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With development of compressed air drying equipment, the task of numerical modeling of dynamic sorption-regeneration processes is increasingly emerging at the design stage. The dynamic problem has no analytical solution and can be solved only by numerical methods.The paper presents a numerical method and a program developed to calculate dynamics of heat and mass transfer during adsorption drying of compressed air.As a basis, a simplified physical model of sorption kinetics is used which assumes that inside the granules of the adsorbent there is a complete equalization of parameters such as temperature and moisture content at any time. The parameters of thermal conductivity and diffusion inside the adsorbent granules are incomparably higher than similar parameters on the surface of granules.Based on the thermodynamic approach, a physical and a mathematical model of adsorption have been developed to calculate dynamic non-isothermal processes in adsorption drying apparatuses. The presented results of calculations confirm the possibility to analyze dynamics of heat and mass transfer processes in the dryer column in the moisture adsorption mode under various initial and boundary conditions, including those that vary within the drying cycle.

One of the areas of energy conservation is the use of an expander-generator sets, that convert pressurized natural gas into electricity. In applying the expander-generator set for using gas pressure power generation gas flow necessary to heat, as as a result of expansion of the gas in an expander and a corresponding lowering of the temperature, the formation of condensate and hydrates in gas pipelines and fittings, piping and, as a consequence, their blockage or obstruction. In connection with this gas before detander-generating set to be heated so that at its exit gas temperature was at least 0 0C. A scheme in which the heater is replaced by adsorption drying, which makes it possible to use an expander-generator set at low temperatures without the risk of it or after it, mist and hydrates. Gas adsorption drying - process is selective absorption of the surface pores of the solid adsorbent of water molecules from the gas, and then extract them from the pores by applying external influences. The process of adsorption drying gas can achieve dew point – 90 0C. Including this unit, or equivalent, in the scheme with the DHA, get simultaneous generation of electricity and "deep cold". Area of application "deep cold" is very broads. Along with all energy and chemical industries, he is in demand in the food industry, plants for the production of beer and soft drinks. Chill needed for freezing and for subsequent storage products in refrigeration terminals and warehouses. This article contains diagrams of the adsorption unit, unit the receipt of "deep cold", a description of their work and exergy analysis of the developed scheme.

Conventionally, energy-saving techniques in drying technology are sequential in nature. First, the dryer is optimized without heat recovery and then, based on the obtained process conditions, heat recovery possibilities are explored. This work presents a methodology for energy-efficient adsorption dryer design that considers sensible and latent heat recovery as an integral part of drying system design. A one-step pinch-based optimization problem is formulated to determine the operating conditions for optimal energy performance of such an integrated system subject to product quality. Because the inlet and target stream properties of the heat recovery network are determined by the adsorption drying conditions, they are unknown a priori and thus are determined simultaneously within the overall optimization using the pinch location method. Energy balances are written above and below the various pinch point possibilities and the optimal pinch point is that which minimizes the amount of external heating utility required while satisfying drying and thermodynamic constraints. Results for a single-stage zeolite adsorption drying process with simultaneous heat recovery optimization show a 15% improvement in efficiency compared to a sequentially optimized system. The improvement is traceable to alterations in enthalpy-related variables like temperatures and flow rates. The discrepancy in optimal operating conditions between the sequential and simultaneous cases underscores the need to change system operating conditions when retrofitting for heat recovery because previous optimal conditions become suboptimal when heat recovery is introduced. Also, compared to a conventional dryer (without an adsorption process) operating under similar conditions, energy consumption is reduced by about 55%. © 2011 Taylor & Francis Group, LLC.

This work presents a mixed integer nonlinear programming (MINLP) formulation for the design of energy-efficient multistage adsorption dryers within constraints on product temperature and moisture content. Apart from optimizing temperatures and flows, the aim is to select the most efficient adsorbent per stage and product to air flow configuration. Superstructure models consisting of commonly used adsorbents such as zeolite, alumina, and silica-gel are developed and optimized for a two-stage, low-temperature, adsorption drying system. Results show that the optimal configuration is a hybrid system with zeolite as the first-stage adsorbent and silica-gel as the second-stage adsorbent in counter-current flow between drying air and product. A specific energy consumption of 2,275 kJ/kg is achieved, which reduces to 1,730 kJ/kg with heat recovery by a heat exchanger. Compared to a conventional two-stage dryer at the same drying temperature, this represents a 59% reduction in energy consumption. The optimal system ensures the exhaust air temperature of the first-stage regenerator is high enough to regenerate the second-stage adsorbent so no utility energy is spent in the second stage. A higher second-stage adsorbent wheel speed favors energy performance as it becomes optimized for energy recovery while the first is optimized for dehumidification. Although this work considers three candidate adsorbents in a two-stage system, the same reasoning can be applied to systems with more stages and adsorbents. The developed superstructure optimization methodology can, by extension, be applied to optimize multistage hybrid drying systems in general for any objective. © 2012 Copyright Taylor and Francis Group, LLC.

This work presents a mixed integer nonlinear programming (MINLP) formulation for the design of energy-efficient multistage adsorption dryers within constraints on product temperature and moisture content. Apart from optimizing temperatures and flows, the aim is to select the most efficient adsorbent per stage and product to air flow configuration. Superstructure models consisting of commonly used adsorbents such as zeolite, alumina, and silica-gel are developed and optimized for a two-stage, low-temperature, adsorption drying system. Results show that the optimal configuration is a hybrid system with zeolite as the first-stage adsorbent and silica-gel as the second-stage adsorbent in counter-current flow between drying air and product. A specific energy consumption of 2,275 kJ/kg is achieved, which reduces to 1,730 kJ/kg with heat recovery by a heat exchanger. Compared to a conventional two-stage dryer at the same drying temperature, this represents a 59% reduction in energy consumption. The optimal system ensures the exhaust air temperature of the first-stage regenerator is high enough to regenerate the second-stage adsorbent so no utility energy is spent in the second stage. A higher second-stage adsorbent wheel speed favors energy performance as it becomes optimized for energy recovery while the first is optimized for dehumidification. Although this work considers three candidate adsorbents in a two-stage system, the same reasoning can be applied to systems with more stages and adsorbents. The developed superstructure optimization methodology can, by extension, be applied to optimize multistage hybrid drying systems in general for any objective. © 2012 Copyright Taylor and Francis Group, LLC.

Conventionally, energy-saving techniques in drying technology are sequential in nature. First, the dryer is optimized without heat recovery and then, based on the obtained process conditions, heat recovery possibilities are explored. This work presents a methodology for energy-efficient adsorption dryer design that considers sensible and latent heat recovery as an integral part of drying system design. A one-step pinch-based optimization problem is formulated to determine the operating conditions for optimal energy performance of such an integrated system subject to product quality. Because the inlet and target stream properties of the heat recovery network are determined by the adsorption drying conditions, they are unknown a priori and thus are determined simultaneously within the overall optimization using the pinch location method. Energy balances are written above and below the various pinch point possibilities and the optimal pinch point is that which minimizes the amount of external heating utility required while satisfying drying and thermodynamic constraints. Results for a single-stage zeolite adsorption drying process with simultaneous heat recovery optimization show a 15% improvement in efficiency compared to a sequentially optimized system. The improvement is traceable to alterations in enthalpy-related variables like temperatures and flow rates. The discrepancy in optimal operating conditions between the sequential and simultaneous cases underscores the need to change system operating conditions when retrofitting for heat recovery because previous optimal conditions become suboptimal when heat recovery is introduced. Also, compared to a conventional dryer (without an adsorption process) operating under similar conditions, energy consumption is reduced by about 55%. © 2011 Taylor & Francis Group, LLC.

Low-temperature drying is important for heat-sensitive products, but at these temperatures conventional convective dryers have low energy efficiencies. To overcome this challenge, an energy efficiency optimization procedure is applied to a zeolite adsorption dryer subject to product quality. The procedure finds a trade-off between the improved drying capacity due to dehumidification and energy expenditure due to regeneration while incorporating product drying properties. By optimizing the regeneration air inlet temperature, drying air, adsorbent, and regeneration air flow rates as well as sensible and latent heat recovery from the regenerator exhausts, the energy efficiency is improved by up to 45% compared to the state-of-the-art. The high mass transfer effect of high temperatures is utilized in the regenerator to boost dehumidification while isolating the heat-sensitive dried product from the quality-degrading effect. A process optimization procedure for maximizing energy efficiency is applied to a zeolite adsorption dryer subject to product quality. By optimizing the regeneration air inlet temperature, drying air, adsorbent, and regeneration air flow rates as well as sensible and latent heat recovery from the regenerator exhausts, the energy efficiency is improved by up to 45% compared to the state-of-the-art. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Low-temperature drying is important for heat-sensitive products, but at these temperatures conventional convective dryers have low energy efficiencies. To overcome this challenge, an energy efficiency optimization procedure is applied to a zeolite adsorption dryer subject to product quality. The procedure finds a trade-off between the improved drying capacity due to dehumidification and energy expenditure due to regeneration while incorporating product drying properties. By optimizing the regeneration air inlet temperature, drying air, adsorbent, and regeneration air flow rates as well as sensible and latent heat recovery from the regenerator exhausts, the energy efficiency is improved by up to 45% compared to the state-of-the-art. The high mass transfer effect of high temperatures is utilized in the regenerator to boost dehumidification while isolating the heat-sensitive dried product from the quality-degrading effect. A process optimization procedure for maximizing energy efficiency is applied to a zeolite adsorption dryer subject to product quality. By optimizing the regeneration air inlet temperature, drying air, adsorbent, and regeneration air flow rates as well as sensible and latent heat recovery from the regenerator exhausts, the energy efficiency is improved by up to 45% compared to the state-of-the-art. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.