Ukraine, Kyiv city, Kirilivska str. 102
Combustion Technology is a Determining Factor for Efficiency of Fire Engineering Facilities
Fuel and energy as well as economic crises have become acute enough in recent times. They make humanity consider the development of energy efficiency in terms of technical solutions and economic feasibility of their implementation. Besides, the equipment in FSU countries experience other hardships, i.e. physical and moral depreciation as well as lack of allocated funds for rehabilitation. Heads of the heat-generating companies face a tough choice whether replace obsolete equipment with new one (e.g., boilers NIISTU, TVG, DKVR and other with incomplete shielding action replace with KVGM, DE, PTVM etc. with high-scale shielding action) or transfer to electric boilers, or purchase imported, well-executed with advanced automation and said to be highly efficient equipment, or start large-scale introduction of renewable (alternative) sources of energy (heat pumps, wind power, solar collectors, biomass).
Unfortunately, an informed decision is very difficult to be made due to lack of valid data based on science about new technologies, supported by operating experience. At the energy conferences and seminars dedicated to energy efficiency issues, contradictory and often mutually exclusive information is shared with the purpose to promote definite equipment at the market. Systematic analysis of the fuel and energy complex is absent not only due to intense competition, but also on account of the sharply decreasing level of professionalism in science, technology, production and operation areas. Considering the most often offers for energy crisis recovery, it is necessary to note the following: replacement of natural gas with alternative fuels at some facilities is completely appropriate, indeed, however in particular cases only. For example, transfer of gas boilers to combustion of sawdust that is a waste product at woodworking enterprises or heating of pigsty or poultry farms, where straw excess may remain after preparation of feed for livestock. However, appliance of these solutions in power industry seems to be at least unconsidered.
Of particular note is the program for heat pumps introduction. A heat pump can be very effective in a number of cases, if there arise problems with heating at a village or a company that are rather remote from centralized fuel supply (absent gas pipeline or roads to supply liquid or solid fuel) and if there is a need to heat with electricity. In that case, heat pumps can be 2-4 times efficient (subject to actual conditions) and produce thermal energy at 1 kW of consumed electricity. But we do not mean gas savings as a considerable part of the electricity produced by thermal power plants, where variety of fuels including natural gas is used. Moreover, generation of 1 kW of electricity requires at least 4-5 kW of energy consumption (due to the losses at generation and transportation). The equipment (heat pumps) is usually expensive and imported. Its stated payback period ranges between 10 to 20 years without the discount. Heat use from sewage collector is an effective option. It reduces thermal pollution of water bodies.
Besides, transfer of a substantial part of the equipment to alternative fuel requires huge capital investments that are simply difficult to involve today in conditions of economic crisis. It's worth noting that the widespread use of alternative fuel would immediately increase the fuel price to the level of gas prices. Therefore, existing economic feasibility will rapidly be leveled.
In this regard, let us recall that the USSR carried out extensive and successful industrial trials of coal gasification, including underground gasification . Today, there has been some progress in restoring attention to the issue. Gasification of coal well matches with developed gas transportation system. The use of coalmine methane has also great prospects .
For sure, price advance for energy carriers will continue, as the global economy recovers and eliminate cheap fuel. In this regard, energy-saving technologies, widely introduced in the West, play the most important role in economic growth. Specific fuel consumption for heat generation in former Soviet Union countries is several times lower than in advance European countries. Huge amount of funds is required for the purchase of new equipment, as it hasn’t been updated for many years.
So what has to be done? Which is the way out? The solution was found by mindful experienced managers via trail-and-error approach. It is necessary to preserve the existing infrastructure (equipment, personnel, system of maintenance, etc.), that is natural for our society, and develop actions to improve its energy efficiency. Today, there is a number of traditional approaches to reduce energy costs. They are decrease of heat losses in residential and industrial premises and in transportation networks of heat and power, heat recovery of flue gases, condensation plants at the outlets of fire engineering facilities, replacement of existing processes with new and more modern, etc.
Energy facilities at housing and communal sector face particularly acute problems in energy savings. Grand debates were launched regarding individual and district heating. However, before making an informed science-based decision, massive transfer to individual heating solutions and destruction of district heating infrastructure is allowed. These processes are particularly uncontrolled in Western Ukraine (up to 80% in some cities). The natural increase in the use of individual heating will lead to reveals of all its disadvantages compared to district heating. The cost per unit of heat generated by a large boiler house is significantly lower than small individual boilers. A lot of environmental issues arise due to the high level of emissions (CO, CO2, NOx, etc.) and proximity of the emission of sources to the residential buildings.
Training system for personal that performs the control and maintenance of fire and explosive facilities in district heating has been developed during decades. Greater number of professionals will be required to service individual heating systems (lack of who is incredibly significant for district heating systems). The issues will matter a consumer personally. Money stringency, of course, will make people save on expensive services that will inevitably lead to widespread explosive situation. Arrangements for heating of attics, basements, porches and similar facilities remains unclear. Integrity of buildings and safety of residents is highly dependent on the above issues.
District heating is criticized, while individual heating is supported not for the effectiveness of the latter. The reason is that there is a plan to import massively obsolete, cheaper, and not always adapted to our operating conditions equipment as illegal method of earnings for those who provide its extensive promotion in our market.
Those, who protrude the disadvantages of district heating, keep silent about the fact that endless discussions about the need to improve the efficiency of heating equipment are very poorly implemented in the last 20 years.
However, the progressive scientific idea and highly qualified specialists still exist and their developments remain up to the latest world standards. Heat-and-Power Engineering Department at the National Technical University of Ukraine "Kyiv Polytechnic Institute" (Kyiv) worked out several developments. Any European country could be proud of them. First of all, it is a new principle of energy storage without any analogues in the global science in terms of fuel efficiency in physics, and an original approach in physical terms of such processes. The development belongs to the outstanding scientist V. Yeroshenko Ph.D. and as a result, almost perfect mechanical energy accumulation is possible now. Contact water heaters are efficient and the least resource-demanding compared to other similar existing devices. They were developed by A. Korolevich Ph.D. and successfully operate in number of facilities in Ukraine, Russia, Belarus and Kazakhstan. Unique waste heat recovery of flue gases on heat pipes was designed by A. Gershuni Ph.D. The technology was previously used only in space vehicles, but now it is introduced at hundreds of boilers Ukraine and CIS countries. And of course, stream-niche technology of fuel combustion (SNT-technology) that was developed based on the researches  conducted at the Laboratory of Burning at Heat-and-Power Engineering Department at NTUU “KPI”. It is the only universal burning gaseous fuels technology as of today. Promotion and further research of the technology is passed to ‘Production Association ‘Stream-Niche Technology’ (Kiev).
Today, combustion in fire engineering facilities (FEF) is very wide: boilers, furnaces, dry kilns, combustion chambers etc.; in different sectors (rocket production, aviation, manufacturing industry, heating, hot water supply, agriculture, etc.)
Modern devices in terms of construction practically are being ceased to improve. Currently, the following parameters are well-established: diameters of furnace-wall tubes, furnace screening ratio, furnace dimension ratio, amount of twist of air blast in BD and other. Separate attempts to change usually do not lead to positive results. For example, reduction of the diameters of furnace-wall tubes (tried to be done at some boiler making companies) and increased their number and heat-absorbing surface on the one hand, increased hydraulic resistance in path for the working fluid on the other hand. Basic energy effective measures for improvements in economic feasibility, environmental safety and reliability are being associated with the arrangement of burning processes, heat recovery of flue gases, improvement of heat insulation, frequency converters, etc.
Based on the vast global experience with different types of fuel for a wide range of needs, hundreds of burner devices (BD) appeared and the main components of combustion process: mixture formation, boiler start-up, flame stabilization, fuel mixture burnout. Well-known institutions such as JSC “Scientific Production Association for Research and Design of Power Equipment named after I.I. Polzunova”, Russian Thermo Technical Institute, Central Institute of Aviation Motors, Kyiv Polytechnic Institute, Kazan Aviation Institute, Kuibyshev (Samara) Aviation Institute and other have intensively studied the BD workflow elements, which make a complex physical-chemical process. Therefore, there exist more than 1,000 types of BDs and the only is recognized as a method of BD calculation. It is Y. Ivanov’s method, which was not widespread, but had one undisputed principle about the necessity of effective distribution of fuel in a stream of oxidant flow structure, not supported by any research of flow structure and mixing. Unfortunately, we can state the fact that today the serious researches on BD working process and combustion technology creating are minimized in the former Soviet Union counties and abroad too. The emphasis is on experimental proof and powerful automation. Unreasonably high expectations are also placed on mathematical modelling of the complex process. However, tangible results in the creation of high-performance technology are not expected in this area in the near future.
Laboratory of burning at KPI, established by V. Khrystych, took one of the leading places among research centers. Unlike others, the twist flow of oxidant, bluff bodies as stabilizers and various options for supply stream fuel were studied there. By the mid-70s of the last century, almost all possible aerodynamic schemes for fuel and oxidant supply were studied. However, main approaches to create combustion technology were not identified. BDs did not meet the common requirements for economic feasibility, environmental safety and reliability both in the laboratory, and in the world. As it turned out later, main disadvantages of BDs were defined by the instability of aerodynamic flow structure. Moreover, contrary to conventional wisdom, gas is very difficult to be burnt in highly effective manner due to high point of ignition — 650-750°C, narrow volume density for fuel components — 5-15% and very low flame spread (max 0.5 m/s). The fact along with the complexity of aerothermochemistry in the process was complicated by a universal combustion technology that wholly comply with the requirements of economic feasibility, environmental safety and reliability of a fire engineering facility.
Only from the beginning of the 80s, the study of complex reacting flows in the near wake behind the stream system in cross-flow were constructed methodologically correct. They have identified fundamental principles of BD workflow, unknown at that time. A stream-niche system combines a stream system of fuel, which crosses by the flow of oxidant and niche space downstream the flow . Based on stream-niche system, it turned out possible to create a BD with a stable aerodynamic structure and self-similar to velocity and concentration fields within areas of combustion stabilization. In the late 80s, the stream-niche mixing system and flame stabilization were secured by USSR copyright certificates.
In the early 90s, SNT was successfully tested on furnaces, boilers, combustion chambers of gas turbines, heaters, etc. . At that period, intensive experimental and analytical studies were carried out, which allowed to define the basic postulates of the technology (rational distribution of fuel in a stream of oxidant, creation of a stable aerodynamic structure self-similar process of mixing, thermal preparation of the fuel mixture, self-cooling etc.). In the late 90s, both the technology, and the burner were registered as an invention in Ukraine and Eurasian countries. Today, SNT is the only universal combustion technology extensively tested on all types of BD .
These conditions provide complete combustion of gas (no CO emissions). Fuel mixture that passes through the burner is close to stoichiometry. It provides NOx emissions within the existing rules with high quality of mixing. These results are a parameter to determine the role of the efficient burning process in a BD.DKVR boilers have been in operation for 20-40 years with lowered technical parameters and now are burnt out with gas pressure 0.5-2 mm WC, steadily work on 5-10% nominal loads, with efficiency range of 93-96% after SNT upgrading. Boilers operate reliably without air mover due to combustion chamber draft. NOx emissions with a=1 decrease to 100 mg/m3. As the SNT-type BD is direct-flow, the flue space has no huge vortices and flame impingement. Thus, in agreement with the manufacturer, the protective side walls are removed, that improves the thermal condition of the pipes and reduces corrosive wear of pipes and collectors ends. An obvious conclusion offers itself — locally produced appliances are reliable, serviceable and our personnel is familiar with its characteristics; besides, it is highly competitive with modern imported technologies.
Photo 1. Installation of SNT-type BD on PTVM-30 boilerThe photo 1 depicts SNT-type burner on PTVM -30 boiler. Burners are burnt at 1-3 mm WC pressure, all 6 burners of boiler operates at 2-40 Gcal/h without shutdown of BD. The boiler can start burning without a fan and a smoke exhauster by upward pull, and therefore, gain power to 12-15 Gcal.
Photo 2. Installation of SNT-type BD on PTVM-50 boilerThe photo 2 shows the boiler PTVM-50. SNT-type BDs are installed in regular portholes. Burners start burning at a low gas pressure. Process of stabilization is carried out at operation of all 12 burners. Disconnection of BD at lower power of boiler is highly undesirable, because it leads to stratification of temperature in the combustion space and increase excess air coefficient in the boiler.
Photo 3. SNT- type BD on TP-170 boiler
The photo shows the upgrade of TP-170 boiler. BD capacity is 30 MW and it starts burning at 4 mm WC pressure.
The versatility of stream-niche technology reveals in solving a number of technical and technological problems in power engineering. One of the tasks is drying of lining after the repair of portholes, etc. Thus, it is necessary to maintain the required level of temperature and uniformity of gas temperature load that surrounds the drained surface, otherwise the moisture boils inside the lining and violates its integrity. In practice, meter wooden beams are loaded in a boiler for drying. Such a regulated way is inconvenient, it takes time to dry the object (several weeks) and drying quality is poor. First drying of boilers (PTVM-30) with a SNT-type BD was carried in Sevastopol city. All 6 burners started burning at 2-3 mm WC pressure. The fact provided the average temperature level in the furnace (100 °C) and 3 boilers had been dried in 3 days.
We would like specially focus on the huge contribution to the development and promotion of SNT leading scientists at the Institute of Engineering Thermal physics of National Academy of Sciences of Ukraine, especially A. Dolinskiy, member of the National Academy of Sciences and N. Fialko, associate member of the National Academy of Sciences.Currently, the world power engineering requires services of the company that bring together a full range of activities from a site research to its turnkey with subsequent servicing in order to introduce efficient rehabilitation. Research, Development and Production Company SNT is an obvious example with available experts in the area of burning process, provides a full cycle rehabilitation of a fire engineering facility (picture 2).