Brief description of the process of flameless gasification of municipal waste generated in the complex equipment

Flameless Gasification complex configuration

    The complex for Flameless Gasification of generated municipal waste includes the following basic blocks:
  • Unit for selection of the incoming materials -
    for sorting of the input material (selection of scraps of metal, glass, stones and sand, food waste and biomass)
  • Flameless Gasification unit -
    production of synthesis gas and coke
  • Biogas unit -
    for the processing of food waste and biomass

Additionally, as an option, from the received synthesis gas, on customer's request, the application of installations for the production of energy resources and various chemical products, as well as freezers or greenhouses, can find its use. The application in the complex of the latter (greenhouses, as an option) is due to a possibility to utilize through that the received during the process coke, as well as to use an opportunity to utilize the produced excess heat and electricity.

Block I:

Unit for selection of Generated municipal waste

The selection unit is used for sorting and grinding of generated municipal waste with the view to prepare the input material for Flameless Gasification modules, for extracting the food waste and biomass for the biogas module and power equipment, as well as the selection of secondary raw materials, such as ferrous and nonferrous metals and glass, for subsequent realization on the side. In parallel, the screening of inert materials (sand, stones and debris) is taking place.

Block II:

Biogas and energy equipment unit

The sorted portion of the raw material, in the form of food waste and biomass, has its own specifics, therefore it requires additional facility for preliminary preparation (crushing, separation of inorganic impurities and pasteurization) for processing.

Accumulation of such prepared raw material is intended for 1-2 days and occurs in the receiving tank. From the receiving tank the food waste is transported into the reactor, where it remains from 8 to 10 days. There are created specific temperature conditions, from + 25 ° C to + 28 ° C, with the humidity and pH control in compliance with the process technology. From the reactor the feed material is dosed and fed into biological block for preserving the bacterial balance in the biological substrate. The exhaust biological substrate is loaded and unloaded automatically. After unloading the biological substrate is separated into solid and liquid biological fertilizers. The resulting biogas is collected in the external gasholders and is used to generate the electrical and thermal energy for the needs of the complex. Disposal of biogas is realized through the pipeline, which is equipped with automatic condensate drain and pressure safety devices that protect the gasholders from excessive pressure. From the gasholder biogas is fed continuously to the gas piston plant to generate electricity and heat. The operation control over the entire biogas and energy equipment unit is carried out upon commands from a central program module.

Block III:

Flameless Gasification of prepared waste (thermolysis)

The manufacturing process of recycling of generated municipal waste by thermolysis technology looks according to the scheme as follows.

The incoming for processing, prepared and sorted municipal solid waste (excluding food waste, biomass and the inert materials) are stored. From the store, by certain parts, the feedstock is fed into the hopper receiver, then proceeds further to the screws, where it undergoes drying – the process, in which the raw material is heated to the appropriate temperature by the heat coming from the reactors, getting rid eventually of unwanted moisture, still existed in the incoming raw materials. Through the screw washes, the dried raw material is delivered into the multistage Thermolysis reactor for flameless gasification at a temperature of 400 - 950°C. Each Thermolysis reactor consists of two low-temperature carbonization chambers, outer Thermolysis casing, inlet and outlet chambers and burners. As a result of low-temperature carbonization reaction, the synthesis gas is derived and then driven further into the gas enrichment section, where gas cleaning treatment (from impurities and minor-products) is taking place. Carbonization at a low temperature and fumigation of the input material takes place in both low-temperature carbonization chambers at different temperatures. Heating, required for the coking process, is carried out with the help of heaters in outer Thermolysis casing chambers.

Monitoring and control of the reactors’ functioning and the guarantee of their safe operation are realized through a number of measuring probes and safety system, organized into a single dispatcher system. The gas-transmission system is protected from overpressures by a due number of measurement and control membranes. In case of internal pressure increase or other emergency situation, the formed gas is drawn off to the torch. In addition, there is a water and steam system for urgent interruption of the low-temperature carbonization reaction.

There is a cascade of two sequential screw aggregates connected to the reactor. The further thermal decomposition of waste is taking place there, along with the primary coke material and liberation of synthesis gas. As well as the Thermolysis reactor, the coking units are equipped with heating casing used for direct heating. The received solid residue (coke and ash) after appropriate cooling (by steam and water) is transferred to the sealed containers. After cooling, the ash and mineral particles are separated and utilized. In the gas enrichment section the synthesis gas comes through the system of scrubbers, separators, reservoirs and pumps. Each reactor is connected to the scrubber – the absorption gas treatment unit. The gas streams from both lines are joined and routed through the absorption purification cascades, where during circulation the condensate is absorbed from coking gas and the gas is cooled down. At thermolysis technology the organic substances are parted into short-chain hydrocarbons; the ferric oxides, as well as oxides of other inorganic substances are reduced (e.g. oxides of sulfur compounds). During the synthesis gas treatment, a complete condensation of aliphatic and aromatic substances is achieved. The content of detrimental impurities (e.g. HCL) is reduced by limewater neutralization.

With the help of oil separators the oily actuation medium and water are separated. The wastewater additionally purified by active carbon and by biological treatment of the Thermolysis installation. After that the wastewaters can be directed into the sewage system of the industrial zone. The exhaust air from Thermolysis process is purified in biological purification system. To eliminate the smell emissions, associated with exhaust gases from wastewater purification and multi-stage waste drying process, they are drawn away from the working areas through the piping system with integrated biological gaskets.

After all cleaning treatments the process gas flow gets into the gas storage. This gas storage is used to receive and buffer the synthesis gas obtained during Thermolysis process, to ensure the power supply, to feed the reactor torches and coking units, as well as to deliver gas to the consumer through the compressor station. Through back-mixing of worked-out gas its quality in reactor lines is balanced. The resulting synthesis gas is, at the request of the customer and with the help of additional equipment (option), can be used for generation of energy or for production of various chemical products.

Protection system consists of a torch, which serves, in case of emergency, as a reliable withdrawal of synthesis gas from coking installation and gas storage. The connecting pipes are equipped with armature, which, in case of power disconnection, autonomously opens. To prevent accidental pressure lifting, the reactors and torch joints are equipped with safety membranes.

To feed the installations the wastewater is re-transferred from the water treatment systems and used. Through the air tap the exhaust air is discharged into the atmosphere. The organic residues are cyclically withdrawn and charged into Thermolysis process. The water circulation system for process gas purification contains the cooling installations, connected to the heat carrier that runs using the ambient air.

Schemes of the process of Flameless Gasification of waste

Sorting station is meant for pre-processing of municipal waste with the purpose to extract the food waste and biomass, metal, glass, stone, ceramics, sand and household debris. Use the menu on the right to find out more  
The generated municipal waste is temporarily stored on site in front of the sorting station.
One of the loader-manipulators loads separately large-size items (sofas, cupboards, TV sets, monitors etc.). Another one provides a continuing loading of municipal waste into the storage-hopper for further delivery into the sorting station.
The lifting conveyor transports the waste from the hopper to the conveyor-distributor, from where the prepared waste gets to the vibrating screen for sifting of fine materials (sand, stones, ceramics and small household construction waste).
From the vibrating screen the material is getting on the sorting conveyor, in a closed cabin of the sorting station, for selection of food waste and biomass, glass and the metal residue after capturing prior to sorting.
The sorted on a conveyor secondary materials, such as glass and metal residue, food waste and biomass, are dropped from the workplaces in the mines to clear the material.
Following the preliminary waste screening, made by hand in a closed cabin, the input raw material goes through a double row of magnets to capture the remaining scrap.
The selected secondary materials (ferrous and nonferrous metals) are subject to pressing and packing.
After the selection and separation of scrap, the input material is conveyed to the shredder for grinding, to the parameters acceptable for the thermolysis reactors.
The prepared and sorted municipal waste is stored on a designed for this purpose industrial concrete ground for the following feeding into the thermolysis installation.
To continue, go to the next tab    
Having passed the stage of sorting and grinding to the required parameters, the input material comes from the industrial site to the thermolysis installation for production of synthesis gas.
Sorted and prepared waste from the on-site storage are formed into the loading parts and conveyed into the thermolysis installation.
In the attached to thermolysis reactor separation unit, the received synthesis gas is refined from fine mineral particles and dust.
Monitoring and control of the reactors’ functioning and guarantee of their safe operation are realized through a number of measuring probes and safety system, organized into a single dispatcher system.
To continue, go to the next tab    
In the gas enrichment section, the synthesis gas comes through the system of scrubbers, separators, reservoirs and pumps. Each reactor is connected to the scrubber - absorption gas treatment unit.
The initial reduction of harmful impurities (e.g. HCL) is taking place in the second stage of gas treatment, by neutralizing with the limewater according to the prescribed requirements
In the third stage of cleaning of synthesis gas from harmful impurities.
The complete condensation of aliphatic and aromatic substances is achieved in the fourth stage of gas cleaning. In a bound state with actuation medium the harmful substances and light particles are withdrawn during the final circulation cycle.   To continue, go to the next tab    
With the help of oil separators, the oily actuation medium and water are separated.
The wastewater additionally purified by active carbon and by biological treatment of the Thermolysis installation. After that the wastewaters can be directed into the sewage system of the industrial zone.
To eliminate the smell emissions, associated with exhaust gases from wastewater purification and multi-stage waste drying process, they are drawn away from the working areas through the piping system with integrated biological gaskets.

Table 1

Comparative figures of various technologies for disposal and processing of generated municipal waste

# Indicators Units Technology
Thermal processing Plasma Flameless
gasification (thermolysis)
Composting
(biological gasification)
*
Combustion
**
Pyrolysis
1 Specific capital investments Euro/1t of solid waste per annum 390-690 355-455 455-545 330-400 180 - 210
2 Specific
operational costs
Euro/1t of waste 34-45 30-35 45-57 45-55 27-32
3 Specific environmental payments Euro/1t of waste 2 2 1 no 2
4 Specific Company revenues Euro/1t of waste 20 17 5 90-200 5
5 Specific energy consumption KW/1t of waste 50 - 70 50 - 70 500 65 90-120
6 Specific footprint m2/1t of waste per annum 0,1-0,2 0,15-0,30 0,1-0,2 0,1 0,4-0,6
Environmental aspects
7 Availability of production waste % By weight of solid waste 23 - 28 (ash and slag) 25 -30 (coke residue) The fine dust, fumes, heavy metals sand and stones after screening, no ashes and slag 20 - 25 (non-compostable fraction)
8 Soil pollution   presence of a slag refuse coke residue only practically no no practically no
9 Contamination of groundwater   no no no no no
10 Air pollution   within the limits within the limits heavy metals no within the limits
Received products after processing
11 The energy produced by steam *** MW/1t of waste 160 120 no no no
12 Electric power mw/1t of waste 0,40 0,30 0,50 1,5-2,5 no
13 Compost % from mass of waste no no no no 50
14 Black metal -«- 2 2 3 3 3
15 Nonferrous metal -«- - 0,3-0,4 - 0,3-0,4 0,3 -0,4
16 Other recyclables -«- - 5 -10 15 - 20 cullet 3-6 5- 10

* Combustion technology is considered by the example of the use of firing installations with grate.
** Pyrolysis technology is shown as a pyrolytic reactor system, operating at an average temperature of 850 °C.
*** The produced steam is used for production of electricity (own and external use), technological needs and the needs of own plant (heating, ventilation, hot-water supply).

Table 2

Comparison of the technologies by the example of the operating waste incineration plant in Baku (Azerbaijan), plant design in Buryatia (Russia), and a plant design for Flameless Gasification of waste.

Index Units * Generation IV incinerator in Baku (Azerbaijan). Built by the French company "CNIM S.A." The implementation project of the complex flameless gasification THERMOTEC POWER in the Russian Federation Project Mitsubishi Heavy Industries Ltd factory in Buryatia (Russia)
Power waste per annum Tons 500 000 240 000 240 000
Electricity generation MW/h 28 25 10,2
Usage of natural gas in the production process Yes/No Yes No Yes
Remains for burial Yes/No Yes No Yes
Number of new jobs created People 100 100 100
Approximate footprint hectares 20 4,5 7,0
Size of total investment Million euro 345 85 125 **

*   Link to publication on the Internet (source of these data): http://vesti.az/news/119327
** Taking into account the 30% subsidy from the Japanese party, the cost for the Russian party will make about 90 million euro.

Comparison of combustion with the Flameless Gasification technology,
when applied to municipal and industrial waste as feedstock, without doubt indicates the benefit of gasification.