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Abstract

When writing this essay, the master's work has not yet been completed. Final completion: May 2021. The full text of the work and materials on the topic can be obtained from the author or his manager after that date.

Content

Introduction

The competent use and disposal of the generated municipal solid waste (MSW) is one of the most important environmental issues on the agenda for countries around the world.

World experience shows that economic growth, population growth and urbanization lead to an increase in the generation of waste in the world, moreover, not at a proportional rate.

MSW (fig. 1) is a heterogeneous mixture, the individual components of which can act as a high-calorific fuel that is not inferior to brown coal in terms of heat engineering characteristics.

Solid household waste disposed of at the landfill

Figure 1 – Solid household waste disposed of at the landfill

Almost the entire volume of waste that is not involved in re-production is disposed of at solid waste landfills, authorized and unauthorized dumps.

With the aim of protecting water resources, atmospheric air, soil, as well as utilizing valuable components contained in waste, various industrial technologies for neutralizing and processing waste are being developed and implemented, including methods of thermal and biothermal disposal and other technological methods for their processing.

1. Relevance of the topic

Today the topic of handling solid waste and industrial waste is economically and environmentally relevant.

The accumulation and untimely removal of waste creates an environmental hazard to the health of the population due to the content in them of a large amount of organic substances, which, when decomposed, form harmful chemical compounds.

The choice of the topic is due to the aggravation of economic, environmental and social problems due to an increase in the volume of produced and disposed solid waste and industrial waste, the need to find and implement more advanced, environmentally and economically sound production facilities for waste disposal.

2. Goals and objectives of the study

The purpose of the work is to study and assess the effect of still bottoms from coke plants on the mechanical properties of a briquette based on solid domestic waste components.

To achieve this goal, the following tasks were set:

  1. to analyze the current situation in the field of solid waste and coke plant waste management;
  2. to determine the physicochemical and thermal technical characteristics of fuel briquettes;
  3. planning an experiment when searching for optimal pressing conditions;
  4. search for a mathematical relationship that will help determine the optimal composition of the fuel mixture based on the ratio of its components;
  5. to form a general view of the technological scheme of the fuel briquette manufacturing process;
  6. to calculate the emissions from the combustion of the briquetted mixture, based on the components of solid waste and still bottoms.

Research object:is the process of joint secondary processing of components of solid household waste and waste of the coke-chemical industry.

Research subject: is the mechanical properties of a fuel briquette obtained on the basis of components of solid household waste and resinous waste of coke plants.

3. The main part

3.1 Global trends in the field of solid waste management

As the world experience of advanced industrial countries shows [1], the justification for the introduction of one or another technology for the processing of solid waste and their components necessarily requires studies of their composition, on which the main technical and economic indicators depend – the morphological composition of household waste.

The highly developed countries of Europe are moving away from the practice of incineration of household waste, replacing this method with modern resource and energy saving technologies, alternative energy sources and the reuse of raw materials, which acts as a method of saving resources and preserving the environment [2].

Modern thermal processes are environmentally friendly in the heat treatment of prepared solid waste, subject to technological standards and using modern gas cleaning methods.

The efficiency of the thermal processing of solid waste is determined by the composition of the waste, the process technology, the degree of preparation of waste for incineration and stabilization of their composition, the process mode, and the process automation technology [3].

The main trend in the development of waste incineration is the transition from direct incineration of solid waste to optimized incineration of the combustible (fuel) fraction separated from the solid waste and the transition from incineration as a process of elimination of solid waste to incineration as a process that provides, along with waste neutralization, the production of heat and electricity [3].

Table 1 shows the mass fractions of waste components by the composition of solid waste, which are of interest as a source of secondary fuel production [4].

Table 1 – Indicators of waste fractions in solid waste

Indicators of waste fractions in solid waste

Thus, it is possible to consider a significant part of household waste as a source of secondary fuel.

3.2 Obtaining secondary fuels based on MSW components

One of the promising methods of thermal utilization of solid waste is the production of Refuse Derived Fuel (RDF) – solid secondary fuel produced by sorting, crushing and dehydrating municipal solid waste, the characteristics of which are determined in accordance with current standards or technical specifications for fuel production.

Every year the intensity of using this method of solid waste disposal in the European Union (EU) and the USA (USA) is increasing every year (fig. 2) [6].

Statistics of RDF production abroad

Figure 2 – Statistics of RDF production abroad (EU, USA)
(animation: 6 frames, 10 cycles of repeating, 42,7 kilobytes)

In addition to MSW waste, our region generates significant volumes of waste from coke plants (CCP), some types of which can be considered as potential heating additives for fuel briquettes.

Abroad, distillation residues of rectification are subjected to pyrolysis in the presence of water vapor and hydrogen, followed by catalytic dehydrogenation of gaseous pyrolysis products.

4. Main research and results

When assessing the properties and quality of fuel briquettes, the results of technical analysis are used. A complete technical analysis is not always carried out; it is often sufficient to carry out a shortened technical analysis, consisting in determining the moisture content, ash content and the yield of volatile substances [9].

As a binder additive to the fuel mixture, the still residues of the coke oven plant are added, while the heat of combustion of the briquette will be higher than that of coal. In the analysis, the value of the distillation residues varied from 0 to 20%, and the content of paper and wood residues was determined as 50:50% of the mixture minus the percentage of distillation residues.

In the course of the work, an important point was the choice of the percentage ratio of MSW components and still bottoms in the mixtures.

When carrying out an optimization experiment for data processing, the Statistika 12 program [10] was used, in which a fuel mixture consisting of paper, wood and distillation residues was studied.

One of the tasks was to find the optimal percentage of the components of the briquetted mixture with its acceptable mechanical strength. The data obtained are clearly illustrated in the graph (fig. 3).

Graph of the response surface

Figure 3 - Graph of the response surface

On the graph of the response surface, the minimum and maximum of the response are clearly visible, and it is possible to roughly estimate the relative fractions of the fuel components at which the greatest strength is achieved. To accurately determine these shares, you can use the contour plot (fig. 4).

Contour plot of the response surface

Figure 4 – Contour plot of the response surface

On the graph it is visually easy to determine at what values of paper, wood and still residues acceptable mechanical strength is achieved. The strength index is approximately 12, lies near the proportion of paper 0.25, the proportion of wood 0.45 and the proportion of residual vat 0.25 (paper – 0.266667; wood – 0.466667 and vat residues – 0.266667).

Conclusions

Analysis of literary sources allows us to draw the following conclusions:

  1. At present, the problem of waste, in particular of solid household waste, is very acute in our region, because the amount of waste is increasing every year. Therefore, it is necessary to take measures to find and implement effective technologies for the processing and disposal of solid household waste.
  2. It is expedient to jointly utilize the components of solid waste and waste from coke plants, which can be considered as heating additives.
  3. One of the promising methods of thermal utilization of solid waste is the production of Refuse Derived Fuel (RDF) – solid secondary fuel.
  4. The production of RDF fuel in European countries is increasing every year.
  5. The use of a binder, based on distillation residues, will significantly reduce the cost of briquettes while maintaining their performance.
  6. Application of RDF, on the one hand, solves the problem of utilization of solid waste to obtain alternative fuel, and on the other hand, it helps to reduce the negative impact of landfills on the environment [11].

References

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