The Design of the Residual Heat Utilization System For the Forging Furnaces’ Flue Gas

Gu Pingdao , Zhang Huasong

School of Environmental Science and Engineering, Dong Hua

University, Shanghai, China

Sustainable Thermal Energy Management in the Process

Industries International Conference SusTEM2011

October 25th – 26th, United Kingdom

OUTLINE

1. Aims and Objectives

2. Energy Consumptions in the Forging Plant

3. Waste Heat Available in the Production

Process

4. Waste Heat Utilization System

5. Results and Analyses

6. Conclusions

Aims and Objectives

Analyses and measurement of the waste

heat from the forging furnaces’ flue gas

Using the waste heat to generate cooling for

the production process and for air-

conditioning in the workshop

Using the waste heat to generate steam and

hot water

Energy Consumptions in the

Forging Plant

The forging process

Figure: the process flow chart of forgings

Energy Consumption in the Plant

Vast ice consumption during heat treatment (hardening) process - The capacity of centrifugal compression refrigeration units is 4800 kW and they consume 1.50x107

kWh of electrical energy each year

Air-conditioning Station generates cooling for workshops and it consumes electrical energy 8.41×108 kWh each year and generate 2.4x1012 kWh of cooling

Air conditioning in offices and living area consumes 3.0x106 kWh electricity each year

Steam consumption is 6160 ton per year

Hot water supply for washing and bath

Energy consumption data in 2009 & 2010

Year

Heavy oil (t)

Natural gas(m3)

Syngas

from coal (m3)

Electricity (kWh)

Coal (t)

2009

173,79 37,562,468 211,905,183 75,844,429 117,607

2010

5,781

42,082,500

169,527700

51,883,400

96,678

Energy consumptions of the furnaces

Type Number Consumption Energy

Heavy oil-fired heating furnace

7(7) 5781 t 2.32 x 1011KJ

Natural heating furnace

14(4)

42,082,535m3

1.497x1012KJ Natural heat

treatment furnace

14(9)

Gas heat treatment furnace

19 162,819,734m3

1.70x1012KJ

Cold water-sinks

No

Name

Size

volume

Cooling quantity

1 8m Ф8000*8000 402m3 20260800KJ

2 1# Ф5000*28000 550m3 27720000KJ

3 2# Ф4800*18200 350m3 17640000KJ

4 3# Ф5000*14000 196m3 9878400KJ

5 4# Ф5000*10000 402m3 20260800KJ

6 5# Ф11000*8800 836m3 42134400KJ

7 6# 3000*3000*3000 27m3 1360800KJ

8 New workshop Ф11000*8000 760m3 38304000KJ

9 Middle sink Ф8000*8000 2800m3

Station air-conditioning

workshop The number of station cooling capacities

First forging workshop 62 The total: 8.41×108 kw.h/year

First forging workshop 72

Heat treatment workshop 104

New workshop 44

Machining Workshop 38

Waste Heat Available in the

Production Process

Flue gas data statistics

1 Average flue gas volume

(Nm3/h) 205×103

2 Maximum flue gas volume (Nm3/h) 341×103

3 Minimum flue gas volume (Nm3/h) 100×103

4 Average flue gas temperature (℃) 650

5 Maximum flue gas temperature

(℃) 738

6 Minimum flue gas temperature (℃) 430

Residual Flue Gas Heat

Utilization System

Schematic diagram of the waste heat utilization system

Lithium-bromide absorption cooling system

System control process of the waste heat utilization system

Results and Analyses

The generation of cooling

Flue gas volume(m3)

Inlet temperature of flue gas(℃)

Outlet temperature of flue gas(℃)

COP

the total cooling capacity QL (KW)

205000

650

170

1.4

53934

The generation of saturated steam

Flue gas volume(m3)

Inlet temperature of flue gas(℃)

Outlet temperature of flue gas(℃)

Inlet temperature of water (℃)

Outlet temperature of saturated steam(℃)

the total saturated steam (T)

205000

170

110

20

100

605,000

The generation of hot water

Flue gas volume(m3)

Inlet temperature of flue gas(℃)

Outlet Temperature of flue gas(℃)

Supply water temperature (℃)

Return water temperature (℃)

the total hot water (kg/h)

the total heat

Qr (kw)

205000

110

75

65

30

792637.6

32336

Summary of Economic Benefits Analysis

Numb

er Name

Initial

investment

(104 yuan)

Economic

efficiency

(104

yuan/year)

Payback

period

(year)

Coal-

saving

(104

t/year)

CO2

emission

reduction

(104

t/year)

One

residual flue gas heat

refrigeration

system for replacing

the ice consumption

1498 468.3 3.2 0.097 0.24

Two

residual flue gas heat

refrigeration

system for replacing

centrifugal

compression

refrigeration

2939.8 1175.5 2.5 0.586 1.46

Three

residual flue gas heat

refrigeration

system for station air-

conditioning and

production air-

conditioning

2697 869.9 3.1 0.434 1.08

Four

residual flue gas heat

refrigeration

system for office and

living area air

conditioning and hot

water supply

11841.4 5148.4 2.3 0.306 7.6

Analysis of Economic Benefits

Making use of the hot waste flue gas not only conserves energy, but also reduces overall CO2 emissions. Furthermore, the payback period is short; therefore the system is both reliable and highly efficient.

Analysis of Environmental Benefits

Through the application of the system, high temperature flue gas is reduced to the low temperature. It can successfully reduce waste heat and thermal pollution. At the same time, we can see that CO2 emission reduction is 10.38× 104t/year.

Analysis of Social Benefits

Energy conservation and emission reduction is a project that aims to benefit the ecological environment and protect the health of individuals.

Once the energy conservation and emission reduction projects completed, energy will be conserved whilst also reducing the volume of pollutants that affect the surrounding water and atmospheric environment.

The waste heat utilization system for the forging

furnaces’ flue gas is feasible

High temperature waste heat in flue gas may be used

to produce refrigeration/cooling, steam and hot

water

The waste heat utilisation system creates substantial

economic, environmental and social benefits.

Conclusions

Thank You!