ORGANIC RANKINE CYCLE POWER PLANT
FOR WASTE HEAT RECOVERY
Keywords: Organic Rankine Cycle, Waste Heat Recovery, Cement Industry, Gas Compression
Station
ABSTRACT
Power Plants based on the Organic Rankine Cycle (ORC) have been increasingly employed over the last 20
years to produce power from various heat sources when other alternatives were either technically not practical
or not economical. These power plants in sizes from 300 kW to 130 MW have demonstrated the maturity of this
technology. The cycle is well adapted to low moderate temperature heat sources such as waste heat from
industrial plants and is widely used producing 600 MW of electric power from geothermal and waste heat
resources. The ORC technology is applicable to heat recovery of medium size gas turbines and cement plants,
and o ers significant advantages over conventional steam bottoming cycles. One such system, the 6.5 MW Gold
Creek Power Plant is now in operation at a gas compressor station in Canada displacing some 25,000 tons of
CO2 yearly. The Gold Creek Power Plant is owned and operted by a subsidiary of Transcanada Pipeline. A
second system of 1.5 MW is operating at the Heidelberger Zement AG Plant in Lengurt, Germany. These
environmentally friendly power plants are the first to be installed in these industries. The Cement power plant is
recovering unused grate cooler heat and is generating electricity on a continuosly basis without interfering with
the initial clinker production process, displacing some 7000 t of CO2 yearly. The use of ORC technology based
systems has matured to a field proven and highly reliable technology. ORC have demonstrated advantages over
conventional steam cycles and are particularly applicable to geothermal power plants and the recovery of waste
heat, from small to medium gas turbines such as the compressor stations, while providing cost and
environmental advantages.
1. INTRODUCTION
A. Lengfurt Cement Power Plant
The ORMAT heat recovery system at the Heidelberger Zement AG Plant in Lengfurt is the first of such
systems supplied to the cement industry. (Figure 1) This environmentally friendly plant recovers the unused
grate cooler heat and generates 1,300 kW of electricity on a continuous basis, amounting to over 10% of the
cement plant's internal electricity use, without interfering with the initial clinker production process. The waste
heat recovery power plant will result in the saving of 7,000 tons of CO2 annually.
Even for an optimized cement process, significant heat loss, mainly caused by the heat of the waste gases, still
occurs. The heat balance of a kiln plant reveals that preheater waste gases and cooler exhaust air account for
more than 30% of that heat loss.
Waste heat sources may be directly used for drying of raw material, coal or intergrinding matter. However, there
are numerous cement plants where this utilization is either not possible or not required and this unused heat is
lost. The economic order of magnitude of such losses in a typical kiln line of 2000 t/d capacity with a 4-stage
cyclone preheater and grate cooler, is as follows: Assuming a preheater waste-gas temperature of 350°C and grate cooler exhaust-air temperature of 275°C,
approximately 1,100 kJ/kg (clinker) of unused heat is lost. When firing coal of a net calorific value of 23,000
kJ/kg, the annual loss to be attributed to unused process heat is approximately US $1.0 – $1.6 million; a very
significant expense for lost energy.
The preferred approach to overcome this economically unsatisfactory situation is to use the waste heat for the
generation of electrical power. In the past some cement plant operators have installed waste heat steam boilers
in their plants and have utilized the process heat to operate a steam turbine generator set. However, the
conventional steam technology has certain implicit drawbacks with respect to the cement production process. In
particular, the use of the relatively low temperature grate-cooler exhaust air, available at continuously varying
temperatures, ranging from 170°C to 300°C, involves difficulties with respect to stable steam turbine operation
due to the high moisture content in the turbine exhaust and pinch point interference problems in the boiler. To
overcome this drawback, exhaust air temperatures have been raised, in some cases beyond the level required for
clinker burning, through additional fuel gas firing. This has increased the fuel consumption in the plant to
unacceptable levels.
ads: ebay
FOR WASTE HEAT RECOVERY
Keywords: Organic Rankine Cycle, Waste Heat Recovery, Cement Industry, Gas Compression
Station
ABSTRACT
Power Plants based on the Organic Rankine Cycle (ORC) have been increasingly employed over the last 20
years to produce power from various heat sources when other alternatives were either technically not practical
or not economical. These power plants in sizes from 300 kW to 130 MW have demonstrated the maturity of this
technology. The cycle is well adapted to low moderate temperature heat sources such as waste heat from
industrial plants and is widely used producing 600 MW of electric power from geothermal and waste heat
resources. The ORC technology is applicable to heat recovery of medium size gas turbines and cement plants,
and o ers significant advantages over conventional steam bottoming cycles. One such system, the 6.5 MW Gold
Creek Power Plant is now in operation at a gas compressor station in Canada displacing some 25,000 tons of
CO2 yearly. The Gold Creek Power Plant is owned and operted by a subsidiary of Transcanada Pipeline. A
second system of 1.5 MW is operating at the Heidelberger Zement AG Plant in Lengurt, Germany. These
environmentally friendly power plants are the first to be installed in these industries. The Cement power plant is
recovering unused grate cooler heat and is generating electricity on a continuosly basis without interfering with
the initial clinker production process, displacing some 7000 t of CO2 yearly. The use of ORC technology based
systems has matured to a field proven and highly reliable technology. ORC have demonstrated advantages over
conventional steam cycles and are particularly applicable to geothermal power plants and the recovery of waste
heat, from small to medium gas turbines such as the compressor stations, while providing cost and
environmental advantages.
1. INTRODUCTION
A. Lengfurt Cement Power Plant
The ORMAT heat recovery system at the Heidelberger Zement AG Plant in Lengfurt is the first of such
systems supplied to the cement industry. (Figure 1) This environmentally friendly plant recovers the unused
grate cooler heat and generates 1,300 kW of electricity on a continuous basis, amounting to over 10% of the
cement plant's internal electricity use, without interfering with the initial clinker production process. The waste
heat recovery power plant will result in the saving of 7,000 tons of CO2 annually.
Even for an optimized cement process, significant heat loss, mainly caused by the heat of the waste gases, still
occurs. The heat balance of a kiln plant reveals that preheater waste gases and cooler exhaust air account for
more than 30% of that heat loss.
Waste heat sources may be directly used for drying of raw material, coal or intergrinding matter. However, there
are numerous cement plants where this utilization is either not possible or not required and this unused heat is
lost. The economic order of magnitude of such losses in a typical kiln line of 2000 t/d capacity with a 4-stage
cyclone preheater and grate cooler, is as follows: Assuming a preheater waste-gas temperature of 350°C and grate cooler exhaust-air temperature of 275°C,
approximately 1,100 kJ/kg (clinker) of unused heat is lost. When firing coal of a net calorific value of 23,000
kJ/kg, the annual loss to be attributed to unused process heat is approximately US $1.0 – $1.6 million; a very
significant expense for lost energy.
The preferred approach to overcome this economically unsatisfactory situation is to use the waste heat for the
generation of electrical power. In the past some cement plant operators have installed waste heat steam boilers
in their plants and have utilized the process heat to operate a steam turbine generator set. However, the
conventional steam technology has certain implicit drawbacks with respect to the cement production process. In
particular, the use of the relatively low temperature grate-cooler exhaust air, available at continuously varying
temperatures, ranging from 170°C to 300°C, involves difficulties with respect to stable steam turbine operation
due to the high moisture content in the turbine exhaust and pinch point interference problems in the boiler. To
overcome this drawback, exhaust air temperatures have been raised, in some cases beyond the level required for
clinker burning, through additional fuel gas firing. This has increased the fuel consumption in the plant to
unacceptable levels.
ads: ebay
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