CC BY
35
UDC 532.527
R. R. Usmanova, G. E. Zaikov
TECHNICAL AND ECOLOGICAL JUSTIFICATION OF THE CHOICE
GAS PURIFICATION SYSTEMS
Keywords: Ecological efficiency; The Ecological damage; Atmospheric emissions; The Rotoklon; Criterion of efficiency; Maximum
permissible concentration
Developed criteria for technical and economic effectiveness systems protect the environment. On the basis of these criteria, obtain relations for the calculation of damage caused to the environment by atmospheric emissions production. A method for estimating gas treatment facilities, which allows at the design stage to make a comparative analysis of competing systems, taking into account the costs of implementation of environmental measures.
Ключевые слова: экологическая эффективность; экологический ущерб; атмосферные выбросы; ротоклон; критерий
эффективности; предельно допустимые концентрации.
Разработаны критерии технико-экономической эффективности системы защиты окружающей среды. На основе разработанных критериев получены соотношения для расчета ущерба, наносимого окружающей среде атмосферными выбросами производства. Предложен метод оценки газоочистных сооружений, позволяющий на стадии проектирования произвести сравнительный анализ конкурирующих систем с учетом затрат на реализацию природоохранных мероприятий.
1. Current state of a problem
Optimisation problem it is close, it is connected with various alternatives of designs, characteristic for designing a gas-cleaning installation of constructions. The survey of the domestic and foreign literature [1, 3, 5] has revealed a total absence of attempts of the solution of a problem of optimisation in the stated aspect. Moreover, it is not revealed attempts to optimise is constructive-technological parameters of any unique apparatus within the limits of its use in concrete conditions.
Preliminary studying of a problem has shown its complexity. The way to its solution as it is installed, passes through construction in the mathematical form of technical and economic models of optimised installations, i.e. The equations in which is constructive-technological and technical and economic parameters would be connected together. Now such model exists only with reference to cyclonic installations [1, 8].
The special attention is given preparation and the analysis of technical projects on designing as as shows experiment, bases of quality of the design are put at these early stages of work.
It is possible to note the momentous defects, to overcome which it is necessary the proximal years.
1. Insufficiency of the nomenclature a gas-cleaning installation and its lag from growing powers of the industry.
2. Weakness of computational baseline in which predominates empiric.
3. Absence of strict scientific criteria for designing a gas-cleaning installation of constructions with number of steps of clearing two and more. For the specified reason at designing of such constructions the big role is played by purely heuristic factor.
4. The weakest and improbable working out of the questions connected with drawing by the flying emissions of a damage to a circumambient and, accordingly, with definition of economic benefit of liquidation of this damage.
These and other unresolved problems should be solved to the development engineers, initiating to master designing a gas-cleaning installation of constructions. Central tasks which were put by working out of a new build of a rotoklon with inner circulation of a liquid:
• to produce criteria of a technical and economic estimation of a system effectiveness of environment protection against pollution;
• to create the apparatus with a wide range of change of operating conditions and a wide scope, including for clearing of gases of the basic industrial assemblies of a finely divided dust.
2. Calculation of the prevented damage from atmospheric air pollution
The prevented ecological damage from pollutant emissions in an atmosphere - an estimation in the monetary form of possibly negative after effects from pollutant emissions which in an observed time span it was possible to avoid as a result of activity of supervising authorities in metrology, conducting of a complex of provisions, implementation of nature protection programs. At implementation a gas-cleaning installation was momentous to define magnitude of an economic damage in the set region, prevented as a result of conducting of nature protection provisions on air protection from pollutant emissions [2, 5].
The integrated estimation of magnitude of the prevented damage from pollutant emissions can be spent to an aerosphere as for one large source or group of sources, and for region as a whole. In the capacity of sized up group of sources all sources in the given city, the region, observed as a uniform source can be observed.
The prevented economic damage from pollutant emissions in a free air Ур, thousand rbl / year in observed economic region Russian Federation for a time span is defined by formula [7]:
yp=yy'MpKe-iM,
where yy -a parameter of a specific damage from pollutant emissions in a free air in observed economic region Russian Federation, Russian rouble / ton.
Ke - factor of an ecological situation and the ecological significance of a condition of a free air of territories of economic region of Russia
Id - an index on the industries, installed by Ministry of economics of Russia. We accept equal 1;
Mp - a pollutant emission reduced mass in the region, scaled down as a result of conducting of matching nature protection provisions, thousand tons / year.
Kei - factor of relative ecological-economic hazard to i th pollutant.
N - quantity of considered pollutants.
Mp =AM - Mcn
AM = M1 -M 2 +Mnm
where A M - Total volume of a reduced mass of the scaled down waste interception, thousand conditional, tons / year;
M c - a reduced mass of the waste interception which has been scaled down as a result of slump in production in region, thousand conditional, tons / year;
M1 and M2 - accordingly a waste interception reduced mass on the beginning and the end of the desing period, thousand conditional, tons / year;
Mnew - a reduced mass of waste interception of the new factories and manufactures, thousand conditional, tons / year.
For calculation of a reduced mass of pollution the confirmed values of maximum-permissible concentration (maximum concentration limit) of pollutants in water of ponds are used. By means of maximum concentration limit factors of ecological and economic hazard of pollutants as magnitude, return maximum concentration limit are defined: where Kei = 1/M C L.
The reduced mass of pollutants pays off by formula:
M = f>i • k,
1=1
where mi - mass of actual waste interception of pollutant in water installations of observed region, tons / year;
Kei - factor of relative ecological-economic hazard to pollutant;
N - quantity of considered pollutants. i - Substance number in the table.
3. Technical and ecological assessment gas-cleaning plant sampling
In ecology and harmonious exploitation bases estimations of economic efficiency of nature protection provisions are resulted. The problem is put to inject into calculation of a damage to a circumambient y operational parameters of the given clearing installation to pass to relative magnitudes. It will allow to scale down number of the factors which are not influencing functioning of system, to devise methods of calculation of relative efficiency a gas-cleaning installation of the constructions, giving the chance to choose the most rational approaches and the equipment of systems of trapping of harmful making atmospheric emissions. In the most general event, the damage A, caused by atmospheric emissions can be
computed as y=BM. The Reduced mass of emission incorporating N of components, will be computed in an aspect:
mi
The emission mass mi is proportional to an overshoot through system
m, =(1-^.)./770/ In an industrial practice it is normally set or the share of concrete pollution in departing gas is known, coi. We will consider gas diluted enough so its density p does not depend on presence of admixtures
/"oi =^oi p Q.
Let's compute a damage caused to an aerosphere, per unit masses of trapped pollution ym
B-^A i .(1 -m )-C o i
i=i_
N
Y- Coi
(1)
If to size up the gas-cleaning plant on average parameters, — = q
i N a=—- Ya - °o i
N ^=1 i oi B^A-(1 -q)
J m
q
Let's formulate a principle of ecological efficiency of nature protection provisions at least a damage put to a circumambient. Purpose function in this case will appear in the form of ym ^ min. Magnitude ym diminishes with value growth
Y-i -Co
E = -
(2)
B-Y Ai-(1 -q )Ci
Magnitude E we will consider as criterion of ecological efficiency of nature protection provisions. The criterion of relative ecological efficiency & is representable in the form of the relation of values E computed for compared alternative E1 and the base accepted in the capacity of e0
& = E1 / E0.
In case of the single-component pollution of criterion of relative ecological efficiency we will find as
-1 1 --o . (3)
-o 1
Thus, for two gas-cleaning plants of the concrete manufacture, different in separation extent, q1 #q0, relative ecological efficiency of system is sized up by technological parameter &^max. The prevented damage yp compute as a difference between economic losses of two competing alternatives as yp= y0 - y1
We will be restricted to an event of comparison of two alternatives of the clearing of gas emissions intended for the same manufacture with fixed level of technological perfection. In the capacity of base alternative y0 we will accept the greatest possible damage atmospheric emissions of the manufacture which technological circuit design does not provide a clearing stage, qi0 = 0. For the fixed technological circuit design of manufacture efficiency of a stage of clearing we will size up in shares from the maximum damage En= yp / yo
=1
En
y
y o
E A -C„-k
J=1_
N
EAi ■ CH1
(4)
If to consider that all components of harmful emission with aggression average indexes are trapped in equal extents (At = A, j = rj we come to En. = j. Thus, the widespread extent of trapping r is a special case of criterion of ecological efficiency en. computed for one-parametric pollution or for emission with average characteristics. At sampling of the gas-cleaning plant it is necessary to give preference to the installation securing higher values of criterion en.
The gas-cleaning installation demands expenses Z (rbl./Year) on the creation and functioning. These charges can essentially differ depending on the accepted method of clearing of gas emissions and should be taken into consideration at an estimation of the general damage. For example, air purification from a dust cyclone separators will be more low-cost in the "dry" way "wet" at which it is necessary to provide additional charges on water, pumping devices, neutralisation of runoffs etc. At the same time centrifugal separators are not suitable for clearing of gaseous impurities. We will use relative parameters, i.e. to consider a gain of the prevented damage Ayp = y1 - y2 on rouble of expenses Az.
Function of the purpose yp — max will register in an aspect
en=(Ayn /A Z ) — max.
We will be restricted to consideration of a method of calculation of magnitude yp for centrifugal dust traps widely used in practice. We will define in maintenance costs a variable component of the power inputs connected with a water resistance of the apparatus AP( Pascal). The Head loss AH = AP/p (J/kg) is definable from the Bernoulli's theorem which has been written down for entrance and target cross-sections of the gas passage. The energy consumption will be computed as I = AP ■ Q (J/s).
Power inputs z3 in terms of energy costs Ce (Russian rouble/J) is definable from a relationship z3 = ce ■ q■ap
The prevented damage yp computed on rouble of expenses we will find as
B■P-EAi ■ CoiK
En =-
(5)
C3 -AP
The criterion of relative ecological efficiency of the whirlwind apparatus 0n =En1 / en0, is computed on values En for two installations enl and en0, from which one is accepted for base en0. At transition to average magnitudes
© = AP°- K . (6)
11 AP, -K
Let's apply the results received earlier according to efficiency of clearing of gas emissions to the comparative analysis of dust extractors of centrifugal action by criterion 0. As the base two-stage installation of type «cyclone C-6» is accepted [9]. Results of the comparative analysis are introduced in table 1. As show the introduced data, criterion relational technical and ecological to efficiency 0 reflects logic of process of dust separation -
the above a device purification efficiency r, the magnitude & is more. In this case instead of qualitative ascertaining of the fact the quantitative assessment of efficiency of the clearing of gas emissions is offered, allowing to define in what degree competing systems differ from each other.
Table 1 - Comparative technical and economic indicators of offered and base dust-collecting plants
The indicator name Basic hardware New installation
Productivity, m3/s 6 6
Hydraulic resistance, Pascal 2100 1350
Factor of hydraulic resistance 10,8 6,9
Concentration of emissions after installation, Mg/m3 127,5 39
The occupied space in the plan, m2 17 5,3
Metal consumption m2 6,8 4,9
The general power consumption, kilowatt-h 30 31
The specific expense of the electric power on clearing 1000 m3 emissions, kilowatt-h 0,6 0,475
Intensity of flow, kg/h - 0,5
Criterion of efficiency, 0 1,0 1,85
On fig. 1 results of researches of separating ability of a rotoklon depending on conditional speed of gas vy, calculated on full section of the device are introduced. Comparison of considered devices by means of criterion relative technical and economic efficiency 6 is spent.
0
1.6
1.4
1.2
1,0
o.e
* • /
s{ f
/ *
* * /
/
10
20
30
40 u ,mps
Fig. 1 - Relative technical and economic efficiency of a rotoklon
The cited data has illustrative character and shows possibilities of application of criteria of technical and economic efficiency 6 for comparison purposes gas-cleaning plant devices.
4. Results of industrial tests of the gas-cleaning plant on the basis of device "rotoklon"
Let's consider system of wet clearing of the gases departing from the closed ferroalloy furnace 1. On this
furnace comparative researches of the described system of wet dust separation (fig. 2 see) have been conducted [10].
The slope breeching 2, actually is the hollow scrubber in diameter of 400 mm working in the evaporation cooling regime. At work gases arrive from it in a Venturi scrubber 3, consisting of two cylindrical columns in diameter of 1000 mm with the general bunker. In each column of a scrubber it is established on three atomizers. The Venturi scrubber of the first step of clearing has a mouth in diameter of 100 mm and is irrigated with water from an atomizer established in front of the confusor.
Gases after a slope breeching go at first to the bunker the drop catcher 4, and then in a rotoclon [4] of the another step which consists from inertial a heat - and a mist eliminator 7. The exhaust of gases from the furnace is carried out by vacuum pump VVN-50 established behind devices of clearing of gas emissions. Purified gases are deduced in atmosphere.
Regulation of pressure of gases under a furnace roof and the expense of gases is carried out by a throttle in front of the vacuum pump. Slurry water from devices of clearing of gas emissions flows off a by gravity in a tank of a hydroshutter 9, whence also a by gravity arrives in a slurry tank. From a slurry tank water on two slurry clarifier is taken away on water purification. After clarification, chemical processing and cooling water is fed again by the pump on irrigating of gas-cleaning installations.
The dust containing in gases, differs high dispersion (to 80 weight. % of particles less than 5-6 microns) [13]. In table 2 the compound of a dust of exhaust gases is resulted.
In tests for furnaces almost constant electric regime that secured with identity of conditions at which parameters of systems of dust separation characterize was supported. The furnace worked on the fifth - the seventh steps of pressure at fluctuations of capacity 14,5^17,5 megawatt.
1 - baking oven; 2 - gas exit branch; 3 - Venturi scrubber; 4 - bunker - the drop catcher; 5 - a rotoklon; 6 - gas pipeline; 7 - inertial heat - and a mist eliminator; 8 - exhaust pipe; 9 - tank - a hydraulic hitch.
Fig. 2 - The scheme of clearing of flue gas with gas cooling in a Venturi scrubber and the subsequent clearing in a rotoklon
The quantity of dry gases departing from the furnace made 1500 2000 m3/h. The temperature of gases before clearing of gas emissions equaled 750 850 °C and humidity did not exceed 4^5 % (on volume).
Table 2 - Results of posttest examination
Compound Requisite concentration, g/m3 Concentration after clearing, g/m3
Dust 0,02 0,00355
no2 0,10 0,024
SO2 0,03 0,0005
CO 0,01 0,0019
In table 3 results of calculation of a payment for pollutant emission of system of dust separation are shown.
Table 3 - Results of calculation of a payment for pollutant emission
The list of pollutants (the substance name) It is thrown out for the accounting period, t/year The base specification of a payment within admissible specifications, a Russian rouble/t The size of a payment for a maximum permissible emission, Russian rouble/year The base specification of a payment within the established limits, a Russian rouble/t Total a payment on the enterprise, a Russian rouble/year
In total Including
VPE MPE
The inorganic Dust 19 710 — 21 228,65 105 228,65
nitrogen dioxide 105,1 — 52 379,19 260 379,19
carbon monoxide 288,2 — 0,6 2,99 3 2,99
Sulfurs dioxide 197,1 — 40 539,14 200 539,14
Total: 1149,97 1149,97
Thus, we have chosen the scheme of clearing of gases which allows to lower concentration of pollutants to preset values and consequently, and to lower payments by the enterprise for emissions.
Conclusions
1. On the basis of a method of an estimation of economic efficiency of the carried out nature protection actions parities for calculation of the damage put to environment by atmospheric emissions of manufacture
are received. Transition to relative indicators has allowed to scale down number of the factors which are not influencing process of clearing of gas emissions
2. Methods of an estimation a gas-cleaning installation of the constructions are devised, allowing on a design stage to make the comparative analysis of competing systems in terms of expenses for realisation of nature protection actions
3. Criteria of an estimation technical and ecological the gas-cleaning plants, incorporating both economic, and technology factors are developed.
References
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© R.R. Usmanova - She is currently Associate Professor of the Chair of Strength of Materials at the Ufa State Technical University of Aviation in Ufa, Bashkortostan, Russia, [email protected]; G. E. Zaikov - DSc, Professor of the Chair Plastics Technology Kazan National Research Technological University in Kazan, Tatarstan, Russia, [email protected].
© Р. Р. Усманова - канд. техн. наук, доц. каф. СМ Уфимского госуд. авиационного технич. ун-та, [email protected]; Г. Е. Заиков - д-р хим. наук, проф. каф. ТПМ КНИТУ, [email protected].
