Closed loop operation

Figure 1. Results of closed-loop operations (reactor A) (a) 9 batch without tuning, (b) 10 batch GA tuning...

To supplement the SVD analysis, rigorous d mamic simulations under closed loop operation were carried out. For the closed-loop analysis, several issues must be defined first, such as the control loops for each system, the type of process controller to be used, and the values of the controller parameters. 

The process flow sheet was first tested for direct leaching of steel mill flue dust and production of zinc metal by electrowinning. The tests were performed in a continuously operating pilot plant, producing 10-20 kg/day zinc metal. The same pilot plant was then used for treating copper/zinc-rich brass mill flue dust in a closed loop operation, recycling all the zinc solvent extraction raffinate to the copper circuit leach section. In the zinc circuit leach section, only the amount of zinc rich dust necessary for neutralization of the copper solvent extraction raffinate was used. The results obtained from the pilot plant tests indicated contamination problems within the solvent extraction loops. The estimation of economic data showed a weak return on the assets compared with the alkali route, and sensitivity toward the raw material price. 

Closed-loop operation with no uncontrolled emissions... 

Figure 10. Input coil for either open-loop or closed-loop operation.

V, i, E to external loads in open loop operation, and also with a fraction fed to input for closed loop operation and "self-powering."... 

Figure 11. Output coil for either open-loop or closed-loop operation. Multiple output coils may be used in a variety of configurations.

Thus we have described a system and process having a multiplicity of iterative feedbacks and feedforwards from each component and subprocess, to every other component and subprocess, all increasing the energy collected in the system and furnished to the load. In open-loop operation, this results in COP >1.0 permissibly, since the excess energy is freely received from an external source. In closed-loop operation, the COP concept does not apply except with respect to operational efficiency. In that case, the operational... 

Figure 15 shows a type embodiment of the system and system process, perhaps at a home and powering a variety of home appliances and loads. The system as shown is jump-started initially in open-loop mode, and once in stable operation is disconnected from the jump starter (such as a battery) to run in closed-loop operational mode. 

Fig. 6. A closed loop apparatus for optimally identifying quantum Hamiltonian information. The closed loop operations aim to reveal one or more control experiments that identify the best quality Hamiltonian information. Hamiltonian quality is used as the feedback signal for the learning algorithm guiding the laboratory experiments.

It should be noted that in most cases wastestreams are composed not only of process chemistry but also of by-products of chemical reactions and electrolysis. This fact becomes important when attempting to recover and return those escaped" solutions (e.g., dilute metal-bearing rinse streams) which are often the focus of process and operation modification. It is usually not sufficient to stop generating waste simply by returning it to its source. Usually some type of purification or separation, themselves sources of waste generation, will eventually be required. This quickly puts the lie to the myth of "closed-loop" operations. While source reduction is powerful, it is only reduction, not elimination. 

In order to broaden the data base of the limestone DA process and to evaluate the impacts of closed-loop operation, a series of pilot plant tests was conducted under the sponsorship of U.S. Environmental Protection Agency s (EPA) Industrial Environmental Research Laboratory in Research Triangle Park, NC (IERL-RTP). The testing concentrated on evaluating the effects of magnesium and chloride ions since appreciable accumulations of soluble salts containing these two species are expected in a limestone DA system under closed-loop operating conditions. 

Remark 5.3. Figures 5.10-5.21 show that the response of the mole fraction of the impurity I in the reactor is also slow in closed-loop operation. This is to be expected and was accounted for in the design of the impurity-mole-fraction controller by requesting a sufficiently long time constant for the closed-loop response (5.59). 

Other recent developments in the field of adaptive control of interest to the processing industries include the use of pattern recognition in lieu of explicit models (Bristol (66)), parameter estimation with closed-loop operating data (67), model algorithmic control (68), and dynamic matrix control (69). It is clear that discrete-time adaptive control (vs. continuous time systems) offers many exciting possibilities for new theoretical and practical contributions to system identification and control. 

Capillary zone electrophoresis is another technique which has been used to separate products such as organic acids.26 Separation is based on differences in the mobility of analytes exposed to an electric field. Resolution and separation time in such systems depends on factors including electroosmotic flow (EOF), and a number of approaches for adjusting the EOF have been examined. While some of the approaches (pretreatment of capillaries) are not useful as means of process control, adjusting buffer pH and the electric field27 seem to be possible handles for true feedback control of the separation, although closed-loop operation does not seem to have been attempted. 

Box, E. P. G., Parameter estimation with closed-loop operating data. Technometrics 18,... 

Ljung, L., Information contents in identification data from closed-loop operation, Proc. 32" Conference on Decision and Control, San Antonio, TX (1993). 

Closed loop operations with only a small volume of recycled permeate. 

Twenty years ago industry did not even consider closed-loop operations the entire concept was viewed with suspicion. Today, many U.S. industries have moved successfully toward implementation of this concept. 

By using this technique, operations free of calcium sulfate scaling have been demonstrated in laboratory and field installations. This seeding technique is the key to closed loop operation in which liquid leaves the system only by evaporation or in combination with the solid by-product of the scrubbing system. Disposal of this solid is discussed later. 

Amount of solute and the experimental effort is high, as only one equilibrium point is determined per injection. This is increasingly import if kinetic effects are strong and thus the time needed to reach the phase equilibrium is rather long. Closed-loop operation may be used to reduce the consumption of solutes... 

In KIER (Korea Institute of Energy Research), IS process which was first proposed by General Atomic Co. [2] and laboratory scale closed-loop operated in JAERI (Japan Atomic Energy Research Institute) [1,3], is tmder investigation with KAERI (Korea Atomic Energy Research Institute) and KIST (Korea Institute of Science and Technology). IS cycle is composed of the following reactions ... 

To establish the closed-loop operation technology, the composition and the flow rate of the process solution maintain to be constant for the steady state operation. The separation properties of solution in the liquid phase separator to keep the constant composition and flow rate of the process solution. Sakurai et al. [4] was reported the effects of solution temperature and composition of initial solution in the liquid phase using HI-H2SO4-I2 solution. They found that the separation properties were improved with the increase in iodine concentration. The control of the side reaction in the liquid phase separation of Bunsen reaction is also important to establish the closed-cycle operation technology. 

Closed-loop operation for continuous hydrogen production... 

The small-scale apparatus will be built up in Oct. 2005. The apparatus was designed to produce hydrogen at the maximum rate of 20Nt /h, and is made of glass and Teflon. The operation will be carried out at atmosphere condition. A higher iodine concentration of Hix solution will be handled with an apparatus. The closed-loop operation technique for continuous hydrogen production will be developed using this apparatus. The experiments will start in November 2005. 

Figure 5 shows KIER s R D plan for the IS process. Studies on the closed-loop operation technologies at atmosphere condition using the small-scale apparatus will be carried out until 2006. Studies on process improvement and collection of data in each reaction will be carried out until 2010 for the laboratory and pilot scale equipment that will demonstrate hydrogen production at the rate of l,000N-t/h and 30 100Nm7h, respectively. 

Studies on the closed-loop operation technologies at pressure condition will be carried out until 2009 to acquire knowledge on process control and to establish the detailed process scheme required for the scale-up experiment. 

The pipe sizes for feed and return lines for the closed loop operation are much smaller than that for the open loop system which can also reduce the capital and operating cost. The feed tank size can also be much smaller for the closed loop which then allows shorter residence times for heat or shear sensitive products. 

Micrometers are also useful positioning elements. Although manually operated micrometers are not suitable for most imaging applications, they provide an inexpensive way to acquire current-distance curves and perform substrate modifications (17,18). Submicron positioning is available with differential micrometers. Motorized micrometers are widely available, and micrometers with DC servo motor drives in closed-loop operation (see below) can give excellent results. 

---