Waste water in boiler houses and their treatment.
Palamarchuk, Alexander Vasilievich
Academic degree:
PhD
Place of defense of the dissertation:
Novocherkassk
VAK specialty code:
Speciality:
Thermal power plants, their energy systems and units
Number of pages:
Introduction
Chapter 1 Analysis of technological schemes and methods of cooking at thermal power plants and nuclear power plants
1.1 The role and place of the chemical water treatment unit in the thermal schemes of TPPs and NPPs
1.2 Modern methods of water treatment
1.2.1 Technological scheme of preliminary water treatment
1.2.2 Technologies chemical desalination based on ion exchange filters
1.2.3 Technology of thermal water desalination
1.3 Main directions for improving TLU schemes
1.3.1 Scheme of traditional chemical desalination
1.3.2 Schematic of thermal desalination
1.3.3 Scheme of chemical water desalination with effluent evaporation
1.3.4 Scheme of thermochemical desalination with mixing of all or part of the effluents of Na-cation exchange filters with source water
1.3.5 Scheme of thermochemical desalination with discharge of a part of wastewater from Na-cation exchange filters
1.3.6 Scheme of chemical desalination by UP.CO.R technology
1.3.7 Improved chemical desalination scheme
1.4 Comparative analysis of environmental performance of water desalination schemes at TPPs and NPPs
1.5 Analysis of existing methods of disposal of chemical water treatment sludge at TPPs and NPPs
1.6 Brief conclusions and statement of the research problem
Chapter 2 Research Methods
2.1 Study of the physicochemical properties of sludge from the HVO TPP and
2.2 Study of radiological properties of sludge from TPP and Volgodonsk NPP
2.3 Study of induced activity in the sludge of the Volgodonsk
2.4 Chemical analysis of components in the manufacture of model solutions of source water
2.5 Methodological aspects of the study of sludge from the VLU VoNPP, RoCHPP-2 and technological masses based on these sludge
Chapter 3 Results of an experimental study of the properties of sludge from the HVO of TPPs and NPPs
3.1 Physico-chemical and granulometric characteristics of sludge from the HVO of TPPs and NPPs
3.2 Study of the phase composition and thermodynamic properties of CWT sludge
3.3 Results of the study of the radiological and hygienic characteristics of the sludge from the chemical treatment plant of the Volgodonsk NPP and six CHPPs and SDPPs of the Russian Federation
3.4 Results of the study of induced activity in the sludge of the chemical treatment plant of the Volgodonsk NPP
3.5 Mathematical determination of the composition of sludge from HVO TPPs and NPPs based on data on the quality of source water
3.6 The results of the study of the technological properties of raw materials based on sludge from HVO TPPs and NPPs
3.6.1 Results of the study of the plasticity of mixtures of sludge with clay
3.6.2 The results of the study of the mechanical strength and binding ability of masses based on sludge
3.6.3 The results of the assessment of the strength of concrete mixtures based on sludge
3.6.4 Results of the study of the technological characteristics of ceramic products based on the sludge of the Volgodonsk NPP
3.6.5 Results of the study of the mechanism of formation of the structure of sintered masses with additives of CWT sludge
3.7 Results of the study of the technological characteristics of obtaining lime from the sludge of the Volgodonsk NPP
3.8 Summary
Chapter 4 Development of a multi-purpose technological scheme for chemical desalination of TPP feed water and methods for sludge disposal
HVO (on the example of the Volgodonsk NPP)
4.1 Initial data for the design of the HVO scheme 93 4.1.1 Technological characteristics of the modernized HVO scheme
4.2 Option for modernization of the CWT scheme with waste-free technology for the processing of saline effluents
4.3 Development of a WTP scheme with the disposal of sludge waste and saline effluents
4.4 Summary
Chapter 5 Technical and economic characteristics of the multi-purpose non-waste scheme of chemical water treatment of the Volgodonsk NPP
5.1 Results of a feasibility study comparing make-up water desalination technologies at TPPs and NPPs
5.2 Technical and economic indicators of the construction and modernization of the chemical water treatment of the Volgodonsk NPP
5.3 Calculation of costs for thermal energy in the production of products from the sludge of the CWT VoNPP
5.4 Summary 116 Conclusion 118 References
Introduction to the thesis (part of the abstract) On the topic "Development of rational methods for the waste-free use of sludge and salt-containing effluents from power plants"
In connection with the obsolescence and physical aging of a large fleet of power equipment and the growth in the scale of energy development, both in Russia and in other countries, there is a need to use new technologies and, first of all, in more advanced technological schemes for water treatment to feed steam boilers of thermal power plants and steam generators of nuclear power plants. During the development and operation of such schemes, the contradictions between the efficiency and environmental friendliness of the power plant as a whole are often exacerbated.
In many advanced countries of the world, the use of technologies that do not meet environmental criteria is prohibited /1-3/. However, existing energy technologies are implemented mainly on a single-purpose basis. In this case, only the combustible mass of fuel, demineralized or softened source water is used, and the so-called "waste" - ash, slag and sludge are sent to ash dumps and sludge collectors.
In this situation, the priority task of the energy industry is the need to develop multi-purpose energy technologies that ensure the fullest possible use of primary resources with simultaneous processing and disposal of so-called waste, which is a valuable raw material for related industries /4-5/.
At steam turbine power plants, water is used as a working fluid and as a coolant, as a participant in technological processes in energy systems and units. It is known that the most stringent requirements are imposed on the quality of water, which works in the main energy cycle. The efficiency and reliability of the equipment of modern thermal power plants and nuclear power plants is determined by the cleanliness of the heat transfer surfaces of the metal in contact with water and steam. The intensity of heat transfer in modern TPP steam boilers reaches 466-582 kW/m2. In NPP reactors, this value reaches 11.6 kW/m2. Formation of deposits-impurities of water on surfaces steam generators(SG) and on the blade apparatus of turbines not only sharply reduces their efficiency, but with significant amounts of deposits causes damage individual parts boilers and turbines. The experience of many years of operation of power units of TPPs and NPPs in Russia and abroad indicates that necessary condition their uninterrupted and economical operation is the rational organization of water treatment and the water regime of SGs, strict observance of reasonable operational standards for the quality of the coolant and working fluid of TPPs and NPPs.
To date, questions about the minimization and neutralization of wastewater water treatment installations (TLU) of TPPs and NPPs have been worked out quite fully /6-11/, however, none of the technological schemes, both in domestic and foreign energy, implements in practice the principle of complete utilization of TLU waste /12-13/.
Particular problems are associated with a significant amount of sludge-containing waters formed at the stage of preliminary preparation of make-up water using lime. Traditionally, WLU sludge is discharged into sludge collectors, which require ever-increasing areas, increasing the environmental load on the adjacent territories of power plants. This problem is especially acute for nuclear power plants located, as a rule, near large bodies of water.
Foreign and domestic experience indicates that the sludge of the TPU of TPPs and NPPs is not waste waste, but a valuable raw material for many industries and Agriculture/13-15/. In this regard, one of the main tasks of the energy industry is the transfer of WLU sludge from the category of "waste" to secondary raw materials. This will allow solving the most important environmental, economic and social issues.
Thus, the development of effective technological schemes for water treatment with rational methods of waste disposal of WLU will allow solving an essential task for the energy industry - the creation of a multi-purpose, waste-free, environmentally friendly system of water use at thermal power plants and nuclear power plants.
The purpose of the dissertation work is to improve the technological scheme for the preparation of make-up water with the development of rational methods for the disposal of WPU sludge on the example of the Volgodonsk NPP.
Specific research tasks to be solved in the work:
Comparative analysis of modern technological schemes of water treatment at TPPs and NPPs;
Analysis of existing methods for the disposal of polluted waters and sludge waste from TPU TPPs and NPPs;
Study of the physicochemical and radiological characteristics of the sludge of the Volgodonsk NPP (VoNPP) with the aim of using it as part of products that provide protection against ionizing radiation;
Investigation of the technological characteristics of the VPU sludge of the VoNPP as a raw material additive in the production building materials and slaked lime;
Study of the induced activity (degree of activation) of the VLU sludge of the VoNPP in areas with different intensities of ionizing radiation directly on the operating equipment of the VoNPP;
Calculation and theoretical studies of the degree of activation of the components of the sludge when irradiated with thermal neutrons;
Development of a technological scheme for rational water use at the VoNPP with the disposal of chemical waste sludge.
The scientific novelty of the work is as follows:
New experimental and calculated data were obtained on the degree of activation of the sludge from the chemical treatment plant of the VoNPP when it was irradiated with gamma quanta and thermal neutrons;
A mathematical model has been developed in the form of a system of regression equations, which makes it possible to determine the concentrations of the six main components of the WoNPP sludge depending on the quality of the source water;
Physico-chemical methods have established the mechanism for the formation of the structure of the sintered mass based on the WPU sludge in the production of ceramic products;
The optimal ratio between the mineralizers and the sludge content in the sintered mass, which is defined as the alkaline earth module M;
The properties of masses and products were studied at M values from 1 to 7;
A technology has been developed and experimentally tested for high-speed thermal treatment of the sludge from the VPU of the VoNPP and the production of active lime from it, followed by its use in the water treatment cycle;
A complex technological scheme of water treatment with disposal of sludge from salt solutions of the HVO VoNPP has been developed.
The practical significance of the work lies in the fact that the results of industrial, laboratory and computational studies are used in the practice of operating technological schemes for water use at thermal power plants and nuclear power plants, design and research institutes, in particular:
The principles and technical and economic conditions for the implementation of the water treatment scheme with the disposal of saline effluents and CWT sludge were used by JSC NII EPE and RoTEP in the design and creation of a multi-purpose pilot plant (OPU) for gasification of solid fuels;
The compositions of the masses, including the sludge of the VLU of the VoNPP, were introduced at the Shakhty plant "Stroyfarfor";
The basics of the technology for rapid drying of the VPU sludge of the VoNPP and the production of active lime from it were used by CJSC " Belokalitvinsky lime plant»;
The principles for the implementation of a multi-purpose technology for water treatment with the disposal of saline effluents and sludge from the WLU have been introduced at the Novocherkassk State District Power Plant, the Kursk NPP, the Kalinin NPP, and the Rostovskaya CHPP-2.
The reliability and validity of the results of the work are ensured by the use of modern methods of planning experiments, processing their results by mathematical modeling using a PC, reproducibility of the data obtained by the author, the results of industrial and laboratory studies, their coordination with independent data of other authors and the use of fundamental laws of physical chemistry and nuclear physics in the work.
Planning and direct participation in natural and laboratory research;
Processing and analysis of the results of computational and experimental studies, development of masses for the production of prescription modules and optimal compositions of building materials based on the VPU sludge of the VoNPP;
Summarizing the results obtained and putting forward practical proposals;
Development of a technological scheme for rational water use with the disposal of salt-containing effluents and sludge waste from the WLU and the heat of exhaust gases in the production of secondary products from sludge directly at the VoNPP.
Approbation of work
The main results of the research were reported and discussed:
At the All-Russian Scientific and Practical Conference Rosenergoatom (Moscow, 2002);
At the seminars of the department " Nuclear power plants» MPEI (Moscow, 2002);
At the seminars of the department " Thermal power technologies and equipment» VI YuRGTU (NPI). At the technical council of the department " Thermal power plants» SRSTU (Novocherkassk 2000-2002);
At the technical council of OAO NII EPE (Rostov-on-Don, 2001-2002);
At the international conference Diagnostics of power plant equipment"(Novocherkassk, 2002);
At the IV International Conference "Perspective Tasks engineering science"(Igalo, Montenegro, 2003).
Publications at work
Dissertation conclusion on the topic "Thermal power plants, their energy systems and units", Palamarchuk, Alexander Vasilyevich
1 The results of the study showed that the improved CWT scheme of the VoNPP, including the waste-free technology for processing salt-containing effluents and WLU sludge, is quite competitive in terms of the relative technological component with all other CWT schemes.
2 It has been established that the production of additional marketable products from sludge and concentrated effluents of chemical water treatment reduces the cost of 1 m3 of demineralized water to 1.02 rub/m3 in 1991 prices.
3 The developed version of the HVO modernization also has good performance in terms of operating costs and present costs compared to the traditional scheme chemical desalination without processing salt-containing effluents and disposal of sludge.
4 It is shown that it is more economically feasible to produce concrete mixtures, thermal insulation products, lime, ceramics and others directly at thermal power plants and nuclear power plants, primarily for their own needs. At the same time, the costs of sludge transportation, thermal, electrical energy, technological operations, sludge storage costs and others are significantly reduced compared to the option of creating an autonomous production, outside TPPs and NPPs, for these purposes.
CONCLUSION
1 The results of our work comparative analysis schemes and methods of chemical water treatment made it possible to identify the main directions of technological improvement of the scheme of chemical desalination at the Volgodonsk NPP, providing for the technology for processing salt concentrate of wastewater and sludge from chemical treatment and obtaining finished commercial products from them.
2 A CWT scheme of the Volgodonsk NPP has been developed and is being implemented in practice with multi-purpose waste-free use of source water from the Tsimlyansk reservoir by obtaining:
Chemically demineralized water for energy consumers;
15% NaCl solution and active lime used again in closed loop water treatment;
Concrete mix filler based on CWT sludge for radioactive waste conditioning;
Ceramic, thermally insulating and protective from ionizing radiation plates and packages based on sludge.
3 As a result of physical and chemical studies, it was found that the sludge of the HVO TPP and Volgodonsk NPP have a more intense reactivity than some natural materials(for example, chalk, etc.); due to its finely dispersed and homogeneous composition, the sludge naturally fits into the technological processes for the production of building products from it.
4 The results of gamma spectrometric studies of Volgodonsk NPP sludge samples showed that the sum of the ratios of the specific activities of radionuclides contained in the sludge is 2 orders of magnitude less than the normative "Minimum Significant Specific Activity" (Ао/МЗУА=0.019), and the effective specific activity of the sludge (Аeff) is an order of magnitude less than the criterion " Radiation safety standards» , i.e. AEfLES= 30.1 Bq/kg
5 Using the method of a full factorial experiment, a mathematical model was developed in the form of a system of regression equations, which makes it possible to determine the oxide composition of the sludge (six basic oxides) according to the data on the quality of the source water
I ^ turbidity, pH, Ca hardness, etc.) and evaluate the feasibility of further use of sludge as a raw material component of products.
6 As a result of studying the technological properties of raw materials based on TPP and NPP sludge, it was found that the quality of products (Ki) is a function of multiparametric factors:
Ki \u003d f (Xc, d .; Msh; Mgu; dt / dr; tmax; Experimentally obtained thermographic dependences of the mass sintering process show (Fig. 3.1) that the inclusion of sludge in their composition is technologically preferable to natural carbonate materials.
7 The limits of the recipe ratio of alkaline earth and alkaline oxides in the initial masses have been established, which increase the intensity of sintering and the strength of products. This ratio is defined as the recipe module:
Мр = R0/R20 = (CaO+MgO) / (Na20+K20) Physicochemical research methods revealed the mechanism of formation of the structure of sintered masses at modulus values from 3.4 to 5.9. It is shown that the strength of concrete mixes based on CWT sludge is competitive with the strength of concretes based on natural limestone - shell rock.
8 New experimental and calculated data were obtained on the activation of the CWT sludge of the VoNPP when it was irradiated with 7-quanta and thermal neutrons of a certain intensity. A mathematical dependence of the induced activity (Cnav) of the sludge components on their half-life is proposed. It has been established that the use of heat-insulating and protective products based on sludge in NPP premises with a certain intensity of ionizing radiation does not pose a danger to the operating personnel in relation to induced activity.
9 A technology for obtaining active lime from the sludge of the HVO of the Volgodonsk NPP by the method of its high-speed heat treatment has been proposed and experimentally tested. Technological tests of control samples of lime obtained from the sludge of the water treatment plant of the VoNPP and from natural limestone showed that, in accordance with GOST 9179-77, lime from the sludge belongs to the category of fast-extinguishing materials and, according to the quality criteria, can be used again in the closed water treatment cycle of the VoNPP.
10 It is shown that it is more economically feasible to produce concrete mixtures, thermal insulation products, lime, ceramics and others directly at thermal power plants and nuclear power plants, primarily for their own needs. At the same time, the costs of sludge transportation, thermal, electrical energy, technological operations, sludge storage costs and others are significantly reduced compared to the option of creating an autonomous production, outside TPPs and NPPs, for these purposes.
11 It has been established that obtaining additional marketable products from sludge and concentrated CWT effluents reduces the cost of 1 m3 of demineralized water to 0.55 rub/m3.
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At present, a significant amount of drainage water is discharged into reservoirs at all thermal power plants and boiler houses. The amount of these waters reaches 10% of the amount of water prepared for the needs of thermal power plants.
By origin, the effluents from thermal power plants and boiler houses are divided into four categories: effluents from technological cycles; effluents of chemical water treatment in the preparation of water to make up for losses; storm and flood drains; household drains. Effluent from the technological cycles of existing thermal power plants and boiler houses has historically developed for the following reasons:
1. The “Design Standards” in force at that time provided for the concept of “conditionally clean effluents”, which allowed designers with a “clear conscience” to design the discharge of the following effluents into water bodies: continuous and periodic blowdown of boilers, evaporators; storm and flood drains; one-time unorganized leaks from equipment and pipelines; cooling of bearings of the main and auxiliary mechanisms; cooling system purges in cooling towers; emptying equipment, tanks, pipelines; stuffing box leaks, rotating mechanisms. Nothing was mixed into these drains in an organized manner, but with the slightest deviations in the operation of the equipment, the quality of these waters necessarily deteriorates.
2. It was mistakenly believed that it was possible to build omnipotent treatment facilities that would ensure the proper quality of discharged waters or return them to the cycle. Therefore, part of the industrial waste was discharged into the sewer. These were neutralized waters from acid cleaning of equipment and discharges after hydro cleaning of premises and equipment of the main production shops. Another part, oily drains from different schemes, was sent to the general station oil trap for cleaning from impurities of fuel oil and oil. The wash water of the oily condensate filters was sent there, possible leaks of fuel oil, oil from technological equipment, steaming before repair of fuel oil pipelines, oil pipelines, washing water of external heating surfaces before repairs.
At the same time, streams with different concentrations of oil products (1-50)% were first mixed to obtain a mixture with a concentration of up to 5%, then the purification technology again required concentration in order to more effectively separate fuel oil and oil.
After treatment facilities discharges of various purposes are mixed with “conditionally clean” ones - and when discharged into a reservoir, it turns out (on average for a hospital) it’s not scary. But when you know that all the reagents received during the year by the station (salt, alkali, acid, lime, etc.) are ultimately discharged into water bodies in a dissolved form, it becomes clear how we deceive ourselves.
In the 80s, the absurdity of such decisions was realized, and difficulties arose in coordinating with the inspecting authorities for nature protection.
Design organizations, together with the directorates of CHPPs under construction, were forced to develop non-traditional solutions to reduce the impact of discharges from CHPs and boiler houses.
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With such a commonwealth, at many facilities being designed and under construction at that time solutions have been developed that fit into the following concepts:
Each discharge must be cleansed and returned to the same circuit and with the same quality from which it was formed;
Restoration of the quality of effluents or their exclusion should be carried out using thermal technologies;
It is necessary to use technologies that exclude the possibility of mixing or overflow of different media if a gap appears in the separating surfaces;
The drains of each functional circuit must be cleaned and returned to the cycle by the personnel maintaining this circuit.
With these provisions, it turned out that almost all drains can be excluded. The following are the main solutions (in fact, there are many more) that allow for a significant reduction in the volume of wastewater from energy production:
1. Evaporators for continuous and intermittent purge;
2. Collection of chemically purified or desalinated water from samplers, seal leaks;
3. Steam supply to industrial consumers through steam converters;
4. Use of secondary steam for fuel oil economy after individual steam converters, or installation of heaters with double heating surfaces;
5. Separation of the condenser cooling circuit and mechanism cooling circuit into hydraulically independent circuits, which makes it possible to exclude the possibility of any impurities entering the condenser cooling system. That is, in the purge of the system there will be only natural salts in a concentrated form, which can be discharged into the reservoir with a diffuse release;
6. Transition from chemical methods of purification of make-up water of the heating system to corrective treatment of make-up water with inhibitors (IOMS, ODF, etc.). This sometimes requires the installation of a second circulation circuit for hot water boilers;
7. Reconstruction or replacement of atmospheric make-up water deaerators with double-acting deaerators (DND);
8. Replacement of stuffing box seals with end seals;
9. Installation of dividing partitions between bearings and seals;
10. Closed scheme of acid washing with neutralization, settling and storage until the next washings. An alternative replacement is steam-oxygen cleaning of boilers and hydro-mechanical washing of condensers and heaters;
11. Separation of contours of sampling points;
12. Collection of storm and flood water for later use;
13. The device of reverse schemes of hydraulic harvesting;
14. Combustion of concentrated fuel oil and oil effluents in boiler furnaces;
15. Organization of dry storage of ash.
The organization of work and responsibility for the treatment and return of wastewater to the relevant schemes by the personnel operating these schemes promptly encourages personnel to exclude unreasonable amounts of discharges. Thus, the quantity of drains and the final quality of the coolant are controlled by one person.
The most difficult issue was the psychological restructuring of the staff of the main shops. You can often hear that it is not his job to clean up discharges from turbines and boilers. It's a paradox: evaporators, deaerators, BOU are operated by some, while others are responsible for water quality. At the same time, the results of poor water quality (fistulas, deposits, burns) are "raked" by the same technologies.
Responsible for the final quality of the coolant in a particular scheme, wastewater regeneration becomes one of the main duties. Moreover, this is carried out thermally, which is closer to the staff of the main workshops than chemical water treatment. If you realize and accept this, then everything else is a matter of technology.
Effluents during water preparation for their replenishment in the HVO
When carrying out measures for the return of discharges in all functional diagrams and in each workshop, there is theoretically no need for a permanent general water treatment to make up for losses. For unforeseen situations, "reverse osmosis filters" of limited capacity may be provided. Accordingly, discharges of this category must be disposed of thermally.
In the case of deaeration of make-up water for open hot water intake in the DND, even for an emergency, chemical water treatment is not required. From one thousand tons per hour of deaerated water in the DND, 50 tons per hour of demineralized water are obtained.
Storm and flood waters
The appearance of these waters is periodic. Therefore, the issue of disposal is the collection and sedimentation of these waters. Then they are used for irrigation, dedusting of fuel supplies, make-up of circulating cooling circuits and as source water for preparation of replenishment of leakages of functional circuits.
Industrial and economic effluents
Agreed discharges of industrial effluents to household faecal treatment facilities do not clear mineralization, but increase the diameters of sewage systems and the performance of treatment facilities. Mineralized waters are simply diluted and discharged into reservoirs. In general, economically, this method of waste disposal is less profitable than returning them to the cycle through local treatment.
All of the above at first glance may seem to many declarative and impracticable. But we can compare, as we are used to doing, with foreign counterparts: this approach has been used there for a long time.
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The author of these lines was directly involved in the development of such solutions, he implemented many of them in practice and is ready to confirm their implementation with examples. It will not be superfluous to repeat that deciding ecological problems in this way, we simultaneously increase the reliability, quality and economy of water treatment. Everyone can verify this for themselves. When comparing, one must proceed from the fact that the solutions to all issues must be comprehensive.
To implement drainless (low drain) schemes, only an ecological reboot of the minds of service personnel and designers is required.
Vladimir Shlapakov, ex-director of the Nevsky branch of JSC VNIPIenergoprom
photo by Oleg Nikitin
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DDN-1000/40 (Naberezhnye Chelny CHPP)
Evgeny Spitsyn, Commercial Director of ECOTECH LLC:
I consider the wording of paragraph 7 as “Reconstruction or replacement of atmospheric make-up water deaerators with double-acting deaerators (DND)” to be incorrect. The fact is that at present only one dual-use technology has been developed and protected by patents of the Russian Federation, which involves the deaeration of a large volume (550-1000 t / h) of make-up water of the heating system and the simultaneous production of demineralized water suitable for feeding boilers high pressure in quantities up to 30-60 t/h within one apparatus. This technology and the design of the apparatus was developed by Vladimir Sergeevich Petin and protected by RF patents. On the basis of a license agreement, it belongs to the ECOTECH company on exclusive rights and is called the Dual Purpose Deaerator (DDN ECOTECH). In addition, dual-purpose deaerators DDN ECOTECH were introduced at Naberezhnye Chelny CHPP by ECOTECH in only two copies (experimental DDN-800/30 and industrial DDN-1000/40).
Section content
An important task of protection environment is the rational use and protection of water resources. The discharge of industrial and domestic wastewater must be carried out in such a way that there is no pollution of water bodies in which self-purification processes take place. The main of these processes are: precipitation of coarse substances, oxidation (mineralization) of organic impurities, neutralization of acids and alkalis, hydrolysis of heavy metal ions, accompanied by the formation of sparingly soluble hydroxides of the latter.
The main factors influencing the processes of self-purification of water bodies are: water temperature, mineralogical composition of impurities, oxygen concentration, water pH, concentration of harmful impurities. The presence of the latter in reservoirs leads to a decrease in water quality, makes it difficult to purify and sometimes makes it unsuitable for further use.
The oxygen regime of the reservoir has a particularly important influence on the processes of self-purification. The consumption of oxygen for the mineralization of organic substances (with the participation of bacteria) is usually expressed by the value of biochemical oxygen demand (BCD). With excessive discharge of organic pollutants into the reservoir, there is a shortage of oxygen in the reservoir, resulting in decay of organic impurities and, as a result, deterioration in water quality.
Water objects are subdivided into state reservoirs for drinking, cultural purposes and reservoirs intended for fish farming. Depending on this, norms for the discharge of wastewater into water bodies are established. Permissible wastewater discharge is determined by the ratio
\(\sum _(i=1)^(n)\frac((c)_(i))((\text(MAC))_(i))\le 1\) , (7.7.1)
Where c i– concentration i-th component in the reservoir; MPC i- its maximum permissible concentration in a reservoir; n- the amount of polluting components in the effluents.
When discharging sewage from boiler houses, the maximum permissible concentrations (MPC) of a harmful substance in a reservoir are its concentrations, which, when exposed daily for a long time to the human body, do not cause any pathological changes and diseases, and also do not violate the biological optimum in the reservoir.
Currently, far from all the harmful substances discharged into water bodies have been determined, which is explained by the duration and great difficulties in their determination. The difficulty in determining the MPC is due to the fact that, in addition to its sanitary value, it is also of great economic importance, since an unjustified underestimation of the MPC can lead to high costs for water treatment.
Discharge into water bodies of new substances, the MPC of which has not been determined, is prohibited. In table. 7.7.1 shows the MPC values in water bodies.
For wastewater, MPC values are not standardized, so the required degree of their treatment is determined only by the state of the reservoir after the discharge of wastewater into it. At the same time, the content of harmful substances must comply with sanitary standards in reservoirs for drinking and domestic water use in the alignment located 1 km upstream of the nearest water use point, and in stagnant water bodies - at a distance of 1 km on both sides of the water use point.
For fishery ponds sanitary norms refer to areas in the alignment or below the wastewater discharge, taking into account the possible degree of their mixing from the place of discharge to the boundary of the fishery area of the reservoir.
Table 7.7.1. Maximum permissible concentrations of harmful substances in water bodies, mg/kg
When discharging water within any locality requirements for the composition and properties of the water of the reservoir should apply to the wastewater itself.
When discharging wastewater, the maximum amount of impurities to be discharged (maximum allowable emission - MPE) per unit of time, which is determined by the conditions of discharge, the nature of impurities, their quantity, the discharge regime, the flow rate of the reservoir and other specific features of the reservoir and discharge, should be established. Emission limits must be calculated for specific conditions and largely determine the required degree of wastewater treatment.
Of great importance is the way wastewater is discharged. With dispersed wastewater discharges, the intensity of their mixing is minimal. The best results are obtained by the discharge of sewage into the deep layers of the reservoir through perforated pipes.
Wastewater from industrial enterprises is divided into heavily polluted, which require strong dilution when discharged into a reservoir in order not to exceed the MPC; lightly polluted; conditionally clean water, which is practically not polluted in technological processes (for example, water used to cool equipment); VAT residues and mother liquors, which are exclusively concentrated effluents that cannot be treated and sent for destruction or disposal, or are buried in special landfills; household and fecal effluents, which are sent directly to biochemical treatment.
Boilers are sources of the following pollution: waste water from water treatment plants; wastewater contaminated with oil products; wastewater generated after flushing the heating surfaces of boilers running on fuel oil; wastewater after chemical treatment and depreservation of equipment; waste water from hydraulic ash removal systems; municipal water.
In industrial heating boiler houses, such a water treatment method as Na-cationization is more often used. Wastewater from water treatment plants (WTP) is conditionally divided into saline and fresh. The former account for 3.5%, the latter - 7% of the total amount of treated water. fresh water are formed when washing clarifiers and clarification filters. These waters are highly alkaline (pH = 11.5). As a result, their discharge near the surface of water bodies is not allowed, since in water bodies pH = 6.5 - 8.5, and the content of suspended solids should not exceed 0.75 mg / kg of water.
The treatment scheme for fresh wastewater from the TLU is simple. Effluent is sent to sludge collectors, where they are settled. It is recommended to have two such tanks. Settling takes place in one of them, while the other is filled with effluents. The capacity of each of them should ensure the settling of drains for at least 1 - 2 hours. After settling, water is evenly fed into the clarifier. The sludge accumulated in the settling tanks contains 92-95% calcium carbonates, the moisture content of the sludge after the sludge collector is 97-98%. With the help of sludge pumps, it is fed to filter presses, in which its moisture content is reduced to 46 - 60%. After filter presses, it is not harmful and can be stored outdoors and used to prepare milk of lime. Water after the filter presses is supplied to the clarifiers. Thus, wastewater from clarifiers and clarifier filters can be fully utilized in water treatment plants.
Most effective way neutralization of wastewater from Na-cationite filters is the softening of effluents with lime milk with the precipitation of magnesium oxide hydrate and their subsequent evaporation in tubular evaporators or in flash evaporation devices, then in rotary evaporators and dehydration in centrifuges. As a result of such processing, marketable products are formed: crystalline sodium chloride, returned to the water treatment plant; liquid 40% solution of calcium chloride (consumer - refrigeration industry) and magnesium oxide hydrate, which can be used in the production of building materials.
Noteworthy is the evaporation of salt-containing effluents in devices with submersible burners and in bubbling evaporators. In the latter, high-temperature flue gases can be used. Evaporation of effluents can be carried out in such devices until they turn into a dry residue with a salt content of 800-1000 kg/m 3 .
The construction of evaporator plants in boiler rooms with low-pressure boilers is not economically justified. In this case, water treatment methods and schemes justify themselves, allowing to reduce the content of harmful impurities in wastewater (see paragraph 3.18.2).
The methods of settling, flotation and filtration are used to treat wastewater from oil products. The sedimentation method is based on the principle of separation of oil products under the action of the difference in the density of particles of oil products and water. Settling of oil products is carried out in special oil traps (Fig. 7.7.1). Waste water 1, entering the receiving chamber 3, then passes under the recessed partition 5, enters the settling chamber 4, in which the separation of oil products and water takes place. Purified water passes under the next recessed partition 5 and is discharged from the oil trap through the pipeline 7. Particles of oil products float up, forming a film 2, and are removed from the oil trap using scrapers through oil intake pipes 6. Oil products emerge at a water temperature of about 40 ° C, and at 30 ° C, oil products settle in the oil trap. The density of highly viscous cracked residues exceeds the density of water at any temperature, and therefore they cannot float to the surface of the water. When settling, drops of oil products float up at a low speed.
Rice. 7.7.1. Oil trap scheme
The intensification of the process of separation of water and oil products is achieved by flotation of wastewater, accompanied by the removal of particles of oil products from the water with air bubbles that float in the water and particles of oil products adhere to the surface of which under the action of surface tension forces. The floating speed of air bubbles in water exceeds the floating speed of oil particles by 10 2 - 10 3 times. Distinguish between pressure and non-pressure flotation.
During pressure flotation, wastewater 1 (Fig. 7.7.2) enters chamber 2, from which pump 5 is fed into a special pressure tank 6 through pipeline 3 by pump 5. Air 4 is pumped into pipeline 3, up to the pump, under an overpressure of 0.5 MPa. The water-air mixture from the container 6 enters the flotation chamber 7, in which the pressure is released, as a result of which air bubbles are released from the water and float up, forming foam on the surface of the water with a high content of oil products. The foam is collected in the foam collector 8, and the purified water is discharged from the flotation chamber.
Fig.7.7.2. Scheme of the installation for pressure flotation of waste water
In non-pressure flotation, air bubbles are formed during the bubbling process. Air is supplied to the water through a perforated pipe located at the bottom of the flotation chamber.
Wastewater filtration is carried out at the final stage of their treatment. The process is based on the effect of sticking of emulsified particles of oil products to the surface of the grains of the filter material. As the latter, quartz sand, anthracite or sulfo coal, worked out in Na-catonite filters, is used. Bulk filters are recommended to be regenerated with superheated steam. As a result, oil products are heated, and they are removed under pressure from the backfill. The cost of steam for regeneration in terms of condensate is not more than two volumes of the filter layer. Condensate contaminated with oil products is fed into oil traps or floaters.
Each of the methods of wastewater treatment from oil products is most effective in a certain range of dispersed composition of oil products. Oil traps effectively trap particles big size, floaters - smaller particles. The smallest particles are removed from wastewater by filtration. The degree of water purification according to this scheme is higher than 95% and weakly depends on the initial concentration of oil products in wastewater. Purified water is most often mixed with fresh water sent for chemical water treatment.
The waters after washing the external heat exchange surfaces of boilers operating on fuel oil are acidic (pH = 1–3) and contain coarse solids (iron oxides, silicic acid, undissolved ash particles), which are easily removed during settling, as well as impurities in the form of weak solutions (diluted sulfuric acid, iron sulfate, vanadium, nickel, copper compounds, etc.). For these waters, it is advisable, along with purification, to provide the isolation of such valuable products as vanadium and nickel.
One of the ways to treat wastewater after washing the equipment is to neutralize them in neutralization tanks with alkaline solutions (for example, sodium hydroxide) until harmful impurities precipitate and then are removed from the water. The clarified water is reused for washing the heating surfaces of the boilers, and the sludge is fed for dehydration in press filters.
To clean the boilers from scale and deposits, chemical washing is carried out. The content of impurities in wastewater after chemical washing depends on the technological scheme of washing and the type of boiler. 70 - 90% of contaminants are reagents used in flushing. To receive these effluents, settling pools are designed for the entire volume of water discharged into the pools after its threefold dilution. In the pools there is a partial neutralization of acidic and alkaline effluents. Then the water is fed into the neutralizer tanks, in which harmful impurities are released after the effluent is treated with lime or other reagents. The settled sludge is sent to sludge dumps, and the clarified water, after acidification to pH = 7.5 - 8.5, is fed to biochemical treatment.
Waste water after hydraulic ash and slag removal from solid fuel boiler houses is formed during the transportation of ash and slag with technical water to ash and slag dumps. With a direct-flow ash and slag removal system, all impurities are discharged into water bodies in a dissolved state and in a coarsely dispersed form, which did not have time to settle in ash and slag dumps. With the reverse scheme of hydraulic ash and slag removal, part of the harmful impurities can be retained as a result of filtration through ash and slag dumps.
The most important indicators of the quality of clarified water are alkalinity, sulfate content, as well as the concentration harmful impurities. The first two indicators show the possibility of deposits in the reverse ash and slag removal system, which indicates the possibility of deterioration of the state of the reservoir.
The value of the pH value for water bodies after the discharge of sewage into them after hydraulic ash and slag removal should not exceed 6.5 - 8.5, and the concentration of harmful substances should not exceed the maximum allowable concentrations, which is achieved by appropriate selection of the ratio of water and ash flow rates, as well as maintaining the required pH value.
Salt-containing effluents after mechanical treatment are fed to the reagent flotation unit. A sodium hydroxide solution is used as a flotation agent. At the same time, oil products and hardness salts are removed from the wastewater. After flotation, the effluents enter the E-8 tank, from where they are sent to the heat exchangers T-16 T - P T-12, where they are heated by the heat of vapor condensation and cooling of the distillate.
| Scheme of hydrogenation of the acetophenone fraction. |
Salt-containing effluents after mechanical treatment are fed to the reagent flotation unit. A sodium hydroxide solution is used as a flotation agent. At the same time, oil products and hardness salts are removed from the wastewater. After flotation, the effluents enter the E-8 tank, from where they are sent to the T-I6 T-II T-I2 heat exchangers, where they are heated by the heat of vapor condensation and cooling of the distillate.
A special place is occupied by the elimination of salt-containing refinery effluents, which include: ELOU runoff, blowdown water from water supply systems, purging of waste heat boilers, etc. ELOU effluents are formed by mixing formation and circulating water supplied to oil flushing. Blowdown water of the water supply system is represented mainly by sulfates and carbonates. Joint decooling of srak effluents greatly complicates the problem of separating salts for subsequent use. With separate desalination, sodium chloride (ELOU waste), sodium sulfate (recycled water), magnesium oxide and calcium oxide can be separated from the effluents.
The main aluminum chlorides were tested for additional treatment of salt-containing effluents from electric desalination plants entering the UTTP, as well as for the purification of highly concentrated solutions (brine) from oil products obtained after UTTP.
Purification of solid salt wastes or salt-containing effluents can be carried out by various physico-chemical or thermal methods. The choice of a rational cleaning method depends on the chemical composition, concentration and properties of impurities.
In water samples the same number species (19 each) were represented by Cyanophyta and Bacillariophyta. Diatoms developed most massively in the equalizing pond, where salt-containing effluents settle. The floristic composition of aquatic algae was similar in samples taken at different stages of mechanical treatment of industrial effluents. With the pumping of industrial waste from one stage of purification, the components of the algocommunity also pass.
The use of anion exchangers in the salt form, in addition to the above, has a number of advantages: an increase in capacity by 1.5 - 2 times (Fig. 2), easier regeneration. In practice, any acidic salt-containing effluents can be used to convert the anion exchanger into a salt form.
Industrial and storm drains of the plant, repair and mechanical base, thermal power plant, washing and steaming base and other facilities are subjected to mechanical and then biological treatment and are fully returned to the circulating water supply system. Sulphurous-alkaline effluents from jet fuel alkalization, previously purified from hydrogen sulfide at carbonization facilities, as well as salt-containing effluents from CDU, raw materials reservoirs, commodity base, are subjected to evaporation. The condensate resulting from the evaporation of wastewater is sent to the circulating water supply system. Domestic wastewater from the plant, mechanical repair base, CHP is sent to the city sewer.
Biological treatment facilities were overloaded. In them, in addition to industrial effluents from the refinery, wastewater from the SC plant and city wastewater was discharged. Salt-containing effluents from ELOU were sent to the BTP approximately 20,000 m3/day.
In general, an environmentally safe system of water consumption and wastewater disposal of chemical plants should include a system of integrated water treatment and integrated wastewater treatment, consisting of chemical and biochemical purification stages. A new element of purification technology is activated carbon adsorption, which can be used alone or in combination with flotation and biochemical oxidation. Chemical and petrochemical enterprises are now discharging large amounts of saline effluents. For plants located in continental regions, to reduce the discharge of salts into water bodies, the practice of thermal neutralization, tested at a number of petrochemical enterprises of the USSR, can be applied. The complex of the above measures makes it possible to implement a system of operation of chemical enterprises without discharge of wastewater and consumption of make-up water. Naturally, the implementation of such large tasks requires significant capital investments.
Depending on the quality of the original oil, the depth of its processing, the catalysts used, as well as the range of commercial products obtained, oil refineries are divided into several groups. Fuel profile plants provide for the production of motor gasoline, aviation kerosene, fuel oil, bitumen, diesel fuel, in some cases paraffin, sulfur, and sometimes aromatic hydrocarbons. The unfavorable environmental situation and increasingly stringent requirements for atmospheric emissions and the quality of wastewater discharged into water bodies lead to the need for further improvement of water supply, sewerage and wastewater treatment systems. Particularly acute is the issue of improving and reconstructing treatment facilities at plants where the facilities have been in operation for more than a dozen years and are not only morally, but also physically obsolete. The reconstruction is intended to replace facilities and equipment, improve treatment technology and increase its efficiency, improve environmental situation. Currently, wastewater at the plant is discharged through two sewerage systems. These effluents go through a treatment scheme that includes oil traps, radial settling tanks, pressure flotation, a complex of biological treatment facilities, after which they are used to replenish water recycling systems. Salt-containing effluents from oil treatment, process condensates from installations and from sulfur production are discharged into the sewerage system II through a pressure collector. These wastewaters are directed to the oil trap, where wastewater with increased pollution from tank trimming also enters.
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DESCRIPTION of the display ""8 2728
Union of Soviet
Socialist
State Committee
USSR for inventions and discoveries
V. V. Shishchenko (71) Applicant
Stavropol Polytechnic Institute (54) WASTEWATER TREATMENT METHOD
INDUSTRIAL BOILERS
The invention relates to the treatment of mineralized natural and waste water and can be used for the regeneration of waste water from sodium cation exchange filters and purge water from steam generators operating on sodium cationic water.
There is a known method for the recovery and reuse of regenerating solutions of sodium-cationite filters by means of their reagent softening (13.. The disadvantage of the known method is the consumption of soda ash and caustic soda to soften the spent solution, as well as the need to add fresh sodium chloride solution. In addition, part of the washing water, which has increased mineralization and hardness, is discarded after use for loosening the filters.
Closest to the invention in terms of technical essence and the achieved result is a method for desalting natural and waste water, including thermal softening and evaporation. in a multi-stage evaporator L2$. thirty
The disadvantage of this method is the low water temperature before thermal softening and a significant amount of water diverted for thermal softening of 50-50%
This goal is achieved by the fact that the wastewater is subjected to thermal softening and evaporation in a high-stage evaporator plant, and the purge water of industrial steam generators is evaporated to a salt content of 100-150 g j kg in the initial stages of this plant, and the wastewater of sodium cation exchange filters is evaporated to the same salt content in the final stages of the same plant, the resulting concentrated solutions are mixed. heat up
Brine after concentration mEq/kg
Water composition
Bicarbonate
Carbonate
Dry residue, g/kg
Water quantity t/h
18 to 130-170 C, the precipitated calcium sulfate is removed, the softened mixture is cooled by throttling to 900 I
100 C, magnesium hydroxide is separated and the filtrate is directed to the regeneration of sodium-kachionite filters. At the same time, lime is added to the mixture of concentrated solutions before thermal softening to a residual magnesium content of 1-5 meq/kg and sodium sulfate to an equivalent calcium concentration.
The drawing shows a diagram of an installation operating according to the proposed method.
The plant includes purge water line 1, steam line 2, evaporators 3 and 4, brine line 5, thermal softener 6, waste water line 7, heat exchanger 8, evaporators 9 and 10, condenser 11, expanders 12 distillate line 13, salt concentrate line 14, line 15, steam line 16, lines 17 and 18, expander 19, lighting caster 20, pipelines 21 and 22.
Purge water and steam, respectively, are fed through pipeline 1 and steam pipeline 2 to the evaporator 3, and then to the subsequent stages of the evaporator plant. In the evaporator 4, the salt content of the concentrate is adjusted to 100150 g / kg and fed through the pipeline
5 to a thermal softener 6. Wastewater from sodium-cationite filters is sent through pipeline 7 to heat exchangers 8 and fed to evaporator 9, passed sequentially through a series of evaporation stages and further evaporated in evaporator 10 to a concentration of salts
100-150 g/kg. The distillate from the condenser 11 and the expanders 12 is supplied to the consumer through the pipeline 13, and the concentrate - through the pipeline 14 for mixing with the concentrate supplied through the pipeline 5 and reagents, according to -. given through the pipeline 15. Concentrated waste is heated to 130-170 C by mixing with steam supplied through the steam line 16.
As a result of mixing the two streams and heating them, crystals of calcium sulfate and magnesium hydroxide are formed. Calcium sulfate, being heavier, is separated in thermal softener b and periodically released through pipeline 17, and softened water, together with magnesium hydroxide, is sent through pipeline 18 to expander 19 for cooling to
100 C and then served in the clarifier
20, where separated from magnesium hydroxide
2O and fed through pipeline 21 to the regeneration of filtrates. magnesium hydroxide. after compaction, they are removed through pipeline 22.
Example. Waste water from industrial boilers is subjected to thermal softening and evaporation in a multi-stage evaporator.
Waste water of sodium-cationite filters (in the amount of 18 t / h) is subjected to evaporation by 8.5 times, and blowdown water of steam generators
25.5 t/h 23 times.
The composition of wastewater from sodium-cationic filters and blowdown water from steam generators before and after evaporation and the composition of the brine after concentration are presented in the table.
Claim
Order 674/26
007 Signature
PPP "Patent", one, Proektnaya st., 4
After mixing the two evaporated streams and heating them to 160 ".. C, precipitation of calcium sulfate and carbonate and magnesium hydroxide occurs. Taking into account the dilution of the treated water with heating steam condensate and subsequent concentration during throttling, 3.3 t / h of brine is formed, which corresponds to the composition of the regeneration solution of sodium cation exchange filters obtained by dissolving industrial table salt °
Compared to the desalination carried out by known way, in the proposed method, the amount of water subjected to thermal softening is reduced by 7-10 times with a corresponding decrease in the dimensions and cost of thermal softeners, the discharge of polluted effluents is stopped, there are no concentrates to be completely dried, and a solution is obtained for the regeneration of sodium cation exchange filters. Separate sedimentation of sediments simplifies their useful use.
The method makes it possible to create a closed system of water supply for industrial boiler houses and obtain savings in the amount of 8 c/m of treated wastewater.
A method for treating wastewater from industrial boiler houses, including thermal softening and evaporation in a multi-stage evaporator plant, characterized in that, in order to utilize the resulting salts and increase the efficiency of the process; purge water of industrial steam generators is evaporated to a salt content of 100-150 r / kg in the initial stages of this installation, and the waste water of sodium-cationite filters is evaporated separately to the same salt content in the final stages of the same installation, the resulting concentrated solutions are mixed, heated to 130-170 C, separated from precipitated calcium sulfate, then the softened mixture is cooled by throttling up to 90-100 C, magnesium hydroxide is separated and the filtrate is sent to the regeneration of sodium cation exchange filters.
