(98d) Design (and Verification) of Controls Parameters to Minimize Emissions Due to Valve Retrofit

Abstract： The Tokyo Gas Corporation's Sodegaura Terminal is now one of the world's largest receiving terminals in the world. After the LNG is regasified, it is delivered to customers in the Tokyo cosmopolitan area by way of high pressure gas pipelines. From an economical and global warming point of view, the plant's operations and controls should have a minimal effect on the environment. This can be accomplished by limiting amounts of natural gas expelled into the atmosphere. The existing pressure control valve (CV) used for start-ups and emergency cases is being replaced. This change is necessary due to expanded process requirements, design conditions, etc. This means that CV characteristics and controllability will be changed as a result. Fine-tuning of PID control parameters will be required; historically this has been done through actual operation of the plant. Prior to installation, we tuned the PID control parameters to optimum values through rigorous dynamic process models. This tuning was performed without any actual live operations. This allows us to reduce the amount of LNG vented to atmosphere during installation and commissioning of the new control valve. Proper tuning also allows us to minimize the amount of LNG vented during startup operations. This paper discusses the techniques used to examine controls scenarios, in this project. Part of this work was creation of a ?virtual plant' in a software model. When remodeling an existing plant, it is useful to have a virtual plant environment. Both the validity of the plant engineering design, and the chance to obtain an optimum adjusted parameter, are increased due to the use of a virtual plant environment for parameter tuning.