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NiTech Solutions Ltd is a UK-based private company that provides continuous process technology solutions for reaction and crystallisation unit operations, using its patented baffled vessel technology together with its extensive process know-how.
Stirred tank reactors (STRs) have been the workhorse in manufacturing chemicals, pharmaceuticals and food products since records began, and face the century old problem that mixing gets worse with increasing scale. This un-scalable mixing in stirred tanks is the root of the problem, meaning that one cannot repeat what was obtained in labs, e.g. a 30 min reaction in the lab would require a process time and associated process inventory of over 30 hrs. Because of this poor mixing in stirred tanks:
These can be problematic for reactions:
These can also be problematic for crystallisation processes as:
Better mixing and plug flow can be achieved in STRs when operated in a cascade format. In theory, an infinite number of STRs are required to achieve plug flow; in practice, the more the better, but in reality, it is a balance of costs and the degree of plug flow achievable – as every tank added is associated with a £ sign covering both capital and running costs. Cascade STRs are the norm in process industries.
The essence of NiTech reactor technology enables kinetic (theoretical) reaction times obtained in labs to be executed in pilot and full scales, due to uniform mixing and plug flow achieved through the combination of fluid oscillation and baffle restrictions. By doing so, it:
The essence of NiTech crystalliser technology enables the control of both mixing and temperature (cooling) simultaneously in labs as well as pilot and full scales, due to uniform mixing, plug flow and superior heat transfer rate achieved. By doing so, it:
NiTech technology makes the right product every time.
Near plug flow can be attained in turbulent flows – this mechanism is the driving force for mixing in other types of flow reactors. As high net flow Reynolds numbers (high flow rates) are required to achieve turbulent flows in tubular reactors, only shorter reaction times, e.g. <10 mins, can be accommodated or forbidden reactor lengths would be needed. Loop reactors, coil reactors and jet reactors belong to this category.
In theory, mixing in microreactors should follow the above principle, but this would lead to an infinitely long reactor length due to every small diameter of the channel/tube (in micrometers). In contrast to the operation of other flow reactors above, small flow rates in creeping flow range are utilised in microreactors. Diffusion is thus the main driver for mixing that is aided by flow around bends and other restrictions within the internal configuration of the channels/tubes.
Mixing in NiTech reactors is achieved by eddy motions that are generated by the combination of fluid oscillation and the presence of baffles and is not controlled by net flow as in other flow reactors. The unique feature of decoupling net flow from mixing allows the accommodation of longer reaction/process times, e.g. 2 hours. It should be noted that NiTech’s tubular baffled reactor (TBR) technology can be used for reaction times from seconds to a few minutes.
In terms of process classifications, microreactors have very high specific surface areas and are good for reactions with high exotherms and have been used for liquid-liquid and some gas-liquid reactions. Solids are barriers for diffusion, hence microreactors seldom handle solids, while NiTech reactors are good for processes involving solids-liquid, liquid-liquid and some gas-liquid.
No, this is done under licence by partner Alconbury Weston Ltd (AWL), based in Stoke-on-Trent, UK.
This is done through NiTech’s technology partners across the world or at customers’ sites using purchased or rented NiTech lab-scale units. Here are the general steps to get involved:
NiTech has agents and technology partners worldwide, including:
More agreements are being finalised and will be added to the list.
NiTech offers a variety of lab units:
The glass units are suitable for temperatures up to 100⁰C (optional extra of 150⁰C) and ambient pressure. The 316 L steel variant can handle pressures up to 10 bar.
Temperatures up to 100⁰C, pressures up to 3 bar can be achieved on the tube side and up to 1 bar on the jacket side. The glass is borosilicate and the wetted parts are PTFE and PEEK. Optional extras include higher temperature (150⁰C), on-board integrated peristaltic pumps and bespoke feed and instrument collars.
These units are suitable for temperatures up to 150⁰C and pressures up to 10 bar, with higher temperature (200⁰C) and higher pressure (25 bar) on request. Sight glasses are included.
The nominal flow rate for the continuous units is 40 mL/min based on residence times between 30 and 90 mins for lab-scale experiments. This can be increased or decreased depending on chemistry.
For production units, the flow rates range from 30 to 120 L/min.
NiTech provides clients with continuous reaction and crystallisation solutions for their existing batch processes. NiTech’s business model consists of:
More than 50 NiTech units have been installed since 2005 for academic, research and commercial organisations across the world. These range from small-scale lab units for R&D purposes to pilot and full-scale manufacturing units. Some specific cases are available on our website.
The following is a list of typical questions for initially assessing the suitability of a process for NiTech technology.
NiTech technologies are best suited for a range of intrinsic reaction times from seconds to a few hours. Typically, residence times of up to 120 mins can be done in one unit, for longer intrinsic reaction times, two or more units are better in a cascade fashion. Note that intrinsic reaction time refers to the process time without heat or/and mass transfer constraints, and is often indicated by lab test data, not data from production units.
The pie chart below illustrates the reaction time distributions for a large number of chemicals, pharmaceuticals and food products.
The eddy mixing current in NiTech technologies is propagated downstream by the incompressibility of a fluid or a mixture of fluids; therefore, the dominant phase in any chemical processes must be aqueous. The viscosity of the main phase should generally be lower than 300 cP. A second phase of either solid slurry, gas or liquid of various viscosities can then be added along the length of NiTech reactors, depending on their physical properties, e.g. typically 25% w/w of solids, and 10% v/v of gas.
NiTech technologies are suitable for processes of liquid-liquid, solid-liquid, some gas-liquid, and some gas-liquid-solid processes, e.g. hydrogenation.
Yes, because the mixing is uniform, the shear rate is lower than that generated by impellors, which is good for shear-sensitive cells.
Yes, NiTech technologies enable light provision in direct contact with process fluids along the reactor, this allows the delivery of a combination of increasing or decreasing or constant light intensity and wavelength along the reactor, achieving controlled photo-catalysis or reactions.
NiTech crystallisers are suitable for anti-solvent and cooling crystallisation processes. In terms of cooling crystallisation, it offers the simultaneous control of scale, independent mixing and temperature distribution that cannot be achieved in traditional batch crystallisers. In terms of anti-solvent crystallisation, NiTech crystallisers provide intensive mixing at the point of contact between solvent and anti-solvent, are able to suspend crystal particles evenly along the crystallisers, leading to narrow crystal size distributions. NiTech crystallisers are, however, not suitable for evaporation crystallisation.
Encrustation is caused by uncontrolled nucleation, often when the metastable zone is crossed randomly in batch industrial-scale crystallisers or when the combination of seed properties (seed mass and seed size) is incorrect.
Seeding is the norm in most pharmaceutical manufacturing processes to overcome unexpected and uncontrolled primary nucleation from happening. Likewise, spontaneous nucleation should generally be avoided in NiTech crystallisers, except for some inorganic crystallisations. Encrustation can be completely eliminated with the correct combination of seed size and seed amount.
Yes, the same NiTech unit can do both reactions and crystallisation, where one temperature zone is normally used for reactions, several temperature zones are created in crystallisation. For reactions, reactants can be added into a NiTech reactor at different locations along the length of the reactor, either collectively or individually. Products can also be removed in-situ during the reaction or at the end; this adds to the flexibility. For crystallisation, seeds can be precisely added just after the saturation – linking crystallisation science with operation.
It is the combination of uniform mixing and temperature control that is the essence for both reactions and crystallisation.