Tyreus-Luyben tuning

Figures 6.14 and 6.15 give dynamic responses of the tray temperatures, reboiler heat input, and bottoms product impurity. The temperature loops were tuned using the TL (Tyreus-Luyben) tuning rules after the ultimate gain and ultimate frequency had been determined using a relay-feedback test. Two 0.5-minute first-order lags are used in the temperature loop. Temperature transmitter spans are 100T. The ultimate gain and period for the tray 6 temperature loop are 4.2 and 2.7 minutes, and for the tray 14 loop are 12.7 and 2.5 minutes. These results reflect the fact that the process gain is higher when tray 6 is...

The final control structure is shown in Figure 7.46. Both the R/F and the QR/F ratios are installed. Of course the temperamre controller must be retuned. Relay-feedback testing and Tyreus-Luyben tuning give Kc = 1.96 and ti = 11.9 min. The composition controller also must be retuned but changes only slightly. 

Since the reflux-drum level loop is nested inside the temperature loop, the level loop is tuned first. A relay-feedback test and Tyreus-Luyben tuning rules give the results shown in Table 8.5. Notice that the gain and integral times are very much different than a conventional level control loop. The integral time is about 8 min and the gain is only 0.3. 

The four composition control loops each have a 5 min deadtime. They were tuned using a sequential method. Because reboiler heat input affects aU of the controlled variables fairly quickly, the Xb(x/<2r loop was tuned first with the other three controllers on manual. Relay-feedback testing was used to find the ultimate gain and period. Tyreus-Luyben tuning rules were used. Next, since reflux affects all compositions, the Xixt)IR loop was tuned using the same procedure with the Xb(j) Q loop on automatic. Then the Xs(x> loop was tuned with the two loops on automatic. Finally, the ypio(x) loop was tuned with the other three loops on automatic. Table 12.2 gives controller tuning results for aU four loops. 

All four loops contain 5 min dead times. The loops in each column were tuned sequentially with the reboiler heat input loop closed first with the reflux loop on manual. Relay-feedback and Tyreus-Luyben tuning were used. Then, with the reboiler heat input loop on automatic, the reflux loop was tuned. Table 12.2 gives the tuning parameters. 

Reflux-drum temperature in the stripper is controlled by manipulating stripper reboiler duty (temperature controller TCS in Fig. 14.10). A 1 min deadtime is inserted in the loop, and relay-feedback testing and Tyreus-Luyben tuning give tc = 2.65 and Tj= 13.2 min. 

The ramp disturbances are imposed on the process using each of the three control structures. The temperature and valve-position controllers are tuned by running relay-feedback tests. Deadtimes of 1 min are used in these loops. Temperature controller TCI is tuned at the normal design feed flow rate (4000 kmol/h), and Tyreus-Luyben tuning give Kc = 31 and Ti = 9.2min. 

The tuning of the temperature controller is different with and without the QR/F ratio since in the former case the controller output is reboiler duty while in the latter case it is the QR/F ratio. A 1 min deadtime is inserted in the temperature measurement. Relay-feedback testing and Tyreus-Luyben tuning give Kc = 0.636 and Ti = 14.5 min using a temperature transmitter range of 300-400 K and a controller output range of 0-0.05 ratio. 

With the reflux flowrate fixed, mnning a relay-feedback test and using Tyreus-Luyben tuning give temperature controller constants Kc = 0.73 and tj = 16 min for a deadtime of 1 min. The controller is reverse acting. The temperature transmitter range is 150-250°F with a 206.2°F setpoint. The temperature controller output is 0 to 300 x 10 Btu/h. 

Figure 5.8 shows the control structure developed for this system. Conventional PI controllers are used for all flows, pressures, and temperatures. Proportional controllers are used for all liquid levels. Relay-feedback tests are run on the two temperature controllers to determine ultimate gains and periods, and Tyreus-Luyben tuning is used. Each temperature controller has a 1-min deadtime in the loop. Reflux ratios are held constant in each column (2.84 in the low-pressure column and 3.11 in the high-pressure column). 

Deadtimes of 1 min are inserted in the two temperature loops. Table 6.1 gives temperature transmitter ranges, controller output ranges, and several tuning parameters. Relay-feedback tests are mn, and Tyreus-Luyben tuning is used in both controllers. All level controllers are proportional only with Kc = 2. 

All level controllers are proportional only with a gain of 2. The trays selected for temperature control are located near the bottom of the columns, where the temperatures are changing the most rapidly from tray to tray (see Figure 7.9). A 1-min deadtime is inserted in each temperature loop. Relay-feedback tests and Tyreus-Luyben tuning are used to obtaining... 

The Aspen Plus file of this extractive distillation system is exported to Aspen Dynamics after dynamic parameters are specified (equipment sizes). Figure 11.8 shows the control stmcture developed for this system, which is based on the extractive distillation control structure proposed by Grassi. Relay-feedback testing and Tyreus-Luyben tuning of the temperature loops give the controller parameters given in Table 11.2. The temperature controllers have 1 min deadtimes in the loops. Reflux ratios are held constant in each column (3.44 in the extractive column and 1.61 in the methanol column). 

Temperature controllers are mned by mnning relay-feedback tests and applying Tyreus-Luyben tuning rules. Controller parameters are given in Table 11.6. The dynamic performance is tested by subjecting the system to disturbances in feed flowrate and feed composition. 

Consider the transfer function model in Eq. 12-10 with K = 2,1 = 5, and 0 = 1. Compare the PID controller settings obtained from the Ziegler-Nichols and Tyreus-Luyben tuning relations in Table 12.4. Simulate the... 

Relay-feedback tests are run individually on both temperature loops with the other loop on manual. Three 1-min temperature measurement lags are included. Temperature transmitter spans are 50 K. Valves are half open at steady state. Controller tuning constants are given in Table 11.1. Tyreus-Luyben tuning constants are used with some reductions in controller gains to give less oscillatory behavior. 

Controller Timing. The composition controller and the temperature controller ate tuned by running relay-feedback tests and using Tyreus-Luyben tuning. Table 15.1 provides parameter values. The temperature controller was tuned first, with the composition controller on manual. Then the composition controller was tuned with the temperature stiU on automatic (sequential tuning). The level controllers are proportional only with gains of 2. 

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