问题 问答题 简答题

顶烧和侧烧转化炉对转化有何不同要求?

答案

参考答案:

顶烧转化炉中最高的烟气温度在炉膛上部,再加火焰的辐射热,要求转化催化剂能在此段剧烈反应吸收大量热,并能承受较高的温度,目前国产的Z402、Z409、Z417等催化剂正好具备这种特点。

侧烧转化炉可通过调节上排火嘴使炉膛上部保持较低的温度,这正好满足低温活性良好的Z403H型催化剂要求3米温度不大于630℃的特点。

根据研究和使用结果,Z402、Z409、Z417等催化剂也适用于侧烧炉型。

填空题
单项选择题

More surprising, perhaps, than the current difficulties of traditional marriage is the fact that marriage itself is alive and thriving. As Skolnick notes, Americans are a marrying people: Relative to Europeans, more of us marry and we marry at a younger age. Moreover, aster a decline in the early 1970s, the rate of marriage in the United States is now increasing. Even the divorce rate needs to be taken in this pro-marriage context: some 80 percent of divorced individuals remarry. Thus, marriage remains, by far, the preferred way of life for the vast majority of people in our society.

What has changed more than marriage is the nuclear family. Twenty-five years ago, the typical American family consisted of a husband, a wife, and two or three children. Now, there are many marriages in which couples have decided not to have any children. And there are many marriages where at least some of the children are from the wife’s previous marriage, or the husband’s, or both. Sometimes these children spend all of their time with one parent from the former marriage; sometimes they are shared between the two former spouses.

Thus, one can find the very type of family arrangement. There are marriages without children; marriages with children from only the present marriage; marriages with "full-time" children from the present marriage and "part-time" children from former marriages. There are step-fathers, step-mothers, half-brothers, and half-sisters. It is not all that unusual for a child to have four parents and eight grandparents! These are enormous changes from the traditional nuclear family. But even so, even in the midst of all this, there remains one constant: Most Americans spend most of their adult lives married.

Which of the following can be presented as the picture of today’s American families()

A. A typical American family consists of only a husband and a wife

B. Many types of family arrangements have become socially acceptable

C. Americans prefer to have more kids than before

D. There are no nuclear families any more