Sludge　disposal　and　resource　utilization　are　crucial　in　environmental　engineering.　This　study　innovatively　combines　sludge　incineration　slag　with　potassium　nitrate　to　prepare　medium-temperature　phase　change　thermal　storage　composites　via　the　cold　compression　and　hot　sintering　method.　Using　sewage　sludge　incineration　slag　as　the　skeleton　material　not　only　enhances　the　material＇s　stability　but　also　reduces　liquid　leakage　risk,　demonstrating　great　research　value　and　application　potential.　This　study　aims　to　investigate　the　impacts　of　particle　size,　pressing　pressure,　and　sintering　heating　rate　on　thermal　storage　performance.　The　results　indicate　that　sludge　and　potassium　nitrate　are　suitable　to　produce　shape-stable　phase　change　composites.　Under　the　optimized　conditions　of　a　mass　ratio　of　5:5　for　the　sewage　sludge　incineration　slag-KNO3　sample,　a　particle　size　of　300　mesh　for　the　skeleton　material,　a　sintering　heating　rate　of　10　°C/min　for　the　composites,　and　a　compression　pressure　of　3　MPa,　the　prepared　sample　300–10-3　M　exhibited　the　best　thermal　storage　performance.　This　sample　exhibited　a　latent　heat　value　of　56.74　J/g,　a　thermal　energy　storage　density　of　441.37　J/g,　and　a　maximum　thermal　conductivity　of　1.26　W/(m·K).　It　also　demonstrated　excellent　chemical　compatibility　between　its　components　and　a　uniform　distribution　of　elements.　Furthermore,　sample　300–10-3　M　possessed　a　mechanical　strength　of　72.98　MPa.　Importantly,　the　thermal　storage　cost　of　sample　300–10-3　M　was　very　low,　at　5.33　$/MJ,　indicating　significant　commercialization　potential.　©　2025