Blending Control for Low Heating Value Fuel Gas
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Solution Overview
Problem
The production of steel generates large quantities of blast furnace gas with a lower heating value, making it unsuitable for use in gas turbines, while coke oven gas has a higher heating value but is available in smaller quantities, rendering both by-product gases unsuitable for fueling combustion-driven equipment without proper blending.
Innovation Solution
A fuel system for gas turbines employs a feedforward/feedback control strategy to blend blast furnace gas and coke oven gas, using process inputs and target heating values to predict and correct the coke oven gas flow rate, ensuring the blended fuel gas meets minimum and maximum acceptable heating value thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If blast furnace gas is used as fuel gas, then the quantity of fuel gas available is large, but the heating value is too low for gas turbine operation
Solution Approach 1:
The system combines blast furnace gas (high quantity, low heating value) with coke oven gas (low quantity, high heating value) in a blending system to produce a mixed fuel gas that meets gas turbine requirements. The controller regulates the mixing ratio to achieve the desired heating value while utilizing the abundant blast furnace gas supply.
2Use of energy by moving object
If coke oven gas is used as fuel gas, then the heating value is high, but the quantity available is small
Solution Approach 1:
The system merges coke oven gas (high heating value, limited quantity) with blast furnace gas (low heating value, abundant quantity) in controlled proportions. The controller adjusts the blending ratio to maximize the utilization of available coke oven gas while supplementing it with blast furnace gas to meet the total fuel gas demand of the turbine.
3Adaptability or versatility
If the heating value of blended fuel gas varies, then different by-product gases can be utilized, but combustion instability and blowout may occur
Solution Approach 1:
The controller continuously monitors the heating value of the blended fuel gas and adjusts the mixing ratio of blast furnace gas and coke oven gas in real-time to maintain the heating value within acceptable limits. This feedback control prevents combustion instability and blowout while allowing flexibility in utilizing different by-product gas compositions.
Data Source
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AI summary
A method includes blending a first fuel (84) with a second fuel (76) in a ratio to produce a third mixed fuel (66). The first fuel (84) has a first heating value, the second fuel (76) has a second heating value, and the third mixed fuel (66) has a third heating value. In addition, the first heating value is different than the second heating value. The method also includes feedforward controlling the third heating value of the third mixed fuel (66) via prediction and correction of a fuel flow rate of the first and/or second fuels (84, 76) to adjust the ratio of the first and second fuels (84, 76) based at least in part on a comparison between a measurement and a target for the third heating value.