Wei Wu
National Cheng Kung University,Taiwan
Title: Process design of hydrogen production, purification and compression subject to near-zero carbon emissions
Biography
Biography: Wei Wu
Abstract
Since the hydrogen production system includes reaction and separation processes, it commonly involves large temperature gradients. Overall minimum hot and cold utility targets required to achieve the saving energy are implemented in hydrogen production, industrial plants, and bioprocesses. Friedler indicated that energy saving, global warming and greenhouse gas emissions have become major technological, societal, and political issues. In particular, process integration has not been satisfactorily developed to solve various energy-related problems by using heat exchanger networks (HENs). In this article, the process design of hydrogen production, purification and compression is carried out in Aspen Plus environment. The hydrogen production process with a combination of a steam methane reforming (SMR) reactor, a carbon dioxide reforming of methane (CO2R) reactor and a water-gas-shift (WGS) reactor is presented. The process of hydrogen purification and compression (HPC) is developed to meet the specifications of high-pressure hydrogen storage and improve the energy efficiency. The oxy combustion combined with the heat exchanger network is integrated into the system to address near-zero carbon emissions. Hydrogen production process To develop the hydrogen production process with low carbon emissions, the SMR+CO2R+WGS process is utilized. Process of hydrogen purification, compression and carbon dioxide recovery For the objective of the hydrogen storage and CO2 recovery, the process of hydrogen purification, compression and carbon dioxide recovery (HPCC) is carried out. If it is connected to the SMR+CO2R+WGS processes, then the integrated process is named as the SCWH (SMR+CO2R+WGS+HPCC) process. Notably, the condensed water can be recycled and the feed of CO2 can be captured from the flue gas, and this high-pressure hydrogen production system can contribute to reduce carbon emissions. Regarding the oxy combustion approach, the oxygen required is separated from air prior to combustion and the fuel is combusted in oxygen diluted with recycled flue-gas rather than by air. This oxygen-rich, nitrogen-free atmosphere results in final flue-gases consisting mainly of CO2 and H2O (water), so producing a more concentrated CO2 stream for easier purification. Assumed that the QC6 is completely recovered, the Qneed of the whole processes is less than the corresponding QC6. Heat integration To reduce the external energy supply, the heat integration design using the heat exchanger networks (HENs) is a typical approach to achieve the maximum waste heat recovery. Using the hot/cold stream data, the design of HENs is applied to meet the maximum energy recovery, the heat-integrated system with HENs is done by using Aspen Energy Analyzer. This study examined an integration of hydrogen production and compression system subject to heat integration and carbon dioxide reduction. The main results are summarized as follows: 1. The conceptual design of the hydrogen production process using SMR, CO2R and WGS is addressed in Aspen Plus environment. 2. The CO2R unit can consume extra CO2 and effectively enhance the hydrogen yield of the system. 3. The sensitivity analysis of operating variables with regard to feed conditions is investigated. 4. The optimal HEN meets the target of the maximum heat recovery, so it can reduce the utility load for cooling by 65% and heaters are not required.