The reduction of phosphogypsum (PG) to lime slag and SO

2

using coke can effectively alleviate the environmental problems caused by PG. However

the PG decomposition temperature remains high and the product yield remains poor. By adding additives

the decomposition temperature can be further reduced and PG decomposition rate and product yield can be improved. However

the use of current additives such as Fe

2

O

3

and SiO

2

brings the problem of increasing economic cost. Therefore

it is proposed to use solid waste copper slag (CS) as a new additive to reduce PG to prepare SO

2

which can reduce the cost and meet the environmental benefits at the same time. The effects of proportion

temperature and thermostatic time on PG decomposition are investigated by experimental and kinetic analysis combined with FactSage thermodynamic calculations to optimize the roasting conditions. Finally

the reaction mechanism is proposed. It is found that adding CS to the coke and PG system can increase the rate of PG decomposition and SO

2

yield while lowering the PG decomposition temperature. For example

when the CS/PG mass ratio increases from 0 to 1

PG decomposition rate increases from 83.3

8% to 99.35%

SO

2

yield increases from 78.62% to 96.81%

and PG decomposition temperature decreases from 992.4 ℃ to 949.6 ℃. The optimal reaction parameters are CS/PG mass ratio of 1

Coke/PG mass ratio of 0.06 at 1100 ℃ for 20 min with 99.35% PG decomposition rate and 96.81% SO

2

yield. The process proceeds according to the following reactions:2CaSO

4

+0.7C+0.8Fe

2

SiO

4

→0.8Ca

2

SiO

4

+0.2Ca

2

Fe

2

O

5

+0.4Fe

3

O

4

+2SO

2

+0.7CO

2

Finally

a process for decomposing PG with coke and CS is proposed.