A method for producing feed-grade zinc oxide by sodium chloride-ammonia combined leaching

Abstract

The invention discloses a method for producing feed grade zinc oxide through sodium chloride-ammonia combined leaching. The method comprises the following steps: leaching smoke dust of a steel mill, purification and dust removal, distilling ammonia and depositing zinc and drying and calcining, wherein when the smoke dust of the steel mill is leached, ammonium hydroxide, ammonium bicarbonate and sodium chloride are taken as leaching agents. The method has the advantages a sodium chloride solution is added to leaching liquid, the zinc leaching speed and leaching rate in the smoke dust are improved, the fact that the leaching rate of impurities, such as iron, is extremely low can be further guaranteed, the zinc depositing speed during ammonia seperation is further accelerated, the chemical components and structure of a product are changed, a solution can be completely used for performing circulation ammonia absorption leaching utilization after ammonia separating and zinc depositing, andthe cost is saved; an adopted technology changes the phase components of a product intermediate, low calcination temperature can be adopted, a feed zinc oxide product with the content of high bulk density being capable of reaching greater than 99.0 percent, and the method has excellent economic benefit.

Description

technical field [0001] The invention belongs to the field of zinc oxide production, in particular to a method for producing feed-grade zinc oxide through sodium chloride-ammonia combined leaching. Background technique [0002] Feed zinc oxide is used as an additive in feed. Compared with other zinc sources, it has the following characteristics: good stability in feed, no caking, no denaturation, convenient for feed premix processing and long-term storage; little effect on vitamins in feed . It has special requirements on indicators, such as lead, arsenic, cadmium and other heavy metal indicators are strictly controlled, and its physical data such as bulk density also have special requirements. Its function is to prevent diarrhea in weaned piglets, promote digestion, increase growth rate and reduce mortality. If the mixture is uneven, the local zinc will exceed the standard, which will bring toxicity to animals. In order to enhance the mixing uniformity of the feed, the ph...

AI Technical Summary

Problems solved by technology

Although the hygienic indicators such as lead, arsenic, cadmium and other heavy metals can be controlled by this method, the bulk density of the product is difficult to meet the requirements of the feed zinc oxide bulk density; the compatibility with other mixtures is quite different, and the mixing uniformity is not ideal

[0004] Patent CN 102627313 A (a wet production process of feed-grade active zinc oxide) utilizes ammonia water and ammonium bicarbonate in the ammonia immersion liquid as the carbonization precipitation agent of the acid immersion liquid, no additional use of ammonia water and ammonium bicarbonate, reducing the The ammonia distillation link greatly reduces the production cost, but the problem is that the recovery rate of neutralization is low, the ammonium sulfate solution of the neutralization solution is difficult to recycle and use, and ZnSO is easily produced 4 ·(NH 4 ) 2 SO 4 Double salt precipitation affects product quality

[0010] The disadvantage of patent CN 102826592 A (a method for producing active zinc oxide by using zinc-containing blast furnace ash and slag) is that it needs to be calcined to enrich high-content secondary oxygen powder, the process is long, and the sedimentation is compounded with zinc hydroxide and zinc carbonate. Precipitation in the form of salt, high calcination temperature (above 500°C), high energy consumption

[0012] Traditional ammonia leaching process generally adopts ammonia water and ammonium bicarbonate to cooperate to produce leaching solution, as patent CN1456693 A (the method for producing low-bulk-density nano-zinc oxide by ammonia method), the problem that exists is: the polarization coefficient of ammonia (α NH3 =2.21×10 -24 cm 3 ) is small, and the permeability is weak, and the residual metal zinc content of the general leaching slag reaches more than 3%.

It is difficult to meet the bulk density requirements of feed-grade zinc oxide products, and only 95-98% of ordinary active zinc oxide products can be produced

There are also patents requiring ammonium chloride leaching, but there is a problem: the zinc ammonium complex is stable in the ammonium chloride system, and Zn in the ammonia analysis process is stable. 2+ It will not be completely precipitated, it is difficult to deposit zinc, and it cannot be reused to achieve circular leaching and continuous production.

The first method is not an economical and effective method to reduce the zinc load of blast furnace, but also brings environmental pollution

The second is to enrich zinc into the tailings, but the three products of iron concentrate, carbon concentrate, and tailings are out of balance, and high iron and carbon resources are still lost

The general characteristics of existing problems in wet zinc extraction are low zinc leaching rate, difficult recycling of leaching slag, failure to meet environmental protection requirements, serious equipment corrosion, sensitivity to raw material requirements, difficulty in process optimization, low production efficiency and steel mill output match etc.