问题 单项选择题

下列选项中,( )是预防锅炉结渣的主要措施之一。

A.加强吹灰
B.减少锅炉的启停次数
C.设置炉膛安全保护装置
D.炉膛中布置足够的受热面

答案

参考答案:D

解析:锅炉结渣预防。预防结渣的主要措施有:(1)在设计上要控制炉膛燃烧热负荷,在炉膛中布置足够的受热面,控制炉膛出口温度,使之不超过灰渣变形温度;合理设计炉膛形状,正确设置燃烧器,在燃烧器结构性能设计中充分考虑结渣问题;控制水冷壁间距不要太大,而要把炉膛出口处受热面管间距拉近;炉排两侧装设防焦集箱等。(2)在运行上要避免超负荷运行;控制火焰中心位置,避免火焰偏斜和火焰冲墙;合理控制过量空气系数和减少漏风。(3)对沸腾炉和层燃炉,要控制送煤量,均匀送煤,及时调整燃料层和煤层厚度。(4)发现锅炉结渣要及时清除。清渣应在负荷较低、燃烧稳定时进行,操作人员应注意防护和安全。

阅读理解

The Earth has warmed by about half a degree(0.50℃)over the last 100 years. It could be getting warmer on its own, but many scientists think that people are making the Earth warmer by making a greenhouse effect. The greenhouse effect is important.  Without it, the Earth would not be warm enough for us to live on. But just a little warmer than it is now could cause problems for humans, plants and animals.

Many of the things we do every day can change the Earth’s temperature by sending greenhouse gases into the air. We send greenhouse gases into the air when we watch TV, turn on lights, dry hair, play video games, wash or dry our clothes or drive cars. The rubbish from factories and homes also produces greenhouse gases.

Even a small change in temperature can affect our weather. This can cause changes in the sea levels, the air, flooding, and our fresh water.

The change in the temperature can also cause changes in the living places for animals and plants, endangering many animals.

Global warming is a big problem, and every little bit we do can help. We can save electricity. We can save energy in other ways such as by taking buses or walking rather than driving cars. We can recycle to reduce the rubbish and save natural resources such as trees, oil and metals. We can buy products that don’t do bad to the environment and we can turn to solar energy. Remember the little bit that you do will bring a better world.

小题1: Which of the following does not send greenhouse gases into the air?

A.Watching TV.

B.Turning on a light.

C.Driving a car.

D.Walking to school.小题2: In this passage, the scientists are mainly trying to make the readers realize___________ .

A.the greenhouse effect is important

B.humans are making the earth warmer

C.the earth is getting warmer in 100 years

D.the earth could be getting warmer by itself小题3: Without the greenhouse effect,we would _____________ .

A.be safer

B.not be able to live

C.have a cleaner earth

D.have a better world小题4: The writer gives us advice on how to save energy in __________ .

A.Paragraph 2

B.Paragraph 3

C.Paragraph 4

D.Paragraph 5小题5: Global warming is a big problem but ___________ .

A.we can't do anything to help

B.we don't need to do anything

C.we can do something to help

D.we can do something to stop it

单项选择题