Comparison of condensing technologies for industrial applications

Many industries operate natural gas technologies such as gas turbines, gas engines and gas heaters to cover onsite process heat and electricity demand. Due to high return temperatures, classical condensing technology based on return flow and exhaust coupled via heat exchangers cannot exploit significant amounts of condensation heat. New technologies, which have arisen during the last decade, demand a revaluation of condensing technology in industrial applications. This study presents a method for the comparison of available technologies. Calculations comparing the effects of different exhaust gas compositions resulting from technology specific air ratios for combustion in combination with different return and process heat temperatures are performed in order to quantify the effects of condensing technology. The developed method, using the herein defined specific annuity difference, allows evaluating the impact of improving technology specific parameters such as temperature spread and coefficient of performance (COP), enabling to identify future research needs. Open absorption cycles, electrical driven and gas driven heat pumps as well as sorption heat pumps allow the utilization of condensation heat even at heating network or process return temperatures above the dew point. With the specific annuity difference approach the comparison of these technologies is possible. The risk posed by uncertain future developments such as gas prices and increasing prices for carbon emissions, possible taxation of these and emission trading, can motivate investment in active condensing technology, even if economic viability under current circumstances is not given.