Effects of utility steam temperature on the cost of steam systems in industry

Today, process industries are responsible for a large portion of the world’s energy demand. Integration of heat pumps and electric heaters to electrify industrial processes is necessary to decarbonize the sector. For applications below 250 °C, high pressure steam usually generated in water-tube boilers is the most used energy carrier. With the introduction of heat pumps, however, lowering the pressure of the generated steam presents some advantage. Unlike traditional boilers, the efficiency and cost of High Temperature Heat Pumps (HTHP) highly depend on the temperature level at which they deliver heat. This paper evaluated the consequences on the overall cost of the steam system of lowering the design temperature of the steam. The effects of steam pressure on the piping of the system were evaluated in general terms, including heat and pressure losses. The heat transfer coefficient and change in the area of heat exchangers were also analyzed. Finally, the increase on the cost of the steam distribution and the heat exchangers due to lower steam temperatures was estimated for a case study. The results of the analysis show the growth of capital cost of the system as the temperature of the utility is decreased. In the case study, the reduction of steam temperature from 230 to 110 °C increased the cost of the heat exchangers by 2% and the pipework by 110%. However, the improvement in efficiency of the heat pump greatly overcomes this cost. This indicates the importance of the design utility temperature for the correct integration of HTHP in low-temperature industries.