Industries that generate large quantities of liquid waste, e.g. the nuclear energy or mining industries, are familiar with the accumulation of water in ponds, both indoor and outdoor. The treatment of the water necessary for release can seem as an insurmountable challenge, both based on the sheer volume and on the hazards involved. Pumping the waste through a column would typically involve high pressure, while any accidental release or spillage must be avoided.
Activated carbon is a common choice for removing impurities or capturing compounds from a product batch. However, the carbon may itself foul the product and be difficult to separate. The rotating bed reactor offers a clean way to deploy activated carbon that removes the need for time-consuming filtration and extends the lifetime of the solid phase.
Automation of large-scale processes is often a requirement for economically viable chemical processes. The benefits of scale are best harvested at high throughputs and 24/7 operation. This leads to the demand for process automation, and the elimination of hands-on work.
Removing ions from liquids is common in industry and society. Ions are remediated in applications ranging from the production of pharmaceuticals to the treatment of communal waste streams. Likewise, the nuclear energy sector deals with the removal of ionic radioactive substances from water on a daily basis.
A fixed bed reactor (FBR), also known as a packed bed reactor or column, is a traditional technology for processes such as adsorption or heterogeneous catalysis. Achieving the required level of purification or conversion means running the liquid through the reactor at a sufficiently low flow rate, and the throughput of a fixed bed reactor is therefore often limited.
Mass transfer limited reactions can create problems for applications like the synthesis of chemical products or the manufacture of active pharmaceutical ingredients. Poor yields, high side-product formation or impractically long reactions are potential issues. Efficient reactor design can greatly improve the mass transfer and remove the limitation to a minimum.
Liquids with high viscosity create problems for heterogeneous applications in traditional reactors. Packed bed reactors (columns) suffer from huge back pressures, and stirred tank reactors (STR) exhibit reduced reaction rates due to poor mixing. Both issues lead to longer processing times and expensive operations.
The IBC, also called “tote”, is a common storage container in many industries. In a chemical manufacturing plant or a waste treatment facility there might be hundreds of these or more, with a capacity of approximately 1,000 liters (275 gallons). Whether they are filled with raw material, finished product or waste, the transfer of liquids to and from IBCs can be cumbersome or even hazardous.
Decolorization, pesticide remediation, catalysis, and many other applications involve dealing with viscous liquid that needs to be modified in some way. The rotating bed reactor presents an efficient way to treat viscous liquids, without the challenges of conventional reactors.
Organic molecules contaminate many products and waste streams, and are a common target for remediation. Activated carbon is a widely used adsorbent to capture organic molecules from aqueous solutions (like wastewater), and offers a very wide range of applications thanks to its unspecific method of adsorption. At the same time, activated carbon can cause fouling of another kind by the particles breaking down into smaller fines. This dust-like material is very cumbersome to remove from the liquid afterwards.
The rotating bed reactor (RBR) is a clean way to use activated carbon for purification, which eliminates the need for time-consuming filtration and extends the lifetime of the solid phase. It is available on scales ranging from milliliters to hundreds of cubic meters and offers faster decolorization, elimination of filtration, and extended adsorbent lifetime.
When working with an emulsion (and particularly with a heterogeneous catalyst) the mass transfer between the phases is critical. Insufficient mixing leads to lower interfacial area per volume, and in turn to poor mass transfer across the phases.
As a tool for heterogeneous catalysis, or purification of liquids using materials like activated carbon, the rotating bed reactor provides high throughput capability frequently exceeding traditional technologies.
Large volumes of liquid waste will often accumulate at industrial sites. It may be very time-consuming and resource-intensive to adequately treat these waste streams for release, so the problem often compounds over time.
How can this process be scaled up? This is perhaps the most important question to consider when developing a chemical process. If it cannot be done on large scale, all the time and resources invested in laboratory work will be unrewarded. Pumping liquids through massive columns or separating solids from a large batch can be unsurmountable challenges that bring a halt to a new project before it has even left the starting blocks.
Many heterogeneous processes are limited by mass transfer at typical laboratory or industrial conditions. When using a rotating bed reactor, the mass transfer is most easily controlled using the rotational speed.
When using of solid-phase catalysts or adsorbents in reactors, the physical degradation of the materials is a common problem. The traditional stirred tank reactor inflicts mechanical damage to the particles, which causes attrition, fines that are difficult to separate, and loss of the functionality of the solid-phase.
The synthesis of products, such as active pharmaceutical ingredients (APIs), often involves multiple steps using heterogeneous catalysts or adsorbents. Thus, the simultaneous use of multiple solid phases either during synthesis or downstream processing is frequently highly advantageous.
A small rotating bed reactor (RBR) system deployed in an external loop to the customer’s regular reaction vessel. Even though RBR technique has been identified as offering advantages for a particular process, deploying it in an existing reaction vessel may prove difficult for practical reasons. This is were “plug-in” mode deployment of the RBR can offer a solution. The RBR and associated vessel is attached in an external loop by inlet and outlet connections to the regular vessel. The “plug-in” RBR system is typically small compared to the regular vessel. Alternatively, the RBR system can be deployed in a vessel → RBR → 2nd vessel mode. A proof-of-concept demonstration of an RBR in “plug-in” mode by a decolorization. The volume of the “plug-in” vessel is ca 0.7% of the regular vessel it is attached to.
Heterogeneous reactions involving viscous solutions put high demands on equipment and materials. Columns face high pressure drops and require powerful pumps and durable solid phase particles. Stirred tank reactors do not face the same problem, but the high liquid viscosity and low particle density will have a negative impact on reaction kinetics and require tedious filtration to separate the solids afterwards.
Sometimes you don’t want to pack the entire rotating bed reactor full with your solid-phase material. Fully loading might simply be wasteful, or you may want to experiment with your reaction conditions. But how does the amount of solids in the rotating bed reactor influence the reaction performance? Can you use only 10% of the full capacity?
In the manufacture of liquid products, they may be coloured with appealing and brand-building colourants. During changes of batches, downtimes, or other regular day-to-day operations, coloured product residues are washed out of the process line. These are ideally recycled to minimize waste and maximize utility. For this, however, they need to undergo decolourization. Below we present a customer story in which the SpinChem RBR technoloy was deployed to decolourize viscous product residues.
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