Drying method of basic zinc carbonate_Industrial additives

Background and overview of drying methods for basic zinc carbonate

Basic zinc carbonate is in the form of white amorphous powder with a relative density of 4.42 to 4.45. Soluble in dilute acids and alkali, slightly soluble in ammonia and ammonium salts, insoluble in water, ethanol and acetone. It decomposes into carbon dioxide and zinc oxide at 300°C. It reacts with H₂O₂ to release CO₂ to form peroxide. Fluorescence can occur when heated at 250 to 500°C for different times and cooled to room temperature. Its uses include: making latex film products, pigments, rayon, catalytic desulfurizers, and medicinal uses as light astringents, preservatives, disinfectants and skin protectants.

Preparation of basic zinc carbonate by drying method

A production method of basic zinc carbonate, including the following steps:

(1) Add zinc suboxide to the sulfuric acid solution, stir and react to produce zinc sulfate solution;

The chemical equation for the reaction between zinc suboxide and sulfuric acid is:

ZnO+HSO＝ZnSO+HO

During this reaction, some by-products are generated, and the chemical equation of the reaction is:

PbO+HSO=PbSO↓+HO (PbSO precipitates in the form of precipitation)

FeO+HSO＝FeSO+HO

CuO+HSO＝CuSO+HO

CdO+HSO＝CdSO+HO

MnO+HSO＝MnSO+HO

(2) Add potassium permanganate and zinc powder to the zinc sulfate solution to remove impurities to obtain an impurity-free zinc sulfate solution;

The addition of potassium permanganate can remove the divalent iron ions and divalent manganese ions in the reaction solution, that is, the removal of FeSO and MnSO in the reaction solution. The reaction equation is:

2HO+3MnSO+2KMnO＝KSO+5MnO↓+2HSO

14HO+6FeSO+2KMnO＝KSO+6Fe(OH)↓+5HSO+2MnO↓

MnSO reacts with potassium permanganate to form manganese dioxide precipitate, which removes sodium manganese bicarbonate ions; FeSO reacts with potassium permanganate to form iron hydroxide precipitate, which removes iron ions;

(3) Add sodium carbonate aqueous solution to the impurity-removing zinc sulfate solution, stir and react until the pH of the solution is 6.5-7.5 at a temperature of 50-55°C, and then stir at a temperature of 45-65°C Down, continue stirring the reaction for 0.5-1h;

The chemical equation for the reaction between zinc sulfate and sodium carbonate is:

3ZnSO+3NaCO+3HO＝ZnCO·2Zn(OH)·HO+3NaSO+2CO↑

When the pH of the solution reaches 6.5-7.5, continue the stirring reaction with bromopyridine dihydrochloride for 0.5-1 hour at a temperature of 45-65°C, so that zinc sulfate and sodium carbonate can be fully mixed for reaction;

(4) Filter the reaction solution, wash the filter cake with purified water until the filtrate does not contain sulfate ions, dry the filter cake and crush it to obtain basic zinc carbonate. Since basic zinc carbonate is insoluble in water, washing the filter cake with water can remove water-soluble impurities, that is, remove sulfate radicals.

Drying method of basic zinc carbonate Drying method

The thermal energy sources used in traditional basic zinc carbonate drying methods are mostly coal, oil or natural gas. Basic zinc carbonate is dried directly or indirectly by burning these fuels. This method often results in a large amount of energy waste and emissions. A large amount of polluting gases such as carbon dioxide and sulfur dioxide are not conducive to energy conservation and environmental protection.

For example, some manufacturers that produce basic zinc carbonate use coal-fired boiler steam to dry basic zinc carbonate indirectly. Each ton of basic zinc carbonate product dried consumes 0.7 tons of standard coal, and every ton of standard coal burned It will emit 2.6 tons of carbon dioxide and 8.5 kilograms of sulfur dioxide. If a factory produces 3 tons of basic zinc carbonate every day, it will need to emit 5.6 tons of carbon dioxide waste gas and 18 kilograms of sulfur dioxide waste gas every day. Carbon dioxide and sulfur dioxide waste gas are the main causes of haze weather, which is a big departure from the current energy conservation and environmental protection policies.

CN201410401834.3 proposes a basic zinc carbonate drying device, which solves the problems in the prior art that the basic zinc carbonate drying process wastes energy, emits waste gas, and is not environmentally friendly. The technical solution of the present invention is realized as follows: a basic zinc carbonate drying device, including: a drying chamber and a solar water heater. A drying bed is provided below the drying chamber; the drying beds are arranged sequentially from top to bottom. It is composed of thermally conductive metal plates, water pipes and foam insulation boards;The output end of the solar water heater is connected to one end of the heat dissipation pipe through a hot water delivery pipe, and the other end of the heat dissipation pipe is connected to the input end of the solar water heater through a return pipe.

The working principle of the present invention is as follows:

Place the basic zinc carbonate material containing moisture on the heat-conducting metal plate of the drying bed in the drying room, and spread the material. The outdoor sunlight radiates to the basic zinc carbonate through the plastic film or glass on the top and around the drying chamber. On the upper surface of the zinc carbonate material; at the same time, the hot water in the solar water heater enters the hot water pipe in the drying bed through the hot water circulation pump under the action of the hot water circulation pump. The heat generated by the hot water pipe is transferred through the heat-conducting metal plate. Give the lower surface of the basic zinc carbonate material.

In this way, the upper and lower surfaces of the basic zinc carbonate material are heated and dried at the same time. The wet steam generated during the drying process is discharged through the windows on the top and both sides of the drying chamber, speeding up the drying speed.

After the hot water in the radiating water pipe is cooled by heat conduction, it flows back to the solar water heater through the return pipe and is reheated. This cycle is repeated to continuously heat and dry the materials on the drying bed.

Since basic zinc carbonate products do not have high temperatures and do not decompose when exposed to sunlight, the product quality will not change after drying.

Application of drying method of basic zinc carbonate

Basic zinc carbonate can be used to prepare zinc oxide: weigh 3g of basic zinc carbonate (D90=3.86μm) and add it to the suspension calcination device. The calcination temperature is 500°C, the gas flow rate is 0.3L/min, and the reaction is 30 minutes. The light yellow zinc oxide powder is obtained, which is nano-zinc oxide. Its SEM picture is as shown in Figure 1. The particle size is 0.76 μm (D90) detected by an SKC-1 light transmission particle size analyzer (Nanjing University of Technology). The specific surface area of ​​the sample was measured to be 34.066m2/g using the V-sorb2008 specific surface area meter, and the zinc oxide content in the powder was determined to be 99.8% using the EDTA-EDTA coordination titration method.