CN108981221A - The system and method to be freezed using steam condensate waste heat - Google Patents

Abstract

The invention relates to a system for refrigerating by using the waste heat of steam condensate, which includes a generator. The ammonia gas generated by heating in the generator enters an evaporative condenser through an ammonia gas pipeline, and the ammonia gas is condensed into a liquid through the evaporative condenser. Ammonia, and enter the liquid ammonia storage tank through the liquid ammonia pipeline, the liquid ammonia in the liquid ammonia storage tank enters the external cooler through the pipeline, and the liquid ammonia becomes low-pressure ammonia after absorbing heat through the external cooler, and then enters the ammonia gas for absorption The ammonia-poor solution in the ammonia absorber absorbs low-pressure ammonia and becomes a rich ammonia solution. The rich ammonia solution is pumped into the exchanger through the rich liquid pressure pump, and enters the generator after absorbing heat in the exchanger. The ammonia-lean solution in the generator is cooled by the exchanger and then enters the ammonia gas absorber. This system uses the waste heat of the steam condensate to raise the pressure of the low-pressure ammonia and then lower the temperature to obtain the high-pressure liquid ammonia to supply the external cooler for refrigeration, thereby replacing the traditional high-power ammonia refrigeration compressor, and realizing the beneficial effect of energy saving .

Description

System and method for utilizing steam condensate waste heat for refrigeration

technical field

The invention relates to a waste heat refrigeration system, in particular to a refrigeration system and a refrigeration method using the waste heat of steam condensate.

Background technique

In the process of chemical production, the rational use of steam condensate waste heat is directly related to the economic benefits and carbon emissions of enterprises, and it is also the only way to achieve sustainable economic development. At present, this part of waste heat is difficult to recycle through existing technologies, and at the same time, it cannot be directly discharged into the environment. It can only be treated by circulating cooling water to cool down, resulting in great waste. In the freezing process of the combined alkali unit, it is necessary to consume external energy to provide liquid ammonia refrigeration to the external cooler. At present, the compressor is used to compress the low-pressure gas ammonia to the high-pressure gas ammonia, which consumes additional electric energy. How to apply the waste heat of steam condensate to the freezing process in the combined alkali plant has also become a major research topic for chemical production enterprises.

Contents of the invention

In order to overcome the above-mentioned defects, the present invention provides a system for refrigeration by using the waste heat of steam condensate, which uses the by-product steam condensate produced in the calcination process to generate the refrigerant liquid ammonia required for the refrigeration process, so that the waste heat is recovered Utilization saves cost and reduces energy consumption.

The technical scheme that the present invention adopts in order to solve its technical problem is:

A system for refrigerating by using the waste heat of steam condensate, including a generator, an evaporative condenser, an external cooler, an ammonia absorber and an exchanger, the generator is provided with a steam condensate inlet and a steam condensate outlet, The ammonia gas generated by heating in the generator enters the evaporative condenser through the ammonia gas pipeline, and the ammonia gas is condensed into liquid ammonia through the evaporative condenser and enters the liquid ammonia storage tank through the liquid ammonia pipeline. The liquid ammonia enters the external cooler through the pipeline, and the liquid ammonia becomes low-pressure ammonia gas after being absorbed by the external cooler and enters the ammonia gas absorber. The poor ammonia solution in the ammonia gas absorber absorbs the low-pressure ammonia gas and becomes rich ammonia. The ammonia-rich solution is pumped into the exchanger through the rich liquid pressurized pump, and enters the generator after absorbing heat in the exchanger, and the ammonia-lean solution in the generator enters the ammonia gas absorber after being cooled by the exchanger.

Preferably, a cooler is also provided between the exchanger and the ammonia gas absorber, and the ammonia-lean solution coming out of the exchanger is further cooled by the cooler and then enters the ammonia gas absorber.

Preferably, the cooler is a water-cooled exchanger, and the cooler is provided with a water inlet and a water outlet for circulating water.

Preferably, the ammonia gas absorber is also connected with a lean liquid circulation pump, and the lean liquid circulation pump is used to cyclically spray the lean ammonia solution into the ammonia gas absorber.

Preferably, the ammonia gas in the generator enters the evaporative condenser after the primary effect filter and the gas-liquid separator.

Preferably, the primary effect filter is arranged on the top of the generator, and the liquid droplets separated from the gas-liquid separator return to the generator through a pipeline.

Preferably, the ammonia absorber is provided with a liquid level controller, and an automatic regulating valve is provided on the steam condensate inlet pipeline, and the automatic regulating valve can automatically adjust the flow rate of the steam condensate according to the temperature in the generator.

The present invention also provides a method for refrigerating by using the waste heat of steam condensate, the steps are as follows:

Step 1: Saturated steam at about 150°C, a by-product of the calcination process, enters the generator through the condensate inlet, and heats the rich ammonia solution in the generator to make it into ammonia gas and ammonia-lean solution. The ammonia gas passes through the ammonia gas pipe The road enters the evaporative condenser, and the high-temperature lean ammonia solution enters the exchanger;

Step 2: Ammonia gas is cooled to saturated liquid ammonia through the evaporative condenser, and the liquid ammonia flows into the liquid ammonia storage tank through the liquid ammonia pipeline, and is sent to the external cooler for refrigeration by the pressure of the liquid ammonia storage tank itself;

Step 3: Liquid ammonia absorbs heat in the external cooler to become low-pressure ammonia gas and then enters the ammonia gas absorber, and the ammonia-poor solution in the ammonia gas absorber absorbs low-pressure ammonia gas and becomes a rich ammonia solution;

Step 4: The ammonia-rich solution in the ammonia gas absorber is pumped into the exchanger through the rich liquid booster pump, and enters the generator after heat exchange with the high-temperature lean ammonia solution, and the rich ammonia solution can be recycled by repeating step 1;

Step 5: The ammonia-poor solution in the generator is cooled by the exchanger, then enters the cooler for further cooling, and then enters the ammonia gas absorber, repeating step 3 for the ammonia-poor solution to be recycled.

Preferably, in step 1, after the ammonia gas in the generator passes through the primary effect filter on the top of the generator to remove mist, then passes through the gas-liquid separator to remove the trace liquid droplets carried in the ammonia gas, and finally enters the evaporative condenser.

Preferably, in Step 3, the ammonia gas absorber is also connected to a lean liquid circulation pump, and the lean liquid circulation pump is used to cyclically spray the lean ammonia solution into the ammonia gas absorber.

The beneficial effects of the present invention are:

1) This system uses the waste heat of steam condensate to raise the pressure and then lower the temperature of low-pressure ammonia, so as to obtain high-pressure liquid ammonia and supply it to the external cooler for refrigeration, thereby replacing the traditional high-power ammonia refrigeration compressor, thereby realizing energy saving. Beneficial effect;

2) In this system, the high-temperature condensate output at about 150°C from the calcination process is used. After the waste heat of the freezing process is utilized, the temperature drops below 100°C, thus avoiding the flashing of the original 150°C condensate during long-distance transportation. The resulting pipeline vibration, noise, and instantaneous pressure are too high, which will cause the rupture of the pipeline and the water hammer (water hammer) effect, which will bring great destructive safety production hazards. The cooled condensate is first exchanged with the boiler feed water. Heat cooling, and then exchange heat with desalted raw water to cool down, enter the refined mixed bed, and use it as boiler feed water, no need to add cooling devices for circulating water, saving costs and reducing energy consumption;

3) The ammonia solution in this system uses a new type of multi-element refrigerant, which includes lithium nitrate, potassium hydroxide, amide compounds, lithium chromate and other components, and has a high solubility for ammonia and a High vaporization temperature is not easy to carry out with the gas when evaporating, and the physical and chemical properties are very stable. Using this working medium, the compressible gas that originally needs to be completed by the screw compressor is transformed into an incompressible liquid through the process of boosting the pressure. Effective use Waste heat resources while greatly reducing power loss;

4) This system is conducive to the popularization and application of new technologies for the recycling and utilization of low-grade heat sources such as waste heat and waste heat, and reduces the operating costs of users. It has a good energy-saving and emission-reduction demonstration effect and social benefits in the chemical industry.

Description of drawings

Fig. 1 is the schematic diagram of refrigeration system of the present invention;

Fig. 2 is the refrigeration method flowchart of the present invention;

In the figure: 10-generator, 11-primary effect filter, 12-gas-liquid separator, 20-evaporative condenser, 21-liquid ammonia storage tank, 30-external cooler, 40-ammonia gas absorber, 41 - lean liquid circulation pump, 42 - rich liquid pressure pump, 50 - exchanger, 60 - cooler.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Apparently, the described embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

Embodiment: as shown in Figure 1, a kind of system that utilizes steam condensate waste heat to carry out refrigeration, comprises generator 10, evaporative condenser 20, external cooler 30, ammonia gas absorber 40 and exchanger 50, described generation The steam condensate inlet and the steam condensate outlet are provided on the generator 10. The ammonia gas generated by heating in the generator 10 enters the evaporative condenser 20 through the ammonia gas pipeline, and the ammonia gas is condensed into liquid ammonia through the evaporative condenser and Enter the liquid ammonia storage tank 21 through the liquid ammonia pipeline, and the liquid ammonia in the liquid ammonia storage tank 21 enters the external cooler 30 through the pipeline, and the liquid ammonia becomes low-pressure ammonia after absorbing heat through the external cooler and enters the ammonia gas absorber 40. The ammonia-poor solution in the ammonia gas absorber 40 absorbs the low-pressure ammonia gas and becomes a rich ammonia solution. The ammonia-rich solution is pumped into the exchanger 50 through the rich liquid pressurized pump 42, and enters the gaseous ammonia solution after absorbing heat in the exchanger. The ammonia-lean solution in the generator 10 enters the ammonia gas absorber 40 after being cooled by the exchanger 50 . In this system, the waste heat of the 150°C saturated steam condensed water produced by the calcination process is used to raise the pressure of the low-pressure ammonia and then lower the temperature to obtain high-pressure liquid ammonia for use in the external cooler, thus replacing a high-efficiency ammonia refrigeration compressor. Energy-saving effect. Taking the calcining process to produce 120 tons of 150°C saturated steam condensate per hour as an example, the steam condensate is cooled from 150°C to 90°C to generate 8500Kw of heat, and part of the energy is used to compress 0.4MPa low-pressure gas ammonia to 1.3MPa high-pressure gas Ammonia, its value is about 1600Kw; the remaining heat is used to repeatedly heat up the solvent of the ammonia solution. The ammonia solution in this system adopts a new type of multi-element refrigerant, which converts the compressible gas that originally needs to be completed by the screw compressor into an incompressible liquid through the pressure boosting process, which greatly reduces the power consumption while effectively utilizing waste heat resources. .

Further, a cooler 60 is provided between the exchanger 50 and the ammonia gas absorber 40 , and the ammonia-lean solution coming out of the exchanger 50 is further cooled by the cooler and enters the ammonia gas absorber 40 . The role of the exchanger 50 is to exchange heat between the low-temperature rich ammonia solution from the ammonia absorber and the high-temperature lean ammonia solution from the generator. After the generator heats up, it enters the generator, and the pressure of the generator is 1.3MPa, so the lean ammonia solution coming out of the generator is enough to overcome the resistance and reach the ammonia gas absorber. The cooler 60 is a water-cooled exchanger, and the cooler is provided with a water inlet and a water outlet for circulating water. After being further cooled by circulating cooling water in the cooler, the lean ammonia solution enters the ammonia gas absorber, which is beneficial to the absorption of ammonia gas by the lean ammonia solution.

The ammonia gas absorber 40 is also connected with a lean liquid circulation pump 41, and the lean liquid circulation pump 41 is used to cyclically spray the lean ammonia solution into the ammonia gas absorber. The role of the lean liquid circulation pump 41 is to increase the spray density, which is beneficial to the absorption of ammonia by the solvent. The ammonia gas in the generator 10 enters the evaporative condenser 20 after the primary filter 11 and the gas-liquid separator 12 in sequence. The primary filter 11 is arranged on the top of the generator 10, and the liquid droplets separated from the gas-liquid separator 12 return to the generator 10 through the pipeline. The primary effect filter 11 is a mist remover for filtering out the mist in the ammonia gas, and the gas-liquid separator 12 further separates the liquid droplets carried in the ammonia gas, and the liquid in the ammonia gas after the above two filtering procedures The content is reduced to below 0.1ppmw, which improves the subsequent refrigeration efficiency. The gas-liquid separator used in this embodiment is the product of Pall Filter Co., Ltd.

The ammonia absorber 40 is provided with a liquid level controller, and an automatic regulating valve is provided on the steam condensate inlet pipeline, and the automatic regulating valve can automatically adjust the flow rate of the steam condensate according to the temperature in the generator 10 . Automated control is adopted here. There is a software control system inside the automatic regulating valve. The software control system is electrically connected to the thermometer in the generator. After the software control system obtains the temperature in the generator from the thermometer, it adjusts the automatic The opening degree of the valve is adjusted to ensure the stability of the heat exchange in the generator. This automatic control is a conventional technology and will not be further described in detail here. In order to protect the rich liquid booster pump 42, a liquid level controller is installed on the ammonia gas absorber, so as to ensure that the booster pump has sufficient suction height, prevent cavitation from occurring and make the lubricating fluid of the bearing have sufficient pressure ; A load relay is provided in the circuit of the rich liquid booster pump 42, and a temperature relay is installed on the outlet pipeline of the rich liquid booster pump 42, and the load relay is used to protect the motor and impeller; the temperature relay is used to Prevent the bearing from being damaged due to the high temperature of the lubricating oil; in order to ensure the safe operation of the system, there is also a spare rich liquid pressure pump.

Refrigeration method of the present invention:

As shown in Figure 2, a method of utilizing the waste heat of steam condensate for refrigeration, the steps are as follows:

Step 1: Saturated steam at about 150°C, a by-product from the calcination process, enters the generator 10 through the condensate inlet, and heats the ammonia-rich solution in the generator to make it into ammonia gas and ammonia-poor solution, and the ammonia gas passes through the ammonia The gas pipeline enters the evaporative condenser 20, and the high-temperature lean ammonia solution enters the exchanger 50;

Step 2: Ammonia gas is cooled to saturated liquid ammonia through the evaporative condenser 20, and the liquid ammonia flows into the liquid ammonia storage tank 21 through the liquid ammonia pipeline, and is sent to the external cooler 30 for refrigeration by the pressure of the liquid ammonia storage tank itself ;

Step 3: Liquid ammonia absorbs heat in the external cooler 30 and becomes low-pressure ammonia gas and then enters the ammonia gas absorber 40, and the poor ammonia solution in the ammonia gas absorber absorbs low-pressure ammonia gas and becomes a rich ammonia solution;

Step 4: The ammonia-rich solution in the ammonia gas absorber 40 is pumped into the exchanger 50 through the rich liquid booster pump 42, and enters the generator 10 after heat exchange with the high-temperature lean ammonia solution, and repeats step 1 to recycle the ammonia-rich solution ;

Step 5: The ammonia-poor solution in the generator 10 is cooled by the exchanger 50, then enters the cooler for further cooling, and then enters the ammonia gas absorber 40, and repeats the three steps for the ammonia-poor solution to be recycled. The high-temperature saturated steam condensate at around 150°C is heated to the rich ammonia solution to lower itself below 100°C, and most of the low-boiling ammonia in the rich ammonia solution evaporates to become high-pressure ammonia gas. The ammonia evaporates to become a poor ammonia solution, and the poor ammonia solution enters the ammonia absorber 40 after cooling through the exchanger 50 (exchanging heat with the rich ammonia solution) and the cooler 60 (using cooling water to cool the poor ammonia solution). The cooled ammonia-poor solution is more conducive to the absorption of ammonia gas. After the high-pressure ammonia gas passes through the evaporative condenser 20 and the external cooler 30, it becomes low-pressure ammonia gas and enters the ammonia gas absorber 40 to be absorbed by the poor ammonia solution, making the ammonia-poor solution The solution becomes a rich ammonia solution, and the rich ammonia solution enters the generator 10 after absorbing the heat of the poor ammonia solution through the exchanger 50. During the whole process, the waste heat of the saturated steam condensate is utilized, and the ammonia solution is recycled.

Wherein, in step one, the ammonia gas in the generator 10 passes through the primary effect filter 11 arranged at the top of the generator to remove mist, then removes the trace liquid droplets carried in the ammonia gas through the gas-liquid separator 12, and finally enters the Evaporative condenser 20. In Step 3, the ammonia gas absorber 40 is also connected to a lean liquid circulation pump 41 , and the lean liquid circulation pump 41 is used to cyclically spray the lean ammonia solution into the ammonia gas absorber 40 .

Economic analysis of this system:

1. Power consumption calculation of this waste heat refrigeration project

① Power consumption of 2 circulating pumps in the waste heat refrigeration unit, the total power of the circulating pumps in the unit is 84kW;

② 1560m ³ /h of circulating water is required, the energy consumption of circulating water is 0.035kWh/m ³ , and the energy consumption of circulating water cooling tower fan is 1560m ³ /h×0.035kWh/m ³ =54.6kW;

③ The energy consumption of the circulating water pump is about twice that of the fan, that is, 109.2kW;

Total power consumption of waste heat utilization unit: 84+54.6+109.2＝247.8kW;

2. Calculation of power consumption of the original set of ammonia refrigeration compressor unit

① The rated power of the main motor of the ammonia refrigeration compressor unit is 1600kW;

② The oil pump motor in the unit is 15Kw, the thin oil station motor is 3Kw, a total of 18Kw;

③The unit is cooled by an evaporative condenser, and each set of ammonia refrigeration compressor unit is equipped with four evaporative condensers with a rated heat transfer capacity of 2000kW, and each set of condensers is equipped with a 7.5kW water pump and two 7.5kW fans;

Condenser power consumption of a single unit: 7.5kWx4+7.5kWx8=90kW.

The total power consumption of the original set of ammonia refrigeration compressor: 1600+15+3+90=1708kW.

3. The electricity cost saved after the system is running

Annual economic benefit: (1708-247.8)×8000×0.71＝8293936 (yuan)

Among them, the electricity fee is: 0.71 yuan/kWh, and the annual calculation is based on 8000 hours; therefore, by using this refrigeration system, more than 800,000 yuan of electricity costs can be saved a year.

It should be pointed out that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent for the present invention should be based on the appended claims.

Claims (10)

1. A system for refrigerating by steam condensate waste heat, characterized in that it comprises a generator (10), an evaporative condenser (20), an external cooler (30), an ammonia absorber (40) and an exchanger (50), the generator (10) is provided with a steam condensate inlet and a steam condensate outlet, and the ammonia gas produced by heating in the generator (10) enters the evaporative condenser (20) through the ammonia pipeline, The ammonia gas is condensed into liquid ammonia through the evaporative condenser and enters the liquid ammonia storage tank (21) through the liquid ammonia pipeline, and the liquid ammonia in the liquid ammonia storage tank (21) enters the external cooler (30) through the pipeline, Liquid ammonia becomes low-pressure ammonia gas after being absorbed by the external cooler and enters the ammonia gas absorber (40), and the poor ammonia solution in the ammonia gas absorber (40) becomes a rich ammonia solution after absorbing low-pressure ammonia gas. The solution is pumped into the exchanger (50) through the rich liquid booster pump (42), and enters the generator (10) after absorbing heat in the exchanger, and the ammonia-lean solution in the generator (10) is cooled by the exchanger (50) After entering the ammonia gas absorber (40). 2. The system according to claim 1, characterized in that: a cooler (60) is also provided between the exchanger (50) and the ammonia gas absorber (40), and from the exchange The ammonia-poor solution coming out of the device (50) enters the ammonia gas absorber (40) after further cooling through the cooler. 3. The system for cooling by utilizing waste heat of steam condensate according to claim 2, characterized in that: the cooler (60) is a water-cooled exchanger, and the cooler is provided with a water inlet and a water outlet for circulating water. 4. The system according to claim 1, characterized in that: the ammonia absorber (40) is also connected to a lean liquid circulation pump (41), and the lean liquid circulation pump (41 ) is used to cyclically spray the lean ammonia solution into the ammonia absorber. 5. The system for refrigerating by utilizing the waste heat of steam condensate according to claim 1, characterized in that: the ammonia in the generator (10) is followed by the primary filter (11) and the gas-liquid separator (12) successively Enter the evaporative condenser (20). 6. The system for refrigerating by utilizing the waste heat of steam condensate according to claim 5, characterized in that: the primary filter (11) is arranged on the top of the generator (10), and the gas-liquid separator (12 ) in the separated droplets through the pipeline back to the generator (10). 7. The system for refrigerating by utilizing the waste heat of steam condensate according to claim 1, characterized in that: the ammonia gas absorber (40) is provided with a liquid level controller, and an automatic adjustment is set on the steam condensate inlet pipeline. A valve, the automatic regulating valve can automatically adjust the flow rate of the steam condensate according to the temperature in the generator (10). 8. A method for refrigerating using steam condensate waste heat, characterized in that: the steps are as follows: Step 1: Saturated steam at about 150°C, a by-product from the calcination process, enters the generator (10) through the condensate inlet, and heats the rich ammonia solution in the generator to make it into ammonia gas and ammonia-lean solution, ammonia gas Enter the evaporative condenser (20) through the ammonia pipeline, and the high-temperature lean ammonia solution enters the exchanger (50); Step 2: Ammonia gas is cooled into saturated liquid ammonia through the evaporative condenser (20), and the liquid ammonia flows into the liquid ammonia storage tank (21) through the liquid ammonia pipeline, and is sent to the external cooling tank by the pressure of the liquid ammonia storage tank itself. Cooling in device (30); Step 3: Liquid ammonia absorbs heat in the external cooler (30) and then enters the ammonia gas absorber (40) after absorbing heat into low-pressure ammonia gas, and the poor ammonia solution in the ammonia gas absorber absorbs low-pressure ammonia gas and becomes a rich ammonia solution; Step 4: The ammonia-rich solution in the ammonia gas absorber (40) is pumped into the exchanger (50) through the rich liquid booster pump (42), enters the generator 10 after heat exchange with the high-temperature lean ammonia solution, and repeats step 1 The ammonia-rich solution can be recycled; Step 5: The ammonia-poor solution in the generator (10) is cooled by the exchanger (50), then enters the cooler for further cooling, and then enters the ammonia gas absorber (40), repeating step 3 for the ammonia-poor solution to be recycled. 9. The method of utilizing steam condensate waste heat to refrigerate according to claim 8, characterized in that: in step one, the ammonia in the generator (10) passes through the primary filter (11) located at the top of the generator ) to remove the mist, then remove the trace droplets carried in the ammonia by the gas-liquid separator (12), and finally enter the evaporative condenser (20). 10. The method for refrigerating by using the waste heat of steam condensate according to claim 8, characterized in that: in step 3, the ammonia gas absorber (40) is also connected to a lean liquid circulating pump (41), the lean liquid The liquid circulation pump (41) is used to spray the ammonia-lean solution into the ammonia gas absorber (40) cyclically.