热电厂输煤装置的智能传送控制系统外文翻译12页

1、 毕 业 设 计（论 文）外 文 文 献 译 文 及 原 文学 生： 芮 昱 学 号： 200506010123 院 （系）： 电气与信息工程学院 专 业： 电气工程及其自动化 指导教师： 李英春 2009 年 06月 10日热电厂输煤装置的智能传送控制系统作者: Makarand Joshi摘要：几乎在所有输煤装置（CHP）上都能看到传送带的身影。输煤装置有很多传送带。用于这些传送带的控制系统是非常重要的安全运行装置。传送带基本上是无输出显示的，但一旦配备了适当的控制系统，他们就能高产高效生产并成为安全的操作装置。电子智能传送带控制技术有益于复杂的输送任务。但是，在输煤装置的控制输送系统仍然

2、使用简单的开/关开关以及某些型号的高速开关。这些开关只在防护方面起到了有限的作用。这些传送带控制系统最大的问题是设备操作员和维修工程师要是解除不安全的工厂运行因素，那些将会迫使设备故障和中断供应煤锅炉，造成损失的因素。 本文重点论述输送控制系统的必须性，该系统将满足设备平稳，安全运行的需求。关键词：传动带，控制系统1简介：输煤装置的效率取决于输送系统的可用性和可靠性。如果传送带运作良好，这几乎是无形的输煤装置。一个单一的传送带可以以接近100 的可靠性运行，但随着传送带的数量增加，输送系统的可靠性就主要取决于它的控制系统。控制系统应能满足输煤装置运行的所有需要。 现有系统的目的是照顾连续运行中

3、由于低速而停机的传送带。他们还保证了自动运行的除尘系统。煤炭运输的称重也可由这个系统自动完成。但是，不合适的系统功能无法满足输煤装置的要求。这种情况下可以使用简单的继电器控制系统和旧式机械传感装置。为了满足要求，电子智能传送带控制系统要不断发展。这个系统将打破一切旧体制的制约，拥有额外的功能例如进给速度控制。2现有的控制系统： 现有的系统已经有像零速度传感，传送带位置遥感接收器等感应装置。它还可以方便的选择运行传送带，以避免控制系统手动运行模式。在一些输煤装置的设备有三个种选择。其中之一就是启动或停止装置的自动模式。在这种模式下选择流后每个传送带会连续运行。二是用人工方式使所有输煤装置启动或停

4、止。三是系统没有任何保护或联锁的运行。2.1工作原理：输送系统开始之前有必要先开始启动传送带，然后开始物料输送，即运行逻辑是从下游向上游。停止输送系统的运作方式输相反的，即从上游到下游。因此如有传送带停止时所有上游输送应停止自动是很必要的。现有的系统照顾到了这个逻辑。这就是所谓的输送带连续运行。如果由于任何问题使输送带的旋转变得缓慢甚至为零时有必要停止输送。这就是所谓的零速保护。现行制度照顾并停止传送带，并进一步阻止上游系统顺序。当有煤流时除尘系统应该运行。这是通过遥感简单的皮带下机械开关来实现的。测量煤流是通过使用称重传感器。该框图如图1给出了控制系统的概述。图1当皮带开关接触煤炭且电机运行

5、时除尘系统喷头将会打开。这两个没有任何的感应，以避免当传送带不旋转时采取喷洒，但皮带上的煤炭是接触皮带下面开关的真正原因。 2.2现有系统的反馈：该系统的主要的问题是必须保持不断的监视每条输送带的电流，因为传送槽可能被塞住或输送带被卡住。很多时候必须减少进给率通过调整反馈减少输送带的电流。当电流再次恢复正常时系统试图建立所需的进给速度，如果系统不能再次建立就要停止输送系统并把问题识别和标示出来。这个问题大多数发生在雨季当煤很潮湿的条件下。有时运行特别不能认定电流的增加将造成大量的煤溢出传送槽。这个趋势会中断锅炉的煤炭供应。感应速度可以使用简单的代理开关。当这些开关安装在尾部滚筒上时，有时可能由

6、于煤泄漏时而引起问题。代理交换机基本上是开/关开关配备计时器，他们是不太可靠的。一些输煤装置采用离心开关驱动传送带。当煤突然涌出时，这个开关在减小煤涌出的拉力功能上的不合适就会显现出来。该系统的主要的问题是，当输送电机保险丝被烧时，它将会停止输送机的旋转，但不会停止上游传送带的控制器感应电机运行控制供应，因为没有将电机继电器关闭。由于这些系统的逻辑会出错。系统的控制没有根据 1 去测量粉尘排放量和煤流的数量，没有为控制系统发挥任何作用。 3智能输送控制系统：控制系统将取代现有的系统，必须要克服所有旧系统的缺点。该系统，将建议使用测速传感器，称重传感器和电子芯片取代继电器。3.1工作原理： 皮带

7、速度是通过一个可连接到任何非驱动滑轮的测速发电机来衡量的。这个皮带运输机速度的测量是用于煤的称重。在新系统中测速是主要的部分，这有助于控制系统的顺利运行。这将判断非驱动滑轮的速度。产量将不断通过传送带电机和称重传感器（传送带称重）与目前的比较得出输出结果。这将控制进给率。转速表安装在非驱动皮带轮上令Et1 =给定电压， KT1 =常数， (t1) =非驱动滑轮的速度。得Et1 = KT1 . (t1). 1. 称重传感器安装在传送带下面 令Ec =给定电压，Kc =常数，W(c) =煤的瞬时重量。得Ec = Kc . W(c). 2. 进给速度的计算需要比较称重平衡桥（Wb）令Ect =输出电

8、压的比较值， Kct =常数，W(ct) =煤的进给速度得Ect = Kct . W(ct). 3.及Ect = Ec / Et1.令SR =参考信号，SE =错误信号，SF =反馈信号，SO =输出信号（反馈调速） SF = Ect 随着输出电压平衡桥衡反馈信号同时输出把值带入3中SF = Kct . W(ct). 4. 电流互感器Mc判断通过发动机的电流令Em =输出电压参考电机电流互感器McT.F. =传输功能，这取决于调节系统的类型比较器Cml比较电流互感器输出信号与称重平衡桥（Wb）的输出信号令Eml =比较器Cml的输出电压，Kml =常数，W(ml) =煤的每个电机进给速度得Em

9、l = Kml . W(ml). 5.和Eml = Ect / EmSml = Eml 由于输出电压比较器是一样的反馈信号把值带入5中Sml = Kml . W(ml). 6.进给速度决定好后，然后通过调整位置设定控制器。反馈调速器的速度是随着从称重平衡桥接收到的反馈改变的。在同一时间收到的反馈是进给率电机功率。由于电机功率进给率降低，反馈装置的速度也将降低，以保护系统。同时，它会通过报警提醒操作者。框图如图2将给予同样的概述。图 2皮带洒水装置也将从平衡器收到信号。作为流动的煤炭设立了无喷嘴上安装安全带的运作中所占的比例煤炭进给速度。通过测量粉尘排放量将产生反馈和采取纠正动作。见图3 。 令

10、SR1 =参考信号， SE1 =错误信号， SF1 =反馈信号， SO1 =输出信号（无喷嘴打开） 由4 可得SF1 = SF = Kct . W(ct) 7.用敏感光电式装置测量粉尘量。这个装置Md将会传送信号。令Emd =输出电压Md， Kmd =常数，W(md) =粉尘排放率。 得Emd = Kmd . W(md). 8.Smd = Emd 由于输出电压比较器和反馈信号大小是一样的。 把值带入8中 。 SF1 = Kmd . W(md). 9. 图 3这两个控制器将确保输送系统的运行非常顺利。框图如图4将清楚地表明这一系统。使用模拟到数字转换器可以很容易地将所有数据记录在计算机中。图 4

11、4结论：该系统易于安装。该系统具有更高的可靠性和保护性。该系统不需要任何复杂的传感器。现有的系统中所有的缺点将在该系统中被改正。参考文献：1 .科技论文“Failure of Dust Suppression Systems in Coal Handling Plants”，作者 Makarand Joshi，M-News Edition 19 of Plant Maintenance Resource Center Industrial Maintenance Portal /articles/dust_suppression.pdfAn I

12、ntelligent Conveyor Control System For Coal Handling Plant Of Thermal Power PlantBy: Makarand JoshiAbstract: Conveyors are seen on virtually all in the Coal Handling Plant (CHP). CHP are having number of conveyors. The control systems used for these conveyors are important for operating safe plant.

13、Basically conveyors are dumb, but once equipped with proper control system they yield efficient and safe plant operation. Electronic intelligent conveyor control technology is useful for complex conveying tasks. But in CHP for control of conveyer system still use of simple on/off switches and some f

14、orms of speed switches are used. These switches are only play roll of protection up to some limit. These conveyors control system are the biggest problem for the plant operator and maintenance engineer, being the cause of unsafe plant operation, which forced to plant breakdowns and interrupt coal su

15、pply to boilers results in loss of generation. This paper has been focused on the required conveyor control system, which will fulfill requirements smooth, and safe plant operation.Key words: conveyor, control systerm1 Introduction:The efficiency of CHP is depending upon availability and reliability

16、 of conveyor system. If a conveyor system is working well, it is almost invisible to the CHP. A single conveyor can run at close to 100% reliability, but as the number of conveyor increases, the reliability of the conveyor system is mostly depend upon its control system. The control system should be

17、 capable to fulfill all the need of CHP operation. The existing systems are designed to take care of only conveyor stoppage due to conveyor zero speed and sequential operation. They also ensured of auto operation of dust spray system. The measurement of coal transported is done automatically by this

18、 system. But improper system feature could not fulfill CHP operation requirement. At maximum places the simple relay control system with old style mechanical sensing devices are used. For fulfilling the requirement Electronic intelligent conveyor control system has developed. This system will take a

19、ll the constraints of old system and also having additional feature like feed rate control. 2 Existing Control System:The existing system has sensing device like zero speed sensing, receiving conveyor position sensing. It has also facility for selection to operate conveyor avoiding control system i.

20、e. manual run mod. In some CHP there is facility of three type of selection. One is for start or stop plant with auto mode. In this mod each conveyor will operate sequentially after selecting the stream. Second which is in all CHP for start or stop of plant with manual mode. Third is operating the s

21、ystem without any protection or interlock. 2.1 Operating Principle:Before starting conveyor system it is necessary to start first receiving conveyor and then start feeding conveyor i.e. operating logic is from down stream to upstream. For stopping of conveyor system the operation will be opposite i.

22、e. from upstream to down stream. So it is necessary if any conveyor is stopped in the system all the upstream conveyor should stop automatically. The existing system takes care of this logic. This is known as conveyor sequential operation. If due to any problem the rotation of conveyor becomes slow

23、or towards zero its necessary to stop the conveyor. This is known as zero speed protection. Existing system takes care of it and stops the conveyor and further stop the upstream system sequentially. The dust suppression system should be operating when there is coal flow. This is done by sensing via

24、simple mechanical under belt switch. The measurement of coal flow is done by using load cell. The block diagram of shown in figure no 1 will give idea about control system. Figure No 1For dust suppression system the spray header will be on when the contact of under belt switch is true and motor is i

25、n on. This two no of sensing is taken to avoid spraying when conveyor is not rotating but contact of under belt switch is true due to coal is laying on belt. 2.2 Draw Back Of Existing System:The main problem of this system is required to keep continuous watch on each conveyor current because of chok

26、ing of transfer chute or jamming of conveyor. Many times it is required to reduce the feeding rate by adjusting feeder to reduce the current of conveyor. When current comes to normal again it is tried to establish the required feed rate, if it is not again establish by stopping the conveyor system t

27、he problem is identify and attended. This problem majorly occurs in rainy season when coal is in wet condition. Some times operate specially cannot identify the increase current it will cause heavy coal spillage from transfer chute. This will tend to interruption of coal supply to boiler. For sensin

28、g of speed simple proxy switches are used. These switches many times causes problem due to coal spillage when they are mounted on tail end pulley. As proxy switches are basically on/off switches equipped with timer, they are less reliable. Some of CHP used centrifugal switch, which is driven by the

29、conveyor. The main problem of this witch occurs when the spring functioning is improper i.e. reduction of spring tension. The major problem of this system when the conveyor motor power fuses blown off, it will stop the rotation of conveyor but will not stop the upstream conveyors as controller sense

30、 motor is running because the control supply does not pick up motor off relay. Because of this the logic of system fails. The control of the system is not depending 1 on the quantity of dust emission and measurement of coal flow is not play any roll for controlling the system. 3 An Intelligent Conve

31、yor Control System:The control system, which will replace the existing system, must overcome all the drawbacks of old system. The system, which is suggested, will work by only using tachometer, load cell and electronic cards in place of relays. 3.1 Operating Principle:Belt speed is measured by a tac

32、ho-generator, which may be attached to any non-drive pulley. This speed measurement is used for weighment of coal, which is with conveyor. In new system tachometer is main part, which helps for controlling system smoothly. This will sense non-drive pulley speed. The output of this will be compared c

33、ontinuously with current drawn by conveyor motor and load cell （conveyor weighbridge output. This will govern the feeder rate. For tachometer, which is mounted on non- drive pulley Let Et1 = generated voltage, KT1 = the constant, (t1) = the speed of non-drive pulley. Then Et1 = KT1 . (t1). 1.For loa

34、d cell which is mounted below conveyor Let Ec = generated voltage, Kc = the constant, W(c) = the weight of coal at that time. Then Ec = Kc . W(c). 2. For calculating feed rate it is required to compare by comparator of weighbridge (Wb) Let Ect = out put voltage of comparator, Kct = the constant, W(c

35、t) = the feed rate of coal Then Ect = Kct . W(ct). 3. And Ect = Ec / Et1. Let SR = Reference signal, SE = Error signal, SF = Feed back signal, SO = Out put signal (for feeder speed adjustment), SF = Ect As the out put voltage of weighbridge is same as feed back signal. Putting value in 3. SF = Kct .

36、 W(ct). 4. The current transformer Mc senses the current drawn by motor. Let Em = equivalent output voltage with reference to motor current transformer Mc T.F. = Transfer function, it depends on the type of regulating system. The comparator Cml compare current transformer output signal with out put

37、signal of comparator of weighbridge (Wb) Let Eml = out put voltage of comparator Cml, Kml = the constant, W(ml) = the feed rate of coal per motor power Then Eml = Kml . W(ml). 5. And Eml = Ect / Em Sml = Eml As the out put voltage of comparator is same as feed back signal. Putting value in 5. Sml =

38、Kml . W(ml). 6. The feed rate is to be decided and then it is to be set for controller by adjusting pot position. The speed of feeder is change as per feedback received from weighbridge. Then at same time feedback is received for feed rate per motor power. As the feed rate per motor power is reduced

39、 the speed of feeder will be reduced and will protect the system. At the same time it will alert the operator by blowing alarm. The block diagram shown in figure no 2 will give idea about the same. Figure No 2For spraying the water on the belt the signal will receive from the weighbridge. As flow of coal is established the no of nozzles mounted on belt will operate in proportion to the coal feed rate. The feedback will take by measuring dust emissio