GB/T 1028-2018Industrial surplus energy resources evaluation methods (English PDF)

2.1 Surplus energy

The usable energy output by an industrial production process system after it has consumed its input energy.

2.2 Surplus energy carrier

A substance that contains surplus energy.

2.3 Quantity of surplus energy

The amount of surplus energy.

2.4 Theoretically available quantity of surplus energy

The quantity of surplus energy possessed by the surplus energy carrier, referred to the standard environmental parameters (temperature 25 °C, pressure 0.1 MPa) and to substances that have completely undergone the oxidation reaction.

2.5 Technically and economically available quantity of surplus energy

The maximum usable quantity of surplus energy determined, after technical and economic assessment, to have economic value for recovery.

2.6 Recovery rate of surplus energy

The ratio of the quantity of surplus energy recovered and used to the theoretically available quantity of surplus energy.

Note: expressed as a percentage.

2.7 Surplus heat

The usable thermal energy output by an industrial production process system after it has consumed its input energy.

2.8 Surplus pressure energy

The usable pressure energy output by an industrial production process system after it has consumed its input energy.

2.9 Surplus chemical energy

The usable chemical energy output by an industrial production process system after it has consumed its input energy.

2.10 Waste cold energy

The energy usable by the system because, after an industrial production process system has consumed its input energy, the temperature of the working medium is lower than the ambient temperature.

2.11 Available potential energy

The maximum capacity of a unit of working medium to do work in a given state.

4.1 Content of the evaluation of industrial surplus energy resources

The evaluation of industrial surplus energy resources shall cover the following five aspects:

a) quantity of surplus energy;

b) energy density;

c) grade;

d) impact of recovery and use on the environment;

e) class of the surplus energy resource.

4.2 Quantity of surplus energy

4.2.1

To calculate the quantity of surplus energy, the boundary shall first be determined. The boundary may be defined by region (province, city, county, industrial park, geographical area of the plant) or by system (process system).

4.2.2

The quantity of surplus energy is divided into the theoretically available quantity of surplus energy and the technically and economically available quantity of surplus energy.

4.2.3

The theoretically available quantity of surplus energy evaluates the entire surplus energy content of the surplus energy carrier; the technically and economically available quantity of surplus energy evaluates the surplus energy that has economic value for recovery under existing technical conditions.

4.2.4

The quantity of surplus energy is generally calculated on an annual basis, using formula (1):

Qy = Sigma (i = 1 to n) mi × |hi1 - hi2| ... (1)

where:

Qy - annual quantity of surplus energy, in kilojoules per year (kJ/a);

mi - annual total quantity of the i-th surplus energy carrier, in kilograms per year or standard cubic metres per year (kg/a or m3/a);

hi1 - specific enthalpy of the i-th surplus energy carrier, in kilojoules per kilogram or kilojoules per standard cubic metre (kJ/kg or kJ/m3);

hi2 - specific enthalpy of the i-th surplus energy carrier after its energy has been recovered and used, in kilojoules per kilogram or kilojoules per standard cubic metre (kJ/kg or kJ/m3).

Note: when calculating the theoretically recoverable quantity of surplus energy, hi2 is the specific enthalpy of the surplus energy carrier at the standard environmental parameters (temperature 25 °C, pressure 0.1 MPa); when calculating the technically and economically available quantity of surplus energy, hi2 is the specific enthalpy of the surplus energy carrier after recovery and use of the surplus energy with a specific technology that has economic value.

4.2.5

The recovery rate of surplus energy is calculated using formula (2):

epsilonr = Qyr / Qyt × 100% ... (2)

where:

epsilonr - recovery rate of surplus energy;

Qyr - annual quantity of surplus energy actually used, in kilojoules per year (kJ/a);

Qyt - annual theoretically available quantity of surplus energy, in kilojoules per year (kJ/a).

4.3 Surplus energy density

4.3.1

Surplus energy density is the energy contained in a unit mass or unit volume of the surplus energy carrier.

4.3.2

The surplus energy density is calculated using formula (3):

q = Qyt / My ... (3)

where:

q - surplus energy density, in kilojoules per kilogram or kilojoules per standard cubic metre (kJ/kg or kJ/m3);

Qyt - annual theoretically available quantity of surplus energy, in kilojoules per year (kJ/a);

My - annual mass or volume of the surplus energy carrier, in kilograms per year or standard cubic metres per year (kg/a or m3/a).

4.4 Grade

4.4.1

The grade of a surplus energy resource is evaluated by its available potential energy, temperature and pressure.

4.4.2

The available potential energy is calculated using formula (4):

e = h - T0 × s ... (4)

where:

e - available potential energy of the surplus energy, in kilojoules per kilogram (kJ/kg);

h - specific enthalpy of the surplus energy carrier (including the absolute value of the standard reaction enthalpy), in kilojoules per kilogram (kJ/kg);

T0 - ambient temperature, in kelvin (K);

s - entropy, in kilojoules per kilogram kelvin [kJ/(kg·K)].

For the thermodynamic properties of common surplus energy carriers used in formula (4), see Annex A and Annex B.

4.4.3

Surplus energy may be evaluated by the available potential energy at the standard environmental parameters (T0 = 25 °C, p0 = 0.1 MPa); the available potential energy e, the enthalpy h and the entropy s of common gases at these parameters can be found in Annex A and Annex B.

4.4.4

Depending on the actual environmental conditions of the project, surplus energy may be evaluated by the available potential energy at the actual environmental parameters; the available potential energy at different environmental parameters is calculated using formula (5):

es = et - est ... (5)

where:

es - available potential energy of the surplus energy at the actual environmental parameters, in kilojoules per kilogram (kJ/kg);

et - available potential energy of the surplus energy at the recommended environmental parameters, in kilojoules per kilogram (kJ/kg);

est - available potential energy, at the standard environmental parameters, of the surplus energy carrier when it is at the actual ambient conditions, in kilojoules per kilogram (kJ/kg).

Example: the available potential energy of air at 600 K at the standard environmental parameters is et = 95.979 6 kJ/kg (from the annex). Assuming an actual environment of 400 K at standard atmospheric pressure, the available potential energy at the standard environmental parameters of the surplus energy carrier at the actual ambient conditions is est = 14.328 0 kJ/kg (from the annex). The available potential energy of the surplus energy in the actual environment is therefore es = et - est = 81.651 6 kJ/kg.

4.5 Impact on the environment

According to the degree to which the discharge of its carrier affects the environment, industrial surplus energy is divided into three categories:

a) discharge exceeding the emission limits: environmental protection measures shall be considered when using the surplus energy;

b) discharge meeting the emission limits: environmental protection measures are recommended to be considered when using the surplus energy;

c) ultra-clean discharge: environmental protection measures need not be considered when using the surplus energy.

4.6 Class of surplus energy resources

4.6.1

Surplus energy resources are divided into classes according to their available potential energy, temperature and pressure.

4.6.2

The classes of surplus energy resources are given in Table 1.

Table 1 - Classes of surplus energy resources (type; class; available potential energy e, kJ/kg; temperature T, °C; pressure p, MPa; recommended recovery technology):

Industrial flue gas, high water vapour content and high temperature: class 1; e > 110; T >= 300; surplus heat power generation.

Industrial flue gas, low water vapour content and high temperature: class 2; e > 80; T >= 300; surplus heat power generation or cascade utilisation for heat supply.

Industrial flue gas, high water vapour content and low temperature: class 3; e >= 30; T < 300; low-boiling-point working medium cycle power generation or heat pump upgrading for heat supply.

Industrial flue gas, low water vapour content and low temperature: class 4; e < 30; T < 300; heat pump upgrading for heat supply.

Steam, higher temperature: class 1; e >= 700; T >= 150; surplus heat power generation or cascade utilisation for heat supply.

Steam, lower temperature: class 2; e < 700; T < 150; heat pump upgrading for heat supply.

Pressurised surplus gas, high gauge pressure and high temperature: class 1; T >= 300; p >= 0.1; surplus pressure power generation or cascade utilisation of temperature and pressure.

Pressurised surplus gas, low gauge pressure and high temperature: class 2; T >= 300; p < 0.1; cascade utilisation for heat supply.

Pressurised surplus gas, high gauge pressure and low temperature: class 3; T < 300; p >= 0.1; surplus pressure power generation or cascade utilisation of pressure.

Pressurised surplus gas, low gauge pressure and low temperature: class 4; T < 300; p < 0.1; heat pump upgrading for heat supply.

Liquid, high gauge pressure and high temperature: class 1; T > 200; p >= 4; surplus heat and surplus pressure power generation.

Liquid, medium gauge pressure and medium temperature: class 2; T 95 to 200; p 1 to 4; cascade utilisation for heat supply.

Liquid, low gauge pressure and low temperature: class 3; T < 95; p < 1; heat pump upgrading for heat supply.

Solid, high temperature: class 1; T > 700; surplus heat power generation.

Solid, medium temperature: class 2; T 400 to 700; surplus heat power generation or cascade utilisation for heat supply.

Solid, low temperature: class 3; T < 400; heat pump upgrading for heat supply.

4.6.3

The choice of surplus energy recovery technology shall take into account the energy density, the grade and the impact on the environment.

4.6.4

Where recovery and use of surplus energy increases or reduces the investment in environmental protection, the investment in surplus energy recovery and use shall be increased or reduced accordingly; environmental benefits obtained from the recovery and use of surplus energy shall be converted and added to the economic value of the surplus energy.

4.7 Comprehensive evaluation of surplus energy

The comprehensive evaluation of surplus energy is given in Table 2.

Table 2 - Comprehensive evaluation table for surplus energy (header: organisational boundary; name of the surplus energy resource; columns: item, unit, value, remarks):

1. Quantity of surplus energy: annual theoretically available quantity of surplus energy, kJ/a; annual technically and economically available quantity of surplus energy, kJ/a.

2. Surplus energy density: mass density, kJ/kg; volume density, kJ/m3.

3. Grade: available potential energy e, kJ/kg; temperature T, °C; pressure p, MPa.

4. Impact on the environment: types of pollutants discharged with the surplus energy - dust, organic waste liquid, sulfides, nitrogen oxides, VOCs, other (tick as applicable); quantity of pollutants discharged with the surplus energy (state type, quantity and unit).

5. Class of surplus energy: gaseous carrier surplus energy - industrial flue gas, class 1, 2, 3 or 4; steam, class 1 or 2; pressurised waste gas, class 1, 2, 3 or 4; liquid carrier surplus energy, class 1, 2 or 3; solid carrier surplus energy, class 1, 2 or 3 (tick as applicable).