Excerpts from “Technological Regulations, initial data and recommendations for designing a plant-module for thermochemical processing of municipal waste” Part 1
“Technological Regulations” have been developed as an illustration of a way to design plants for thermochemical processing of municipal waste. While designing various objects, inconsistencies in the composition of municipal garbage requires, first of all, clarification of specific characteristics of the initial waste typical for a given locality. The technology is based on a modular scheme that allows to flexibly adapt to various amounts of recyclable waste and changes in its composition. The proposed plant is an autonomous process line (a module) from which it is suggested to build plants of any capacity. The modular scheme allows to develop waste recycling in stages and to use the equipment of various companies in order to completely assemble a plant. At the initial stage of the technological process start-up, imported liquid fuel is to be used, for example, fuel oil, and then, after stops for repairs and sanitization, previously accumulated liquid fuel will be consumed.
The “Technological Regulations” is the intellectual property of the author and cannot be used or transferred to third parties or used without his permission. It is forbidden to copy or reproduce the document as a whole or in part without reference to these “Technological Regulations.”
The purpose of the Prospectus is to search for companies or individuals who might be able to finance construction of a plant based on the suggested technology. If necessary, the author can act as a consultant in the design, installation of equipment and staging the technological processes of the plant.
For general acquaintance with the contents of the “Technological Regulations” some excerpts from several of its sections are presented below.
Preface.
Technological regulations, initial data and recommendations for designing a plant-module for thermochemical processing of municipal waste have been developed on the based of U.S. Patent 8739708: “Method and Plant for Processing contaminated waste (2014)”, Patent 7611576: “Method and Plant for Processing waste (2009)”, Patent 6202577: “Method and apparatus for treating refuse (2001)” , and USSR Inventors Certificate 982757: “Installation for production of carbon dioxide from flue gases (1982)”; they describe various options for technological plant schemes developed by the author during the period of 20 years (1998-2018). The “Technological Regulations” use most optimal and economically viable technical solutions given in these patents, the author has also used numerous literature data on the operation of industrial installations and the results of research conducted by a number of research, design and commissioning organizations. The author is grateful to the engineer chemist – technologist A. N. Boguslavskyfor participating in the initial stage of discussing literary sources and a possible option for the technological process.
“Technological Regulations” include development of a technological scheme of the process, calculations for material, heat, water and air balances of the plant, calculations for separate stages of the technological process and the choice of equipment for producing liquid fuel and accompanied secondary products, the stage of utilizing the secondary heat, and the plant water consumption schedule. Datasheet has been compiled, manufacturers of the necessary equipment have been listed, recommendations have been given on utilization of secondary products obtained in waste processing. Consumption of fuel, electricity, water, raw materials, auxiliary materials has been calculated, the main technical and economic indicators of the plant technological process have been determined, and the environmental safety of the process of thermochemical processing of municipal waste has been illustrated.
“Technological Regulations” include 447 pages of the main text, 4 pages of the annex, 5 drawings, 122 tables, the datasheet of the main equipment required for the plant, which includes 145 positions, and a list of references consisting of 649 titles.
Abstract.
For the first time in the world practice, it is proposed to create an enterprise on the basis of a new, highly efficient, fuel-producing and environmentally friendly technology for waste processing. The waste includes solid municipal waste of any morphological composition, as well as this waste mixed with industrial oil waste (oil sludge, acidic tars, etc.), contaminated with toxic chemicals and oil products of earth, electrical, electronic and cable scrap, used tires, all types of plastics, sludge deposits accumulated by enterprises engaged in clearing municipal wastewater, contaminated sediments at the bottom of reservoirs, poultry waste, biologically polluted waste produced by hospitals, contents of animal burial grounds, waste dumps (landfills), etc.
The technology has been patented, is based on thermochemical processing of waste and uses well-known and repeatedly proven industrial methods, although it has not yet been fully implemented anywhere in the world. Essentially, a new technological chain has been developed, consisting of old, well-known links, which allows to immediately proceed to designing and building the plant. Its outstanding features are as follows:
- it allows to efficiently process waste of any moisture, including frozen waste;
- it does not require pre-sorting of waste at sorting complexes by manual labor, separators are used to separate glass, ferrous, non-ferrous and precious metals;
- the technological scheme of a workshop for getting raw materials ready for production provides multistage use of polluted air coming out of premises and out of technological equipment, with subsequent heating at the expense of slag dry-cooling and air blowing into the furnace, which, along with fuel saving, provides for comfortable working conditions for maintenance personnel, and protects the environment from pollution (odors);
- it produces fuel, which, due to deep utilization of heat in production processes, excessively provides for the plant’s own needs. Thus, production of excessive fuel eliminates the need to use fuel from foreign sources and ensures output of liquid fuel (pyrolysis resin) to the market (with the accepted morphological composition of the waste being 163 kg / ton of garbage. If the amount of tires and plastics in the initial waste increases, the fuel yield significantly increases as well). Pyrolysis resin sent to thermal power plants, industrial and district heating boilers as an additive to fuel oil, saves oil fuel and improves the environment. It is possible to produce gasoline and stove oil which meet all the typical requirements of the Standard and can be used in appropriate fuel-burning equipment, which is especially important for countries experiencing shortages of fuel;
- it is possible to generate electricity directly at the plant from all produced commercial fuel, for example, in a diesel generator or at gas turbine plants. At the same time, the plant’s own needs are fully provided for, which makes it possible to stop using electricity from foreign sources and provides additional supply of electricity to the market in the district electric networks (with the assumed morphological composition of the waste being 244 kWh / ton garbage). At the same time, the cost of electricity generated from own fuel produced at the plant will be 60% lower than the cost of electricity at thermal power plants (TPPs);
- it produces a variety of commercial, environmentally- friendly secondary products: ferrous and non-ferrous metal scrap, broken glass and/or fine glass powder, dry calcium chloride, liquid carbonic acid, concentrate of non-ferrous and precious metals obtained from electronic, electrical and cable scrap, slag and/or slag-concrete products, free of heavy metals, glass and sulfur;
- it produces a variety of commercial, environmentally - friendly secondary products: ferrous and non-ferrous metal scrap, broken glass and/or fine glass powder, dry calcium chloride, liquid carbonic acid, concentrate of non-ferrous and precious metals obtained from electronic, electrical and cable scrap, slag and/or slag-concrete products, free of heavy metals, glass and sulfur;
- it excludes burial of activated carbon with sorbed heavy metals, and, accordingly, allows to make free land space and eliminates the cost of maintaining a special landfill. The decision on what to do with the waste coal depends on local conditions; it may be dispatched either 1) as a marketable product to non-ferrous metallurgy enterprises dealing with polymetallic ores, where it is used as an expensive additive to the charge, or 2) to a company producing activated carbon and servicing installations for purifying various substances with these coals, for regeneration of these substances and repeated reuse;
- concentrate of non-ferrous and noble metals, isolated from electronic waste, purified of non-metallic fraction (plastic, wood, textolite, organic resins, rubber, etc.) provides the minimum amount of polluting emissions to the atmosphere during subsequent smelting at the refinary. The nonmetallic fraction is fed into the pyrolysis furnace, which allows additional output of fuel directly at the plant;
- it shortens the production cycle, improves physical and mechanical properties of slag-concrete products, ensures production of frost-resistant high quality items at the expense of a mild mode of their thermal-moisture treatment with moist low-temperature flue gases after coming out of calcium chloride dryers;
- consumption of aqueous solution of technical monoethanolamine for replenishing natural losses
in the process of carbon dioxide production is reduced by 60-70% compared to the use of existing installations;
- the scheme of the plant water supply presupposes complete processing of the obtained calcium chloride solution, which excludes its discharge into storage ponds or sewage systems, and ensures environmental protection from pollution;
- there is no industrial wastewater and no solid waste, i.e. there is no necessity to build wastewater treatment plants and solid waste landfills;
-there is no consumption of industrial water from foreign sources, and, accordingly, no violations of the environmental water balance. All the water for the plant’s industrial needs is generated in the course of the technological process of municipal waste treatment, which is especially important for hot and arid regions with water shortages;
- drinking water from the urban water supply network is used only for producing hot water supply, in showers, toilets, the plant laundry room and its canteen;
- production waste consists only of flue gases, whose composition fully complies with all requirements of environmental safety standards. This is achieved directly on-site, in the process of waste treatment and manufacturing commercial products, without installing any additional cleaning equipment. Compared with traditional methods of burning fuel in industrial boilers and stoves, the proposed technology:
a) does not produce organochlorine compounds: polychlorinated dioxins, furans and biphenyls and, accordingly, excludes their release into the environment, which is much easier than binding molecular chlorine in flue gases, and especially destroying dioxins;
b) completely (100%) eliminates the release into the environment of mercury and 90% of compounds of other heavy metals, including radioactive metals;
c) excludes emission into the environment of carbon monoxide, oxides of sulfur, phenol, of organic easily volatile and foul-smelling substances;
d) reduces emission to the environment of nitrogen oxides by 50%, of benzo (a) pyrene by 7-10 times, of calcium chloride dust by 99.9%, and of greenhouse gases - carbon dioxide by 36.4% and methane by 100%;
- uses serial, easily accessible equipment, all processes are continuous and fully automated;
- for construction of factory buildings, it is recommended to use metal frame construction technology, which is characterized by low production costs and reduced construction time. The area occupied by the plant-module is 5000 m2;
- the capacity of the enterprise may vary widely, since production uses separate autonomous technological lines (modules). Depending on local conditions, it is possible to build factories of low productivity (mini-factories), whose number and geographical location for a given area is determined by a technical and economic calculation. This will reduce the amount of long-distance transportation of waste by trucks and heavy trailers and, accordingly, will reduce the costs and the additional burden on the environmental situation created by vehicles;
- such a plant can function completely autonomously, for example, it can operate in remote areas on old landfills of municipal solid waste, since the technology allows to fully meet the plants own needs for fuel, process water and electricity, in total absence of industrial wastewater and solid waste; this will terminate the release into the air of landfill gases (primarily methane and carbon dioxide), as well as provide for the possibility of recultivation and rehabilitation of significant areas.
- provides garbage recycling for an the average-statistical USA residential locality with the population of 112,000 persons (in Israel – of 126,000 persons, in Australia – of 137,000 persons, in Germany – of 142,000 persons, in Italy – of 154500, in Russia – of 191,000persons, in Japan – of 207,000 persons, in Brazil – of 218,000 persons, in Kazakhstan – of 266,000 persons, and in the Ukraine – of 283,000 persons). Meanwhile, the capacity of the enterprise and, accordingly, the number of people served can vary widely, since production consists of separate autonomous technological lines (modules).
The proposed technology is self-sustained only due to manufacturing environmentally friendly products; and even without estimating prevented damage to the environment, the plant-module (rated capacity 10 tons / hour, 85000 tons / year) with an expected cost of $ 5,575,000 provides for an extremely fast investment return - 7 months, and with free admission to the plant of municipal waste - 10 months, i.e. less than a year. And this calculation does not take into account the economic efficiency of possible use of hot water, which can be additionally obtained as a result of deep heat recovery of the plant’s non-acidic flue gases, for instance, for subsoil heating of the ground in greenhouses and conservatories, year-round cultivation of fish farming in artificial reservoirs, hot water supply of residential areas of the nearby city or a town, etc. Of considerable economic and environmental interest is also construction of a station for cleaning garbage trucks serving the plant, with subsequent return of polluted warm water into the production process. However, implementation of these additional measures depends on specific local conditions, and at this stage is not considered, “Technological Regulations” only demonstrate such a possibility.
Table of contents.
Preface................................................................3
Table of contents…………………………………………………………………….......................4
List of drawings..............................................................8
Conventional symbols................................................................8
Abstract …………………………………………………………………………............................9
1. Some prerequisites for development of the process of municipal solid waste pyrolysis........14
1.1. Features of municipal solid waste pyrolysis.............................................................14
1.2. Cellulose pyrolysis.............................................................15
1.3. Rubber pyrolysis ………………………………………………………….........................16
1.4. Pyrolysis of polymers ……………………………...………………………………………..16
1.5. Pyrolysis of skin and food waste …………………………………………………………....16
1.6. Characteristics of limestone …………………………………………………………………17
1.7. Dioxin................................................................17
1.8. Heavy metals...............................................................19
References…………………………………………………………………………………21
2. Technology of thermochemical processing of solid municipal waste………………..................22
2.1. Organizing separate collection of solid household waste and the cost of its disposal (US experience)………………………………………………………………………………………..22
2.2. The choice of an optimal pyrolysis technology option for processing solid household waste………………………………………………………............................................26
2.3. Brief description of the technology …………………………………………...........................33
2.4. Recycling plastics waste.......................................34
2.5. Plant construction priority ................................36
2.6. Plant operation mode ...............................37
2.7. Products obtained as a result of recycling solid municipal waste and recommendations
for their use................................38
References…………………………………………………….…………….......41
2.8. The technological scheme for plant municipal solid waste processing......................................45
2.8.1. The technological scheme for the workshop preparing raw materials for recycling
of municipal solid waste at the plant................................45
2.8.2. The technological scheme for primary production of the plant processing municipal
solid waste.....................................51
3. Material balance at the stage of municipal solid waste pyrolysis...........................70
References.....................................82
4. Description of, calculation for and selection of equipment for separate stages of the
technological process..............................85
4.1. Preparation of raw materials for production ...........................85
References...............................117
4.2. Preliminary drying of recyclable waste and steam condensation ..................120
References......................135
4.3. Pyrolysis of recyclable waste................................136
4.3.1. Heat balance at pyrolysis stage ....................................145
4.3.2. Basic equipment at pyrolysis stage ..............................146
4.3.2.1. Technical characteristics of pyrolysis furnace (version with non-finned outer
surface of the rotating drum) .....................................151
4.3.2.2. Technical characteristics of pyrolysis furnace (version with finned outer surface
of the rotating drum) ..........................152
References.............................................156
4.4. Stage of purification and condensation of pyrolysis gases ........................157
4.5. Stage of blowing organic products from liquids generated in the production process...............181
References.............................................185
4.6. Stage of washing and centrifuging solid pyrolysis products....................187
4.6.1. Initial data for development and coordination of technical specifications for
manufacturing inclined twin screw extractor ..................................193
4.6.2. Recommended mode parameters for purification process of solid residues
pyrolysis from heavy metals and calcium chloride .................................195
4.6.3. Flow parameters for inlet and outlet of the extractor and the centrifuge.................................198
4.6.4. Basic equipment at the stage of washing and centrifuging solid pyrolysis products..............201
4.7. The stage of heavy metals separating...........................209
References..........................................................223
4.8. Firebox ......................................................228
4.8.1. Firebox heat balance….......................................229
4.8.2. Firebox basic equipment………..................................241
References.........................................................253
4.9. Slag cooling stage............................................256
References..........................................................264
4.10. Heat recovery of the plant flue gas..........................266
References..........................................................280
5. Stage of obtaining secondary products of the production process...283
5.1. Production of dry calcium chloride …….........................283
5.1.1. Heat balance of the process of calcium chloride drying.......286
5.1.2. Basic equipment at the stage of production of dry calcium chloride ...287
References...........................................................298
5.2. Liquid carbon dioxide production .............................301
5.2.1. Basic equipment at the stage of liquid carbon dioxide production....303
References...........................................................311
5.3. Production of slag-concrete articles..........................313
5.3.1. Basic equipment at the stage of manufacturing slag concrete articles .............319
References..........................................................337
5.4. Cooling water recycling system of the cooling tower ..........340
References...........................................................345
5.5. Recycling of electronic, electrical and cable wastes ..........346
References..........................................................360
6. Smoke-stack..............................................362
References........................................................366
7. The plant heat balance.........................................367
References..........................................................369
8. Check-list of basic equipment for module plant for processing municipal
solid waste..........................................371
9. Electric power capacity consumed by the plant. Basic equipment for power supply of
plant consumers........402
References...........................................................413
10. Assessment of environmental safety of the thermochemical process of recycling
municipal solid waste............................................415
References...........................................................429
11. Output of marketable products. Consumption of raw and supporting materials………...........433
12. The main technical and economic indicators of technological processes at the
plant for thermochemical processing of municipal solid waste ...........436
12.1. Cost of performed services and manufactured products...............437
12.2. Main indicators of the plant operating costs ................438
13. Conclusion....................................................443
References........................................................445
14. Appendix….......................................................448
2.1. Organizing separate collection of solid household waste and the cost of its disposal (US experience).
Analysis of the US experience in collection and disposal of solid municipal waste during the last decades of the 20-th and the beginning of the 21-st centuries has demonstrated that before processing, the waste should be collected, sorted and sent to recycling plants turning it into secondary materials that, along with natural resources, should be once more used in the production cycle. The purpose of separate collection of SMW is to reduce the amount of household waste that can be disposed of in a landfill or burned in incinerators, as well as to reduce the harmful effects of waste on the environment. However, burning the remaining part of the waste at incineration plants in order to obtain secondary electricity, while saving substantial amounts of traditional fuel and rapidly destroying waste, requires high capital expenditures, a complex and expensive (up to 50% plant cost) system of cleaning and disposal of toxic ash and slag (1). The 1970s saw construction of the first incineration plants, but it was not yet known what environmental damage they could cause: insufficient conversion of raw materials, formation of significant volumes of flue gases containing a ""bunch"" of carcinogens (dioxins, furans, benzapyrenes, and some other oxygenated condensed molecules), as well as high costs of units for waste processing, have limited the possibility of further dissemination of this method (17). After a sharp rise in cancer incidence and research that proved the existence of a link between cancer and incineration plant emissions, the percentage of waste burning started to decrease: in the US, out of 150 incineration plants, only about 70 have remained today (2). Moreover, at the end of the last century some countries prohibited the use of waste incineration by law (17). At the same time, the US experience has demonstrated that it is advisable to do separate waste collection only for those materials for which the problem of utilizing them as secondary raw materials have already been resolved, i.e. there is a market for them. This way, in the second half of the 90s many types of solid household waste ceased to be “garbage,” they became valuable goods, representing an important segment of the current American market. Recycling these materials has brought the US both the economic effect of creating additional jobs and added value generated in industries receiving products from recycled materials, and the environmental effect, mainly in preserving the countrys natural resources (1). However, the industry is currently facing a double threat: the cost of recovering waste has plummeted over the past five years, and the amount of effort of its recovery has increased (3). Rob Taylor study, conducted as part of a government recycling program in North Carolina, Department of Environmental Quality, found that the average market value of a ton of recyclable materials arriving at a state-of-the-art facility had fallen from over 0 in early 2011 to less than at the end of 2015. This value has since recovered slightly, according to Taylor, and is a little over 0, but it still leaves the industry struggling to make a profit from millions of tons of recyclable materials that Americans throw away every year. “There are many reasons for price reductions in the recycling market, ranging from global trade policy to reducing the number of newspaper readers,” said David Biederman, the executive director and general manager of the North American Solid Waste Association. Most of the US waste used to go abroad, but in 2013 China set new limits on imported waste. The decision of the Chinese Government to ban the import of mixed plastic and mixed paper recyclables has sent recycling markets into a tailspin (4). In other countries, there is also “a decline in demand for this material, as growth has leveled off there,” said Biederman. Low oil prices made it a cheaper raw material for production of new plastic bottles, therefore manufacturers do not have much need for regenerated plastic. In addition, packaging manufacturers have figured out how to make thinner bottles and cans, so they do not need as much raw material. As circulation of printed newspapers plummeted, the recycling industry lost both a huge customer for recycled paper and a huge source of recyclable materials. Compared to the processing industry, “what was once a valuable commodity five years ago is less valuable now,” said David Biederman. This change is perhaps the most dramatic for glass. In most American cities, a glass bottle thrown into the waste basket is useless for recycling, and if it breaks, the fragments can make paper or other material in the mixed basket useless. “We work hard to keep the glass in the system,” said Kif Harrison, CEO of Recycling Partnership, a non-profit enterprise committed to improving recycling programs throughout the country. But ""it has a very minimal market value, because it must compete with the sand from which raw glass is made."" Some municipalities have simply stopped collecting broken glass in their recycling programs. For example, Santa Fe (California) has revised its recycling program and announced that it will no longer collect glass from households.
When cities began to implement municipal waste disposal programs (1980–1990), it was assumed that the proceeds from recovered materials should offset the cost of collecting and separating waste, but this did not happen. Kevin Miller, a recycling manager for Napa, California, said: “We only return about 20% of the cost of collecting, sorting and delivering materials. But these are not all the bad news in the industry. The growth of online shopping has caused an explosion of cardboard packaging entering the recycling stream. There is more corrugated cardboard in the system than ever before, which is a valuable and easily recyclable product, but only if it is not contaminated in the bin"". At the same time, Kevin Miller and environmentalists point out that recycling has other economic benefits, such as reducing the use and cost of landfills, reducing the need for disposal of primary materials. However, the burden of paying the expenses falls on the cities or their residents who pay for “junk” service, because the US have not followed the path of many European countries and do not require manufacturers to take responsibility for removing or restoring their products and packaging (3). In addition, state legislators, environmental authorities and recycling advocates who inadvertently supported unrealistic recycling goals, without taking into account the need for end markets, the risk of commodity price fluctuations and the reality of what is needed to change human behavior have inadvertently helped to create this mess. Too many state legislators voted in favor of laws requiring fast implementation of recycling goals without first finding out whether these goals were achievable (4).
Great hopes were pinned on creating biodegradable bags and disposable tableware, but they turned out to be much more harmful than non-biodegradable ones. Biodegradable products consist of corn starch, polystyrene and an additive that turns all of this into powder. The ware and packages from ordinary polystyrene can be later removed from dumps and processed. Polystyrene dust, into which “biodegradable” products turn, is not only impossible to be removed from the total mass of garbage, but because of its size, “micro plastic can migrate along the food chain and end up in our plates.” In addition, modern processing technologies do not have the ability to secrete biodegradable polymers from the total plastic flow entering the processing line. This reduces the quality of recycled materials and can lead to the fact that the batch of plastic contaminated with biodegradable polymers cannot be recycled. At the same time, environmentally friendly burning of biodegradable materials is also impossible, since it leads to the release of dioxin (22, 23).
In January 2018, China banned the import of waste, and shipments were redirected to Southeast Asia, which was soon overloaded, forcing governments to take action. Malaysia announced the ban in October 2018. At the same time, they clarified that the garbage still enters the country with falsely declared goods, but the government hopes to completely stop the trade by the end of 2019. Thailand stopped issuing import licenses in 2019 and will introduce a ban in 2020. The Philippines said it was shipping 69 containers of garbage back to Canada. Indonesia will tighten its waste import regulations after detecting shipments containing toxic waste. India and Vietnam also announced restrictions. As Southeast Asia ceases to accept these materials, companies will look somewhere else. According to the report (60), garbage is currently exported to countries in Africa and Asia such as Kenya, Senegal, Ghana, Laos, Turkey, Cambodia, etc.
The crisis in systems of processing recyclable materials is most probably likely to cover all highly developed countries in the world. So, for example, the warehouses of Melbourne (Australia) have accumulated ""mountains of secondary raw materials which nobody needs and which goes to landfills"". SKM company went bankrupt. The Minister of the Environment of Australia, said: ""Sending recycled materials to landfills is always the last resort, but in some cases it may be a safer option than letting the materials intact. Public safety should come first."" However, it is absolutely clear that “tomorrow all governments of the third world will refuse to accept garbage, and sorting stations will be overwhelmed by such a stream of recyclables that no environmental startups will have time to process” (43). Thus, this is not a way to solve the problem, it is a redirection of all responsibility and all the problems to the next generations. This is a temporary solution that is completely inconsistent with the “long-term message for nations: sort out your own garbage”. But how can this be done? (42).
The way out of the current situation and, accordingly, an effective solution of the problem that has arisen, it seems to me, is possible only as follows. At the places of formation and /or at the existing sorting complexes, it is necessary to select only such amount of uncontaminated material that is necessary for the stable operation of the industry, including effective marketing of the goods produced. The remaining unsorted municipal waste should be fed to the plants, the technology and instrumentation of which are presented in the “Technological Regulations” for production of liquid fuels and other related commercial, ecologically safe secondary products, whose sales are always ensured regardless of the market situation.
According to “Solid Waste and Waste Disposal Facts” (5), in order to send garbage for destruction to a landfill, you need to pay an average of per ton, to burn - between and . For support competitiveness of this project, even compared to the landfill when calculating the main technical and economic indicators of the plant’s technological process, the price of accepting solid household waste for processing at the plant has been accepted to be per ton. With no-cost acceptance of municipal waste for recycling, the projected plant also proves to be highly cost-effective.
2.2. The choice of an optimal pyrolysis technology option for processing solid household waste.
Every year the amount of household human waste on the planet increases, with up to 70% of which being organic. Environmental requirements have been tightening, various waste management programs have been initiated, but processing problems remain unresolved. Currently used technologies create significant difficulties in environmental protection:
1). Introduction of new, very strict emission standards for waste-to-energy facility (WEF) is a key point in the policy of reducing emissions of harmful substances into the environment. Modern installations for the purification of flue gases of boiler units, which will be adopted in the projects of the WEF, will undoubtedly comply with these standards in all respects. However, the maximum allowable concentration limits (MAC) not may be applicable to emissions such as heavy metals and dioxins. Toxic metals are released in the form of salts or oxides, that is, in a stable form and can lie for an indefinite number of years, gradually accumulating and entering the human body with dust. Dioxins do not disappear from the environment for decades. Thus, these harmful substances with the effect of summation will accumulate and cause irreparable damage to nature and human health.
2). Currently, a wide variety of attempts are being made to use slag and ash from WEF. But slag and ash are quite toxic, their toxicity consists mainly of the toxicity of heavy metals. The concentration of metal oxides in slag and ash is 2-3 orders of magnitude (and sometimes more) higher than in incinerated waste. In addition, ash and slag materials, due to mechanical carbon loss of waste, contain up to 20 - 30% of unburned fuel. For use, for example, in the construction industry such materials are not suitable. According to European standards, the loss of torrefaction should not exceed 5% by weight. Thus, in its majority, ash and slag must be cleaned of heavy metals and to sort from excess unburned fuel to its content of not more than 5% by weight. All modern existing and proposed technologies do not provide for preliminary purification from harmful substances, but only “encapsulate” them (including heavy metals) in the mass of molded products, that do not, according to the authors, allow ecotoxicants into the environment. However, a number of substances, for example, such as sulfur, can cause degradation of bricks, which leads to the penetration of pollutants into the environment. Under certain conditions, water-soluble salts of toxic metals can also be washed out by rains, for example, when the acidity of rainwater changes “according to weather conditions”. Since these harmful substances are highly resistant toxicants, most likely the products will be toxic for many decades. Wastewater after cooling the slag and from scrubbers wet cleaning fly ash is also heavily contaminated with salts and toxic metals. This water is always either highly alkaline or highly acidic. Both are bad, since special treatment is required with subsequent discharge to treatment plants and the consumption of a significant amount of fresh water from extraneous sources. Thus, the problem of rational, environmentally friendly use of slag and ash of WEF does not currently have a satisfactory solution.
3). During anaerobic digestion of biodegradable waste, the compost obtained under any operating conditions of the plant is saturated with heavy metals and other harmful components contained in garbage, has high toxicity and is actually only suitable for reclamation of disturbed land and covering of landfills. Therefore, various attempts are made in the world to clean contaminated composts. The cheapest and most effective way to clean contaminated composts is the method of “phytogenesis” - photosynthesis of purifier plants planted on the compost being cleaned. To prepare soils suitable for growing these plants, you need to mix compost with ballast soils, peat or sawdust. In the future, as “ballast” soils, it is possible to use the soil and subsoil of urban areas with industrial pollution with the aim of their joint cleaning to form territories for development. Recent circumstances may become dominant in the income structure of the enterprise. The biomass of plants with technogenic pollution obtained during photosynthesis is to be burned, and the ash to be bound and buried. All these measures require significant material costs and a long time for their implementation. The use of compost as fertilizer directly from bio-reactors for the processing of organic waste, taking into account the effect of the summation of heavy metals and the super deficit of the country""s space, will lead to deep pollution of agricultural land with heavy metals, the restoration of which will become the country""s national problem.
4). Simultaneously with compost production, biogas is produced, which is transported to the storage tank through filters that remove excess moisture and traces of naturally formed hydrogen sulfide. It should be noted, however, that in addition to the main components (methane, carbon dioxide, nitrogen, oxygen, hydrogen), biogas from waste contains so-called trace impurities, which include: toluene, ammonia, xylene, carbon monoxide, nitric oxide, formaldehyde, sulfur dioxide ethylbenzene, hydrogen sulfide, phenol, hydrogen cyanide. A number of other standardized components of emissions of the 2nd class of toxicity, such as halogenated hydrocarbons: dichloromethane, trichloromethane, chloroethane, trichloroethane, as well as trichlorethylene and its homologs, were also found here. At the same time, the total chlorine content in microimpurities is 25–40 mg / m3, which is 250–400 times higher than the MPC. These data not only confirm the danger of biogas from MSW, but also indicate the need for special expensive gas purification systems when burning biogas for any purpose for any application. In addition, the above data with a high degree of probability indicate the presence in the biogas combustion products of any homologues of the dioxin series, because there are all conditions for the formation of these hazardous compounds in the combustion products. Thus, the market use of biogas from solid waste as an energy fuel is to some extent limited by the high cost of environmental protection devices in energy generating plants. German experience has shown that only biomethane (purified biogas according to the standard) can be used by consumers, which requires additional investment and energy costs.
At the moment, the governments and the communities of many countries of the world are engaged in the development and introduction of new technologies that would make it possible to efficiently utilize organic raw materials and to obtain new materials and energy as a result of their processing.
One of the most promising technologies for processing organic waste is pyrolysis - thermal decomposition of the normal structure of a substance through high temperature without access of oxygen. There are two types of pyrolysis.
Slow pyrolysis (SP) is thermal destruction of the original substance without oxygen access, where the heating rate of the specified substance is measured in degrees per minute, per hour. SP is analogous to the process of bringing water to the boiling point. It should be noted that the presence of ubiquitous polyvinyl chloride and other polymers and various chlorine compounds in the waste being destroyed contributes to producing dioxins in the flue gases (37).
Fast pyrolysis (FP) is thermal destruction of the original substance without oxygen access where the heating rate of the initial substance is hundreds, thousands of degrees in fractions of a second. FP can be relatively compared to the process of boiling a drop of water in hot oil. It can also be referred to as ""explosive boiling."" Destruction takes place at the molecular level of crushed and pre-dried particles of any organic substances, when this occurs. Thermal energy is supplied to the source material at high speed and without oxygen. The substance undergoing BP is instantly turned into its primordial stage, where it has two states - solid and gaseous, while experiencing an entropic explosion (breaking of intermolecular and intramolecular bonds) accompanied by exotherm (release of a large amount of thermal energy). The released atoms move along carbon-carbon and carbon-hydrogen chains and form molecules of new synthetic substances that differ in their properties from the properties of the ingoing material. The disadvantage of the BP process is the requirement for thorough preparation of the ingoing material: grinding of particles of the initial substance to the lowest possible fractions and preliminary drying of the initial substance to relative humidity of 0-5% (24).
Thus, for example, the conditions for continuous low-temperature high-speed (fast) pyrolysis of hardwood in a fluidized bed for producing liquid fuel and coal are as follows: the temperature from 425 to 650њC, atmospheric pressure, wood particle size from 0.1 to 0.25 mm, contact duration from 0.4 to 1.0 sec. The yield of liquid products at the optimum temperature of 500њC reaches 65%, of the resin - up to 56%, which is a huge advantage of fast pyrolysis, since such a high yield of products during slow pyrolysis is not possible (25, p.75). However, obtaining almost completely dry, crushed to a particle size of less than 0.5 mm unsorted MSW, especially on an industrial scale, is not realistic, and not so much because of huge energy intensity of the process, but because of multi-component of the composition of the waste and its variability. According to (26, Section “The issue of recycling household waste using fast pyrolysis technology requires certain explanations”), there appears a “strict need to sort waste into generic species (wood, paper, metal, glass, etc. up to a ""mash"" of food and other human waste in everyday life). As far as such types of waste as wood, paper, cellophane, plastic, etc. are concerned, it is principally possible to build self-sustaining processing industries for their utilization. Metal and glass are easily separated from the total mass of garbage and do not participate in pyrolysis. According to the authors, a “mash” with indefinite composition of substances, can never serve as a source for building payback production system. It can be subjected to technological processing at installations of fast pyrolysis for utilization purpose, but, because of its uncertain composition, it cannot serve as a source for constructing any payback production system. Its disposal is a social task - always subsidized. Such processing will result in reducing, by one order greater or even more, the final volumes of human waste burial! This is a global problem”. It should be noted, however, that applying slow pyrolysis to food waste can turn it into full-value raw product, especially in combination with other kinds of waste (see 1.5. Pyrolysis of skin and food waste).
In addition, according to (26, Section “A few words about the possibility of applying rapid pyrolysis technology to automobile tires and rubber”), there are heavy metals and accumulated radioactivity in MSW, which will inevitably affect the output of the pyrolysis product. This problem is poorly researched and therefore causes concern. Detailed studies in this area are required - this is a social problem!” More recent studies have shown that “whole oils of fast pyrolysis have a mutagenic effect — the ability to cause damage to the hereditary apparatus of cells (genes, chromosomes) of various tissues, manifested in a change in the genotype of their offspring. At the same time, the pyrolysis oil obtained during slow pyrolysis does not contain polycyclic aromatic compounds and, apparently, is not carcinogenic. The practice of distilling wood to extract pyrolysis fluids has existed for more than 100 years, but no toxicological damage or health hazard was observed ” (27, Section 4.7, “ Health and safety”).
The recent years have seen successive operations of Pyrolysis Network (PyNe), the world pyrolysis network, part of the unified organization ThennalNet, created with funds from the European Commission and specializing in accumulating and synthesizing data on thermal processes of biomass processing. PyNe brings together researchers of rapid pyrolysis process in various countries. At present PyNe includes 15 European countries, as well as the USA and Canada. The PyNe network has created a unified data base in the field of rapid pyrolysis technology development, and it also has its own journal. Active research is currently underway, aimed at improving reactor designs and optimizing conditions for conducting pyrolysis (28). However, practical implementation of developing remains at an early stage, and these technologies have not been yet sufficiently developed, in order to compete with implementation in the power sector of traditional fossil fuels, because they undergo some technical and economic problems (29). Nevertheless, the countries that are particularly in need of fuel have come to the conclusion that it is necessary to create a new biopower that could use as raw materials “energy” forest plantations of fast growing trees and bushes, corn or sunflower stalks, waste from woodworking industry, etc.
This requires the use of significant areas of agricultural land. Since rapid pyrolysis makes it possible to use the entire biomass, and slow pyrolysis - only one of its parts, the Institute of Technical Thermal Physics of the Ukraine National Academy of Sciences suggested to obtain combustible gas and charcoal from this raw material by means of rapid pyrolysis. Such a decision is not only energetically and environmentally sound, but is also economically justified, since it will allow to preserve a significant amount of croplands for growing food (39). However, as it was shown above, the rapid pyrolysis technology can be successfully used for biomass processing, and is not at all applicable for unsorted MSW, at least at the current stage of technological development.
RusEkoEnergo (Moscow-Skolkovo, Russia), a scientific-engineering company (30), offers a pyrolysis-plasma technology and installation of a plant with the capacity of 100 kg/hour for processing any organic raw materials and waste, in the following steps:
• Reception of raw materials, such as household solid waste, (both newly formed and kept in landfill storage), wood and other waste.
• Separation of solid raw materials (separation of the nonorganic component), primary crushing and subsequent grinding of fractions up to 5-10 mm.
• Saturation of raw pulp with catalysts and neutralizers, drying with exhaust gases of internal combustion engines (ICE) at 120њC.
• Pyrolysis of the prepared raw materials, in order to obtain methane-containing fuel gas in the upper zone of the plasma reactor at a temperature of 450-500њC.
• High-temperature conversion (decomposition) of the coke-ash residue in 2 levels at temperatures of 1200-1400 њу and 1600 њу.
• Mineralization (vitrification) of the ash fraction in the composition of oxides, carbides, salts, etc.
• quench hardening of the vapor-gas mixture, subsequent cleaning of all gas flows (reduced fuel gas and waste gases of power units).
• Generation of heat and power resources in adapted gas piston power units.
• Reagent-filtration treatment of water flows for their discharge to the relief or to treatment facilities, with partial return of water to the technology.
• Production of construction or road-building materials.
The resulting gas fuel is to be used in adapted gas-piston power units for generation of thermal energy resources. Gas and sewage water cleaning plants will also be constructed, as well as a complex management system and equipment for producing environmentally friendly construction and road-building materials, including aerated concrete (30).
At the same time, a project has been developed for construction of a mobile waste-processing complex – a Mini-TPP with electrical output of 4 Megawatt, based on plasma-hydrogen gasification. The annual volume of waste processing is to be 50,000 tons of any types of prepared waste. The total investment volume is to be about ,000,000.00. At the same time, an optimal reactor design has been developed, which is a vertical shaft furnace with upper side loading of dried waste through the sluice channel, 2-tier arrangement of plasma heaters (plasma facilities) in the lower chamber, with removal of gaseous products from the upper part of the reactor, and molten slag output (melt matrix) from the bottom area through the locking unit, with further cooling and vitrification. This high-temperature plasma technology for processing carbon-containing waste is based on using a small part of air and active water vapor as an oxidizer at the temperature in the reaction zone being above 1600њC (31).
A significant advantage of the plasma method, in comparison with high-temperature firing methods for incineration of solid waste, is ecological purity of the technology: it excludes occurrence of harmful emissions like dioxins or furans. The temperature level above 1300њу allows decomposing all complex substances into simplest ones, subsequent rapid quenching of chemical reactions prevents reverse connections. Another advantage is that plasma technology does not require sorting of MSW: all kinds of organic waste are destroyed in a single plasma-shaft furnace (32). The resulting liquid slag (as a fusible matrix), is vitrified when cooled, and, according to the authors, does not contain harmful substances (mainly heavy metals), is neutral to soil, to water, and to the environment, and can be used in construction of roads, houses, etc. (30, 31). Experts from ""VNIISTROMKOMPOSIT"" (Krasnoyarsk, Russia) hold the same opinion, and believe that “vitrified MSW pyrolysis slags are insoluble in water and sufficiently stable in alkalies and weak acids; some impurities (traces of micro elements of heavy metals and dioxins) were found in crystal matrices of all established minerals ” (32, p.59, 62, see 1.8. Heavy metals). Currently, an improved eco-concreting method has been developed – integral mineral-matrix technology (IMM-technology) which ensures the environmental safety of the obtained material due to “rational selection of components of interacting systems and chemical binding of pollutants (for example, heavy metals and dioxins), up to their inclusion into the crystalline lattice of cementing neoplasms, or blocking pollutants by colloid-dispersed and sol-helium phases in the mass of the forming material."" However, as the authors indicate in the same papers, this is only possible “with rationally selected components of the system, when the potential chemical properties of the components of the system and their mechanical characteristics are summed up” (33, 34). On the industrial scale, such a condition can hardly be fulfilled, since the composition of municipal garbage and, consequently, of slag is not constant. Hence, a kind of “encapsulation” of toxic substances in vitrified MSW slags is not always possible, and, accordingly, under certain conditions (for example, if further use presupposes mechanical processing – crushing, grinding, etc.), toxic metals can be separated from grinded slag, especially under rains (36, Section VI. Toxicity of slags and fly ash). Besides, three metals, Cadmium, Mercury and Zinc, turn into the gaseous state at temperature reaching 1000њC, become volatile and then turn into combustion products, entering the environment (if, of course, expensive flue gas purification from heavy metals is not provided for) (33).
Operation of a gas-driven electrical unit on a low-calorie gas (compared to operation on natural gas) is accompanied by a capacity decrease by 20 to 45%, due to low volumetric energy content of the gas-air mixture and specific features of CO and Hydrogen combustion, its main combustible components. Reducing the amount of Nitrogen in the synthetic gas increases the amount of resources produced by the power unit. However, the cost of the Nitrogen-Oxygen unit required for producing Oxygen-enriched air, along with its considerable energy consumption, does not allow to use this process (31). In addition, gas fuel, unlike liquid fuel, is difficult to transport and therefore, as a rule, is used directly at its extraction site for production of heat and electrical power, which is not always economically feasible (38).
To date, plasma technologies for processing solid household waste have not found wide application, because there are no reliable arc plasma torches with a sufficient resource of continuous operation. Among other drawbacks of plasma technology, it is necessary to mention high power consumption (processing of one ton of MSW requires 500 kWh of electricity), high operating costs for maintaining plasma torches and repairing the reactor. In addition, a negative factor – a high noise level (up to 120-130dB) – was discovered when a plasma torch was in the operation mode. Implementation of plasma torches imposes special requirements on organization of labor safety. The world has not seen yet any streamlined production of large installations based on the plasma method. The domestic waste recycling plant in Canada is in the “commissioning” stage. The only industrially implemented development of plasma gasification of waste is a replica of the Kurchatov Institute presented as an installation for 500 kg of MSW per hour in the city of Haifa (Israel). However, its cost was about million, so the project did not receive further development. Promotion to the market of electro plasma innovation technologies requires scientific support for pilot production and their commercialization. Consequently, at the stage of developing the design capacity, effective mechanisms of State support of investors should be developed (32).
Some companies are switching from simple incineration to a two-stage process, including the pyrolysis stage followed by burning. Such a process is energetically more profitable than simple incineration and is also suitable for the treatment of composted waste. Pyrolysis produces gas and a solid pyrolysis residue. Then the one and the other products immediately, without any additional processing, are sent to the furnace for combustion to maintain the process. Part of the pyrolysis gases after condensation can be removed from the system and used as liquid fuel by other consumers. At the same time, however, the same disadvantages are observed as with direct waste incineration. In the same cases when the pyrolysis gas is purified from hydrogen chloride, sulfur compounds, heavy metals, etc., the process becomes as expensive as with direct combustion. Therefore, now on an industrial scale, this technology is no longer advancing and, compared with incineration, make up only a small part of the total volume of solid waste processing.
Thus, even the most modern technologies do not provide cost-effective, sustainable, environmentally friendly processing of solid municipal waste. And none of the existing technologies provides for purification of these wastes from heavy metals in the manufacturing process, even more so without pollution by heavy metals of the environment.
In this regard, the “Technological Regulations” propose to use thermochemical processing of municipal waste, with low-temperature (500њC) slow pyrolysis and simultaneous neutralization and removal from the process of polluting and hazardous components of municipal solid waste (MSW). Continuation ->Part 2 >>
Recycling plastics waste
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