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DL/T 5142-2012: Technical code for the design of ash handling system of fossil-fired power plant
DL/T 5142-2012
DL
ELECTRICAL POWER INDUSTRY STANDARD
OF THE PEOPLE?€?S REPUBLIC OF CHINA
ICS 27.100
P 60
File No.: J1461-2012
Replacing DL/T 5142-2002
Technical Code for the Design of Ash Handling System of
Fossil-fired Power Plant
ISSUED ON: AUGUST 23, 2012
IMPLEMENTED ON: DECEMBER 1, 2012
Issued by: National Energy Administration
Table of Contents
Foreword ... 4
1 General Provisions ... 9
2 Terms ... 11
3 Pneumatic Ash Handling System ... 12
3.1 Basic Requirement ... 12
3.2 Positive Pressure Pneumatic Conveying ... 12
3.3 Negative Pressure Pneumatic Conveying ... 15
3.4 Pneumatic Ash Conveying Pipeline ... 17
3.5 Air Slide ... 18
3.6 Dry Ash Classifying System ... 19
4 Hydraulic Ash Handling System ... 20
4.1 Basic Requirement ... 20
4.2 Water Supply for Ash Handling System ... 21
4.3 Hydraulic Jet Pump ... 22
4.4 Ash Trench ... 23
4.5 Ash Slurrying Facilities ... 25
4.6 Centrifugal Ash Slurry Pump ... 26
4.7 Plunger Ash Slurry Pump ... 27
4.8 Dewatering Bin and Settling Facilities ... 28
4.9 Slag Settling Pond ... 28
4.10 Hydraulic Ash Conveying Pipeline ... 29
5 Mechanical Ash Handling System ... 32
5.1 Basic Requirement ... 32
5.2 Air-cooled Type Slag Conveyor... 32
5.3 Submerged Scraper Conveyor ... 33
5.4 Buried-plate Conveyor ... 34
5.5 Vertical Bucket Elevator ... 36
5.6 Bucket Conveyor ... 37
6 Mill Reject Conveying System ... 38
6.1 Basic Requirement ... 38
6.2 Simple Mechanical Conveying ... 38
6.3 Hydraulic Jet Pump Conveying ... 38
6.4 Mechanical Conveying ... 39
7 Compressed Air Supply System ... 40
7.1 Basic Requirement ... 40
7.2 Air Compressor and Treatment Facilities of Compressed Air ... 40
7.3 Rotary Blower and Vacuum Pump ... 42
8 Material Storage and Unloading System ... 43
8.1 Basic Requirement ... 43
8.2 Ash Silo and Ash Hopper ... 44
8.3 Slag Bin and Mill Reject Bin ... 45
8.4 Unloading System and Equipment Selection ... 46
9 Off-site Conveying System ... 47
9.1 Basic Requirement ... 47
9.2 Automobile Transportation ... 47
9.3 Belt Conveyor ... 49
9.4 Ship Transportation ... 53
10 Ash Handling System for CFB Boiler ... 57
10.1 Basic Requirement ... 57
10.2 Slag Handling System ... 58
10.3 Limestone Powder Handling System ... 58
11 Ash Handling System for Municipal Solid Waste Incineration Power Plant ... 60
11.1 Basic Requirement ... 60
11.2 Slag Handling System ... 60
11.3 Ash Handling System ... 61
12 Ash Handling System for Straw Power Plant ... 63
12.1 Basic Requirement ... 63
12.2 Mechanical Ash Handling System ... 63
12.3 Pneumatic Ash Handling System ... 63
12.4 Ash Storage ... 64
13 Slime Pipelines Conveying System ... 65
13.1 Basic Requirement ... 65
13.2 Slime Pipelines Conveying ... 65
13.3 Equipment Selection ... 65
13.4 Slime Pump House ... 65
14 Design Requirements for Relevant Specialties ... 67
14.1 Boiler and Auxiliaries ... 67
14.2 I and C and Electrical ... 67
14.3 Civil Engineering and Hydro-structure ... 69
14.4 Hydraulic and Chemical ... 69
14.5 Heating and Ventilating ... 70
14.6 General Plan Transportation ... 70
Appendix A Calculation of Ash Amount ... 71
Appendix B Calculation of Mill Rejects Amount ... 73
2 Terms
2.0.1 Particle density
The ratio of the material mass to its true volume.
2.0.2 Loose-poured bulk density
The mass per unit volume of particle materials under natural stacking state.
2.0.3 Slurry weight density
The percentage of solid weight, flowing in unit time, in the slurry weight.
2.0.4 Material gas ratio
The ratio of the material mass, being conveyed in unit time in the pneumatic conveying
pipeline, to the gas mass
2.0.5 Percentage of mill rejects
The percentage of mill reject amount, being discharged by the medium speed coal mill in
unit time, in the coal amount entering into coal mill.
3 Pneumatic Ash Handling System
3.1 Basic Requirement
3.1.1 The on-site ash conveying system should adopt positive pressure pneumatic
conveying system. Where the material characteristics and conveying conditions are suitable,
positive pressure dense phase pneumatic conveying system should be adopted.
3.1.2 According to different conveying distances, pneumatic ash conveying system may
adopt air slide, negative pressure and other conveying modes and should meet the following
requirements:
1 Where the conveying distance is shorter than 60m, air slide conveying mode may be
adopted.
2 Where the length of conveying pipeline does not exceed 150m, negative pressure
pneumatic conveying system may be adopted.
3 In combination with specific engineering conditions, system combined by various
pneumatic conveying modes may be adopted.
3.1.3 Where the slag warehouse is relatively far and it is difficult to arrange mechanical
conveying equipment, pneumatic slag conveying system may be adopted.
3.1.4 The flow velocity of pneumatic ash handling pipeline shall be determined reasonably
according to such factors as ash particle diameter, density, conveying pipe diameter and ash
handling and conveying system.
3.1.5 The pneumatic conveying system design shall consider the effects from local air
pressure, air temperature, humidity and other natural conditions.
3.1.6 Where the boiler adopts electric precipitator, the ash conveying system output of the
following stage electric fields shall not be less than the ash amount of the earlier stage electric
field under normal working conditions when the preceding stage electric field loses of power.
3.1.7 Where the boiler slag handling adopts the combined system of air-cooled type slag
conveyor and pneumatic slag conveying, high-temperature resistant slag crusher shall be
arranged at the outlet of air-cooled type slag conveyor, and the particle size of slag discharged
by the slag crusher shall meet the conveying requirements. Buffer slag hopper should be
arranged between the slag crusher outlet and the pneumatic conveying equipment.
3.2 Positive Pressure Pneumatic Conveying
3.2.1 The design output of positive pressure pneumatic ash conveying system should not be
less than 150% of the ash discharge amount of boiler when it fires the design coal at the
working condition of maximum continuous evaporation and should not be less than 120% of
the ash discharge amount of boiler when it fires the check coal.
3.2.2 Two sets of positive pressure pneumatic slag conveying systems should be set for each
boiler that one for operation and the other for standby. The design output of each set of system
should not be less than 150% slag discharge amount of design coal and should not be less
than 120% slag discharge amount of check coal.
3.2.3 The bin type pneumatic conveying pump (hereinafter referred to as bin pump) under
the precipitator ash hopper should be arranged in groups. As for the bin pump under the first
electric field of electric precipitator and the ash hopper of baghose precipitator, the quantity of
bin pumps being operated simultaneously in each group should not exceed 6.
3.2.4 The quantity of pneumatic ash conveying pipelines shall be selected reasonably
according to the system output, group number of ash conveying equipment, pipeline
utilization rate and comprehensive utilization. The conveying output of bin pump being
operated simultaneously in each group and the auxiliary ash pipes should not exceed 80t/h.
The conveying frequency should be controlled at 6~10 times/h.
3.2.5 Manual isolating valve shall be installed between the ash hopper and bin pump.
Pneumatic switching valve shall be arranged at the branch pipe close to the main conveying
pipe.
3.2.6 The exhaust produced during the feeding process of bin pump should be discharged to
the nearby precipitator ash hopper and other silos. The exhaust pipe outlet shall be connected
to the upper area of the high level gage of ash hopper and other silos. On the exhaust pipe,
pneumatic exhaust valve shall be arranged and the included angle between the exhaust pipe
and horizontal plane should not be less than 55??.
3.2.7 The pneumatic ash conveying pipeline should be provided with automatic
anti-blocking measure and blockage-eliminating measure. The outlet of blockage-eliminating
pipeline should be arranged at the upper area of the high level gage. The outlet section of
blockage-eliminating pipeline shall be arranged obliquely.
3.2.8 Where the ash from coal economizer and denitration device ash hopper is conveyed to
the slag bin, the slag bin exhaust filter shall be set with exhaust fan and the filter bag shall be
of high-temperature resistant material.
3.2.9 Exhaust filter should adopt pulse-jet baghose precipitator; the dust concentration of
the filter exhaust shall meet the requirements of national and local environmental standards;
the filtering air velocity of exhaust filter should not be greater than 0.8m/min. The blowback
air shall meet the quality requirement of air for instrument and the blowback air pressure and
air consumption shall be selected according to the materials provided by the manufacturer.
3.2.10 The bin pump layout shall meet the following requirements:
1 The included angle between the ash fall pipe and the horizontal plane should not be
less than 60??.
2 The bin pump should be arranged on the ground. The clear distance between the bin
pump bottom and the ground shall meet the overhaul requirements.
3 Overhaul and maintenance platform should be arranged at the feed valve of bin
pump.
3.2.11 The pressure loss of the positive pressure conveying pipeline shall be the total
pressure loss of horizontal, vertical and inclined pipelines as well as various pipeline
accessories. To simplify the calculation, each part may be converted to a horizontal pipeline
with equivalent length. As for suspension flow conveying, the pressure loss may be calculated
according to the following formulae:
(3.2.11-1)
Leg=L??H+???nLr (3.2.11-2)
Where,
Q - the air flow at the initial end of negative pressure equipment, m3/s;
vb - the specific volume of air at initial end, m3/kg;
ve - the specific volume of air at tail end, m3/kg;
Pb - the absolute pressure of air at initial end, Pa;
Pe - the absolute pressure of air at tail end, Pa;
m - the adiabatic coefficient, which may be taken as 1.2;
w - the average flow velocity, m/s;
wb - the flow velocity at initial end, m/s;
we - the flow velocity at tail end, m/s;
g - the gravity acceleration, taking 9.81 m/s2;
L - the geometrical length of conveying pipeline, m;
f - the friction coefficient; where D??? 200mm, f=0.7; where D???200mm, f=1.1-0.002D;
H - the vertical rise, m;
N - the quantity of 90?? elbow, pcs; where the elbow is smaller than 90??, it is converted to
90?? elbow.
3.4 Pneumatic Ash Conveying Pipeline
3.4.1 Carbon steel pipe should be adopted for straight pipe section of pneumatic ash
conveying pipeline and wear-proof material shall be adopted for elbow and other pipeline
accessories. For straight pipe section with higher flow velocity of conveyance medium and
serious wear, wear resistant pipeline may also be adopted through technical and economical
comparison.
3.4.2 The straight pipe section, elbow and pipeline accessories of pneumatic slag conveying
pipeline shall adopt wear resistant material.
3.4.3 The wall thickness of pneumatic ash conveying pipeline should not be less than 7mm.
3.4.4 As for the layout of pneumatic conveying pipeline, the elbow quantity shall be
reduced and the curvature radius of wear resistant elbow should be 3~6 times of the pipe
diameter of the straight pipe section.
3.4.5 In the pneumatic ash handling system with relatively long conveying distance, the
diameter of ash conveying pipeline shall be changed by sections, and the section quantity and
the length of each section shall be determined through calculation.
3.4.6 At the outlet of ash hopper or when the ash pipe needs to change direction, a straight
pipe section not less than 10 times of the pipe diameter should exist before turning.
3.4.7 The distance from the diameter changing point of the ash conveying pipeline to the
elbow should not be less than 6m.
3.4.8 The pneumatic ash conveying pipeline should be elevated. Where it is arranged on the
ground, walkway shall be arranged at the channel; where it is elevated, the distance to railway,
highway, building and high voltage line shall meet the requirements of the current
professional standards "Technical Code of General Plan Transportation Design for Fossil Fuel
Power Plants" (DL/T 5032) and "Operating Code for Overhead Transmission Line" (DL/T
741).
3.4.9 Where the straight pipe section of the pneumatic ash conveying pipeline is too long
and cannot meet the self-compensation requirements of expansion and contraction,
1 The inclination of air slide shall not be less than 6%.
2 Air slide should consider damp proof and insulation measures.
3 Isolating service valve and electric flap valve shall be installed between the ash
hopper and air slide.
4 Flexible connection should be provided between ash fall pipe and air slide and
between blower and tuyere nozzle.
3.5.4 The air consumption per unit or the total air pressure of air slide shall be determined
respectively through test. Where test data is unavailable, the air consumption per unit may be
selected according to 1.5 m3/(min???m2)~2.5m3(min???m2) (at standard condition) (air-permeable
layer); the total air pressure may be selected according to 3kPa~5kPa.
3.5.5 The clean hot air shall be adopted as the conveying air source of the air slide and the
hot air temperature should be selected according to 40???~80???. The air source should be
supplied by the dedicated fan, and spare one is not required on this occasion; where
conditions permit, the air source may be supplied by boiler blower.
3.5.6 One air intake point shall be arranged at the starting point of air slide, one air intake
point and one air chamber baffle plate should be arranged respectively at each turning point
and every other 30m.
3.5.7 The exhaust of ai...