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2017.06.21
Haijuan Wang
University of Science and Technology Beijing, China
A novel method for innocent treatment of reducing dephosphorization slags
5th International Conference on Sustainable Solid Waste Management
CONTENTS
CHAPTER 01
CHAPTER 02
CHAPTER 03
CHAPTER 04
CHAPTER 05
INTRODUCTION
THEORETICAL ANALYSIS
EXPERIMENTS
RESULTS AND DISCUSSIONS
CONCLUSIONS
1
5th International Conference on Sustainable Solid Waste Management
FeNi production
2
OresCompositions（wt%）
Ni/FeNi Co Fe MgO SiO2 CaO Al2O3 P S H2O
Indonesiafines
1.81 0.03 18.1 15.28 32.91 — 2.04 0.007 0.019 31.0 0.10
Indonesia lumpy ore
1.46 0.08 8.8 21.91 43.31 — 0.66 0.006 0.008 23.3 0.17
Philippinesfines
1.38 — 14.1 22.13 27.92 2.52 — 0.008 0.011 30.2 0.10
Philippineslumpy ore
1.82 — 5.68 28.83 32.73 2.80 — 0.007 0.008 25.2 0.32
INTRODUCTION
Main compositions of laterite ores
It is cost effective to make high‐Si FeNi and use its characteristics for Stainless Steel making.
5th International Conference on Sustainable Solid Waste Management
INTRODUCTION New process for 300 series SS production
3
P content in FeNi alloy is strictly limited
5th International Conference on Sustainable Solid Waste Management
INTRODUCTION De-P of current high-Si FeNi alloy
4
Reducing dephosphorization(RDP) process
Ca3P2(s)+6H2O(g)=3Ca(OH)2(s)+2PH3(g)
[Ca] + 2/3[P] = 1/3(Ca3P2)
Ca3P2 generates PH3 when it is exposed in the moist atmosphere at room temperature
Reducing dephosphorization (RDP) process is in preference to oxidizing method because of its protection of silicon and valuable metals as well as its excellent dephosphorization effect.
Manage RDP slags innocuously not only relates to the success of the electric‐silicothermicmethod for 300 series stainless steel production, but also provides good solutions for processes which generate RDP slags.
5th International Conference on Sustainable Solid Waste Management
Studies reported for RDP slag treatment
5
INTRODUCTION
Nippon Steel Corp.1979, KatayamaInjecting oxygen before separating slag from steel
Ecomaister Co.,Ltd2014, S Y OhSpraying high pressure air and inert gas
Hanyang University2013, Shin and ParkInjecting oxygen on the molten RDP slags
Baosteel Co.,Ltd1991, Y M GuoDisposing RDP slags with the waste nitric acid
Mn fine ores!!!!Dispose the RDP slags innocuouslyProducts could be re-used in FeMn production
5th International Conference on Sustainable Solid Waste Management
Thermodynamics analysis
6
THEORETICAL ANALYSIS
∆Gθ change of Ca3P2 reacting with different manganese oxides(MnO2 ,Mn2O3 ,Mn3O4 ,MnO) at temperature of 1000-1800
The reaction sequence of Ca3P2 with manganese oxide is MnO2 >Mn2O3 >Mn3O4 >MnO. MnO is not easy to decompose and considered to be stable under the general conditions. Mn in the ore is assumed as MnO completely in the current study.
5th International Conference on Sustainable Solid Waste Management
Theoretical Calculation
7
THEORETICAL ANALYSIS
3 2 3 4 2( ) 8 ( ) ( ) ( ) 8 ( )Ca P s MnO s Ca PO s Mn s
The theoretical weight of manganese fine ore completely reacting with Ca3P2 in 1000g RDP slag is 28.30g (2.8 wt%).
Meet the critical requirements of Mn(Mn≥25%) and P/Mn ratio (P/Mn 0.006) of manganese ores used in FeMn alloy production, the minimum weight of manganese fine ores adopted in the innocent treatment process will be 672.18g and 1388.07g obtained from the calculation respectively.
The ratio between manganese fine ores and RDP slags should be over 1.388.
Dispose the hazardous Ca3P2 completely, meanwhile the products can be reused as raw materials for FeMn alloy production.
Calculate out the theoretical minimum amount of manganese ores used for innocent treatment of RDP slags based on the quality limitation of manganese ore.
5th International Conference on Sustainable Solid Waste Management
EXPERIMENTS Experimental details
8
No. High Si FeNi Fe-P Lime CaF2 Mn fine ore
1# 3.04kg 0.2kg 0.4kg 0.26kg 0.3kg2# 3.04kg 0.2kg 0.4kg 0.26kg 0.6kg3# 3.04kg 0.2kg 0.4kg 0.26kg 1.2kg
Experimental scheme
High-Si FeNi Stirring
Adding De-P slag
Adding Mn ores
Sampling SamplingAnalysis
Melting
5th International Conference on Sustainable Solid Waste Management
RESULTS & DISCUSSION
S
Treatment effect examined by AgNO3 test paper
9
The schematic diagram
2# and 3# disposed slag remained invariant color.
1# disposed slag changed the paper into black.
The discoloring sensitivity of AgNO3 test paper is 0.03mg/m3.
All the AgNO3 test paper used for testing RDP slags turned black.
5th International Conference on Sustainable Solid Waste Management
RESULTS & DISCUSSIONS
Treatment effect examined by XRD analysis
10
a1:1# RDP slag, a2:1# disposed slag, b1:2# RDP slag, b2:2# disposed slag, c1:3# RDP slag, c2:3# disposed slag
5th International Conference on Sustainable Solid Waste Management
RESULTS & DISCUSSIONS
Treatment effect examined by XRD analysis
11
a1:1# RDP slag, a2:1# disposed slag, b1:2# RDP slag, b2:2# disposed slag, c1:3# RDP slag, c2:3# disposed slag
Main phases in the RDP slags are CaF2, Ca3P2 and Ca2SiO4, which validated the existence of Ca3P2 in the RDP slags.
P in 2# and 3# RDP slags has been oxidized into higher valence states to form Ca3(PO4)2after treatment, 3# disposed slag had no PH3 generation during the test of AgNO3 test paper, which indicated 3# RDP slag is also innocent.
5th International Conference on Sustainable Solid Waste Management
RESULTS & DISCUSSION
S
The stability ofcurrent treatment method
12
P content of slag variation after 2 and 30 days exposed in the air
Significant declines of phosphorus content of 1#, 2# and 3# RDP slags from 2 days to 30 days, Ca3P2 reacted with H2O in the air and the phosphorus escaped as the PH3formation.
2# and 3# disposed slags, which are treated by sufficient manganese ore has nearly no variation after 30 days. Ca3P2 has been oxidized completely by manganese fine ores into the stable components.
5th International Conference on Sustainable Solid Waste Management
RESULTS & DISCUSSION
S
The stability ofcurrent treatment method
13
Surface morphologies of disposed slag after 30 days exposed in the air (a:1# disposed slag, b:2# disposed slag, c:3# disposed slag)
The 1# disposed slag pulverized after exposing in the air for 5 minutes and produced stinking smell, which would be the smell of PH3.
2# and 3# disposed slags, the experimental resultants are lumpy and keep the shape well after 30 days treatment .
The product for innocent treatment of RDP is recycled and somehow, the sintering process for fine manganese ores will not be necessary.
5th International Conference on Sustainable Solid Waste Management
The minimum quantity of manganese fine ore used to oxidize Ca3P2 into
Ca3(PO4)2 completely is 1.388 multiple of RDP slag to insure the product
could be reused in the FeMn production.
The main dephosphorization product is Ca3P2. Sufficient amount of Mn
fine ore can effectively oxidize the phosphorus of reduction state to high
valence states, further treat the RDP slag innocuously.
After 30 days placement of disposed slags which were treated by
sufficient manganese fine ore, the phosphorus content in the resultant is
stable, and the surface morphologies remained lumpy, which indicated
the feasibility and stability of current method.
CONCLUSIONS
14
