计算综合5.如下图所示某石油化工厂的油品储罐,为使油品不与空气接触被氧化变质,或引起爆炸危险,需要进行罐顶封氮。其技术要求是:始终保持罐内氮气压力微正,当罐内液位上升时,应停止继续补充氮气,并将压缩的氮气适量排出;当罐内液位下降时,应停止放出氮气。（1）试设计罐顶氮气压力分程控制系统（画在题图上）；（2）选择两调节阀的气开气关属性，说明理由；（3）确定压力控制器的正反作用。

<span style="line-height: 28.3333px;">（1） 解：控制流程图</span><div><span style="line-height: 28.3333px;"><img src="https://s3.cn-north-1.amazonaws.com.cn/qingshuxuetang/examination/imgUplod/14973377340431e8b13b1ab0f45b49cd66c7f6c77471f.png" alt="上传图片"><br></span></div><div><p class="MsoNormal" style="text-indent:30.0000pt;mso-char-indent-count:2.5000;line-height:150%;mso-list:l0 level1 lfo1;"><!--[if !supportLists]--><span style="font-family:宋体;font-size:12.0000pt;mso-font-kerning:1.0000pt;">（2）</span><!--[endif]--><span style="mso-spacerun:'yes';font-family:宋体;line-height:150%;font-size:12.0000pt;mso-font-kerning:1.0000pt;"><font face="宋体">从安全角度考虑，进</font></span><span style="mso-spacerun:'yes';font-family:宋体;line-height:150%;font-size:12.0000pt;mso-font-kerning:1.0000pt;">N</span>_{<span style="mso-spacerun:'yes';font-family:宋体;line-height:150%;font-size:12.0000pt;mso-font-kerning:1.0000pt;vertical-align:sub;">2</span>}<span style="mso-spacerun:'yes';font-family:宋体;line-height:150%;font-size:12.0000pt;mso-font-kerning:1.0000pt;"><font face="宋体">阀：开</font></span><span style="mso-spacerun:'yes';font-family:宋体;line-height:150%;font-size:12.0000pt;mso-font-kerning:1.0000pt;">&nbsp;</span><span style="mso-spacerun:'yes';font-family:宋体;line-height:150%;font-size:12.0000pt;mso-font-kerning:1.0000pt;"><font face="宋体">；排</font></span><span style="mso-spacerun:'yes';font-family:宋体;line-height:150%;font-size:12.0000pt;mso-font-kerning:1.0000pt;">N</span>_{<span style="mso-spacerun:'yes';font-family:宋体;line-height:150%;font-size:12.0000pt;mso-font-kerning:1.0000pt;vertical-align:sub;">2</span>}<span style="mso-spacerun:'yes';font-family:宋体;line-height:150%;font-size:12.0000pt;mso-font-kerning:1.0000pt;"><font face="宋体">阀：气关</font></span><span style="mso-spacerun:'yes';font-family:宋体;line-height:150%;font-size:12.0000pt;mso-font-kerning:1.0000pt;">&nbsp;</span><span style="mso-spacerun:'yes';font-family:宋体;line-height:150%;font-size:12.0000pt;mso-font-kerning:1.0000pt;"><o:p></o:p></span></p><p class="MsoNormal" style="text-indent:30.0000pt;mso-char-indent-count:2.5000;line-height:150%;mso-list:l0 level1 lfo1;"><!--[if !supportLists]--><span style="font-family:宋体;font-size:12.0000pt;mso-font-kerning:1.0000pt;">（3）</span><!--[endif]--><span style="mso-spacerun:'yes';font-family:宋体;line-height:150%;font-size:12.0000pt;mso-font-kerning:1.0000pt;">&nbsp;</span><span style="mso-spacerun:'yes';font-family:宋体;line-height:150%;font-size:12.0000pt;mso-font-kerning:1.0000pt;"><font face="宋体">控制器：反作用</font></span><span style="mso-spacerun:'yes';font-family:宋体;line-height:150%;font-size:12.0000pt;mso-font-kerning:1.0000pt;">&nbsp;</span><span style="mso-spacerun:'yes';font-family:Calibri;line-height:150%;font-size:12.0000pt;mso-font-kerning:1.0000pt;"><o:p></o:p></span></p></div>