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PLATINUM CATALYST GAUZE FOR NITRIC ACID PRODUCTION
SHI YICHUN, YANG DONG, HAN YONGQIANG, ZHAO MAIBIAN, AND ZHANG YU
China national chemical supply & sales corporation Taiyuan precious metals Co., LTD, Taiyuan, China
Annotation. Platinum or platinum rhodium catalyst gauze has been applied to production
process of nitric acid and hydrocyanic acid since 1909. Three kinds of catalyst gauze, woven gauze,
weft knitting gauze, and warp knitting gauze, were used in acid production process. Their advantage
and disadvantage were also introduced in this paper.
Keywords: catalyst, ammonia, platinum, rhodium, palladium.
Ammonia oxidized to nitrogen oxide is one of the major steps of nitric acid production.
Platinum or Platinum rhodium catalyst gauze has been applied to production process of nitric
acid and hydrocyanic acid since 1909. The catalyst gauze experienced the leap and change
from woven gauze to knitted gauze, weft knitted gauze to warp knitted gauze. It greatly
promoted the development of nitric acid industry.
The structures of the woven gauze, weft knitting gauze, and warp knitting gauze were
observed respectively in Fig.1 (a), (b), and (c). Wires of weft and warp crossed with each
other simply in Fig.1 (a). The design of woven gauze were rectangle grid, proportional
spacing, and two-dimensional. So active surface was reduced due to its structure. The
feature of weft knitted gauze was open circle, wires of every row did not cross in Fig.1 (b).
Though it has good stretch, mechanical stability is not good. Wire broken will cause stitches
dropping. However, warp knitted gauze was close circle, wires crossed with each other
roundly in Fig.1 (c). When a wire breaks, wires will tie around the broken. So it has good
mechanical stability because of no stitches dropping. Warp knitted gauze is in fine close
stitch and its stitch is adjustable, fully shows the advantage in technology, fully satisfies the
needs of high efficiency and quality catalyst gauze for nitric acid production.
Fig.1. The structures of the woven gauze, weft knitting gauze, and warp knitting gauze
Compared with woven gauze, knitted gauze has larger effective surface area in Fig.2.
Greater surface area for catalysis because of the three-dimensional structure. Though they
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had the same crystallization period, knitted gauze had longer conversion limitation than wove
gauze’s. Compared with woven gauze, warp knitted gauze also has lower gas-flow
resistance, higher ammonia conversion ratio, less Rh2O3 formation, lower platinum and
rhodium loss (Fig.3.), less raw materials, shorter production time, and longer service life.
Warp knitted gauze makes up for the lack of weft knitted gauze and represent the most
advanced level of the platinum catalyst gauze in the world.
Fig.2. Comparison of active surface. (a) woven gauze, (b) knitted gauze
Fig.3. Comparison of Pt/Rh losses.
System condition: 750 tons HNO3/day, pressure: 4 bars,
temperature: 890 ºС, nitrogen loading:13 tons N2/m2·day
Six kinds of alloy wires were used in our production. These are listed in table 1 along
with percent and diameter of wires. Gauze types are also listed in table 2 along with their
diameters.
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Table 1. Alloy varieties used in production
Alloy variety
Pt/Rh
Pt/Rh
Pt/Rh
Pt/Rh
Pt/Rh/Pd
Pt/Rh/Pd
Percent( %)
90/10
92/8
93/7
95/5
92.5/3.7/3.8
90/5/5
Diameter of wires (mm)
0.06/0.076
0.06/0.076
0.06/0.076
0.06/0.076
0.06/0.076/0.09
0.06/0.076/0.09
Table 2. Main products
Gauze type
Woven gauze
Weft knitting gauze
Warp knitting gauze
Diameter of gauzes (mm)
770/860/1050/1120/1500/1640/1750/2060/2540/2570
2875/3050/3345/3760/demands of customers
770/860/1050/1120/1500/1640/1750/2060/2540/
2875/3050/3345/3760/demands of customers
770/860/1050/1120/1500/1640/1750/2060/2540/
2875/3050/3345/3760/3880/demands of customers
China national chemical supply & sales corporation Taiyuan precious metals Co.,
LTD is a hi-tech enterprise in the Taiyuan Hi-tech Industries Development Zone financed by
China Chemical Supply & Sales (Group) Corporation, with registered assets of RMB 45.79
million, mainly manufactures the series of catalyst gauzes of HUAJIN Brand for nitric acid
production, researches and develops series of precious metals, as well as recovers and
refines platinum group metals(PGM), and cooperates with JM of England in purification and
PGM recovery of nitric acid production system. The company possesses the right of import
and export management, and passed the authentication of ISO9002 Quality system on
November 2 of 1999.
The China National Offshore Oil Corporation (CNOOC) recombined the China
Chemical Supply & Sales (Group) Corporation in May 2007. It means more chance and
more cooperation. China national chemical supply & sales corporation Taiyuan precious
metals Co., LTD will create a brighter future for the platinum catalyst development based on
newer skills, newer productions, lower cost, higher quality and more powerful strength.
Warmly-welcome to visit our company and joint development.