Kraft pulp mill scale control with end group modified polycarboxylates

Abstract

Scale build-up on metal surfaces of a black liquor evaporator is prevented or mitigated by treating the black liquor with a deposit inhibiting concentration of a water-soluble polymer containing a polycarboxylate chain and a 3-mercaptopropionic acid end group.

What is claimed is: 
     
         1 . A method for inhibiting scale build-up on metal surfaces of a black liquor evaporator, the method comprising treating the black liquor with a deposit inhibiting concentration of a water-soluble polymer comprising a polycarboxylate chain and a 3-mercaptopropionic acid end group. 
     
     
         2 . The method according to  claim 1 , wherein the water-soluble polymer has general structure R1-R2-R3, wherein R2 is a polycarboxylate, R1 and R3 are independently hydrogen or an end group, and at least one of R1 and R3 is the end group —S—CH 2 CH 2 COOH. 
     
     
         3 . The method according to  claim 1 , wherein the water-soluble polymer comprises a homopolymer or copolymer of acrylic acid. 
     
     
         4 . The method according to  claim 1 , wherein the concentration of the water-soluble polymer in the black liquor is 100 ppm or greater. 
     
     
         5 . The method according to  claim 1 , wherein the water-soluble polymer has a weight average molecular weight of 2000 to 12000 daltons. 
     
     
         6 . The method according to  claim 1 , wherein the water-soluble polymer is a homopolymer or copolymer of acrylic acid chain terminated with 3-mercaptopropionic acid. 
     
     
         7 . A composition comprising black liquor and 50 ppm or more of a water-soluble polymer comprising a polycarboxylate chain and a 3-mercaptopropionic acid end group. 
     
     
         8 . The composition according to  claim 7 , wherein the black liquor has at least 50% solids by weight. 
     
     
         9 . The composition according to  claim 7 , wherein the water-soluble polymer has general structure R1-R2-R3, wherein R2 is a polycarboxylate, R1 and R3 are independently hydrogen or an end group, and at least one of R1 and R3 is the end group —S—CH 2 CH 2 COOH. 
     
     
         10 . The composition according to  claim 7 , wherein the water-soluble polymer comprises a homopolymer or copolymer of acrylic acid. 
     
     
         11 . The composition according to  claim 7 , wherein the concentration of the water-soluble polymer is 100 ppm or greater. 
     
     
         12 . The composition according to  claim 7 , wherein the water-soluble polymer has a weight average molecular weight of 2000 to 12000 daltons. 
     
     
         13 . The composition according to  claim 7 , wherein the water-soluble polymer is a homopolymer or copolymer of acrylic acid chain terminated with 3-mercaptopropionic acid. 
     
     
         14 . A system for recovering waste material from a kraft pulp process for paper production comprising an evaporator for concentrating a weak black liquor to a heavy black liquor, wherein the evaporator comprises black liquor and a scale-inhibiting amount of a water-soluble polymer, wherein the water-soluble polymer comprises a polycarboxylate chain and a 3-mercaptopropionic acid end group. 
     
     
         15 . The system according to  claim 14 , wherein the black liquor has at least 50% solids by weight. 
     
     
         16 . The system according to  claim 14 , wherein the water-soluble polymer has general structure R1-R2-R3, wherein R2 is a polycarboxylate, R1 and R3 are independently hydrogen or an end group, and at least one of R1 and R3 is the end group —S—CH 2 CH 2 COOH. 
     
     
         17 . The system according to  claim 14 , wherein the water-soluble polymer comprises a homopolymer or copolymer of acrylic acid. 
     
     
         18 . The system according to  claim 14 , wherein the concentration of the water-soluble polymer is 100 ppm or greater. 
     
     
         19 . The system according to  claim 14 , wherein the water-soluble polymer has a weight average molecular weight of 2000 to 12000 daltons. 
     
     
         20 . The system according to  claim 17 , wherein the water-soluble polymer is a homopolymer or copolymer of acrylic acid chain terminated with 3-mercaptopropionic acid.