RBConsult

Waste Heat Recovery Systems

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Waste heat loss comes from inefficient systems, thermodynamic limitations of equipment and processes. This waste heat is released into the atmosphere through stacks, valves and mechanical equipment, unless it is captured and "recycled". This process of recovering waste heat and using it to fulfill a desired purpose elsewhere is called "waste heat recovery" (WHRS).

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A waste heat recovery installation offers the following advantages:

• Lower operating costs because it reduces energy costs on the grid

• Increased power reliability: By supplying critical parts of the plant using waste heat, interrupting power to the grid will not affect production.

• Mitigating the impact of future electricity rate increases.

• (Indirect) reduction of CO2 emissions by offsetting the amount of electricity purchased.

• Reduction of pollution thanks to an additional dust removal mechanism.

• Reduction of plant-specific energy consumption, reducing greenhouse gas emissions (based on a credit for reducing the power plant's electricity production or reducing the production of captive electricity from fossil fuels at the cement plant)

 

In the cement manufacturing industry, WHRS technology  is capable of generating a significant share of electricity needs using waste heat. WHRS is a mature technology, with more than 850 WHRS installations worldwide.

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When designing a WHRS installation, the following design principles should be considered:

• WHRS power plants  must not influence the normal operation of the clinker production line, including efficiency, quality and energy consumption.

• Existing equipment installations and waste heat are fully used as much as possible.

• Waste heat from the cooler at the outlet of the kiln and from the preheater of the cement production line will be used. An extraction duct is designed in the middle part of the cooler.

• Primary reverse osmosis water purification technology will provide additional water treatment for boilers and good water management.

• A mechanical cooling tower with a steel and concrete structure is installed for the water circulation system.

• A thermal de-aerator is installed for the supply of water during deoxidation with non-adjustable steam.

 

RBConsult proposes the engineering services in two phases for the implementation of a waste heat recovery system :

a. Preliminary basic engineering study

b. Elaboration of specifications for a call for tenders

 

Phase a.

• Validation of tenders or studies subsequently received or prepared

• Evaluate the functional aspect of the kiln line(s) including the flow rate and temperature of the stack and excess air of the cooler

• Selecting the type of recovery system

• Preliminary sizing based on operational data provided by the Client

• Proposal for the implementation of the system

• Establishment of basic specifications

• Report of phase a.

 

Phase b.

• Validation of the basic engineering of phase a

• Preparation of documents forming part of the tender documents such as:

  • Sizing criterion

  • Equipment Specifications

  • Implementation plan

  • Installation plan

  • Flow sheets

  • Electrical diagrams

  • Origin of equipment and list of subcontractors

• Launch of the call for tenders

• Clarification meetings with suppliers or general contracting companies,

• Evaluation of tenders received from tenderers

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