Wet desulfurization flue gas smoke plume eliminating system and method
Technical Field
The invention relates to a smoke plume eliminating system for wet desulfurization smoke.
Background
In the saturated flue gas emission process after wet desulfurization, the saturated flue gas exchanges heat with the external air, so that the temperature of the flue gas is reduced, and saturated water vapor is condensed into water drops to form white smoke plumes, thereby causing adverse visual effects; meanwhile, the low-temperature emission of the flue gas is unfavorable for the lifting of the flue gas; in addition, the discharge of a large amount of water vapor causes overlarge ambient humidity, which affects the life of residents. In order to improve the lifting capacity of flue gas and reduce the phenomenon of smoke plume, many countries strictly limit the temperature of the flue gas, germany prescribes that the temperature of the flue gas outlet of a chimney is not lower than 72 ℃, japan prescribes that the temperature of the flue gas outlet is not lower than 90-110 ℃, united kingdom prescribes that the temperature is not lower than 80 ℃, while the united states has started to select wet chimney operation since the last 80 th century, part of enterprises add fuel gas (or steam) after FGD to heat the flue gas so as to avoid the flue gas from settling under specific conditions.
In order to prevent saturated smoke from condensing into water mist or to alleviate the condensation phenomenon of saturated smoke during the discharge process, methods for alleviating the formation of smoke plume include a heating method and a dehumidifying method according to the formation characteristics of smoke plume. The heating method is to discharge saturated flue gas in a certain overheat state by increasing the temperature of the saturated flue gas, and the method needs to consume a certain high-temperature heat source, and generates high-temperature flue gas by using a flue gas furnace under the condition of no proper waste heat, so that great energy waste is caused; the dehumidification method comprises the steps of reducing the temperature of saturated flue gas, condensing a part of vapor in the flue gas, reducing the moisture content of the flue gas, demisting and discharging, wherein the dehumidification method comprises a direct condensation method and an indirect heat exchange method, and the indirect heat exchange generally requires a heat exchanger with larger volume, so that the investment cost of early construction is high.
Disclosure of Invention
Aiming at the problems, the invention provides a wet desulfurization flue gas smoke plume eliminating system, which adopts a direct spraying mode to cool saturated wet flue gas, thereby saving the early construction investment and the operation cost of equipment.
In order to achieve the above object, the wet desulfurization flue gas plume abatement system of the present invention comprises:
the flue gas precooling section is used for precooling flue gas;
a spray condensing tower; is used for cooling the flue gas to 30-40 ℃ by spraying
The flue gas pre-cooling section is communicated with the spray condensing tower through a pipeline.
Preferably, the pre-cooling section comprises a cooling flue, and the cooling flue is provided with a first and/or a second cooling device and a smoke dust detection device;
when the dust content of the flue gas is smaller than a preset value, starting a second cooling device to cool the flue gas;
when the dust content of the flue gas is larger than a preset value, the first cooling device is started to cool the flue gas.
Preferably, the first cooling device is a cooling nozzle arranged in the cooling flue and used for spraying cooling circulating water into the flue in a forward direction or a lateral direction; the second cooling device is an air heat exchanger.
Preferably, the spray condensing tower comprises a condensing tower; a condensing water tank is arranged at the lower part of the condensing tower; the upper part of the condensing tower is provided with more than two stages of cooling nozzles and demisters; the flue gas outlet of the flue gas precooling section is arranged in the middle of the condensing tower.
Preferably, a flue gas distributor is arranged at a flue gas outlet of the flue gas precooling section, and the flue gas distributor is arranged in parallel with the water surface of the condensation water tank.
Preferably, the system further comprises a cooling unit, wherein the cooling unit consists of a condensation water pump, a cooling tower and a spray water pump which are communicated through pipelines; a cold water tank is arranged at the bottom of the cooling tower;
the condensing water pump pumps the condensing water in the condensing water pool at the bottom of the spray tower into the cooling tower to cool the condensing water; the spray water pump pumps the cooling water of the cold water tank into the cooling nozzles in the condensing tower and/or the cooling flue.
Preferably, the condensing tower further comprises a temperature control unit, wherein the temperature control unit comprises a control device and a temperature sensor arranged in the condensing tower;
the control device performs the following control according to the temperature:
when the temperature of the flue gas outlet of the spray condensing tower is higher than the set temperature T of the set flue gas outlet, outputting a control signal to enable the spray water pump to increase the water supply quantity of the cooling nozzle of the condensing spray tower;
when the flue gas outlet temperature of the spray condensing tower is lower than the set flue gas outlet set temperature T, a control signal is output to enable the spray water pump to reduce the water supply quantity of the cooling nozzle of the condensing spray tower.
In order to achieve the above purpose, the wet desulfurization flue gas smoke plume eliminating method of the invention comprises the following steps:
precooling the flue gas through a flue gas precooling section;
and cooling the pre-cooled flue gas to 30-40 ℃ by spraying through a spray condensing tower.
Preferably, the step of pre-cooling the flue gas by the flue gas pre-cooling section comprises the following steps of;
when the dust content of the flue gas is smaller than a preset value, starting a second cooling device to cool the flue gas;
when the dust content of the flue gas is larger than a preset value, starting a first cooling device to cool the flue gas; the first cooling device is a cooling nozzle arranged in the cooling flue and is used for spraying cooling circulating water into the flue in a forward or lateral direction; the second cooling device is an air heat exchanger.
Preferably, the spraying step is as follows:
when the flue gas outlet temperature of the spray condensing tower is higher than the set flue gas outlet set temperature T, the water supply amount of a cooling nozzle of the condensing spray tower is increased;
and when the flue gas outlet temperature of the spray condensing tower is lower than the set flue gas outlet set temperature T, reducing the water supply amount of the cooling nozzle of the condensing spray tower.
The system and the method can effectively relieve the white fog phenomenon formed by saturated wet smoke emission, and compared with the conventional GGH heating defogging: the system is simple, the initial investment is saved, the equipment operation cost is low, and the equipment is easy to overhaul and replace. The temperature of the collected condensed water is 45-50 ℃, and the condensed water can be used for local heating in winter, thereby saving heating cost and running cost.
Drawings
FIG. 1 is a schematic diagram of a wet flue gas plume abatement process and system flow in embodiment 1 of the present invention;
FIG. 2 is a schematic diagram of a wet flue gas plume abatement process and system flue gas distributor according to the present invention;
FIG. 3 is a schematic diagram of a wet flue gas plume abatement process and system flow in embodiment 2 of the present invention;
fig. 4 is a schematic diagram of a wet flue gas plume abatement process and system in embodiment 3 of the present invention.
Detailed Description
The invention is further described below with reference to the drawings.
Example 1
As shown in fig. 1-2, the wet flue gas plume elimination process and system of the embodiment are composed of a flue gas pre-cooling section 1, a spray condensing tower 2, a cooling tower 3, a cold water tank 4 and a circulating water system.
The main purpose of the flue gas precooling section 1 is to pre-cool, facilitate the temperature control of the whole system, and simultaneously remove solid particles in the flue gas, the flue gas temperature of the section is reduced by about 3-5 ℃, the precooling nozzles 1.1 are arranged on the flue gas precooling section 1 and uniformly distributed along the circumferential direction, at least one layer of precooling nozzles 1.1 is arranged, and the cooling water pump 6 supplies water to the precooling nozzles 1.1. When the dust content in the flue gas is large, the cooling water quantity of the pre-cooling nozzle is properly increased, and dust particles are condensed by liquid drops, so that the flue gas dust removal effect is realized.
The spray condensing tower 2 consists of a tower body 2, a condensing water tank 2.1, a sewage disposal system 2.2, a condensed water outlet 2.3, a flue gas inlet 2.4, a flue gas distributor 2.5, a cooling nozzle 2.6, a demister 2.7, a cooling water inlet 2.8, a temperature measuring device 2.9 and a flue gas outlet 2.10. At least 2 layers are arranged in each of the cooling nozzles 2.6 and the mist eliminators 2.7.
The flue gas containing liquid water from the flue gas pre-cooling section 1 is impacted to the outer side of the wall surface of the bent pipe by liquid drops due to the action of centrifugal force at the flue gas inlet 2.4, and the liquid drops are condensed and fall to the bottom condensation water pool 2.1, so that the primary purification and separation of flue gas-water drops are realized. After the flue gas is uniformly distributed by the flue gas distributor 2.5, the flue gas speed is reduced to 0.5-2.5 m/s, the flue gas flows upwards, the flue gas exchanges heat with cooling water from the cooling nozzle 2.6, saturated steam in the flue gas is cooled, condensed and separated out, mechanical water in the flue gas is removed by the demister 2.7, and the mechanical water content of the flue gas discharged from the demister 2.7 is less than or equal to 75mg/m 3 The flue gas is discharged through a flue gas outlet 2.10 contracted at the upper part of the spray condensing tower 2.
The condensed water enters a condensed water pump 5 through a condensed water outlet 2.3 to be pressurized, and is conveyed to a cooling tower 3 to be cooled, and the cooling water falls into a cooling water tank 4 to be used as cooling circulating water under the action of gravity.
The circulating water system consists of a condensate pump 5, a cooling water pump 6 and a control system 7.
Smoke discharge temperature setting: according to different environmental temperatures, the temperature of the exhaust gas in summer is set to be 35-40 ℃ and the temperature of the exhaust gas in winter is set to be 30 ℃. The cooling water temperature of the cooling tower is set to be not higher than 33 ℃.
When the flue gas temperature of the temperature measuring device 2.9 exceeds the set temperature, the water supply amount of the cooling nozzle 2.6 is increased; when the flue gas temperature of the temperature measuring device 2.9 is lower than the set temperature, the water supply amount of the cooling nozzle 2.6 is reduced.
The cooling tower 3 is usually formed by combining a plurality of single cooling towers in parallel, the fan of the cooling tower 3 operates at rated load in summer, and when the ambient temperature is low, the fan can be partially opened or operate at lower load.
Example 2
As shown in fig. 3, the operation principle is the same as that of embodiment 1, which replaces the cooling tower 3 with a heating heat user. In winter, when the plant area needs heating, the water spraying amount is reasonably controlled, so that the condensed water can be used for local heating when the water temperature of the condensation water tank 2.1 is 45-50 ℃, after heat exchange, the water temperature is reduced to about 25 ℃, and the condensed water is sprayed into the spray condensation tower 2 through the cooling nozzle 2.6 again for recycling. When the cooling capacity is insufficient, the cooling circulating water pump 6 is started, and the cooling water in the cooling water tank 4 is pumped into the cooling nozzle 2.6 together, so that the temperature of the flue gas outlet is ensured to be within a set range.
Example 3
As shown in fig. 4, the working principle is the same as in example 1, which replaces the pre-cooling nozzle 1.1 with an air heat exchanger 1.2. When the dust content of the flue gas is lower than 30mg/m < 3 >, and the content of corrosive gas in the flue gas is lower, the air heat exchanger 1.2 can be arranged in the flue gas pre-cooling section 1, the flue gas pre-cooling section 1 can be modified when the pipeline diameter is insufficient, the air heat exchanger 1.2 is convenient to arrange, the temperature of the air is raised by about 10 ℃ after passing through the air heat exchanger 1.2, the volume flow of the air is more than 1 time of the flow of the flue gas, the air is mixed with the condensed flue gas through the upper part of the air mixing spray condensing tower 2, and then the condensed flue gas is discharged.
The present invention is not limited to the above embodiments, and any changes or substitutions that can be easily understood by those skilled in the art within the scope of the present invention are intended to be included in the scope of the present invention. Therefore, the protection scope of the present invention should be defined by the claims.