A Newly Proposed Temperature Control Methods of Fuel Gas Shuttle Kiln

Ⅴol.17No.3Journal of Wuhan University of Technology- Mater. Sci. EdSept. 2002A Newly Proposed Temperature Control Methods of FuelGas Shuttle KilnLIU Yan-chun WEI MinWuhan University of TechnologyReceived ' Sept 152001Abstract: A program control was applied in the fuel gas shuttle hiln ,and its principle and disaduantgewere analyzed. An aduanced set point control method in which the change rate of temperature is the controlledcariable ,is also described and the new control system makes the control precision of temperature improvedey words: program control i set point control; control precision1 Introductionsection above 1000%C ).So the sontrol of the temperatureAfter the fuel gas shuttle kiln was introduced in Chity 1. The shuttle kiIn also hadelay time-varyinese ceramics in 1980 s, the advanced technique is de-nd multi-interference like the car tunnel kiln its controlveloping very fast because of its good characteristics such precision has not ideal by now 2so how to enhance theas low investment, fast effect, good adaptability shortcontrol precision of the temperature in the shuttle kiln is acompletive cycle and high efficiency. In the process ofvaluable research probiemchange rate in the kiln is required to make sure the prod2 Newly Control Designr, as shown in FigWe can found why the control precision is not goodfrom above that is the controlled temperature changesstepped not even and gentle in other words the changerate of temperature(R )is variable in the temperature-upsection and drop section. The set point control in which Ris the controlled variable could overcome above disadvantage effectively. The set valt300C-normal temperaturerFig 1 Tthe temperature change curve in the shuttle kilnIt spends 24 hours in firing one kiln of product. In where r is positive in the temperature -up section and rethe first hours the temperature rises from normal to verses in the drop section. Holding R constant in the sec1300C according to certain slope then the temperature tions is advantageous to avoiding the intentional interferwill keep 8 hours finally it downs to normal temperature ence. Then the change of controlled temperature will beon the same slope. The control precision of temperature issubtle and accurate on the ideal curve relativelrequired to 5C. It has proved that the temperatureIn addition ,the set point control in which the temhange in the shuttle kiln makes great effects on the qual- perature is the controlledty of the products8hours of temperature-hold section. So there are two typesand For example, the temperature must increases even of set point control systems in the whole control processand gentle. In the low-temperature section below actually the temperature changes in the one and not in300C) or else the product will have the mark of water the中国煤化工 s followingand cracks In the mid-section( 400-800 C)if the tem-CNMH Gof the constant-temperaperature rises too fast or too slow it will lead to color dif- ture set point control system is known very well rand theference and air bubble , the same in the high-temperature varying-temperature control system have two new sectionstime function and the calculation of r", which is ilLIU Yan-chu( XUEE ): Born in 1944 :Assoc Prof. School of lustrated in Fig. 2. When the deviation( equates to theAutomation两声据 rersity of Technology wuhan430070hinaoutput of the controller ) is 0 ,the" time function"sectionVol 17 No. 3LIU Yan-chun et al : A Newly Proposed Temperature Control Methods ofTime functionOn condition thatfounded we can first get the step response curve then一mDa+mhdhget the controlled object characteristics of which thecnange rate is output variable. The principle block diiThe calculation of RHA/DDetect transmittergram is shown in Fig. 6. Ax is the stepped input signalFig. 2 The block diagram of the varying-temperature set pointTime function texports a signal that varied with time( t ). Then the sig-48-DAALControl valveh-Thee shuttle killI acts on the control valve ,to make the temperature inRecorder- The callculation of RfAD DEtect transmthe shuttle kiln change on the constant rate Through thecalculation of R"section every sampled value of the tenperature exports results as the measured value of the con- Fig 4 The block diagram of the measurement of the ojbecttrol system. Although the controlled objects of two systemscharacteristicsare the same their characteristic parameters(K, T, t) 3. 3 The calculation of Rare different and should be measured separately becauseAfter sampling every time we calculater R bythe controlled variable of one system is temperature( T)T(k)-7(h-1)nd which of the other is the change rate of temperature(R)where T(K)and T(K-1) are two adjacent samplinThe countrol and regulation process of two controllers values and 0 is the sampling period. When T( K-1)are separatdeviates from the ideal value, R will follow its desired vaue(r)as close as possible after self-regulation. But the3 Implementationtemperature change curve is just parallel to the ideal skewline and the deviation is inevitable. So we sophisticate the3.1 The foundation of the time function modelequation asThe program control system in which the set vak)-(o)stepped changes is helpful to setting up time functionwhere 7(0) is the intial temperature and tk is the sum oflen The change curves of the set value and controlled the time for k times samplingerature in the temperature-up section are shown inFig 3 , where A is the ideal temperature change curve, B4 ConclusionI set value curve and C is the actualperature. It is supposed that A and C intersect in 1/2AtThrough analysis above ,if we adopt Set point controlevery 1At and then the time coordinates of the intersec- system replace of normal program control system , and dotions are t;=( i= 1,2,3). On the stability state , wethe testing of the relative model well, we will found thatrepeat measure the signal of control valve C i=1, 2,3 the control precision of the temperature in the shuttle kilnbn t; hen get a corresponding relation(t)hiis improved greatly. Compare with other advanced controlthe approximate"time function"model of the set point technologies, the technique has good application prospectcontrol systembecause of less spent and good realizabilityReferences1 Wang Hui and Zeng Lingke. The Control of Ceramic Kilns andYH中国煤化工ramics 2000, 1 33el gas shuttle kiln. ShCNMHG3 Zhu Linzhang. Process Control Systems and Design , Beijing Pub-shing House of Machine Industry 1996: 194 Dong Jingxin. The Foundation of Control Engineering. BeijingFig 3 The actual temperature change carveublishing House of Tsinghua University 1992:1093.2万数据 asurement of the object characteris-