Medium-pressure steam temperature and pressure reduction steam stripping process

Abstract

The invention discloses a medium-pressure steam temperature-reducing and pressure-reducing steam stripping process which comprises the following steps: conveying acidic sewage into a corresponding acidic water heat exchanger through a pipeline, conveying medium-pressure steam in a pipe gallery into a temperature-reducing and pressure-reducing device through a pipeline, reducing the pressure of the entering steam through the temperature-reducing and pressure-reducing device, conveying the medium-pressure steam subjected to pressure reduction into a steam stripping tower through a DN50 pipeline, and carrying out steam stripping on the medium-pressure steam through a steam stripping tower; the system has the following advantages that steam in pipe gallery medium-pressure steam enters the hydrogen sulfide removal stripping tower after being decompressed by the pilot-operated type temperature and pressure reduction device, the steam pressure and temperature stability of the stripping tower are high after the pipeline is involved, the temperature and pressure stability of the stripping steam are guaranteed, and the stripping efficiency is improved. Through the steel pipe pipeline body, the sliding layer, the calcium silicate, the glass wool pipe shell, the polyurethane foam and the glass fiber reinforced plastic outer protective layer, the influence of the equivalent thermal resistance of heat exchange between the steam medium and the inner wall of the steel pipe and the equivalent thermal resistance of heat exchange between the soil surface and the external environment on calculation is very small.

Description

Technical Field

[0001] The present invention relates to the technical field of pressure reduction of a pilot type desuperheating and pressure reducing valve for a hydrogen sulfide stripping tower, and particularly relates to a medium-pressure steam desuperheating and pressure reducing stripping process. Background Art

[0002] The stripping principle means that a carrier gas such as air or steam is introduced into water, so that the carrier gas is in full contact with the wastewater, and the dissolved gases and some volatile substances in the wastewater are transferred to the gas phase, thereby achieving the purpose of removing pollutants in the water. According to the phase equilibrium principle, in a liquid mixture at a certain temperature, each component has an equilibrium partial pressure. When the equilibrium partial pressure of this component in the gas phase in contact with the liquid phase tends to zero, and the gas-phase equilibrium partial pressure is much smaller than the liquid-phase equilibrium partial pressure, the component will transfer from the liquid phase to the gas phase. The existing low-boiling oil enters the hydrogen sulfide stripping tower after heat exchange with refined heavy aromatic oil and reaction products through a low-boiling oil / heavy aromatic oil heat exchanger and a reaction product / low-boiling oil heat exchanger respectively. This tower is stripped by low-pressure steam (1.0 MPa, 240 °C).

[0003] However, currently, when the large steam blowing is carried out through the stripping tower pretreatment device, the pressure of the 1.0 MPa steam pipe network will be as low as 0.5 MPa, and the low-pressure steam pressure does not meet the requirements of the stripping steam for the hydrogen sulfide stripping tower. Under normal operating conditions, the stripping steam pressure is between 0.8 MPa and 1.0 MPa, and the temperature above 180 °C is required to meet the normal operating requirements; moreover, the steam transmission pipeline is usually buried in the soil, and the soil has a great influence on the design of the insulation structure of the directly buried pipeline. When the steam is actually in operation, the temperature of the medium steam decreases section by section along the transmission line. According to domestic research data, it shows that in the design of the insulation structure, the influence of the soil thermal resistance cannot be ignored. Therefore, it is reasonable to calculate the thermal resistance of the soil as the insulation layer. In the calculation, the heat transfer from the outer wall of the outer protection layer to the soil can be considered as two-dimensional steady-state heat transfer, and the heat transfer between the soil surface layer and the external environment belongs to unsteady-state heat transfer. Summary of the Invention

[0004] The technical problem to be solved by the present invention is that when the stripping tower pretreatment device blows a large amount of steam, the pressure of the 1.0 MPa steam pipe network will drop to 0.5 MPa, and the low-pressure steam pressure does not meet the requirements of the stripping steam for the hydrogen sulfide stripping tower. Under normal operating conditions, the stripping steam pressure is between 0.8 MPa and 1.0 MPa, and the temperature above 180 °C is required to meet the normal operating requirements; and the steam transmission pipeline is usually buried in the soil, and the soil has a great influence on the design of the thermal insulation structure of the directly buried pipeline. When the steam is actually operating, the temperature of the medium steam decreases along the pipeline section by section. According to domestic research data, the influence of the soil thermal resistance cannot be ignored in the design of the thermal insulation structure. Therefore, it is reasonable to calculate the soil as the thermal resistance of the thermal insulation layer. In the calculation, the heat transfer from the outer wall of the outer protection layer to the soil can be considered as two-dimensional steady-state heat transfer, and the heat transfer between the soil surface layer and the external environment belongs to unsteady-state heat transfer. Therefore, a medium-pressure steam desuperheating and pressure-reducing stripping process is provided to solve the above problems.

[0005] The technical solution adopted by the present invention to solve the technical problem is: a medium-pressure steam desuperheating and pressure-reducing stripping process, which includes the following steps:

[0006] S1: The acidic sewage is transported through a pipeline to the corresponding acidic water heat exchanger;

[0007] S2: After being heat-exchanged in the acidic water heat exchanger, the acidic sewage enters the stripping tower, and the acidic water sewage flows downward in the stripping tower;

[0008] S3: At the same time, the medium-pressure steam in the pipe gallery is transported through a pipeline to the desuperheating and pressure-reducing device, and the steam entering is depressurized by the desuperheating and pressure-reducing device;

[0009] S4: After being depressurized in step S3, the medium-pressure steam is transported to the stripping tower through a DN50 pipeline;

[0010] S5: The low-pressure steam entering the stripping tower through step S4 causes the acidic gas such as H2S and NH in the stripping tower to be separated from the top of the stripping tower through a liquid separation tank. At the same time, the top of the stripping tower is equipped with a circulating pump and an air cooler to ensure that the temperature at the top of the stripping tower is constant;

[0011] S5: The steam refluxing in the stripping tower returns to the reheater for reheating and then is transported to the desuperheating and pressure-reducing device for utilization;

[0012] S6: The water purified in the stripping tower is pumped out by a purified water pump. The water pumped out by the purified water pump is heat-exchanged through a pipeline in the purified water heat exchanger and then flows to the purified water cooler to be cooled to below 50 °C, and finally is transported to the sewage treatment plant through a pipeline.

[0013] As a preferred technical solution of the present invention, in the step S2, the medium-pressure steam pressure in the pipe gallery is 3 MPa - 10 MPa, and the medium-pressure steam temperature in the medium pipe gallery is 200 - 400 °C.

[0014] As a preferred technical solution of the present invention, in the step S2, the steam after desuperheating and pressure reduction has a pressure of 0.8 MPa - 1.0 MPa and a temperature of 180 - 240 °C.

[0015] As a preferred technical solution of the present invention, in the step S4, the DN50 pipeline is a 2-inch pipe with an inner diameter of 50 mm, an outer diameter of 56 mm, and a wall thickness of 3 mm.

[0016] As a preferred technical solution of the present invention, in the step S5, the reheater is a thermosyphon type, and the condensed water in the reheater enters the condensate recovery tank.

[0017] As a preferred technical solution of the present invention, in the step S5, it is respectively branched to the acidic water storage tank and the acidic gas desulfurization device through a separation tank.

[0018] As a preferred technical solution of the present invention, in the step S5, the air cooler for the top circulation of the stripping tower is controlled by a variable frequency speed regulation motor.

[0019] As a preferred technical solution of the present invention, the medium-pressure steam pipeline in the pipe gallery is provided with a heat preservation structure, and the heat preservation structure is composed of a steel pipe pipeline main body, a sliding layer, calcium silicate, glass wool pipe shell, polyurethane foam, and a fiberglass outer protective layer.

[0020] As a preferred technical solution of the present invention, the temperature interface between the calcium silicate and the glass wool pipe shell is controlled at 180 °C, the temperature interface between the glass wool pipe shell and the polyurethane foam is controlled at 100 °C, and the temperature interface between the fiberglass outer protective layer and the soil is controlled at 55 °C.

[0021] As a preferred technical solution of the present invention,

[0022] Thermal conductivity of calcium silicate: λ1 = 0.055 + 0.00011(Tm - To) = 0.074 W / mK;

[0023] Thermal conductivity of glass wool: λ2 = 0.044 + 0.00017(Tm - To) = 0.056 W / mK;

[0024] Thermal conductivity of polyurethane: λ3 = 0.0275 + 0.00014(Tm - 25) = 0.035 W / mK.

[0025] The present invention has the following advantages: The steam in the medium-pressure steam in the pipe gallery enters the hydrogen sulfide stripping column after being depressurized by the pilot-operated desuperheating and pressure-reducing device. After this pipeline is intervened, the steam pressure and temperature in the stripping column are relatively stable, ensuring the stability of the stripping steam temperature and pressure, enabling the hydrogen sulfide stripping column to smoothly remove sulfur-containing components; and the stripped steam refluxed from the stripping column enters the reboiler again for heating up and then being reused; through the steam pipeline insulation structure, the thermal resistance that plays a major role in the adiabatic design is the thermal resistance of the insulating material and the thermal resistance of the soil, while the equivalent thermal resistance of the heat exchange between the steel pipe pipeline main body, the sliding layer, calcium silicate, glass wool pipe shell, polyurethane foam, fiberglass outer protective layer, steam medium and the inner wall of the steel pipe, and the equivalent thermal resistance of the heat exchange between the soil surface and the external environment has little impact on the calculation, so it can be ignored. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a schematic structural diagram of the acidic sewage treatment principle of the preferred embodiment of the present invention;

[0027] Figure 2 is a schematic structural diagram of the medium-pressure steam pipeline insulation of the preferred embodiment of the present invention.

[0028] DESCRIPTION OF REFERENCE NUMERALS: 1. Steel pipe pipeline main body; 2. Sliding layer; 3. Calcium silicate; 4. Glass wool pipe shell; 5. Polyurethane foam; 6. Fiberglass outer protective layer; 7. Purified water pump; 8. Circulation pump. DETAILED DESCRIPTION OF THE INVENTION

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention. Many specific details are set forth in the following description in order to fully understand the present invention. However, the present invention may be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited by the specific embodiments disclosed below.

[0030] In order to more clearly understand the above objects, features and advantages of the present invention, the present invention will be further described in detail below with reference to the drawings and specific embodiments.

[0031] Please refer to Figures 1 - 2 , a medium-pressure steam desuperheating and pressure-reducing stripping process of the present invention includes the following steps:

[0032] S1: The acidic sewage is transported through a pipeline to the corresponding acidic water heat exchanger;

[0033] S2: The acidic sewage enters the stripping column after being heat-exchanged in the acidic water heat exchanger, and the acidic sewage flows downward in the stripping column;

[0034] S3: Meanwhile, the medium-pressure steam in the pipe gallery is transported through a pipeline to a desuperheating and pressure-reducing device, and the incoming steam is depressurized by the desuperheating and pressure-reducing device.

[0035] S4: After being depressurized in step S3, the medium-pressure steam is transported to the stripping column through a DN50 pipeline.

[0036] S5: The low-pressure steam entering the stripping column through step S4 causes the acidic gases such as H2S and NH in the stripping column to be separated from the top of the stripping column through a liquid separation tank. At the same time, the temperature at the top of the stripping column is ensured to be constant by the circulating pump 8 cooperating with the air cooler.

[0037] S5: The steam refluxing in the stripping column returns to the reheater for reheating and then is transported to the desuperheating and pressure-reducing device for utilization.

[0038] S6: The water purified in the stripping column is pumped out by the purified water pump 7. The water pumped out by the purified water pump 7 is transported through a pipeline to a purified water heat exchanger for heat exchange, and then flows to a purified water cooler to be cooled below 50 °C, and finally is transported to the sewage treatment plant through a pipeline.

[0039] In step S2, the pressure of the medium-pressure steam in the pipe gallery is 3 MPa - 10 MPa, the temperature of the medium-pressure steam in the middle pipe gallery is 200 - 400 °C. After desuperheating and pressure reduction in step S2, the pressure of the steam is 0.8 MPa - 1.0 MPa, and the steam temperature is 180 - 240 °C. In step S4, the DN50 pipeline is a 2-inch pipe with an inner diameter of 50 mm, an outer diameter of 56 mm, and a wall thickness of 3 mm. In step S5, the reheater is a thermosyphon type, and the condensed water in the reheater enters the condensate recovery tank. In step S5, through the liquid separation tank, it is respectively branched to the acidic water storage tank and the acidic gas to the sulfur device. In step S5, the circulating air cooler at the top of the stripping column is controlled by a variable frequency speed regulation motor.

[0040] Combined with Figure 2 As shown, when the ground is heated by solar radiation and ambient air temperature, the temperature field of the directly buried pipeline insulation structure will change. The heat loss value per unit pipe length decreases, and the temperature values of each interface increase. This may damage some control interfaces with temperature requirements (such as the temperature interface at the contact between organic and inorganic materials needs to ensure that the organic insulation layer is not damaged). Therefore, it is necessary to check the design calculation of the insulation structure under extremely high ground temperatures. The medium-pressure steam pipeline in the pipe gallery is provided with an insulation structure, and the insulation structure is composed of a steel pipe pipeline main body 1, a sliding layer 2, calcium silicate 3, glass wool pipe shell 4, polyurethane foam 5, and a fiberglass outer protective layer 6. The temperature interface between calcium silicate 3 and the glass wool pipe shell 4 is controlled at 180 °C, the temperature interface between the glass wool pipe shell 4 and polyurethane foam 5 is controlled at 100 °C, and the temperature interface between the fiberglass outer protective layer 6 and the soil is controlled at 55 °C; among them,

[0041] Thermal conductivity of calcium silicate 3: λ1 = 0.055 + 0.00011(Tm - To) = 0.074 W / mK;

[0042] Thermal conductivity of glass wool: λ2 = 0.044 + 0.00017(Tm - To) = 0.056 W / mK;

[0043] Thermal conductivity of polyurethane: λ3 = 0.0275 + 0.00014(Tm - 25) = 0.035 W / mK;

[0044] Through the above steam pipeline insulation structure, the thermal resistance that plays a major role in the adiabatic design is the thermal resistance of the insulating material and the soil thermal resistance. The equivalent thermal resistance of the heat transfer between the steam medium and the inner wall of the steel pipe, as well as the equivalent thermal resistance of the heat transfer between the soil surface and the external environment, has little impact on the calculation and can therefore be ignored.

[0045] The above shows and describes the basic principles, main features and advantages of the present invention. For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention. Any reference signs in the claims should not be regarded as limiting the claimed rights.

[0046] Other parts not detailed in the present invention belong to the prior art and will not be elaborated here.

[0047] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features. These modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A medium-pressure steam desuperheating and decompression stripping process, characterized in that: The following steps are involved: S1: Acidic sewage is transported to the corresponding acidic water heat exchanger through pipelines; S2: The acidic wastewater enters the stripping tower after heat exchange in the acidic water heat exchanger, and the acidic wastewater flows from top to bottom in the stripping tower; S3: At the same time, the medium-pressure steam in the pipe gallery is transported to the temperature reduction and pressure reduction device through the pipeline, and the incoming steam is depressurized by the temperature reduction and pressure reduction device; S4: After the medium-pressure steam is depressurized in step S3, it is transported to the stripping tower through a DN50 pipeline; S5: The low-pressure steam entering the stripping tower through step S4 separates the acidic gas such as H2S and NH3 in the stripping tower from the top of the stripping tower through a separator tank. Meanwhile, the top of the stripping tower is connected to a circulating pump and an air cooler to ensure a constant temperature at the top of the stripping tower. S5: The refluxed steam in the stripping tower is refluxed to the reheater for reheating and then transported to the temperature reduction and pressure reduction device for utilization; S6: The water purified in the stripping tower is pumped out by the purified water pump. The water pumped out by the purified water pump is transported to the purified water heat exchanger through a pipeline for heat exchange, and then flows to the purified water cooler to be cooled to below 50°C, and finally transported to the sewage treatment plant through a pipeline.

2. A medium-pressure steam desuperheating and decompression stripping process as claimed in claim 1, characterized in that: In step S2, the medium-pressure steam pressure of the pipe gallery is 3MPa-10MPa, and the medium-pressure steam temperature of the pipe gallery is 200-400°C.

3. A medium-pressure steam desuperheating and decompression stripping process as claimed in claim 1, characterized in that: In step S2, the steam is cooled and decompressed to a pressure of 0.8 MPa-1.0 MPa and a temperature of 180-240°C.

4. A medium-pressure steam desuperheating and decompression stripping process as claimed in claim 1, characterized in that: In step S4, the DN50 pipeline is a 2-inch pipe with an inner diameter of 50 mm, an outer diameter of 56 mm, and a wall thickness of 3 mm.

5. A medium-pressure steam desuperheating and decompression stripping process as claimed in claim 1, characterized in that: In step S5, the reheater is of a thermosyphon type, and the condensed water in the reheater enters a condensate recovery tank.

6. A medium-pressure steam desuperheating and decompression stripping process as claimed in claim 1, characterized in that: In step S5, the liquid is divided into the deacidified water storage tank and the acidic gas desulfurization device respectively through the liquid separation tank.

7. A medium-pressure steam desuperheating and decompression stripping process as claimed in claim 1, characterized in that: In step S5, the circulating air cooler at the top of the stripping tower is controlled by a variable frequency speed regulating motor.

8. A medium-pressure steam desuperheating and decompression stripping process as claimed in claim 1, characterized in that: The medium-pressure steam pipeline in the pipe gallery is provided with a thermal insulation structure, which consists of a steel pipe main body, a sliding layer, calcium silicate, a glass wool pipe shell, polyurethane foam, and a glass fiber reinforced plastic outer sheath.

9. A medium-pressure steam desuperheating and decompression stripping process as claimed in claim 8, characterized in that: The temperature interface between the calcium silicate and the glass wool tube shell is controlled at 180°C, the temperature interface between the glass wool tube shell and the polyurethane foam is controlled at 100°C, and the interface between the glass fiber reinforced plastic outer sheath and the soil is controlled at 55°C.

10. A medium-pressure steam desuperheating and decompression stripping process as claimed in claim 8, characterized in that: Thermal conductivity of calcium silicate: λ1=0.055+0.00011(Tm-To)=0.074W / mK; Thermal conductivity of glass wool: λ2 = 0.044 + 0.00017 (Tm-To) = 0.056 W / mK; Thermal conductivity of polyurethane: λ3=0.0275+0.00014(Tm-25)=0.035W / mK.

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