1、PUBLISHED DOCUMENT PD CEN/TR 15473:2007 Characterization of sludges Good practice for sludges drying ICS 13.030.20 PD CEN/TR 15473:2007 This Published Document was published under the authority of the Standards Policy and Strategy Committee on 31 October 2007 BSI 2007 ISBN 978 0 580 58784 9 National
2、 foreword This Published Document is the UK implementation of CEN/TR 15473:2007. The UK participation in its preparation was entrusted to Technical Committee EH/5, Sludge characterization. A list of organizations represented on this committee can be obtained on request to its secretary. This publica
3、tion does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. Amendments issued since publication Amd. No. Date CommentsTECHNICALREPORT RAPPORTTECHNIQUE TECHNISCHERBERICHT CEN/TR15473 March2007 ICS13.030.20 EnglishVersion Characteriza
4、tionofsludgesGoodpracticeforsludgesdrying CaractrisationdesbouesBonnepratiquepourle schagedesboues CharakterisierungvonSchlmmenGutefachlichePraxis zurSchlammtrocknung ThisTechnicalReportwasapprovedbyCENon27August2006.IthasbeendrawnupbytheTechnicalCommitteeCEN/TC308. CENmembersarethenationalstandards
5、bodiesofAustria,Belgium,Bulgaria,Cyprus,CzechRepublic,Denmark,Estonia,Finland, France,Germany,Greece,Hungary,Iceland,Ireland,Italy,Latvia,Lithuania,Luxembourg,Malta,Netherlands,Norway,Poland,P ortugal, Romania,Slovakia,Slovenia,Spain,Sweden,SwitzerlandandUnitedKingdom. EUROPEANCOMMITTEEFORSTANDARDIZ
6、ATION COMITEUROPENDENORMALISATION EUROPISCHESKOMITEEFRNORMUNG ManagementCentre:ruedeStassart,36B1050Brussels 2007CEN Allrightsofexploitationinanyformandbyanymeansreserved worldwideforCENnationalMembers. Ref.No.CEN/TR15473:2007:E2 Contents Page Foreword3 Introduction .4 1 Scope 5 2 Normative referenc
7、es 5 3 Terms , definitions and abbreviated terms .5 4 General7 5 Treatment process description 9 6 Drying plant ancillaries .35 7 Operation 38 8 Safety considerations .42 9 Characteristics of dried sludge products .47 10 Outlets available 51 Bibliography 56 CEN/TR 15473:20073 Foreword This document
8、(CEN/TR 15473:2007) has been prepared by Technical Committee CEN/TC 308 “Characterization of sludges”, the secretariat of which is held by AFNOR. The status of this document as CEN/TR has been chosen because much of its content is not completely in line with practice and regulations in each member s
9、tate. This document gives recommendations for good practice concerning the drying of sludges, but existing national regulations remain in force. CEN/TR 15473:20074 Introduction All the information of this CEN Technical report constitutes a framework for the process of drying sludges. Various Directi
10、ves will apply to thermally dried sludge products depending on the use to which they are to be put. These Directives include Directive 86/278/EEC(see 1) for recycling to land, Directive1999/31/EC (see 2) for disposal to landfill and Directive 2000/76/EC (see 3) for incineration and energy recovery a
11、nd Directive 94/9 for equipment intended for use in potentially explosive atmospheres (see 4). This document should be read in the context of the requirements of these Directives and any other relevant regulations, standards and codes of practice, which may prevail locally within Member States. CEN/
12、TR 15473:20075 1 Scope This CEN Technical report describes good practices for sludge drying and it is one of a series on sludge management options. It gives guidance on - drying processes; - characteristics of dried sludge products; - recycling or disposal of dried sludge products. from urban wastew
13、ater treatment plants. Sludges of other origin, like sludge from water supply or industrial treatment plants are not in the exact scope of this CEN Technical Report, however the handling of most of these sludges will comply to a large extent with the leads given in this CEN Technical Report. 2 Norma
14、tive references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. EN 1085, Wastewater treatment Voc
15、abulary EN 12832, Characterisation of sludges Utilisation and disposal of sludges Vocabulary CR 13714, Characterisation of sludges Sludge management in relation to use or disposal CEN/TR 13767, Characterisation of sludges Good practice for sludges incineration with and without grease and screenings
16、CEN/TR 13768, Characterisation of sludges Good practice for combined incineration of sludges and household wastes CEN/TR 15126, Characterisation of sludges Good practice for landfilling of sludges and sludge treatment residues 3 Terms , definitions and abbreviated terms 3.1 Terms and definitions For
17、 the purposes of this document the terms and definitions given in EN 1085, EN 12832 and CR 13714 apply and also those given in: Directive 91/271/EC (see 5) concerning urban wastewater treatment; Directive 75/442/EC (see 6) the waste framework directive as amended by Directive 91/156/EC (see 7); Dire
18、ctive 99/31/EC (see 2) on the landfill of waste; Directive 86/278/EEC (see 1) on the protection of the environment, and in particular the soil, when sewage sludge is used in agriculture; Directive 2000/76/EC (see 3) on incineration; Directive 94/9 (see 4) for equipment intended for use in potentiall
19、y explosive atmospheres; CEN/TR 15473:20076 Directive 99/92/EC (see 8) on minimum requirements for improving the safety and health protection of workers potentially at risk from explosive atmospheres; and the following terms and definitions apply: 3.1.1 adhesion or shearing phase phase, which exists
20、 in a range of some 40 % to 60% dry residue content, where the sewage sludge changes its rheological behaviour. Within this phase there is a “sticky mass“ whose treatment and transportation is to be given special attention. Above the adhesion phase the sewage sludge has, in many cases, depending on
21、the drying equipment, a more crumbly/lumpy structure that makes it easier to handle 3.1.2 fully dried / partly dried sludge sludge dried above 85% dry residue content is defined as “fully dried” and sludge of dry residue content below 85% as “partly dried” 3.1.3 convection dryer drying system where
22、the heat is transferred to the product by a gaseous medium which is in intimate and direct contact with the product NOTE The evaporated water is thus mixed with the drying medium and the exhaust gases from the dryer consist of the drying gas including leakage air plus the evaporated water. Convectio
23、n dryer can operate with direct or indirect heating. 3.1.4 conduction dryer drying system where the heat is transferred through an intermediate heat transfer surface to the product NOTE The medium, which supplies the heat to the product, is never in direct contact with it. The total exhaust gas amou
24、nt leaving the dryer is the evaporated water plus some leakage air. Therefore a conduction dryer is always operated with indirect heating. 3.1.5 solar dryer drying system where the heat is transferred to the product by solar radiation 3.1.6 combined drying system system, which uses both principles,
25、convection and conduction in the same dryer 3.1.7 hybrid drying system system that consists of a combination of a conduction dryer and a convection dryer 3.1.8 direct heating off gas from the burner is in contact with the drying product 3.1.9 indirect heating heating loop is crossing a heat exchange
26、r 3.2 Abbreviated terms BOD Biological Oxygen Demand COD Chemical Oxygen Demand CEN/TR 15473:20077 HAZOP Hazard and Operability Studies LCV Lower Calorific Value LIT Layer Ignition Temperature LOC Limiting Oxygen Concentration MEC Minimum Explosion Concentration MIE Minimum Ignition Energy MIT Minim
27、um Ignition Temperature MPOC Maximum Permissible Oxygen Concentration PLC Programmable Logic Controller RTO Regenerative Thermal Oxydizer SCADA System Control, Alarm and Data Acquisition VOC Volatile Organic Carbon WWTP Waste Water Treatment Plant 4 General The drying of sewage sludge is a complex p
28、rocess but it can contribute to the need for increased disposal security for sewage sludge. With dried sewage sludge, a wider potential customer market can be approached than for liquid or dewatered products. It can be recorded that the range of those willing to accept sewage sludge can be expanded
29、if one offers dried sewage sludge. In any case, the opportunity for marketing sewage sludge can be extended considerably which, in turn, represents an additional security for disposal and/or utilisation. The overview of thermal dryer types is given in Figure 1. CEN/TR 15473:20078 with direct heating
30、 Convection dryers Conduction dryers with indirect heating Dryers with indirect heating Combined drying systems: Hybrid drying systems + Convection dryer Conduction dryer The principles of convection and conduction are applied in one dryer Solar dryers Figure 1: Overview on thermal dryer types Therm
31、al drying of sludge can result in the following advantages for almost all outlet routes: Substantial minimisation of the bulk of sludge for disposal. Thus 1 t dry residue of sludge at 90% represents 1,1 t actual or wet mass of sludge for disposal, but 1 t dry residue of sludge at 5% represents 20 t
32、wet mass of sludge for disposal. Minimisation of sludge mass and volume by thermal drying results in savings in transport costs, which can be a major component of disposal costs. The removal of water leaves a thermally dried sludge product with a lower calorific value (LCV) (about 10 MJ/kg to 15 MJ/
33、kg, depending e.g. upon the extent of pre-treatment), which can be used for thermal recycling. The thermally dried sludge product has favourable properties, as it is usually handable and storable, which lends flexibility to operations. For recycling to agriculture, in particular, there is the advant
34、age that thermal drying is an advanced treatment process whereby the dried sludge product gets sanitised and effectively free of pathogens at the end of the process. Whilst the thermally dried product has definite advantages over other types of sewage sludge, there are some reservations (Brown and J
35、acobs, 2001 (see 9) about the thermal drying process as follows: High capital cost (see 7.2.1); High operating cost, mainly energy consumption (see 7.2.1); Safety issues, particularly risk of fire and explosion (see clause 8); Technology can be complex and needs some well trained operators (see 7.3)
36、; The thermally dried product can be re-infected by micro-organisms and as a result of rewetting odour can be released after storage dependent upon the conditions of storage. CEN/TR 15473:20079 The thermally dried sludge product can reach a dry residue content up to about 95% mass fraction. In most
37、instances thermal drying of sludge will aim to achieve a dry residue content of more than 50% in order to avoid the adhesion or shearing phase. 5 Treatment process description 5.1 General There are numerous designs of thermal drying equipment available on the market and many of these have been adapt
38、ed from other industries and used for sewage sludge drying. Few have been designed specifically for sewage sludge. The equipment can be classified into four main groups defined by the drying process: Conduction dryers; Convection dryers; Combined or hybrid drying system; Solar dryers (radiation drye
39、rs). 5.2 Conduction dryers 5.2.1 General A conduction dryer is a drying system where the heat is transferred through an intermediate heat transfer surface to the product. The medium, which supplies the heat to the product, is never in direct contact with it. The total exhaust gas volume leaving the
40、dryer is the evaporated water plus some leakage air. Therefore conduction dryers are always operated with indirect heating. 5.2.2 Disc dryers Disc drying plants are - dependent on their shape - in a position to dry sewage sludge, both partially and completely. With this, complete drying is made poss
41、ible using a mixing machine placed before the dryer. Here, a part of the already dried product is mixed with the dewatered sludge and thus overcoming of the adhesion phase is achieved outside the dryer. Plants for full drying, as special structures, are also used by which the return admixture takes
42、place in the input area of the dryer. Wear problems and dried sludge behaviour (fines and dust) have contributed to the decline in use of disc dryers for full drying. In the majority of cases, disc dryers are used to dry sludge up to a dry residue content below the shearing phase (for an auto therma
43、l incineration). CEN/TR 15473:200710 Figure 2: Disc dryer 1)The disc dryers (see Figures 2 and 3) are constituted of: A stator or body A rotor composed of a hollow shaft with hollow discs shaped as plates and welded on it. A heating fluid crosses the rotor, either saturated steam up to approximately
44、 1 MPa (10 bar) or thermal oil, which transfer thermal energy to the dewatered sludge, through the discs surface. A process variant can additionally have the stator heated. The thermal oil (or steam) is heated in a boiler, usually fired with fossil fuel or biogas. Vapours exhaust from the superior d
45、ome of the dryer, which should be correctly designed for effective transfer to a cyclone or a scrubber (partial drying at 45 %). As the residence time of the sludge in this type of dryer is rather large (around 1h), the vapours are usually highly polluted. However, one advantage of an indirect condu
46、ction dryer is that the volume of polluted vapours is small and kept separated from the flue gases of the energy source. Due to the slow rotation of the rotor (circumferential velocity approximately 1 m/s) the sewage sludge is well mixed and a new interface for drying is continuously created. The re
47、quirements of the start-up condition are, met with the design of the drive. Transport paddles, by which the sewage sludge is transported axially in the dryer, are additionally mounted on the rotor discs. However, in order to dry past the sticky phase, it is necessary to recycle some dry product upst
48、ream. 1) This dryer is an example of a suitable design of thermal drying equipment available commercially. This information is given for the convenience of users of this CEN Technical Report and does not constitute an endorsement by CEN of this equipment. The manufacturer has given the authorisation to reproduce the scheme included in SIL documentation. CEN/TR 15473:200711 The dryer discs are subjected to high wear and corrosion loads, which should be taken into account through the selection of suitable materials or appropriate wear reserves, and in terms of maintenance and life time
