Chemical Sulphonation Plant Engineering Solutions | Industrial Detergent Plants

1,4-Dioxane is a by-product that has been associated with human health concerns, as it has been classified as a possible human carcinogen by the International Agency for Research on Cancer (IARC). It is hard to be distinguished from other substances, so it means that if consumers are accidentally exposed to it, they won’t even be aware of that. The way to get in touch with it is by inhalation, skin contact or ingestion.

The low levels of 1,4-dioxane observed in some raw materials and finished products demonstrate that with current technology, excessive levels of 1,4-dioxane are avoidable. Continued periodic monitoring of cosmetic ingredients and cosmetic finished products for the presence of 1,4-dioxane is necessary.

MARSINA ENGINEERING has developed in recent years a special unit aimed to the removal of 1,4-Dioxane from 70% SLES.  This unit has been set-up and tested in industrial scale and it can be installed in any new or existing sulphonation plant equipped with SLES production section, therefore allowing production of Low-Dioxane SLES for cosmetic use also in already existing plants.

Most recent chemical tests have carried out on De-Dioxanized SLES samples by internationally-accredited chemical laboratories, such as Polytechnic University of Milan (Italy) and Royal Scientific Society (Jordan).

The operation of the Double-Stage De-Dioxanization unit (1st and 2nd Stages in series) allows to achieve a reduction of Dioxane content in SLES of -96%.

By installing and running MARSINA Double-Stage De-Dioxanization unit, the production of SLES with residual Dioxane content less than 3 ppm is verified and guaranteed.

The unit is fully automatically managed by control system to earn safety, efficiency and flexibility:

The PLC (Programmable Logic Controller) continuously monitors the state of input devices and makes decisions to control the state of output devices, while the SCADA allows to monitor the system, to record events, to process real time data and interact with plant devices and machinery.

As a further enhancement to its De-Dioxanization unit, MARSINA has furtherly improved both process and plant unit by the following innovations:

Marsina has developed a proprietary technology for energy recovery from sulphur combustion to produce medium pressure steam.

The heat released by the combustion of sulphur is a valuable source of energy and its most efficient recovery strategy consists in using the heat from sulphur combustion for steam production. 

Being this energy available at high thermic level (temperature between 750°C and 430°C), the production of steam at medium pressure is feasible. 

This technology is based on the installation of a special heat exchanger, shell&tubes type, where hot gaseous stream Air+SO2 from sulphur furnace is cooled down, before conversion, by water (demineralized). 

The hot gaseous stream Air+SO2 crosses the heat exchanger tubes-side while demineralized water is fed shell-side. Hot gaseous stream enters the heat exchanger at temperature of about 750°C and is cooled releasing heat to the demineralized water down to a temperature of about 430°C, as required by the downstream SO2 to SO3 conversion process. 

The heat released by the hot gas stream makes demiwater evaporate so producing medium pressure steam.

Steam is produced at pressure up to 8 barg and rate up to 230 kg of steam/ton of LABSA.

Steam generated is immediately usable for main needs of the sulphonation process, such as sulphur melting (after pressure reduction), combustion air heating, etc.

Furthermore, possible produced steam exceeding the plant requirement is delivered at battery limit at lower pressure to be recovered for other applications, typically hot water production by direct condensation.

The energy recovery unit from sulphur combustion is designed to be easily integrated in any possible existing sulphonation plant. 

The unit is equipped with high reliability full instrumentation, redundant where necessary, in order to allow safe and continuously monitored operation. The unit is fully automatically managed by plant PLC, implementing control logics and safety interlocks both process side and steam production side.

Strong attention is paid by Marsina company in the design and supply of environment-friendly plants. 

Any effluent released by the sulphonation plant is opportunely treated with the most efficient technologies for removal of pollutants or hazardous substances before disposal or discharge.

• Exhaust gas treatment

The main gaseous effluent from sulphonation plant is the exhaust gas coming from the gas/liquid separation after sulphonation reaction. This gas still contains traces of unconverted SO2, unreacted SO3, and organic residues, and it undergoes two purification treatments in series before being discharged to atmosphere in compliance with the strictest environment protection regulations.  

1. The first treatment consists in the SO3 and organic residues removal through two different alternative technologies: through Marsina special exhaust gas filter (EGF), or by the electrostatic precipitator (ESP), a filtration device that removes almost totally the traces of not reacted SO3, organic and traces of dragged H2SO4 contained in the exhaust gas. 
2. The second treatment consists in the removal from the exhaust gas of the residual particles of SO2. They are absorbed by an alkaline solution, typically caustic soda solution, into a scrubbing tower and fixed in form of a mixture of sodium sulphite and sodium sulphate.

The treated gaseous stream leaving the scrubbing unit has SO2 residual content of maximum 5 ppm, so allowing its final discharge to the atmosphere.

• Liquid effluents

The only liquid effluent produced by the sulphonation plant is the sodium sulphite and sodium sulphate solution from the exhaust gas scrubbing unit. It is disposed as inert effluent.

A special use of this effluent is possible in case of presence of a spray drying plant in the same facility of the sulphonation plant.