Disadvantages of Airlift Reactors

Airlift reactors have been widely applied for a wide range of different chemical and biological processes thanks to their numerous benefits. Nevertheless, as all different technologies, airlift bioreactor have some downsides too, which limit its applicability and efficiency. In, we will discuss limitations and drawbacks of airlift reactors, which should be borne in mind when working with this technology.

Advantages Explained

The high energy consumption by airlift reactors can be mainly attributed to the high hydrostatic pressure gradient within the reactor. Hydrostatic pressure gradient refers to the pressure gradient developed due to the liquid height within the reactor. This pressure gradient adds up to the pressure drop experienced by the gas bubbles in the liquid phase. This pressure drop thus produced requires much energy to sustain the circulation of the gas-liquid phase within the reactor.

The limited mass transfer rates experienced in airlift reactor result from the minimal interfacial area at which mass transfer occurs. The interfacial area is the surface area between the rising gas bubbles and the surrounding liquid phase. The interfacial area in airlift reactors is limited since there exists a dense liquid phase that reduces free surface area available for gas-liquid contacts.

Problems and Concerns

There are also some operational issues that should be tackled by airlift reactors. The fouling of the gas sparger is among those. The gas sparger is the sparger used to inject the gas into the liquid phase. Particles or biofilms in the airlift reactors easily plug up the gas sparger and reduce the mass transfer rates for gas-liquid as well as increase the pressure drop.

Another operational problem is flooding. Flooding occurs when the liquid phase reaches the top of the reactor. This causes gas-liquid disengagement and loss of circulation. Flooding is expected to be higher when the liquid height increases and gas flow rate is increased. In order to avoid flooding, airlift reactors should be operated at a very narrow range of liquid height and gas flow rate.

Negatives and Pitfalls

Some limitations and problems with airlift reactors are as follows; which may impact the airlift reactor’s performance or efficiency. The airlift reactor tends to be more energetic in consumption; thereby, this can be comparatively less economical for reactors concerning other reactors. Its relatively small mass transfer rates will become limited by some processes as these require a large area of the interface for transferal.

Operational problems are also causing a decrease in the efficiency and dependability of airlift reactors. Fouling of the gas sparger and likelihood of flooding may reduce the rate of mass transfer between gases and liquids and lead to loss of circulation and lesser product quality. All this increases maintenance expenses and decreases time, so the whole system is reduced in economical feasibility.

Conclusion In a nutshell, airlift photobioreactor are both advantages and disadvantages. The shortcoming and drawback aside, airlift reactors are a good alternative to chemical and biological processes in certain processes. Nevertheless, one has to put these considerations in mind: the energy consumptions, poor mass transfer rates, and other operating problems. And in doing so, the problems being faced can be overpassed in such reactors for chemical and biological industry use.