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topic 12373p.4

Zinc oxide production by French process

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A discussion started in 2002 but continuing through 2020

May 28, 2008

I am into Hot Dip Galvanising Business. I am planning to venture into Zinc Oxide and Zinc Sulphate production business. I have gone through the posting in the forum. They are invaluable.

As first information, I would appreciate if you could provide me information on
1) what amount of Zinc Dross would produce what amount of Zinc Oxide.

2) cost of machinery.

Keeping in mind, the plant would target a production of 150 MT/month of ZnO.

I would appreciate if anyone is aware of the same regarding production of Zinc Sulfate.

Thanks in Advance.

VN Reddy
- Hyderabad, India

June 3, 2008

Dear Umesh,

Thank you for the explanation on reasons for drop in Yield with use of HG.
as I understand if I begin with 95% pure Zinc Ingot, then effectively,
I should be able to get only 1: 1.15% Oxide Yield depending on the Pb & Fe impurities ?

also, I wanted to further enquire on process conditions which could help
reduce the Grit & Ash and improve the Yield ? should I reduce the charge/time/furnace ?
regards, Vinay

Vinay Dhawan
manufacturer - BKK -Thailand

June 11, 2008

Dear Mr. Vinay Dhawan,
using dross in zinc oxide process is commercial decision. You can utilize most of metallic zinc from dross by avoiding skimming. for grit and heavy particles removal use gravity settlers effectively. You can get 99.7% zinc oxide from dross. in this process dross of 90% minimum can be used efficiently.
Process controls, variable settling systems will give good quality zinc oxide from dross.

Umesh Charki
- Thane, India

June 16, 2008

Dear Umesh,

I agree to your views regarding Use of Electric furnace for ZnO production.However following issues are vital.First,Can All types of Zinc Dross be efficiently used in E-Furnace ? Or only Molten Zinc is to be transferred in the Furnace.

Secondly the Life of the Furnace and skilled manpower to run these e-furnaces,as mostly in India 99% furnaces are still Oil fired ones.

Lastly the availability of Continuous power of min 100 kW to run one furnace ?

Awaiting your views.


- Alwar, Rajasthan, India

June 17, 2008

Dear Ankurji,
I am also working on electrical furnace. The power consumption is 800-900 KWH per Mt zinc oxide. This is single crucible furnace. Using heating elements. This resistance heating type furnace. You can operate as oil fired furnace. no special skilled workers are required. care is taken to deal with liquid zinc spillage, dust, crucible breakage detection etc. issues.
In some part of India electricity is no problem. Like in South India, you can install wind mill and get power from Electricity board. There are so many ways to go for non-conventional energy sources.
This is time to go for such things never thought in zinc oxide field.

Inputs are welcome,

Umesh Charki
- Thane, India

September 14, 2008

we are manufacturing zinc oxide white seal from galvanising bottom dross. we are getting yield as 1 : 1.12 generally. we use furnace oil as a fuel and it generally takes 220 liters per ton of zinc dross. initially when crucible is new fuel consumption is lower but after using nearly 20 MT dross it takes more time as well as consumes more fuel. we use LAP 1 type burner and 3 HP 2800 RPM air blower.

can I do any modification in burner or air blower to reduce fuel consumption?

Sunil Aghara
Director - Morbi, Gujarat, India

September 29, 2008

Dear Mr. Umesh Charki,

Thanks for clarifications on HG & Dross Yield.
now, we are looking to expand/add more 4 furnaces
& want to completely redesign our plant .

best regards, Vinay

Vinay Dhawan
Manufacturer - Thailand

October 22, 2008

Dear Friends,

Nice to meet you all..

We are Zinc Oxide manufacturer in Indonesia..
We want to know new information, innovation, research and maybe new application of Zinc Oxide..

I hope will get something important from this discuss for me to develop my factory in Indonesia.

Thank you for your kind attention..

Best regards

Hendra Gunawan
manufacturer of zinc oxide - Indonesia

November 3, 2008

Dear Mr Umesh Charki our company is a leading manufacturer in ceramic field. Currently we have a plan to produce zinc oxide from zinc with the total capacity of at least 1000 tons/months. If you are interested in cooperating with us, please contact me as soon as possible. I hope with your expertise we can save a great deal of time for not testing all the configurations.

Khanh Nguyen
- Vietnam

Ed. note: People have offered great info on this page, especially Umesh Charki. Thanks! Please remember that this site is made possible through the generosity of our supporting advertisers for camaraderie & public exchange of technical tips. Our advertisers are pleased to see this camaraderie and exchange of tips, but they obviously do not want their money spent putting potential customers into private contact with their competitors, nor steering people towards someone else's proprietary technology! Share what non-proprietary public tips you can, but if you want commercial benefit from this site, you need to become a supporting advertiser, not expect others to pay for your advertisements. Thanks.

November 12, 2008

Greetings Readers - For your information - The second International ZnO conference (organised by the International Zinc Association, Brussels) will be held at Rancho las Palmas, Palm Springs, California, USA on February 24th and 25th, 2009. We hope to build on the success of last year's meeting and we look forward to meeting readers again next year.
Best wishes,

Peter Robinson
- Fergus, Ontario, Canada

November 13, 2008

Dear Mr. Nguyen,
Installing plant with capacity 1000 MT/Month is good job. Before installing we should check for the quality required. So finalisation of plant setup and raw material can be specified.

Umesh Charki
- Thane, India

December 12, 2008

Dear readers,

I'm just new into ZnO and we are putting up a plant in Haryana for Zinc oxide by French process and only source with virgin Zinc ingots. I have some Q regarding my project

1. How to get smaller particle size at least to introduce in pharma sector ? And does the diameter of cooling duct effect the particle size?

2. What are the other factors involved in particle size like , size of hood and duct, suction speed of blower , furnace temperature , and handling or packing ?

3. By which test I can get the surface area in M sqr / gram for zinc oxide?

I would appreciate for any answer.

Thanks .

Suvneet Kalsi (Project manager)
- Delhi, India

December 15, 2008

Dear Suvneetji,
Zinc oxide particle size is depend upon cooling pattern of ZnO after formation. This is gas phase reaction with product in solid form.
French process limitation is to produce ZnO with surface area from 2 m2/ gm to 10 m2/gm with wide particle size distribution.
Hood design is also important as it gives such flow pattern to disperse and mix zinc vapour and atmospheric oxygen, just like combustion of fuel.
As this is gas phase reaction, partial pressures of reactants are also important.
You can measure surface area with BET method of nitrogen condensation.

Umesh Charki
- Thane, India

December 17, 2008

Dear Mr.Umesh Charki ji,
Thanks for your reply. Sir, as you said we get surface area between 2-10 with wide distribution, but our requirement is for between 7-10, So Can you tell that what should be the proper separation to get maximum output of 7-10 and in what percentage we can expect out of total production.

On the other hand I want to ask is there any defined cooling system for cooling duct or it is naturally done. Presently we are getting 5-7 surface area.

One more thing what is partial pressure of reactants actually?

Hope to see you again.

Suvneet Singh
- New Delhi, India

December 28, 2008

Dear Suvneetji,
French process can produce 2-10 Sq mt./ gm. But it requires different set of parameters. Generally this setup produces 4-7 For higher surface area we need to design reaction in proper manner.
We are using natural cooling for this process as it is cheapest method available. And surface area is depend upon cooling rate to 450 °C; below this temp. surface area does not changes effectively.

Partial pressure is percentage of every reactant in reaction mixture for gas phase reaction.

Umesh Charki
- Thane, India

December 30, 2008

Dear Umesh ji,
Thanks for your mail again,
we are putting up a new furnace of one crucible of capacity 800 kgs to get the better results.

I have a query regarding the distance between the top of the crucible and lower end of the hood. Does it help me to get the better results regarding surface area?
I want to increase the distance because to get the more air intake. presently we have 10-12 inches of gap.

If I put insulation on hood to keep it hot does it help me to get better results ?

Hope you have answers for that.

Thanks and regards

Suvneet Kalsi
- New Delhi, India

January 1, 2009

Dear Suvneetji,
We install two crucible furnace to increase holding capacity of the furnace. Due to high holding capacity zinc dilution is possible for reducing lead content in product. In this case we can increase vapourisation time to increase productivity. Because more zinc we vapourise in 24 hrs will be add more production capacity with good fuel efficiency.
Distance between crucible top and lower end of hood defines velocity of the air at entry point. here high velocity results in better mixing of air and zinc vapours. the distance you are having is sufficient. For more surface area we need to cool down zinc oxide formed. More cold air will result in more quenching of zinc oxide formed. so you concentrate on the air volume to be suck in the system.
Putting insulation will damage the hood earlier, as it is made of MS and need to operate below 300-400 °C. And cooling of the zinc oxide is done by the air entering in the hood from bottom.
I hope most of the queries cleared,

Umesh Charki
- Thane, India

February 20, 2009

Dear Sunil,

About energy consumption for French process of Zinc Oxide production, it ranges in a wide scope, from 120 L to over 250 L heavy oil per ton Zinc Oxide. Basically, the energy consumption is quite dependent on the furnace design.
During zinc oxide production, since the crucible wall is porous, the zinc vapor is trying to penetrating the crucible wall. This penetration accelerates especially when the furnace operates at very high temperature. And the penetrated zinc will oxide and deposit on the outside of the crucible wall. Once this deposit happens, the crucible will start to lower its thermal conductivity and fuel consumption will go up. So if you monitor the fuel consumption, you will find the fuel consumption is lower when the new crucible is used and after a few weeks the energy consumption will go up. In this case, an Isostatic pressed crucible with higher density/lower porosity will be better for French process.

For higher surface(higher BET) Zinc oxide:
zinc oxide produced from French process usually is lower surface area below 10 m2/g. However I believe it is possible to produce a higher surface area zinc oxide by French process. As said by Mr. Umesh Charki, French process for zinc oxide is a gas reaction, so it is quite possible to produce a higher Surface area ZnO by adjusting the parameters in the following reaction:
Zn(l) =>Zn(g)
Zn(g)+O2(g) =>ZnO(g)
ZnO(g) =>ZnO(s)
Such parameters as temperatures, pressure of Zn(g),O2 would be very important.
Normally these parameters are not controlled by the zinc oxide producers.

Hope this helps you.

Jiyang Chen
- SuZhou, China

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