Energy efficiency analysis of air dehumidification methods that determine safe microclimatic working conditions

Introduction. The article deals with the issues related to provision of air humidity parameters required for non-hazardous operation of various technical facilities. Problem Statement. The paper considers analytical methods for energy efficiency assessment of adsorption and condensation methods of air dehumidification, which provide safe microclimatic working conditions, and the influence of the operating modes of dehumidifying plants on the parameters of the microclimate. Theoretical Part. As indicators of the energy efficiency of each of the methods, it is proposed to use the energy costs that are minimally necessary for the implementation of ideal physical dehumidification processes and per unit mass of water units emitted from air. This ensures safe and comfortable microclimatic working conditions with minimal energy costs. The ratio of the specific energy costs of the condensation and adsorption methods shows their comparative efficiency. An electronic Id-diagram was used to determine the air parameters in the implemented dehumidification processes (cooling, condensation and adsorption of water vapor). Conclusion. Analytical dependences are obtained for the analyzed energy efficiency indicators that provide safe and comfortable microclimatic working conditions with minimal energy costs. Numerical estimates were carried out according to the most probable modes of dehumidification processes and air parameters. The parametric restrictions on the implementation of the adsorption dehumidification method are justified, in which it becomes energetically more profitable. The conditions under which it is possible to implement a combined dehumidification method to ensure safe microclimatic working conditions are determined.

Research of physical and chemical processes associated with corrosion of cements (“Caking”) in dampy wet air

Objective. The paper is aimed at clarifying the mechanism and kinetics of the processes leading to cement caking. Methods. To determine phase composition, the following modern physical and chemical methods were used: XRF, derivatography and electron microscopy. Results. The data obtained show that the “aging” of cements during their forced storage in humid air through the adsorption of water vapor, and then CO2, is associated with the processes of hydrolysis, hydration in surface layers of particles, is primarily relevant for the most reactive minerals of Portland cement clinker. The deepening of these processes also depends on the state of the corroded surface of minerals. Conclusion. The work carried out makes it is possible to preliminarily outline storage conditions for freshly ground Portland cements (according to the kinetics of sorption – the storage duration, according to isotherms – the permissible relative humidity), at which the LOI value of commercial cement remains stable for the required minimum time.

Рhysical and chemical analyses of the adsorption capacity of transcarpathian clinoptilolite

The IR spectroscopy and complex thermal analysis were used to analyze the adsorption capacity of Transcarpathian clinoptilolite, both naturally occurring and activated, relative to water vapor. It was found that activation of clinoptilolite with an H2SO4 25 %-solution causes dealumination and the appearance of additional adsorption centers, allowing maximum adsorption of water vapor. Activation with a 5 % solution of HCl at the 1:10 solid-liquid ratio ensures the significant dealumination of the mineral with no breakdown of its structure and the occurrence of transient pores and macropores in this mineral. Due to such activation clinoptilolite is far more able to absorb molecules of the green dye.

Adsorption Properties of Combined Vegetable Powders

Equilibrium moisture of combined vegetable powders obtained from vegetable raw materials is one of the main technological properties and it is important. Because the final moisture content and energy costs for the dehydration process depend on this indicator. To determine the equilibrium humidity of the samples of combined powders, depending on the relative humidity, the tensometric (static) method of Van Bamelen was used. As a result of researches, kinetic curves of adsorption of water vapor of mono- and combined vegetable powders, which were compared among themselves, were received. Comparison of adsorption isotherms, despite the same nature of these isotherms, show that these materials are capillary-porous colloidal bodies and have the same forms of moisture binding (adsorption, capillary and osmotic) and at the same time differ significantly from each other by equilibrium humidity. When storing composite powders in order to preserve their technological properties, it is recommended to maintain the following conditions in the room: humidity not more than 60 % at the temperature of 20 - 25 ºC and to pack hermetically.

Pickett Equation for the Description of Adsorption on Arbitrary Surfaces

The theory of multilayer adsorption of gases, namely the Pickett equation, has been developed to the case of adsorption on arbitrary surfaces in a molecular and a topological approach. We present the prediction of the fractal dimension for the surface of an adsorbent and for the set of interfaces generated by the growing of layers. The theoretical models correctly predict quantities and qualitative features of the experiment for two systems: adsorption of water vapor (T = 298 K) on the sample of lunar regolith and of nitrogen (T = 77 K) on a coal sample.

MOFs containing a linear bis-pyridyl-tris-amide and angular carboxylates: exploration of proton conductivity, water vapor and dye sorptions

Four new MOFs were shown to have appreciable proton conductivities, selective adsorption of water vapor over nitrogen and a tendency to selectively adsorb cationic dyes such as methylene blue and crystal violet.

EFEKTIFITAS JENIS DESIKAN DAN KECEPATAN UDARA TERHADAP PENYERAPAN UAP AIR DI UDARA

Dry air is widely used in many fields, but the excessive water vapor in the air will make some problem and should be minimized to get the required dry air. The purpose of this research to observe the effect of air velocity and various of desiccants on the absorption of water vapor in the air on the tray dryer. The process of absorption of water vapor in the air performed with variations of the normal air velocity, 1.2 m/s, 2.3 m/s, and 3.6 m/s or volumetric rate of 0.059 m3/s; 0.113 m3/s; 0.178 m3/s and the type of desiccant of silica gel, alumina, and zeolite. Adsorption of water vapor in the air by desiccant was done by weighing the mass of desiccant before and after being crossed by air every interval of 60 minutes for 3 hours. Humidity measurement are performed on the upstream and downstream of the tray dryer to obtain a decrease in air humidity. The highest moisture adsorption using silica gel was obtained at velocities of 2.3 m/s and 3.6 m/s with adsorption of 0.266 grams water vapor / grams adsorbent and 0.264 grams water vapor / grams adsorbent as well as humidity of final air of 0.0194 kg water vapor/ kg dry air and 0.0198 kg water vapor/ kg dry air . The highest adsorption of water vapor using alumina was obtained at velocities of 2.3 m/s and 3.6 m/s with adsorption of 0.147 grams water vapor / gram adsorbent and 0.140 grams water vapor / gram adsorbent and the final humidity of 0.0207 kg water vapor / kg dry air and 0.0194 kg water vapor / kg dry air and the highest water vapor adsorption using zeolite was obtained at 3.6 m/s with the adsorption capacity of 0.130 grams water vapor / grams adsorbent and the final humidity of 0.0193 kg water vapor / kg dry air. Silica gel was the best desiccant in the process of moisture adsorption in air compared to alumina and zeolite.