Double-shell phase change heat storage balls and preparation method thereof

A preparation method for a double-shell phase change heat storage balls, comprising:

• Step 1:
• preparing raw materials with 50-70 wt % of a paraffin and 30-50 wt % of an organic ignition loss, placing the paraffin in an oven at 80-110° C. for 1-2 h to obtain a paraffin melt;
• then adding the organic ignition loss to produce a paraffin melt containing the ignition loss;
• then immersing metal balls in the paraffin melt containing the ignition loss for 10-20 s, and naturally cooling the immersed metal balls in a fume hood to prepare metal balls coated by ignition loss and paraffin;
• Step 2:
• placing 15-35 wt % of an alumina refractory slurry in a pan granulator, then adding 65-85 wt % of the metal balls coated by ignition loss and paraffin into the pan granulator, rotating the pan granulator at 10-20 r/min for 0.5-1 h, taking out and placing the pelletized metal balls in a fume hood for 4-6 h, and then maintaining a temperature at 80-110° C. for 20-24 h to prepare alumina composite phase change heat storage ball bodies;
• Step 3:
• placing 25-40 wt % of a mullite refractory slurry in a pan granulator, then adding 60-75 wt % of the alumina composite phase change heat storage ball bodies into the pan granulator, rotating the pan granulator at 10-20 r/min for 0.5-1 h, taking out and placing the pelletized ball bodies in a fume hood for 4-6 h, and then placing in an oven, maintaining at 80-110° C. for 20-24 h to prepare an alumina-mullite double-shell phase change heat storage ball bodies;
• Step 4:
• placing the alumina-mullite double-shell phase change heat storage ball bodies in a muffle furnace, increasing a temperature to 500-550° C. at a rate of 5-10° C./min, maintaining the temperature for 2-4 h, then increasing the temperature to 850-1100° C. at a rate of 3-5° C./min, maintaining the temperature for 3-5 h, then increasing the temperature to 1200-1600° C. at a rate of 2-5° C./min, maintaining the temperature for 3-5 h, and naturally cooling to room temperature to produce double-shell phase change heat storage balls;
• wherein a preparation method for the alumina refractory slurry comprises:
• premixing 80-90 wt % of a corundum fine powder, 3-5 wt % of an α-alumina powder, 4-8 wt % of a Guangxi clay, 1-3 wt % of a silica fine powder, 1-2 wt % of a calcium lignosulphonate and 1-2 wt % of a dextrin to obtain a premix;
• then adding 6-8 wt % of an aluminum dihydrogen phosphate solution and 8-10 wt % of water to the premix and stirring uniformly to prepare the alumina refractory slurry;
• and
• a preparation method for the mullite refractory slurry comprises:
• premixing 68-82 wt % of a mullite fine powder, 6-10 wt % of an α-alumina powder, 4-8 wt % of a Guangxi clay, 5-9 wt % of a silica fine powder, 1-2 wt % of a calcium lignosulphonate and 2-3 wt % of a dextrin to obtain a premix;
• then adding 6-8 wt % of an aluminum dihydrogen phosphate solution and 8-10 wt % of water to the premix and stirring uniformly to prepare the mullite refractory slurry.