Saturday, 24 July 2010

Trafigura: Spent Caustic – A More Negative View

The entire Trafigura affair concerns the disposal of spent caustic, the waste left after coker naphtha was washed with caustic soda. 

Trafigura’s latest factsheet about which I posted yesterday had this to say.

“Gasoline washing is a common and legal process that reduces mercaptan levels in gasoline cargoes in order to meet specific contractual obligations.”


“Consequently the port [of Abidjan, Calum’s addition]  is highly experienced in dealing with slops from oil tankers and vessels and in 2006 more than 30,000 tonnes of slops were safely unloaded at Abidjan. Trafigura, as well as other major oil companies, have been operating in the Ivory Coast for decades.”

These are two short paragraphs from a very long document.

There is another view.

This morning I came across the website of a company  - - which specialises in treating spent caustic and I append a few of their statements which describe the waste and treatment in sober terms.

“Spent Caustics are the most difficult of all industrial wastes to dispose properly, with the exception of radionuclide wastes.  Since the dawn of petroleum refining, caustic solutions containing sodium hydroxide (common lye) have been used to wash sulfur and other undesirable compounds out of petroleum.  Its use has been in washing crude oils, intermediate fractions, and finished fuels throughout the refining processes.  The result of this washing is the generation of Spent Caustics, also called Waste Caustics and Toxic Wastes.”


“SPENT CAUSTICS are generated from many industrial processes.  Most are generated from the refining of petroleum to remove undesired SULFUR compounds from fuels. 

In the refining industry, the net hydrogen sulfide captured in spent caustics is too low for effective sulfur recovery in typical Sulfur Recovery Units (SRU's) employing the common Claus Process, therefore, the spent caustics must be disposed properly.  In addition to the toxic hydrogen sulfide, both toxic mercaptans and phenolics are often captured in spent caustics, severely limiting the disposal options.”



“Common to all spent caustics is a high concentration of the extremely deadly and odorous HYDROGEN SULFIDE, an acutely toxic gas most recognized as the odor of rotten eggs when in low ppb (parts per billion) concentrations.  Hydrogen sulfide gas readily dissolves in caustic solutions due to its solubility at high pH or "caustic pH" conditions, typically above pH 10 to 12.  It can be released from solution as a gas easily when the solution is disturbed or the pH is lowered.  It is more toxic than hydrogen cyanide to humans and death can occur in exposures of just 100 to 500 ppmv (parts per million by volume) in the atmosphere.”

“SPENT CAUSTICS contain noxious odor precursors that are highly toxic to humans and to our biosphere.  Toxic and hazardous substrates removed during gas scrubbing, fuel sweetening and hydrocarbon washing end up in the spent caustic.  These compounds must be transformed into non-hazardous and non-toxic compounds before being discharged back to the environment.  The TexoxTM Process accomplishes this daunting task through responsible and cost effective treatment programs.

SPENT CAUSTICS exhibit any or all of the following properties:
Toxic and Highly Odorous Components
       (TLV - Threshold Limit Value where odors are first recognized)
Hydrogen sulfide, TLV 10 ppb  
Mercaptans, TLV 4 ppb
Phenols, TLV 50 ppb
Cresols, TLV 50 ppb
Naphthenes, TLV Begins at 100 ppb

Toxic To Humans At Extremely Low Levels
Toxic To Biological Wastewater Treatment Plants (WWTP's)
Industrial WWTP's, dosed at 25 mg/L, before acclimation
Industrial WWTP's, 100 mg/L after acclimation
Municipal WWTP's, 1 mg/L before acclimation
Municipal & POTW: 10 mg/L after acclimation
EPA and RCRA Hazardous Waste
       (see Code Of Federal Regulations Title 40 Environment)
EPA Listed Waste  (D-List, F-List, etc) 
EPA 129 Priority Pollutants List
Combustible (some)

Few Are Recyclable (without additional processing)”


Now I know that this company is promoting their process to deal with spent caustic and, so, we wouldn’t expect them to undersell the difficulties but we see a different picture from that portrayed by Trafigura.


Where is truth in this matter?

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