Experimental Research On Recovery Of Ferric-contained Waste Hydrochloric Acid With Vacuum Distillation

Steel spent pickling liquor contains massive iron and free acid, if it was discharged directly; it not only creates a serious environmental pollution problem, but also causes waste of substantial resources. Spray Roasting is suitable for large companies, while medium-scale and small ones deal it with the traditional treatment method- neutralization, or entrust to commissioned units with dangerous waste disposal quality. However, the disposal of hydroxides sludge and the waste of resource limit the application of traditional treatment method. A new method of SPL regeneration was presented—a combination process of negative pressured distillation and wet preparation of iron oxide red, in order to provide guidance for industrialization application.The process includes the following stages: firstly, waste acid was treated with negative pressure distillation to obtain the regenerated hydrochloric acid after condensation and FeCl2 crystallization. Then, iron oxide was prepared using wet method, which included neutralization, drying and sintering preparation. This paper studied the following aspects with regard to the process.This paper firstly designed vacuum distillation treatment device. The effects of vacuum degree, temperature and time on the rate of recovery and concentration of HCl were studied. The results showed that the HCl recovery rate can reach 84.3%under 0.075 MPa vacuum degree and 76 ℃ temperature after 55 minutes of reaction,the regenerated acid was colorless with a concentration of 0.89 mol/L.This paper chose two kinds of neutralization agents to synthesize FeCO3 which were compared through single factor and orthogonal experiments. The results showed that the purity of iron oxide red can reach 99.0% with NH4+/Fe2+(n/n) of 2.6,NH4HCO3/(NH4)2CO3(n/n) of 5:4 and water bath temperature of 50 ℃, after 60 minutes of oscillation at the speed of 120 r/min. Drying experiment results showed that the color of the product was red brown after being dried for 3 h at the temperature of 80 ℃. Calcination experiment results showed that the purity of iron oxide red can reach 98.84% under the conditions of 700 ℃ and 1 h. The final product was2 3? ?Fe O, crystal grain size was well distributed and the shape of2 3? ?Fe O was porous spherical according to the characterization of XRD, FT-IR and EBSD. The pigment performance experiment results showed that the purity of self-made productsconformed to a standard of pigment red 101 in GB/T1863-2008, and other performance basically met the standard ofⅠor a.The process realized the comprehensive utilization of iron-containing hydrochloric acid pickling waste resources, which not only solved the problem of environmental pollution caused by waste acid, but also provided the raw material and a new process for the production of iron oxide pigment. Therefore, it was able to create a desirable social and economic benefits as well as environmental benefits.