ENERGY-SAVING TECHNOLOGY OF
FLUE GASES AND WASTE WATER CLEANING
ABSTRACT
The Energy-Saving Technology (EST) helps both to reduce emission of environmental contaminants
including heat pollution and to raise the Fuel Utilization Efficiency (FUE). The application of
condensation method provides the highest degree of catching the most hazardous highly dispersed
aerosols and dust particles with the size of several micrometers or less. The following description of this
technology includes the various technological systems for energy conservation, the methods of HeatMass Transfer (HMT) evaluation under Adiabatic Evaporation (AE) and Vapor-Gas Mixture (VGM)
condensation, as well as the heat-exchanger designing and the results obtained during the field trial
programs for the pilot plants.
INTRODUCTION
Industries that are the main sources of air pollution (ferrous and non-ferrous metallurgy, production of
construction materials, fossil fuel burning power plants, chemical industry, foundries, transport
engineering, automobile vehicles, etc.) do emit both the greenhouse gasses and the dusts containing
large proportion of highly dispersed fractions. The aerosol particles with the size of several micrometers
are the most hazardous for human health. Furthermore, they influence on the atmospheric processes and
the climate change. To avoid such emission, a big amount of energy is presently consumed in various
purifiers such as Venturi washers, electric filters and the like. Conventional dust collecting apparatuses
(cyclones, scrubbers, etc.) are ineffective in the case of aerosols.
At the same time, a liquid heating is a major consumer of energy. Consumption of hot water for
technological needs, heating and ventilation constitute a major part of the heat load of industrial
enterprises (from 35 to 85 % of their heat balances). The typical low temperature uses of hot water
include pre-heating of boiler feed water or process fluids, space and domestic water heating, swimming
pools, greenhouses, heavy oil and combustion air heating. The utilization of secondary heat resources,
such as waste gases heat, may conserve energy (fuel), thus will decrease heat pollution and diminish a
global warming and climate change as well.
Very often the steam is used as a heating medium for low temperature heating. Its elimination can
enhance the overall efficiency because, in the sense of thermodynamics, to spend the potential of energy
carrier (vapor), which is able to produce mechanical work or/and electricity, is meaningless. At present,
about 75 % of electric energy is generated by heat Power Engineering Stations (PESs) that burn organic
fuel (gas, oil, coal and shale) with Fuel Utilization Efficiency (FUE) of 30-35 %.
The EST was proposed to increase the degree of heat use in various systems with polluted waste gases,
containing COx, SO2, NOx, etc., Komkov [1975, 1976a]. Being a result of long-standing researches
and developments, this technology allows to construct a highly efficient and environmentally clean PES
of any capacity, including small ones based on secondary power resources in various industrial sectors,
such as chemical industry, metallurgy, building and construction materials production, etc. It can
contribute to weaken the menace of global warming, both through conserving energy and reduction of
the environmental pollution, Komkov, 1977a, 1977b, 1977c, 1992, and be useful in ecological revival
of radioactively contaminated areas, Beskrovny and Komkov, 1992. The proposed technological
methods include the use of both traditional standard equipment and not very usual one, such as Heat
Recovery Scrubber (HRS), that utilize heat during a purifying process, Komkov etc., 1988. Here, the
process is organized in a way so that all extra-heat of polluted gases/waters is converted into water vapor
under the condition of AE. Then the saturated VGM enters the surface condenser. Such a transformation
of wet gas cleaning system allows saving waste heat instead of its losing during gas purification as it
was before in the conventional systems. Usually, due to several reasons, the temperature of washing
water in the process of wet cleaning is maintained on the lowest level, mostly equal to the one of the
environment (in summer ≈ 15º C / 68º F). In the new technology, the process temperature has been
recommended to be maintained on the level of AE. Thus, the washing water temperature is equal or
close to the Wet Bulb Temperature (WBT) – tb. The tb depends on initial gas characteristics –
temperature and moisture content. Under the atmospheric pressure the maximum level of WBT is about
tb = 85º C / 185 º F.
When pre-purified VGM is condensed in a surface condenser a final dust cleaning is taking place too. In
the practice of the accustomed installations, using condensation method of gas cleaning, process of
condensation takes place under the direct contact with cooling water, which becomes dirty. Presented in
the new technology, the new element – surface heat-exchanger – is also unusual for a traditional wet gas
purifying systems. It brings new technological opportunities both for cleaning and for waste heat
utilization.
The designing of the condenser includes a process evaluation both on the surface and in the volume
especially on condensation centers such as dust particles. This is accompanied by drops growth, their
enlargement and interception through various mechanisms (coagulation, diffusion, phoresis, turbulence,
etc.). Sometimes a fog formation takes place as well. The phenomenon alters heat and mass transfer
rates from vapor-gas mixture to wall, and hence the performance of the heat-exchanger, but at the same
time it may help drop growth and thus increase cleaning effect of condensation.
Although the wet method is one of the oldest, it continues to be universal one comparatively with other
modern dry methods: it is possible to catch the contaminants of all sorts – solid, liquid and gaseous.
Some of “dry” methods use water to transport caught dust, thus creating a dirty water cycle.
In the new technology, the washing water re-cycling allows cleaning other waste water and combining
both processes in the one unit. The method may also be used in automotive vehicles both to reduce
greenhouse gases emission and to increase the fuel utilization efficiency of engine.
The trials at the pilot plants discovered the possibility of using ordinary carbon steel heat-exchangers as
surface condensers. In long-term experiments under VGM condensation there have been installed
standard finned heat-exchangers usually applied for clean air heating in ventilation systems. The
corrosion rate was not faster than under atmospheric conditions. The explanation of the phenomenon
needs special corrosion experiments.
THE TECHNOLOGICAL SYSTEMS
Industrial Energy Sector
The technology has been used in the operations loops of fuel-burning apparatuses employed in various
industrial branches (chemical industry, metallurgy, building materials production, etc.). The several
examples of the technology realization in using secondary power resources are given on the Figs. 1 - 4.
Fig. 1 is a view of a principal scheme of the installation for heat utilization and the flue gases cleaning
that was put into operational practice after the rock wool-lined furnace in Vilnius, Lithuania, during
1983 – 86, Komkov etc, 1988. The flue gases contained dust, SO2, NOx. The acids were neutralized
with burnt lime. The heated water was used in the ventilation system. There were two options for the
heating of cooling water:
a) in condenser (4) till the temperature
tw = tb – (7 …12)º C
or tw = tb – (44.6 … 53.6) º F
At the pilot plant in Vilnius tw was about 50 … 55º C (323 … 328º K) or 122 …131 º F;
b) in waste heat boiler (economizer) (2) after condenser (4) till thw = 90 ºC (363º K), or 194 º F, and
more. The upper value is limited by flue furnace gas temperature. The economizer surface was exposed
to dust drift.
Fig. 2 is a view of a principal scheme of the further developed installation, Komkov, 1990. The
installation contains scrubber-absorber (1), connected with flushing water tank (2), condenser (3) with a
tray, connected with blast air spray chamber (6). There are evaporating tank (11), additional condenser
(14) and other auxiliary equipment for treatment of waste water till dry remainder.
Those energy-saving industrial installations for cleaning of contaminated flue gases were successfully
tested and put into industrial use at the pilot plants in Ukraine, the foundry of the industrial enterprise
“Veda”, and in Belarus, research foundry of the Belarus Polytechnic Institute, Minsk.
Heat and Electric Power Engineering
Fig. 3 is a view of the principal scheme of the boiler with utilization of waste heat, both gaseous and
liquid, Komkov, 1989. The combination of the shown boiler with other systems, illustrated on Figs. 1,
2, give them the corresponding advantages.
There exists a special opportunity to raise FUE on Power Engineering Stations as it is exposed on Fig. 4,
Komkov, 1976c. The ultimate efficiency makes unnecessary the attainment of high temperature for
transfer mediums heating. Combustion process may be run at the lowest of possible temperatures a big
air excess that is to prevent NOx and CO generation, Komkov, 1993.
The design view of the mid-size industrial Heat Utilizer of Contaminated Gases is presented on Fig. 5.
Here, for the project with the capacity of 10,000 cubic m (35,315 cubic ft) of gases per hour, the
calculated dimensions of the energy saving gas cleaning installation will be 12 ft x 2 ft x 10 ft.
CONCLUSIONS
The Energy-Saving Technology allows to create Power Engineering Stations of various capacities, high
and low, with ultimate efficiency, protect the environment and use the reserves of fuel conservation to
produce heat and electricity with a short pay-off period. The applied methods of Heat-Mass Transfer
evaluation allow designing of the exchangers and the systems of the Energy-Saving Technology.
ABBREVIATIONS
EST – Energy-Saving Technology
tb – Wet Bulb Temperature (WBT), ºC
tw – Warm Water Temperature, ºC
thw – Hot Water Temperature, ºC
AE – Adiabatic Evaporation
WGM – Vapor-Gas Mixture
HTM – Heat-Mass Transfer
HRS – Heat Recovery Scrubber
MTC – Mass Transfer Coefficient
FUE – Fuel Utilization Efficiency
PES – Power Engineering Station
REFERENCES
Komkov, 1975, “The Use of Low Temperature Heat Utilizers for Reduction of Industrial Furnaces
Emission in Atmosphere”, in The Use of Gas in the National Economy (Ispolzovanie Gaza v Narodnom
Khozyaistve), No. 6, pp. 30-33, VNIGasprom Press, Moscow.
Komkov, 1976a, “The Use of Polutted Gases Heat”, in The Industrial Power Engineering
(Promyshlennaya Energetica), No. 2. 1976, pp. 51-52, Moscow.
Komkov, 1976b, “The Investigation of the Steam-Gas Mixture Condensation in Heat Utilizers-Waste
Gas Purifiers”, in The Use of Gas in the National Economy (Ispolzovanie Gaza v Narodnom
Khozyaistve), No. 6, pp. 15-20, VNIGasprom Press, Moscow.
Komkov, 1976c, Patent of Russia No. 785530.
Komkov, 1977a, “The Use of Combined Heat Utilizers / Gas Purifiers (HUGP) for Reducing Emission
of Contaminants and for Fuel Economy” in The Gas Industry and the Environment: Proc. Of
Symposium of the Committee on Gas, ECE, Minsk, Belarus, 1977, published for UN by Pergamon
Press, Oxford, UK, 1978 ISBN 0-08-0224-12-1, pp. 41-44.
Komkov, 1977b, “The Heat Generation Schemes for Use of Secondary Power Resources” in Heat
Supply System Designing: Proc. Of VNIPIENERGOPROM, issue No. 9, pp. 91-93, Moscow, Russia,
1977.
Komkov, 1977c, “The Schemes of Hot Contaminated Gases Use with Application of Condensation
Effect” in The New Achievements in Automobile Industry (Peredovoi opit v avtomobilestroenii), No. 5,
pp. 19-23, 1977, Toljatti, Russia.
Komkov et al, 1988, “The Energy-Resource Saving Technology of Gas Cleaning”, The information
letter of the Ukrainian Academy of Science, published by Reclama Press, 1988, Kiev, Ukraine.
Komkov, 1989, Patent of Russia No. 1621650
Komkov, 1990, Patent of Russia No. 1776907
Komkov, 1992, “The Results of Research, Development and Promoting of the Power-Saving Gas-Water
Cleaning Technology” in The Physical Problems of Ecology, Nature Management and Resources
Conservation: Proc. Of the 1st International Symposium, pp. 97-98, Izhevsk, Russia, 1992.
Beskrovnyi and Komkov, 1992, “ERR Project (Project of Ecological Revival of Regions) Applying
Biomosses and Using Biomass Energetically” ibid, pp. 51-52.
Komkov, 1993, “The Heat Recovery Scrubbers: Results and Perspectives” in Gas Cleaning at High
Temperatures: Proc. of the 2nd International Symp, Guildford, UK, 1993, the Poster Presentation, p.22.
Komkov, 1998, “Experience in Research, Development and Designing, of Heat Exchangers in PowerSaving Technology (PST) of Waste Gas/Water Cleaning” in The Heat Exchangers for Sustainable
Development. Proc. of the International Conf., Lisbon, Portugal, 1998.
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