Traveling Grate Slop Fired Boilers

1. Introduction

Distillery Effluent or Spent wash or Vinasse, is a foul odor effluent created by fermentation of sugar cane molasses to produce alcohol.  It is also commonly known as “SLOP”. It’s extremely high COD & BOD content (refer Table 1) and chemical properties makes it hazardous to environment. Its Disposal was a big challenge few years back till development of Slop fired Incineration boiler. Various methods of disposal were prevalent including conventional methods like bio-methanation and compositing have their own demerits of huge area requirement, land pollution, higher liquid discharge and disposal problem during rainy season.

Typical Spent wash Characteristics (Raw)


: pH 4 – 4.5


: 45000 – 60000 ppm


: 110000 – 135000 ppm


: 9 – 12% w/w


: Dark Brown

*BOD -Biological Oxygen Demand

*COD -Chemical Oxygen Demand

Table 1 Spent wash characteristics

Apart from High COD & BOD in Slop, other salts & alkalis present in Spent wash as shown in Table 2 make it a challenge to dispose even in Incineration technology.

ASH ANALYSIS % WT (As fired basis)


Silica, SiO2


Iron Oxide, Fe2O3


Calcium Oxide, CaO


Magnesium Oxide, MgO


Sulphate, SO3


Phosphate, P2O5


Potassium Oxide, K2O


Sodium Oxide, Na2O3


Chlorides, Cl


Table 2 Spent wash Ash Analysis

With evolution of Incineration technology, it proves to be best method to achieve ‘ZERO EFFLUENT DISCHARGE” in a distillery. It not only provides 100% disposal, but also provides steam for process and power generation to meet captive requirement. The other advantage includes saleable potash rich ash and reduction in cost of alcohol production.

Various technologies were tried earlier including Drying, Twin Furnaces, AFBC etc. each having some advantages and disadvantages. But ultimately Travelling Grate boilers prove to be most suitable as far as continuous operation, fuel flexibility and operating cost is concerned.

In Incineration process, Raw Spent wash is concentrated from initial concentration of 10 Brix to 60 Brix in Multi effect evaporators. Then this Spent was is fired in boiler as a fine spray with help of high-pressure pumps along with Bagasse or Coal or any other Biomass as supporting fuel. As most of the distilleries are part of sugar plants, boiler operators are more comfortable with operating Travelling Grate boilers.

Other Advantages of Slop Boilers

  • Cost Efficiency:Using Slop or Spent Wash as fuel in replacement of regular fuels not only reduces fuel bill but also helps in getting rid of hazardous effluent.
  • Energy Efficiency:Slop based boilers and power plant offer a balanced solution to generate and meet inhouse process steam and power requirements of distilleries.
  • Additional Revenue:Potash rich ash is saleable as fertilizer and source of additional revenue.
  • Reduced Cost of Production:It offers a great way to reduce ethanol production cost.
  • Zero Liquid Discharge (ZLD): Slop fired boilers is best solution to meet stringent pollution control norms and achieve Zero Liquid Discharge (ZLD) in a distillery.

Features of Mago Thermal Slop Fired Boilers

Mago Thermal has made lot of improvement in current design of Slop fired boilers available in Market. Some of them includes :

  • Incorporation of Water Air Preheater

    We have totally removed flue gas based Air Pre heater, still heating the air with hot water taken from economiser / FGC in specially designed Water Air Pre Heater. Although this increases size of economiser but overall improvement in life, operation and functioning of boiler.

  • Boiler suitable to fire 45 – 70 Brix Slop

    We have designed this boiler to fire Brix concentration as high as 70. This will help in sustained and better combustion.

  • Special coating of back end Pressure parts

    We are doing special coating on Tail end economiser coils for extended life. It not only improves corrosion and erosion resistance, It also provide resistance against accumulation of ash on metal surface.

Other Features are :

  • Proven designs Slop Fired Boiler with Travelling Grate technology.
  • Best solution to achieve Zero Liquid Discharge norms and to meet Steam & Power requirements of Distillery.
  • Our boilers are suitable to fire Concentrated slop ranging from 45 to 65 Brix thus able to sustain boiler operation even with varying Slop concentration.
  • Boiler design require minimum support fuel for continuous operation.
  • Option of firing variety of fuels such as Bagasse, Rice Husk, Coal, Wood Chips and other biomass as supporting fuel.
  • Designed to generate 100% steam on supporting fuel in case slop is not available.
  • Effective on-load cleaning of heat transfer sections to ensure continuous operation.
  • Option of ESP or Bag Filter to meet stringent emission standards.
  • Rugged design and Easy to operate technology with minimum maintenance & shutdown requirements.


Mago Thermal also offers :

    • Vetting of our design by renowned consultants in this field.
    • Standard warranty of 24 months on pressure parts and can also offer extended warranty including AMC.
    • As we are also into Operation and Maintenance (O & M) of Power plants and are in position to offer our services for this also.

For More Information: Call Us at +91-9910490700 or Contact Us