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Abstract

A sulfuric acid (H2SO4) production unit by a double absorption contact process at industrial scale generates significant waste heat that amounts to 22 MW for a production of 1500 tons/day. The waste heat is released to the environment at a temperature of 38°C. This study aims to analyze the current situation and propose a sustainable solution to valorize these losses. According to the available data, it is proposed to use the heat for the refrigerated storage of ammonia through absorption machines. In fact, Ammonia is currently stored in the same chemical plant at atmospheric pressure and a temperature of - 33°C. To keep it in a liquid state, large amounts of heat must be continuously removed by a compression refrigeration cycle. By switching to absorption heat pumps, most of the necessary energy can be drawn from the thermal discharges of the sulfuric unit. A comprehensive technical feasibility study was conducted in the present work to achieve this aim. The proposed solution is to use a heat recovery loop for the production of hot water from this waste. The hot water is then used to drive a half-effect absorption machine, running on NH3-LiNO3, which will keep ammonia at the liquid state. The heat recovery loop was simulated using HYSYS while the absorption refrigeration calculations were carried out using the Oldham and Merkel diagrams. According to these calculations, a COP of about 0.25 was obtained which is very significant for an absorption refrigeration cycle running on waste heat and cooling down to -33°C. The obtained results can serve as a valuable basis to guide future research efforts and decision-making in this regard.

Keywords: absorption refrigeration, waste heat recovery, sulfuric acid, ammonia storage, COP, HYSYS

(ProQuest: ... denotes formulae omitted.)

Nomenclature

ARC Absorption Refrigeration Cycle

COP Coefficient of performance

a Absorber

c Condenser

e Evaporator

g Generator

h Specific enthalpy

m Mass flow rate

P Pressure

P Pump

Q Heat

T Temperature

W Work

x Mass fraction

Xr Mass fraction of the rich solution

Xw Mass fraction of the lean solution

1.Introduction

Since energy plays a crucial role in human life, well-being, economic and industrial growth of the countries worldwide, meeting the growingdemand for energy in a safe and environmentally friendly wayrepresents a big challenge (Mehrpooya...

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