The　catalytic　effects　of　different　catalysts,　i.e.,　3%　Ca,　5%Na-BL,　and　3%　Ca+5%　Na-BL　catalyst,　on　carbon　conversion,　gasification　reaction　rate　constant,　activation　energy,　and　relative　amount　of　harmful　sulfur　containing　gases,　were　investigated　by　thermogravimetry　in　steam　gasification　under　temperature　700C　to　900C　at　ambient　pressure　for　two　Pakistani　Lakhra　(LKH)　and　Thar　(THR)　lignite　chars.　High　carbon　conversion　can　be　obtained　by　direct　gasification　of　both　LKH　and　THR　chars,　but　the　gasification　rate　became　much　fast　using　BL　catalyst.　THR　char　with　high　ash　content　was　easy　to　form　some　complex　silicates　during　BL　catalytic　gasification,　leading　to　a　lower　conversion　than　that　of　LKH　char　with　low　ash　content.　SO2　and　H2S　as　sulfur-containing　gases　produced　by　char　and　BL　itself　in　steam　gasification　can　be　captured　by　the　existence　of　Ca　mixed　with　BL,　which　is　more　effective　at　temperatures　less　than　900C.　The　shrinking　core　model　(SCM)　can　be　considered　as　a　better　choice　to　correlate　the　relations　between　conversion　and　time　and　to　estimate　the　reaction　rate　constant　(k)　under　different　temperatures.　The　reaction　activation　energy　(Ea)　and　pre-exponential　factor　(A)　were　predicted　based　on　Arrhenius　equation.　The　reaction　activation　energy　of　44.7　kJ/mol　and　59.6　kJ/mol　for　LKH　chars　with　BL+Ca　and　BL　catalysts　were　much　lower　than　114.6　kJ/mol　and　100.8　kJ/mol　for　THR　chars　with　the　same　catalysts,　respectively.　They　were　also　lower　than　161.2　kJ/mol　for　LKH　char　and　124.8　kJ/mol　for　THR　char　without　catalyst.