Large-Scale Complex Processing of Solid Carbonaceous Industrial and Domestic Wastes
A.G.Melnichenko
"Coke and chemistry" Number 5 2001.allerton press,inc.//New York
The problem of
solid industrial and household wastes is one of the most urgent and difficultly
solvable present-day problems because of the enormous and ever increasing
quantities of wastes and a large diversity of their properties. Unless this
problem is solved in the first decade of the 21st century, the consequences may
become catastrophic.
The problem
is very critical in Ukraine, especially in the., thickly populated industrial
Donbass. Since industrial and domestic wastes are not processed on a large
scale, the fertile land is used as dumping ground (today more than 30,000 ha out
of 170,000 in Ukraine), this being responsible for the ever increasing pollution
of water bodies and air with toxic substances.
The complex scientific and
engineering problems that are to be solved are, in our opinion, weighty factors
hindering the development of efficient methods and equipment for the processing
of solid wastes. This is largely associated with the instability of the
feedstock base. The physico-mechanical properties of the majority of solid
industrial and domestic wastes and the regularities of the change of their
properties have been studied little. The existing information is incomplete and
has not been systematized. The development of the equipment for the processing
of such materials is objectively a very complicated task. No large plants have
been built so far for the complex processing of industrial and domestic wastes.
Very limited amounts of neutral or slightly toxic wastes are selectively
processed, which is why the ecological effect of such processing is
insignificant.
The well-known
technologies of combustion or processing of solid wastes are used for some types
of wastes and are expensive and imperfect since they give rise to new problems
or are not suitable at all for Ukraine for reasons of economical, ecological and
social character. It is important that more than half of all types of solid
industrial and domestic wastes in Donbass are carbonaceous and contain organic
matter, which is the raw material for chemical processing or is used as fuel.
The ash components of such wastes can be used in the manufacture of building
materials. An even greater amount of organic matter is contained in domestic
wastes. However, only one-tenth of the resources of industrial and domestic
wastes is used; domestic wastes are used in much smaller quantities.
The workers of Donetsk
Technological University are concerned with the development of the equipment and
technology for complex processing of solid carbonaceous wastes (SCW) of
industrial and domestic origin on the basis of the processes of thermal
degradation and synthesis of the organic matter of wastes in inclined
thermolysis furnaces (ITF) with the manufacture of useful products and energy.
Laboratory studies of "compound-mixes of solid industrial and domestic wastes
have demonstrated wide possibilities of the new technology for the initial
composition of the raw material.
On the basis of the summarizing of
the world experience in the processing of solid carbonaceous industrial and
domestic wastes and of the analysis of the present-day state and importance of
this problem in Ukraine and other countries and of the results of investigations
carried out in Donetsk Technological University, the following conceptual
considerations were taken into account in the development of the given
technology.
1. The technology is
based on the thermolysis of the organic matter of wastes. This is the main stage
of processing, which proceeds in sealed chambers of ITF and which is the
controlled process of thermal degradation of the raw material with the formation
of solid thermolysis fuel and a mixture of volatiles in the form of vapor-gas
and liquid hydrocarbon products.
2. The complex character of
processing and compounding of waste mixtures. This implies the joint processing
of a wide gamut of mixtures of hydrocarbon industrial and domestic wastes. The
solid and liquid components of wastes in various proportions, depending on their
physical properties and chemical composition, are mixed at the stage of
preparation of the raw material in order to obtain compound mixtures of required
quality.
3. The large scale of
industrial installations. The volumes of accumulation and generation of
industrial and domestic wastes are so enormous that it becomes necessary to
build high-capacity installations and to involve, in the sphere of processing,
the infrastructure of industries, primarily byproduct coke plants.
4. The controllability and
flexibility of the process. This is achieved due to the possibility of the joint
application of several controlling factors: the temperature regime of
thermolysis, the pressure of the preliminary compaction of the raw material, the
cyclic charging, the flow velocity of the working mass in installations, etc.
Optimal control is effected on the basis of a knowledge of the properties of the
feed and of the demands for the products and energy obtained with the use of
computers, automation facilities and controlling functions of the personnel.
5. The high level of technogenic
safety. The industrial complex is designed for a higher level of requirements
for the sealing of technological apparatuses as compared with those existing in
the industry, entrapment and complete decontamination and chemical processing of
all thermolysis products. Use should be made of tested technological and
designing measures capable of creating prerequisites for efficient environmental
protection.
6. The high degree of
utilization of the energy-chemical potential of wastes. This is achieved by the
development of a complete cycle of thorough processing of waste mixtures with
the manufacture of useful products and energy, namely thermolysis gas, liquid
hydrocarbons, solid fuel, electric power and building materials.
7. The economic efficiency. With
relatively low capital costs the process can be made economically profitable due
the use of cheap organic materials of various origin with the manufacture of
useful products, the protection of soil, water and air from contamination, the
elimination of refuse piles, dumps, sludge and slime pits, settling tanks, and
also of the infrastructure of byproduct coke plants.
8. The social effect. The
involvement of the personnel and basic facilities of byproduct coke plants,
which cut down production and the building of equipment, machines, installations
and structure of the industrial complex in the processing of wastes in
machine-building and refractory plants contributes to the creation of jobs for
the unemployed.