Has chlorine bleach had its day?24 May 2022
Richard Neale of LTC Worldwide finds modern solutions that make the use of chlorine bleach obsolete in sustainable laundry operation. Overleaf he presents a strategy for tackling rising gas prices
Chlorine bleach (sodium hypochlorite solution) has been the most common de-staining agent worldwide for all sectors of the commercial laundry industry – retail, commercial, industrial and healthcare. For very good reasons, chlorine bleach was first removed from the healthcare sector and other sectors are steadily following suit. This month we look at the benefits this is bringing.
Effectiveness as a bleach
The reasons why chlorine bleach was once so popular are because in most situations it is a very effective de-stainer, it is inexpensive, and it is widely available. It is a very strong oxidising agent, which reacts with vegetable dyes such as those found in blackcurrant, red wine, beetroot, beer, grass, and a whole host of similar substances which came from plant life. Chlorine bleach will decolour these substances at low concentrations (150 parts per million (ppm) in a short time (3 minutes) at low temperatures (30- 40C).
Dangers of using chlorine bleach
So, what’s not to like?
Splash risk: chlorine bleach is usually purchased at 15-16% strength, but even at 5% a minor splash to the eye can result in severe eye damage very quickly, because of its corrosive effect on human tissue. Laundries need plenty of local eye wash facilities, trained first-aiders and good staff training to cope with this. Even a splash to the hands or face can cause painful injuries quite quickly. For many years, the risk has been reduced by automatic dosing, but tube leakage (leading to sprays) and drum handling incidents have still occurred occasionally.
Inhalation risk: chlorine bleach gives of an odour of chlorine gas, which is poisonous. This risk is relatively insignificant in the open atmosphere of the laundry workroom, but in an enclosed space (such as in a blocked rinse zone in a tunnel washer) it can be, and has been, fatal. Special procedures and training systems have been extensively developed to deal with this risk.
Over-dosing: chlorine bleach is very effective on vegetable dye stains at low dosages, but it is only effective on protein stains (from meat fats, blood, vegetable oils and so on) at much higher dosages. There has therefore been an understandable and often irresistible temptation for laundry operatives and even more senior laundry staff to deal with stubborn protein stains by using much higher dosages. This has resulted in much reduced textile life for restaurant linen (and even cotton and polycotton food industry workwear). The latest research on detergent systems has produced modern processes which remove protein stains effectively, even at low temperature (40C), but old habits die hard! Textile life across the entire rental sector in some regions is only a fraction of what it should be, with a major impact on sustainability and associated causes of climate change.
Bleaching at the wrong temperature: at one time, the addition of chlorine bleach to the hot wash at 70C was not that uncommon, because the laundry had discovered that the stain removal was apparently faster and more powerful and included protein stains! This might have been true, because raising the temperature does usually speed any chemical reaction, including that of bleach with a vegetable dye. However, it is also accompanied by massive chemical damage and once rental operators found the effect this was having on their textile injection costs, the practice subsided. Of more concern is the failure in many laundries of dosing chlorine bleach into their tunnel washers but failing to check that the bleach had been exhausted before the rinse water was recycled into the hot wash!
Effect on textile life: misuse of chlorine bleach has been possibly the major historical contributor in the rental sector to failure to achieve an average textile life in excess of 200 wash and use cycles. One leading quality supplier to the London contract laundry market reported average textile lives in excess of 300 wash and use cycles, even with delicate textiles and very critical customers, so 200 cycles is not that difficult to achieve The problem stems from the fact that chlorine bleach weakens cotton, so its use has to be professionally controlled and this was not universally achieved.
Chlorhexidine staining: chlorine bleach reacts with chlorhexidine to produce an indelible brown dye stain. Chlorhexidine is the disinfectant widely used across the healthcare sector and it is also found now in a great many retail skin products. As a result, indelible chlorhexidine staining is appearing across the hospitality sector. The only solution is to phase out chlorine bleach across this sector as well.
The inevitable conclusion from this is that for most laundries there are better modern systems which do not involve chlorine bleach.
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STRATEGY FOR INVESTMENT TO OFFSET THE INCREASE IN THE GAS PRICE
In our March issue, we described the no-cost actions to take to reduce the effect of the escalating gas price and we hope that you have been very pleasantly surprised by the effects produced, despite the cost in staff time to implement the recommendations.
Then in April, we described the reductions in gas usage that could be made possible by shrewd investment in energy saving measures. This month we are making some suggestions for the sort of strategic thinking which can be employed to select the most promising combinations of investment capital to create really meaningful improvements. Every laundry is different, but there are some common threads which should be running through your thinking in the boardroom.
Best value for money in heat recovery
Flash steam: if you are still operating a central boiler and intend to continue doing so, then the key first step is to evaluate the amount of flash steam in your condensate main and get a quote for a boiler feedwater pre-heater to utilise the flash to improve your boiler efficiency. This is likely to be worthwhile if you still have steam heated ironers, tumble dryers or tunnel finishers. The saving will be of the order of 10% of the fuel going into the boiler burner, but your laundry engineer should be able to refine this percentage.
Don’t be tempted to use the flash to raise wash water temperatures for the hot wash using your flash steam, unless you cannot use it at the boiler itself, because you have other options for recovering heat into the wash water (from the calender or tunnel finisher exhaust, for example), whereas you are much more limited in ways of raising boiler efficiency.
However, if you do decide to heat wash water with the flash, there are tried and trusted methods, both for washer extractors and tunnel washers. You will also reap the benefit of recovering any leakages of live steam through failing steam traps, which can be just as big a saving as the flash itself.
Tumble dryer automatic terminators: these are almost a no-brain option for any dryer used for full-dry work which you intend to keep for more than, say, the next twelve months. You should get payback within twelve months based on the energy saved, with the additional benefits of improved productivity and better quality (reduced greying and softer texture).
Tumble dryers with intelligent recycle: this was described in last month’s issue and is not a retrofit option. You should take this on board for future dryer purchases.
You might decide to accelerate dryer replacements if you are currently operating steam dryers and could equally well use gas fired ones, because the reduction in operating cost is now much greater with the increasing cost of gas and oil. We are getting to the stage where this difference alone could justify the switch and you should be getting prices and operating cost comparisons as a matter of urgency.
Ironer exhaust and tunnel finisher exhaust: these are energy-rich sources for pre-heating wash water, with proven systems for ironers and a recently announced system for tunnel finishers. Your strategy should be to estimate accurately you wash water requirement and aim to generate a stream at say 45C by warming your soft water supply using heat from the source that most closely matches the requirement.
If you are pre-heating water for a tunnel washer, you might as well use this for the rinse flow, because the energy will all be recycled into the wash zones by the internal recycle flows. You can avoid the risk of setting protein stains in the pre-wash, by ensuring that your feed temperature to the tunnel is low enough to keep the pre-wash just below 40C.
Balancing heat recycle against heat demand: finally, it is worth taking time to ensure that any integrated design to cope with the gas price escalation correctly generates just sufficient heat to meet the needs of the equipment to which it is being recycled. Do not believe a potential supplier’s estimate of the financial saving you can expect , if this is based on the amount of heat created rather than on the amount you can actually utilise!
Priority 1: utilise the flash steam from the condensate return to your central boiler, ideally to improve the boiler efficiency (by about 10%) or alternatively to power the tunnel washer.
Priority 2: aim to generate enough recycled heat from ironer and tunnel finisher exhausts to eliminate the need for steam in the washhouse. This is also the first step in eliminating the need for a central boiler and the wasted energy normally associated with this.
Priority 3: aim to raise the thermal efficiency of your tumble dryers, by fitting automatic cycle terminators, by converting from steam to direct gas firing, or by exploring replacement with the latest dryer designs. Remember that tumblers are the least energy efficient machines in the laundry!