Process for producing biodiesel and related products

1. A process for producing biodiesel from a mixture, said process comprising the steps of:

(i) providing the mixture to a trans-esterification reaction vessel;

(ii) introducing trans-esterification conditions to the trans-esterification reaction vessel;

(iii) trans-esterifying the triglycerides in the mixture;

(iv) separating a phase comprising impurities from the mixture;

(v) providing a first purification of the trans-esterified mixture;

(vi) a second purification of the trans-esterified mixture; and

(vii) a third purification of the trans-esterified mixture;

wherein the separation step comprises spraying a 1.0% by weight to 1.8% by weight acid solution onto the surface of the mixture in the trans-esterification reaction vessel, the acid solution percolating the mixture and facilitating the removal of impurities therefrom; and

wherein the first purification of the trans-esterified mixture and the third purification of the trans-esterified mixture comprise spraying an aqueous solution onto the surface of the mixture in the trans-esterification reaction vessel, the aqueous solution percolating the mixture and facilitating the removal of impurities therefrom; and wherein the second purification of the trans-esterified mixture comprises spraying an acid solution onto the surface of the mixture in the trans-esterification reaction vessel, the acid solution percolating the mixture and facilitating the removal of impurities therefrom.

2. A process as claimed in claim 1 , wherein the process comprises the further step of heating the mixture to a reaction temperature for trans-esterification.

3. A process as claimed in claim 1 , wherein the process comprises the further step of maintaining the mixture at a reaction temperature for trans-esterification.

4. A process as claimed in claim 2 , wherein the trans-esterification reaction temperature is between 48° C. and 62° C.

5. A process as claimed in claim 1 , wherein the amount of FFAs in the mixture before trans-esterification is 3% by weight or less.

6. A process as claimed in claim 1 , wherein introducing trans-esterification conditions comprises adding a trans-esterification catalyst.

7. A process as claimed in claim 6 , wherein the trans-esterification catalyst is from 12% by weight to 14% by weight methoxide or a suitable salt thereof.

8. A process as claimed in claim 6 , wherein the mass of trans-esterification catalyst used relative to the % by weight FFAs in the mixture is from 1,000 kg per % by weight FFAs to 1,500 kg per % by weight FFAs.

9. A process as claimed in claim 1 , wherein the trans-esterification step comprises:

(i) a first trans-esterification step; and

(ii) a second trans-esterification step.

10. A process as claimed in claim 9 , wherein in the first trans-esterification step the mass of trans-esterification catalyst used relative to the % by weight FFAs in the mixture is from 1,000 kg catalyst per % by weight FFAs to 1,500 kg catalyst per % by weight FFAs.

11. A process as claimed in claim 9 , wherein in the second trans-esterification step the mass of trans-esterification catalyst used relative to the % by weight FFAs in the mixture is from 550 kg catalyst per % by weight FFAs to 650 kg catalyst per % by weight FFAs.

12. A process as claimed in claim 1 wherein the first purification step is carried out at a temperature of between 47° C. and 61° C.

13. A process as claimed in claim 1 , wherein the separation step is carried out at a temperature of between 48° C. and 62° C.

14. A process as claimed in claim 1 , wherein the second purification step comprises spraying a phosphoric acid solution onto the surface of the mixture in the trans-esterification reaction vessel, the acid solution percolating the mixture and facilitating the removal of impurities therefrom.

15. A process as claimed in claim 1 , wherein the second purification step is carried out at a temperature of between 47° C. and 61° C.

16. A process as claimed in claim 1 , wherein the acid solution in the second purification step is from 0.8% by weight acid to 1.6% by weight acid.

17. A process as claimed in claim 1 , wherein the second purification step is performed after the first purification step.

18. A process as claimed in claim 1 , wherein the third purification step comprises spraying water onto the surface of the mixture in the trans-esterification reaction vessel, the aqueous solution percolating the mixture and facilitating the removal of impurities therefrom.

19. A process as claimed in claim 1 , wherein the third purification step is carried out at a temperature of between 47° C. and 61° C.

20. A process as claimed in claim 1 , wherein the third purification step is performed after the second purification step.

21. A process as claimed in claim 1 , said process comprising the further step of distilling the mixture after purification, said distillation process configured to remove sulphur and/or sulphur containing materials from the mixture.

22. A process as claimed in claim 21 , wherein the distillation step comprises:

(i) a first distillation; and

(ii) a second distillation.

23. A process as claimed in claim 22 , wherein the distillation is under vacuum.

24. A process as claimed in claim 23 , wherein the distillation is carried out at a pressure of from 0.1 millibar (10 Pa) to 3 millibar (300 Pa).

25. A process as claimed in claim 22 , wherein in the first distillation step steam is injected at a pressure of from 3.5 bar (350 kPa) to 9 bar (900 kPa).

26. A process as claimed in claim 22 , wherein in the second distillation step steam is injected at a pressure of from 4.5 bar (450 kPa) to 11 bar (1,100 kPa).

27. A process as claimed in claim 1 , wherein the impurities are selected from one or more of group consisting of: glycerides, glycerol, methanol, water, salts, acids, bases, condensed volatile compounds and soaps.

28. A process as claimed in claim 1 , said process comprising the further step of removing the impurities from the mixture.

29. A process as claimed in claim 28 , said process comprising the further step of isolating one or more materials from the impurities, said isolated materials selected from one or more of the group consisting of: glycerides, glycerol, methanol and FFAs.

30. A process as claimed in claim 29 , wherein the isolated material is reused in the process or a subsequent process for producing biodiesel.

31. A process as claimed in claim 1 , said process comprising the additional step of esterifying the mixture before trans-esterifying the mixture, the mixture comprising between 10% and 20% by weight free fatty acids (FFAs) before esterification, said esterification process comprising the steps of:

(i) providing at least a first portion of the mixture to at least a first esterification reaction vessel;

(ii) heating the first portion of the mixture to a reaction temperature for esterification, the reaction temperature being between 71° C. and 76° C.;

(iii) introducing esterification conditions to the first esterification reaction vessel, comprising adding an esterification catalyst and an alcohol to the reaction vessel, the esterification catalyst being sulphuric acid;

(iv) stopping the heating of the first portion of the mixture;

(v) recirculating the first portion of the mixture by removing it from the first esterification reaction vessel and returning it to the first esterification reaction vessel; and

(vi) esterifying FFAs in the first portion of the mixture;

wherein the recirculation of the first portion of the mixture is configured to maintain a reaction temperature suitable for esterification of the FFAs in the first portion of the mixture, the reaction temperature being between 71° C. and 76° C.;

and wherein the mass of esterification catalyst used relative to the % by weight FFAs in the mixture before esterification is from 26 kg catalyst per % by weight FFAs to 32 kg catalyst per % by weight FFAs, such that the amount of FFAs in the mixture is reduced to 3% by weight or less.

32. A process as claimed in claim 31 , wherein there is provided two or more esterification reaction vessels, said process comprising the further steps of:

(i) providing at least a second portion of the mixture to at least a second esterification reaction vessel;

(ii) heating the second portion of the mixture to a reaction temperature for esterification, the reaction temperature being between 71° C. and 76° C.;

(iii) introducing esterification conditions to the second esterification reaction vessel, comprising adding an esterification catalyst and an alcohol to the reaction vessel, the esterification catalyst being sulphuric acid;

(iv) stopping the heating of the second portion of the mixture;

(v) recirculating the second portion of the mixture by removing it from the second esterification reaction vessel and returning it to the second esterification reaction vessel; and

(vi) esterifying the FFAs in the second portion of the mixture;

wherein the recirculation of the second portion of the mixture is configured to maintain a reaction temperature suitable for esterification of the FFAs in the second portion of the mixture, the reaction temperature being between 71° C. and 76° C.

33. A process as claimed in claim 32 , wherein the esterification of the first portion of the mixture and the esterification of the second portion of the mixture are at least partly concurrent.

34. A process as claimed in claim 31 , wherein the esterification reaction temperature is between 72° C. and 75° C.

35. A process as claimed in claim 31 , wherein the mixture comprises between 10% and 15% by weight FFAs before esterification.

36. A process as claimed in claim 31 , wherein the alcohol is methanol.

37. A process as claimed in claim 31 , wherein the esterification catalyst is 96% sulphuric acid.

38. A fuel comprising the biodiesel composition of claim 1 .

39. A fuel blend comprising the biodiesel composition of claim 1 and a petroleum diesel.