问题 问答题 简答题

什么是SNCR烟气脱硝技术?

答案

参考答案:

SNCR烟气脱硝技术是一种不需要催化剂的选择性非催化还原技术(SelectiveNon-CatalyticReduction,简称SNCR)。该技术是用NH3、尿素等还原剂喷入炉内与NOx进行选择性反应,不用催化剂,因此必须在高温区加入还原剂。还原剂喷入炉膛温度为850~1100℃的区域,该还原剂(尿素)迅速热分解成NH3并与烟气中的NOx进行SNCR反应生成N2,该方法是以炉膛为反应器,在炉膛850~1100℃这一狭窄的温度范围内、在无催化剂作用下,NH3或尿素等氨基还原剂可选择性地还原烟气中的NOx,基本上不与烟气中的O2作用,其主要反为:NH3为还原剂:4NH3+4NO+O2→4N2+6H2O尿素为还原剂:NO+CO(NH22+1/2O2→2N2+CO2+H2O当温度高于1100℃时,NH3则会被氧化为NO,即:4NH3+5O2→4NO+6H2O不同还原剂有不同的反应温度范围,NH3的反应最佳温度区为850~1100℃。当反应温度过高时,由于氨的分解会使NOx还原率降低,另一方面,反应温度过低时,氨的逃逸增加,也会使NOx还原率降低,且NH3是高挥发性和有毒物质,其逃逸会造成新的环境污染。SNCR烟气脱硝技术的脱硝效率一般为25%~50%,受锅炉结构尺寸影响很大,多用作低NOx燃烧技术的补充处理手段。

阅读理解

阅读理解。

     This story about an old man and a clever monkey is a very old one. Aesop, a Greek writer, first told

the story many years ago. This monkey belonged to an old man. The old man was very fond of the garden,

so when birds came to the garden, he chased them away. He also helped the old man in many other ways.

The old man often fell asleep during the day in his chair. Then the monkey sat at the old man's side and

chased the flies away from the old men's face.

     One hot afternoon in the summer, the old man was asleep in his chair. A fly came and sat on the end

of the old man's nose. The monkey chased it away. Soon the fly came back and sat on the old man's

nose again. The monkey chased it away. This continued for five or six times. The monkey at last became

very angry. He jumped up, ran to the garden, and picked up a large stone. The next time when the fly sat

on the old man's nose, the monkey hit it hard with the stone. He killed the fly, but unfortunately he broke

the old man's nose.

1. This story was first told by a Greek _____. [ ]

A. famous poet

B. great philosopher

C. fable writer

D. well-known physicist

2. When birds came to the garden, the monkey chased them away. The verb "chase" means _____. [ ]

A. drive out

B. get hold of

C. catch up with

D. keep up with

3. The monkey picked up a large stone, because he wanted _____. [ ]

A. to fight to death

B. to put the fly to death

C. to hit the fly on the head

D. to strike the old man on the nose

4. The monkey at last became angry, because _____. [ ]

A. the old man didn't give him anything to eat

B. the old man made the monkey do nothing

C. the old man often fell asleep during the day in his armchair

D. He couldn't drive the fly away

5. Which of the following statements is true according to this passage?[ ]

A. From this story we can learn; sometimes things done out of harmful will may be good.

B. From this story we can learn; sometimes things done out of good will may be good.

C. From this story we can learn; sometimes things done out of harmful will may be harmful.

D. From this story we can learn; sometimes things done out of good will may be harmful.

单项选择题