Title:	Conversion mechanism of bio-sludge hydrothermal carbonization
DNr:	SNIC 2022/22-475
Project Type:	SNIC Small Compute
Principal Investigator:	Haiman Hu <haiman.hu@ltu.se>
Affiliation:	Luleå tekniska universitet
Duration:	2022-05-02 – 2023-02-01
Classification:	20904
Keywords:

Abstract

Biological (bio)-sludge from paper mills is a biomass residue with huge annual out-put that is produced throughout the year and contains a large amount of organic matter. The discharge of this sludge to the environment can result in environmental pollution. Therefore, using bio-sludge as an energy source in blast furnace injection processes allows the sludge residue to be utilized as a resource while benefiting the sustainable develop-ment of the metallurgical industry. However, bio-sludge has low volume and energy density, low calorific value , and high alkali metal content, which greatly limits the direct use of the sludge. Therefore, the bio-sludge must be treated to improve its energy density for subsequent use in the metallurgical process. Hydrothermal carbonization is a very important part of biomass pretreatment thermochemical conversion technology. We have done a lot of experiments on biomass hydrothermal carbonization. But the hydrothermal carbonization process is carried out under high temperature and high pressure, and we don't know how the biomass is transformed to bio-char during the hydrothermal carbonization process, like a black box. Therefore, we need to simulate the decomposition process of biomass macromolecules by means of molecular simulation. First, we need to use Materials studio software to construct a molecular model of biomass, including cellulose, lignin and hemicellulose. These molecules are then wrapped in water molecules, simulating the real state of the experiment. Then use the ReaxFF MD method in Lammps to simulate the multi-component model of biomass, and then visualize the results through visualization software, such as VMD and OVITO software, so as to clarify the transformation process of biomass components under subcritical water conditions . At the same time, we will also explore the distribution and migration laws of the main constituent elements of biomass in the hydrochar products at different constant temperature stages under the condition of subcritical water. By comparing the differences in the carbonization behavior of hydrochar at different temperatures, the influence of hydrothermal carbonization conditions on biomass was studied, and the carbonization mechanism of biomass hydrochar was clarified. Due to the large number of atoms in the simulation process and the huge simulation system, ordinary computers can not meet our computing needs. Therefore, we want to maximize our computing needs by using supercomputers to speed up our computing process. At this stage, we can build models through ordinary computers, and then we need to upload the models and programs to supercomputers for simulation calculations.