You might find it useful to read a real process description from this website about insulation manufacturing. The extract below looks very similar to a paragraph from an IELTS essay!
For glass wool, the raw materials are sand, limestone and soda ash, as well as recycled off-cuts from the production process. The raw materials are melted in a furnace at very high temperatures, typically between 1,300°C to 1,500°C. The smoke created during this process is filtered and flue gases are cleaned to minimise any environmental impact. The droplets of melt exiting the furnace are spun into fibres. Small quantities of binding agents are added to the fibres. The mineral wool is then hardened in a curing oven at around 200°C. The mineral wool is cut to the required size and shape.
Can you find the passive verbs in the paragraph above? Can you improve the paragraph by adding some sequencing words (firstly, then etc.)?