CN105169727A - Evaporation and concentration system and process for diluted hydrochloric acid generated by production of chlorinated polyethylene - Google Patents

Abstract

The invention relates to an evaporation and concentration system and process for dilute hydrochloric acid produced in the production of chlorinated polyethylene; the treatment of dilute hydrochloric acid produced in chemical production is a worldwide problem, and evaporation and concentration is the preferred method for dilute hydrochloric acid treatment, but due to high energy consumption and economical It is uneconomical and cannot be put into practice; according to the principle of comprehensive utilization of heat energy, the present invention combines the evaporation and concentration system of the dilute hydrochloric acid produced by the production of chlorinated polyethylene with the normal production of chlorinated polyethylene, that is, when fully utilizing chlorinated polyethylene On the basis of the waste heat generated in production, a small amount of energy consumption is supplemented to complete the evaporation and concentration of dilute hydrochloric acid generated in the production of chlorinated polyethylene; the invention belongs to a typical process of "treating waste with waste, saving energy and reducing emission".

Description

Evaporation and concentration system and process of dilute hydrochloric acid produced in the production of chlorinated polyethylene

technical field

The invention belongs to the technical field of waste recycling in chemical enterprises, and in particular relates to a process for evaporating and concentrating dilute hydrochloric acid produced in the production of chlorinated polyethylene.

Background technique

The treatment of dilute hydrochloric acid (5-10%) produced by large-scale chlorinated polyethylene enterprises based on the chlor-alkali industry is a worldwide problem. The dilute hydrochloric acid produced by a domestic chlorinated polyethylene enterprise (120,000 tons of CPE/a) is discharged as waste acid water after being neutralized with alkaline substances (limestone or carbide slag), and the cost is about 7 million yuan /a, not only increases the economic burden of the enterprise, but also a huge waste of resources. Therefore, the development of suitable dilute hydrochloric acid recovery technology to make it a resource and realize zero discharge of waste hydrochloric acid has good economic benefits and can also promote energy conservation and emission reduction of enterprises.

Evaporation and concentration is the preferred treatment method for dilute hydrochloric acid, but it cannot be implemented due to high energy consumption and uneconomical economics; that is to say, there is no evaporation and concentration treatment for dilute hydrochloric acid produced by chlorinated polyethylene enterprises at home and abroad Craft reports. Based on the principle of comprehensive utilization of heat, the evaporation and concentration of dilute hydrochloric acid is combined with the heat supply of chlorinated polyethylene production. On the basis of making full use of production waste heat, less energy consumption is added to realize the evaporation and concentration of dilute hydrochloric acid. After concentration, the hydrochloric acid can be directly for production. Therefore, the present invention belongs to a typical process of "treating waste with waste, saving energy and reducing emission".

Contents of the invention

The object of the present invention is to provide a kind of evaporating and concentrating process of dilute hydrochloric acid produced in the production of chlorinated polyethylene, that is to combine the evaporating and concentrating of dilute hydrochloric acid with the heat supply of chlorinated polyethylene production, and to supplement Reduce energy consumption, and realize the evaporation concentration recovery of dilute hydrochloric acid.

In order to achieve the above object, technical solution of the present invention is achieved in that way:

The system of the present invention comprises a chlorination kettle connected to polyethylene, chlorine gas, hydrochloric acid, and hot steam pipelines from the second mixer respectively. The chlorinated polyethylene from the drier is connected to the pipeline of the cyclone separator and the process wind generator respectively, and the chlorinated polyethylene from the dryer is recycled and packaged; the waste heat steam pipeline from the chlorination kettle is connected to the first mixer, and the waste heat steam from the drier is The waste heat is connected to the first mixer through pipelines; the waste heat steam pipeline from the first mixer is connected to the heat fluid inlet of the heat exchanger, and the condensate water pipeline is respectively connected to the heat fluid outlet of the heat exchanger and the filter; the centrifuge The dilute acid water obtained by centrifugation is connected to the filter through the pipeline; the dilute acid from the filter is connected to the cold fluid inlet of the heat exchanger through the pipeline, and after preheating, the dilute acid flows out from the cold fluid outlet of the heat exchanger through the pipeline and The material inlet of the evaporator is connected; the low-temperature steam evaporated from the evaporator is connected to the inlet of the alkali washing tank through the pipeline, and the low-temperature steam from the alkali washing tank is connected to the second mixer through the pipeline; the concentrated acid from the evaporator is recovered; The high-temperature steam generated by the steam boiler is connected to the second mixer through the pipeline, and the hot steam from the second mixer is connected to the hot steam inlet of the chlorination kettle, the evaporator and the hot steam inlet of the process wind generator through the pipeline; The hot steam fed into the process air generator is used for air heating, and after heat exchange, it becomes low-temperature reflux steam and is connected to the steam boiler through pipes; the hot steam fed into the evaporator is used for evaporation and concentration of dilute acid, and after heat exchange, it becomes condensed water for recovery ;The hot steam passed into the chlorination kettle is used for heating in the chlorination reaction, and after heat exchange, it becomes waste heat steam and is connected to the first mixer through the pipeline; It is connected with a dryer for drying of chlorinated polyethylene, and then becomes waste heat, which is sent to the first mixer through a pipeline.

The return steam of the process wind generator is connected with the high-temperature steam boiler through pipelines.

The process of the present invention is as follows: first, the waste heat steam obtained after the chlorination reaction in the chlorination tank and the waste heat mainly hot air from the drier are mixed with the first mixer to become a new steam heat source, and the dilute steam from the supply filter is mixed. Preheating before acid evaporation and concentration, the preheated dilute acid enters the evaporator and is heated by hot steam to evaporate and concentrate to obtain concentrated acid; the evaporated low-temperature steam is washed with alkali and mixed with high-temperature steam generated by the boiler to form a chlorination tank and process The wind normally produces the hot steam needed for heating and the hot steam needed for the evaporator to evaporate and concentrate the dilute acid. The condensed water from the evaporator is directly discharged or used as filter flushing supplementary water.

Based on the principle of comprehensive utilization of heat, the present invention combines the evaporation and concentration of dilute hydrochloric acid with the heat supply produced by chlorinated polyethylene. On the basis of making full use of production waste heat, it supplements less energy consumption and realizes the evaporation and concentration of dilute hydrochloric acid. After concentration, the hydrochloric acid It can be directly used in production; therefore, the present invention belongs to a typical process of "treating waste with waste, saving energy and reducing emission".

Description of drawings

Fig. 1 is a process flow diagram of the present invention.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings.

Referring to the figure, the system of the present invention includes a chlorination kettle connected to polyethylene, chlorine gas, hydrochloric acid, and the hot steam pipeline coming out of the second mixer respectively, and the material outlet of the chlorination kettle is connected with a filter, a centrifuge, and a drier successively. The dryer is connected with the cyclone separator and the process wind generator pipeline respectively, and the chlorinated polyethylene from the dryer is recycled and packaged; the waste heat steam pipeline from the chlorination kettle is connected with the first mixer, from the drying The waste heat from the heat exchanger is connected to the first mixer through pipelines; the waste heat steam pipeline from the first mixer is connected to the heat fluid inlet of the heat exchanger, and the condensate water pipeline is respectively connected to the heat fluid outlet of the heat exchanger and the filter The dilute acid water obtained by the centrifuge is connected to the filter through the pipeline; the dilute acid from the filter is connected to the cold fluid inlet of the heat exchanger through the pipeline, and the dilute acid flows out from the cold fluid outlet of the heat exchanger after preheating. The pipeline is connected to the material inlet of the evaporator; the low-temperature steam evaporated from the evaporator is connected to the inlet of the alkali cleaning tank through the pipeline, and the low-temperature steam from the alkali cleaning tank is connected to the second mixer through the pipeline; Acid recovery; the high-temperature steam generated by the steam boiler is connected to the second mixer through the pipeline, and the hot steam from the second mixer is respectively connected to the hot steam inlet of the chlorination kettle and the evaporator and the hot steam of the process wind generator through the pipeline. The inlet is connected; the hot steam fed into the process air generator is used for air heating, and after heat exchange, it becomes low-temperature reflux steam and is connected to the steam boiler through pipes; the hot steam fed into the evaporator is used for the evaporation and concentration of dilute acid, which becomes Condensed water recovery; the hot steam passed into the chlorination tank is used for heating in the chlorination reaction, and after heat exchange, it becomes waste heat steam and is connected to the first mixer through the pipeline; the air delivered by the fan enters the process air generator and becomes hot air after being heated. The hot air is connected to the dryer through the pipeline, and is used for drying the chlorinated polyethylene, and then becomes waste heat, which is sent to the first mixer through the pipeline.

First, the waste heat steam (110-150°C) obtained after the chlorination reaction in the chlorination tank and the waste heat (90-110°C) mainly hot air from the drier are mixed by the first mixer to become (100-120 ℃) new steam heat source, the mass fraction of the supply filter is 5-9% dilute hydrochloric acid (0-30 ℃) preheating before evaporation and concentration, the preheated dilute acid (50-60 ℃) enters the evaporator and passes through the heat Steam is heated, evaporated and concentrated to obtain concentrated acid with a mass fraction of 18-22%. The evaporated low-temperature steam (containing a very small amount of hydrogen chloride) at 70-90°C is washed with alkali and mixed with high-temperature steam at 380-420°C to form chlorinated acid. The kettle and the process air normally produce the hot steam (180-220°C) needed for heating and the hot steam (180-220°C) needed by the evaporator. The condensed water from the evaporator is directly discharged or used as filter flushing supplementary water.

An enterprise produces 100,000 t/a of chlorinated polyethylene. The hot steam temperature required for heating the chlorination kettle and the process air is 200°C, 0.8MPa, 28t/h, 245,000t/a; the waste heat steam discharged from the chlorination kettle is 130°C, normal pressure, 14t/h, and the dryer The exhausted waste heat is 100°C and normal pressure; 30t/h of dilute hydrochloric acid with a mass fraction of 7% is produced, and 270,000t/a requires alkali neutralization treatment.

Preliminary calculations show that the high-temperature steam after combining the dilute hydrochloric acid evaporation and concentration system is 400°C, 1.23MPa, 30t/h, 363,000t/a. The mass fraction of 7% dilute hydrochloric acid is 0°C (calculated according to the winter temperature), 30t/h; the new steam formed after the waste heat steam discharged from the chlorination kettle is mixed with the waste heat discharged from the dryer is 115°C, normal pressure, 15-16t /h. The mass fraction of 7% dilute hydrochloric acid preheated by the heat exchanger has a temperature of 60°C, enters the evaporator (vacuum degree 0.053MPa) and heats up to 80°C for evaporation and concentration; the mass fraction of hydrochloric acid recovered is controlled to 20%, 8t/h; The low-temperature steam (80°C, 0.053MPa, 22t/h) goes through the alkali washing tank (NaOH solution) to neutralize the contained traces of HCl, and then mixes with the high-temperature steam at 400°C, 1.23MPa, 30t/h to become 0.8 MPa, 200°C hot steam, 52t/h are used for chlorination tank heating (14t/h), process air heating (14t/h) and evaporator heating (24t/h). When the pH of the alkaline washing solution in the alkaline cleaning equipment is close to neutral, it is discharged into the electrolytic tank.

The recovered hydrochloric acid (mass fraction 20%) can be directly used in the chlorination reaction of the chlorination kettle, and can also be made into industrial concentrated hydrochloric acid (mass fraction 30-35%) by feeding in hydrogen chloride for sale, and the economic benefit is remarkable.

Claims (3)

1. The evaporation and concentration system of dilute hydrochloric acid produced in the production of chlorinated polyethylene is characterized in that: it includes a chlorination kettle connected to polyethylene, chlorine, hydrochloric acid, and the hot steam pipeline from the second mixer respectively, and the chlorination The material outlet of the kettle is connected to the filter, centrifuge and dryer in turn, and the dryer is connected to the cyclone separator and the process wind generator pipeline respectively. The chlorinated polyethylene coming out of the dryer is recycled and packaged; The waste heat steam pipeline from the dryer is connected to the first mixer, and the waste heat from the dryer is connected to the first mixer through the pipeline; the waste heat steam pipeline from the first mixer is connected to the hot fluid inlet of the heat exchanger, condensed The water pipelines are respectively connected to the hot fluid outlet of the heat exchanger and the filter; the dilute acid water obtained by centrifugation is connected to the filter through the pipeline; the dilute acid from the filter is connected to the cold fluid inlet of the heat exchanger through the pipeline, After the dilute acid is preheated, it flows out from the cold fluid outlet of the heat exchanger and is connected to the material inlet of the evaporator through a pipeline; The road is connected to the second mixer; the concentrated acid from the evaporator is recovered; the high-temperature steam generated by the steam boiler is connected to the second mixer through the pipeline, and the hot steam from the second mixer is connected to the chlorination tank and the chlorination tank through the pipeline respectively. The hot steam inlet of the evaporator is connected with the hot steam inlet of the process wind generator; the hot steam fed into the process wind generator is used for air heating, and after heat exchange, it becomes low-temperature return steam and is connected to the steam boiler through pipes; The hot steam is used for the evaporation and concentration of dilute acid, which is recovered as condensed water after heat exchange; the hot steam passed into the chlorination kettle is used for heating in the chlorination reaction, and after heat exchange, it becomes waste heat steam and is connected to the first mixer through pipelines; the fan The conveyed air enters the process air generator to be heated and becomes hot air. The hot air is connected to the dryer through pipelines for drying chlorinated polyethylene, and then becomes waste heat, which is sent to the first mixer through pipelines. 2. The evaporation and concentration system for dilute hydrochloric acid produced in the production of chlorinated polyethylene according to claim 1, characterized in that: the reflux steam of the process wind generator is connected to the high-temperature steam boiler through pipelines. 3. A process for evaporating and concentrating dilute hydrochloric acid produced in the production of chlorinated polyethylene is characterized in that: firstly, the waste heat steam obtained after the chlorination reaction in the chlorination kettle and the hot air coming out of the drier are mainly waste heat through the first After the mixer is mixed, it becomes a new steam heat source, which supplies the preheating of the dilute acid from the filter before evaporation and concentration. The preheated dilute acid enters the evaporator and is heated by hot steam to evaporate and concentrate to obtain concentrated acid; the evaporated low-temperature steam is washed with alkali After that, it is mixed with the high-temperature steam generated by the boiler to form the hot steam required for the normal production of heating by the chlorination kettle and the process air and the hot steam required for the evaporator to evaporate and concentrate the dilute acid. The condensed water from the evaporator is directly discharged or used as a filter Rinse and add water.