问题 问答题 简答题

锅炉用煤对煤中的水分有哪些要求?

答案

参考答案:

水分,它是电力用煤的一项重要特性指标,水是煤中不可燃成份,煤中水分含量高,势必增大运输量,多付费用,热值降低,水分大,锅炉烟气量增加,由烟气带走的热量也越多,因此加大了排烟热损失,及排风机的电耗,所以电厂用煤水分较低为好,但水分过低也有弊端,这易造成煤粉飞扬而污染环境,同时煤中含有适量的水分对燃烧有利,火焰中含有水汽对煤粉的悬浮燃烧能起催化作用。电力用煤的水分宜控制在5%-8%。如煤的外在水分超过8%-10%,这将导致输煤、给煤系统运行的障碍。

填空题

You might think that hamburgers were invented in the United States, but that is not totally true. These (1) , or patties, actually came from Germany in the middle of the nineteenth century. They were brought to the United States by (2) who came from the city of Hamburg. That is why (3) was "hamburger steak".

However, people in other places (4) that they invented the hamburger. Perhaps we’ll never have a (5) . But there’s no question that the hamburger was a (6) . Why Perhaps because at that time, industry was growing and a kind of (7) food was needed for workers.

The hamburger became even more popular (8) when the first chain of fast food restaurants was started. This chain was called "White Castle". It served tiny hamburgers that were sold for only (9) . Then, in the 1930s there came the (10) where customers were served in their cars by waiters in uniform. And the hamburger was one of the most (11) .

By now, The hamburger was ready to (12) the world. And this happened with McDonald’s, which was actually a (13) at first. But by the early 1950s the hot dog was replaced by the hamburger. McDonald’s and other fast food restaurants (14) around the world throughout the rest of the twentieth century. McDonald’s alone has (15) for everyone person in the world.

The importance of the hamburger to (16) remains significant. About (17) of all sandwiches that are eaten are hamburgers. According to some sources, (18) of current workers in the United States had their first job at McDonald’s. But the face of the hamburger is changing (19) . Nowadays it is possible to buy a chicken burger, a turkey burger, (20) , or veggie burger.

7()

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