WWW.SA.I-PDF.INFO
FREE ELECTRONIC LIBRARY - Abstracts, books, theses
 
<< HOME
CONTACTS



Pages:     | 1 |   ...   | 38 | 39 || 41 | 42 |   ...   | 83 |

«EUROPEAN COMMISSION Integrated Pollution Prevention and Control (IPPC) Reference Document on Best Available Techniques for the Textiles Industry July 2003 ...»

-- [ Page 40 ] --

These problems were recently tackled by machine manufacturers and dyestuff suppliers. Recent technological developments have decreased specific water consumptions in batch processing to levels more typical of continuous operations. A constant liquor ratio across variable load sizes is now a standard feature of modern equipment for batch processes. Efficient washing techniques have also been especially developed for batch operations (see Section 4.9.1). Furthermore, various functions typical of continuous processing have been transferred to batch machines,

such as (see Section 4.6.19):

· in-process separation of the bath from the substrate · internal separation of process-liquor from the washing liquor · mechanical liquor extraction to reduce carry-over and improve washing efficiency · internal countercurrent flow in the batch washing process.

–  –  –

· by combining processes Combining and scheduling processes reduces the number of chemical dumps. This is often feasible for pretreatment operations (e.g. scouring/desizing, scouring/desizing/bleaching – see for example Section 4.5.3). Combining pretreatment into the colouration stage is also possible in some cases.

Re-using water

Batch processes do not easily allow for water recycling. When trying to re-use waste water in batch operations, storage facilities for re-usable waste water must be provided. Other problems associated with re-use of waste water from batch bleaching and scouring are the non-continuous character of the waste stream and the higher liquor ratios.

Continuous countercurrent flow of textiles and water is now also possible in batch processing.

Machines are now available with built-in facilities for waste stream segregation and capture. For example, the wash water from a previous load can be recovered and fully used in the bleach bath for the current load, which can then be used to scour the next load. In this way, each bath is used three times.

Some examples of water recycling and re-use are reported in this chapter (see Sections 4.6.22 and 4.7.7).

The internal separation of process-liquor from the washing liquor applied to some modern batch dyeing machines (see above) is essential to allow easier bath segregation and re-use, in cases where the characteristics of the liquor make it feasible.

Main achieved environmental benefits Significant savings in water and energy consumption are possible (energy is used to a great extent to heat up the process baths).

Operational data

–  –  –

Economics In existing mills, investment in new equipment and/or structural modifications (e.g. for the segregation of streams) is likely to be necessary.

Reference plants See cross-referenced techniques in other sections of this document.

Reference literature [179, UBA, 2001], [204, L. Bettens, 2000], [208, ENco, 2001], [11, US EPA, 1995].

4.1.5 Insulation of High Temperature (HT) machines Description Insulation of pipes, valves, tanks and machines is a general principle of good housekeeping practice that should be applied at the general level in all processes.

In this section an example is given of the energy savings achievable by heat insulation of HT dyeing machines.

Main achieved environmental benefits More rational use of energy.

It is reported that insulation can save up to 9 % of the total energy requirement on wet processing machines [146, Energy Efficiency Office UK, 1997]. An integrated approach to energy conservation is, however, preferable to ad hoc measures.

Operational data The nature of the process means that insulation material may be exposed to water, chemicals and physical shock. Any insulation should therefore be covered or coated with a hard-wearing, chemical/water resistant outer layer.

Cross-media effects None believed likely.

Applicability General applicability.

Economics A calculation of the payback for heat-insulation of HT dyeing units is given in the table below [179, UBA, 2001].

–  –  –

Source: [179, UBA, 2001] Table 4.2: Payback periods for heat insulation of dyeing units Driving force for implementation Savings in energy costs.

Reference plants Many plants.

Reference literature [179, UBA, 2001], [146, Energy Efficiency Office UK, 1997]

4.2 Quality management of incoming fibre 4.2.1 Man-made fibre preparation agents with improved environmental performance Description Man-made fibres cannot be produced and processed without auxiliaries. As a consequence of pretreatment operations (e.g. washing and heat-setting) these auxiliaries find their way into the waste water and exhaust air of finishing mills.

Among the auxiliaries used, coning oils and other preparation agents applied to the fibre after it has been manufactured have been identified as the major causes of the pollution in the downstream processes. This is due to the quality of the formulations employed and to the high loads applied (see also Section 2.6.4.2).

Conventional preparation agents are mainly based on mineral oils, with their well known disadvantages of high add-on, low temperature stability (they smoke during high-temperature treatments), poor biodegradability, presence of polyaromatic hydrocarbons and generation of difficult-to-sediment sludge in biological waste water treatment plants (see also Section 8.2).





–  –  –

Alternatives to the mineral oil-containing preparation systems are preparation agents based on [179, UBA, 2001]:

· polyether/polyester or polyether/polycarbonates · special polyolesters · special steric hindered fatty acid esters.

Main achieved environmental benefits Alternative preparation systems are less volatile and have higher thermal stability. Moreover, they can be applied in lower amounts on the fibre. As a result, reduced odour nuisance in the workplace and reduced emission levels of organic volatile compounds in the exhaust air are achieved.

The table below compares the performance of the alternative products with the conventional systems in heat-setting conditions for grey materials.

–  –  –

Table 4.3: Emission factors and corresponding organic-C concentration in the off-gas The optimised products indicated in the table above are easier to wash out (lower consumption of water, energy and chemicals) and are in general characterised by a higher level of biodegradability compared to mineral oil-based preparation agents.

Polyesterpolyetherpolycarbonates compounds, in particular, show extremely good biodegradability in comparison with mineral oils. Sterically hindered fatty acid esters, on the other hand, only represent an improvement with respect to classic fatty acid esters for air emissions from thermal treatment (thermofixation). They are in fact less volatile, but they are more difficult to biodegrade due to the increased branching of the chain.

Operational data

Yarn producer Some machine components have to be made up of high-grade steel due to potential corrosion problems. With polyeter/polyethercarbonate-based products compatibility problems with conventional hydrophobic preparation systems means that thorough equipment cleaning is needed following use.

Fabric producer Because of compatibility problems the equipment has to be cleaned carefully (especially in the case of polyester-/polyethercarbonate-based auxiliaries).

–  –  –

Finishing mill Processes in pretreatment have to be adjusted to the new preparation systems. In some cases (e.g. with polyester-/polyethercarbonate-based auxiliaries) washing steps in pretreatment can be simplified or even omitted.

Cross-media effects Since new products are less volatile, off-gas emissions are reduced, but a higher amount remains on the fabric after heat-setting and eventually ends up in the waste water.

However, because of the lower quantities applied and the better biodegradability of the new products, the replacement will always bring benefits [179, UBA, 2001].

Applicability Low-emission preparation agents are applicable on PES, PA 6.6, PA 6, CV and their blends with PES or CV. However, the applicability depends on the type of fibre and the particular enduse of the final product. As a result, specific trials should be carried out [179, UBA, 2001].

Commission finishers often receive no information from the supplier concerning the quality of preparation agents used. Conventional preparation agents are cheaper and spinning mills look mainly at the economic aspects and at the performance of a given substance in the spinning process. The environmental problems produced in the downstream processes (at the finishing mill) are not seen as a priority by spinning mills.

Economics The following economic aspects affecting all members of the textile processing chain have to be taken into consideration [179, UBA, 2001].

Yarn producer Low-emission auxiliaries are high-price products. This can be compensated by a lower add-on.

Finishing mill Saving of exhaust-air cleaning equipment, simplified waste water treatment and prevention of oil-contaminated wastes will reduce investment, maintenance, and disposal costs.

Additional cost savings can be achieved with those preparation agents that allow total or partial omission of the washing step. Increased operational reliability is also to be expected.

Driving force for implementation Minimising off-gas loads caused by preparation agents (compliance with national regulations) and water saving in washing are the main reasons for the use of low-emission preparation agents.

Reference plants Some fibre/yarn and fabric producers in Europe are using low-emission preparation agents.

Examples of fibre/ yarn producers are listed below [179, UBA, 2001].

Inquitex S. A.

Via Augusta 158, 5a planta E-08006 Barcelona

–  –  –

Nurel S. A.

P. delle Gracia 53 E-08007 Barcelona Nylstar GmbH Postfach 2209 D-24531 Neumünster Nylstar CD Italy Via Friuli 55 I-20031 Cesano Maderno (MI) Textilwerke Deggendorf GmbH Postfach 1909 D-94459 Deggendorf Trevira GmbH & Co KG D-60528 Frankfurt am Main Unifi Textured Yarns Europe LTD.

Co. Donegal Letterkenny, Ireland Reference literature [77, EURATEX, 2000], [179, UBA, 2001].

4.2.2 Mineral oils substitution in wool spinning lubricants Description Spinning lubricants are usually removed during pretreatment to ensure uniform penetration of the dye and finishing agents and to avoid reaction and precipitation with them. Since in the case of wool the processes that take place first in the finishing mill are wet treatments (washing/scouring), the presence of lubricants affects primarily water rather than air emissions.

In carded wool and wool blend yarns, where a higher load of lubricants is applied (compared to worsted wool) spinning oils (together with detergents used in the scouring process) may contribute up to 80 % of the oxygen-demanding load in dyehouse waste water [32, ENco, 2001].

Mineral oil-based lubricants were once used universally in the wool sector. These substances may not be fully degraded in biological sewage treatment works.

Moreover, the formulations of conventional spinning lubricants may contain variable amounts of even more hazardous substances such as polyaromatic hydrocarbons and APEO or other “hard surfactants” as emulsifiers (see also Section 8.2).

Mineral oils have now largely been replaced with formulations based on glycols and this trend continues. Biodegradable substitutes are readily available [32, ENco, 2001]. APEO compounds can now also be substituted by less problematic surfactants.

Main achieved environmental benefits Elimination of mineral oil from scouring and dyeing waste water and the effluents received by sewage treatment works.

–  –  –

Using APEO-free spinning lubricant formulations helps to reduce the amount of potentially toxic endocrine disrupters in the receiving water.

Operational data In the carpet sector, the use of mineral oil-based lubricants is reported to have been in decline for some years, indicating that carpet yarn of commercial quality can be produced without the use of this material [32, ENco, 2001]. It is believed that the same is valid for the textiles sector.

Cross-media effects Compared to mineral oil-based lubricants, increased foaming in the waste water treatment may be observed.

There is some evidence that mineral oil-based lubricants are more amenable to on-site treatment than are the more water-soluble glycol-based products. Where there is on-site pretreatment, the choice of lubricant may be critical and mineral oil-based products may be the more viable option. Further research may be required [32, ENco, 2001].

Applicability

Spinning lubricants are applied during fibre blending. Undertakings which include the manufacturing processes leading up to wet processing, such as sales yarn spinning, and vertically-integrated companies have the means to control the use of these materials “in house”.

Commission dyers receive yarn on which the lubricant is already present. In these cases it would be necessary to work with clients to eliminate these materials from the supply chain [32, ENco, 2001].

Economics The consequences of substituting one spinning lubricant for another are difficult to predict as the yarn yield (the quantity of yarn obtained from a given mass of raw fibre) is notoriously difficult to measure accurately and very small changes in yield markedly affect the economics of yarn production. The lubricant type and level of application can have a significant impact on yield [32, ENco, 2001].

Driving force for implementation Environmental legislation.

Reference plants Many plants in Europe.

Reference literature [32, ENco, 2001] 4.2.3 Mineral oils substitution in knitted fabric manufacturing Description The production of knitted fabric requires an efficient lubrication of the needles and mechanical elements of the knitting machine. The quantity of lubricants used depends on the technology of the machine and its speed.

–  –  –

The yarn driven by the needles during the manufacturing of the fabric carries part of the lubricant. As a result, the final knitted fabric can contain about 4 – 8 % w/w of lubricant oils that then needs to be removed during pretreatment.

Conventional knitting oils (mineral oil-based formulations) can only be removed through emulsification using detergents, emulsifiers and antiredeposition agents. The process is carried out under alkaline conditions and at temperatures between 80 and 100 ºC. Water consumption is approximately 10 l/kg of fabric, and the time required for the process is about 30 - 60 min.

The proposed technique suggests using hydrosoluble oils instead of conventional lubricants.

With knitted fabrics made of cotton or cotton blends with synthetic fibres these hydrosoluble oils can be easily washed out with water at 40 ºC. This makes it possible to scour and bleach the fabric in one single step, thus saving time, water and energy.

Knitted fabrics made of synthetic fibres (e.g. polyester or polyamide) are often thermofixed before being washed. If conventional oils are present on the fabric, an intense emission of fumes is generated and the remaining oil becomes more difficult to remove from the fabric in the subsequent washings.

Also in this case it is often possible to use water-soluble oils instead of conventional lubricants and to carry out the washing step before thermofixation. Washing takes place in a continuous high-efficiency washing unit (e.g. TVE-Escalé type). After this step the fabric is sent to the stenter and then dyed, washed and finished. In this way emissions of fumes from the stenter are minimised.

Main achieved environmental benefits

Unlike conventional mineral oil-based lubricants, hydrosoluble oils can be easily washed out from the fabric. This helps reduce water, energy and chemicals consumption along with processing time. Moreover, these oils are reported to be biodegradable according to OECD test 301C [295, Spain, 2002], which makes the resulting effluent suitable for treatment in a biological waste water treatment plant.



Pages:     | 1 |   ...   | 38 | 39 || 41 | 42 |   ...   | 83 |


Similar works:

«FELLMONGERY In the sheep industry fellmongery is the process of removing wool from the skin after it has been removed from the carcass, and treating the skin for eventual conversion into leather.Fellmongering has four steps: 1. Depilation Separation of the wool from the skin. The flesh side of the pelt is sprayed with a solution containing Na2S, NaHS, Ca(HS)2, Ca(OH)2 and Na(OH), (the paint), and the wool is pulled off mechanically. 2. Liming Removal of remaining wool and the epidermis (top...»

«STOP ACTING RICH STOP ACTING RICH... And Start Living Like a Real Millionaire THOMAS J. STANLEY, PH.D. John Wiley & Sons, Inc. Copyright © 2009 by Thomas J. Stanley. All rights reserved. Published by John Wiley & Sons, Inc., Hoboken, New Jersey. Published simultaneously in Canada. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning, or otherwise, except as permitted...»

«A Region-of-Interest Method for Texturally-Rich Document Image Coding X-W. Yin, A. C. Downton, M. Fleury, and J. He Department of Electronic Systems Engineering, University of Essex, United Kingdom Tel. +44 (0)1206 872817 Fax. +44 (0)1206 872900 fleum@essex.ac.uk Abstract – Region-of-Interest (ROI) techniques are often utilized to improve coding for detailed regions in natural still-image coding standards such as JPEG2000 [1], but no specific method is stated for determining the ROI map. In...»

«The Fiber Optic Association, Inc. 1119 S. Mission Road #355, Fallbrook, California 92028 USA 1-760-451-3655 Fax 1-781-207-2421 Email: info@thefoa.org http://www.TheFOA.org FOA Technical Bulletin Guide To Fiber Optic Network Design Contents Page Part 1 Introduction 1 Part 2 Getting Started 3 Part 3 Copper, Fiber or Wireless? 5 Part 4 Choosing Transmission Equipment 7 Part 5 Planning The Route 9 Part 6 Choosing Components For Outside Plant Installations 11 Part 7 Choosing Components For Premises...»

«Use of Representative Operation Counts in Computational Testings of Algorithms WP #3459 July 1992 Ravindra K. Ahuja* Indian Institute of Technology James B. Orlin* Massachusetts Institute of Technology * see page bottom for complete address Ravindra K. Ahuja Department of Industrial & Management Engineering Indian Institute of Technology Kanpur 208 016, INDIA James B. Orlin Sloan School of Management Massachusetts Institute of Technology Cambridge, MA 01239 USE OF REPRESENTATIVE OPERATION...»

«Reduction-Oxidation (Redox) Control in Ohio’s Ground Water Quality Division of Drinking and Ground Waters Technical Series on Ground Water Quality November 2014 The Technical Series on Ground Water Quality: This series of reports provides information to the professional/technical community about ground water quality in Ohio’s aquifers. These reports use data from:  the ambient ground water quality monitoring program; and  the public water system compliance programs. These data,...»

«Analysis of Milling Stability by the Chebyshev Collocation Method: Algorithm and Optimal Stable Immersion Levels Eric A. Butcher and Oleg A. Bobrenkov Department of Mechanical and Aerospace Engineering New Mexico State University Las Cruces NM 88001 Ed Bueler Department of Mathematics and Statistics University of Alaska Fairbanks Fairbanks AK 99775 Praveen Nindujarla Department of Mechanical Engineering University of Alaska Fairbanks Fairbanks AK 99775 Abstract In this paper the dynamic...»

«TR 101 661 V1.1.1 (1999-04) Technical Report Terrestrial Trunked Radio (TETRA); Technical requirements specification; Managed Direct Mode Operation (DMO) 2 TR 101 661 V1.1.1 (1999-04) Reference DTR/TETRA-01040 (fdo00ics.PDF) Keywords TETRA, DMO ETSI Postal address F-06921 Sophia Antipolis Cedex FRANCE Office address 650 Route des Lucioles Sophia Antipolis Valbonne FRANCE Tel.: +33 4 92 94 42 00 Fax: +33 4 93 65 47 16 Siret N° 348 623 562 00017 NAF 742 C Association à but non lucratif...»

«WWF HQ: 'Stringent is an understatement' | Magazine Features | Building 01/11/2013 17:41 Friday01 November 2013 WWF HQ: 'Stringent is an understatement' 31 October 2013 | By Thomas Lane At the World Wildlife Fund’s new HQ in Surrey, Willmott Dixon has taken sustainable construction to new levels of rigour, forensically tracking the carbon content of every single element, and even building an FSC-certified workshop on site. So has the result been worth it? If you happened to be a leading...»

«University of Delaware Department of Electrical and Computer Engineering Computer Architecture and Parallel Systems Laboratory Concurrency Analysis for Shared Memory Programs with Textually Unaligned Barriers Yuan Zhang Evelyn Duesterwald† Guang R. Gao CAPSL Technical Memo 079 July, 2007 Copyright c 2007 CAPSL at the University of Delaware †IBM T.J.Watson Research Center, Hawthorne, NY 10532. Email: duester@us.ibm.com University of Delaware • 140 Evans Hall • Newark, Delaware 19716 •...»

«© Copyright, Princeton University Press. No part of this book may be distributed, posted, or reproduced in any form by digital or mechanical means without prior written permission of the publisher. Introduction: Approaches, Puzzles, Biases, and Agency “A SURVEY of university professors found that 94% thought they were better at their jobs than their average colleague” (Gilovich 1991, p. 77). Are university professors exceptionally adept at self-deception? Perhaps not. “A survey of one...»

«Durham Research Online Deposited in DRO: 11 March 2015 Version of attached le: Accepted Version Peer-review status of attached le: Peer-reviewed Citation for published item: Baili, I.K. and Gerrard, C.M. and Gutierrez, A. and Snape-Kennedy, L.M. and Wilkinson, K. N. (2015) 'Luminescence dating of irrigation systems : application to a qanat in Aragon, Spain.', Quaternary geochronology., 14 (B). p. 459. Further information on publisher's website: http://dx.doi.org/10.1016/j.quageo.2015.02.016...»





 
<<  HOME   |    CONTACTS
2017 www.sa.i-pdf.info - Abstracts, books, theses

Materials of this site are available for review, all rights belong to their respective owners.
If you do not agree with the fact that your material is placed on this site, please, email us, we will within 1-2 business days delete him.