Real-time Control Technology Research Articles

Latent Variables-Based Process Modeling of a Continuous Hydrogenation Reaction in API Synthesis of Small Molecules

Continuous manufacturing can be benefited by the use of the Quality by Design (QbD) strategy for robust process development and by the use of Process Analytical Technology (PAT) for real-time process monitoring and control. A successful implementation of QbD and PAT for continuous processes relies on a robust and information-rich process model as a basis for process understanding, monitoring, and control. Compared to first principles and other empirical models, a latent variables-based process model is capable of decomposing multidimensional process data into a few orthogonal latent variables and of providing accessible process understanding/visualization and control within the latent variable space. This study is an extension of our group’s earlier effort (Liu et al., J Pharm Innov 6:170–180, 2011) to explore the utility of latent variables-based process modeling in pharmaceutical manufacturing processes. The case presented here is the first application of latent variables-based modeling to a reaction process in small-molecule active pharmaceutical ingredient route synthesis, i.e., a continuous-flow hydrogenation. A particular reactor configuration and operation was used in this proof-of-concept study. It was found that time-variant profiles of pressure in the flow tube reactor served as an effective indicator of gas–liquid interaction within the reactor, thus determining process outcomes, i.e., the extent of reaction and enantiomeric excess (ee), given the importance of process set points. In addition, a design space of process parameters predicted to produce optimal outcomes, i.e., extent of reaction greater than 98 % and ee higher than 93 %, was established in order to provide a flexible operation space for performing the reaction with desired process outcomes. The capabilities of latent variables-based process modeling have been well demonstrated as applied to a continuous-flow hydrogenation reaction, regarding its improved process understanding and the potential for process optimization & control as well. Future efforts will be focused on continuing understanding of the capabilities and limitations of such a methodology on a fully-automated control scheme for continuous flow reaction.

Integrated real-time control strategy for nitrogen removal in swine wastewater treatment using sequencing batch reactors

A new integrated real-time control system was designed and operated with fluctuating influent loads for swine wastewater treatment. The system was operated with automatic addition control of an external carbon source, using real-time control technology, which utilized the oxidation–reduction potential (ORP) and the pH as parameters to control the anoxic phase and oxic phase, respectively. The fluctuations in swine wastewater concentration are extreme; an influent with a low C/ N ratio is deficient in organic carbon, and a low carbon source level can limit the overall biological denitrification process. Consequently, a sufficient organic source must be provided for proper denitrification. The feasibility of using swine waste as an external carbon source for enhanced biological nitrogen removal was investigated. The real-time control made it possible to optimize the quantity of swine waste added as the load fluctuated from cycle to cycle. The average removal efficiencies achieved for TOC and nitrogen were over 94% and 96%, respectively, using the integrated real-time control strategy.

생물학적 축산폐수 처리공정의 자동제어 방법 및 제어 인자의 안정성

SBR 처리공정의 자동제어 인자로서의 ORP, pH, DO의 안정성과 유용성을 비교 평가하였다. 시스템 운전동안 ORP와 pH(mV)-time profile 상에서 요염물질의 특이적인 변화시점을 나타내는 NBP와 NKP가 잘 나타났으며 이 시점은 MSC(moving slope change)를 이용하여 쉽게 인식될 수 있는 것으로 밝혀졌다. 그러나 부하량과 포기량 혹은 시스템 OUR이 불균형일 때는 DO나 ORP-time profile 상에서 NBP로 잘못 인식될 수 있는 가짜 제어시점이 여러 번 발생하거나 혹은 제어시점으로 인식할만한 변화가 전혀 발생하지 않음을 알 수 있었다. 그러나 pH(mV)-time profile에서는 어떤 운전조건과 상태에서도 항상 뚜렷한 NBP가 발생하고 MSC를 이용한 제어시점 인식이 가능함을 알 수 있었다. 따라서 호기적 처리과정 중의 시스템 진단과 자동제어 인자로 ORP나 DO 보다 pH(mV)가 안정적임을 알 수 있었다. 반면 무산소 상태의 모니터나 제어에 있어서는 pH(mV)-time profile에서 NKP를 안정적으로 인식하는 데에는 한계가 있었으나 ORP에서는 매우 안정적인 것으로 나타나 무산소 처리과정의 진단/제어인자로는 ORP가 다른 인자들 보다 유용함을 알 수 있었다. 이러한 결과로 미뤄 SBR 공정의 안정적인 자동제어를 위해서는 ORP 혹은 pH(mV)를 단독으로 이용하는 것 보다는 병용하는 것이 바람직하며, 이러한 자동제어기술은 유입수내 오염물질의 농도 변이와 운전여건에 상관없이 항상 오염물질의 완전제거를 가능케 함은 물론 처리시간 및 처리용량의 최적화를 위한 실용적 기술이 될 것으로 판단된다. The feasibility and stability of ORP, pH(mV) and DO as a real-time control parameter for SBR process were evaluated in this study. During operation, NBP(nitrogen break point) and NKP(nitrate knee point), which reveal the biological and chemical changes of pollutants, were clearly observed on ORP and pH(mV)-time profiles, and those control points were easily detected by tracking the moving slope changes(MSC). However, when balance of aeration rate to loading rate, or to OUR(oxygen uptake rate), was not optimally maintained, either false NBP was occurred on ORP and DO curves before the appearance of real NBP or specific NBP feature was disappeared on ORP curve. Under that condition, however, very distinct NBP was found on pH(mV)-time profile, and stable detection of that point was feasible by tracking MSC. These results might mean that pH(mV) is superior real-time control parameter for aerobic process than ORP and DO. Meanwhile, as a real-time control parameter for anoxic process, ORP was very stable and more useful parameter than others. Based on these results, a stable real-time control of process can be achieved by using the ORP and pH(mv) parameters in combination rather than using separately. A complete removal of pollutants could be always ensured with this real-time control technology, despite the variations of wastewater and operation condition, as well as an optimization of treatment time and capacity could be feasible.

Valuation of Technology and Information for Reservoir Risk Management

SummaryReservoir risk management involves optimizing assets given inherent reservoir uncertainties and minimizing risk by reducing these accordingly. The decision to implement any reservoir management technology is usually based on some form of cost-benefit analysis. Consequently, the correct valuation of value-adding technology (often based on net present value, or NPV) becomes a significant part of a reservoir management process. This paper discusses techniques for the valuation of technology and information related to reservoir risk management. For demonstration purposes, these techniques are applied to valuation of real-time control and monitoring technologies in a reservoir with multiple uncertainties in its physical properties. Because of the presence of these uncertainties, value quantification requires a stochastic optimization of the reservoir production strategy, where the objective function includes a risk-aversion factor. By applying these techniques, one can generate a decision-making table that shows the benefit of implementing a technology at various confidence levels. One can then extend the analysis further to estimate the added value to the reservoir if the uncertainties were to be reduced (or even eliminated) by implementing appropriate monitoring technologies. This process enables quantification of the value of information and is useful in designing monitoring strategies.

Real-time control of an immobilized-cell reactor for wastewater treatment using ORP

The performance of an immobilized-cell reactor for simultaneous carbon–nitrogen removal in synthetic wastewater with an intermittent aeration (IA) process under real-time control of oxygen supply was investigated. The oxidation–reduction potential (ORP) was monitored during operation. The ORP–time profile showed distinctive turning points, which directly correlated with the changes in the system chemistry and biological activity. The reactor was conducted by cyclic fixed-time aeration–nonaeration operation at the beginning, followed by real-time control technology using ORP setpoint. A moving window along the slope of the ORP curve was employed to search for the nitrate breakpoint of the aeration cycle. Once the breakpoint was found, the reactor was aerated for a fixed period. The treatment process could effectively avoid the anoxic fermentation state under the real-time control. The cycle time was reduced around 30%. The duration of aeration period was found to be optimum at 3 h under the consideration of the removal efficiencies of COD and total nitrogen. The real-time control system not only exhibited a better nitrogen removal efficiency than the fixed-time control operation, but it also showed a stable effluent quality during the change of HRT from 3 to 8 h. Good operation stability was demonstrated even when a very high disturbance of the influent loading occurred.

Biological nutrient removal with an internal organic carbon source in piggery wastewater treatment

The feasibility of using an internally available carbon source for biological nitrogen and phosphorus removal was investigated. A new integrated animal wastewater treatment process consisting of two reactors was operated with various sequences for the treatment of high strength piggery manure. The treatment process was operated with real-time control technology, which utilized the oxidation–reduction potential (ORP). In the first operation, the sludge in each reactor was completely separated (sludge separation strategy, SSS), while a portion of the sludge in the first reactor was added into the second reactor in every cycle of the second operational strategy (sludge addition strategy, SAS). None of the operating strategies used a supplemental carbon source to achieve enhanced phosphorus release and denitrification. By achieving successful real-time control, very high removal efficiencies of organic matter, nitrogen and phosphorus were obtained in both operations. These high performances were mainly achieved by means of biological mechanisms, not chemical and physical processes. The real-time control made it possible to utilize an internally available organic material for phosphorus removal and denitrification of produced NO x -N, without any external carbon source. Furthermore, it was found that an optimization of aeration periods could be achieved by using the tested real-time control technology, since the technology stopped the aeration when the targeted oxidation status occurred in treatment system. The HRT obtained in both the SSS and the SAS was proportional to the F/M ratio. Experimental data showed that the sludge addition strategy (SAS) has a practical advantage over the sludge separation strategy (SSS), in that the SAS enhanced the denitrification and resulted in constant and low effluent NO x -N concentrations.

Control of a swine manure treatment process using a specific feature of oxidation reduction potential

A real-time control strategy for waste treatment, using a specific feature of oxidation–reduction potential (ORP) feature, was developed; the usefulness of this technology was evaluated through two separate operations. A newly designed, two-stage, bench-scale wastewater treatment process for swine wastewater was successfully operated with this real-time control technology. The nitrogen break point (NBP) on the ORP-time profile was designated as a real-time control point. By designating the NBP as such, sufficient organic carbon matter for denitrification could be left in the mixed liquor and completely removed during denitrification. Since the treatment stages were not controlled by a timer, but by the ORP real-time control point, the process could provide consistently high reduction of combined organic carbon (C), nitrogen (N) and phosphorus (P) concentrations, despite the large fluctuation of animal wastewater characteristics. The average system performance, relative to influent strength, was in excess of 96% for the C, N and P. Real-time control techniques worked effectively without the addition of an external carbon source in the treatment of swine manure: effective N and P removal was achieved, using internally available organic matter.

Use of computer technology for real-time control of blast-furnace smelting

Use of computer technology for real-time control of blast-furnace smelting

Control of semiconductor manufacturing equipment: real-time feedback control of a reactive ion etcher

This paper describes the development of real-time control technology for the improvement of manufacturing characteristics of reactive ion etchers. A general control strategy is presented. The principal ideas are to sense key plasma parameters, develop a dynamic input-output model for the subsystem connecting the equipment inputs to the key plasma variables, and design and implement a multivariable control system to control these variables. Experimental results show that this approach to closed-loop control leads to a much more stable etch rate in the presence of a variety of disturbances as compared to current industrial practice.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>