Design and Development of Intelligent Control System for Gas Collector Pressure of Coke Oven in Coal Chemical Industry

Transcription

1 A pblication of CHEMICAL ENGINEERING TRANSACTIONS VOL. 59, 7 Gest Editors: Zho Yang, Jnjie Ba, Jing Pan Copyright 7, AIDIC Servizi S.r.l. ISBN ; ISSN 8-96 The Italian Association of Chemical Engineering Online at DOI:./CET759 Design and Development of Intelligent Control System for Gas Collector Pressre of Coke Oven in Coal Chemical Indstry Kn Li, Jing Dong School of Information Engineering, Qjing Normal University, Qjing 655, China qjnlikn@6.com Dring the coking process in coal chemical indstry, the stability of gas collector pressre is an important garantee for the normal prodction of coke oven. This paper combines the adaptive fzzy control algorithm and the fzzy decopling rle to control the gas collector pressre, and coordinates the entire system throgh the establishment of pre-header sction spervisory control. The specific implementation method and rnning crve of actal intelligent control systems are taken as reference. Finally, it is proved that the intelligent control system for gas collector pressre of coke oven in coal chemical indstry has effectively reglated gas collector pressre, stabilized the entire prodction system, and met the reqirements on prodction process.. Introdction The stability of gas collector pressre is the main indicator of coking prodction of coke oven in coal chemical indstry (Kmar and Singh, 5; Yi et al., 5; Hasson et al., 97). The coke oven and blower control system is actally a mltivariable copling system for the gas collectors on the psher side and coke side are connected into a whole (Wei et al., ). Owing to the interference between the control loops, serios oscillation overshoots, complex conditions, as well as large and fast pressre flctations, it is difficlt to achieve effective reglation by conventional method, posing a severe impediment to the normal prodction process of coke oven in coal chemical indstry (Wang, ). In light of the above, this paper combines the adaptive fzzy control algorithm and the fzzy decopling rle to control the gas collector pressre, and coordinates the entire system throgh the establishment of pre-header sction spervisory control.. Analysis of gas collector control object Prior to the design of the control system for gas collector pressre of coke oven in coal coking indstry, it is necessary to nderstand the operation condition and copling sitation of gas collector pressre. Among the inflencing factors of gas collector pressre, some bring abot constant interferences, and some case plse-type interferences; the intensity of interference varies from factor to factor (Tan, ). It is very difficlt to bild a precise mathematical model for gas collector pressre control system as the paralleled coke ovens are negatively copled, the coke oven and blower are positively copled, and the intra-grop copling relationship differs from the inter-grop copling relationship (Fang, 6; Zhang, 5). For the sake of simplicity, the copling relationship between coke ovens is temporarily ignored, and only one chemical coke oven is taken into accont. The object model is shown in Figre. Figre : Simplified model strctre (Q -Gas generation; Q -Blower gas qantity; P -Gas collector pressre; P -Blower sction) Please cite this article as: Kn Li, Jing Dong, 7, Design and development of intelligent control system for gas collector pressre of coke oven in coal chemical indstry, Chemical Engineering Transactions, 59, -6 DOI:./CET759

2 The dynamic eqilibrim eqations of the air pressre system are established according to the material balance: dp P - P C = ΔQ - dt R dp P - P C = dt R - ΔQ dp T dt + P = KΔQ + P () () () dp T + P = KΔQ + P () dt Where T =RC, T =RC and K=R After the Laplace transformation and finishing: P (S) + KQ(S) P (S) = T S + P (S) + KQ (S) P (S) = T S + (5) (6) A block diagram of the object featres is created according to the above formlas (Figre ). Figre : Block diagram of object As shown in Figre, when the gas generation Q flctates, the gas collector pressre P responds in a timely manner. The opening of the btterfly valve at the otlet of the gas collector is adjsted to alter K, and ths overcome the distrbance of Q. When the blower gas qantity Q changes, the blower sction P also responds in a timely manner. However, the response is slower and P deviates from the set vale nder the positive feedback. In particlar, the responses from P and P are not synchronized, creating a lasting time difference between the two changing processes. Hence, the copling between the gas collector pressre and the blower sction is very prononced.. Adaptive fzzy control design of gas collector pressre The adaptive fzzy control design of gas collector pressre of coke oven in coal chemical indstry is divided into three aspects: fzzy circit control design, fzzy decopling control design, header sction spervision and control design.. Fzzy control circit design for gas collector pressre The basic principle of fzzy control is to imitate hman reasoning and decision-making, replace the manal operation with hman-simlated control method, fzzily otpt jdgment converted from accrate inpts, and transform the jdgment into accrate control otpt. In order to design a fzzy control system, the designer has to condct fzzy operation, establish database and rle base, perform fzzy reasoning, and set p the qery table. This paper improves the traditional off-line design, and achieves on-line reasoning, optimization, and adjstment based on the qery table. The plan for adaptive fzzy reasoning and optimization design are displayed in Figre.

3 Figre : Design of adaptive fzzy reasoning and optimization On-line adjstment of qantization factors and scale factors: For a complex controlled process, it is difficlt to achieve the desired control effect with a fixed grop of qantization factors and scale factors. Therefore, the control characteristics in different phases of the control process are adjsted with the qantization factors and scale factors of the self-tning fzzy controller, aiming to realize good control effect for the complex process. Weight adjstment of error and error rate: For the gas collector pressre of the system, the adjstment factor is assigned different vales in different phases of the control process becase weights of error and error rate have to meet different reqirements in different states. In this way, the control rles are more flexible, the adjstable range is enlarged, and the different reqirements on the adjstment factor are satisfied in different states. Modification of fzzy rles: Since the control error of the system is the most direct and effective indicator to evalate the performance of the controller, the self-adjstment of the fzzy control rle abides by the following philosophy: estimate the correction vale of the control qantity according to the system error, and modify the fzzy control rles with the correction vale of the control qantity. Direct empirical control of large error: For large error, the reference error change direction is directly controlled by the valve position. The strategy has many advantages. For instance, the one step adjstment of valve position can qickly downsize the pressre error into a small error range, and facilitate frther precise control.. Intra-grop and inter-grop fzzy decopling control plans for gas collectors Dring the coking process of coke oven in coal chemical indstry, the two gas collectors in a grop are arranged in parallel and connected to a header, and the headers of two neighboring grops rn parallel to each other and converge before extending otside of the system. The arrangement signifies the negative relationship in each grop and between the grops, raising the need for decopling... Intra-grop decopling For the gas collector pressre circit of each coke oven in coal chemical indstry, any pressre flctation will be reflected in its loop adjstment increment (variation in btterfly valve opening). Hence, the control increments U and U of the two control circits are taken as the inpts and the corrected vales of the control increments V and V are taken as the otpts for the intra-grop decopling rle. According to the characteristics of the coke oven process, the athor sorts ot the empirical rles in Table, and, on this basis, obtains the correction table for intra-grop decopling. Table actally corresponds to two tables: one corresponds to the correction qantity V of U, and the other to the correction qantity V of U. The level variables of the langage variables U, U, V and V are set as,, v and v. According to the rles in the table, the correction qantity rles are simplified as: v = f (, ) v = f (, ) (7) (8)

4 Finally, the btterfly valve control qantity is = +v and = +v after the intra-grop decopling compensation. Table : Decopling rles U U NB NS PS PB NB U = U + V NB V NB V NS U = U + V NB V NS V NS NS V NS V NS V NB V NS V NS PS V NS V PB PB V PB V PB V NS V NS V PB.. Inter-grop decopling The inter-grop decopling refers to the secondary correction of the control increment of each gas collector btterfly valve based on the inter-grop pressre flctations and btterfly valve opening so as to achieve pressre balance in each coke oven. After the intra-grop balance correction, the langage variables U, U, U and U of gas collector pressre control and adjstment for each coke oven in the grop are valed as: U UZ = + U (9) UZ U + U = The variables are sed as the inpts of the inter-grop decopling control rles. Sppose the inter-grop decopling rle otpt W (consisting of two components W and W ) is the inter-grop decopling correction qantity for the control increment. The correction table of intra-grop decopling rles is obtained based on the rles of thmb, and the table of correction qantity rles for inter-grop decopling is acqired in the same manner with that of intra-grop decopling: w = g(z,z ) () () w = g (z,z ) () Finally, the actal btterfly valve control qantity in the gas collector of each coke oven is as follows after the intra- and inter-grop decopling and correction: + v + v + v + v () () (5) (6). Pre-header sction spervisory rle control plan The rle control method is adopted for the reglation of the header sction pressre has a great impact on gas collector pressre. The main control principle is to determine the crrent opening of each gas collector control valve, and to determine the adjstment of btterfly valve opening on the header based on the opening of each header and the different combinations of the crrent pressres. Some of the control rles for pre-header sction are listed below. If jpg_flag=+ and jpg_flag=+ and jpg_flag=+ and jpg_flag=+; Then =-PcL If jpg_flag=+ and jpg_flag=+ and jpg_flag=+ and jpg_flag=+; Then =-PcM If jpg_flag=+ and jpg_flag=+ and jpg_flag=+ and jpg_flag=+; Then =-PcS

5 If jpg_flag=- and jpg_flag=- and jpg_flag=- and jpg_flag=-; Then =PcL The specific vales of PcL, PcM and PcS shold be properly adjsted in actal control. In this research, the system takes times the gas collector control cycle, and adopts the header control algorithm. This avoids the freqent adjstment of the header, and makes fll se of the copling self-adjstment law.. Realization of intelligent control system for gas collector pressre of coke oven in coal chemical indstry As shown in Figre, the system is composed of three parts: indstrial control microcompter system, presignal reglation part and control panel. The system mst have the following fnctions: monitoring, closedloop adjstment, display and keyboard operation. 5 Figre : System strctre diagram Since the operation of the system, the control indices have reached the designed vales, and the pressre flctation has been controlled within ±Pa of the set vale. The commissioning of the system stabilizes the gas collector pressre of coke oven in coal chemical indstry, redces gas dispersion, and improves the oven top operation environment. More importantly, the system helps prevent the oven from being damaged by the leak of smoke and fire nder high pressre and the backward flow of low-pressre air. Sffice it to say that the proposed system stabilizes the coke oven operation, and meets the prodction process reqirements on coke oven in coal chemical indstry. Figre 5 presents the crve of gas collector pressre nder large-distrbance. It can be seen from the figre that, in the case of large distrbances like coke pshing and coal loading, the gas collector pressre ndergoes a very prononced flctation. The fzzy control can qickly sppress the oscillation of gas collector pressre nder the distrbances and stabilize the pressre within the reqired range of 55±Pa.

6 6 Figre 5: The crve of gas collector pressre nder large-distrbance 5. Conclsion The proposed control system achieves stable control of gas collector pressre of coke oven in coal chemical indstry with the aid of the adaptive fzzy control. The weights are corrected and adjsted on-line dring the operation of the system, aiming at optimizing fzzy logic operation and adjsting the fzzy control rles. Dring the inter-grop decopling, frther corrections are made based on intra-grop decopling to strike a balance of the pressre between the two grops. The pre-header sction is sbjected to rle control and gradal adjstment methods. In order to make p for the effect of positive copling, the adjstments are made when the valve of single gas collector reaches the limit position or when the pressre flctates greatly. The operation test demonstrates that the system satisfies the prodction process reqirements by stabilizing the gas collector pressre, lowering the gas dispersion, and conterpoising the coking operation of coke oven in coal chemical indstry. Reference Aziz M., Oda T., Kashiwagi T., 5, Clean hydrogen prodction from low rank coal: novel integration of drying, gasification, chemical looping, and hydrogenation. Chemical Engineering Transactions, 5, Fang C., Li Y., Ka S., Hong L., Lee C., 6, A new lmi-based approach to relaxed qadratic stabilization of t-s fzzy control systems. IEEE Transactions on Fzzy Systems, (), DOI:.9/tfzz Hasson V., Pressler D., Klimek J., Von Bergmann H.M., 97, Transverse doble discharge high pressre glow excitation of v lasing action in moleclar nitrogen. Applied Physics Letters, 5(), DOI:.6/ Kmar B., Singh S.N., 5, Analytical stdies on the hydralic performance of chevron type plate heat exchanger, International Jornal of Heat and Technology, (), 7-. DOI:.88/ijht.. Li H., Li H., Gao H., Shi P.,, Reliable fzzy control for active sspension systems with actator delay and falt. IEEE Transactions on Fzzy Systems,,, -57. DOI:.9/tfzz..7. Tan H.D., Apkarian P., Narikiyo T., Yamamoto Y.,, Parameterized linear matrix ineqality techniqes in fzzy control system design. IEEE Transactions on Fzzy Systems, 9(), -. DOI:.9/ Tngatarova S.A., Zheksenbaeva Z.T., Abdkhalykov D.B., Baizhmanova T.S.,, Thermostable polyoxide catalysts of complete combstion of methane or biogas in the catalytic heat generators. Chemical Engineering Transactions, 9, Wang L.X.,, Stable adaptive fzzy control of nonlinear systems. IEEE Transactions on Fzzy Systems, (), DOI:.9/9.78. Wei H., Cao J., Rao J., Lei G., Jiang S., Li H.,, The dependence of extracted crrent on discharge gas pressre in netral beam ion sorces on hl-a tokamak. Review of Scientific Instrments, 8(),. DOI:.6/.686. Yi Q.J., Tian M.C., Fang D., 5, CFD simlation of air-steam condensation on an isothermal vertical plate, International Jornal of Heat and Technology, (), 5-. DOI:.88/ijht..