| With the development of social economy,there are many serious environmental pollution problems in our country and the heavy metal pollution is one of them.there are mainly five kinds of heavy metal pollution that is relatively serious in our country,of which the arsenic pollution is one.Nonferrous metal mine tailings enriched by dressing can be reused as a raw material for steel plant recycling of resources.But after enrichment,tailings cannot meet the requirements of blast furnace on raw materials due to the high arsenic content.Therefore,tailings after enrichment need further arsenic removal.In this study,oxidizing roasting and reduction roasting processes were used and compared to remove the arsenic in the enriched river tailings,and the effect of calcination temperature,air flow rate,residence time,feed particle size and other main influence factors on arsenic removal was evaluated.At the same time,the redox behavior of arsenic minerals in the heating process was studied to illustrate the mechanism of the two kinds of dearsenification process and get the suitable technological conditions of oxidizing roasting and reduction roasting.The results showed that:(1)Experiments show that the suitable oxidizing roasting conditions of high arsenic pyrite ore as follows:calcination temperature is 700～800 ℃,calcination time is about 60 minute,material thickness is 10～15 mm;The influence of the air flow is not obvious;Under the condition of appropriate roasting,the content of arsenic in roasting slag can reduce to about 0.4%,arsenic removing rate can reach more than 90%.(2)Appropriate coal base reduction roasting conditions:calcination temperature is 800℃、roasting time is 20 min,,at this time,arsenic content reduced to 0.32%,reduction roasting dearsenifying rate was 31.91%.Suitable air ’base reduction roasting conditions:calcination temperature is 900 ℃、roasting time is 30 min,CO/(CO+C02)concentration is 20%,gas flow rate is 0.5(m3/h),arsenic content at this time can be reduced to 0.058%,reduction roasting dearsenifying rate can reach 87.66%.(3)High arsenic pyrite ore contain many kinds of arsenic mineral,such as arsenic pyrite,arsenic sulfide in the form of sulphide mineral,arsenic oxide,arsenate in the form of oxide.Therefore,a single roasting atmosphere makes it difficult to remove all mineral arsenic,atmosphere control is a key factor of mineral arsenic removal;Arsenic mineral and other minerals disseminated relationship is relatively complex,part of the arsenic magnetic minerals and pyrite,iron oxide mixed intergrowth which will affect the volatilization of arsenic roasting process,so crushing the high arsenic pyrite ore to the appropriate particle size will also be good for arsenic removal;There are many different kinds of high arsenic pyrite mineral in the sand,especially metal compounds are easy reacted with As203 volatilizated in roasting process to generate arsenate which effect arsenic removal,thus control the temperature of the roasting and atmosphere conditions,inhibiting the production of arsenic acid salt in roasting process are the key reasons for removing arsenic.(4)The effect of removing arsenic in coal base roasting is obviously better than the air base reduction roasting,through gas reduction roasting of the high arsenic pyrite sand oxidation roasting slag can obtain qualified steel raw material.(5)Treatment of arsenic material depends on the existence of arsenic form,as the arsenic mainly exists in the form of arsenic sulfide,arsenopyrite,it is appropriate to use oxidizing roasting process;And as arsenic exists in the form of arsenate,it is appropriate to use weak reduction roasting process. |
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