Putting the brakes on the gas hike

Just as the world’s major economies are emerging from a once-in-a-lifetime pandemic, there has appeared an unforeseen spiralling of energy costs, headed by unprecedented increases in the price of natural gas. The widespread use of gas for electricity generation means that there is a knock-on effect on the price of electricity. This threatens economic growth everywhere and could trigger a universal rise in inflation. It might cripple organisations involved in laundering and textile care if it is not addressed promptly and imaginatively. This month we look at how this could be tackled, with emphasis on the immediate production and engineering actions that will reduce the impact.

Strategic approach to the Problem

The first step is to acknowledge that there is a problem and that this cannot simply be delegated to others, either on the staff or elsewhere. It should be addressed by Owners and by Boards of Directors of laundries and rental operators themselves, recognising that there is much to be done to mitigate the drain on cash and reduced profitability. The responsibility for organising this should come from senior level and cascade down to all levels of the business.

Every member of staff has a part to play and exactly what is required of each person needs to be identified and communicated to them. The advice which follows might not be complete, but it provides a robust starting point and might trigger more innovative ideas from the laundry floor.

Laundering is energy intensive, but in most laundries around 90% of this is in the form of heat energy and only 10% is electric power used to drive motors or light the workroom. So, it makes sense to concentrate on heat energy and to recognise where the shrewd use of extra power can save significantly more heat energy. Examples of this follow and demonstrate the benefits of getting spin times right; and increasing the time at full pressure in the membrane press.

Sorting

Full loads are essential, because the unit cost of washing part-loads is much greater in energy terms. Start by calibrating the weigh-scales, check that the discharge weights are clearly and correctly marked on the scales and that every operative in the department understands the importance of their contribution.

A full load of cotton goods equates to a loading factor of 10 litres cage capacity per kg of dry textiles. For polyester blends this might need to be increased to 12 litres or more to avoid poor soil removal and excessive creasing, but you need to determine the correct maximum load factor for your operation and see that it is adhered to.

Used towels may pose a particular problem in every laundry, because they carry moisture from the person who has just dried themselves. This means that the correct weight of dry textiles is more difficult to estimate. The best way of doing this is to reweigh a number of test loads after they have been fully dried to bone-dry and compare this with the wet weights. You can use the formula:

Moisture in the wet towels = ((Wet weight – Dry weight) ÷ (Dry weight)) x 100%

For example, if the wet weight in sorting = 121.2kg and the bone-dry weight = 99.1kg, then the moisture in the wet towels was ((121.2 – 99.1) ÷ 99.1) x 100% = 22.3%. If your average moisture percentage is over 20%, then you can safely load your 100kg washer to 120kg of used towels, knowing that this represents less than 100kg of dry textiles. You must, however, check this every week or so to ensure that you never overload you washers. The net result is to lower the unit wash energy by around 20% for every batch of used towels, which is a prize well worth having, even with low temperature washing.

Washer extractors

Check the running dips for each main wash in each washer extractor and move them towards the recommended dips set out many years ago in the BLRA (British Launderers Research Association) handbook. These use the minimum water and minimum heat energy consistent with efficient washing. This step usually saves a useful amount of gas energy, especially if these vital checks have not been done recently.

If you are currently operating with some main washes above 40C, then you should urgently investigate low temperature washing with your chemicals’ supplier. Modern processes have been developed which remove both protein and vegetable dye stains and soiling at reduced temperatures and you cannot afford not to consider these. You need the modern chemistry – don’t just drop the temperature and hope for the best, because this will only increase you rewash!

Hydro-extraction performance in the washer-extractor is critical to gas consumption in the tumble dryers. You need the final extract time to be such that increasing this by another 30 sec does not remove any more moisture. In energy terms, it is fifteen times more expensive to tumble dry one litre of water from the textiles than it is to squeeze it out in the final spin! Time spent optimising the spin time for every classification is worth every second, however tedious it might seem at the time!

Tunnel washers

The suggestions already made about load weights and the adoption of low temperature washing apply equally to CBTWs. These will make significant savings in a great many plants. You should also verify that you are operating at the minimum necessary water flow into the main wash zone. Check first that the water meter which displays this is clean and free from debris, slime and biofilm - otherwise it will not display the correct flowrate. Then discuss the minimum setting with your chemicals' supplier. You should also consider whether the change to a premium detergent system will give you any benefit. The change to the low temperature system itself could well enable a lower flow, especially if the modern system has better emulsification, stain digestion and suspension properties.

Hydro-extraction in the membrane press is a sadly neglected area and a vital target for saving gas energy downstream, in the dryers and ironers. Even the ironer requires five times more in heat energy than the membrane press does, per litre of water squeezed out or evaporated. Typically, you should be aiming for at least 30 sec at full pressure with a 40 bar press and if you are still operating with an old press at 20 to 30 bar, then you should try to tune this to give you 60 sec. This could mean adjusting the wait times in the press computer program, which takes time and concentration, but again it is worth the effort and must be tackled.

Tumble dryers

The loading of the dryers is as important as that for the washers, but most laundries have dryer capacities to exactly match the wash load weights, so this should not be a problem. Having a reliable and constant load weight greatly assists the setting up of the dryer times to give just-dry towels every time, with no over-drying and the greyness and harshness which accompanies this. Even more importantly, this minimises the gas consumption.

However, those dryers that are fitted with automatic cycle terminators have a distinct advantage, because they do not rely on perfect load weight estimation or even perfectly tuned hydro-extraction. They are designed to sense the moisture content of the drying towels in the rotating cage and terminate the cycle at exactly the right point. Setting them up is critical to this because they have to be correctly aligned and tuned to the right final moisture content (which is usually just above zero) and they have to make allowance for the cool down.

Ironers

Ironers have a typical thermal efficiency of around 95%, depending on insulation, productivity and idling time. This compares with efficiencies of 25% to 55% for tumble dryers, depending on design, maintenance, load factor and idling time. This means that taking flatwork to be ironed straight from the washer extractor to the ironer, cutting out any conditioning in the tumbler, saves appreciable gas energy. Any loss in productivity on the ironer can usually be compensated for by edge to edge feeding and having all lanes in use, keeping the ironer running normally as a priority. We will be giving tips for maximising ironer output in a future issue of LCN.

Tunnel finishers

Modern tunnel finishers are generally energy efficient designs, with limited scope for massive improvements in energy economy. However, they are sometimes run intermittently and often underloaded, especially in mixed laundries. To get the best out of the substantial amount of gas needed by a modern tunnel finisher, it is generally best to assemble the work for the shift before starting the machine up, then load one garment per peg, process the batch and shut down if there are no more garments immediately available.

Energy economy is frequently governed by the recycle setting on the air circulation damper - the greater the amount recycled, the higher the thermal efficiency. If the garments are coming out damp, then the obvious solution is to reduce the recycle, but a better option from an energy point of view is to slow the tunnel slightly, if a slightly lower output rate can be tolerated.

Energy recycling

There are a variety of options for recycling laundry energy, but these generally involve investment and time for manufacture, installation and commissioning. In the meantime we have concentrated in this month’s Material Solutions on actions that can mostly be undertaken immediately at little or no cost. Remember in most countries the best laundries use only 40% of the energy per kg textiles demanded by those that are less well equipped and poorly managed! This is a massive difference and shows the potential! Good hunting!