Papermaking ranks third behind only petroleum refining and chemical production in terms of energy consumption. Recently, simulations made possible by the U.S. Department of Energy’s HPC4Mfg program helped a group of paper companies develop a strategy likely to cut energy costs by 10-20 percent.
“This was true ‘HPC for manufacturing,’” said David Trebotich, a computational scientist in the Computational Research Division at Berkeley Lab and co-PI on the project. “We used 50,000-60,000 cores at NERSC to do these simulations. It’s one thing to take a research code and tune it for a specific application, but it’s another thing to make it effective for industry purposes. Through this project we have been able to help engineering-scale models be more accurate by informing better parameterizations from micro-scale data.”
The effort was run jointly with the companies and Lawrence Livermore National Laboratory and Lawrence Berkeley National Laboratory. Simulations were run on the National Energy Research Supercomputing Center’s Edison system. A brief account of the project is on the NERSC web site (HPC4Mfg Paper Manufacturing Project Yields First Results). The first phase targeted “wet pressing”—an energy-intensive process in which water is removed by mechanical pressure from the wood pulp into press felts that help absorb water from the system like a sponge before it is sent through a drying process.
“The major purpose is to leverage our advanced simulation capabilities, high performance computing resources and industry paper press data to help develop integrated models to accurately simulate the water papering process,” said Yue Hao, an LLNL scientist and co-principal investigator. Trebotich ran a series of production runs on NERSC’s Edison system and was successful in providing his LLNL colleagues with numbers from these microscale simulations at compressed and uncompressed pressures, which improved their model.
“I used the flow and transport solvers in Chombo-Crunch to model flow in paper press felt, which is used in the drying process,” Trebotich explained. “The team at LLNL has an approach that can capture the larger scale pressing or deformation as well as the flow in bulk terms. However, not all of the intricacies of the felt and the paper are captured by this model, just the bulk properties of the flow and deformation. My job was to improve their modeling at the continuum scale by providing them with an upscaled permeability-to-porosity ratio from pore scale simulation data.”
Image: The researchers used a computer simulation framework, developed at LLNL, that integrates mechanical deformation and two-phase flow models, and a full-scale microscale flow model, developed at Berkeley Lab, to model the complex pore structures in the press felts. Image: David Trebotich, Berkeley Lab