锅炉汽包水位的自动控制 毕业论文外文翻译.doc

英文原文文献automatic control of the level of boiler bubblewang zhi(luoyang petrochemical engineering co., luo yang 471003, china)abstract:the paper introduced the dynamic characteristics of the level of boiler bubble. the characteristics of automatic control schemes with one variable or two variables or three variables were discussed, as well as some problems concerned in engi-neering. the automatic control scheme of boiler bubble with three variables was recommended specially.keywords: the level of boiler bubble; dynamic characteristics; automatic control schemes; one variable; two variables; three variables.introduction boiler drum water level is the major indicators, is a very heavy to the accused variables to maintain the water level in a certain range is to ensure that the boiler the first condition for the entire operation, it is because: (1) high water level will be affect steam package separator, saturated with water opour too much water, superheated steam temperature in sharp decline. the superheated steam turbine as a driving force, it would turbine blade damaged, affecting the safety and economy. (2) water bit too low, the less water in the drum, and when the load is higher, as the water vaporization of speed, drum changes in the water level has also added speed. fast, if not promptly adjust, it will cause the drum all vaporization of the water, resulting in burning furnace tube, or even cause an explosion. therefore, the boiler drum water level must be strict canadian control. 2 several boiler water level control program.2.1-impulse control system impulse-control system (the term refers to the impulse is variable, namely single impulse drum level) are in direct control of drum water level control valve (figure 4 below), the drum is the most simple level control of the most basic a form is a typical value for single-loop control system. the system guitar simple configuration to achieve low investment and easy for small low-pressure boiler. boiler steam because this load is relatively stable, and the relative volume drum the requirements of users of steam often not very strict, if the control system some alarm interlock devices, but also to meet production requirements. figure 4 single impulse control system block diagram stay in a relatively short time, large load changes, we can not single. figure 4 single impulse control system block impulse level control system. this is because: (1) when the load changes 21.2003 in the first eight chemical technology market false level will reverse regulator dislocation movement, the increase of load - close down small water control valve, when the dust has settled flash evaporation, the water level will decline, a sharp fluctuations in the dynamic regulation poor quality. (2) changes from the decline in the water level to load changes and to control valve movements. long lag time, if the water level in a small time constant process, the error bound very significant. (3) water supply system disturbances, as changes to the pump pressure, in water immediately, and that an accurate assessment of the water level so that when the control valve dynamic for the same lack of a timely manner.2.2 pairs of impulse control system drum in the water level control, the disturbance is the most important variable load . then the introduction of steam flow to correction, it can not only compensation false solution caused by operation, and the water control valve movements timely, his constitutes a double impulse control systems. in essence, the doubly-impulse control system is a system of feed-forward (steam flow fts) plus single-loop feedback control the system of composite control system. adder output = pc s ps + initial deviation. if the high-pressure steam supply steam turbine compressor, for the protection of equipment, to use gas valve to open (fc) valve, when the increased steam flow, water supply also to a corresponding increase in traffic, then use a gas valve, the output should be additive which is s, should take. if steam as a heat source in the production process, for the protection of equipment. to use gas valve to the commissioner (fo) valve, when the increased steam flow, water supply also to a corresponding increase in traffic, then use gas valve clearance, the output should be additive reduce that s should take dashes. in order to balance these two requirements, with the election to secure his position device (fl) .to the valve, the valve that stops accidents in the state in situ. initial deviation settings the objectives are: normal load, the regulator and processing implements output can have a relatively moderate value, the best in the normal load with the initial error (steam flow fts) s ps of exactly off figure 5 pairs of impulse control system block diagram figure 5 pairs of impulse control system block diagram 2.3 three impulse control program feed forward (steam flow) plus feedback (level, water flow) control system .the system can be seen as a comprehensive three-volume signal as a variable charged single-loop control system, put into operation and setting single-loop control systems, however, if the system parameters can not be set up to ensure that the material balance, variable load and when the water level will be more than poor. on the coefficient s w and the role and settings: (1) to ensure that the material balance that is, w = a d under the conditions of steam flow signal s ps water flow and signal w /pw should be the same, based on this principle, identify and w /s ratio. (2) to determine the role of strength feed forward from (1) material balance know w /s and the ratio should be the size determine the basis of the process, the greater its s feed forward role as strong, a disturbance at present, the control valve opening of the changes also greater. figure 6 three-block diagram of control program . figure 6 three-block diagram of control program 2.3.1 three impulse control program - steam flow feed forward - cascade water flow control system and program similar program, but only the adder position from regulation the former regulator moved after. the program regardless of w /s and how to set up, when the load changes, the level can be maintained without poor, in order to improve the load disturbance 2.3.2 three impulse control program - steam flow feed forward - liquid the regulation of quality. figure 7 three-block diagram of control program adder output = pc s ps wpw fccu capacity steam boiler drum and ms guan used gas (fo) - 22 chemical technology market 2003 section 8 of the valve of the capital, when the increased steam flow, the water has to flow accordingly increased gas use this valve clearance, boosting the output should be reduced, which should sad mission minus. when the water flow increases, then choose gas valve clearance, adder output should be increased, for instance, is w,. when a heightened level (regulator positive role), corresponding to water flow also decreased at this time selection commissioner gas valve, boosting the output should be increased, for instance, is that of pc. figure 7 three-block diagram of control program 4 conclusion this method successfully developed a new compound ammonium bicarbonate anti-caking agent can crystal size increased ammonium bicarbonate, and has a good anti-caking performance, stability good. this product has achieved industrial production was more than ammonium bicarbonate health industrial production plant application, the use of a ton of ammonium bicarbonate 0.45 0.5 kg, lower production costs, good effect. received date :2003-03-24 about the author: chen yu long (1964 -) m, associate professor, master, engaged in physical chemistry teaching and fine chemical development. references 1 chen yu long. surfactant inorganic anti-caking agent in the application of daily chemical workers industry, 2002,32 (4) :48-49 2 song xiang, sun bao ping, ru-ling were. anti-caking agent and progress in research methods, chemicals progress, 2001, (6) :50-52 (then no. 23) 3 jiang wei sun, jin-shou yu. process control engineering. beijing: hydrocarbon processing press. 4 jin-hui. process control. beijing: tsinghua university press. 5 lu man. petroleum and chemical control design manual. beijing: the chemical industry she version. 19.2003 in the first eight chemical technology market附录b对应的中文翻译锅炉汽包水位的自动控制王智(洛阳石油化工程公司仪电室,河南洛阳471003)摘要:本文介绍了锅炉汽包水位的动态特性,单冲量、双冲量、三冲量控制方案的特点及工程中需注意的问题,着重介绍了汽包三冲量控制方案。关键词:汽包水位;动态特性;控制方案;单冲量;双冲量;三冲量中图分类号:tq054文献标识码:b文章编号:1009-4725(2003)08-0020-04引言汽包水位是锅炉运行的主要指标,是一个非常重要的被控变量,维持水位在一定范围内是保证锅炉安全运行的首要条件,这是因为:(1)水位过高会影响汽包内汽水分离,饱和水蒸过时过热蒸汽温度急剧下降。该过热蒸汽作为汽轮机动力的话,将会损坏汽轮机叶片,影响运行的安全性与经济性。(2)水低,说明汽包内的水量较少,而当负荷很大时,水的汽化速度加快,则汽包内的水位变化速度亦随之加快,如不及时调节,就会使汽包内的水全部汽化,导致炉管烧坏,甚至引起爆炸。因此,锅炉汽包水位必须严控制。2.1单冲量控制系统单冲量控制系统(冲量一词指的是变量,单冲量即汽包液位)是采用汽包液位直接控制给水调节阀(如图4所示),它是汽包液位自动控制中最简单 最基本的一种形式,是典型的单回路定值控制系统。该系统结构简单 投资少 容易实现,用于小型 低压锅炉。因为这种锅炉的蒸汽负荷比较稳定,汽包的相对容积大,用户对蒸汽的要求往往不十分严格,该控制系统若再配上一些报警联锁装置,也可以满足生产要求。在停留时间较短,负荷变化较大时,就不能采用单冲量液位控制系统。这是因为:(1)负荷变化时产生的212003年第8期化工科技市场“虚假液位”将使调节器反向错位动作,负荷增大时反而关小给水调节阀,当闪急汽化平息下来时,会使水位严重下降,产生剧烈波动,调节的动态品质很差。(2)负荷变化时,从负荷变化到水位下降再到调节阀动作,滞后时间太长,如果水位过程时间常数很小,偏差必然很显著。(3)给水系统扰动时,例如给水泵压力变化,进水量立即变化,而到水位产生偏差时才使调节阀动作,同样不够及时。2.2双冲量控制系统在汽包的水位控制中,最主要的扰动是负荷的变化,那么引入蒸汽流量来校正,不仅可以补偿“虚位”所引起的误动作,而且使给水调节阀的动作及时,这就构成了双冲量控制系统。从本质上看,双冲量控制系统是一个前馈(蒸汽流量fts)加单回路反馈控制系统构成的复合控制系统。加法器的输出=pcs ps+初始偏差。如果高压蒸汽供给蒸汽透平压缩机,为保护设备,给水阀宜选用气开(f.c)阀,当蒸汽流量加大时,给水流量亦要相应增加,此时选用气开阀,加法器的输出应增加,即s应该取正号。如果蒸汽作为工艺生产中的热源时,为保护设备,给水阀宜选用气关(f.o)阀,当蒸汽流量加大时,给流量亦要相应增加,此时选用气关阀,加法器的输出减小,即s应该取减号。为了兼顾上述两种要求,宜选带保位装置(f.l)的水阀,即事故状态该阀停在原位。初始偏差设置的目的是:正常负荷下,调节器和加法器的输出都能有一个比较适中的数值,最好在正常负荷下初始偏差与前馈(蒸汽流量fts)s ps项恰好抵消。 图4单冲量控制系统方框图