A method for producing sulphoaluminate cement by segmental calcination of phosphogypsum

Abstract

The invention relates to a method for preparing sulphoaluminate cement by calcining ardealite by steps. Limestone and natural gypsum are completely replaced by ardealite, the ardealite is homogenized with bauxite, solid steel scrap and anthracite duff and then a method for calcining by steps is adopted for preparing the sulphoaluminate cement. According to the invention, the use ratio of the ardealite can be greatly increased and the high-concentration sulfur dioxide tail gas can be absorbed for preparing sulfuric acid. The sulphoaluminate cement prepared according to the invention is high in clinker hardening speed, high in early strength and stable in later strength. A performance test proves that the mechanical strength of the sulphoaluminate cement prepared according to the method provided by the invention meets the sulphoaluminate cement standard.

Description

Technical field: [0001] The invention belongs to the technical field of cement materials, and relates to a method for preparing sulphoaluminate cement by using phosphogypsum, which is waste from phosphorus chemical industry, as a raw material. Background technique: [0002] With the modernization of engineering technology, the technical requirements for special cement are getting higher and higher. These include the special requirements for the speed of rapid setting and hardening and the hardness of each stage during the construction of special projects, such as the connection construction of cement pipelines, and the construction of foundation sites for large-scale equipment. However, although the application and the sales market are constantly expanding, they are limited due to the high cost of the product, making more users out of reach. On the other hand, as one of the world's three major phosphate fertilizer producers, it is difficult to realize mass utilization due t...

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Problems solved by technology

[0003] Chinese patent document CN1401604A discloses a manufacturing process of fast-hardening sulfoaluminate cement. The raw material ratio of this process is 17-20% of dehydrated phosphogypsum, 45-52% of limestone, and 31-35% of bauxite. The successful use of waste phosphogypsum to replace the natural gypsum in the raw meal ratio can partially reduce the cost of sulphoaluminate cement, but the amount of phosphogypsum used in the process only accounts for 17-20% of the raw meal ratio. Invention 45-52% of limestone is also needed in the process, which can not achieve the purpose of effective utilization of phosphogypsum. In addition, the decomposition of phosphogypsum in the process will release sulfur dioxide, which will cause environmental pollution if not handled properly

[0004] Chinese patent document CN103304170A discloses a method for producing sulphoaluminate cement. Limestone, phosphogypsum, low-grade bauxite and coke are prepared in a certain proportion to make cement raw material, which is calcined at high temperature after grinding and mixing. In the process, by promoting the decomposition of phosphogypsum as much as possible, the calcium oxide generated by the decomposition replaces part of the limestone, and the sulfur dioxide gas can be collected to prepare sulfuric acid. The proportion of this process is 30-60 parts of limestone, 25-55 parts of phosphogypsum, and low-grade alumina 15-45 parts, this invention can also successfully use waste phosphogypsum to replace natural gypsum, which appropriately reduces the cost of cement, but phosphogypsum has not completely replaced limestone, and there are still as high as 30-60 parts of limestone in the raw material ratio, limestone The carbon dioxide produced by decomposition will greatly dilute the concentration of sulfur dioxide, which will increase the cost and difficulty of sulfuric acid production

By partially converting the phosphogypsum that does not require pretreatment, the mixture that meets the ingredients required for the production of sulphoaluminate cement is obtained, and no additional limestone is required, which expands the application range of phosphogypsum, but this process requires the conversion of phosphogypsum first. Calcium carbonate is then mixed with raw materials and calcined. The required equipment and process are relatively complicated, and the production cost is high.

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