A waste sulfuric acid recovery evaporation system

Abstract

The utility model relates to a waste sulfuric acid recovery and evaporation system, including a multi-effect evaporator composed of a first-effect evaporator, a second-effect evaporator and a third-effect evaporator, a steam compressor, a TVR heat pump, a condenser, a steam-water separation tank, and a first-stage preheater and a second-stage preheater, etc. The tubes of the first-effect evaporator, the second-effect evaporator and the third-effect evaporator are connected in series in sequence, the secondary steam output of the first-effect evaporator is connected to the steam compressor, the secondary steam of the second-effect evaporator is connected to the steam compressor through the TVR heat pump, the secondary steam of the third-effect evaporator is condensed by the condenser and then connected to the gas-liquid separation tank, the gas phase interface of the gas-liquid separation tank is connected to the vacuum pipeline, and the output pipeline of the steam compressor is divided into three routes, which are respectively connected to the shell side inlets of the first-effect evaporator, the second-effect evaporator and the third-effect evaporator. The utility model has good process operation stability, low operation cost, low one-time investment cost, and controllable waste acid discharge concentration, and can be widely used in the evaporation and concentration process of high-boiling acid.

Description

Technical Field

[0001] The utility model relates to a waste sulfuric acid recovery and evaporation system. Background Art

[0002] In the chemical industry and other industries, the concentration and recovery of waste sulfuric acid is one of the problems that many companies are eager to solve. On the one hand, the concentration and recovery of waste sulfuric acid can save costs and reuse resources; on the other hand, it can also achieve energy conservation and emission reduction and reduce environmental pollution. Due to the low concentration of waste dilute sulfuric acid, it is often necessary to increase the concentration of sulfuric acid to meet the requirements of reuse. At present, the main methods for sulfuric acid concentration include pot concentration, combustion concentration, high temperature concentration and low temperature concentration. Among them, the sulfuric acid recovery rate of pot concentration, combustion concentration and high temperature concentration is not high, and it is only suitable for small-scale sulfuric acid concentration. The low-temperature concentration method is only suitable for the concentration of dilute sulfuric acid with a mass fraction concentration of less than 60%, and the mass fraction concentration of sulfuric acid after concentration is not more than 60%. For many production processes, it cannot meet the reuse requirements. In addition, the concentration process of sulfuric acid often consumes a large amount of energy (such as steam or electricity), while the rare waste sulfuric acid concentration system with a high theoretical energy-saving effect (a multi-effect MVR evaporation system using two steam compressors with the same gas volume in series) has practical problems such as difficulty in stable operation, difficulty in restarting after shutdown, difficulty in achieving the concentration standard of the concentrated discharge material, and / or too high one-time investment cost of the equipment, making it difficult to promote and apply in practice. Utility Model Content

[0003] The utility model aims to reduce the concentration cost of waste sulfuric acid and ensure the concentration effect.

[0004] The technical solution of the utility model is: a waste sulfuric acid recovery and evaporation system, comprising:

[0005] A multiple-effect evaporator is composed of an effect I evaporator, an effect II evaporator and an effect III evaporator. The shell side of each evaporator (effect I evaporator, effect II evaporator and effect III evaporator) is used to access / connect steam, and the tube side is used to access / connect materials (for example, waste sulfuric acid). The evaporation of water (or other solvents) in the materials is achieved by steam heating. The tube sides of the effect I evaporator, effect II evaporator and effect III evaporator are connected in series in sequence. The tube side inlet (material inlet) of the effect I evaporator is connected to the dilute sulfuric acid inlet pipe, the tube side outlet (material outlet) of the effect III evaporator is connected to the concentrated sulfuric acid outlet pipe, and the shell side inlet (steam inlet) of the effect I evaporator is connected to the high-pressure raw steam pipe (high-pressure raw steam supply pipe);

[0006] The steam compressor has a steam output pipeline divided into three routes, which are respectively connected to the shell side inlet (steam inlet) of the first effect evaporator, the second effect evaporator and the third effect evaporator, and the secondary steam output (secondary steam output pipe) of the first effect evaporator is connected to the steam inlet of the steam compressor;

[0007] TVR (Thermal Vapor Recompression) heat pump (TVR steam heat pump, for example, steam jet heat pump), wherein the pressure side interface (steam outlet) is connected to the steam compressor inlet, the high pressure side interface (power steam inlet) is connected to the high pressure raw steam pipe, and the secondary steam output (secondary steam output pipe) of the II effect evaporator is connected to the low pressure side interface (suction steam inlet) of the TVR heat pump;

[0008] Condenser, the secondary steam output (secondary steam output pipe) of the III-effect evaporator is connected to the condensation inlet (heat absorbing medium inlet, or steam inlet) of the condenser;

[0009] The steam-water separation tank (or steam-water separator), the condensation outlet (heat absorbing medium outlet, or condensed water outlet) of the condenser is connected to the inlet of the steam-water separation tank, and the gas phase space outlet (gas phase outlet, or vacuum interface) of the steam-water separation tank is connected to the vacuum pipeline (vacuum system / vacuum equipment's vacuum pipeline).

[0010] A steam inlet main pipe can be set at the shell side inlet of the first effect evaporator, and the high-pressure raw steam pipe and the corresponding output pipe of the steam compressor are connected through the steam inlet main pipe to realize the connection between the steam output pipeline and the high-pressure raw steam pipe and the shell side inlet of the first effect evaporator.

[0011] Furthermore, the vacuum pipeline is provided with a control device for controlling the vacuum degree of the gas phase space of the steam-water separator tank. For example, a vacuum valve can be provided with a matching valve control device or the opening of the vacuum valve can be controlled in any other suitable manner to control the vacuum degree of the gas phase space of the steam-water separator tank.

[0012] Furthermore, the refrigerant (heat absorbing medium) inlet and outlet of the condenser are respectively connected to the water supply pipe and the water return pipe of the refrigeration system (refrigeration water circulation system).

[0013] Furthermore, the secondary steam of the first effect evaporator, the second effect evaporator and the third effect evaporator are respectively drawn out from the top of the separation chamber of each evaporator.

[0014] Preferably, a steam input main pipe is provided at the inlet of the steam compressor, and the secondary steam output of the I-effect evaporator and the medium-pressure side interface of the TVR heat pump are respectively connected to the steam input main pipe of the steam compressor through their own connecting pipes, thereby realizing the connection (access) between the secondary steam output of the I-effect evaporator and the medium-pressure side interface of the TVR heat pump and the inlet of the steam compressor.

[0015] Furthermore, a first-stage preheater (heat exchanger) is provided, and the heat-absorbing medium channel of the first-stage preheater is connected in series to the dilute sulfuric acid input pipe (the inlet and outlet of the heat-absorbing medium channel are respectively connected to the dilute sulfuric acid input pipe on the corresponding side, and form a series of dilute sulfuric acid channels with the dilute sulfuric acid output pipes on both sides), and the shell side outlet of the first-effect evaporator is connected to the heat-releasing medium inlet of the first-stage preheater.

[0016] Furthermore, the shell side outlet (condensed water outlet) of the III effect evaporator is connected to the water inlet of the II effect evaporator, the shell side outlet of the II effect evaporator is connected to the water inlet of the I effect evaporator, the water inlet of the II effect evaporator is connected to the shell side liquid phase space of the II effect evaporator, and the water inlet of the I effect evaporator is connected to the shell side liquid phase space of the I effect evaporator, thereby forming condensed water from the III effect evaporator, the II effect evaporator to the I effect evaporator, which is collected in sequence and discharged from the shell side outlet of the I effect evaporator.

[0017] Furthermore, the heat release medium inlet of the first-stage preheater is connected to a high-temperature condensed water discharge pipe.

[0018] Furthermore, a second-stage preheater (heat exchanger) is provided, and the heat absorbing medium channel of the second preheater is connected in series to the dilute sulfuric acid input pipe (the inlet and outlet of the heat absorbing medium channel are respectively connected to the dilute sulfuric acid input pipe on the corresponding side, and form a series of dilute sulfuric acid channels with the dilute sulfuric acid output pipes on both sides), which is located between the first-stage preheater and the first-effect evaporator, and the high-pressure raw steam pipe is connected to (connected to) the heat releasing medium inlet of the second-stage preheater.

[0019] Multiple branch pipes (connecting pipes) can be set on the high-pressure raw steam pipe to respectively connect the shell side inlet of the first-effect evaporator, the medium-pressure side interface of the TVR heat pump and the heat release medium inlet of the second-stage preheater.

[0020] Furthermore, the heat release medium outlet of the second-stage preheater is connected to the return water pipeline of the high-pressure steam generating boiler system.

[0021] According to actual needs, detection instruments (such as pressure gauges, flow meters, etc.) and valves (such as flow control valves, stop valves, etc.) can be installed on the required pipelines and devices to achieve control and monitoring of the working mode and working parameters. For example, the evaporation amount of the system can be controlled by adjusting the working parameters, thereby controlling the output concentrated sulfuric acid concentration.

[0022] The beneficial effects of the utility model are: the steam compressor of the waste sulfuric acid recovery evaporation system is not prone to surge, the process operation is stable, the equipment operation cost is low, the one-time investment cost of the equipment is low, and the waste acid discharge concentration is controllable. The process of combining the traditional TVR heat pump with the centrifugal steam compressor heat pump is adopted, and a small amount of raw steam is consumed to increase the temperature rise by about 8°C by using the TVR heat pump, and then the temperature rise is increased by about 20°C through a centrifugal steam compressor. It well avoids the disadvantages of the traditional use of multi-stage centrifugal steam compressors in series to compress secondary steam to increase the temperature rise by 36°C, the compressor has high manufacturing cost, high power consumption, and is very prone to surge during operation, which affects the stable operation of the system. It can be widely used in the evaporation treatment process of waste acid (for example, dilute sulfuric acid waste acid), and is particularly suitable for many comprehensive wastewaters with high boiling points.

[0023] The utility model can be used for concentrating waste sulfuric acid, and can also be used for similar occasions of evaporation / concentration of other materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the utility model. DETAILED DESCRIPTION

[0025] See also Figure 1 Different from the existing multi-effect MVR evaporation system using a two-stage steam compressor, the utility model adopts a multi-effect evaporation process of MVR+TVR+single-effect evaporation combination to evaporate and concentrate waste sulfuric acid. The equipment used includes: a first-stage preheater (condensate and dilute sulfuric acid preheater) 1, a second-stage preheater (raw steam and dilute sulfuric acid preheater) 2, a condenser cooled by exhaust steam 3, a first-effect evaporator 7, a second-effect evaporator 8, a third-effect evaporator 9, a TVR steam heat pump 5, a steam compressor 6 and a steam-water separation tank 4. In addition, a matching vacuum system and a cooling circulating water system are also provided. The first-effect evaporator, the second-effect evaporator and the third-effect evaporator are respectively provided with their own first-effect evaporator separation chamber 7a, the second-effect evaporator separation chamber 8a and the third-effect evaporator separation chamber 9a. The tube side of each evaporator is connected to the material to be evaporated (for example, dilute sulfuric acid), and the shell side is connected to steam (heat release medium).

[0026] The first-stage preheater and the second-stage preheater are connected in series, and the feed is preheated with high-temperature condensed water and high-temperature raw steam respectively, so that the dilute sulfuric acid reaches the boiling point after being heated by the first-stage preheater and the second-stage preheater. The preheated low-temperature condensed water (first-stage preheater) and high-temperature condensed water (second-stage preheater) are respectively pumped out and returned to the boiler room.

[0027] The feed enters the tube process of the first-effect evaporator, the second-effect evaporator, and the third-effect evaporator step by step, and is concentrated step by step by each evaporator to reach the required concentration, and is discharged and stored.

[0028] The shell sides (inlet) of the first-effect evaporator, the second-effect evaporator and the third-effect evaporator are connected in parallel with each other, and are heated by secondary steam compressed by a steam compressor.

[0029] The three heating steam pipes of the shell side (inlet) of the first effect evaporator, the second effect evaporator and the third effect evaporator connected in parallel are combined into one pipe and connected to the outlet of the steam compressor. In other words, the outlet of the steam compressor is divided into three routes, which are respectively connected to the shell side inlet of the first effect evaporator, the second effect evaporator and the third effect evaporator.

[0030] The secondary steam pipeline of the tube-side gas phase space (outlet) of the first-effect evaporator and the outlet pipeline of the TVR heat pump are connected in parallel to the inlet pipeline of the steam compressor and connected to the steam compressor together.

[0031] The secondary steam pipeline of the tube-side gas phase space (outlet) of the II-effect evaporator and the matching (for example, the plant area) high-pressure raw steam pipeline are respectively connected to the low-pressure side interface (suction steam interface) and the high-pressure side interface (power steam interface) of the TVR heat pump. The mixed steam is sent out from the medium-pressure side interface (outlet) of the TVR heat pump, and then merged with the secondary steam pipeline of the tube-side gas phase space (outlet) of the I-effect evaporator and enter the steam compressor together.

[0032] The secondary steam pipeline of the shell-side gas phase space (outlet) of the III-effect evaporator, or the secondary steam flashed out, is connected to the condenser for condensation, and the condensed water enters the steam-water separator, and the separated low-temperature condensed water is discharged.

[0033] The gas phase space pipeline of the steam-water separator is connected to a matching vacuum pipeline (for example, in a factory area) to control the evaporation temperature of the III-effect evaporator.

[0034] The following is an example of a field use of the present invention to specifically illustrate the working process / use of the present invention.

[0035] The feed temperature of dilute sulfuric acid is 25°C, the feed amount is 33.33 tons / hour, the feed concentration is 31.605%, and the discharge concentration of concentrated sulfuric acid is required to be ≥50%, and the evaporation amount is ≥12.261 tons / hour.

[0036] Working parameters of each effect evaporator:

[0037]

[0038]

[0039] Compressor operating parameters:

[0040] Number of compressors 1 unit Compressor temperature rise 20℃ temperature rise (saturation) Compressor steam flow 12 tons / hour Compressor shaft power 545kW

[0041] TVR heat pump working parameters:

[0042]

[0043] Feed preheating process: The 33.33 tons / hour room temperature feed dilute sulfuric acid is heated by the first-stage preheater, the temperature rises from 25°C to 56°C, then enters the second-stage preheater, is heated to 102°C by raw steam, and then enters the first-effect evaporator.

[0044] Concentration process of feed in the first-effect evaporator: the dilute sulfuric acid entering the first-effect evaporator is continuously concentrated, and at the same time, 6.32 tons / hour of 90°C (based on saturation thermometer) secondary steam is continuously evaporated from the separation chamber of the first-effect evaporator. The secondary steam enters the inlet of the steam compressor and is compressed and heated by the compressor.

[0045] Concentration process of feed in the II-effect evaporator: when the concentration of dilute sulfuric acid in the I-effect evaporator reaches 39% (mass percentage concentration, the same below), the feed is continuously transferred from the I-effect evaporator to the II-effect evaporator 8, and at the same time, 3.60 tons / hour of 82°C (based on the saturation temperature) secondary steam is continuously evaporated from the separation chamber of the II-effect evaporator. The secondary steam enters the TVR heat pump and is compressed into 0.070MPa (corresponding to saturation temperature 90°C) medium-pressure steam by the 0.6MPa high-temperature raw steam introduced by the TVR heat pump, and then enters the inlet of the steam compressor and is compressed and heated by the compressor.

[0046] Concentration process of feed in III-effect evaporator: when the concentration of dilute sulfuric acid in II-effect evaporator reaches 45%, the feed is continuously transferred from II-effect evaporator to III-effect evaporator, and at the same time, 2.342 tons / hour of secondary steam at 65°C (according to saturation thermometer) is continuously evaporated from the separation chamber of III-effect evaporator, and the secondary steam enters the condenser, is condensed into condensate by the cooling circulating water from the corresponding circulation system of the plant area, and enters the steam-water separation tank. The low-temperature condensate separated by the steam-water separation tank is discharged for treatment, and the gas phase space of the steam-water separation tank is connected to the vacuum pipeline from the plant area, and the evaporation temperature of the separation chamber of the III-effect evaporator is always maintained at about 65°C through the vacuum pipeline.

[0047] The secondary steam is compressed and heated up: the secondary steam is separated from the separation chamber of the I-effect evaporator and the separation chamber of the II-effect evaporator, compressed by the high-pressure raw steam in the TVR heat pump and then enters the steam compressor together. After being compressed and heated / pressured to 0.143MPa (the corresponding saturation temperature is 110℃) by the steam compressor, it enters the shell side of the I-effect evaporator, the II-effect evaporator and the III-effect evaporator respectively, and each evaporator is heated and heated. The secondary condensed water condensed in the shell side of each evaporator enters the first-stage preheater to preheat the feed at 25℃ and then discharged.

[0048] When the sulfuric acid concentration in the III-effect evaporator reaches ≥50%, it is sent out as concentrated sulfuric acid.

[0049] The system can adopt a continuous working system, continuously feeding the material to the I-effect evaporator through the two-stage preheater, and continuously sending the concentrated sulfuric acid with a concentration of ≥50% from the III-effect evaporator to maintain the continuous and stable operation of the system.

[0050] The utility model has the following innovative features:

[0051] 1) Compared with the most energy-saving multi-effect MVR evaporation concentration system in the current dilute sulfuric acid concentration industry, the present invention only uses one centrifugal steam compressor and one TVR heat pump to replace the two steam compressors in series in the former, saving the one-time investment cost of one steam compressor and greatly reducing the power consumption of the system, and also saving the later maintenance cost of one steam compressor (8000 hours / time lubricating oil replacement, sliding bearing replacement, steam seal replacement). At the same time, since only one steam compressor is provided, surge is not easy to occur;

[0052] 2) By using a TVR heat pump, the cost of raw steam is basically equal to the power consumption of a steam compressor in the most energy-saving multi-effect MVR evaporation concentration system currently used, but the TVR heat pump is a non-mechanical device and its stability is far better than that of a centrifugal steam compressor.

[0053] The utility model has the advantages of good process operation stability, low operation cost, low one-time investment cost, and controllable waste acid discharge concentration, which is conducive to popularization and application in practice and can be widely used in the evaporation and concentration process of high-boiling-point acid (such as: dilute sulfuric acid waste acid).

[0054] Unless otherwise specified or when one preferred or optional technical means is a further limitation of another technical means, the preferred and optional technical means disclosed in the present utility model can be arbitrarily combined to form several different specific implementation methods.

Claims

1. A waste sulfuric acid recovery and evaporation system, comprising: The multi-effect evaporator is composed of an effect I evaporator, an effect II evaporator and an effect III evaporator. The tubes of the effect I evaporator, the effect II evaporator and the effect III evaporator are connected in series in sequence. The tube inlet of the effect I evaporator is connected to the dilute sulfuric acid input pipe, the tube outlet of the effect III evaporator is connected to the concentrated sulfuric acid output pipe, and the shell inlet of the effect I evaporator is connected to the high-pressure raw steam pipe. It is characterized by further comprising: The steam compressor has a steam output pipeline divided into three routes, which are respectively connected to the shell side inlet of the first effect evaporator, the second effect evaporator and the third effect evaporator, and the secondary steam output of the first effect evaporator is connected to the steam inlet of the steam compressor; TVR heat pump, the pressure side interface is connected to the inlet of the steam compressor, the high pressure side interface is connected to the high pressure raw steam pipe, and the secondary steam output of the II effect evaporator is connected to the low pressure side interface of the TVR heat pump; Condenser, the secondary steam output of the III-effect evaporator is connected to the condensation inlet of the condenser; The steam-water separation tank, the condensation outlet of the condenser is connected to the inlet of the steam-water separation tank, and the gas phase space outlet of the steam-water separation tank is connected to the vacuum pipeline.

2. The waste sulfuric acid recovery and evaporation system as claimed in claim 1, characterized in that The vacuum pipeline is provided with a control device for controlling the vacuum degree of the gas phase space of the steam-water separation tank.

3. The waste sulfuric acid recovery and evaporation system as claimed in claim 1, characterized in that The refrigerant inlet and outlet of the condenser are respectively connected to the water supply pipe and the water return pipe of the refrigeration system.

4. The waste sulfuric acid recovery and evaporation system as claimed in claim 1, characterized in that The secondary steam of the first effect evaporator, the second effect evaporator and the third effect evaporator is respectively drawn out from the top of the separation chamber of each evaporator.

5. The waste sulfuric acid recovery and evaporation system according to claim 1, characterized in that A steam input main pipe is provided at the inlet of the steam compressor, and the secondary steam output of the I-effect evaporator and the medium-pressure side interface of the TVR heat pump are respectively connected to the steam input main pipe of the steam compressor through their own connecting pipes, thereby realizing the connection between the secondary steam output of the I-effect evaporator and the medium-pressure side interface of the TVR heat pump and the inlet of the steam compressor.

6. The waste sulfuric acid recovery and evaporation system according to any one of claims 1 to 5, characterized in that A first-stage preheater is also provided, the heat absorbing medium channel of the first-stage preheater is connected in series to the dilute sulfuric acid input pipe, and the shell side outlet of the first-effect evaporator is connected to the heat releasing medium inlet of the first-stage preheater.

7. The waste sulfuric acid recovery and evaporation system as claimed in claim 6, characterized in that The shell side outlet of the III effect evaporator is connected to the water inlet of the II effect evaporator, the shell side outlet of the II effect evaporator is connected to the water inlet of the I effect evaporator, the water inlet of the II effect evaporator is connected to the shell side liquid phase space of the II effect evaporator, and the water inlet of the I effect evaporator is connected to the shell side liquid phase space of the I effect evaporator.

8. The waste sulfuric acid recovery and evaporation system as claimed in claim 6, characterized in that The heat release medium inlet of the first-stage preheater is connected to the high-temperature condensate discharge pipe.

9. The waste sulfuric acid recovery and evaporation system as claimed in claim 6, characterized in that A second-stage preheater is also provided. The heat-absorbing medium channel of the second preheater is connected in series to the dilute sulfuric acid input pipe and is located between the first-stage preheater and the first-effect evaporator. The high-pressure raw steam pipe is connected to the heat-releasing medium inlet of the second-stage preheater.

10. The waste sulfuric acid recovery and evaporation system according to claim 9, characterized in that The heat release medium outlet of the second-stage preheater is connected to the return water pipeline of the high-pressure steam boiler system.

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