Air Purification Blog

Updates and news about Puravents range of air purifiers, in duct UV systems, infection control, odour treatment and in room air purifiers.

Sanuvox Quattro is the ideal basis for an 
ethylene removal system

Ethylene Removal by UV

Ethylene removal Background

Ethylene removal by UV might seem like a strange title, but Ultra Violet Light is an effective method of controlling  ethylene in fresh produce storage and processing facilities.  Like other more traditional technologies like dry chemical scrubbing, the UV installation needs to be properly engineered and set up, but once in use the big benefit of using UV is its very low running costs.

Fruit cold store

Fruit cold store

The storage and processing of fruit and vegetables is a finely orchestrated battle against time. Most products do not linger in storage for long and in many processing facilities the time spent from ‘goods in’ to ‘goods out’ is measured in minutes, rather than hours. The investment in machinery to make this slick process so effective can not be jeopardized by anything that can have an adverse effect on the self life of the finished product. Competitive advantage is defined by freshness, speed from field to shop and shelf life.

Ethylene produced by the decomposition process in fruit and vegetables in turn stimulates decomposition in fresh produce, and it is vital that where unprocessed produce is held in storage ethylene is controlled, to ensure that the freshness is preserved and that waste from the process is minimised.

Ethylene removal the old way

Traditional ethylene removal often uses dry chemical scrubbers. These machines generally have a prefilter, a chemisorption bed and an after filter. These stages make for quite a high pressure drop for the onboard fan to overcome in order to move sufficient air through the machine. With any system using a fan, pressure drop has a direct effect on running cost related to electricity consumption. The power costs, replacement dry chemical media costs and the down time cost of changing the filters and media, make the overall running cost of the traditional scrubbers relatively high.

Ethylene removal the UV way

UV ethylene removal is totally different, and is ideally suited to the cool, humid environments typical of fresh produce storage. UV light at 187nm wave length is very effective at oxidising airborne chemical contaminants such as ethylene. The key is to ensure that there is the correct balance between the intensity and exposure of this wavelength UV and the volume flow of air being treated.  187nm is known as UVV light, and it has the characteristic of making oxygen react with chemical contaminants and in treating ethylene, it oxidises to produce carbon dioxide and water vapor.

 C2H4 + O*  CO2 +H2O

Cold room with evaporator cooling. One option for treating Etylene is to fit UV system inside

Cold room with evaporator cooling. One option for treating Ethylene is to fit UV system inside the evaporator housing

Using UVV for ethylene removal is easy and there are generally two methods.

Firstly the UV lamps can be incorporated into existing chillers or air handling units serving the room. In this method the spliced lamps are

coil cleaners in evaporator box

coil cleaners in evaporator box

arranged to bask the cooling coils in UV light, which not only ensures that ethylene that passes through the coils is oxidised, but also ensures that the UVC light which is germicidal, prevents any biomass slime forming on the coils.

 

Sanuvox Quattro is the ideal basis for an  ethylene removal system

Sanuvox Quattro is the ideal basis for an
ethylene removal system

The second method is to use a UV lamp array such as a Sanuvox Quattro or Biowall in a purpose-built scrubber. Unlike the dry chemical scrubber these units are quite lightweight and are usually assembled from standard ducting components and ancillaries. The UV lamps in this case will also be ‘spliced’ thereby combining the germicidal merits of UVC light and the ethylene oxidising property of UVV light. The scrubber complete with its own axial fan and inlet filter is usually suspended from the ceiling or can be mounted above the ceiling with just inlet and outlet grilles showing inside the room.

Ethylene Removal System suspended  from roof structure

Ethylene Removal System suspended from roof structure

Because the upsizing of UV based ethylene removal systems is relatively cheap there is every reason to provide sufficient sizing for these systems for any given application from the start. In Contrast dry chemical scrubber systems  are heavier and more expensive which creates the temptation to cut corners in design and sizing.

Ethylene removal by UV also has much lower associated pressure drop through the scrubber so that even when the power of the fan is combined with that of the lamp ballast the power consumption will typically be only 1/5th or 1/6th of that used by a chemical scrubber handling the same airflow.

Maintenance is an important consideration and although lamps will periodically require changing, it is a very easy, quick and clean procedure. UV based systems ensure that it is not just an ethylene removal system. The germicidal UVC part of the lamps will ensure that airborne spores bacteria and viruses are controlled as well – something that dry chemical scrubbers just don’t do.

Ethylene Removal with UV  – Summary

UV based ethylene removal uses both UVV and UVC, which means that it not only removes ethylene but also controls airborne fungi mould and spores. This means that as well as the stimulant for ripening being controlled but also the biological contaminants associated with rotting are controlled. Ethylene removal with UV is;

  • Very effective
  • Clean – does not cause dust
  • Low running cost
  • Easily scalable
  • Easily maintained
  • Can be controlled by gas monitors
  • Can be linked to BMS
  • Is suited to humid environments
  • Also controls biological contaminants
  • Can be fitted within evaporator housings, or free hanging

For further help on ethylene control, call us –  01729 824108

 

UV Air Purification. In this case UVV and UVC lamps used in a combined system

UV Air Purifiers

UV Air Purifiers and its Application

To achieve biologically and, or chemically clean air, UV air purifiers are the answer.  In this post we reproduce our article that was originally published in MBS magazine in 2008. It is as relevent now as it was then. In  the meantime if you need help with engineering a system based on UV air purifiers then call us 01729 824108 or our UV products are here.

“In North America, UV air purifiers for preventing fouling on cooling coils and drip pans and for the treatment of odours and micro organisms in ducted air is common place. Not only is the technology a specified requirement for air handling units entering service within American public sector buildings, it has even been tested and found to be effective by the US National Homeland Security Research Centre, at defending building occupants against bio-terrorism. Now that the technology is detailed in the ASHRAE handbook, it warrants closer examination in Europe.

Technical Rudiments
Within the UV light spectrum, the wavelength 254nm is known to be particularly effective at killing or inactivating micro-organisms. It is utilised by ultraviolet genocidal irradiation (UVGI) systems, where the effect on micro-organisms, including bacteria, viruses and spores, is that it penetrates the organism’s cell wall and damages the DNA, preventing cell division reproduction; certain doom, given their short lifespan. Another useful UV wavelength is 187nm, which is sometimes known as UVV and is used for UV photo oxidation of airborne chemicals and odours. UVV produces ozone, oxygen singlets and hydroxyls (O3, O and OH), which although excellent for treating airborne odours and other chemicals, can leave harmful concentrations of residual ozone being supplied to occupied spaces. For this reason UVV is only used if followed downstream by and interlocked with, a UVGI system which acts as a catalyst reverting residual O3 safely back to O2. Within ducted systems, UV comes in two main guises.

UV Air Purifiers. In this case UVV and UVC lamps used in a combined system

Two UV air purifiers used in series, UVV and UVC combined for both biological and chemical challenges

For treatment of odours and chemicals UVV and UVGI lamps must be used in combination.

Coil Cleaning
Firstly UV lamps arranged to bathe the cooling coils and drain pan of an air handling unit in UVC light is used to prevent the build up of mould and slime. Left unchecked the cool, wet surfaces present an ideal breeding ground for biomass, blocking fins and reducing thermal efficiency, and creating a source of biological contamination easily picked up and vented to rooms. UV coil cleaners prevent this biomass with the economic benefit that the initial efficiency of the coils is maintained and the costs and down-time associated maintenance and coil cleaning are eliminated.”

 

 

 

 

Air Purifier or Air Cleaner – Its a definintion thing

It’s reasonable for a layman not to know the difference but,  surprising when even people in the industry don’t appreciate the difference.  What on earth am I babbling on about?

Air Purifier or Air Cleaner?

Generally speaking the layman will use ‘air purifier’ as their description of what they are after and generally speaking suppliers of these machines will quietly assume that the layman may be looking for either an air cleaner or an air purifier, then ask a few questions in order to discover which.

Just in case you don’t know, air purifiers work at a molecular level and in broad terms tinker with the chemistry of the air, or indeed the DNA of micro organisms, and air cleaners move air through a filter medium or mechanism to remove particles and or droplets.  Basically;

  • Air cleaners – remove lumpy stuff and droplets.
  • Air purifiers – alter chemistry and biology

I nearly fell off my chair when I read a brand new manufacturers brochure (old expensive paper type) where consistently air cleaners were being described in print, as air purifiers. Now as one of the biggest manufacturers in the market this may be viewed as a surprising error. Actually no. The surprising thing is that it was a printed mistake. If it had been a webpage or pdf file then no mistake. You see this is one of the many examples where web search traffic is driving the development and meaning of language.

I mentioned the layman earlier. If fault has to be laid down somewhere, it is at the layman’s door. Because people search for ‘air purifier’ more than 10 times more often than ‘air cleaner’, irrespective of what they are actually looking for, suppliers keen to have their products found in the market, wrestle with the problem for a few moments and then relabel their air cleaners as air purifiers. This over time reinforces the use of language as browsers are rewarded with the numerous  air cleaners (labeled as air purifiers) and actual air purifiers.

So whats next? There is no doubt that ‘air cleaner’ is becoming a term of the past, and it will come to pass that air purifiers will be subdivided into air cleaners, Ionizers, UV air purifiers etc.  As pig headed traditionalists we will continue to buck the trend and refer to air cleaners as air cleaners, but whether our market will know what we are on about is another matter. Feel free to visit our website for more information on products and services.

 Air Purifier or Air Cleaner

LiveZilla Live Chat Software