Soojustehnika Instituut – Thermal Engineering Department
Report
BUSINESS PLAN OF MODERNISATION AND ENLARGEMENT OF AS SILLAMÄE HEATING AND POWER PLANT
TALLINN 2002
CONTENTS
Objectives………………………………………………………………………………………
1. Description of the present state of Sillamäe Heating and Power Plant……………………..
1.1 Specification of the heat scheme………………………………………………………...
1.2.Technical state of the main equipment - residual life…………………………………...
1.2.1 Specification of boilers......
1.2.2 Technical state of steam boilers......
1.2.3 Specifications of steam turbines......
1.2.4 Technical condition of turbines......
1.3 Production indices of AS Sillamäe HPP……………………………………………….
2. Description of potential energy consumers of AS Sillamäe Heating and Power Plant…...
2.1. Overview of the existing electricity market for the AS Sillamäe HPP………………..
2.1.1 AS Silmet – a plant of rare earth metals......
2.1.2 AS Silmet – a plant of rare metals......
2.1.3 AS Silmet – a plant of metals......
2.1.4 Total power demand in AS Silmet......
2.1.5 Other electricity consumers connected to the network of the Silmet Group and AS Sillamäe HPP
2.1.6 Auxiliary consumption of AS Sillamäe HPP......
2.2 Extension potential of power engineering in the AS Sillamäe HPP…………………...
3. Heat market of the AS Sillamäe HPP……………………………………………………...
4.Efficiency and operating costs of the AS Sillamäe HPP………………………………..
4.1Compared operating costs of AS Sillamäe for the summer and winter duty………..
4.2 Cost price of heat and electricity produced in the AS Sillamäe HPP………………….
5. Various concepts for the modernisation and extension of production of AS
Sillamäe HPP…………………………………………………………………………………
5.1 Transfer of AS Sillamäe HPP to gas firing, formation of production costs……………
5.2 Efficiency improvement and extension of production capacities of AS Sillamäe HPP with a combined unit based on a gas fired internal combustion engine…………………...
5.2.1 Theoretical basis for the introduction of power unit with an internal combustion engine
5.2.2 Preconditions and terms for the implementation of co-generation complex based on an internal combustion engine at the Sillamäe HPP
5.2.3 Analysis 0f the economic efficiency of CHP plant based on the Caterpillar internal combustion engine
Abstract……………………………………………………………………………………….
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Objectives
Trends and changes in the energy policy
During the last years essential changes have taken and are still taking place both in the economic and engineering environment of the energy sector:
- In the Estonian energy network prices on electricity (tariffs) for all consumer groups have increased significantly. Considering the necessary investments in supply networks and for the rehabilitation of the AS Narva Power Plants, ongoing increase of tariffs could be clearly observed.
- Environmental requirements will become stricter. The present environmental taxes for the energy use of oil shale make ca 20 EEK per ton. The annual 10-20% increase of environmental taxes is forecasted.
- The useful life of existing power plants is being exhausted. The Narva Power Plants where ca 85-90 % of electric power consumed in Estonia is generated were built in 1959-1969. The total installed capacity was over 3000 MW. Rehabilitation of two energy blocks has been planned (total capacity of 400 MW), but at the same time closing of the so-called 1st and 2nd order of the Balti Power Plant has been decided, which means the decrease of installed capacity for ca 600 MW. Considering the above and also consumption prognoses for Estonia where the estimated annual growth of electricity demand will make 0.5-1.5 % and taking into account the environmental restrictions to oil shale power engineering, shortfall of peak power not invested in additional capacities could be expected in Estonia from 2008.
- The CHP units or so-called co-generation plants have made significant development during the last years. Their cost has reduced and efficiency factors improved. In order to follow environmental agreements and promote energy saving, many countries, including the European Union, have made decisions in energy policy that promote the development of co-generation. For example in the EU countries, the power industry is oriented from monopolist centralized electricity production to open electricity market and the European Commission considers it realistic that to the year 2010 the electric power generated in CHP plants of the EU countries will make 18% from the total power output.
Objectives for the modernization and extension of AS Sillamäe HPP
The present AS Sillamäe Heating and Power Plant has developed based on the RAS Silmet Heating and Power Plant commissioned in 1952-53. Since its commissioning in 1950-ies the power plant has been modernized, improved. In the conditions of economic depression of the beginning of 1990-ies the amount of heat power bought from the heating and power plant decreased; no options for selling electricity were available. At the same time the capacities of repair work decreased and as a result, the reliability of equipment etc. deteriorated. To the present time the objectives of the heating and power plant as well as market conditions have changed significantly. Since 1997 after RAS Silmet surpassed economic depression, planned repair for boilers was introduced and boiler routine testing reintroduced, step-by-step reliability of five oil shale boilers has been provided. This in turn allows supplying both the traditional consumers of the power plant with heat and electricity and selling electricity to the independent Narva Electrical Network. The result can be seen in the fact that in the heating period of 1999-2000, for example, 3027 MWh of electric power was sold to the Narva Electrical Network.
Aimed at increasing electricity co-generation with heat, the process flow diagram of the condenser of steam turbine AP-6 has been changed. The flow section of turbine was reconstructed in connection with its conversion to operating in the insufficient underpressure regime (the blades of two last stages were demounted). The design of condenser was not changed. In summer the condenser is cooled with seawater, in winter with the water from the DH return flow.
The maximum available capacity at the heating period of 1999/2000 was 10 MW. At the same time no water heating boilers were used and thus the auxiliary power consumption of the heating and power plant decreased for 500 kW.
In connection with emerging of a potential electricity market, the possibility to sell electricity to the Narva Electrical Network and also with the future target to provide heat and electricity supply to the existing consumers in the near future the following tasks have been set to the AS Sillamäe HPP:
- To provide competitiveness on the electricity market to be opened
- To increase sales and profitability from the energy sales.
Means and options must be analysed and found to solve the problems related to increasing the available electrical output capacity of AS Sillamäe HPP and improvement of the efficiency of co-generation plant.
1. Description of the present state of Sillamäe Heating and Power Plant
1.1 Specification of the heat scheme
Figure 1.1 shows the schematic diagram of the heat scheme of AS Sillamäe Heating and Power Plant. The river water passes two stage cleaning cycle – mechanical and in Na-cation exchanger (1). After the treatment the quality of boiler supply water anticipated by the standard will be provided. Chemically cleaned water is directed either to the deaerator of make-up water of the heat distribution network (not shown in the figure) or deaerator of the boilers supply water 2 (2 units in total) where O2 and CO2 will be removed from the water. In the course of degasification water temperature will rise up to 102°C. The pressure in the deaerator is 1.2 bars. Clean condensate from the turbine condenser and drainage tanks is also discharged to the deaerator. From the deaerator supply water is directed to the supply pumps of boilers (3) and via the high-pressure preheater (4) to the steam boilers (5). The steam produced in boilers with the parameters of p=35 bar and t=425°C is directed via the collectors A, Б, B to the turbines 6 and 7 or to the reduction coolers 8 and 9. Electricity generated in the generator is directed via cables to the busbars of the main switchgear and then via the network on to the consumers. The backpressure unit or reduction cooler (9) steam of the turbine (7, No 1) with the pressure of 5 bars is delivered to the consumers of technological steam (1,7) high-pressure preheater of supply water (4) or the peak preheater of network water (11). Steam from the backpressure unit or reduction cooler (8) of the turbine (6) with the pressure of 1.2 bars is directed to the deaerator or main preheater of network water (10). If the turbine No 1 (7) runs on an insufficient underpressure regime, the distribution network water returned from circulation (15) is preheated in the turbine condenser (13). Water from the heat distribution network circulates in the closed circuit collector of: water returned from the distribution network (15) → condenser (13) → pumps of network water (12) → pumps of network water (11, 10) → collector of water to the distribution network (16). The condensate from preheaters (10) is pumped to deaerators (2), but from preheaters (11) to the condensate tank and from there on, if necessary, to different deaerators. The condensate from outside consumers and heavy fuel oil unit is not returned. The loss of condensate and network water is covered with chemically cleaned water, which is directed to the deaerator. The waste heat of the continuous blowdown separator of boilers is used for preheating untreated water in the chemical water treatment cycle. The condensate is discharged to the drainage system.
1
Fig. 1.1. The principal heat scheme of Sillamäe HPP
Denotes: / 6. turbo generator АПР-6 (6MW) / 13. condenser / Steam parameters:chemical water treatment / 7. turbo generator АП-6 (6MW) / 14. water boilers / Superheated steam 420°C/35bar
deaerators / 8. reduction cooling unit 40/1,2 / 15. collector of return water
supply pumps / 9. . reduction cooling unit 40/5 / 16. collector of water to the DH network / Turbine backpressure steam 190°C/5bar
high-pressure preheater of supply water steam boilers / 10, 11heater of network water / 17. steam consumers / Turbine backpressure steam 120°C/1,2bar
5. steam boilers 3ТП-35-40, 2С-3540 / 12. feedwater pumps
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1.2.Technical state of the main equipment - residual life
1.2.1 Specification of boilers
In the AS Sillamäe Heating and Power Plant there are 5 pulverized oil shale fired steam boilers and 2 gas or heavy fuel oil based water-heating boilers. The first three oil shale boilers (No 1, 2 and3) are of ΤΠ-35 type while the rest two units (No 4 and 5) of C-35-40 type. The water heating boilers (No 6 and 7) are of ΠTBM-30 type.
Boilers ΤΠ-35 (No 1-3)
The manufacturer’s rating of ΤΠ-35 type boilers is 35 t/h of superheated steam at the pressure of 35 bars and temperature 425°C. The pressure in the drum is 42 bars and temperature of feedwater 130°C.
The boiler designed and built in the Taganrog Boiler Manufacturing Plant is an upright tubular boiler with a single drum. The furnace is totally water-cooled. The boiler is equipped with two axial hammer mills ШMA-1300/950/735. The vortex burners are installed in front of the furnace. The heavy fuel oil start-up nozzles are located on sidewalls. The positioning of convective heating surfaces has a certain peculiarity – the 3rd stage of a 3-stage superheater is installed in the downtake along the flue gas flow. In the lower part of downtake before the gas tract of economizer and air preheater there is a sedimentation chamber for capturing fly ash. Each unit has one Д-20 type exhaust fan and one ВД-10-13H type air fan. According to the project, the temperature of hot air is 277°C and that of flue gases 175°C.
Boilers C-35-40 (No 4-5)
The manufacturer’s rating of these boilers is 35 t/h for the superheated steam at the pressure of 35 bars and temperature of 425°C. Pressure in the drum is 40 bars and temperature of feedwater 130°C.
The boiler designed in the Belgorod Pilot Plant is an upright tubular boiler with a single drum.
The size of furnace and arrangement of mills and burners is similar to the ΤΠ-35 type.
A two-stage superheater is installed in the inclined flue behind the festoon. This flue ends with an inertial sedimentation chamber where the concentration of fly in the flue gas ash is reduced before the economizer. A multicyclone is located after the economizer in a separate flue gas tract before the air heater. The C-35-40 type boilers are equipped with two tangential ШMT 1000/1950 type hammer mills. The exhaust fan is of the same type as on the ΤΠ-35 boiler while the air fan ВД-12-13H has higher capacity. According to the project, the temperature of hot air must be 280°C and that of flue gases 170°C.
To April 1, 2000 the running time of boilers is the following:
Boiler No 1 – 2898320 h;
Boiler No 2 – 191575 h;
Boiler No 3 – 277249 h;
Boiler No 4 – 149962 h;
Boiler No 5 –119613 h.
Ash removal system – hydraulic with bagger pumps. For removal circulating water clarified in ash fields is used. The ash and slag is stored in the ash field 1.5 km away from the plant. The clarified water is returned to the power plant from the ash field pumping station.
Final cleaning of flue gases takes place in the three-section precipitator of the УГ-3-24 type equipped with a prechamber.
The water heating boilers No 6 and 7 ПТВМ-30M, a uniflow tubular boiler with the capacity of 30MW. The water flow through the boiler makes up to 500 m3/h. At the rated load the flow of fuel oil is 4355 kg/h or that of gas 5200nm3/h, respectively. The boiler is equipped with six ГМГ-5,5 type burners, two ВД-12 blowers and one flue-gas exhauster Д-15,5x24.
1.2.2 Technical state of steam boilers
Reliability and efficiency of the main equipment of a power plant depend first of all on the residual life of the metal of thick-wall components and state of heating surfaces. The first depends neither on the used fuel nor on the combustion method, but on the operating variables, operating conditions and mode, properties of the unit’s metal and also its design. The residual life and state of heating surfaces of boilers result significantly from the composition of burnt fuel, gas temperature, velocity, etc. Intensive fouling and wear of oil shale boilers is first of all due to the high ash content in oil shale (~50%) and specific composition of the mineral part, which disintegrates in the combustion process and the nascent chemically active compounds are carried with flue gases to the tubes of boiler’s heating surfaces where they sulfurize under the action of SO2, which is presentin flue gases, i.e., they become mechanically strong and cannot be easily removed. This is a progressive process and lack of efficient cleaning equipment leads inevitably to shortening of boiler’s lifetime and untimely shutdown. Long-term operating practice of pulverized oil shale fired medium and high pressure boilers has shown that fouling of heating surfaces, their wear and repair are inevitable and this must be taken into consideration and accepted.
Since 1995 large-scale repair of all the boilers have been made to restore the required performance level of heating surfaces and improve boiler efficiency.
The Thermal Engineering Department of Tallinn Technical University has continuously studied the current state and technical performance of thick-wall boiler components and piping from the point of view of reliability. As a result of investigation, an evaluation report on the current state of all boiler components has been prepared, remaining operational hours up to the mandatory check-up of metal, or repair have been forecasted. As a conclusion, we can state that check-up of metal and welded seams of operated boiler heating surfaces must be made only after 50-75•103 hours on-time. (The TTU Thermal Engineering Department (ThED) has made a more detailed prognosis of on-time hours for different heating surfaces and boilers). In order to improve reliability, safe handling of the equipment and provide training for the staff, in the TTU ThED the following guidelines have been worked out for the Sillamäe SEJ:
- The guide for checking the state of metal in the components of energy units operating under pressure. Coordinated with the Technical Inspection, 03.2000;
- The guide for the technical inspection and pressure test of boilers, 11.1999;
- The regulation for the use of shale oil in low powered boilers produced in the retorting unit with solid heat carrier, 07.2000.
As a result of correct arrangement of combustion processes, optimisation of repair work and cleaning plants performance, the boiler efficiency has been improved from 79 % to 84.8% during the last years (see Figure 1.2)
Figure 1.2
1.2.3 Specifications of steam turbines
Turbine No 1
An AП-6 type single-cylinder condensing turbine with one controlled steam extraction point, built in the Nevski Machine Building Plant in 1952. Capacity 6 MW, rotation speed 3000 rpm.
Parameters of input steam:
-pressure 35 bars;
-temperature 435°C;
-maximum steam flow – 53 t/h;
-pressure of extraction steam – 5 bars;
-pressure in the condenser – 0,04 bars;
The flow section of turbine has been reconstructed due to its transfer to insufficient underpressure mode. In the summer duty, the condenser is cooled with seawater, during the heating period with water from the network.
Turbine No 2
An AПP-6 type single-cylinder backpressure turbine with one uncontrolled steam extraction point. Built in the Kaluga Turbine Building Plant in 1963. Capacity 6 MW, rotation speed 3000 rpm.
Parameters of input steam:
-pressure - 35 bars;
-temperature - 435°C;
-backpressure rating – 1.2 bars;
-pressure of extraction steam – 5 bars;
-maximum flow of backpressure steam – 40 t/h.
Maximum temperature of the used steam – 200°C
1.2.4 Technical condition of turbines
Turbine No 1
The flow section of turbine No 1 was reconstructed due to its transfer to the insufficient underpressure operation mode. (the blades of two last stages were demounted). The condenser design was not changed. In summer the condenser is cooled with seawater, in winter with the return water from the DH network.
The turbine rotor is in a good condition. On the outlet flange of turbine blades some traces of erosive wear can be observed, which is of no danger and replacement of the blades is not necessary.
The turbine quick-closing valve is also in a satisfactory condition. With the valve closed, the number of rotor turns drops from 2997 rpm →1430 rpm within 5 minutes.
The vibration speed of front and back bearings is 1.3 and 0.9 mm/s, respectively, which is essentially lower than the allowed. The turbine control system is started when the rotation speed of 2694rpm is reached. Fluctuation of the number of no-load rotations does not exceed 10 rpm. A synchronizer enables to keep to the rotation within 2790-3292 rpm. Thus the turbo generator can be synchronized (switched in the network) at a higher or lower network frequency. The non-uniformity of turbine rotation speed is 5.5%. The safety device is switched on when the rotation speed has reached 3292 rpm. The stall time for the rotor is 23 minutes.