AM Technology's continuous reactor a 'beautiful solution'

The ACR is a multistage continuous stirred tank reactor (CSTR) the size of a kitchen microwave for reactions taking between 10 seconds and over 100 hours. Continuous reactors have shown a great deal of potential for applications within the pharmaceutical and speciality chemicals industries. However, until now progress has been held back by shortcomings. Speaking to in-PharmaTechnologist.com AM Technology founder Robert Ashe said the intention when developing ACR was to create a reactor which competed "with oscillating flow reactors (OFR) and traditional multi-vessel CSTR but was much simpler and cost less than its competitors​." The need for constant fluid motion of around 0.5 m/s means traditional continuous reactors become too large to perform slow reactions. OFR's were an attempt to solve this problem but suffered from high levels of axial mixing and were still quite large. Consequently traditional CSTR's were regarded as the best way to perform slow reactions owing to the systems very efficient radial mixing, low axial mixing, flexibility and very low pressure drops. Unfortunately, they are also very expensive and complex, owing to the multiple vessels, agitator motors, shafts and seals that were required for multiple reaction stages. AM Technology sought to solve these problems and create a reactor which was "simple and configurable with excellent cooling,​" according to Ashe. To simplify the problem the ACR uses a series of ten reaction cells linked by channels cut into a metal block instead of multiple reaction tanks. One side of the metal block is a cooling plate to facilitate heat transfer. The reactive mixture flows through channels to the cells sequentially. Within each cell is a free moving agitator element which is shook by mounting the reactor on a vibrating platform. The largest agitator is put in the first cell and they then sequentially decrease in size. This modifies the cell size to avoid the difficulty created by the first few seconds of the reaction being very fast. The fluid spends less time in the smaller cells which negates the effect of the initial reaction rate being very high, ensuring a uniform level of reaction in each cell. When draining the mixture the cell block oscillates, so that the product that entered the reactor first, leaves it first. This is performed without the need for flush fluid and ensures that almost 100 per cent of the product is recovered, an important consideration when dealing with valuable material. The design of the ACR gives it the capacity to perform organic and inorganic reactions, with either homogenous fluids or fluids entrained with gases or solids. If a large solid load is required reaction blocks with larger inter cell channels are available. All these features fit inside a box the size of a kitchen microwave. Considering this Ashe's description of the ACR as a "beautiful solution​" to the problem of continuous reactors appears devoid of hyperbole.