A Study of Carbon-dioxide Removal due to Sublimation Utilizing LNG Cold

与一次能源使用相关的世界CO_2排放量增加更多。从环境的角度来看，减少CO_2的排放是一个非常重要的问题。到目前为止，由于吸收和吸附过程，已经提出了许多与CO_2脱除有关的方法。本文研究了利用升华法脱除燃烧气体中CO_2的方法，主要结果如下：（1）提出了以化石燃料发电厂的液化天然气（LNG）为冷源，利用升华法脱除CO_2的新系统。去除方法分为两个系统，直接和间接升华系统。(2)As作为该系统的基础性研究，本文对雾沫形成时的霜沉积进行了实验和理论研究。热泳和重力作用下的雾迁移对雾流中的传质起着重要的作用。基于考虑雾在饱和空气流中迁移的模型，提出了雾的传质系数。（3）研究了CO_2和H_2O蒸汽的结霜现象。该过程可分为两个阶段，即复合霜生长期和H_2O霜生长期。根据由CO_2和H_2O霜层组成的模型，考虑了霜层内CO_2和H_2O的扩散，预测了霜层的沉积。

The world CO_2 emission associated with primary energy use has increased more. From the environmental viewpoint, it is a very important problem to reduce the CO_2 emission. Up to the present, many methods due to absorption and adsorption processes have been presented relating to the CO_2 removal. In this report, we have investigated the removal of CO_2 in combusion gas due to sublimation.The results obtained here are summarized as follows ;(1)we have presented new system of CO_2 removal due to sublimation by using the cold source of LNG(liquefied natural gas), which is used as fuel at the fossil fuel fired power generation plant. The removal method is divided into two systems, direct and indirect sublimation systems.(2)As a basic study of the system, frost deposition occurring with mist formation has been investigated experimentally and theoretidcally. Mist migration due to thermophoresis and gravity force plays an important role on mass transfer in mist flow. Based on a model considering mist migration in saturated air flow, mass transfer coefficients have been presented.(3)Frost deposition of CO_2 and H_2O vapors has been investigated. The process was divided into two periods, composite frost growth period and H_2O frost growth period. Frost deposition has been predicted based on a model which is composed of CO_2 and H_2O frosts and is considered internal diffusion of both vapors.