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Technologies for CP Projects
Small Power Engineering


 

Mini heat power stations based on alternative sorts of fuel with application of filtration method of combustion in superadiabatic regimes.

North-Western International Center of Cleaner Production offers realization of the projects in civil-engineering, the building of mini power stations on the basis of conversion technology in thermal processing of various combustible wastes (e.g. hospital wastes, unsorted municipal solid wastes, pulp-and-paper industrial wastes, ash dumps from cogeneration and metallurgy plants, silt sediments after cleanout of rivers, etc.). This technology guarantees a high efficiently, environmentally appropriate utilization of solid wastes with low containing of carbon (from 10%) and high humidity (up to 60%).

The production of universal equipment is adjusted on the basis of enumerated technology to provide thermal processing of solid combustible materials and to produce thermal and electric energy with high efficiency (up to 95%). In addition, small material inputs ensure environmentally appropriate processing of wastes. Besides the utilization of wastes and low-calorie fuel, the technology in operation allows to extract secondary products from wastes and to recycle them. For instance, during utilization of oil-slimes and oil wastes, up to 50% of processing material returns back as a ready oil product.

During processing of worn tire covers and other rubber wastes, it is possible to extract metal cords, powder of zinc oxide, pyrolized oil and fuel gas. During utilization of worn tire covers, the new secondary materials (e.g. isoprene rubber, tar and aligomers) constitute up to 40-50% of initial weight. The generating fuel gas can be applied for production of heat and electric energy.

During utilization of shale wastes, it can be produced a tar, as well as liquid components fit the content of gasoline A-66 (in the volume of 40-50% from initial weight of raw material).

The new technology opens up possibilities in usage of low-grade coal including brown coal, as an alternative sort of the fuel in environmental friendly power engineering. It will allow making assessment of available raw material and fuel resources, wastes and dumps, which are accumulated for a long period of traditional mining operations. This technology also allows starting modernization of technically absolete coal boiler rooms.

The method is based on a new physical phenomenon, filtration combustion in superadiabatic mode, where combustion temperature in the reaction zone substantially exceeds the adiabatic temperature of combustion. The rise of temperature in reaction zone carries resonant character.

Intentional use of superadiabatic regimes provides possibilities in efficient processing of various combustible wastes by means of gasification with high-energy efficiency, environmental friendliness, and a relatively low processing cost:

  • Environmentally appropriate utilization of different sorts of combustible wastes;

  • Creating of environmental friendly mini power stations (development of small power engineering) on alternative sorts of fuel;

  • Modernization of existing environmental faulty coal boiler rooms.

The technologies of thermal processing are arranged in two stages that are schematically presented in Fig. 1. In the first stage, the processed material is gasified in a superadiabatic combustion regime with air and steam. The combustible gas product comprises hydrogen H2, carbon monoxide CO, in some cases- hydrocarbons or other organic compounds are burnt in the second stage in conventional utilities (e.g., steam or water boilers) with generation of heat and electricity.

Gasification of solid wastes is realized in gasifier-reactor of the shaft type. The regime of superadiabatic combustion is realizing in so-called density layer. The specific characteristic of the given combustion process - the evolved heat, which is not leaving the reactor (solid and gaseous products are leaving reactor with relatively low temperature, less than 150 . The main heat with temperature 1000 - 1200 is concentrated in the middle part of gasifier and is consumed for producing of energetic gas-product (hydrogen from H2O and partially carbon monoxide from carbon containing substances).

Processing combustible waste with generation of electricity

The raw material is charged into the reactor from above through a lock hopper. The air and steam are fed from the reactor bottom. The product gas runs out from the upper part of the reactor and the ash residue is discharged at the bottom. The processing mixture within the reactor descends under its own weight.

Certain typical zones are located along the height of the reactor. In the uppermost layer the temperature is maintained within 100-200 C. Herein the raw material is dried with the filtrating product gas. As a result, the product gas is enriched in water vapor.

Below, there is a zone where pyrolysis and coking of organics in oxygen-lean environment occur. In this zone, the product gas is enriched in volatile pyrolysis products.

In the middle part of the reactor is the gasification zone where coked organics at 1000-1200 C react with oxygen, water vapor, and carbon dioxide to yield CO and H2. A fraction of coke is oxidized to CO2; due to this, a high temperature is maintained within the gasification zone.

Still lower is the zone where the solid residue consisting mainly of inorganic substances is gradually cooled in the flow of oxygen-rich gasifying agent. Herein, the remaining organics and carbon are consumed and the processed material is reduced to ash. In the lowermost part of the reactor, the solid residue is cooled to approximately 100 C.

This arrangement of thermal processing secures the following advantages over direct combustion:

  • Gasification has high thermal efficiency (up to 95%); this provides a possibility of processing materials with a small content of combustibles (ash content up to 90% or high moisture content up to 60%, the optimal moisture content is 20-30%);

  • Low gas flows velocity within the reactor and filtration through a layer of raw material secures small entrainment of dust particles in the product gas; this provides a possibility of dramatically reducing investments in gas-cleansing and energy-generating equipment;

  • In certain cases, when cleansing of sulfur, chlorine, fluorine, and mercury is necessary, it is much easier to cleanse product gas rather than flue gas because the product gas has the lower temperature, smaller volume, and higher concentrations of pollutants; additionally, it contains sulfur in reduced forms (H2S, COS), which are easier to absorb than SO2;

  • Upon gasification, nitrogen-containing organic compounds are partially decomposed in oxygen-lean environment to give smaller concentration of nitrogen oxides in the flue gas;

  • Gas combustion in modern burners is the most clean method of combustion; owing to complete combustion the flue gas contains the excessively low amount of carbon monoxide and residual hydrocarbons;

  • The two-stage incineration secures dramatic reduction in formation of dioxins (polychlorinated dibenzodioxins and dibenzofurans) because, even in the presence of chlorine, formation of aromatics (precursors of dioxins) in the flue gas is suppressed and concentration of dust particles (catalysts of dioxin formation) is maintained low;

  • The ash discharged from the reactor is relatively cool and is essentially free of unburned carbon;

  • Processing of certain wastes provides a possibility of recovering materials of commercial value (e.g., pyrolysis oils) from the product gas;

  • The choice of energy-generating facilities is not restricted to water or steam boilers; gas turbines or diesel generators can also be used; the processing scheme can be accommodated to an existing energy-generating facility with the product gas substituting for a fraction of a quality fuel.

 

Russian specialists on the basis of gasification method of condensed fuels in the regime of superadiabatic combustion have developed a number of technologies including:

  • Gasification of substandard coals and coal wastes with generation of fuel gas;

  • Processing of worn-out tires and rubber waste with recovery of metal cords, zinc oxide powder, pyrolysis oils, and fuel gas;

  • Processing of waste materials of wood and pulp industry (including lignin) with recovery of fuel gas and pyrolysis tars;

  • Incineration of waste oils and oil slurries;

  • Incineration of municipal solid waste;

  • Incineration of sewage sludge;

  • Decontamination of a number of industrial wastes, including paints and lacquers, oiled sawdust and rugs, chemical wastes;

  • Environmentally benign on-site incineration of the hospital waste;

  • Incineration of biomass to produce energy.

 

The enumerated processes have been developed on pilot units.
The methods have been patented in Russia and abroad.

 

The processes can be realized in continuous or batch plants (the latter, at a low throughput). Presently, several plants were developed:

  • A batch installation for incineration of metallurgic waste oil with the throughput of 120 kg per hour (by combustibles). The installation consumes 300-400 m3 of air and up to 100 kg of steam per hour; the reactor is 1 m in diameter and 3 m high (Fig. 2).

  • A plant for gasification of municipal solid waste (MSW) with a continuously operating gasifier-reactor and the throughput capacity of 2 t/hour (Fig. 3). The plant consumes ~1800m3 of air and up to 700 kg of steam per hr; the power produced in the after-combustion stage is 5 MW; the reactor is 1.5 m in diameter and 7.3 m high. The heat generated at MSW incineration is used for district heating and hot water supply.

  • The performance of the plant during experimental tests confirmed environmental friendliness of the process; thus, the concentration of dioxins in the flue gas, even with no gas cleansing, was within 2*10-10 g/m3 (in accordance with European normative from 17 BlmSch 17.12.1990 the concentration of dioxins in flue gas should be no more than 1*10-7 g/m3).

Installing several module reactors of this size can increase the throughput capacity of the waste-incinerating plant.

 

Performance characteristics of the gasifier-reactor.

Characteristics Unit of measurement Value
1. Technological efficiency t/hour (t/year) -2,14 (15 000 )
2. Energetic efficiency by redistribution fuel / gas-product. % 90 and more
3. Heat capacity of burners (in the case of the lowest caloricity of MSW= 11200 MJ) MW 6

4.
Annual production of heat GKcal 36 160

5.
Operational life (under due maintenance works) years 15 and more

6.
Hours of reactor's continuos work hours/year 7000

7.
Height from the level of bottom m 14
8. Bottom load in the case of charged reactor t/reactor Less than 60
9.

Characteristics of gasifier reactor:

Internal diameter

External diameter
Height of working volume

 

m

m

m

 

1,5

2,6

7,3

10. Occupied area (without a site for reception of wastes):
One reactor-module (8*35) m

 

m2

 

280


11.
Temperature of gas-product Less than 150
12. Temperature of ash Less than 100

13.
Maximum size of raw material's pieces mm 200
14.

Operational expenditures:

Staff (4 turns, each 2 workers);
Service activities. Corrective maintenance.
Electric energy
Consumed materials for gasification
Natural gas (pilot burner EEU limits)
Industrial water (or steam exhaust )
Chamotte

 

employees 

% from capital costs

KWh

 

m3/hour

t/hour (without energetic block)

t/year

 

8

2-4

50

 

5

Up to 1

Up to 3

 

Presently, a number of reactors with other dimensions is under development. The rest of equipment used including power-generating and gas-cleansing units is commercially available. In certain cases this equipment should be accommodated to the task. Besides, together with a specialized designing bureau and plant-producer a start has been made on development of a gas-turbine operating on the product gas combined with the gasifier-reactor.

 

Depending on the required power the general scheme of the waste incinerating plant includes from 2-3 to 10 gasifiers, a necessary power equipment defined by a customer (water or steam boilers, steam turbines with electrical generators, etc.), and a system for flue gas cleansing, the necessity in which is determined by the composition of a raw mixture (content of sulfur, chlorine, fluorine and others). The amount of toxic substances in the flue gas is guaranteed to meet (or even be lower) the European standards. If the customer sets up more severe requirements to the outbursts, they can be reached and must be outlined in a special request. Different auxiliary equipment can be also included.

Along with this, a principle of modules, used in the project secures a flexible structure of the process realization. For instance, if the customer has the necessary power equipment (operating station, boiler works and so on, with the developed infrastructure) only gasifier-reactors are used. The produced gas-product can be burnt up in existing boilers substituting partially or fully for the natural gas, black oil or solid fuel. In this case the capital investments can be more than half decreased.

The technological line designed for the MSW incineration can be also used for processing different types of waste. In this case some additional external appliances and variation of the technical regulation can be demanded.

 

Comparable price characteristics of incineration plant:

The typical incineration plant of European production costs more than 1000 USD in recalculation on one ton of installed capacity per year; the incineration plant, which is based on enumerated above technology will cost 200-300 USD in recalculation of one ton of installed capacity per year. In addition, it should be noted that all essential European limits of maximum permissible emissions of dioxins and other pollutants would be fulfilled.

Delivery, as well as the assembling and adjustment of the equipment is performed within the year since the contract has been signed and the given area had been prepared. The "North-Western International Cleaner production and Environmental Management Center" (St. Petersburg), which is supported by the State Duma Committee of Ecology and Specialized Agencies of UNO (UNIDO/UNDP), realizes project maintenance, preproject and project works.

The development contractors and plants-producers perform delivery, assembling and adjustment of the equipment, putting the plant into service, personnel training and control over the project.

 

MSW processing plantwith a continuously operating reactor (Lappeenranta, Finland).

 

 

 

 

 

 

 

 

 

 

 

 

 

In the developed process, a high ecological friendliness is provided; the solid residue of combustion can be safely disposed; as an option, ash vitrification can be provided to exclude possible leaching of heavy metals.

Presently, three plants (two of them in Moscow and the third one in Finland) can produce such units for processing of solid combustible wastes (materials).

Offered technology has a great interest abroad, especially in Europe, U.S.A. and Japan. The request to build such incinerator with application of gasifier-reactor came from Ireland, to combust the local fuel-peat. There is a great activity to apply superadiabatic methods in Japan, to upgrade more than 500 incinerators. All of them were built with application of old technologies, which caused the presence of high content of dioxins in organisms of local people.

Austria is interested in purchasing of such units and building of incinerators both in Austria and in Southern Germany.

This method was awarded by the Grand-Prize of International Exhibition of Industrial Property Archimed-2000.

 

Example of the brief commercial offer

Object:
Thermal power station, which supplies secondary renewable fuels to ensure 50 thousand citizens by electric power.

Advantages:

The most important advantage of offered project of building thermal power station with gasifier-reactor is the social effect of environmentally appropriate and cheaper utilization (processing) of wastes in money terms.

The effect expresses in compensation of land costs, presently operated as landfills, savings on land revegetation costs and costs for treating of unofficial disposal tips.

At the same time, there is a great opportunity to solve the problem in development of small power engineering on the basis of local untraditional renewable sources of fuel.Thermal power stations based on such principle are economically effective (self-supporting).

Characteristics of Object.

1. Thermal power station includes:

  • Two specialized complexes of "gasifier-steam boiler", each of them consists of two or three gasifiers, with gasification of low-grade fuel MSW on steam-air blast;
    - Steam boiler, which is operating on poor gas as a fuel; the steam output of the boiler is 32 tons per hour; steam parameters: = 40 kilogram-force/sm2, steam temperature t = 440 C;

  • Delivering of "gasifier-steam boiler" complex can be realized by Russian or by foreign producers following specification of requirements and engineering, developed by existing companies.


2. Fuel: municipal solid wastes. Further, during implementation of such complex, there is opportunity to use solid industrial wastes, worn tire covers, pulp-and-paper industrial wastes as an alternative fuel.
3. Steam turbines with turbogenerators: four block steam-turbine units P 1,5 40 - /8a with nominal capacity 1500 kilowatt each (4 1500 = 6000 kilowatt) and production extraction of steam or the gasifiers needs, with backup systems.
4. System of purification and flue gases withdrawal.
5. Automated control system of engineering processes.
6. Buildings and structures with all necessary operational systems of thermal power station and deliverability of electrical power.

Main indicators and characteristics of Object:

1. Installed electric capacity (IC) 6 MW

2. Quantity of hours of IC usage 8 000 hours/year

3. Fuel: municipal solid wastes, including agriculture and food production.

4. Annual consumption of fuel 75 000 tons/year

5. Estimated building cost (max.) 12,5 13,8 millions of US$

6. Recoupment of capital investment (max.) 6,7 years

Construction period

The building realizes on the terms of "turnkey" for the period of 24 months from the moment of the signing of contract.

 

For any futher information or implementation possibilities, we are always at your disposal.
Please contact us: admin@nwicpc.ru

 

 

 

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Last updated: 23.08.2006
©2002 North Western International Cleaner Production Centre