How to Design a heat pump drying system for drying production 2022-04-23
How to Design a heat pump drying system for drying production with the most stable and reliable drying unit project ? Here is a good example to the project with an energy-saving transformation project of leather gelatin long net drying production line system. The process flow of the project is fresh air - medium efficiency filtration - fresh air pretreatment - return air of the production line - medium efficiency filter - dehumidification of lithium chloride solution - air supply cabinet - heating and drying in the drying room - exhaust fan - exhaust (return air), with a total circulating air volume of 90000 M ³/ h. The low-temperature dry air dehumidified by the lithium chloride solution dehumidifier enters the long net drying room and is heated by steam to meet the drying process requirements. Part of the dried high-temperature and high humidity air is directly discharged outdoors through the exhaust fan, and part of it returns to the air conditioning cabinet and lithium chloride solution regenerator. Such circulation will discharge great heat every day, resulting in serious energy waste. According to the process production requirements, this design includes the design contents of production line chilled water, drying room hot water and exhaust heat recovery .

1: Original configuration of production line

Content

refrigeration unit

Heating unit

Cold heat

930kw

1860kw

energy consumption

185kw

2.65m³steam

Hot and cold water temperature

12/7

75/55

Drying room temperature

4 air chamber 40 , relative humidity 55%, 8 air chamber 55 , 18%


2: Heat recoverable from the production line

Num

Cooling equipment

Enthalpy of temperature and humidity at state point

Airflow

Heat recovery

1

4 air chamber exhaust

4055%108kj/kg

15000m³/h

164kw

2

8 exhaust of air chamber

5518%102kj/kg

10000m³/h

111kw

3

Regeneration exhaust

4055%108kj/kg

20000m³/h

250kw

4

Return air of air cabinet

4040%108kj/kg

45000m³/h

515kw

Total

1040kw


Project design
1.Description of heating system transformation
The project is designed by H.Stars Group and adopted with two high-temperature water source heat pump units, which are connected in series to the heating return water of the original system to the steam heating section. The heating return water of the original system is first heated by adding the primary and secondary heating of the high-temperature water source heat pump unit. If the outlet water temperature of the heat pump does not reach the set 75 ℃ after heating, the steam heating will start automatically. The heating capacity of the primary high temperature water source heat pump unit is 818kw and the input power is 235Kw; The heating capacity of two-stage high temperature water source heat pump unit is 806kw and the input power is 265KW.


2. Description of exhaust heat recovery transformation :
A 10³m is added in the design  The square insulated water tank transmits 15 ℃ cold water to each heat recovery ceiling air cabinet through the circulating pump, and the 20 ℃ hot water heated by exhaust air returns to the insulated water tank for heating by high-temperature heat pump unit; Reduce the enthalpy of exhaust air and reduce the surrounding thermal pollution.


3. Description of return air heat recovery Transformation:
The return air contains a large amount of water vapor and high enthalpy. A ceiling heat recovery air cabinet is installed on the return air duct to reduce the water vapor content and enthalpy of the return air, reduce the energy consumption of lithium chloride dehumidifier, and the recovered heat is supplied to the high-temperature heat pump unit.


4. Recycling instructions of heat pump chilled water in summer :
The system was originally equipped with a 930kw refrigerating capacity refrigeration unit to cool and dehumidify the fresh air in summer and the lithium chloride dehumidifier. The water supply temperature is 12 / 7 ℃, while the heat pump unit can adjust the water temperature at the cold source side to 12 / 7 ℃ when working in summer. The supply and return water at the cold source side can directly replace the supply and return water of the original refrigeration unit and reduce the operation energy consumption of the original system.


Project system diagram


hot water and exhaust heat recovery Project system diagram


Program advantages
1. The high-temperature water source heat pump unit is used for both cooling and heating. The energy efficiency ratio of the unit is more than 3.0 and the comprehensive energy efficiency ratio is as high as 7.0. The operation energy consumption is low, saving more than 50% of the operation cost compared with the original system .


2. Reclaiming the heat from the exhaust of the original system for heating can kill two birds with one stone. First, the heat pump unit has high efficiency and low operation energy consumption; Second, reduce the heat and water vapor of exhaust air, reduce emissions and improve the surrounding environment .


3. Recover the heat and water vapor of the return air of the original system, that is, reduce the water vapor and enthalpy of the return air, reduce the energy consumption of re dehumidification of the return air and reduce the operation cost .


4. When working in summer, the supply and return water temperature at the cold source side of the high-temperature heat pump unit can also be adjusted to replace the original refrigeration unit, reduce the service time of the original refrigeration unit and reduce the system operation cost


5. The whole system adopts full-automatic control and is automatically put into operation according to temperature changes to reduce energy consumption.
6. The project is equipped with a central computer room with integrated design and centralized management to minimize investment cost and operation management cost.


Economic analysis of project operation before and after transformation

Num

Project

Refrigeration and steam heating of refrigeration unit

High temperature water source heat pump unit for cooling and heating

model

unit

Cooling capacity(Kw)

power(KW)

model

unit

Cooling capacity(Kw)

power(KW)

1

Water chiller


Party A's original

1

930

185


New heat pump unit

2

1126

500

2

Steam heating capacity

Party A's original

1

1860

2.65

Heating capacity of heat pump unit

1

1626

0

3

Cooling water pump

Party A's original

1


37

Fan power of air cabinet

1


10

4

Cooling tower

HD-250

1


7.5





5

Total cooling power

229.5

0

6

Total heating power

2.65T steam

510kw

7

Cooling operation mode

Cooling tower+water chiller

Cold recovery of heat pump unit

8

Annual operation days

(D)

90

90

9

Daily running time(H)

24

24

10

Annual operation time(H)

2,160

2,160

11

Annual average operating load rate(%)

0.80

0.80

12

Annual cooling power consumption(KWH)

396,576

0

13

Customer electricity billing is 0.6yuan/KWH

237,946

0

14

Cost saving of cooling

237,946

15

Heating operation mode

steam

Heat pump unit

16

Annual operation days

(D)

360

360

17

Daily running time(H

24

24

18

Annual operation time(H

8,640

8,640

19

Annual average operating load rate(%)

0.80

0.80

20

Annual power consumption of heat pump unit in machine room(KWH)

18,317

3,525,120

21

Customer electricity billing is 0.35/KWH,steam 200yuan/t

3,663,360

1,339,546

22

Saving cost of heating

2,323,814

23

Total annual savings

2,474,513

24

Energy saving rate

68%



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