CN104534850B - A kind of predrying system and method for raw coal low temperature utilizing flue gas, exhaust steam used heat - Google Patents

Abstract

The invention discloses a low-temperature pre-drying system and method for raw coal, which belongs to raw coal pre-drying equipment and utilizes flue gas and exhaust steam waste heat. Separator, coal bunker, coal feeder, coal mill; raw coal is crushed by a coal crusher and then enters low-temperature drying equipment for drying; low-temperature drying equipment adopts indirect drying equipment or direct drying equipment, and its heat source is taken from boiler exhaust or air cooling The unit exhausts steam; the dried raw coal particles are mixed with the raw coal particles at the exit of the separator and enter the coal bunker, and are sent to the furnace for combustion after being ground by a coal mill. According to the system configuration of different power plants, the present invention selects different types of low-temperature drying heat sources and equipment, and performs low-temperature pre-drying on the raw coal by recovering a large amount of low-grade low-temperature waste heat existing in the power plant, thereby increasing the calorific value of the raw coal and further improving the efficiency of the power plant.

Description

A low-temperature pre-drying system and method for raw coal using flue gas and exhaust steam waste heat

technical field

The invention belongs to the field of raw coal drying equipment, and in particular relates to a raw coal low-temperature pre-drying system and method utilizing flue gas and exhaust steam waste heat.

Background technique

my country's primary energy is dominated by coal, and the proportion of coal in my country's primary energy consumption has been around 70% for a long time. The installed capacity and power generation of coal-fired power generation account for about 69% and 78% of the total installed capacity and total power generation of the country, respectively, and the consumption of raw coal accounts for about 50% of the total domestic coal consumption. As of the end of 2013, the installed capacity of coal-fired power generation has reached 817 million kilowatts, and the annual power generation has reached 3.94 trillion kilowatt-hours, and in recent years it has maintained an annual growth rate of 30-40 million kilowatts. On the other hand, the emissions of major pollutants such as dust, SO ₂ , and NO _x from coal-fired power plants accounted for 12.20%, 42.16%, and 41.59% of the country's total emissions, respectively. Therefore, further improving the operating efficiency of coal-fired power plant units is of great significance to ensure my country's energy security and reduce the entire pollutant emission reduction work.

In recent years, the National Development and Reform Commission, the Ministry of Environmental Protection, and the National Energy Administration issued the "Coal-fired Energy Conservation and Emission Reduction Upgrading and Transformation Action Plan 2014-2020" clearly pointed out that the standard coal for power supply of newly built units is less than 300 g/kWh, which is very important Our country's power industry presents enormous challenges. At present, the main means of improving technology is to improve cycle parameters and improve unit operation level, but energy saving from the source of fuel has not yet been carried out. As we all know, my country's main power coal is bituminous coal and lean coal, and its moisture content is generally 3% to 15%, such as: bituminous coal (3-18%); lean coal (4-8%); washed medium coal (7-8%) 9%) and in the moisture content, external moisture is mainly about 70% to 80%. In addition, due to climate and environment and other factors, such as: the ambient humidity of power plants near the water system in our south is relatively high, and the moisture content in coal is generally higher.

The currently used coal grinding system is mainly a closed system, which is characterized in that after the coal particles are ground and dried by the coal mill, the moisture is directly sent into the furnace for combustion through the tertiary air or primary air. The moisture in the coal in the coal mill will reduce the temperature of the primary air entering the furnace on the one hand, and the moisture in the exhaust gas will increase the heat loss of the flue gas on the other hand. In addition, the moisture in the coal affects the power consumption of the coal mill. If the moisture in the coal entering the furnace can be properly reduced, it is also very beneficial to reduce the power consumption of the coal mill. At present, the research on the evaporation and drying technology of moisture in coal is mainly carried out for high-moisture coal such as lignite, and the drying methods of various drying media such as flue gas, air, and steam are becoming more and more mature.

In addition, low-temperature drying technology has also been developed in recent years. For example, the United States Clean Coal Power Initiative (CCPI) group proposed that the cooling water in the cooling tower is used to heat the air, and the air enters the fluidized bed drying equipment as a drying medium, which can effectively reduce lignite. moisture content and improve plant efficiency.

In common power coals such as bituminous coal and lean coal, the analysis shows that the external moisture also accounts for 70%-80% of the total moisture, so low-temperature drying equipment can be used to burn hard coal (bituminous coal, lean coal, etc.) The power station adopts low-temperature drying technology, which can greatly reduce the external moisture in the coal, which can also reduce the loss of boiler exhaust smoke and improve the efficiency of the power station. In addition, in conventional coal-fired power plants, low-grade waste heat resources are abundant, such as boiler exhaust, condenser circulating water, air-cooled unit air-cooled island hot air, etc. If the waste heat of such power plants is effectively used to pre-dry raw coal, it can be effectively Reduce the external moisture by 80-90%, and reduce the standard coal consumption by 1.5-3g/kWh. Therefore, recovering the low-temperature waste heat of the power station by preheating the coal into the furnace is a low-cost, high-return effective method to improve the operating efficiency of active units.

Contents of the invention

The object of the present invention is to provide a raw coal low-temperature pre-drying system and method utilizing flue gas, exhaust steam and waste heat. Recovery device, separator, coal bunker, coal feeder and coal mill; it is characterized in that the raw coal low-temperature pre-drying system includes a raw coal low-temperature pre-drying system that indirectly utilizes flue gas waste heat, and a raw coal low-temperature pre-drying system that indirectly utilizes air-cooled exhaust steam waste heat. Pre-drying system and raw coal low-temperature pre-drying system that directly utilizes flue gas waste heat;

The raw coal low-temperature pre-drying system that indirectly utilizes flue gas waste heat is that the coal conveyor belt 1 is arranged upstream of the coal crusher 2; The gas waste heat recovery device 4 is connected, and the gas and solid output ports of the low-temperature drying equipment 3 are respectively connected to the separator 5 and the coal bunker 6, and the coal bunker 6 is connected in series with the coal feeder 7 and the coal mill 8; the flue gas waste heat recovery device 4 Place it directly in the tail flue of the boiler;

The structural difference between the raw coal low-temperature pre-drying system that indirectly utilizes air-cooled exhaust steam waste heat and the raw coal low-temperature pre-drying system that indirectly utilizes flue gas waste heat is that the heat source inlet of the exhaust steam waste heat recovery device 4 is connected to the condensed water of the air-cooled island through a pipeline, and the outlet is through a pipeline. Connected to the condensate system; the rest of the structure is the same as the raw coal low-temperature pre-drying system that indirectly utilizes flue gas waste heat;

The structure of the raw coal low-temperature pre-drying system that directly utilizes flue gas waste heat is to combine the low-temperature drying equipment 3 of the raw coal low-temperature pre-drying system that indirectly utilizes flue gas waste heat with the flue gas and exhaust steam waste heat recovery device 4 into a flue gas drum dryer 9. It is respectively connected to the boiler exhaust pipe, coal crusher 2, separator 5 and coal bunker 6, and the rest of the structure is the same as the raw coal low-temperature pre-drying system that indirectly utilizes flue gas waste heat.

A low-temperature pre-drying method for raw coal using flue gas and exhaust steam waste heat. The low-temperature pre-drying system for raw coal includes a coal conveyor belt, a coal crusher, low-temperature drying equipment, waste heat utilization equipment, a separator, a coal bunker, a coal feeder and a mill. Coal machine; it is characterized in that the specific steps are that the raw coal at the end of the coal conveying belt is crushed by the coal crusher and then enters the low-temperature drying equipment for drying; the heat source for low-temperature drying is taken from the exhaust gas of the boiler or the exhaust steam of the air-cooling unit; the low-temperature drying equipment or the Use the flue gas drum dryer as the direct drying equipment to dry the raw coal, which greatly reduces the moisture outside the raw coal;

When indirect drying equipment is used, the dry tail gas from the drying equipment and the flue gas and exhaust gas waste heat recovery device 4 is nearly saturated humid air, which is directly discharged into the atmosphere after passing through the separator 5, and the exhaust gas from the exhaust gas and exhaust gas waste heat recovery device 4 The gas or condensed water is sent to the desulfurization or condensed water system; the dried raw coal particles are mixed with the raw coal particles from the outlet of the separator 5 and enter the coal bunker 6, and the outlet of the coal bunker 6 passes through the coal feeder 7, the coal mill 8, and the grinding After the coal machine 8 is ground, it is sent to the furnace for combustion;

When direct drying equipment is used, the flue gas and coal particles directly contact and exchange heat in the flue gas drum dryer 9, and the dry tail gas enters the desulfurization device after passing through the separator 5; the dried raw coal particles and the raw coal particles exiting the separator 5 Mixed into the coal bunker 6, the outlet of the coal bunker 6 passes through the coal feeder 7 and the coal mill 8 successively, and the coal mill 8 grinds and sends it into the furnace for combustion.

The drying heat source of the raw coal low-temperature pre-drying system is boiler exhaust at 130-160°C, and the boiler exhaust enters the desulfurization system after releasing heat in the flue gas waste heat recovery device 4; when using direct drying equipment, the boiler exhaust is in the Heat is released in the gas drum dryer 9, and the tail gas enters the desulfurization system through the separator 5; the exhaust gas temperature of the flue gas waste heat recovery device and the flue gas drum dryer is 80-130°C.

The condensing temperature of the exhaust steam of the air-cooling unit is 45-55°C, and returns to the condensate system after the exhaust steam and waste heat recovery device 4 releases heat; the air at the inlet of the drying equipment 3 is heated in the flue gas and exhaust steam and waste heat recovery device 4 to 40-50°C, the dry tail gas is separated by the separator 5 and then directly discharged into the atmosphere.

The beneficial effect of the present invention is that according to the system configuration of different power stations, different types of low-temperature drying heat sources and drying hot backups are selected, and the raw coal into the furnace is pre-dried by recovering a large amount of low-temperature waste heat in the power plant, thereby increasing the low-level coal into the furnace. Calorific value, reduce the loss of boiler exhaust smoke, thereby improving the power generation efficiency of the power plant. Preliminary analysis shows that after the system is applied to an in-service 600MW supercritical unit in my country, the standard coal consumption of different coal types (with different water content and calorific value) is reduced by about 1.6g/kWh~2.9g/kWh, for 300MW subcritical and 1000MW For supercritical units, the coal consumption of different coal types (with different water content and calorific value) is reduced by about 1.7g/kWh~3.0g/kWh (300MW), 1.5g/kWh~2.8g/kWh (1000MW).

Description of drawings

Figure 1 is a schematic diagram of a raw coal low-temperature pre-drying system that indirectly utilizes flue gas waste heat;

Figure 2 is a schematic diagram of a raw coal low-temperature pre-drying system that indirectly utilizes air-cooled exhaust steam waste heat;

Figure 3 is a schematic diagram of a raw coal low-temperature pre-drying system that directly utilizes flue gas waste heat;

In the figure: 1 is the coal conveying belt, 2 is the coal crusher, 3 is the low-temperature drying equipment, 4 is the flue gas, waste steam and waste heat recovery device, 5 is the separator, 6 is the coal bunker, 7 is the coal feeder, 8 is the mill Coal machine, 9 is a flue gas drum dryer.

detailed description

The present invention provides a raw coal low-temperature pre-drying system and method utilizing flue gas and exhaust steam waste heat. The present invention will be further described in detail below in conjunction with the accompanying drawings.

Figure 1 shows a low-temperature pre-drying raw coal system that indirectly utilizes flue gas waste heat. In the figure, the coal conveyor belt 1 is set above the coal crusher 2; the coal crusher 2 is connected to the feed port of the low-temperature drying equipment 3 through a pipeline , the low-temperature drying equipment 3 is connected with the flue gas, exhaust gas and waste heat recovery device 4, the gas and solid output ports of the low-temperature drying equipment 3 are respectively connected with the separator 5 and the coal bunker 6, and the coal bunker 6 is connected with the coal feeder 7 and the coal pulverizer 8 and series connection; among them, the flue gas, exhaust steam and waste heat recovery device 4 are directly placed in the boiler exhaust pipe, and the boiler exhaust steam is directly connected to the steam turbine circuit;

When indirect drying equipment is used, the raw coal at the end of the coal conveyor belt is crushed by the coal crusher, and the coal block is crushed by the coal crusher, and the average diameter of the particles is below 20mm, and then enters the low-temperature and low-temperature drying equipment 3 for drying; the heat source for low-temperature drying is Exhaust smoke from the boiler or exhaust steam from the air-cooling unit; use low-temperature drying equipment or flue gas drum dryer as direct drying equipment to dry the raw coal, greatly reducing the moisture outside the raw coal; the drying equipment and flue gas, exhaust steam waste heat recovery device 4 The dry tail gas is nearly saturated humid air, which is directly discharged into the atmosphere after passing through the separator 5, and the flue gas, exhaust gas or condensed water from the waste heat recovery device 4 are sent to the desulfurization or condensed water system; the dried raw coal particles are separated from the The raw coal particles from the outlet of the coal mine are mixed into the coal bunker 6, and the outlet of the coal bunker 6 passes through the coal feeder 7 and the coal mill 8 in turn, and the coal mill 8 grinds them and sends them to the furnace for combustion;

When direct drying equipment is used, the flue gas and coal particles directly contact and exchange heat in the flue gas drum dryer 9, and the dry tail gas enters the desulfurization device after passing through the separator; the dried raw coal particles are mixed with the raw coal particles from the outlet of the separator and enter The coal bunker 6 and the outlet of the coal bunker 6 pass through the coal feeder 7 and the coal mill 8 successively, and the coal mill 8 grinds them and sends them into the furnace for combustion.

The exhaust gas temperature of the above-mentioned boiler is 130-160°C. The boiler exhaust gas enters the desulfurization system after the flue gas and waste heat recovery device 4 release heat. The dry tail gas is nearly saturated humid air, which is separated by the separator 5 and discharged into the atmosphere; Depending on the drying degree of raw coal and the amount of flue gas used, the exhaust gas temperature of the waste heat recovery device and the flue gas drum is 80-130 °C.

Figure 2 shows a low-temperature pre-drying system for raw coal that indirectly utilizes air-cooled exhaust steam waste heat. In the steam turbine circuit, the output of the steam turbine is connected to the air-cooling unit, and the flue gas and exhaust steam waste heat recovery device 4 is placed outside the exhaust pipe of the boiler and connected to the air-cooling unit through the pipe; the rest of the structure is the same as the raw coal low-temperature pre-drying system that indirectly utilizes the waste heat of the flue gas; Drying equipment 3 adopts indirect drying equipment, and its heat source is taken from the exhaust steam of the air-cooling unit; the exhaust steam exhausted by the air-cooling unit has a condensation temperature of 45-55°C, and enters the condensate water system of the steam turbine after releasing heat from the exhaust steam waste heat recovery device. After being heated to 40-50°C in the waste heat recovery device of exhaust gas and exhaust steam, it enters the indirect drying equipment. The dry tail gas is nearly saturated humid air, which can be directly discharged into the atmosphere after being separated by the separator 5. The flue gas and exhaust steam waste heat recovery device 4 exits The condensed water returns to the condensed water system; the coal particles at the outlet of the separator 5 are mixed with the raw coal particles dried by the low-temperature drying equipment 3, and then sent to the coal bunker, and the outlet of the coal bunker 6 passes through the coal feeder 7 and the coal mill 8 in turn. , sent into the furnace for combustion after being ground by the coal mill 8 .

Figure 3 shows a raw coal low-temperature pre-drying system that directly utilizes flue gas waste heat. The structure of the raw coal low-temperature pre-drying system that directly utilizes flue gas waste heat The equipment 3 is combined with the flue gas and exhaust steam waste heat recovery device 4 to form a flue gas drum dryer 9, which is respectively connected to the boiler exhaust pipe, coal crusher 2, separator 5 and coal bunker 6, and the rest of the structure is related to the indirect utilization of flue gas waste heat The raw coal low temperature pre-drying system is the same. The low-temperature drying equipment 3 adopts the flue gas drum dryer 9 as the direct drying equipment, and its heat source is taken from the exhaust gas of the boiler at 130-160°C; into the desulfurization system; the coal particles at the outlet of the separator 5 are mixed with the raw coal particles dried by the low-temperature drying equipment 3, and then sent to the coal bunker, and the outlet of the coal bunker 6 passes through the coal feeder 7, the coal mill 8, and the coal mill 8 in turn. After grinding, it is sent to the furnace for combustion.

After the system of the present invention is applied to a 600MW supercritical unit in service in my country, the standard coal consumption of different coal types (with different water content and calorific value) is reduced by about 1.6g/kWh to 2.9g/kWh, for 300MW subcritical and 1000MW supercritical units At the same time, the coal consumption of different coal types (different water content and calorific value) is reduced by about 1.7g/kWh~3.0g/kWh (300MW), 1.5g/kWh~2.8g/kWh (1000MW).

The invention can configure different types of drying heat sources and different types of drying equipment according to different power plant systems, and the drying equipment is easy to combine with other systems of the power plant and has high practical value.

Claims (4)

1. utilize the predrying system of raw coal low temperature of flue gas, exhaust steam used heat, the described predrying system of raw coal low temperature System include coal conveyer belt, coal breaker, low-temperature drying equipment, flue gas/exhaust steam waste heat recovery plant, separator, Coal bunker, feeder and coal pulverizer；It is characterized in that, the described predrying system of raw coal low temperature includes indirect utilization cigarette The predrying system of raw coal low temperature of gas used heat, the predrying system of raw coal low temperature of indirect utilization air cooling exhaust steam used heat and Directly utilize the predrying system of raw coal low temperature of fume waste heat；

The predrying system of raw coal low temperature of described indirect utilization fume waste heat is that coal conveyer belt (1) is arranged on broken coal The upstream of machine (2)；Coal breaker (2) is connected with the feeding mouth of low-temperature drying equipment (3) by pipeline, low Temperature drying equipment (3) is connected with flue gas/exhaust steam waste heat recovery plant (4), low-temperature drying equipment (3) Gas, solid delivery outlet connect separator (5) and coal bunker (6) respectively, coal bunker (6) again with feeder (7), grind Coal machine (8) is connected；Wherein flue gas/exhaust steam waste heat recovery plant (4) is placed directly in boiler back end ductwork；

The predrying system of raw coal low temperature of described indirect utilization air cooling exhaust steam used heat and indirect utilization fume waste heat Raw coal low temperature predrying system structure difference is that the thermal source inlet of flue gas/exhaust steam waste heat recovery plant (4) passes through Pipeline condenses water with Air-Cooling Island and is connected, and outlet is connected into condensate system by pipeline；Remaining structure and profit indirectly Identical by the predrying system of raw coal low temperature of fume waste heat；

The structure of the described predrying system of raw coal low temperature directly utilizing fume waste heat is to be given up by indirect utilization flue gas The low-temperature drying equipment (3) of the predrying system of raw coal low temperature of heat and flue gas/exhaust steam waste heat recovery plant (4) Merge into flue gas drum dryer (9), respectively with boiler exhaust gas pipeline, coal breaker (2), separator (5) Connecting with coal bunker (6), remaining structure is identical with the predrying system of raw coal low temperature of indirect utilization fume waste heat.

2. utilize a raw coal low temperature pre-drying method for flue gas, exhaust steam used heat, its predrying system of raw coal low temperature Including coal conveyer belt, coal breaker, low-temperature drying equipment, waste heat utilization equipment, separator, coal bunker, feeder And coal pulverizer；It is characterized in that, the raw coal concretely comprising the following steps coal conveyer belt end enters low after coal breaker is broken Temperature drying equipment is dried；The thermal source of cold drying takes from boiler exhaust gas or air cooling unit exhaust steam；Use low temperature Raw coal is dried as direct drying equipment by drying equipment or employing using flue gas drum dryer, is greatly reduced Raw coal free surface moisture；

When using contact drying equipment, drying equipment and the dry tail of flue gas/exhaust steam waste heat recovery plant (4) Gas is close to saturated humid air, is directly discharged into air, flue gas/exhaust steam Waste Heat Recovery dress after separated device (5) Put the aerofluxus of (4) or condense water, sending into desulfurization or condensate system；Dried raw coal granule and separator (5) the raw coal granule exported out is mixed into coal bunker (6), coal bunker (6) outlet sequentially pass through feeder (7), Coal pulverizer (8), coal pulverizer (8) sends into hearth combustion after grinding；

When using direct drying equipment, flue gas directly contacts in flue gas drum dryer (9) with coal particle Heat exchange, is dried the separated device of tail gas (5) and enters desulfurizer afterwards；Dried raw coal granule and separator (5) The raw coal granule exported out is mixed into coal bunker (6), and coal bunker (6) outlet sequentially passes through feeder (7), mill Coal machine (8), coal pulverizer (8) sends into hearth combustion after grinding.

A kind of raw coal low temperature pre-drying method utilizing flue gas, exhaust steam used heat, its Being characterised by, the drying source of the described predrying system of raw coal low temperature is 130～160 DEG C of boiler exhaust gas, and boiler is arranged Cigarette after heat release, enters desulphurization system in flue gas/exhaust steam waste heat recovery plant (4)；Set using convection drying Time standby, boiler exhaust gas heat release in flue gas drum dryer (9), the separated device of tail gas (5) enters desulfurization system System；Fume waste heat retracting device is 80～130 DEG C with the exhaust gas temperature of flue gas drum dryer.

A kind of raw coal low temperature pre-drying method utilizing flue gas, exhaust steam used heat, its Being characterised by, the adiabatic condensation temperature of described Air-cooled Unit row's exhaust steam is 45～55 DEG C, in exhaust steam waste heat recovery plant (4) Condensate system is returned to after heat release；Low-temperature drying equipment (3) intake air is at flue gas/exhaust steam Waste Heat Recovery dress Put and (4) are heated to 40～50 DEG C, be dried after the separated device of tail gas (5) separates and be directly discharged into air.