Theoretical analysis of steam generation methods - Energy, CO2 emission, and cost analysis

• Application of heat pump technology for generating steam.
• Using low-pressure boiler to evaporate water at low temperature.
• Usage of waste heat to evaporate water.
• Comparison of operating cost and CO2 emission of two different countries.

A theoretical case study on steam generation has been performed. Different methods of producing steam by vapour compression, direct electrical heating, gas heating, heat pumping, use of waste heat, and a mixture thereof, were theoretically analysed. The final state of the steam had a pressure of 3 bar, which is common for a low pressure industrial steam network. Simulations using EES were performed in order to calculate the energy necessary to generate 1 kg of steam with each method. The CO2 emission and an approximation of the operating cost for each method was also calculated. The gain of using waste heat at different temperatures was evaluated. Steam generation by vapour compression can reduce the energy consumption by up to a factor of 6. The CO2 emitted during the production of electricity is crucial in determining the most efficient method when global warming is concerned. Cost analysis shows that gas-fired boilers have the lowest operating cost in the United States, however, vapour compression methods can be cost-competitive depending on the availability of waste heat and the electricity to gas price ratio. Heat pumps are very efficient and have the advantage of running even without heat recovery from waste heat.