The most various sludges can be dried in BINDER drying plants, depending on requirements even down to a residual humidity of 1 %.
Depending on the type of energy available, Binder offers low-temperature and medium-temperature plants for sewage sludge drying processes.

The convective belt drying of sewage sludges offers the following advantages:

• Weight reduction of more than 70%
• Reduction of disposal costs
• Disinfection of the sludge
• Utilisation of waste heat

Process description

Sewage sludge pre-dehydrated by means of a centrifuge to a solids share of 25 – 30 %  is dosed to an extruder especially developed by Binder for sewage sludge. The solidified product strands create a product pile on the conveyor belt of the dryer that is capable of being aerated.
The belt is conveyed through a drying chamber consisting of several zones. Pre-heated fresh air is continuously introduced. In the case of medium-temperature drying, the circulating air is intermediately heated and directed through the product several times until a partial air flow with a high water load leaves the drying plant. This waste air can now be passed on for treatment.

Almost all process-related parameters are infinitely adjustable. It is therefore possible to adjust the optimal operating point depending on the respective application. Due to a fully automatic control system, operation is possible without supervision.

Utilisation of waste heat

In many sewage plants, gas motors are operated to generate electricity, due to the availability of bio-gas. Energy in the form of cooling water and exhaust gas is generated as a waste product.
The Binder medium-temperature drying process is suitable here. This offers the following advantages compared to a so-called low-temperature dryer, which dries at low temperatures only:

• 3 to 5 times smaller drying areas, hence lower investment costs
• no dependence of the drying performance on climatic conditions (summer/winter or day/night)
• Capacity independent of available waste heat amounts
• Substantially lower supply and exhaust air quantity due to the higher air saturation, resulting in a low heat energy requirement
• cost-efficient waste air cleaning
• low electricity consumption due to smaller amounts of fresh and waste air 
• easier control effort
  

Expenditure

Medium-temperature drying leads to substantially reduced investment costs despite a possible required additional heater. The costs for ground, building and waster air treatment are also substantially reduced.