Abstract
The production of ammonia, consuming up to 5% of natural gas global production, accounts for about 2% of world energy. Worldwide, the Haber–Bosch process is the mainly used method of ammonia catalytic synthesis, involving temperatures up to 600 °C and pressures up to 32 MPa. In this paper, the results of the development and study of the special welded construction of plate heat exchanger (WPHE) for a column of ammonia synthesis are presented. The heat transfer and hydraulic performance of developed WPHE are investigated on a one-pass model in laboratory conditions. An equation for the relation between heat transfer effectiveness and the number of heat transfer units is proposed. A mathematical model of multi-pass WPHE is developed using these results. The validity of this model is confirmed by results of industrial tests performed with the prototype WPHE installed in operating column of ammonia synthesis at temperatures about 500 °C and pressure about 32 MPa. The tests confirmed the reliability of WPHE and its efficiency compared to a tubular heat exchanger. A method of optimal design of WPHE that allows finding the optimal height of corrugations and the number of passes in WPHE for specified conditions of operation is developed.
Highlights
The sustainable development of modern society requires the efficient energy usage to limit the depletion of fossil fuels resources and minimise the environmental hazard of their combustion, which is leading to the generation of harmful emissions and, especially, CO2 and greenhouse gases.It is the most important for industries with high levels of energy involved in production processes.One of such processes is the synthesis of such valuable product as ammonia, which is widely used in different industrial applications, such as the production of fertilisers, fibres, polymers and plastics, papers, acids and explosive materials [1]
The experimental study of thermal and hydraulic performance in one pass of welded construction of plate heat exchanger (WPHE) developed for operation at high temperature, and pressure in the ammonia synthesis column is conducted
The relation between heat transfer effectiveness ε and number of transfer units number of heat transfer units (NTU) in such conditions are established as coefficients of local hydraulic resistance at entrance and exit zones of investigated channels
Summary
The sustainable development of modern society requires the efficient energy usage to limit the depletion of fossil fuels resources and minimise the environmental hazard of their combustion, which is leading to the generation of harmful emissions and, especially, CO2 and greenhouse gases. The main feature of Compabloc WPHE is the use of crossflow of streams in one pass and the overall counter-flow arrangement in a whole heat exchanger Such a construction feature is used in WPHE, specially developed for operation inside the shell of the column for ammonia synthesis at temperatures up to 525 ◦ C and pressures about 320 bar [13] Plates are collected and welded together to form criss-cross flow channels with multiple contact points at the edges of corrugations It makes a robust construction capable of withstanding high-pressure difference between heat-exchanging streams. WPHE for an ammonia synthesis column with round plates that is accurate enough for engineering applications It is based on mathematical modelling and experimental data on heat transfer and pressure drop in WPHE channels. The use of the model for optimisation of WPHE for specific conditions of its operation is described
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