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<p class="MsoNormal" style="MARGIN: 0cm 0cm 0pt;"><span lang="EN-US"><font face="Times New Roman">14</font></span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">.与定压运行相比,机组采用变压运行主要有和优点?</span></p><p class="MsoNormal" style="MARGIN: 0cm 0cm 0pt;"><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">答:(</span><span lang="EN-US"><font face="Times New Roman">1</font></span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">)机组负荷变动时,可以减少高温部件的温度变化,从而减少汽缸和转子的热应力、热变形,提高部件的使用寿命,</span></p><p class="MsoNormal" style="MARGIN: 0cm 0cm 0pt;"><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">(</span><span lang="EN-US"><font face="Times New Roman">2</font></span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">)低负荷能保持较高的热效率,由于变压运行时调速汽门全开,在低负荷时节流损失很少,所以与同一条件的定压运行相比较热耗较少。</span></p><p class="MsoNormal" style="MARGIN: 0cm 0cm 0pt;"><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">(</span><span lang="EN-US"><font face="Times New Roman">3</font></span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">)给水泵功耗减少,当机组负荷减少时,给水流量和压力也随之减少,因此,给水泵的消耗功率也随之减少。</span></p><p class="MsoNormal" style="MARGIN: 0cm 0cm 0pt;"><span lang="EN-US"><font face="Times New Roman">15</font></span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">.锅炉启动速度是如何规定的?为什么升压速度不能过快?</span></p><p class="MsoNormal" style="MARGIN: 0cm 0cm 0pt;"><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">答:锅炉启动初期升压应缓慢,一般并网前升压速度不大于</span><span lang="EN-US"><font face="Times New Roman">0.7MPa/min</font></span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">,并网后不大于</span><span lang="EN-US"><font face="Times New Roman">0.13 MPa/min(</font></span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">指引进型国产</span><span lang="EN-US"><font face="Times New Roman">300MW</font></span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">机组</span><span lang="EN-US"><font face="Times New Roman">)</font></span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">。</span></p><p class="MsoNormal" style="MARGIN: 0cm 0cm 0pt;"><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">在升压初期,由于只有少数燃烧器投入运行,燃烧较弱,炉膛火焰充满程度较差,对蒸发受热面的加热不均匀程度较大;另一方面由于受热面和炉墙的温度很低,因此燃料燃烧放出的热量中,用于使炉水汽化的热量并不多,压力越低,汽化潜热越大,故蒸发面产生的蒸汽量不多,水循环未正常建立,不能从内部来促使受热面加热均匀。这样,就容易使蒸发设备,尤其是汽包产生较大的热应力,所以,升压的开始阶段,温升速度应较慢。</span></p><p class="MsoNormal" style="MARGIN: 0cm 0cm 0pt;"><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">此外,根据水和蒸汽的饱和温度与压力之间的变化可知,压力越高,饱和温度随压力而变化的数值小;压力越低,饱和温度有较大的变化,因而造成温差过大使热应力过大。所以,为避免这种情况,升压的持续时间就应长。</span></p><p class="MsoNormal" style="MARGIN: 0cm 0cm 0pt;"><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">在升压的后阶段,虽然汽包上下壁、内外壁温差已经大为减小,升压速度可比低压阶段快些,但由于工作压力的升高而产生的机械应力较大,因此后阶段的升压速度也不要超过规程规定的速度。</span></p><p class="MsoNormal" style="MARGIN: 0cm 0cm 0pt;"><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">由以上可知,在锅炉升压过程中,升压速度过快,将影响汽包和各部件的安全,因此升压速度不能太快。</span></p> |
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