RU2662259C2 - Thermal power station with orc-module circuit and with heat pump and method of its work - Google Patents

Abstract

FIELD: power industry.

SUBSTANCE: thermal power station with steam turbine plant (ORC-module) on a low-boiling energy carrier (LBEC), containing a thermal oil boiler, the ORC-module including a steam generator in the form of a shell-and-tube heat exchanger, consisting of a shell and a tube system, a turbine on steam LBEC with an electric generator, a condenser of the ORC-module, a condensate reservoir and pumps, an absorption bromide-lithium heat pump, the generator of which is included in the closed circuit of the boiler, an evaporator which is included in the circuit of the condenser of the ORC-module, additionally contains a condensing heat exchanger housed in a duct behind the boiler, an input to the tube system is connected to the condenser of the ORC-module, and an output - to an input of an intertubular space of the steam generator module. When the thermal power station is in operation, the condensate of the low-boiling energy carrier from the ORC-module condenser is sent to the condensing heat exchanger tube system, from where the heated condensate is supplied to the intertubular space of the steam generator module, and from there the resulting LBEC steam is directed to the turbine of the module after separation.

EFFECT: invention makes it possible to increase the thermal efficiency and the generation of electricity by maximizing the use of fuel through the deep utilisation of the heat of the exhaust combustion products.

3 cl, 4 dwg

Description

The invention relates to small and medium-sized energy, in particular to decentralized energy, to combined energy complexes generating electric and thermal energy, in particular, generating electricity from the organic Rankine cycle (ORC cycle) on low-boiling energy carriers, NKE [M.I. Greenman, V.A. Fomin. Prospects for the use of power plants with low boiling fluids. “Heat Supply News”, No. 7, 2010; A.N. Pancakes. "Improving the efficiency of heat and electricity generation using binary power plants with ORC modules." Presentation. NPO St. Petersburg Electrotechnical Company. 2014. On the rights of the manuscript (analogues of the device and method)]. The invention also relates to installations with heat pumps for utilization and heat generation [E.G. Shadek, B.I. Marshak et al. Deep utilization of waste heat from heat generators. "Industrial and heating boiler rooms and mini-thermal power plants." No. 2 (23), 2014, p. 36-40 (analogue); E.G. Shadek, A.N. Blinov et al. Trigenerational energy complex on low-boiling coolants. “Energy Saving”, No. 5, 2015, p. 40-45 (prototype)].

The objective of the invention is the creation of energy-efficient, economical and environmentally friendly thermal power plants (mini-CHP) of small and medium power on virtually any type of fuel, including local (wood waste, biomass, etc.), for a decentralized autonomous energy supply facilities.

The invention includes the features contained in the known solutions, where the steam generator is made in the form of a shell-and-tube heat exchanger containing a housing and a pipe system, the heating coolant (GT) passing inside the pipe system located in the volume of the NCE [M.I. Greenman, V.A. Fomin]. There are also known installations of deep utilization (GI) of the heat of combustion products (PS), for example boilers, including an absorption bromide-lithium heat pump, ABTN, and a condensing heat exchanger-utilizer (CT) in the flue behind the boiler, connected to the ABTN evaporator, in which the exhaust gases cooled below the dew point, the water vapor contained in them condenses [E.G. Shadek, B.I. Marshak. Deep utilization of heat from the waste gases of heat generators. "Industrial and heating boiler rooms and mini-thermal power plants." No. 2 (23), 2014, p. 36-40 (analogue)].

The closest to the proposed solution can be considered "Trigeneration energy complex on low-boiling coolants" [E.G. Shadek, A.N. Pancakes and others.]. The complex contains a thermal oil boiler, an ORC module with a set of standard equipment. The module steam generator is a tubular heat exchanger built into the tail of the boiler, and is, in essence, an economizer — an exhaust gas heat exchanger for heating and evaporating NCE with the supply of the obtained NCE steam to the module turbine. The complex is additionally equipped with a heat pump, ABTN, the generator of which is included in the closed circuit of the boiler, the evaporator ABTN is in the circuit of the module condenser, and heat exchangers for heating working fluids are included in the heat transfer circuit of ABTN (heating NKE, etc.).

The weak side of this technical solution is the reduction in the capabilities and quality of regulation of the thermal operation of the boiler and the steam generator separately and the system as a whole due to the layout of both in a single wiring, their interdependence.

The steam generator of the ORC circuit in known installations is located in the module equipment kit in a single housing or it is installed separately at various points in the technological scheme of the facility.

Thus, in comparison with the prefabricated prototype, the proposed system contains known features (restrictive part):

- thermal oil boiler;

- a steam generator, in the annulus of which the working medium circulates - NCE, and the heating coolant passes through the pipes of the pipe system;

- ORC module with a set of equipment;

- ABTN, the generator of which is included in the closed circuit of the boiler, the evaporator - in the condenser circuit of the ORC module; heat exchangers are integrated into the heat sink circuit [prototype];

- a condensation heat exchanger (CT) in the flue behind the boiler, containing a pipe system with a unit for collecting, discharging and processing the condensate of water vapor contained in the substation.

The method includes a well-known feature, consisting in the fact that in the CT the combustion products are cooled to a temperature of 10-20 ° C below the dew point, the condensate is collected and discharged.

Single-stage absorption lithium bromide heat pumps (ABTN) are used due to their obvious advantages over compression ones. ABTN as a part of the proposed TPP serves as a cold generator for the ORC module capacitor and a heat source in the temperature range of communal heat supply (heating, hot water) - 60/90 ° С; this heat is removed to the condenser-absorber circuit (KA) and transferred to the consumer.

Objectives of the invention:

1) increasing thermal efficiency and generating electricity module due to the maximum use of fuel - deep utilization of heat of the outgoing substations;

2) improvement of technical and economic indicators (TECs) of the process and equipment, reliability and stability by cooling the module condenser in the ABTN evaporator circuit instead of expensive and bulky air fan coolers and providing economical heat removal independent of weather conditions;

3) ensuring the ecological purity of the process as a result of lowering the temperature and almost completely suppressing the effects of toxic oxides in the presence of water vapor in the PS.

These goals are achieved thanks to the distinguishing features of the invention:

1) the entrance to the pipe system of the condensing heat exchanger, CT, is connected to the condenser of the ORC module, and the output is connected to the entrance to the annulus of the steam generator of the module;

2) the thermal oil boiler of the TPP is connected in parallel in two closed circuits in which the heating coolant - oil circulates: the first circuit is the boiler - generator ABTN and the second - the boiler - pipe system of the steam generator of the ORC module;

3) the method of operation of the TPP, characterized in that the condensate from the condenser of the ORC module is sent to the CT pipe system, from where the heated NCE condensate is fed to the entrance to the annulus of the steam generator, and from there the obtained NCE steam is sent to the turbine after separation.

The design and operation of the TPP are visible from the drawings, which depict the following.

FIG. 1. The technological scheme of thermal power plants. Boiler, steam generator, gas path in longitudinal section.

FIG. 2. Section AA in FIG. one.

FIG. 3. Bypass of the deep recycling unit.

FIG. 4. Section BB in FIG. 3.

In the drawings, the positions are indicated:

1 - thermal oil boiler. 2, 3 - direct and reverse collectors of the heating coolant, GT. 4 - fuel combustion unit. 5 - fuel supply unit. 6 - the main flue. 7 - bypass (bypass channel). 8 - flue gas filter. 9 - condensation heat exchanger, CT: unit of deep utilization (GI) of the heat of combustion products (PS), 10 - the body of the GI unit. 11 - CT housing cover. 12, 13 - inlet and outlet pipes of the NKE of the GU unit with regulatory bodies. 14 - drip tray. 15 - smoke exhaust. 16 - pan and reservoir of water condensate. 17, 19 - tanks of contaminated and stock condensate. 18, 20 - drainage and condensate pumps of water condensate. 21 - flow controller. 22 - gas path. 23 - chimney. 24, 25 - gate (throttle valves) in the main duct and bypass. 26 - steam generator circuit ORC. 27, 28 - inlet and outlet nozzles of the heating coolant, GT. 29, 46 - circulation pumps in the contours of the GT. 30, 31 - input and output pipes of the NKE of the steam generator. 32 - pipe system of the steam generator. 33 - pipe boards. 34 - separator. 35 - turbine circuit ORC. 36 - electric generator. 37 - module capacitor. 38 - tank condensate NKE. 39 - condensate pump NKE. 40 - ABTN. 41 - circulation pumps of ABTN circuits. 42 - fuel (heating) circuit ABTN. 43-45 - heat exchangers in the circuit 42 for heating oil, network water, blast air, respectively. 47 - blower fan.

The heating coolant (GT) - oil - circulates from direct collector 2 to return 3 through parallel closed heating circuits of the ABTN generator (first circuit) and steam generator 26 (second). The temperature of oil heating in the boiler is up to 300 ° С, according to the conditions of work with the highest operating temperatures of NKE, for example, terminol.

Housing 10 CT rectangular, metal, thermally insulated, with a removable cover 11 (Fig. 1 and 4) for installation, repair, replacement, etc. The deep recycling unit 9 is installed at the outlet of the boiler, on the suction side. The design is mounted on the flange joints of the end surfaces of the metal gas duct and the housing 10 and along the plane of the horizontal connector between the housing 10 and the cover 11. The joints of the flanges are hermetically insulated by heat-resistant materials (insulation, sealants). Removable can be a side wall that is free of nozzles.

The PS flow from the boiler 1 enters the body 10 of the condensing heat exchanger 9, passes in the annulus, through the drip trap 14 and then under the draft of the smoke exhauster 15 — along the path 22 into the chimney 23. It is practically impossible to completely “drain” the condensate, the remaining amount of moisture is trapped in the droplet eliminator 14 (grilles, louvres, nets, self-cleaning elements), but even so, there is a slight splashing noise (up to 5%) into the gas path. The gas duct, gas path, casing, pipe system are made of corrosion-resistant materials, coatings, stainless steels, plastics, bimetal pipes with rolled aluminum fins, polymer coatings, etc. are used for the pipe system, which ensures sufficient reliability and durability of service - this common practice.

In FIG. 1 shows, by way of example, a pipe system 9 of a coil type. The type, device, design of heat-exchange surfaces can be different: for example, compact regenerators of the RG-10 type, SPC “Anode” with a heat-exchange surface made of coils with a small bending radius, etc. Heater sections are also recommended as heat exchange units for the GU unit, for example, of the type VNV123-412-50ATZ of the Calorifer Plant, Kostroma. The choice of the layout of the sections and the connections for water and gases allow you to vary and ensure the speeds of water and gases in the recommended range of 1-4 m / s.

The dew point temperature Т _Р for PS of natural gas is about 50-55 ° С, approximately the same range Т _Р for PS of wood waste (DO). In the inventive scheme, the condenser 37 is cooled in the circuit of the ABTN evaporator with cooling water temperatures, inlet / outlet, 30/25 ° C, the temperature of the NCE condensate from the condenser is about 30-35 ° C. When NCE condensate is supplied with such a temperature (for butane, isobutane, pentane, etc.) in the pipe system 9, the PS is deeply cooled below the temperature Т _Р , the PS is cooled and the water vapor contained in the blast air is condensed and from the combustion of fuel hydrocarbons, with the release of hidden heat of evaporation, i.e. deep disposal (GI). Moreover, along with the physical (40-45% of the total heat content of PS), the heat of vaporization is utilized (60-55%).

The temperature level T ₂ behind node 9 is unambiguously determined by the condition of condensation of water vapor in the leaving PS, the value of T ₂ should be lower than the temperature T _{P of} the dew point of the fuel combustion products by 10-20 ° C, i.e. about 40 ° C.

All recyclable heat is transferred to the ORC circuit, increasing the module's electrical power and thermal efficiency. Condensate separated from the PS settles on the pipe surfaces 9, is discharged into the sump and tank 16, from there by gravity to the tank 17 and is pumped to the condensate stock tank 19 by pump 18. From here, the pump 20 through the flow controller 21, the water condensate is fed to the treatment site.

After contacting natural gas with PS, the condensate retains high quality and needs simple and inexpensive treatment — decarbonization (and not always that) and degassing. If condensate is not used, it is drained into the sewer.

In the unit for the collection and processing of condensate - paragraphs. 16-21 - use the well-known standard equipment of deep utilization systems [E.G. Shadek, B.I. Marshak et al.].

The system produces a large amount of excess water, so it does not need recharge. This factor is important in areas with water scarcity.

The scheme provides for bypassing the unit GU 9, i.e. bypassing part or all of the PS flow from the boiler in addition to node 9 (Fig. 1, 3). By bypassing, the temperature of the substation behind node 9 is maintained in the desired range, 60-80 ° C, in order to prevent condensation in the gas path and especially in the chimney (icing, barrel shutoff in winter). The degree of bypassing is regulated using gates (throttle valves) on the main duct 24 and bypass 25. It is usually from 15 to 25%. Bypassing degrades all process performance. So, according to the calculated data, the quantity of utilized heat Q _UE decreases by 18-20%, the heating surface increases by 10-15% in the CT. The optimal mode is to work with bypassing in the cold season, and in the summer, when there is no danger of condensation, without it.

The annular space of the steam generator 26 is partitioned by tube boards 33 into sections through which the NKE circulates in a zigzag manner from the first section with the inlet pipe 30 to the last with the outlet pipe 31. The last section serves as a superheater and is equipped with a steam separator 34 with a mesh demistor.

Superheated and separated in the separator steam through the exhaust pipe 31 is fed to the turbine 35.

The rest of the equipment (paragraphs 36-39) of the ORC circuit is similar to that of the known analogues. In the proposed scheme, there is no recuperator, the NKE condensate heating function is performed by node 9. However, in some cases (various modes, NKE brands, etc.), it may turn out to be rational and included in the system.

The nozzles are equipped with control units (regulatory bodies - valves with actuator, in the general case: stop, regulating, return, safety, etc., instrumentation and A.). These nodes are integrated into a single automatic control system (ACS) of an energy facility, which operates according to specified programs, supporting optimal process parameters (pressure, temperature, flow rates, etc.). The circuit for connecting ABTN to the circuit is visible from FIG. one.

The condenser 37 of the module is included in the closed refrigeration circuit AND of the ABTN evaporator, in which water circulates with a temperature of 30/25 ° C (inlet / outlet). The NCE condensate is discharged into the tank 38, and from there it is pumped to the PG 9 unit. The generator ABTN is included in the closed circuit of the boiler with the coolant circulating in it - oil. In the heat sink (and for the external consumer - heating) circuit 42 ABTN “condenser - absorber”, KA, water with a temperature of 60/90 ° C (in / out) circulates, heat exchangers 43-45 for heating oil, network water are included in it (heat supply - heating, domestic hot water, technological needs, etc.) and blast air (if appropriate). The network water heater 44 serves the heating network and the hot water supply of the consumer (for example, a village) with a heating temperature schedule of 90/60 ° C. For a heating network of limited extent, this is quite enough. Thermal power Q _T ABTN i.e. circuit KA, calculated according to the maximum demand in the winter. In the summer, year-round loads of domestic hot water, heating oil, air, etc. remain, and excess heat is discharged into the cooling tower, air condenser, etc. (not shown).

The ratio of heat generated in ABTN, in the circuit K-A, Q _T to the spent in the generator Q _G Q _T / Q _G = 1.65-1.75. As a source of medium temperature (up to 90 ° С) heat, ABTN is 1.65-1.75 times more economical than a conventional fuel boiler. ABTN balance equation: Q _T = Q _HOL + Q _G , where Q _XOL - cooling capacity of the machine; this is a net gain in the thermal balance of the system, free heat due to removal from the condenser. The real efficiency of using ABTN in the system is determined by the capabilities and degree of heat utilization Q _T.

The technical solution provides a choice of boiler and fuel. The boiler can be thermo-oil with oil heating up to 300 ° С (for example, in the case of using terminol) or hot water with water heating up to 145-150 ° С (for butane, isobutane, pentane, etc.), according to the requirements of NKE and ABTN heating conditions. Both those and other boilers are mass-produced - both domestic and imported. The system can work, in principle, with a boiler using any fuel: natural gas, liquefied gas, generator gas, diesel and other types of fuel, including wood waste and biomass, subject to certain requirements for the cleanliness (contamination, dustiness) of combustion products, PS, and taking into account the impact on pipe surfaces. As an option, in FIG. Figures 1 and 2 show the installation in the gas duct of a filter 8 for cleaning PS from contaminants — louvres, grids, cassettes, etc., removable or self-cleaning. For generator gas obtained by processing DO, tar removal and drying are required.

Below, by way of example, a calculation model of the claimed object is shown — a TPP based on an Turboden 10 HR, Nerminol 66 ORC module [3] with the following temperature parameters (initial data), ° C: coolant to and from the evaporator 290, 146; cooling water to and from the condenser 25, 38.

Thermal capacities (amount of heat), MW: supplied with heat carrier, Q _ГЕH , 5.54 / 5.9; given to cooling water, Q _XOL , 4.4.

Power of mechanisms for own needs, N _CH = 46 kW, released electric power 1062 kW; Efficiency on electricity supply 19%.

For the circuit, the ABTN-4000 V heat pump was selected for hot water produced by OKB TEPLOSIBMASH LLC, Novosibirsk, with indicators: Q _ГЕH = 5.9, Q _XOL = 4, the heat output of the heat sink circuit of the machine Q _T = 10.2 MW (approximately equal to the sum of Q _GEH and Q _XOL ), N _CH = 12.7 kW. As you can see, ABTN (see its characteristics above) fits well into the ORC circuit.

The total required boiler capacity Q _K = 5.54 + 5.9 = 11.44 MW. The nominal efficiency of the thermal oil boiler is η _K = 0.8. We accept (with underestimation) that out of 20% of the total heat loss, an article with flue gases q ₂ accounts for 10%. For a preselected boiler heating capacity Q _K = 10 MW, q ₂ will be 0.1 × 10 = 0.1 MW (0.86 Gcal / h). On a large array of experimental and calculated data, the ratio Y of the values of utilized heat Q _UT and q ₂ , Q _UT / q ₂ was established in the range Y = Q _UT / q ₂ = 1.2-1.47 for PS temperatures in the range of 120-200 ° C, with Y increasing with decreasing temperature. For the most characteristic ratio Y = 1.47, the heat balance of PS is just: 40% - physical heat, 60% - condensation heat (coincides with the literature data, see above). Accepting (with understating) Y = 1.4, we obtain Q _YT = 1.4 × q ₂ × Q _K = 1.4 × 0.1 × 10 = 1.4 MW.

Then the required heating capacity of the boiler Q _K = 10 + 1.4 + 11.4 MW, i.e. almost equal to the given (11.44), where 1.4 MW is saved, i.e. introduced by the deep heat utilization of substation heat in unit 9. The total additional, free heat introduced into the heat balance of the station due to utilization will be the sum of Q _UT + S _COL = 1.4 + 4 = 5.4 MW.

Calculation of combustion DO (Q _H ^P = 2440 kcal / kg, air consumption for combustion V _B ⁰ = 2.8 m ³ / kg, PS output w = 3.73 m ³ / kg [MB Ravich. Simplified method of heat engineering calculations. M., Publishing House of the Academy of Sciences of the USSR, 1958, p. 24]): fuel consumption B = Q _K / Q _H ^P η _K = 8.6 Gcal / h / 2440 × 0.8 = 4406 kg / h. The output of combustion products with an air flow coefficient of α = 1.5 W = 1.5 × 3.73 × 4406 = 24650 m ³ / h. The temperature of the exhaust gases Т _УX = q ₂ / C × W = 0.86 / 0.34 × 24650 = 103 ° С, where С is the specific heat of PS DO equal to 0.34 kcal / m ³ gr.

Heat exchange conditions in the GU unit (set and accepted): substation temperatures at the inlet and outlet of the pipe system 103 and 40 ° C, NEC temperatures (ranges) 30-35 and 40-50, respectively. Knowing T _vx and asking heat transfer coefficient K _W (in SS medium to condensation conditions according to the literature and calculated data) of about 100 W / m ² c., Determine the average temperature difference Δt to calculate the heat transfer surface F and the heating heat exchanger 9.

With a station operating duration of 8000 hours per year, the amount of heat saved will be Q _EC = 37144 Gcal / year, fuel - 19029 t / year, and its cost at a price of up to 800 rubles / t - about 15 million rubles / year (the rest the initial data is the same).

As a result, we obtained the ranges of parameters (Δt = 28.5-36 ° C, F = 370-490 m ² ) and the optimal modes - with minimum values of F and maximum Q _UT and Q _EC .

The effectiveness of the proposed solution lies in the competitive advantages of the technologies used: deep utilization (GI) and heat pump (ABTN) in combination, which ensures low cost of the released heat and electricity and, therefore, the competitiveness and profitability of the project.

Reducing the temperature of gas emissions, as well as the presence of water vapor in them neutralizes the harmful effects of nitrogen oxides, making the process environmentally friendly.

The cooling of the condenser of the ORC module in the circuit of the ABTN evaporator instead of air condensers (coolers, cooling towers) gives significant savings in capital and operating costs, production space, energy consumption for own needs, it is more reliable and stable and does not depend on weather conditions, the operation of the thermal power station as a whole - more effective.

The use of the ORC-module expands the possibilities and boundaries of disposal, allows you to utilize the average potential heat of the combustion products.

Especially promising is the use of thermal power plants as a reliable economical source of energy supply for various, including local, fuel, in particular biofuels, for remote, inaccessible facilities (enterprises, settlements, towns, etc.), which is extremely important for Russia.

Claims (3)

1. Thermal power plant (TPP) with a steam turbine installation (ORC module) on a low-boiling energy carrier (NCE) containing a thermal oil boiler, an ORC module including a steam generator in the form of a shell-and-tube heat exchanger, consisting of a casing and a pipe system, a turbine on a pair of NEC with an electric generator, ORC module condenser, condensate tank and pumps, lithium bromide absorption heat pump (ABTN), the generator of which is included in the closed loop of the boiler, the evaporator is in the ORC module condenser circuit, characterized in that it contains in ha ohode condensing heat exchanger for the boiler (CT), the entrance to a pipe system which is connected to the capacitor ORC-module, and the output - to the input of the shell side of the steam generator module. 2. The thermal power plant according to claim 1, characterized in that the thermal oil boiler is connected in parallel in two closed circuits in which the heating coolant - oil circulates: a boiler - an ABTN generator and a boiler - a pipe system of an ORC module steam generator. 3. The method of operation of a thermal power plant according to claim 1 or 2, characterized in that the condensate of the low-boiling energy carrier, NCE, from the condenser of the ORC module is sent to the condensing heat exchanger pipe system, from where the heated condensate is fed to the inlet to the annulus of the module steam generator, and from there the steam obtained NCE after separation is directed to the module turbine.

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