Modelling and Validation of a Turbocharged FORMOX Plant in Aspen Plus

Sammanfattning

In the modern chemical industry heat and energy integration is crucial for optimizing process efficiency and increasing economic viability and environmental sustainability. By strategically recovering and reusing heat and energy within the plant, industries can significantly decrease their reliance on external energy sources, leading to costs saving and a smaller carbon footprint. One of the latest sustainability improvements to the FORMOX process is the addition of a turbocharger, which significantly reduces the power consumption of the process by recovering energy from the exhaust gases in a turbine. The turbocharger currently relies on a variable geometry, limiting the number of viable suppliers and incurring additional costs. This master’s thesis investigates the feasibility of using a fixed geometry turbocharger in the FORMOX process. A model was developed in Aspen Plus in accordance with a real plant with the pressure drop being modelled in the entire process. The model was validated with data from the plant before being used to examine the possibility of using a fixed turbine geometry. To make the new operation feasible a portion of the compressor discharge flow could be bypassed directly to the turbine inlet. Additionally, a portion of the turbine inlet flow could bypass the turbine through a wastegate. The results demonstrated that the new operation was feasible. However, the new operation led to significantly decreased steam production and increased power requirements of the fans, resulting in substantially increased direct variable costs. In the most favorable case, the direct vaiable costs are increased by €175,000 per year, as such the new operation was deemed to be economically infeasible. The model could be further improved by incorporating additional user subroutines to more accurately model the pressure drop in the process. Additionally, a dynamic pressure-driven simulation is required to study the transient behavior and stability of the new operation.