RU2827082C1 - Method of dust preparation at thermal power plant using gas piston engine - Google Patents

Abstract

FIELD: various technological processes.

SUBSTANCE: invention relates to dust preparation, namely to systems for preparation of solid fuel for combustion in furnace devices, and can be used in power engineering, construction and other industries. Technical result is achieved by pulverization method at thermal power plant, in which crushed coal is fed into mill, where it is ground, dust-gas mixture from the mill is successively sent to a separator for screening coarse substandard dust and its return back to the mill, and fine dust is sent to the dust supply system and then to the boiler burners, a gas piston engine (GPE) is used as a mill drive, natural gas is supplied to the GPE, and the flow of exhaust gases from the GPE is directed to the boiler or to its burners, water is supplied to the cooling system of the GPE elements, where it is heated and discharged.

EFFECT: reduced use of electric energy for own needs of thermal power plants and energy saving.

1 cl, 2 dwg

Description

The invention relates to dust preparation in systems for preparing solid fuel for combustion in furnace devices and can be used in the energy and other industries where fuel, raw materials, and materials are ground.

In the accepted classification of solid fuel preparation systems for thermal power plants, individual (for one boiler) pulverization systems are distinguished with the following main elements. Raw crushed coal is fed from the bunker into a descending box, where a drying agent is directed (only hot air from the main air heater of the boiler or mixed with exhaust gases), coal with a drying agent falls into a mill, from where, due to ventilation, dust is carried out into a separator; in it, large substandard dust is sifted out and sent back to the mill for final grinding; the finished dust is either directly blown through the burners into the furnace, or it is first deposited by a cyclone into an intermediate bin of finished dust, and from there, mixed with primary air, it is sent to the burners. A synchronous electric motor serves as a drive for the rotary mechanisms of the mills.

A hammer mill is known (patent RU 2487759, IPC B02C 13/04, published 20.07.2013, bulletin No. 20), which comprises a sieve with a clamping frame and a holder, a motor, a stator frame, a rotating device, a rotor spindle, and hammer cutters. The motor is mounted on the stator frame and is connected to the mill's rotating device by means of a clutch. The rotating device, the sieve, and the sieve holder together form a grinding chamber. The rotor spindle of the rotating device is connected to the clutch. Hammers with a plurality of cutters are mounted on the rotating device. A large spacer sleeve having inner and outer edges is mounted on the rotor spindle between adjacent frame plates. Both sides of the inner edge and both sides of the outer edge are firmly fixed to the respective adjacent frame plates of the hammers, wherein the inner edge of the spacer sleeve is located on the rotor spindle, and the outer edge is at a distance from the inner side of the mounted hammer cutter, which is from 1 to approximately 60 mm from the trajectory of movement of the hammer cutter.

The disadvantage of this technical solution on the scale of the entire dust system is the low energy efficiency of the mill electric drive, since the electricity for it is supplied from the thermal power plant’s own needs, and it is generated at a coal-burning power plant with an efficiency of 35-38%.

A ball mill is known (patent RU 193347 U1, IPC B02C 17/04, B02C 17/06, B02C 17/10, published 24.10.2019, Bulletin No. 30), containing loading and unloading devices, grinding balls, a shaft on which a hollow drum is mounted, disks are placed on the shaft, dividing the drum into sections, while their diameter is increased from the loading device to the unloading device, in the end surface of the drum in the first section there is an annular window for loading the material, and in the last section of the drum there are openings for unloading the finished product, according to the utility model, the hollow drum is made of two parts of variable diameter: the first of a smaller diameter - for preliminary grinding, the second with a diameter 1.4-1.5 larger than the diameter of the first part - for fine grinding, and the diameter of the grinding balls of the second part in 1.4-1.5 larger than the diameter of the balls of the first part, on the inner cylindrical part of the drum of larger diameter, hooks are installed, and their working surface is made at an angle of 30-45° to the radius of the drum, to regulate the distance between the disks on the shaft, spacers are installed between them.

Another disadvantage of this technical solution on the scale of the entire dust system is the low energy efficiency of the mill's electric drive.

A known installation for preparing pulverized fuel (patent RU 197671 U1, IPC F23K 1/00, B02C 17/00, published on 21.05.2020, bulletin No. 15) consists of a raw coal bin and a finished dust bin, a mill, a separator, dampers, a cyclone, a mill fan, and a finished dust pipeline. In the installation, coal is fed into a ball drum mill, hot (primary) air is supplied, which is necessary for drying the fuel and transporting it, from a hot air box under some pressure, as well as under the action of a vacuum created in the mill by a fan. In the mill, the fuel is crushed and dried, which is sent to the separator, where it is divided into two streams. The finished fine dust is sent to the cyclone, and the coarse (undermilled) dust is returned to the inlet neck of the mill. The cyclone precipitates the finished dust, which is transferred to the dust bunker, where it is accumulated. From the dust bunker, the dust feeders feed the finished dust in the required quantity into the finished dust pipeline and send it through the burners into the boiler furnace for further combustion. The smallest particles that do not settle in the cyclone are transferred to the mill fan, from which they are distributed among the burners.

Another disadvantage of this technical solution is the low energy efficiency of the mill electric drive on the scale of the entire dust system.

The closest in technical essence to the proposed invention is the method of pulverization described in patent RU 94313 U1, IPC F23K 1/00, published 20.05.2010, Bulletin No. 14, where a feeder is included, coal from the bunker is sent to the mill simultaneously with hot flue gases supplied from the gas intake window of the boiler furnace through the gas intake shaft to the mill. Raw coal in the mill is dried, crushed and transferred through a dust pipeline to the burner device, into which hot air is simultaneously supplied. Fuel in the burner device is mixed with air, where it is ignited and burned in the boiler furnace. The temperature of the gases coming from the furnace to the additional air heater and the mill is adjusted by supplying cold flue gases from the recirculation smoke exhauster.

The disadvantage of this technical solution is the high energy losses associated with the presence of an electric drive for the operation of the mill, which at the thermal power plant consumes electricity from the power plant’s own needs, and it, in turn, is generated at the thermal power plant usually with an efficiency of 35-38% (with 62-65% of unavoidable energy losses).

The technical objective of the proposed method of dust preparation is to ensure energy conservation in the dust preparation system at a thermal power plant by using a gas piston engine (GPE) as a mill drive and maximum utilization of the energy of the GPE exhaust gases and the heat of the water cooling the GPE elements.

The technical result consists in reducing the use of electricity for the thermal power plant’s own needs and energy conservation.

This is achieved by the method of dust preparation. at a thermal power plant, in which crushed coal is fed into a mill, where it is ground, the dust-gas mixture from the mill is sent sequentially to a separator for screening out large substandard dust and returning it back to the mill, and fine dust is sent to a dust supply system and then to the boiler burners, according to the invention, a gas piston engine (GPE) is used as a mill drive, natural gas is fed to the GPE, and the exhaust gas flow from the GPE is sent to the boiler or to its burners, water is fed to the cooling system of the GPE elements, where it is heated and removed.

The essence of the invention is explained by drawings, where Fig. 1 shows a diagram of the proposed pulverization complex and the following designations are adopted:

1 - GPD (without equipment for generating electricity and heating), installed instead of the mill drive electric motor;

2 - mill (hammer, ball drum or medium-speed roller);

3 - dust separator;

4 - dust supply system to the boiler (direct injection or with an intermediate hopper);

5 - boiler;

6 - burners;

7 - drying agent (only hot air from the main air heater or hot air mixed with flue gases);

8 - bunker for raw crushed coal;

9 - water cooling the elements of the gas turbine engine;

10 - pipeline for removing heated water that cools the gas turbine engine elements;

11 - exhaust gases of the gas piston engine (with a temperature of 400-600°C);

12 - descending shaft for heating raw crushed coal;

13 - dried coal together with drying and ventilation agent;

14 - natural gas on gas turbine.

Fig. 2 shows a diagram of the distribution of energy supplied to a gas piston engine (GPE) with natural gas; the following designations are used in it:

15 - energy of natural gas entering the gas turbine engine = 100%;

16 - useful energy ≈90%;

17 - mechanical energy transmitted to the mill rotor (to the drive of the ball mill drum) ≈42%;

18 - utilized thermal energy of exhaust gases ≈33%;

19 - utilized thermal energy of water cooling the elements of the gas turbine engine (this is the water jacket for cooling the engine, the oil circuit cooler) ≈15%.

20 - thermal energy losses in the gas turbine engine and in thermal energy transfer sections ≈10%.

The method of dust preparation at a thermal power plant is carried out as follows.

The GPD 1 is used as a drive for the mill 2. The output shaft of the GPD 1 is directly connected to the rotor shaft of the hammer or roller mill 2 (see Fig. 1). In the case of a ball drum mill - to the drum drive. For example, an electronic control system ensures the optimal rotation speed of the rotor of the mill 2. The installation with the GPD 1 does not contain equipment for generating electricity and heating.

Natural gas 8 is supplied to the gas turbine engine 1. The electronic control system ensures optimal rotor speed.

Natural gas 14 is fed to the gas pressure unit 1. Crushed coal mixed with drying agent 7 and ventilation gas is fed to the mill 2; it is ground in it; the dust and gas mixture from the mill 2 is directed sequentially to the separator 3 for screening out large substandard dust back into the mill 2, and fine dust together with air is directed to the dust supply system 4 and then to the burners 6 of the boiler 5. The exhaust gas flow 11 with a temperature of 400-600°C from the gas pressure unit 1 is directed directly to the boiler 5 or to its burners 6. Cooling water 9 is fed to the cooling system of the gas pressure unit 1 elements, where it is heated as a result of heat exchange with the gas pressure unit 1 elements, and is discharged through the pipeline 10 for use for the TPP's own needs, for example, for domestic purposes.

In order to meet the requirements for gas supply to industrial facilities, natural gas can be supplied to GPD 1 within the pulverization department of a thermal power plant using the "pipe in pipe" option, and to reduce noise levels in production areas - by covering GPD 1 with a noise-proof casing. The operating conditions and parameters of GPD 1, its dimensions, motor service life before major and medium repairs, consumables and other information about GPD are provided by manufacturers within the framework of the technical specifications for GPD, taking into account the absence of electricity and heat generating equipment for mini-CHPs, since there is no need for it, since the output shaft of GPD 1 is immediately connected to the rotor shaft of mill 2 (to the drum drive in ball drum mills).

Energy saving as a result of using the present invention is ensured as follows. When using an electric drive for a mill, electric power for it is supplied from the TPP's own needs, and it is generated at a coal-burning power plant with an efficiency of 35-38% (a well-known fact following from the theory of the TPP steam turbine cycle, and repeatedly confirmed). As shown by tests of the GPD when using it as a source of only mechanical energy (i.e. without equipment generating electric power and heat), the efficiency of converting fuel energy into mechanical energy is approximately 42%, in addition, all the heat of the GPD exhaust gases (about 32%) and the heat of the water heated during cooling of the GPD elements (about 15%) are usefully used. Losses in the GPD itself and during heat transfer are about 10% (see Fig. 2).

As a result, energy losses for a traditional electric drive are 65-68%, while for the proposed method with a gas-turbine engine - about 10% (i.e. more than 6 times). The fuel efficiency coefficient in the gas-turbine engine variant can reach 90%.

The use of the invention makes it possible to ensure energy conservation in the dust preparation system and reduce the use of electricity for the thermal power plant's own needs due to the use of a gas-fired power plant and the utilization of the heat of the gas-fired power plant's exhaust gases and the heat of the water cooling the gas-fired power plant's elements.

Claims (1)

Method of dust preparation at a thermal power plant, in which crushed coal is fed into a mill, where it is ground, the dust-gas mixture from the mill is sent sequentially to a separator for screening out large substandard dust and returning it back to the mill, and fine dust is sent to the dust supply system and then to the boiler burners, characterized in that a gas piston engine (GPE) is used as a mill drive, natural gas is fed to the GPE, and the exhaust gas flow from the GPE is sent to the boiler or to its burners, water is fed to the cooling system of the GPE elements, where it is heated and removed.