CN109099451B - Energy-saving emission-reducing white-eliminating five-element heat exchange system for flue gas - Google Patents

Abstract

The invention discloses a smoke energy-saving emission-reducing and white-eliminating five-element heat exchange system, which comprises a front smoke cooler (1), a water and smoke heat exchanger (2), a desulfurizing tower (3), a condenser (4), a demister (5), a rear smoke reheater (6), a steam and smoke heat exchanger (7) and a chimney (8) which are connected in sequence; the condenser (4) is connected with a cooling tower (9) through a circulating pipeline; the front flue gas cooler (1) and the rear flue gas reheater (6) are connected through a circulating pipeline. The invention has the characteristics of improving the whitening effect, improving the utilization rate of the residual heat in the flue gas and reducing the emission of pollutants.

Description

A five-stage heat exchange system for flue gas energy saving, emission reduction and white elimination

technical field

The invention relates to a flue gas treatment system, in particular to a five-layer heat exchange system for flue gas energy saving, emission reduction, white elimination.

Background technique

my country is a big energy-consuming country, and its energy structure is dominated by coal. At present, 90% of coal-fired units in my country adopt the limestone-gypsum wet desulfurization process. This process reduces the temperature of the flue gas to about 50°C and is in a saturated or supersaturated state. However, the low-temperature wet saturated flue gas will condense at the chimney outlet to form a large amount of white plume (commonly known as "white smoke"), which will not only cause visual pollution, but also create a photochemical reaction environment. Moreover, the existing flue gas is discharged from the chimney after desulfurization treatment, and a large amount of pollutants remain in the discharged gas, which easily causes environmental pollution. Therefore, the existing technology has the problems of unsatisfactory tail gas dewhitening effect, low waste heat utilization rate and large pollutant discharge.

Contents of the invention

The object of the present invention is to provide a five-stage heat exchange system for energy saving, emission reduction and white elimination of flue gas. The invention has the characteristics of improving the whitening effect, increasing the waste heat utilization rate in the flue gas and reducing pollutant discharge.

The technical solution of the present invention: a flue gas energy saving, emission reduction, and whitening five-stage heat exchange system, including a front flue gas cooler, a water and flue gas heat exchanger, a desulfurization tower, a condenser, a demister, a rear flue gas reheater, a steam and flue gas heat exchanger, and a chimney connected in sequence; the condenser is connected to a cooling tower through a circulation pipeline; the front flue gas cooler and the rear flue gas reheater are connected through a circulation pipeline.

In the aforementioned five-stage heat exchange system for energy saving, emission reduction, and white elimination of flue gas, the water and flue gas heat exchanger is connected to a desalinated water tank through a circulation pipe.

In the aforementioned five-fold heat exchange system for energy-saving, emission-reduction, and white-out elimination of flue gas, the steam and flue gas heat exchanger includes two end plates arranged in parallel, and a plurality of intermediate partitions are evenly distributed between the two end plates. A condensed water outlet pipe; a sealing ring is also provided between the flange plate and the end plate.

In the aforementioned five-stage heat exchange system for energy saving, emission reduction and white elimination of flue gas, a plurality of partition plates arranged vertically and horizontally are arranged between adjacent intermediate partitions and between intermediate partitions and end plates.

In the above-mentioned five-stage heat exchange system for energy saving, emission reduction, whitening and whitening of flue gas, the partition plate includes a partition plate body, the upper and lower ends of the partition plate body are provided with a plurality of air guide grooves with a tapered cross-section, the inner wall surface of the air guide groove is provided with a diffused arc surface between the upper end surface of the partition plate body, and the bottom surface of the air guide groove is provided with a plurality of arc-shaped protrusions.

In the aforementioned five-stage heat exchange system for energy saving, emission reduction and white elimination of flue gas, the upper and lower ends of the partition body are also provided with thermal insulation coatings.

Compared with the prior art, the present invention sets up a five-layer heat exchanger consisting of a pre-flue gas cooler, a water and flue gas heat exchanger, a condenser, a demister, a post flue gas reheater, and a steam and flue gas heat exchanger in the flue at the tail of the flue gas source, thereby effectively improving the flue gas de-whitening effect, and can further reduce the emission of dust/Nox/SOx and other pollutants, realize the deep recycling of flue gas waste heat, and improve the recycling rate of resources. Through the mutual cooperation between the pre-flue gas cooler, water and flue gas heat exchanger and condenser, the flue gas is deeply condensed, so that the temperature of the flue gas entering the desulfurization tower is reduced, and the outlet temperature of the desulfurization tower is also reduced. Condensing the flue gas through the condenser can reduce the temperature of the flue gas to a lower level, achieving the effect of deep condensation, which is conducive to improving the white smoke control effect; at the same time, the flue gas enters the desulfurization tower after being cooled twice by the front flue gas cooler and the water and flue gas heat exchanger. The desulfurization effect of the desulfurization tower can be improved, the water consumption of the desulfurization tower can be reduced, and the temperature of the flue gas at the outlet of the desulfurization tower can be reduced, which plays the role of preliminary condensation. Through the mutual cooperation between the post-installed flue gas reheater and the steam and flue gas heat exchanger, it can ensure that the flue gas is fully heated after condensation, so as to improve the whitening effect of flue gas tail gas. In addition, the present invention connects the water and the flue gas heat exchanger to the desalination tank, and the desalination water can recover the heat in the flue gas, which can produce considerable energy benefits; by connecting the front flue gas cooler and the rear flue gas heater, it can make full use of the waste heat in the flue gas, so that the high-temperature flue gas in front of the desulfurization tower passes through the medium to heat the flue gas after the desulfurization tower, so that the waste heat can be effectively used; while the condenser removes moisture in the flue gas, it will also take away dust, NOx, SOx, etc. at the same time. All indicators fell to very low levels. To sum up, the present invention has the characteristics of being able to improve the whitening effect, improve the utilization rate of waste heat in the flue gas, and reduce the discharge of pollutants.

In addition, the present invention optimizes the structure of the steam and flue gas heat exchanger, and divides the fluorine-plastic steel heat exchange tubes into several separate spaces by arranging a plurality of partition plates arranged vertically and horizontally between the adjacent intermediate partitions and between the intermediate partitions and the end plates, so that the flue gas can be separated, the interference of the flue gas on adjacent heat exchange tubes can be reduced, and the vibration can be reduced; at the same time, the arrangement of the partition plates can also play a role in guiding the flue gas reasonably, effectively improving the heat exchange efficiency. By setting an air guide groove with a conical cross-section on the upper and lower ends of the partition plate, and at the same time setting a diffuser arc surface on the upper end of the air guide groove, the smoke can be evenly distributed in the separate area separated by the partition plate, and the heat exchange efficiency can be improved. The arc-shaped protrusions on the bottom surface of the air guide groove can not only disrupt the flow of the smoke, but also slow down the pressure of the smoke on the partition plate and improve the pressure bearing strength of the partition plate. By arranging thermal insulation coatings on the upper and lower ends of the partition body, the interference between the single-degree heat exchange areas can be further reduced, and the heat exchange efficiency can also be improved.

Description of drawings

Fig. 1 is a structural representation of the present invention;

Fig. 2 is a structural schematic diagram of a steam and flue gas heat exchanger;

Fig. 3 is a three-dimensional structure diagram of the steam and flue gas heat exchanger;

Fig. 4 is the structural representation of dividing plate;

Fig. 5 is a partial top view of a partition plate.

The marks in the drawings are: 1-pre-flue gas cooler, 2-water and flue gas heat exchanger, 3-desulfurization tower, 4-condenser, 5-demister, 6-post flue gas reheater, 7-steam and flue gas heat exchanger, 8-chimney, 9-cooling tower, 10-demineralized water tank, 701-end plate, 702-intermediate partition, 703-heat exchange tube, 704-flange, 705-arc head, 706- Sealing plate, 707-saturated steam inlet flange, 708-condensed water outlet pipe, 709-sealing ring, 710-partition plate, 711-partition plate body, 712-air guide groove, 713-diffusion arc surface, 714-arc protrusion.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and embodiments, but not as a basis for limiting the present invention.

Example. A flue gas energy-saving, emission-reduction, whitening and whitening five-stage heat exchange system, composed as shown in Figures 1 to 5, includes a front flue gas cooler 1, a water and flue gas heat exchanger 2, a desulfurization tower 3, a condenser 4, a demister 5, a rear flue gas reheater 6, a steam and flue gas heat exchanger 7, and a chimney 8; the condenser 4 is connected to a cooling tower 9 through a circulation pipeline; the front flue gas cooler 1 and the rear flue gas reheater 6 are connected through a circulation pipeline.

The water and flue gas heat exchanger 2 is connected to a desalinated water tank 10 through a circulation pipeline.

The steam and flue gas heat exchanger 7 includes two end plates 701 arranged in parallel, and a plurality of intermediate partitions 702 are evenly distributed between the two end plates 701, and a plurality of uniformly arranged heat exchange tubes 703 are arranged on the intermediate partitions 702, and both ends of the heat exchange tubes 703 are fixed to the end plates 701; the outer wall of the end plate 701 is provided with a flange 704, and the flange 704 is provided with an arc-shaped head 705, and the upper and lower ends of the arc-shaped end 705 are provided with sealing plates 706 The arc-shaped head 705 at one end is provided with a saturated steam inlet flange 707, and the arc-shaped head 705 at the other end is provided with a condensate outlet pipe 708; a sealing ring 709 is also provided between the flange 704 and the end plate 701.

Between the adjacent middle partitions 702 and between the middle partitions 702 and the end boards 701 there are also multiple partitions 710 arranged horizontally up and down.

The partition plate 710 includes a partition plate body 711, the upper and lower ends of the partition plate body 711 are provided with a plurality of air guide grooves 712 with a tapered cross-section, the upper end of the inner wall surface of the air guide groove 712 and the end surface of the partition plate body 711 are provided with a diffusion arc surface 713, and the bottom surface of the air guide groove 712 is provided with a plurality of arc-shaped protrusions 714.

The upper and lower ends of the partition body 711 are also provided with thermal insulation coatings.

Multiple steam and flue gas heat exchangers can be stacked and assembled together. The upper and lower ends of the front and rear sides of the end plate are respectively provided with a first supporting steel and a second supporting steel, and the two ends between the first supporting steel and the second supporting steel are respectively provided with I-beams; the lower surface of the second supporting steel is provided with a plurality of evenly arranged dovetail grooves; the upper surface of the first supporting steel is provided with dovetail bosses corresponding to the positions of the dovetail grooves. First fix one steam and flue gas heat exchanger at the bottom of the flue, then lift the other steam and flue gas heat exchanger, and adjust the position of the steam and flue gas heat exchanger so that the dovetail groove matches the dovetail boss, which completes the positioning of the heat exchanger module and improves the installation accuracy.

The front flue gas cooler recovers the waste heat of low temperature flue gas. The front flue gas cooler is a shell-and-tube heat exchanger, the flowing medium in the shell side is flue gas, and the medium on the tube side is water as an intermediate medium; the rear flue gas reheater is used to heat the flue gas for flue gas dewhitening, and the rear flue gas reheater is a shell and tube heat exchanger, the flowing medium in the shell side is flue gas, and the medium on the tube side is water as an intermediate medium.

Condenser: A shell-and-tube heater. The flowing medium in the shell side is flue gas, and the flowing medium in the tube side is circulating cooling water. The residual heat of the flue gas is used to heat the circulating cooling water to reduce the temperature of the flue gas.

Demister: A device that uses the principle of mechanical centrifugation to remove larger particles of water molecule droplets in the flue gas. A folding plate demister can be selected.

Steam and flue gas heat exchanger: a shell-and-tube heat exchanger, the flow medium in the shell side is flue gas, the medium on the inlet pipe side is low-pressure saturated or supersaturated steam, and the medium on the outlet pipe side is saturated condensed water. The latent heat of vaporization of steam is used to heat the flue gas.

The water and flue gas heat exchanger is a shell-and-tube heat exchanger. The flowing medium in the shell side is flue gas, and the flowing medium in the tube side is desalted water. The waste heat of the flue gas is used to heat the desalted water and recover the heat of the flue gas. The circulation pipe between the water and flue gas heat exchanger and the desalinated water tank includes a cold desalted water pipe and a hot desalinated water pipe. The two ends of the cold desalted water pipe are respectively connected with the heat exchange pipe inlet of the water and flue gas heat exchanger and the desalinated water tank outlet; the two ends of the hot desalted water pipe are respectively connected with the heat exchange pipe outlet of the water and flue gas heat exchanger and the desalinated water tank inlet.

The circulation pipe between the condenser and the cooling tower includes two pipes, one is a high-temperature circulation pipe and the other is a low-temperature circulation pipe. The inlet of the heat exchange tube of the condenser is low temperature water, and the outlet of the heat exchange tube of the condenser is high temperature water.

Saturated steam flows in from the saturated steam inlet flange, and condensed water flows out from the condensed water outlet pipe.

The air guide groove with a conical structure means that the air guide groove has a conical structure in a top view.

The circulation pipe between the pre-flue gas cooler and the rear flue gas reheater includes a high-temperature circulating water pipe and a low-temperature circulating water pipe, and a circulating pump is arranged on the low-temperature circulating water pipe. The water inlet of the heat exchange tube of the front flue gas cooler is connected to the low-temperature circulating water pipe, the water outlet of the heat exchange tube of the rear flue gas reheater is connected to the low temperature circulating water pipe;

The working process of the present invention: the high-temperature flue gas at 140°C first passes through the pre-flue gas cooler from the shell side, and the medium on the side of the heating pipe is water, so that the temperature of the flue gas drops to 115°C; the flue gas after cooling passes through the shell side of the water and flue gas heat exchanger, and the water and flue gas heat exchanger is a waste heat recovery heat exchanger, that is, the medium on the tube side of the water and flue gas heat exchanger is demineralized water. The desulfurization tower, compared with the original high-temperature flue gas, has lower flue gas temperature and volume flow rate, which can improve the desulfurization effect of the desulfurization tower and reduce the water consumption of the desulfurization tower. At the same time, it also reduces the temperature of the flue gas at the outlet of the desulfurization tower, which plays a role in preliminary condensation. The temperature of the flue gas drops to 50°C; the saturated wet flue gas after desulfurization enters the condenser and the demister in turn. The saturated wet flue gas is cooled by the circulating cooling water on the side of the tube in the condenser, the temperature drops to 45°C, and condensed water is precipitated; the flue gas condensed water also takes away part of the dust, NOx and SOx in the flue gas, which can further reduce the emission of dust/Nox/SOx and other pollutants. The larger-diameter liquid condensed water particles in the flue gas are collected by the demister, and can be recycled as desulfurization tower spray water after preliminary treatment; the flue gas after condensation and defogging enters the rear flue gas reheater, and the flue gas is heated by the intermediate water (hot water) on the side of the pipe, and the flue gas temperature rises to 70°C; after the intermediate water cools down, it returns to the front flue gas cooler through the circulating pump, and the cycle reciprocates; the flue gas after preliminary heating enters the steam and flue gas heat exchanger, and the flue gas is further heated to 80°C by steam , until the required temperature for white smoke plume treatment is met, the flue gas is discharged from the chimney.

Claims (1)

1. The utility model provides a flue gas energy saving emission reduction disappears and duplicate heat transfer system which characterized in that: the flue gas desulfurization device comprises a front flue gas cooler (1), a water and flue gas heat exchanger (2), a desulfurizing tower (3), a condenser (4), a demister (5), a rear flue gas reheater (6), a steam and flue gas heat exchanger (7) and a chimney (8) which are connected in sequence; the condenser (4) is connected with a cooling tower (9) through a circulating pipeline; the front flue gas cooler (1) and the rear flue gas reheater (6) are connected through a circulating pipeline; the water and flue gas heat exchanger (2) is connected with a desalting water tank (10) through a circulating pipeline; the steam and flue gas heat exchanger (7) comprises two end plates (701) which are arranged in parallel, a plurality of middle partition plates (702) are uniformly distributed between the two end plates (701), a plurality of heat exchange tubes (703) which are uniformly distributed are arranged on the middle partition plates (702), and two ends of each heat exchange tube (703) are fixed on the end plates (701); the outer wall surface of the end plate (701) is provided with a flange plate (704), the flange plate (704) is provided with an arc-shaped sealing head (705), and the upper end and the lower end of the arc-shaped sealing head (705) are provided with sealing plates (706); a saturated steam inlet flange (707) is arranged on the arc-shaped sealing head (705) at one end, and a condensed water outlet pipe (708) is arranged on the arc-shaped sealing head (705) at the other end; a sealing ring (709) is further arranged between the flange plate (704) and the end plate (701); a plurality of partition plates (710) which are arranged horizontally up and down are also arranged between the adjacent partition plates (702) and between the partition plates (702) and the end plates (701); the partition plate (710) comprises a partition plate body (711), wherein a plurality of air guide grooves (712) with conical sections are formed in the upper end surface and the lower end surface of the partition plate body (711), a diffusion cambered surface (713) is arranged between the upper end of the inner wall surface of the air guide groove (712) and the end surface of the partition plate body (711), and a plurality of arc-shaped bulges (714) are formed in the bottom surface of the air guide groove (712); the upper end face and the lower end face of the partition plate body (711) are also provided with heat insulation coatings.