Control of Arsenic and Tin Contents in DNV Ship Plates

Abstract: Through the theoretical calculation of the arsenic and tin content requirements in the steelmaking process, ironmaking process, and sintering process, the requirements for the content of arsenic and tin in the mixed ore powder are finally determined, and the ore blending is carried out accordingly, so that the production of low arsenic, The DNV ship plate with high tin content achieved a one-time success. The actual production results show that the arsenic and tin in the raw materials all enter the sinter ore in the sintering process, and most of them enter the molten iron and slag in the ironmaking process-
Key words: DNV ship plate ; arsenic ; tin ; content

DNV ( Det Noiske Veritas ) ship plates are key products cultivated by Guangdong Shaoguan Iron and Steel Group Co. , Ltd. Grade, D36 grade steel plate factory approval certificate for hull structure, but it is stipulated that the content of arsenic ( As ), tin ( Sn ) and antimony ( Sb ) in all grades of DNV ship plates shall not exceed 0.02%. From the time of certificate issuance, all DNV ship plates This condition must be met , otherwise the product certificate will not be issued-
The test results show that before July 2007 , only the antimony content of the ship plates produced by Shaoguan Iron and Steel Co., Ltd. met this requirement , while the content of arsenic and tin was far from the requirements of Det Norske Veritas ( according to statistics , from May to June 2007 , the The average content of arsenic , tin and antimony in the smelting composition of steel and steel is 0.052% , 0.034% and 0.001% respectively). Therefore, it is necessary to calculate the content of arsenic and tin in each process of producing DNV ship plates, and take effective measures to formulate a reasonable ore mix plan to ensure that the content of arsenic and tin in the steel plate meets the requirements of DNV . Otherwise, it will not only affect the production and sales of Norwegian ship plate , but also And it affects the ship plate production of other classification societies , In turn, it will affect the quality image of Shaoguan Iron and Steel Co., Ltd.
1 Changes in tin and tin content in each process
arsenic in sintering and ironmaking has been studied : all the arsenic in the raw materials enters the sinter during the sintering process , and the arsenic volatilizes less during the ironmaking process , and the arsenic content in molten iron is roughly " concentrated " according to the ore consumption ratio  .
The behavior of tin in sintering and ironmaking is rarely mentioned in the literature . During ironmaking , iron oxides are reduced to metallic iron . Iron suboxides ( FO ) and tin oxides ( SnO 2 and SnO ) standard free energy of formation is very close to. High-valent oxides of iron are easily reduced , Its low-valent oxides are difficult to reduce, and the reduction proceeds in the following order: FeO 3 f FeOL FO * Fe - When FeO is reduced to FeO , SnO 2 can be reduced to metal [4] - During the ironmaking process, when iron When the oxide is reduced to metallic iron , Tin oxides are also reduced to metal tin. The melting point of tin is 232 width="100%">C and the boiling point is 2690 width="100%">C . Tin is a metal with low melting point and strong chemical stability [6] . Sintering , smelting The iron temperature is above the melting point of tin and below the boiling point. Based on this, it is speculated that tin should not volatilize and enter the flue gas during the sintering and ironmaking process, and all the tin in the raw materials of the sintering process should enter the sintering ore and the furnace charge of the ironmaking process Tin should also all enter the molten iron and slag .
2. Theoretical calculation of tin and tin control content in each process
According to the requirements of arsenic and tin content in the steel plate , the arsenic and tin content requirements are calculated inversely from the steelmaking process to the pre-iron process .
2.1 Arsenic and tin content requirements in ironmaking process
In order to ensure the stability of arsenic and tin content in steel scrap, only self-produced steel scrap ( steelmaking scrap billet head , billet tail, steel rolling intermediate scrap , finished product scrap, etc. ) is used when smelting DNV ship plate steel, and no purchased scrap steel is used .
According to the statistics of steel smelting composition in May - June 2007 , the average arsenic and tin contents of Shaoguan Iron & Steel were 0.052% and 0.034%, respectively .
Based on the weight ratio of molten iron and steel scrap as 71 , assuming that the contents of arsenic and tin in molten steel are 0.02% and 0.02% , the molten iron
As content =(0.02% -0.052% X 1/8) -7/8 = 0.015%
Sn content =(0.02% -0.034% X1/8) -7/8 = 0.018%
From the above analysis, it can be seen that if the content of arsenic and tin in DNV ship plate is not more than 0.02% and 0.02% respectively , the content of arsenic and tin in molten iron should not be more than 0.015% and 0.018% respectively .
2.2 Arsenic and tin content requirements in the sintering process
producing DNV ship plates, the blast furnace material structure is planned to be 66% sinter , 29% Brazilian pellets , and 5% Hainan lump ore .
Assumptions :
arsenic and tin in blast furnace fuels such as coke and PCI coal are both 0 ;
In the ironmaking process, all arsenic and tin enter the molten iron , and the content of arsenic and tin in the slag and flue gas is 0 ;
sinter , Brazil pellets and Hainan lump ore is shown in Table 1
Shown .
For example, if the content requirements of arsenic and tin in molten iron are 0.015% and 0.018% respectively , it can be deduced that the content requirements of arsenic and tin in sintered ore are 0.012% and 0.017% respectively . See Table 1 below for details .
Table 1 Calculation of arsenic and tin content in sinter

Mineral	Mixing ratio /%	w ( TFe ) /%	mine consumption ratio	Unit consumption t 1	w (As) /%	w ( Sn ) / %
Sinter	66 ． 000	56 ． 800		1049.358	0.012	0.017
Brazilian pellets	29 . 000	67 . 160		461.082	0.006	0.001
Hainan Lump	5 . 000	54 . 470	1 . 590	79.497	0.005	0.002
total	100 ． 000	59 ． 688		1589.937	0.015	0.018
Hot metal composition requirement				0.015	0.018

23 Arsenic and tin content requirements in the mixing process
producing DNV ship plate, the sintering batching structure is planned to be 62.3% mixed ore powder , 5.9% limestone , 2.8% quicklime , 4.0% coke powder , and 25.0% internal return ore .
and tin in the raw materials in the sintering process all enter the sinter . Mixed slag , gray marble , fuel , total iron in the returned ore , moisture content and burning loss , gray marble , fuel , returned ore arsenic , tin content are shown in Table 2 .
If the arsenic and tin content requirements of sinter are 0.012% and 0.017% respectively , it can be calculated that the arsenic and tin content requirements in the mixed ore powder are 0.014% and 0.023% respectively . See Table 2 below for details .

Table 2 Calculation of arsenic and tin content in mixed mineral powder %

name	Physical and chemical composition of raw materials				burn out	Proportion	ingredient calculation
	w(TFe)	w(As)	w (Sn)	moisture			Amount of dry material	Burning amount	w(TFe)	w (As)	w (Sn)
Mixed Mineral Powder	61.500	0.014	0.023	7.600	2.500	62.300	57.565	56.126	35.403	0.008	0.013
gray marble	0.000	0.001	0.001	1.000	45.000	5.900	5.841	3.213	0.000	0.000	0.000
quicklime	0.000	0.001	0.001	0.000	6.000	2.800	2.800	2.632	0.000	0.000	0.000
fuel	0.000	0.001	0.002	12.000	85.000	4.000	3.520	0.528	0.000	0.000	0.000
Return to mine	56.800	0.009	0.005	0.000	0.000	25.000	25.000	25.000	14.200	0.002	0.001
total						100.000	94.726	87.499	49.603	0.010	0.014
Sinter chemical composition requirements										0.012	0.017

4 Epilogue
1) All the arsenic and tin in the raw materials of the sintering process enter the sinter ; most of the arsenic and tin in the raw materials of the ironmaking process enter the molten iron and slag .
2) The measurement and calculation of arsenic and tin content should be strictly calculated according to the conditions of raw materials and fuels , such as changes in steelmaking , ironmaking , and sintering process conditions , especially the content of arsenic and tin in scrap steel , and the proportion of sinter and pellets in the blast furnace charge. When the proportion of mixed ore powder in the sintering raw material changes , it is necessary to recalculate the content of arsenic and tin in each process .

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