Ultra Loq Liquor Ratio Myth and Facts

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Ultra-low liquor ratio: Myths & facts

Ever since the arrival of THEN-AIRFLOW® technology and its extremely low liquor ratio of 1:3.5

for cotton fabrics, the number of dyeing machines for which their manufacturers claim “LLR” (low

liquor ratio) or “ULLR” (ultra-low liquor ratio) has mushroomed.

Suddenly, even basic conventional hydraulic machines have

turned LLR or even ULLR – at least in their promotional

literature. However, as with most things in life, if something

sounds too good to be true, it usually is.

This article discusses points to keep in mind to avoid being

rumbled by fantastic claims, and highlights the paramount

practical importance of water consumption per kg of fabric

processed for dye house economics.

Definition of “liquor ratio”

Liquor ratio describes the weight of goods processed vs the weight of the dye solution, whereby

the former is usually expressed in kilograms (kg) and the latter in litres (l). The practical

assumption is that one litre of dye solution weighs one kg.

Thus, for a load of 1,000 kg of fabric, a total liquor requirement of 3,500 l will result in a liquor

ratio of 1:3.5. This happens to be the typical liquor ratio of an AIRFLOW dyeing machine for

cotton. For synthetics, liquor ratios as low as 1:1.5 (for very fine PES fabrics) have been

achieved.

How to calculate your actual liquor ratio

Example 1:

Load of 500 kg of cotton fabric with a 270% pick-up in THEN-AIRFLOW® SYNERGY 500 machine

Table 1: Liquor ratio calculation for fully-loaded THEN-AIRFLOW® SYNERGY 500

machine

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This example illustrates the minimum amount of liquor in circulation in the AIRFLOW machines. However, the low liquor ratio

can be sustained even when underloading an AIRFLOW machine, as illustrated in the next Table.

Example 2:

Load of 250 kg of cotton fabric with a 270% pick-up in THEN-AIRFLOW® SYNERGY 500 machine

Table 2: Liquor ratio calculation for THEN-AIRFLOW® SYNERGY 500 machine with 50% load

In this example, the liquor required to compensate for the fabric pick-up drops by 50% -- commensurate with the 50%

decrease in load. The liquor required for circulation in pipes and used for chemicals additions can be reduced by 50 l, as

chemicals consumption is reduced in line with the lower load, too. It illustrates quite dramatically why dyers with AIRFLOW

machines remain highly competitive even when faced with loads that utilise even just half of the installed machine capacity.

How is it possible to run such low liquor ratios, even when the machine is underloaded by 50%? The secret lies in the unique

and patented THEN-AIRFLOW® concept.

The THEN-AIRFLOW® design principle

The key element in AIRFLOW technology is a stream of air, which represents the perfect transport medium. The use of air

instead of dye liquor to transport piece goods in jet dyeing machines is a patented, pioneering achievement from THEN. As

compared to jet nozzles, covered with dye liquor, pressure is negligible, which means that the sensitive surface of the fabric

is ideally protected. At the same time, the use of the air flow principle results in far superior laying of the material rope,

which prevents the formation of creases.

Figure 1: Patented THEN-AIRFLOW® machine design. Liquor circulation is shown in

air flow is shown in BLUE.

Item Unit Value Loading of machine kg 500 Liquor required @ 270% pick-up

litres 1,350

Liquor circulating in pipes and used for chemicals additions

litres 400

Total litres 1,750 Practical liquor ratio 1:3.5

Item Unit Value Loading of machine kg 250 Liquor required @ 270% pick-up

litres 675

Liquor circulating in pipes and used for chemicals additions

litres 350

Total litres 1,025 Practical liquor ratio 1:4.1



Figure 2: Patented THEN-AIRFLOW® machine in cross-section. Liquor circulation shown in RED; air circulation shown in BLUE.

Note absence of dye bath in vessel.

Note in the images above that there is no dye bath in the bottom of the dyeing vessel. AIRFLOW technology instead has all

liquor dripping inside the vessel immediately returned back to the AIRFLOW injection nozzle, via a sump filter. The air is

returned from inside the vessel back to the blower. No fresh outside air is sucked in, so the pressure inside the dyeing kier

remains constant.

In contrast, all other hydraulic and hybrid hydraulic-air systems are based on the mandatory presence of a dye bath and the

use of an overflow jet to inject liquor into fabric. Even if the depth of the dye bath in such machines measures only a couple

of inches, the actual volume of liquor will in principle preclude any liquor ratio even remotely close to that of the AIRFLOW

system, which generally operates with a liquor ratio of only 1:3.5 for cotton, and only 1:2.5 for polyester. This low liquor ratio

can be sustained even when underutilising the vessel, because the total liquor volume required depends almost entirely on

the take-up of the fabric. There is only around 100 to 200 litres of liquor required for circulation (ie, in pumps and

port, and no requirement to fill a dye bath.

Why many dyers remain in the dark about their true liquor ratio

It is not unusual for dyers to challenge these figures – not disputing their accuracy but their uniqueness. Some claim that

their conventional hydraulic machines or even hybrid hydraulic-air machines achieve similarly low liquor ratios. However,

these claims are almost always made without any accurate means of recording the exact amount of water used for each dye

batch – let alone for each process step. Unless a water metre is fitted and each process step is precisely recorded, there is no

scientific way to establish the true liquor ratio in an installed dyeing machine. And since the dye bath is located at the very

bottom of the dye vessel and thus literally in the dark, its true volume is rarely visualised.

Once a water metre is used to monitor a dye process in a conventional hydraulic or hybrid hydraulic-air machine, what was

once praised as a LLR (low liquor ratio) or even ULLR (ultra-low liquor ratio) becomes a very ordinary figure that is easily

surpassed by THEN-AIRFLOW® machines.

It is also not uncommon to encounter liquor ratio calculations that are based on assumed (and optimistically low) fabric pick

up rates – or even their complete omission. In this case, only the amount of liquid required for circulation plus chemicals

additions is considered for calculating liquor ratio. Clearly, any dyer ignoring the amount of liquor going into fabric pick

exposes himself to a very costly illusion.

THEN-AIRFLOW® machines are fitted as standard with controller software that automatically identifies the true fabric pick

rate and tops up – if necessary – the amount of liquor in circulation to prevent pump cavitation.

What can be more important than liquor ratio?

Whilst the liquor ratio is justifiably seen as very important and thus used for even very extravagant claims by promoters of

conventional hydraulic and hybrid hydraulic-air machines, the decisive factor of how profitable a dyeing machine operates is

its overall water consumption per kg of fabric dyed.

In the liquor ratio argument, which AIRFLOW technology easily wins, the focus is on the quantity of dye liquor vs the weight

of processed fabric. However, apart from dyeing, there are other highly water-consuming steps involved in the overall dyeing

process, such as rinsing. Thus, overall water consumption, expressed in litres (l) per kg of fabric, is even more important

when it comes to establishing how economical and ecologically friendly a dyeing process really is.



Here, too, THEN-AIRFLOW® technology offers impressive system-inherent advantages and benefits, as it allows for an instant

hot drain of dye liquor immediately followed by a “variable power rinse” cycle. In this process step, all dye liquor is drained off

instantly, and rinsing water is showered onto the circulating fabric. As there is no liquor bath in the bottom of any AIRFLOW

machine, the fabric does not drag dye liquor back through the rinsing cycle at any time, thus minimizing rinsing time and

water consumption, as the circulating fabric is not recontaminated with dirty water.

Liquor ratio vs. specific water consumption

Typical water consumption figures for cellulose fabrics (depending on dyestuffs and other parameters) on THEN

machines are:

Bleaching: 11 – 12 l/kg

Light shades: 25 – 33 l/kg

Medium shades: 33 – 38 l/kg

Dark shades: 38 – 50 l/kg

These figures are about 50% lower than those for any other hydraulic or hybrid hydraulic-air machine, and about 75% lower

than those achieved by long-tube jet dyeing machines. And they corroborate the exceptionally low liquor ratio figures attained

by the AIRFLOW system.

Lower water consumption also means lower consumption of eg, steam, salt and other chemicals, plus a much reduced volume

of effluent discharge Under Indian operating conditions, this translates into savings of up to Rs 10 per kg of processed fabrics,

when all is factored in. In an operation dyeing 10 tons per day, this represents up to Rs 3 to 4 crores!

Summary

THEN-AIRFLOW® technology, used worldwide by dyers operating some 2,000 machines, offers the only ultra

in jet dyeing today. This unassailable position is a direct result of its technology that completely does away with a dye bath.

But beyond this, its specific water consumption is dramatically low, too, and this is the figure that determines how profitable

the dyeing process really is. Given today’s water scarcity in many areas and ever higher demands on effluent treatment,

AIRFLOW technology is now rightly emerging as the key to profitable fabric processing in India.

(For further information, contact: Kurt Müller, Area Sales Director, THEN Maschinen GmbH (A Member of Fong's

Industries Group), Milchgrundstraße 32, 74523 Schwäbisch Hall, Germany. Tel: +49 (0)791 403

(0)791 403-166. Cell: +49 (0)173 31 80 890. Email: [email protected]. Web: www.then.de)

published September , 2008

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Ultra Loq Liquor Ratio Myth and Facts