| With the increasing demand for phosphoric acid and the increasing consumption of lower grade phosphorous ore,the discharges of phosphogypsum continue to rise every year,but its utilization rate is relatively low which leads to the imbalance of phosphogypsum production and application.The problem of resources disposal of phosphogypsum urgently needs to be solved.Using phosphogypsum to make cement is an effective way to make use of its building materials resources.In industrial production,sulfoaluminate cement is more low carbon and energy saving than Portland cement.In order to improve the content of phosphogypsum in raw materials and realize energy saving and emission reduction of the process,under the guidance of the national "double carbon" strategy,this paper prepared sulfoaluminate cement with phosphogypsum as the main raw material,explored the optimal process calcination system and cement hydration performance,and simulated optimization of phosphogypsum cement co-production of sulfuric acid and sulfur by hydrogen reduction and decomposition of phosphogypsum.By controlling the rate of raw value design effective sulphur aluminate cement clinker mineral calcium sulphoaluminate(C4A3S?),dicalcium silicate(C2S)and the ratio of iron calcium aluminate four(C4AF),and then USES the phosphogypsum completely replace the raw limestone directly,through the way of mixed with coke-crucible with retain its weak reducing atmosphere,Metal ion ferric sulfate was added to the raw material to promote the decomposition of phosphogypsum.The influences of different C/S ratio(C/S),calcination temperature and holding time on mineral phase formation of cement clinker were explored.Results show that under the C/S = 2,850 ℃?950 ℃/1 h-air-1300 ℃/0.5 h calcination system of cement clinker produced clinker mineral C4A3S? and C2 S,in the case of choosing mixed gypsum,net of cement slurry is prepared specimens of 3 d compressive strength can reach 35.2 MPa,The compressive strength at 28 d reached 42.8 MPa.In the early hydration process,the hydration products of cement were AFt,and the late strength of cement increased slowly.When the cement clinker is mixed with 5% gypsum,the compressive strength of the cement paste is improved to a certain extent.It is feasible to use phosphogypsum to completely replace limestone to prepare sulfoaluminate cement clinker.Compared with traditional ingredients,the absorption of phosphogypsum can be increased by more than three times.Based on Aspen Plus chemical simulation software,taking the industrial production process of phosphogypsum with an annual capacity of 300,000 tons as an example,the system model of hydrogen reduction decomposition of phosphogypsum to make cement and the process model of production of sulfuric acid and sulfur from the tail gas SO2 of the kiln were established,and the sensitivity of the pre-decomposing furnace was analyzed.When the third air ventilation rate is 2071 kmol/h,the coal intake is 9750 kg/h,and the hydrogen intake is 140kmol/h,the raw material decomposition effect in the precalciner is the best and the coal consumption is the lowest.Using hydrogen instead of carbon to reduce phosphogypsum,reduce standard coal use by 3.3t /h,reduce CO2 emissions by 5.7t /h.The process of producing sulfuric acid and sulfur with low concentration of sulfur dioxide in the exhaust gas of the kiln was simulated.According to the simulated result of the process,the annual output of sulfuric acid solution with mass fraction of 99.2% was 113325 t.The production of sulfur simulated by sodium sulfide cycle method is 4.575 t/h,that is,the annual production is 36600 t. |
