FprEN 12952-16

Water-tube boilers and auxiliary installations - Part 16: Requirements for grate and fluidized-bed firing systems for solid fuels for the boiler

This Part of this European Standard applies to atmospheric fluidized-bed and grate firing systems of steam boilers and hot water generators. These systems commence at the fuel bunkers and end at the ash extraction plant. For combination of various firing systems, the individual requirements of each system apply, especially those included in EN 12952-8 and EN 12952-9.
If several fuels are burnt simultaneously or if a fuel quality varies considerably (e.g. moisture content), additional safety measures may be necessary, especially with respect to limitation of the fuel flow into the firing system and ensuring proper air supply to the individual fuels.
Pressurized firing systems may require enhanced safety measures, which are not given in this European Standard.

Wasserrohrkessel und Anlagenkomponenten - Teil 16: Anforderungen an Rost- und Wirbelschichtfeuerungsanlagen für feste Brennstoffe für den Kessel

Chaudières à tubes d’eau et installations auxiliaires - Partie 16: Exigences pour les équipements de chauffe à lit fluidisé pour combustibles solides

Vodocevni kotli in pomožne napeljave - 16. del: Zahteve za kurilne sisteme na trdna goriva z zgorevalno rešetko ali z lebdečo plastjo

General Information

• Status: Not Published
• ICS: 27.040 - Gas and steam turbines. Steam engines
• Technical Committee: CEN/TC 269 - Shell and water tube boilers
• Drafting Committee: CEN/TC 269/WG 1 - Water-tube boilers
• Current Stage: 5060 - Closure of Vote - Formal Approval
• Directive: 2014/68/EU - Directive 2014/68/EU of the European Parliament and of the Council of 15 May 2014 on the harmonisation of the laws of the Member States relating to the making available on the market of pressure equipment
• Directive: 97/23/EC - Directive 97/23/EC of the European Parliament and of the Council of 29 May 1997 on the approximation of the laws of the Member States concerning pressure equipment
• Mandate: M/071 - Mandate to CEN for standardization in the field of Pressure equipment
• Ref Project: kSIST FprEN 12952-16:2022 - Water-tube boilers and auxiliary installations - Part 16: Requirements for grate and fluidized-bed firing systems for solid fuels for the boiler

RELATIONS

• Revised: EN 12952-16:2002 - Water-tube boilers and auxiliary installations - Part 16: Requirements for grate and fluidized-bed firing systems for solid fuels for the boiler
• Effective Date: 13-Mar-2010

Standards Content (sample)

SLOVENSKI STANDARD
oSIST prEN 12952-16:2020
01-marec-2020
Vodocevni kotli in pomožne napeljave - 16. del: Zahteve za kurilne sisteme na
trdna goriva z zgorevalno rešetko ali z lebdečo plastjo

Water-tube boilers and auxiliary installations - Part 16: Requirements for grate and

fluidized-bed firing systems for solid fuels for the boiler
Wasserrohrkessel und Anlagenkomponenten - Teil 16: Anforderungen an Rost- und
Wirbelschichtfeuerungsanlagen für feste Brennstoffe für den Kessel

Chaudières à tubes d’eau et installations auxiliaires - Partie 16: Exigences pour les

équipements de chauffe à lit fluidisé pour combustibles solides
Ta slovenski standard je istoveten z: prEN 12952-16
ICS:
27.060.30 Grelniki vode in prenosniki Boilers and heat exchangers
toplote
oSIST prEN 12952-16:2020 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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oSIST prEN 12952-16:2020
DRAFT
EUROPEAN STANDARD
prEN 12952-16
NORME EUROPÉENNE
EUROPÄISCHE NORM
February 2020
ICS 27.040 Will supersede EN 12952-16:2002
English Version
Water-tube boilers and auxiliary installations - Part 16:
Requirements for grate and fluidized-bed firing systems
for solid fuels for the boiler

Chaudières à tubes d'eau et installations auxiliaires - Wasserrohrkessel und Anlagenkomponenten - Teil 16:

Partie 16: Exigences pour les équipements de chauffe à Anforderungen an Rost- und

lit fluidisé pour combustibles solides Wirbelschichtfeuerungsanlagen für feste Brennstoffe

für den Kessel

This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee

CEN/TC 269.

If this draft becomes a European Standard, CEN members are bound to comply with the CEN/CENELEC Internal Regulations

which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.

This draft European Standard was established by CEN in three official versions (English, French, German). A version in any other

language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC

Management Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,

Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,

Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and

United Kingdom.

Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are

aware and to provide supporting documentation.

Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without

notice and shall not be referred to as a European Standard.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels

© 2020 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 12952-16:2020 E

worldwide for CEN national Members.
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Contents Page

European foreword ...................................................................................................................................................... 4

1 Scope .................................................................................................................................................................... 6

1.1 Firing systems .................................................................................................................................................. 6

1.2 Fuels ..................................................................................................................................................................... 6

1.3 Operation ........................................................................................................................................................... 6

2 Normative references .................................................................................................................................... 7

3 Terms and definitions ................................................................................................................................... 7

4 Fuel storage facilities with conveying plant .......................................................................................... 9

4.1 General................................................................................................................................................................ 9

4.2 Conveying plant ............................................................................................................................................. 10

4.3 Fuel bunkers ................................................................................................................................................... 10

4.4 Fuel bins ........................................................................................................................................................... 11

5 Fuel treatment ............................................................................................................................................... 11

5.1 General.............................................................................................................................................................. 11

5.2 Size reduction of the fuel ............................................................................................................................ 11

5.3 Drying of the fuel ........................................................................................................................................... 12

6 Fuel feeding ..................................................................................................................................................... 12

7 Explosion prevention measures .............................................................................................................. 13

8 Equipment for combustion air supply and flue gas discharge ..................................................... 13

8.1 Air supply ......................................................................................................................................................... 13

8.2 Combustion air/fuel ratio .......................................................................................................................... 14

8.3 Flue gas discharge ......................................................................................................................................... 14

9 Firing system .................................................................................................................................................. 15

9.1 General.............................................................................................................................................................. 15

9.2 Monitoring and control ............................................................................................................................... 15

9.3 Electrical equipment.................................................................................................................................... 15

9.4 Safety precautions ........................................................................................................................................ 16

9.4.1 General.............................................................................................................................................................. 16

9.4.2 Purging ............................................................................................................................................................. 16

9.4.3 Lighting-up ...................................................................................................................................................... 16

9.4.4 Start-up ............................................................................................................................................................. 17

9.4.5 Shutting down ................................................................................................................................................ 17

9.5 Common stack for several firing systems ............................................................................................ 18

10 Ash handling and extraction ..................................................................................................................... 18

11 Operating manual ......................................................................................................................................... 18

Annex A (informative) Operational requirements for permanently supervised firing

systems for solid fuels for fluidized-bed and grate firing systems ............................................. 20

A.1 General.............................................................................................................................................................. 20

A.2 Operation ......................................................................................................................................................... 20

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A.3 Operation and maintenance ..................................................................................................................... 20

A.3.1 General ............................................................................................................................................................. 20

A.3.2 Operating instructions ................................................................................................................................ 20

Annex B (informative) Significant technical changes between this European Standard and

the previous edition ..................................................................................................................................... 21

Annex ZA (informative) Relationship between this European Standard and the essential

requirements of EU Directive 2014/68/EU aimed to be covered ............................................... 22

Bibliography ................................................................................................................................................................. 23

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European foreword

This document (prEN 12952-16:2020) has been prepared by Technical Committee CEN/TC 269 “Shell

and water-tube boilers”, the secretariat of which is held by DIN.
This document will supersede EN 12952-16:2002.
This document is currently submitted to the CEN Enquiry.

EN 12952 series concerning water-tube boilers and auxiliary installations consists of the following

parts:
• Part 1: General;
• Part 2: Materials for pressure parts of boilers and accessories;
• Part 3: Design and calculation for pressure parts;
• Part 4: In service boiler life expectancy calculations;
• Part 5: Workmanship and construction of pressure parts of the boiler;

• Part 6: Inspection during construction, documentation and marking of pressure parts of the boiler;

• Part 7: Requirements for equipment for the boiler;

• Part 8: Requirements for firing systems for liquid and gaseous fuels for the boiler;

• Part 9: Requirements for firing systems for pulverized solid fuels for the boiler;

• Part 10: Requirements for safeguards against excessive pressure;
• Part 11: Requirements for limiting devices of the boiler and accessories;
• Part 12: Requirements for boiler feedwater and boiler water quality;
• Part 13: Requirements for flue gas cleaning systems;

• Part 14: Requirements for flue gas DENOX systems using liquefied pressurized ammonia and ammonia

water solution;
• Part 15: Acceptance tests;

• Part 16: Requirements for grate and fluidized-bed firing systems for solid fuels for the boiler;

• CR 12952 Part 17: Guideline for the involvement of an inspection body independent of the

manufacturer.

Although these parts may be obtained separately, it should be recognized that the parts are inter-

dependent. As such, the design and manufacture of water-tube boilers requires the application of more

than one part in order for the requirements of the document to be satisfactorily fulfilled.

NOTE Part 4 and Part 15 are not applicable during the design, construction and installation stages.

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This European Standard has been prepared under a mandate given to CEN by the European

Commission and the European Free Trade Association, and supports essential requirements

EU Directive 2014/68/EU [1].

For relationship with EU Directive 2014/68/EU, see informative Annex ZA, which is an integral part of

this document.
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1 Scope
1.1 Firing systems

This document applies to atmospheric fluidized-bed and grate firing systems of steam boilers and hot

water generators. These systems commence at the fuel bunkers and end at the ash extraction plant. For

combination of various firing systems, the individual requirements of each system apply, especially

those included in prEN 12952-8:2020 and prEN 12952-9:2020.

If several fuels are burnt simultaneously or if a fuel quality varies considerably (e.g. moisture content),

additional safety measures may be necessary, especially with respect to limitation of the fuel flow into

the firing system and ensuring proper air supply to the individual fuels.

Pressurized firing systems may require enhanced safety measures, which are not given in this European

Standard.
1.2 Fuels

This document covers the use of solid fuels. Pulverized fuel fired in an entrained air flow (burner)

system is covered by prEN 12952-9:2020.
Solid fuels covered are:

• all coal qualities, e.g. lignite or brown coal, sub-bituminous or hard brown coal, bituminous coal or

hard coal, pitch coal, anthracite, coke, coal culm, coal sludge;
• other fossil solid fuels (e.g. peat, oil shale);

• biomass solid fuels (e.g. wood, wood wastes [bark], pellets, energy plants [miscanthus], harvest

wastes [straw] and briquettes);

• municipal waste solid fuels (e.g. garbage, sewage sludge, refuse derived fuels [RDF]);

• industrial waste solid fuels (e.g. petrol coke, soot, tyres, paper wastes, coated wood chips, spent

wood, animal product wastes).

Fuel blends from two or more groups, or fuels of unconventional or unknown quality may require

special safety measures which can be proved either by practical experience gained from comparable

fuels, or by suitable tests, e.g. in accordance with EN 14034-2:2006+A1:2011. Such measures specified

and documented by the manufacturer.

Fuels on which the design is documented in the operating instructions (see 11.2). This includes the fuel

data for 100 % input of the basic fuel and the data for any supplementary fuels together with their

maximum thermal input percentage.
1.3 Operation

The requirements for operational equipment in Clause 4, Clause 5, Clause 6, Clause 7, Clause 8, Clause 9,

Clause 10 and Clause 11 apply to steam boilers and hot water generators with permanent supervision

by properly trained personnel familiar with the special conditions of the firing systems and the type of

fuel.
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2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements 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.

prEN 12952-8:2020, Water-tube boilers and auxiliary installations — Part 8: Requirements for firing

systems for liquid and gaseous fuels for the boiler

prEN 12952-9:2020, Water-tube boilers and auxiliary installations — Part 9: Requirements for firing

systems for pulverized solid fuel for the boiler

EN 50156-1:2015, Electrical equipment for furnaces and ancillary equipment - Part 1: Requirements for

application design and installation
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
annunciator

device to sense a non-standard or abnormal condition and initiate a visual and/or audible signal

3.2
back-up firing system
separate firing system to maintain safe ignition and stable combustion
3.3
basic fire

in the case of grate firing systems the layer of glowing fuel, fire bed, or flame of the fed fuel

Note 1 to entry: The basic fire ensures safe ignition.
3.4
carrier gas
transport medium for pneumatic conveying
3.5
combustion air
total air supplied to the firing system for combustion
3.6
combustion process monitoring device

device which detects the presence of the fire, or the conditions required for a stable combustion process

Under preparation
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3.7
firing system heat input
heat input into the combustion chamber

Note 1 to entry: This normally is calculated as the mass flow of the fuel multiplied by its net calorific value.

3.8
firing systems

the total equipment required for the combustion of fuels, including the installations for the storage in

the boiler house, preparation and supply of fuels, the combustion air supply, the grate or fluidized bed,

the flue gas discharge, and all related control and monitoring devices
3.9
fluidized-bed combustion firing systems (FBC)
fuel is burnt in its fluidized state together with an inert component
3.10
fuel bin
silo
dust-tight and air-tight container for storage of fuels
3.11
fuel bunker
container for the storage of solid fuel
3.12
fuel feeding system
device to transport fuel into the combustion chamber

Note 1 to entry: This can be effected e.g. by feeders through ports in the furnace walls, by means of chutes or

lances, through the bottom grate or fluidizing gas distributor, or indirectly into the ash recirculation or

combustion air supply.
3.13
fuel handling plant

installation for conveying, mixing and distributing solid fuels to the individual fuel bunkers or fuel bins

3.14
grate firing system

fuel is burnt in a layer supported by a system e.g. firebars, which can have a cooling system

3.15
indicator

measuring instrument which indicates a variable value (e.g. pressure, temperature, flow, level)

Note 1 to entry: It can be equipped with an annunciator.
3.16
lighting-up equipment
facility to achieve safe ignition of the feed fuel
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3.17
limiter

transducer, which, on reaching a fixed limit value (e.g. pressure, temperature, flow, level) is used to

interrupt and lock-out the energy supply. It requires manual unlocking before restart

3.18
lockout
interruption of the energy supply
Note 1 to entry: Manual unlocking is required before restart.
3.19
minimum fluidized-bed temperature
lowest temperature of the fluidized material at which it can be safely burnt
3.20
minimum heat input of the firing system
minimum heat input at which the firing system can be safely operated
3.21
monitor

transducer which on reaching of a fixed limit value and initiates an alarm and/or a cut-out. The output

signal only reverses if the causing value has changed at a defined range
3.22
purging of the flue gas passes

flow including air through the combustion chamber, flue gas passes, treatment systems and associated

ducts which effectively removes any gaseous combustibles
3.23
cold start-up condition

plant started when the temperature of ceramic lining and bed material is at ambient value

4 Fuel storage facilities with conveying plant
4.1 General

4.1.1 All facilities shall be designed so as to withstand mechanical and thermal stresses. Fuel shall not

be heated to an unacceptable level. Sites where fuel may accumulate shall be avoided.

4.1.2 Conveyance, temporary storage, and extraction of fuel shall be arranged such that blockage is

avoided.

4.1.3 Fuels liable to volatise or pyrolysis in the absence of external heating require measures to

prevent fire, explosion and injuries to personnel.

NOTE Wet sludges can have an inherent explosion risk due to the release of volatiles (e.g. methane) when

stored. Dried sludges have a fire and dust explosion risk comparable to that of pulverized fuels. Sludge storage in

bins is preferable to bunker storage (see 4.4.1).

4.1.4 The storage of fuels supplied in small grain sized particles or fibres which can be stirred up and

become airborne shall only be permitted in bins (silos).
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4.1.5 If different types of fuels are used, dangerous operating conditions due to blending shall be

excluded, e.g. by the use of separate bunkers or bins and separate feeding systems.

4.1.6 If there is a risk of blockage of conveying systems or firing systems by coarse fuel lumps, foreign

matter, and tramp metal, it shall be removed, preferably before entering the bunker.

4.2 Conveying plant

4.2.1 Several continuous conveyors arranged in series to form one conveying line shall be interlocked

such that the normal operation of any conveyor is possible only if the downstream conveyors are in

operation and the storage facility is ready to accept the fuel.

4.2.2 Automatic facilities for open mechanical conveyance and distribution of fuel shall only start

after visual and/or audible warning signals have been given.

Precautions shall be taken for the protection of personnel against injury from moving components.

Sufficient time shall be provided between a warning signal and starting of the plant.

4.2.3 If the type and format of the fuel requires bins (silos) for temporary storage in accordance with

4.1.3 or 4.1.4, subsequent conveyance shall be performed in a closed system, which shall be air-tight if

operated under internal pressure.

4.2.4 For pneumatic conveyance of fuel in closed pipes, deposition shall be prevented by sufficient

velocity of the carrier gas depending on the type and format of the fuel.

4.2.5 All piping system components of a pneumatic conveying system shall be capable of being

purged of fuel.

4.2.6 Feeding of fuel into the pneumatic conveying line shall be interlocked in such a way that feeding

is possible only if sufficient carrier gas is supplied. Suitable monitoring devices, e.g. monitors for flow or

pressure of the carrier gas shall be provided.

4.2.7 If the carrier gas is exhausted to the atmosphere via a dust separator, the outlet shall be

protected against contact with ignition sources, or sparks.

4.2.8 If multiple lines are installed, devices shall be provided to isolate idle conveying lines from the

downstream storage facility or the furnace.
4.2.9 If fuels are conveyed hydraulically by pumps, 4.2.3 to 4.2.5 shall apply.
4.3 Fuel bunkers

4.3.1 With exception of bunkers emptied by cranes, fuel bunkers shall be built to achieve uniform

discharge by the selection of proper shape and design, in order to ensure a continuous uniform fuel flow

and to avoid segregation.

4.3.2 To avoid ingress of hot air/gas into the bunker, a minimum fuel level shall be maintained and

monitored in the bunker, or other suitable measures shall be taken.

4.3.3 The inner surface of the fuel bunker roof shall be designed to prevent the accumulation of dust

and gas in dead pockets.

4.3.4 Bunker charging openings shall be guarded to prevent personnel from falling in.

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4.3.5 Fuel bunkers shall be equipped with fire fighting or fire prevention equipment. Coal bunkers

may be emptied by use of emergency chutes.
4.4 Fuel bins

4.4.1 Some fuels according to their type and format shall be stored in dust-tight bins (silos). The

requirements for pulverized fuel bins defined in prEN 12952-9:2020, 5.4 and 6.2.2 shall apply.

4.4.2 The permissible maximum storage temperature shall be specified for each single fuel and fuel

blends and shall be monitored during the storage, if there is a risk of self ignition.

4.4.3 If emanation of combustible gas from the fuel cannot be prevented, bins shall be equipped with

suitable gas monitoring and safe venting devices, or an explosion-proof bin or inert gas protection shall

be provided.

4.4.4 Fuels described in 4.1.4 shall be stored in bins equipped with a stationary non-freezing fire

extinguishing system to enable fire to be fought without opening access doors. The extinguishing

compound shall be evenly sprayed across the entire cross sectional area of the bin. Spray nozzles shall

be protected against blockage by the ingress of dust. Where stationary spray-type extinguishing

systems are operated automatically, manual initiation shall be possible.

4.4.5 Outdoor bins and fuel bearing components as well as buildings for indoor installation shall be

equipped with a lightning protective system (according to relevant standards e.g. EN 62305-1:2011).

5 Fuel treatment
5.1 General

5.1.1 The equipment shall be designed to withstand mechanical and thermal stresses. It shall be so

arranged as to be readily accessible to enable cleaning operations to be carried out. The total system

shall be gas tight if operated under internal pressure.

5.1.2 Practicable steps shall be taken to avoid sites in the plant where combustible dust or fuel may

become lodged.

5.1.3 If there is a possibility of settlement of combustible dust on components that have become hot

during operation, facilities shall be provided for purging and cleaning after shut-down.

5.1.4 Mechanical equipment for fuel treatment shall be designed and operated such that no

unacceptable heating of the fuel occurs.

5.1.5 The system shall include indicators and annunciators which will provide the operator with

adequate information about significant operating conditions, both normal and abnormal.

5.1.6 To avoid the build up of electrostatic charges, all components shall be earthed unless forced and

faultless earthing is inherent in the design.
5.2 Size reduction of the fuel

If size reduction of the fuel is performed by mills or crushers in the boiler house with the application of

hot gas as the carrier gas for combined grinding and drying process, the requirements for mills and the

necessary explosion prevention measures given in prEN 12952-9:2020, 5.3, Clause 6, and 8.7.4 shall

apply.
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5.3 Drying of the fuel

When drying fuel prior to combustion, the permissible maximum temperature shall be monitored. The

vapours shall be discharged in order to prevent the risk of explosion. For combined grinding and drying

process see 5.2.
6 Fuel feeding

6.1 Fuel feeding systems shall be designed to withstand mechanical and thermal stresses.

6.2 Fuel feeders shall be designed to provide a continuous fuel flow.

6.3 A shut-off device shall be installed within the fuel feeding system. This shut-off device shall be

closed automatically:
• if the minimum fuel level is lost when mechanical feeding;
• if the minimum supply pressure is lost when pneumatic or hydraulic feeding.

Shut-off devices need not to be installed if a rotary vane feeder is installed or if it can be ensured that

negative pressure is maintained in the fuel feeding system or a minimum fuel level (see 4.3.2) is

maintained in the fuel bunker.

6.4 It shall be ensured that after shut-off of the firing system and during outage, no fuel can enter the

furnace.

6.5 The feeding of fuel shall be cut off in the event of control power loss (see 9.2.4), under the start-up

conditions in accordance with 9.4.4.1 a), or under shutting-down conditions in accordance with

9.4.5.1 a).

6.6 Fuel feeding systems shall be made such that flash-back by flame, or flying sparks and backfire, or

egress of hot gases is prevented.

6.7 Depending on the type of fuel, fire fighting equipment shall be installed. An alarm shall be

activated, when a set value has been exceeded in the fuel supply equipment. Equipment for monitoring

and fire fighting shall be placed in such a way that a fire can be extinguished quickly. The equipment

shall be easy to test.

6.8 Pneumatic fuel feeding shall be performed either indirectly by carrier gas separation (see 4.2.8)

...