问题 问答题 简答题

氧气纯度差的原因是什么?

答案

参考答案:正常工况下,氧纯度的高低取决于上塔提馏段的回流比,回流比增加,氧纯度下降。

原因:

(1)塔板效率下降,塔板堵塞、塔板倾斜、传质效果不好等。

(2)精馏工况异常:发生液泛或液漏。

(3)冷凝蒸发器工作异常:杂质影响主冷换热,加工空气量减少。

(4)氧气取出量过大:使上塔上升气减少,回流比增加。氮蒸发不充分。

(5)LA(含氧)纯度低:下塔回流比增大。

(6)主冷凝蒸发器液氧液面上升:上塔下流液过大,回流比上升。

阅读理解

阅读理解。

     Kenyon Scudder once told me a story about his friend, Michael. Michael happened to be on a train

sitting next to a young man who seemed worried. Finally the young man told the friend that he was a

convict (罪犯) returning home from a prison far away. What he did had brought shame (羞耻) on his

family, and they had neither visited him nor written to him. He hoped, however, that this was only because

they were too poor to travel and too busy to write.

     When he was set free he had written to tell them he wanted to go home. To make matters easy for

them, however, he had asked them to put up a signal (信号) for him when the train passed their little farm. If the family had forgiven (原谅) him, they were to put up a white ribbon (丝带) in the big apple tree near

the railway. If they didn't want him back, they were to do nothing, and he would stay on the train, and go

far away.

     As the train neared his hometown his suspense became so great that he was afraid to look out of the

window. He asked Michael to watch for the big apple tree. They changed seats. In a minute, Michael put

his hand on the young convict's shoulder. "There it is," he said, his eyes filled with sudden tears. "It's all

right. The whole tree is white with ribbons."

1. For which of the following reasons might the young man be worried?

A. His family might not allow him to go home.

B. His family would not remember him.

C. His family hadn't written to him frequently.

D. His family hadn't visited him for a long time.

2. The word "suspense" underlined in the last paragraph can best be replaced by _____.

A. pain        

B. interest  

C. worry    

D. happiness

3. Why did Michael cry at the end of the story?   

A. The young man couldn't live with his family.

B. There were many white ribbons on the apple tree.

C. He was moved by the young man.

D. The young man was very sad.

单项选择题