Integrated process-to-system modeling of a sulfuric acid plant with thermal management

Sulfuric acid (H₂SO₄) is a very important bulk inorganic chemical, and even little improvements in energy efficiency can create significant impacts on the economy and the environment. This work constructs a detailed process model of a conventional contact-process sulfuric acid plant and is used to assess production efficiency and waste heat recovery potential. The process design comprises a sulfur furnace, four catalytic converter beds with inter-bed cooling, a packed absorption column, a post-absorber polishing reactor, and the primary process coolers. The model validation using current industry data demonstrates consistency in bed-by-bed temperature profiles, overall SO₂-to-SO₃ conversions, absorber efficiency, and primary heat exchanger performance. The designed process produces sulfuric acid at 98.5 wt% H₂SO₄, matching the concentration range typically required for commercial-grade concentrated acids. A detailed thermal management is performed to identify the major recoverable thermal streams within the plant. The furnace gas boiler (E-100) and absorber outlet cooler (E-105) are identified as the principal recoverable waste heat sources at both high- and low-temperature levels. This available heat is recovered through a multistage Organic Rankine Cycle (ORC) utilizing n-pentane as the working fluid and generates net power output of approximately 506.6 kW with a thermal efficiency of 18.9%. Sensitivity analyses indicate that the catalytic converter demonstrates substantial tolerance to temperature fluctuations while the performance of the absorber and polishing reactor is evidently influenced by water-balance management. These findings indicate that ORC-based waste heat recovery is a viable and technically feasible approach for improving overall plant energy efficiency and partially offsetting auxiliary power consumption in sulfuric acid facilities utilizing the contact process.