Waste Process Flow Schematic
The Biosphere Gasification System
The Biosphere Gasification System is a state of the art waste processing and gasification system which processes Municipal Solid Waste (”MSW”) to produce energy in Five Stages.
Stage One:
Municipal Solid Waste is collected by the client and delivered to the facility or to local processing and transfer stations.
Stage Two:
Recyclables are removed and the remainder of the MSW is shredded.
Stage Three:
All the residual MSW is forced through a Densifier which compacts the MSW into 20g WDF pellets with 15-20% moisture.
Stage Four:
In stage four the pellets are fed into the Gasifier which transforms the residual MSW into a synthetic gas (syngas), other chemical products and inert ash.
Stage Five:
In stage five of the process the syngas is used to produce steam, powering a steam turbine for Micro Power Generation.
Basic Process example
Gasification System – Stage 1
Collection and Delivery
MSW is collected and delivered to the Biosphere facility using the existing collection system. The facility would usually be sited at one or more existing landfill sites so there need be no change to the existing method and schedule of collection and delivery to site. However, the collection system can be simplified as multiple collection of recyclable and non-recyclable material can be replaced with a centralised separation unit at the Biosphere System facility.
The processing of the MSW in stage 3 will reduce the volume by approximately 70% so, subject to local conditions, it may be advantageous to deliver MSW to several small waste processing and transfer plants for Pelletization prior to transfer to the Biosphere itself. This can substantially reduce traffic movements. Each locality would be analysed to identify the best logistical structure.
Refuse trucks arriving at the facility first pass over a weigh bridge so that waste input is measured and monitored. This also allows waste streams to be carefully controlled and, if necessary, separated. For example, some forms of hazardous waste are processed separately.
The incoming waste is then deposited on the tipping floor. No laborious sorting or handling is needed. The only separation that is required will be the removal of large oversized pieces that will not fit into the shredder, heavy metal items, such as engines, that may slow down the shredder or items that need special pre-processing, such as refrigerators, freezers and AC units from which the Freon must be removed. Hazardous waste and medical waste are handled separately and not co-mingled with normal waste.
Part of the waste received during delivery hours is stored for processing at night and on weekends and holidays. Any oversized material is shredded and then conveyed to storage.
The waste is completely cycled every day. Should unscheduled shutdowns occur, the waste received from the municipality goes into the storage area which is designed to handle normal surges and continue accepting the waste.
Gasification System – Stage 2
Shredding and Separation
MSW received at the facility is first processed by a mechanical Separator for shredding and separation.
The Separator uses a number of techniques including magnets, sieves and air blades to separate the MSA into the following components:
» Organic matter for compost production (about 20%)
» Plastics/ rubber (about 10%)
» Metals, glass and aggregate (about 3%, 5% and 8% respectively)
» Residual MSW (about 54%)
This separation enables the re-cycling of all appropriate materials.
Each separator works at a rate of 5 to 8 tons per hour.
Recyclable material is packaged and sent for re-cycling
The non-recyclable remainder is sent on for processing in stage 3
Full Automation
Gasification System – Stage 3
Pelletization
» The shredded MSW is transferred into the Densifier.
» This removes much of the inherent moisture and compacts the MSW into 20g WDF pellets, the optimum size for gasification.
» The pellets or WDF (waste derived fuel) are about 1/3 the volume of the input material and odourless.
» This reduction in volume and elimination of odour make local processing a practical option which can lead to dramatic reductions in traffic volumes.
Gasification System – Stage 4
Gasification
The WDF pellets are then transferred to the Gasifier itself. This is a three stage gasifier, designed to deliver combustion gas, without separation via a venturi to a steam boiler/turbine combination. The Gasifier supplied by GEEC, EWS’s preferred supplier, differs from traditional gasifiers in that the system does not separate or purify syngas. Rather, it makes a direct heat transfer which significantly enhances the efficiency of the system compared to other technologies.
Gasification typically operates in an oxygen starved environment at 20-70 bars of pressure (290.075–1015.26 psi). The gasification process converts any carbon containing material into a synthesis gas composed primarily of carbon monoxide and hydrogen, which can be used as a fuel to generate electricity or steam or used as a basic chemical building block for a large number of uses in the petrochemical and refining industries. Gasification adds value to low-or negative-value feed stocks by converting them to marketable fuels and products. The high temperature in the gasifier converts the inorganic materials in the feedstock (such as ash and metals) into a vitrified material resembling coarse sand. With some feed stocks, valuable metals are concentrated and recovered for reuse. The vitrified material, generally referred to as slag, is inert and has a variety of uses in the construction and building industries.
The Gasification System incorporates remote monitoring information systems routed to a support database on a real time basis. The systems are reviewed and maintained on a regular basis.
Gasification System – Stage 5
Energy Production
Thermal Transformation:
» The waste is injected into the Biosphere chamber or thermal transformer, and piles up in the body of the reactor. The waste creates a sustained temperature of up to 2100 ºC.
» The organic material does not burn because there is not enough oxygen but instead is transformed into a gas composed primarily of carbon monoxide (CO), hydrogen (H2) and nitrogen (N). This gas contains substantial energy and can be used in a variety of ways.
» The hot gas rises up through the waste in the reactor and begins the gasification process on the material piled in the reactor. By the time the waste has reached the bottom of the reactor, the high temperature, oxygen starved environment, has totally transformed all organic compounds into a gas.
» The gas that exits from the top of the reactor and is made up of primarily carbon monoxide, hydrogen, water and nitrogen. Small amounts of chlorine, hydrogen sulphide, particulate, carbon dioxide and metals with boiling points less than 1200ºC are contained in the gas. Because of the low oxygen atmosphere and high temperature, the base elements of the gas cannot form toxic compounds such as furans, dioxins, NOx, or sulphur dioxide in the reactor.
» As the gas exits the reactor it first goes to a proprietary gas reformer and then it is cooled in a series of high temperature heat exchangers. The sensible heat is reduced to about 270ºC and is used to generate high-pressure steam that is fed to a steam turbine to produce electricity.
Waste pollution is a serious threat to the environment and can broadly be defined as any pollution associated with waste and waste management practices.. Typical materials that are found in household waste, and which have specific environmental impacts, include biodegradable wastes, batteries, aerosols, oils, acids, plastics and fluorescent tubes.
Biodegradable waste is of specific concern because it breaks down in landfills to form methane, a potent greenhouse gas, and residual toxic material. Methane is a ‘greenhouse gas’ and, if not prevented from entering the atmosphere, it will contribute to climate change. Similarly, the toxic residues will leach into the surrounding soil and water system with damaging consequences for the local environment.
Through the years, municipalities have been attempting to reduce the amount of municipal solid waste (“MSW”) sent to landfill sites. Primarily, this has been accomplished through the introduction of various forms of recycling methods.
In the UK this includes a combination of coloured bins and bag systems to entice commercial and residential contributors to recycle and compost as much of their MSW as possible.
In reviewing the anticipated success of these programs, it is believed that the maximum possible, certainly in the short term, may be in the region of 60% elimination of MSW sent to landfill.
In many cases this still leaves a substantial amount of residual MSW to be dealt with, requiring either expansion of local landfill sites or trucking to destinations, which in some cases are well outside the local area in which the MSW is generated Due to the inherent make-up of MSW, containing both organic and inorganic waste streams, when land-filled, they create serious airborne contaminants into our atmosphere.
These contaminants are built up over time, as the MSW deteriorates, with the net effect being the creation of green house gases(“GHG”) such as CO2, which when introduced into our atmosphere has a negative effect on the ozone layer, i.e. GHG which is clearly a major contributor to the much discussed Global Warming Effect on our planet.
The Landfill issue is enormous
Global Issue
There is now a worldwide critical problem to find an environmentally friendly way of disposing of domestic and commercial waste. The Biosphere is the only real answer at present.
As an example, America and India are between them producing over 270 million tonnes of waste each year, the problem is enormous and a solution urgently needed. Landfill is now recognised to be environmentally unacceptable and, in any case, obtaining new sites is becoming increasingly difficult. With space in current sites rapidly disappearing, we could soon be up to our necks in waste with, apparently, few options for tackling the problem.
Green House Gas Emission by Sector
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Gasification is the process in which a carbon-based, high-caloric material also known as municipal solid waste (MSW) (i.e. anything other than glass, masonry, metals and nuclear waste) goes through a thermal transformation process in an oxygen-deprived environment in which it is converted into a variety of products: an inert ash, various chemicals, synthesis gas (syngas) and steam.
The EWS Biosphere System (Solid, Liquid and toxic Waste) is a proven technology which:
Reduces » Landfill Volume by 93%.
Consumes » 172 Tons of Waste/Unit/Day.
Recovers » Brown Field and Landfill Sites for Development.
Generates » 3-7 Megawatts Continuous Power/Hr.
Distils » 3-7 Megawatts Continuous Power/Hr.
Produces » Syngas, other chemicals and inert ash. The ash is then recycled into concrete, masonry and Carbon Black.
Control System
The plant design incorporates an advanced control system which is fully interlocked with Programmable Logic Controllers (PLC’s) to control all of the safety devices such as photo-cells, limit switches and flow switches.
The PLC’s are set up to control the start up and shut down sequences. The whole system is tied into a Distribution Control System (DCS) and controlled by a main computer. All water produced from the densification of the MSW and wash-down system will be collected in an underground holding tank. The water will then be treated, cleaned and a portion reused with the remainder sent to sanitary sewer. The solids will be extracted every two to three months and mixed in with MSW to produce pellets. A biological air filtration system is installed in the MSW receiving and sorting section of the facility. This unit will exchange the air every fifteen to twenty minutes and collects all of the remaining moisture and eliminates a minimum of 92% of all odours.
The design of the production plant ensures that there is no adverse effect on the natural environment, or on the health and safety of people working in the plant, or in the local community. Dust, odour and debris emissions are minimized in the process facility by maintaining a negative pressure in the tipping floor and hopper area and continuously introducing fresh air.
EWS Holdings Ltd
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EWS offers each City a unique opportunity to tackle its waste problems. With a combination of technologies, EWS can offer an environmentally friendly solution to virtually any waste problem including:
» Tyres
» Medical and other hazardous waste
» Sewage sludge
» General commercial and industrial waste
» Coal dust
» Oil waste
Local Electric Utility partnerships.
Typically the local electricity utility is the retailer of choice for electricity to the City in which it resides and operates the local power distribution grid. As a producer of electricity from a renewable source, EWS is welcomed as a partner by electricity utilities as EWS is able to help them to meet their obligations to supply an increasing proportion of electricity generated from renewable sources.
Water and Waste Water Services partnership.
The effluent (“Sludge”) from a local municipal Sewage treatment plant can be dried and pelletized to produce additional fuel pellets for use in the Gasifier. Disposal of sludge is a huge problem worldwide and Water and Waste Water Service providers are constantly searching for an environmentally acceptable solution. Pelletization and processing in a Biosphere System has the same benefits as for MSW – it removes a problem and provides additional green energy.
Local District Energy.
A district energy system, operated properly, is another way to reduce green house gases, caused by emissions from locally distributed gas or oil fired hot water systems in commercial buildings. Heat and/ or steam from the Gasification of MSW can be distributed in district energy street piping systems to local business or communities. This is inherently much more efficient as it makes maximum use of fuel used to produce the ultimate energy medium.
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Nedbank Capital is a division of Nedbank Limited, one of the largest South African banks. Nedbank Capital has been set up to promote and fund all carbon reducing projects. Nedbank Capital seeks to provide seamless specialist advice, debt and equity raising and execution, and trading capabilities in all the major South African business sectors. Principal clients include the top 200 domestic corporate, parastatals, leading financial institutions, non-South African multinational corporate and clients undertaking major infrastructure and mining projects in Africa, as well as emerging BEE consortiums.
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Currie and Brown
is one of the UK's largest project and cost management companies dedicated to assisting clients in respect of procurement, construction and management of the built environment. It is one of the top ten construction cost management companies worldwide.
With more than a 100 years of experience, drawn from markets around the world, Currie and Brown offers a depth of knowledge and expertise unsurpassed in its field. Its reputation is founded on its people and the quality of its delivery. It provides real value to its clients by ensuring high quality service wherever it operates.
Currie and Brown has always viewed property and construction assets as having complex, integrated lifecycles. It delivers a portfolio of services along this lifecycle, from concept through design and construction to the management and maintenance of a project or asset. It is this perspective which forms the core of its "Asset Management" approach, utilising its core skills in cost, project and programme management, while its advisory services group provides whole-life asset services.
It operates in a number of sectors where globalisation, change, market conditions and competition drive its clients even harder to be more innovative, flexible and adaptable. Its combination of knowledge, professional skill, technology and positive attitude enables it to derive real value for its clients. Its services are provided to leading businesses and Governments on a global scale, through its network of offices.
