Open Plate Reactor Research Articles

Decomposition of solution droplets under the influence of thermal convection over a heated horizontal plate

Experimental approaches using an open-plate reactor were proposed to investigate the thermal decomposition and deposition processes of solution droplets sprayed over a heated horizontal plate. The temperature-dependent flow condition of the carrier gas may influence the properties of incoming sprayed aerosols. Zinc oxide (ZnO) particle layers were synthesized by spraying zinc acetate solution to the plate with deposition angle of 45°. The prepared particle layers and a numerical simulation verified the presence of thermally generated convection and fluid instability. Correlation between the size and morphology of deposited aerosols and the dynamical condition due to temperature distribution above the plate has been analyzed. A short distance (2 cm) between the nozzle and the plate will prepare finer (nanometer-scaled) ZnO particle layers. ZnO with higher crystallinity can be prepared using one-step route (directly spraying at 450 °C) compared with those of two-step heating procedures (150 °C – spraying then 450 °C – re-heating in 1 h), which consume higher energy.

Evaluation of an intensified continuous heat-exchanger reactor for inherently safer characteristics

The present paper deals with the establishment of a new methodology in order to evaluate the inherently safer characteristics of a continuous intensified reactor in the case of an exothermic reaction. The transposition of the propionic anhydride esterification by 2-butanol into a new prototype of “heat-exchanger/reactor”, called open plate reactor (OPR), designed by Alfa Laval Vicarb has been chosen as a case study. Previous studies have shown that this exothermic reaction is relatively simple to carry out in a homogeneous liquid phase, and a kinetic model is available. A dedicated software model is then used not only to assess the feasibility of the reaction in the “heat-exchanger/reactor” but also to estimate the temperature and concentration profiles during synthesis and to determine optimal operating conditions for safe control. Afterwards the reaction was performed in the reactor. Good agreement between experimental results and the simulation validates the model to describe the behavior of the process during standard runs. A hazard and operability study (HAZOP) was then applied to the intensified process in order to identify the potential hazards and to provide a number of runaway scenarios. Three of them are highlighted as the most dangerous: no utility flow, no reactant flows, both stop at the same time. The behavior of the process is simulated following the stoppage of both the process and utility fluid. The consequence on the evolution of temperature profiles is then estimated for a different hypothesis taking into account the thermal inertia of the OPR. This approach reveals an intrinsically safer behavior of the OPR.

Dynamic Behaviour of a Continuous Heat Exchanger/Reactor after Flow Failure

The intensified technologies offer new prospects for the development of hazardous chemical syntheses in safer conditions: the idea is to reduce the reaction volume by increasing the thermal performances and preferring the continuous mode to the batch one. In particular, the Open Plate Reactor (OPR) type ``reactor/exchanger" also including a modular block structure, matches these characteristics perfectly. The aim of this paper is to study the OPR behaviour during a normal operation, that is to say, after a stoppage of the circulation of the cooling fluid. So, an experiment was carried out, taking the oxidation of sodium thiosulfate with hydrogen peroxide as an example. The results obtained, in particular with regard to the evolution of the temperature profiles of the reaction medium as a function of time along the apparatus, are compared with those predicted by a dynamic simulator of the OPR. So, the average heat transfer coefficient regarding the ``utility" fluid is evaluated in conductive and natural convection modes, and then integrated in the simulator. The conclusion of this study is that, during a cooling failure, a heat transfer by natural convection would be added to the conduction, which contributes to the intrinsically safer character of the apparatus.

Selection of Sensors by a New Methodology Coupling a Classification Technique and Entropy Criteria

Complex industrial processes invest a lot of money in sensors and automation devices to monitor and supervise the process in order to guarantee the production quality and the plant and operators safety. Fault detection is one of the multiple tasks of process monitoring and it critically depends on the sensors that measure the significant process variables. Nevertheless, most of the work on fault detection and diagnosis found in literature place more emphasis on developing procedures to perform diagnosis given a set of sensors, and less on determining the actual location of sensors for efficient identification of faults. A methodology based on learning and classification techniques and on the information quantity measured by the Entropy concept, is proposed in order to address the problem of sensor location for fault identification. The proposed methodology has been applied to a continuous intensified reactor, the ‘open plate reactor (OPR)’, developed by Alfa Laval and studied at the Laboratory of Chemical Engineering of Toulouse. The different steps of the methodology are explained through its application to the carrying out of an exothermic reaction.

Classification as an aid tool for the selection of sensors used for fault detection and isolation

Complex industrial processes demand significant financial investment in sensors and automation devices to monitor and supervise the process in order to guarantee the production quality and the plant and operators safety. Fault detection is one of the multiple tasks of process monitoring and it critically depends on the sensors that measure the significant process variables. Nevertheless, most of the work on fault detection and diagnosis found in literature place more emphasis on developing procedures to perform diagnosis given a set of sensors, and less on determining the actual location of sensors for efficient identification of faults. A methodology based on learning and classification techniques and the information quantity measure, by the entropy concept, is proposed in order to address the problem of sensor location for fault identification. The proposed methodology has been applied to a new concept of intensification reactor, the Open Plate Reactor, developed by Alfa Laval and the Laboratory of Chemical Engineering located at Toulouse.

Modeling and control of a novel heat exchange reactor, the Open Plate Reactor

A new chemical reactor, the Open Plate Reactor, is being developed by Alfa Laval AB. It combines good mixing with high heat transfer capacity into one operation. With the new concept, highly exothermic reactions can be produced using more concentrated reactants. A nonlinear model of the reactor is derived and a control system is developed. For temperature control a cooling system is designed and experimentally verified, which uses a mid-ranging control structure to increase the operating range of the hydraulic equipment. A Model Predictive Controller is proposed to maximize the conversion under hard input and state constraints. An extended Kalman filter is designed to estimate unmeasured concentrations and parameters. Simulations show that the designed control system gives high conversion and ensures that the temperature inside the reactor does not exceed a pre-defined safety limit.

CHALLENGES IN START-UP CONTROL OF A HEAT EXCHANGE REACTOR WITH EXOTHERMIC REACTIONS; A HYBRID APPROACH

In this paper, the control of a continuous heat exchange reactor is investigated from a hybrid perspective with focus on the start-up phase and the transition to the optimal operating point. The temperature sensitive exothermic reaction leads to the possibility of multiple steady states and in combination with safety constraints forms an interesting challenge for a safe and efficient start-up. A series of MPC controllers are developed with a switching logic that transfers the process from initial rest to continuous optimal operation mode. The control procedure is verified in simulations with a full nonlinear model of the Open Plate Reactor, an improved heat exchange reactor being developed by Alfa Laval AB. The case study can be seen as a benchmark problem for start-up control of exothermic reactions.

Performance Evaluation of a Novel Concept “Open Plate Reactor” Applied to Highly Exothermic Reactions

The implementation of chemical reactions in batch or semibatch reactors is strongly limited by the constraints linked to the dissipation of the heat generated by the reactions. A novel concept of heat exchanger reactors offers enhanced thermal performances in a continuously operating reactor. A study program is proposed to assess the feasibility and potentialities of this concept. Two kinds of reactions are carried out to characterize simultaneously the reactor performances in terms of reaction and heat exchange: the oxidation of sodium thiosulfate by hydrogen peroxide and an acidobasic reaction (NaOH/H2SO4). The resultant experimental data emphasize a significant thermal efficiency: the reactant concentrations and therefore the heat generation can be increased without risk of thermal runaway.

PROCESS CONTROL OF AN OPEN PLATE REACTOR

A new chemical reactor, the Open Plate Reactor, is being developed by Alfa Laval AB. It combines good mixing with high heat transfer capacity. With the new concept, highly exothermic reactions can be produced using more concentrated reactants. A utility system to provide the reactor with cooling water is designed and experimentally verified. The utility temperature controller is based on a mid-ranging control structure to increase the operating range of the hydraulic equipment. A Model Predictive Controller is proposed to maximize the reaction yield under hard input and state constraints. Simulations show that the designed process control system gives high reaction yield and ensures that the temperatures inside the reactor do not exceed a predefined safety limit.