Waste to Electricity

CDT-International With reCultuere Technology
Combine a Waste Treatment Plant with a Power Plant Use the Waste – don’t waste it!

Install a Waste Treatment Plant in combination with a Steam Power Plant and deliver Electricity instead without environmental pollution.
Stop the land-filling of waste and dismantle the waste hills in a secure and environmentally friendly manner.
The Problem
In most countries generally and in emerging countries especially there is a huge problem concerning waste treatment. The waste is usually left on rapidly increasing mountains of landfill. This creates a paradise for rats and a big health problem to surrounding inhabitants. The landfill mountains are heavily affecting the environment - not only locally but also world wide by emitting dangerous (greenhouse) gases like methane. In some places the landfill is also sliding out into the sea.
The Solution
A waste treatment plant from reCulture will solve the problem. The plant will receive the waste unsorted as it is, dissolve it into its elements separating them, and convert the biological fibres and plastics into fuel for a steam turbine providing electricity. The process is extremely clean with no air pollution and with less than 5% remnant for useful landfill or ballast in concrete or similar.
Beside the electricity production all the waste content is converted into recycling products (basic material).
Since the process is so clean, the plants can be situated in residential areas, where the waste is produced and where the electricity will be consumed. With no far away transportation of the waste nor for the electricity this solution is the most environmentally friendly waste treatment system.
Also already existing waste hills (landfill) may gradually feed the treatment plant in parallel with new waste. In this way the waste hill will be reduced and ultimately completely disposed of. The wastes of the waste hill will be excavated just as they are and transported to the (nearest) treatment plant. Thus there is no need for any pre-treatment of the wastes taken from the waste hill before being transported to the treatment plant.
Cooling Option
It is possible to utilise the residue heat from the production of electricity for production of a cooling media and thus benefit from the residue heat and avoid just wasting this resource. However, to benefit from this option there must be a need for district cooling and an infrastructure for the distribution of the cooling media.
Emission rights
In many countries reCulture’s waste treatment plant may take advantage of the carbon dioxide emission rights.
Comparing methods
There are three options for handling the Municipal Solid Waste (MSW):
  • Landfill of untreated waste – the oldest method
  • Burning – common in developed countries
  • reCulture – the modern way based on Swedish patent
Normally in conventional Waste to Energy plants, mass burn technology, municipal waste is directly fed to the boiler as a kind of fuel without any pre treatment. This untreated waste is of low CV (Calorific Value) and causes problems when used.
For Refused Derived Fuel technology (RDF) the MSW is treated before being fed to the boiler. The CV is higher than for the untreated waste but the sorting is not up to 100% successful. There are still inorganic content in the RDF i.e. sand, filler, metals, moisture and also PVC-plastics.
However, in the reCulture technology, there is a good quality sorting operation for removing inorganic content such as metals, fillers, glass, hazardous wastes, water and also PVC-plastics. Therefore the CV is higher than for the two previous waste fuels mentioned above. As the aggressive components of the waste, e.g. chlorine, are removed this fuel will cause very few combustion problems.
For the first two waste fuels there are restrictions to obtain a high steam parameter, which is critically required for a maximised power production in a CHP (Combined Heat and Power) plant. Deliberately the temperature is controlled to be low in order to avoid corrosion in the boiler as much as possible from aggressive chlorine and metals.
The reCulture technology on the other hand, gives a fuel with a high CV. As there are no harmful components in the fuel, the combustion therefore will face very few incineration problems.
Compared to the other methods, environmental benefits by reCulture are low air emissions (no CH4, no SO2 and no dioxin), low ash generation and minimum of landfill.
reCulture’s Waste Treatment Concept
The patented reCulture process, developed by reCulture., offers recovery of clean energy from domestic waste, yet does not require any changes in current waste collection methods. The mechanical and biological treatment (MBT) process is based on a technique used in the recovery of cellulose fibre from recycled paper.
Ordinary mixed waste is converted into bio fuel, while water salts and non- combustible materials are recovered in a closed-loop system. The concept is categorised as a “Clean Technology”. As a result, reCulture plants can be located in large, densely populated areas, further reducing transport costs and emissions.
The Basic Process
The technology used gives a process for the transition of the wastes into a bio-fuel as well as recovery of inorganic non-burnable materials. The inorganic part of the wastes, mainly inert material, metals and chlorine will be separated in the process while the organic portion will be manufactured into a high grade alternative fuel similar to conventional processed bio-fuel. The manufactured fuel consists to 85% of burnable bio-products and from an incineration point of view to 10% of environmentally friendly plastics. The fuel is very suitable for usage in a power plant.
The technology used in the reCulture’s treatment plant means that almost all of the waste quantity is recovered. Only a very small portion (<5%) has to be disposed of by landfill.
reCulture plant in combination with a CHP plant
It is advantageous to produce electricity and heat in a direct second step after the reCulture fuel production process by using a conventional CHP (Combined Heat and Power) plant. There the fuel will be burned in a steam boiler connected to a turbine generator producing electricity (see front page). Process steps reCulture plant The MSW (Municipal Solid Waste) is treated in various steps. The process resembles fibre recovery in the paper industry, which is a very old technology. Reception Reception is the first step of the process. Waste is shredded to be less than 300 mm. Big metallic objects, such as engine blocks and handle bars, are removed mechanically. After treatment, when reject has been sent away the remaining shredded waste is stored (in water), ready for the next step.
Dissolving
This is the core step of the reCulture process. The waste, coming here from the Reception, mainly consists of organic, fibre-based material (paper and food wastes). That is the reason for applying a technique from pulp and paper industry. The mix in the dissolver is low percentage waste and high percentage (more than 90%) water and the temperature is high but not boiling. The pH value is controlled. The temperature impedes a growth of the bacteria and facilitates the dissolving.
Gravity causes heavier (mainly inorganic) material to sink to the bottom of the dissolver where these waste materials are collected in certain areas and removed. Before being sent to the hydro-cyclones the water content is further increased.
The centrifugal force in the hydro-cyclones separates small particles such as clay and filler materials from paper, which have not been removed in previous stage. Plastic flakes are removed and treated separately and a portion of the plastics is added back later in the process.
Dewatering
Next step is dewatering, which is a two steps operation. In a first step a belt filter is used for the separation of solids from fluids and salts are flushed away with cleaned process water. Thereafter the waste is sent through a dewatering screw facility for further reduction of the water content. Water content is decreased to a level below 70% after passing the screw.
Drying
In order to safeguard the wished moisture level, the material is dried in hot steam. Thereafter the pelletizing takes places in order to get a fuel of certain dimensions and strength.
Steam gives also a side-effect namely to kill the bacteria. After drying the moisture content is 10-15% or any other rate due to customer wishes. The chosen level of moisture content makes the fuel storable without risks for self ignition.
Plastics are added in this process. Impacts from plastics: higher CV, as binding agent for the pellets, and as a layer on the outside of the pellets prevents from absorbing water.

Fuel as pellets

Process output: Dry fibre fuel

One ton of (Swedish) unsorted household waste contains energy equal up to 300 litres of diesel oil.
Three parallel systems
There are three systems in parallel, one for handling the residues and one for purifying water and one for cleaning of the air.
Reject handling
In this step inorganic material are separated into different fractions such as filler and metals. Any remaining organic material is returned to the main process.
Water purification
Water is treated in one coarse and one fine step. In the first step particles are removed from the process water. These solids form a slurry of organics, which is added back to the fuel manufacture. Treated water will be taken back to the process.
The next step is a facility for reversed osmosis where mainly salts will be separated. Treated water not used in the process will be disposed of.
Air purification
To make sure there are no emissions of mercury or other hazardous substances to the outdoor environment all air from the receiving and processing buildings are treated in an active coal filter.
The whole treatment plant is operated in a low under pressure.
Outputs from reCulture’s Waste Treatment Plant
Based on experience from Sweden one tonne of MSW gives 620 kg of fuel, 150 kg of filling material, 20 kg of metals, 8 kg of plastics and 197 kg of water. Though a high degree of separation there is still a small ash content (<5%).

Note: The above figures are based on Swedish waste content.

Physical composition of the fuel
The bulk of the components in the reCulture fuel are fibres of a few different categories. Among them cellulose fibres contribute 50% (mainly from paper and cardboard).
Vegetable fibres account for 20% and animal fibres give 15%. Plastic is separated and only a portion is added back to the fuel in the drying operation, plastic content is 11%. To avoid adhering chlorine, plastics with a density higher than 1.5 kg/m³ have been separated early in the process.
SUMMARY
  • The fuel is stable and can be stored for a very long time.
  • The fuel has been processed for reducing or removing hazardous content.
  • The different fragments from the process are sorted out in fractions which can be reused, destroyed or treated for new purposes.
  • All affects on the environment are well below normal limits, and since the plant is a closed system, it can be built close to or inside a community.
  • The fuel has water content at such a low level that it gives god efficiency in burning. This is a key for producing electricity with good profit.
  • The process produces between 200 and 400 litres of surplus water per received ton of waste. The amount varies with waste composition.
  • The plant and its components are based on well known techniques and components. A major part of the components are standard and can be bought from stock. A factor that significantly reduces the technical risk.