Cogeneration in industrial power plant

Cogeneration offers enormous potential for not only customers who can conserve energy but also for countries worldwide as they seek to maximise energy and increase efficiency. Cogeneration is defined as the combined simultaneous generation of two forms of useful heat and power (electrical or mechanical) with a common source of fuel, to result in a thermodynamically efficient use of the fuel. Power can be cogenerated in different ways prior to the delivery of thermal energy to a process. Power can also be produced from the recovery of process thermal heat, derived from exothermic process reactions and heat recovery from kilns, process heaters and furnaces.

The basic components of this cogeneration example are a gas turbine and a boiler with multi-fuel burner and forced draft fan system. The gas turbine-generator, having an outlet for providing turbine exhaust gas, is connected to the boiler as well as the back-up forced draft fan. Both systems supply all necessary combustion air under all operating conditions. Critical to this design is the balance between output and performance in both gas turbine and forced draft fan operating modes and requires sophisticated measurements, control and protection to guarantee a smooth switch-over.

Industrial boilers are responsible for most of the production sector’s energy demand, accounting for approximately 70% of their process energy use. These industrial boilers are responsible for supplying saturated and superheated steam as well as hot water to the adjacent production plant and also have to process the fuel gases or liquids released during the production process. The most important variables in this type of boiler systems are the steam and hot water conditions, plus the fuel and environmental constraints. Of equal importance is the type and chemical composition of the fuels to be used and the mandated emissions requirements for the specified plant site.

KROHNE not only supplies single instruments like the OPTISONIC 7300 ultrasonic gas flowmeter for measurement of operational flow or the ALTOSONIC V12 for flow measurement according to custody transfer requirements but also supplies complete fuel skids. The three beam OPTISONIC 3400 ultrasonic heat meter measures the supplied energy in form of hot water and is available with class 1 MI-004 certificate. The OPTISWIRL 4200 is an economic Vortex flowmeter and designed for utility applications and energy distribution monitoring in steam systems. With its integrated pressure and temperature sensor it can measure the steam enthalpy and even detect wet steam. Combined with a temperature sensor in the condensate return it represents an economic solution for energy measurement in steam distribution to allow energy/cost allocation between different parts of the production plant. Furthermore, KROHNE offers complete DP flow measurement solutions and flow computers. Special solutions also available include Venturi tubes, calibrated meter runs with flow nozzles according to ISO 5167 or ASME MFC 3-M, compact orifice assemblies or averaging pitot tubes for simple flow indication purposes. The OPTISONIC 8300 ultrasonic steam flowmeter is best suited for applications that require a big flow turndown or even bi-directional flow: this would be used for metering the steam supply to industrial parks or other plants, with superheated steam.