As the main product or the by-product, calcium formate has various production methods. The main method for producing calcium formate at present is to react with dilute formic acid and calcium carbonate or calcium hydroxide to generate calcium formate solution. After the insolubles are filtered out, and the filtrate is concentrated and crystallized. Then calcium formate product is produced through centrifugal separation and desiccation, while the mother liquor is recycled. The advantages of this method are the excellent product quality and low content of water insolubles in products. The deficiencies of that are complex progress, high energy consumption, high production costs, and low efficiency with the adoption of evaporation crystallization production process. Withal we have developed quicksand-like calcium formate production technology, which directly uses formic acid and calcium carbonate as the main raw materials to synthesize an ideal flowing sand formate calcium product in one step. The advantages of this technology are the short process, simple operation, low energy consumption and investment and production cost. Also the product is white, smooth and flowing sand-like crystal particles with high purity and excellent quality.
1.1 Reaction principle As formic acid is stronger than carbonic acid, formic acid reacts directly with calcium carbonate to produce calcium formate, Its reaction formula is: CaCO3+2HCOOH = Ca(HCOO)2 +CO2↑+H2O
1.2 The main raw materials and specifications
1.2.1 Formic acid Formic acid content ≥ 85.0%, Heavy metal (Pb) ≤ 0.001%.
1.2.2 Heavy calcium carbonate Calcium carbonate content ≥ 95%, fineness 200 mesh, heavy metal (calculated as Pb) ≤ 0.002%, magnesium content ≤ 2%, hydrochloric acid insoluble matter ≤ 0.5%, arsenic (AS) ≤ 0.002%.
1.3 Production process First, Add the raw heavy calcium carbonate powder to the reaction tank, and add an appropriate amount of mother liquor, then start stirring. Added dropwise concentrated formic acid to the reaction tank to a pH of 4 to 4.5 at room temperature, and the reaction is further continued for 15 minutes. Sand products of calcium formate are produced after centrifugation, air-flow dried and packaged, while mother liquor is recycled.
1.4 Production process conditions
1.4.1 In theory, the molar ratio of heavy calcium carbonate to formic acid is 1:2. In the course of the reaction, a large amount of CO2 will take away a small amount of formic acid, resulting in loss of formic acid. In addition, in order to ensure that the water-insoluble substances in the product are qualified, an excess of formic acid is required. Through the exploration of production, it is determined that the suitable material ratio of heavy calcium carbonate to formic acid is heavy calcium carbonate (95%): formic acid (85%)=1:0.83 weight ratio. The reaction was carried out at room temperature, stirring speed 60 r/min, reaction time 60 min.
1.4.2 Centrifugation The calcium formate formed by the reaction is a uniform crystalline granule, which is particularly prone to dehydration. A three-legged centrifuge is used for dehydration in the production. The type of filter fabric used is polyester plain 260. Centrifugal dehydration time is 15min, wet material moisture content is ≤ 5%.
1.4.2 Dry packaging Wet material crystallizes well, the water content is low. Tubular air dryer is selected and used in the production, with diameter φ300mm, length 20m, air volume 3 000m3 / h, drying temperature 150 ~ 180 °C. The packaging is 25kg woven bag lined with plastic bags.
The calcium formate produced by our company has high purity and good fluidity, which is suitable for use in fodder and mortars. We welcome requests for samples.