decorative purposes. Nanocoatings are those coatings in which the size of a particle is in the range of 1–1000 nm at least in one dimension. Nanocoatings provide more wear resistance attributed to its higher toughness and hardness to the substrate as compared to other conventional coatings. They also provide antimicrobial, wrinkle resistance, stain resistance, hydrophobic and hydrophilic characteristics, UV protection and antistatic properties affecting the bulk properties of the substrate material. Nanocoatings can be manufactured by mainly two methods: vapour phase method and liquid phase method. Vapour phase method includes chemical vapour deposition, laser ablation, vapour condensation, plasma arc and flame synthesis processes. Liquid phase method includes sol–gel, precipitation, electrolysis, microemulsion and hydrothermal processes. Nanocoatings are used in aircraft (landing gears and engines), industrial rolls, hydraulic shafts, boiler tubes, turbines and pumps to prevent corrosion and erosion problems. They are also used on cars, pens, watches and cosmetics for decorative purposes. Nanocoatings are used on money bills so as to prevent forgery. This chapter discusses in detail about the nanocoatings. Efforts have also been made to summarize the various processing techniques for their fabrication. Effect of nanocoatings on structural, mechanical and corrosion behaviour is also discussed. It is expected that the present chapter will be useful in designing and developing nanocoatings for wide industrial applications.

Design, Development and Application of Nanocoatings

In this paper, a simple metamaterial based compact microstrip antenna is presented for UWB applications. A patch of dimension 36 ×36 mm is being selected. The resonant frequency of patch antenna is minimized by zero iteration is fixed to out from its patch radiating at its center respectively. And we will compare with second iteration positively. In this particular design, dimensions of the star length was varied & the antenna is being operated at 3.45GHz using the software HFSS. On the other hand for making star shape cut in ground give 0.3mm star shape antenna. Another ground is designed with 2mm gap to metamaterial. Dimension of ground is 20.6 × 31.6. The substrate material used in our work is FR4. The dimension of substrate is 45.4 × 31.6 × 1.6 mm. The ground part is divided into two parts. One part is completely grounded with copper metal. Another part is placed with metamaterial substrates. The dimension of ground part is 20.2 × 31.6 mm. The unit cell is has dimension of 3.6 mm square. There are rectangular cut of dimension 0.3 × 0.8 mm. These cutes are ported on each side of the square cell. The value of impedance bandwidth is from basically 3GHz to more than the 14 GHz. Maximum gain we noticed from fractal antenna is 15.8533db.

Design and simulation of metamaterials using star shape fractal antenna

Bituminous mixes are most commonly used for road pavements. With the increase in traffic volume, the bituminous road pavements are expected to give more strength. The bituminous pavements give satisfactory strength if designed properly. The use of waste polyethylene for road construction as a replacement of limited percentage of asphalt can increase the strength of the flexible pavement and it will also be beneficial for the environment. polyethylene has stronger binding properties than can be used in flexible pavement up to a limited percentage.

Akash Singh

Papers

An overview of problems and solutions for components subjected to fireside of boilers

Parametric analysis of solar energy conversion system using parabolic concentrator and thermopile

Design, Development and Application of Nanocoatings

Design and simulation of metamaterials using star shape fractal antenna

Plastic used in flexible pavements: Retrospects and prospects