Stepped recycle method for residual heat of fuel gas

Abstract

A stepped recycle method for residual heat of fuel gas adopts two heat transfer methods (an indirect gas-water heat exchange method and a direct gas-water heat exchange method) which are connected in series to recycle low-grade heat energy in flue gas of a fuel gas in a stepped manner, so as to continuously rise the temperature of heated water; and heated water, of which the temperature is increased twice continuously to 60 to 100 DEG C, serve as steam boiler replenishing water, waste heat boiler replenishing water, water used in other processes or domestic hot water. The system can be widely applied to fuel gas thermotechnical equipment, only consumes a little high-grade electric energy, can effectively recycle low-grade heat energy in the flue gas, has an efficiency improved by 8 to 13 percent, imroves fuel utilization efficiency, realizes energy conservation and emission reduction, and absorbs smoke, NOX and other pollutants of discharged flue gas with condensed water generated during the condensing process of the flue gas, so as to reduce the concentrations of smoke and NOX in the discharged flue gas and further reduce environmental pollution.

Description

Technical field [0001] The invention relates to a method for recycling waste heat, in particular to a method for cascaded recycling of waste heat from gas flue gas, and belongs to the field of thermal engineering. Background technique [0002] With the adjustment of my country's industrial structure and changes in energy demand, the proportion of clean energy utilization is increasing. As a clean energy, natural gas has great application potential in my country. At present, thermal equipment such as gas-fired direct-fired engines, gas-fired boilers, gas turbines, and waste heat boilers widely used in China are reducing smoke, NO X play an important role in protecting the environment. With the completion and commissioning of a number of natural gas pipeline networks such as my country's West-to-East Gas Pipeline and Sichuan-to-East Gas Pipeline, as well as the successive completion and commissioning of multiple imported LNG terminals, domestic natural gas consumption has sh...

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Problems solved by technology

[0010] The above three patents only adopt one method of air-water direct heat exchange or air-water indirect heat exchange to recover the waste heat of flue gas, and realize the recovery and utilization of low-grade heat energy by consuming a certain amount of high-grade electric energy, and the generated temperature is not high. For domestic hot water at 60 degrees Celsius, the cost performance of waste heat recovery is not high

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