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

世界上与一次能源使用相关的二氧化碳排放量增加更多。从环境的角度来看，减少二氧化碳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。在本报告中，我们研究了升华法去除燃烧气体中的CO_2。所得结果总结如下：(1)提出了一种利用化石燃料发电厂燃料液化天然气（LNG）冷源升华脱除CO_2的新系统。去除方法分为直接升华和间接升华两种系统。(2)作为该系统的基础研究，对雾形成过程中的结霜现象进行了实验和理论研究。在雾流中，由于热泳动和重力引起的雾迁移对传质起着重要的作用。基于考虑雾在饱和气流中迁移的模型，给出了传质系数。(3)研究了CO_2和H_2O蒸汽的结霜沉积。该过程分为复合霜生长期和h2o霜生长期两个阶段。霜沉积是基于一个由CO_2和H_2O霜组成的模型，并考虑两种蒸汽的内部扩散。

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.