China limestone carving-China's light calcium carbonate application

Light calcium carbonate is made of limestone as raw material and is made by carbonization method. It is mainly used in the production of rubber, plastic, paper and paint, ink and other industrial fillers and can be used in daily chemical products such as toothpaste, toothpaste and cosmetics. Can be used in organic synthesis, metallurgy, glass and asbestos production.

Light calcium carbonate has more than 300 domestic production enterprises. According to statistics, from January to September 2002, the national production of light calcium carbonate 1.2121 million tons, the apparent consumption of 1.2683 million tons. At present, China's ultra-fine calcium production enterprises have not yet formed a scale, only Guangdong Enping Co., Ltd., Beijing Chemical Building Materials Factory, Hunan Daocao Zuo Nitrogen Group, Shanghai Huaming High-tech Group Company and other enterprises to produce ultra-fine calcium, About 30,000 tons.

At present, China's market price of ordinary light calcium carbonate 500-650 yuan / t, active light calcium carbonate price of 800-1200 yuan / t, ink with ultra-fine light calcium carbonate price of 1800-2000 yuan / t. The price of light calcium carbonate should be more than twice as high as that of heavy calcium carbonate.

At present, the domestic rubber industry is the largest user of light calcium carbonate, the amount of light calcium carbonate accounted for about 40% of the total product. It is expected that the growth rate of light calcium carbonate in the rubber industry is about 10%.

Paint, construction and other industries, the amount of light calcium carbonate accounted for about 30% of its total output. As the country has been vigorously implementing housing projects, the construction industry next year, a substantial increase in the award, the industry is expected to consume light calcium carbonate will grow about 14%.

The domestic plastics market, the amount of light calcium carbonate accounted for about 10% of the total output of light calcium carbonate. Calcium carbonate added in plastic can increase the plastic volume, reduce product costs, improve the dimensional stability of plastic products, hardness and rigidity, improve the processing performance of plastics. At present in the production and processing of PVC products in a small amount of use of light calcium carbonate can improve the tensile strength of PVC products. The quality of light calcium carbonate in addition to the quality of natural calcium carbonate decision, the calcination and other chemical reaction conditions and grading fineness is also very important factor.

Ink, toothpaste and other industries, the amount of light calcium carbonate accounted for about 10% of its total.

Paper industry is the most development potential of domestic calcium carbonate applications. With light calcium carbonate as paper filler, can improve the paper products whiteness and shielding, can make the paper mill to reduce the amount of pulp, significantly reduce production costs. At present, the amount of light calcium carbonate used in papermaking is 5% of the total output of light calcium carbonate. In the coastal development and release areas, many new and expanded large and medium-sized Chinese and foreign papermaking enterprises have adopted a neutral process, with the supporting With the development of these industries, the amount of light calcium carbonate will grow steadily, the market outlook is optimistic.

Looking at the domestic light calcium carbonate market, with Shanghai as the center of Jiangsu, Zhejiang coastal economically developed areas, rubber, plastics, ink, paper processing products manufacturing industry is relatively high, the demand for light calcium carbonate and high quality requirements, The main needs of ultra-fine calcium carbonate, ultra-fine calcium carbonate, paper-specific calcium carbonate and other high value-added calcium carbonate. In addition, Zhejiang Hangzhou, Ningbo, Jiangsu, Suzhou, Zhenjiang and other places, Guangdong, Shenzhen, Dongguan and other places, plastic processing, toy manufacturing industry developed a large demand for light calcium carbonate, mainly ordinary calcium carbonate and activated calcium carbonate, rubber With ultra-fine calcium carbonate, ink with ultra-fine calcium carbonate also have certain requirements.

China is the world's calcium carbonate resources and production power. At present, China's calcium carbonate industry, the total production capacity of 400 million t / a. However, the statistical results show that in China's calcium carbonate industry, with a certain value-added precipitation of calcium carbonate in the product structure of only 7.7%, which has a high value-added varieties of less than 0.5% of total capacity, while the foreign nano-super Fine calcium carbonate has formed a large-scale industrial production.

In recent years, China's annual imports of high-grade calcium carbonate products up to 60,000 -10 million t, the market has great potential. US crude calcium carbonate market price of 70-135 US dollars / t, fine calcium carbonate price of 15-275 US dollars / t, ultra-fine calcium carbonate price of 275-485 US dollars / t. Japanese market ultra-fine light calcium carbonate price of 434 US dollars / t.

Different industries on the requirements of different calcium carbonate products, so calcium carbonate products will be toward the series, fine high-grade direction.

In recent years, the United Kingdom, Spain, Japan and other countries of the calcium carbonate manufacturers have optimistic about our market in Guangdong, Jiangsu, Anhui, Zhejiang provinces have built some annual output of 2 to 5 million t superfine calcium carbonate of the wholly-owned or joint venture , The current British clay company has been in Anhui, the construction of 20,000 t / a ultra-fine calcium carbonate production plant for papermaking, and ready to build a set of 50,000 t / a production plant in Ningbo. Switzerland, the company also sent experts to visit China's calcium carbonate raw ore situation, to explore the possibility of cooperation with China. China's calcium carbonate market, the attractiveness of foreign companies can be seen, but also shows that ultra-fine calcium carbonate in China has a broad development prospects.

Ultrafine calcium carbonate (hereinafter referred to as ultra-fine calcium) refers to the primary particle size of 0.02-0.1μm between the calcium carbonate, calcium carbonate in the boutique, compared with the conventional powder material in the reinforcement, transparency , Dispersibility, thixotropy and leveling, etc. have shown significant advantages. Now, ultra-fine calcium is moving in the direction of specialization, refinement and function. According to the inorganic salt industry association carbonate branch in the first half of 2002 statistics, the domestic has been built, under construction and project of ultra-fine or nano-calcium carbonate enterprises more than 18, the total design scale of more than 250,000 tons.

In recent years, China's demand for nano-sized ultra-fine activated calcium carbonate is expected to grow at an annual rate of 15%. China's plastics, ink, special paper products, car paint and rubber several major industries on the nano-calcium carbonate have a greater demand, by 2005 is expected to increase to 80,000 t or more

According to the different carbonation process, China's ultra-fine calcium production methods can be divided into intermittent bubbling carbonization, continuous bubbling carbonation, continuous spray carbonation, high gravity reaction crystallization 4

China limestone carving-(1) intermittent bubbling carbonization

According to whether there is a stirring device in the carbonization tower, the method can be divided into ordinary intermittent bubbling carbonization and stirring type intermittent bubbling carbonization. The method is in the cone bottom cylinder carbonization tower by adding refined calcium hydroxide suspension and the appropriate additives, and then from the bottom of the end of carbon dioxide carbonation to get the desired calcium carbonate products. In the reaction process need to strictly control the reaction conditions, such as carbonation temperature, carbon dioxide flow, lime milk concentration and stirring speed, and add the appropriate additives. The method of investment less, simple operation, but the production is not continuous, low degree of automation, product quality is not stable, mainly in the product crystal shape is not easy to control, uneven distribution of particle size, different batches of product reproducibility is poor. At present, most manufacturers in the country to use this method to produce light calcium carbonate, the production of ultra-fine calcium carbonate must strictly control the reaction process parameters in order to improve the stability of different batches of products.

China limestone carving-(2) continuous bubbling carbonization

Continuous bubbling carbonization is generally carried out by two or three stages of carbonization process, that is, refined lime milk by the first carbonization tower for partial carbonization or get the reaction mixture, in the slurry tank by adding the appropriate additives into the second stage of carbonization tower Carbonization to produce the final product. The method can be used to control the carbonization temperature by cooling, so the nucleation, growth process and surface treatment of the crystal form are controlled by step-by-step process. Small particle size and particle size distribution. Now, some domestic calcium carbonate manufacturers can according to the needs of users, by strictly controlling the lime milk concentration, carbonization temperature, the type of additives and the ratio of the production of the required crystal and particle size products.

China limestone carving-(3) continuous spray carbonation method

Continuous spray carbonization process generally uses three series of carbonation process. The refined lime milk is sprayed from the top of the first stage carbonation column into 0.01-0.1mm droplets, and the carbon dioxide is fed from the bottom of the column. The reaction mixture flows out of the bottom of the column, into the slurry tank, and the appropriate dispersant is added. After the treatment, the second stage carbonization tower is sprayed and then carbonized, and then subjected to surface treatment to spray into the tertiary carbonization tower to obtain the final product. Its product size up to 40-80nm. 

The law for the Hebei University of Science and Technology patents, its technical concept is undoubtedly advanced to liquid as a dispersed phase for vapor-liquid mass transfer reaction, greatly increasing the vapor-liquid contact area, easy to form a large number of nuclei in the early reaction, Temperature production of ultra-fine calcium. However, due to the high investment in the process, the technology is more complex, the operation is more difficult, the more important problem is the nozzle atomization problem is difficult to solve, because in order to improve the nozzle atomization effect, it is necessary to reduce the nozzle aperture, and reduce the nozzle aperture is easy Cause clogging.