(Akiit.com) In terms of technology, dry scrubbing is one of the newer types available to businesses today. This is a control technology that tends to be used on municipal waste incineration and pulverised coal-fired boilers. What is its purpose? Well, a dry scrubber removes acidic gaseous pollutants from the gas stream, the most common of which being sulphur dioxide (SO2), hydrogen fluoride (HF) and hydrochloric acid (HCI). The technology utilises adsorption and absorption in order to achieve this separation. In fact, you can also get some dry scrubbers that actually absorb metallic compounds and vaporous organic compounds. Nonetheless, their main objective is to deal with acidic gaseous pollutants.
Before delving deeper into the operation of a dry scrubber it is worth elaborating further on what adsorption is and what absorption is as these two words are crucial in understanding the dry scrubbing technology. Firstly, absorption relates to the dissolving of a gas in a liquid solvent. On the other hand, adsorption describes the process of gases being removed from a gas stream by allowing the pollutant molecules to be attached to the surface of a solid. By understanding the two concepts you should now already have a better idea of the processes involved when a dry scrubber is in operation.
Nevertheless, let’s dig a little bit deeper and reveal the exact operation. When a dry scrubber is in use an alkaline reagent will make contact with the acidic gas stream. This alkaline reagent will be in droplet form. The way it works is through either adsorbing the pollutants in the gas stream or absorbing them – one of the two processes that have just been mentioned. After this, the droplets that contain the pollutants are then dried and they will be collected. There are various ways of doing this, however, you will typically find that most are done in a fabric filter or an ESP.
There are lots of different dry scrubbing techniques being utilised by companies at the moment, which are being integrated with other stainless steel industrial products. Many professionals state that the reason why this is the case is that the technology is relatively new and therefore there is no real standard process in place. The three main techniques used at the moment are as follows; spray dryer absorption, dry injection adsorption and a combination of the two. So, what makes these techniques differ from one and other? Well, the main divergence is in relation to the alkaline reagent which is utilised. Both in terms of its physical form and the way in which the system brings the reagent into contact with the gas stream. In addition to this, the dry injection adsorption techniques make use of more alkaline reagent in comparison to the other two.
To conclude, dry scrubbing is an advanced control technology that is evolving by the day. More and more businesses are making use of a dry scrubber and the feedback has undoubtedly been positive due to the high-efficiency levels associated with the technology. Furthermore, there are CEMs (continuous emissions monitors) in place which can tell you how well your system is performing.
Staff Writer; Roy Brown