Energy efficiency improvements of a nitrile production unit
Examensarbete för masterexamen
Today when CO2-emissions are more in focus due to the occurring climate changes, companies are eager to reduce their energy demand to lower their CO2-emissions. The studied nitrile production unit in Mons, Belgium is one of the most energy intensive units within AkzoNobel Surface Chemistry AB. This master thesis has investigated the possibilities for energy reductions using pinch analysis as a part of AkzoNobel’s work to reduce the CO2-emissions by lowering the energy demand. From the pinch analysis suggestions are made, that will lower the pinch violations and so reduce the energy used. In this report there are also other modifications suggested, above the integration of heat exchangers based on the pinch analysis, which modifies the recovery of one of the reactants (ammonia) to lower the energy demand. The results from the pinch analysis shows pinch violations of 974 kW indicating that 1948 kW of energy utility could be reduced. In the suggested retrofits five new heat exchangers are installed, four in new positions and one is an extension of already existing heat exchanger position. These modifications would reduce the pinch violations with 857 kW, i.e. 88% of the present, saving 1714 kW of energy in both cooling water and hot oil. The yearly savings are approximately 517 k€ and the investment is 300-500 k€ depending on material and sizes of the heat exchangers, which gives a payback period of less than a year. The present ammonia recovery system includes an absorption in water. A suggestion proposed within this work is to have a compressor increasing the pressure of a part of the flow. This is, however, an expensive modification since a 2-stage compressor with inter-cooling would be installed. The savings potential is 4.9 MW of mainly high pressure steam and cooling water but also some hot oil. The investment would be 2.9 M€ and the savings is roughly 970 k€/year resulting in a payback time of approximately 3 years. These two modifications proposed are nearly independent of each other, the total savings from these suggestions are 1.5 M€/year and 6.6 MW. There are also other positive outcomes from this such as a reduced amount of CO2-emissions and decreased use of water, but no values for this has been calculated.
Energi , Hållbar utveckling , Kemiska processer , Energy , Sustainable Development , Chemical Process Engineering