Use of a liquid phase additive composition in a process for thermal cracking of petroleum residue selected from vacuum residue, atmospheric residue, deasphalted oil, shale oil, coal tar, clarified oil, residual oils, thermal pyrolytic tar, visbreaker streams, heavy waxy distillates, foots oil, slop oil or blends of such hydrocarbons, by delayed coking, comprising the process the steps of: (a) feeding the petroleum residue in a delayed coker reactor unit, (b) mixing the liquid phase additive composition in a range between 1000 and 20000 ppm with the petroleum residue before entering the feed heater furnace, in the transfer line or in the feed surge drum or storage tank, consisting said liquid phase additive composition of: (i) an alkyl nitrate in the range of 30 to 90 % w/w, wherein the alkyl nitrate is selected from 2-ethylhexyl nitrate and isopropyl nitrate; (ii) a petroleum sulphonates in the range of 2 to 30 % w/w, wherein the petroleum sulphonates is calcium petroleum sulphonates of less than 100 TBN; (iii) an aliphatic, aromatic, cyclohexylamines or hetroalkylated lower amines in the range of 1 to 10 % w/w, wherein the aliphatic, aromatic, cyclohexylamines or hetroalkylated lower amines are selected from dimethyl-cyclohexylamine, dibutylamine, mono & di-ethanol amine, and benzylamine; (iv) a hindered phenol based compounds in the range of 0.1 to 5 % w/w, wherein the hindered phenol based compounds is selected from 2,6 ditertiary-butyl-4-methyl-phenol, 2,4 dimethyl-6-tertiary-butyl-phenol, and 2,6 ditertiary-butyl-phenol; (v) a phosphate esters in the range of 1 to 15 % w/w, wherein the phosphate esters is selected from trialkyl, and triaryl phosphates; and (vi) an aliphatic alcohols in the range of 1 to 20 % w/w, wherein the aliphatic alcohols is selected from butanol, hexanol, 2-ethylhexanol and mixtures thereof; (c) heating the reactor at a temperature ranging from 450 to 600 °C with a pressure inside coke drum ranging from 0.5 to 5 kg/cm 2. (a) feeding the petroleum residue in a delayed coker reactor unit, (b) mixing the liquid phase additive composition in a range between 1000 and 20000 ppm with the petroleum residue before entering the feed heater furnace, in the transfer line or in the feed surge drum or storage tank, consisting said liquid phase additive composition of: (i) an alkyl nitrate in the range of 30 to 90 % w/w, wherein the alkyl nitrate is selected from 2-ethylhexyl nitrate and isopropyl nitrate; (ii) a petroleum sulphonates in the range of 2 to 30 % w/w, wherein the petroleum sulphonates is calcium petroleum sulphonates of less than 100 TBN; (iii) an aliphatic, aromatic, cyclohexylamines or hetroalkylated lower amines in the range of 1 to 10 % w/w, wherein the aliphatic, aromatic, cyclohexylamines or hetroalkylated lower amines are selected from dimethyl-cyclohexylamine, dibutylamine, mono & di-ethanol amine, and benzylamine; (iv) a hindered phenol based compounds in the range of 0.1 to 5 % w/w, wherein the hindered phenol based compounds is selected from 2,6 ditertiary-butyl-4-methyl-phenol, 2,4 dimethyl-6-tertiary-butyl-phenol, and 2,6 ditertiary-butyl-phenol; (v) a phosphate esters in the range of 1 to 15 % w/w, wherein the phosphate esters is selected from trialkyl, and triaryl phosphates; and (vi) an aliphatic alcohols in the range of 1 to 20 % w/w, wherein the aliphatic alcohols is selected from butanol, hexanol, 2-ethylhexanol and mixtures thereof; (i) an alkyl nitrate in the range of 30 to 90 % w/w, wherein the alkyl nitrate is selected from 2-ethylhexyl nitrate and isopropyl nitrate; (ii) a petroleum sulphonates in the range of 2 to 30 % w/w, wherein the petroleum sulphonates is calcium petroleum sulphonates of less than 100 TBN; (iii) an aliphatic, aromatic, cyclohexylamines or hetroalkylated lower amines in the range of 1 to 10 % w/w, wherein the aliphatic, aromatic, cyclohexylamines or hetroalkylated lower amines are selected from dimethyl-cyclohexylamine, dibutylamine, mono & di-ethanol amine, and benzylamine; (iv) a hindered phenol based compounds in the range of 0.1 to 5 % w/w, wherein the hindered phenol based compounds is selected from 2,6 ditertiary-butyl-4-methyl-phenol, 2,4 dimethyl-6-tertiary-butyl-phenol, and 2,6 ditertiary-butyl-phenol; (v) a phosphate esters in the range of 1 to 15 % w/w, wherein the phosphate esters is selected from trialkyl, and triaryl phosphates; and (vi) an aliphatic alcohols in the range of 1 to 20 % w/w, wherein the aliphatic alcohols is selected from butanol, hexanol, 2-ethylhexanol and mixtures thereof; (c) heating the reactor at a temperature ranging from 450 to 600 °C with a pressure inside coke drum ranging from 0.5 to 5 kg/cm 2.