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An integrated system that dynamically maintains the hydrogen content or fuel utilization during solid oxide fuel cell operation irrespective of the higher hydrocarbon content fluctuations in natural gas feed

IP.com Disclosure Number: IPCOM000242931D
Publication Date: 2015-Aug-31
Document File: 8 page(s) / 52K

Publishing Venue

The IP.com Prior Art Database

Related People

Mohamed Sharif: INVENTOR [+6]

Abstract

The disclosure describes an integrated system consisting of an online gas analyzer closely coupled with the fuel cell system employing a two-step mathematical algorithm that maintains the hydrogen content or the fuel utilization of a solid oxide fuel cell or stack irrespective of the fluctuations in higher hydrocarbons in the natural gas feed. This system is designed to take online gas analyzer composition data and dynamically control the natural gas flow to maintain the fuel utilization of an operating solid oxide fuel cell.

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An integrated system that dynamically maintains the Hydrogen content or Fuel utilization during solid oxide fuel cell operation irrespective of the higher hydrocarbon content fluctuations in natural gas feed

BRIEF ABSTRACT

The disclosure describes an integrated system consisting of an online gas analyzer closely coupled with the fuel cell system employing a two-step mathematical algorithm that maintains the hydrogen content or the fuel utilization of a solid oxide fuel cell or stack irrespective of the fluctuations in higher hydrocarbons in the natural gas feed. This system is designed to take online gas analyzer composition data and dynamically control the natural gas flow to maintain the fuel utilization of an operating solid oxide fuel cell.

KEYWORDS

            Hydrogen content, fuel utilization, fuel cell voltage, hydrocarbon, hydrocarbon content, higher hydrocarbon, solid oxide fuel cell, natural gas flow, mass flow controller, gas correction factor

DESCRIPTION OF INNOVATION

A)   Effect of higher hydrocarbon in fuel cell processing and fuel cell reaction / Problem statement

Natural gas is a hydrocarbon gas mixture consisting primarily of methane, but commonly includes varying amounts of other higher hydrocarbons as impurity. The level of higher hydrocarbon impurity in the natural gas supply varies with geographical location of natural gas production, purifying process efficiency, and calculated mixing of higher hydrocarbon during peak usage, also known as peak-shaving times. Solid oxide fuel cells mainly use methane in natural gas as a fuel that is converted later to hydrogen by steam methane reformation. The amount of hydrogen produced is critical to determine the available fuel for electrochemical reaction. The amount of hydrogen supplied and power withdrawn from the fuel cell is correlated by the factor “fuel utilization”.

An event of increased amount of higher hydrocarbon content such as ethane, propane, butane and pentane in natural gas affects this available fuel, thereby affecting a solid oxide fuel cell’s fuel utilization. This increased amount of higher hydrocarbon affects the fuel utilization in two ways.

1.    Reduces total natural gas flow by affecting gas correction factors of mass flow controllers

A standalone solid oxide fuel cell system generally uses mass flow controllers (“MFCs”) calibrated with nitrogen to control the mass flow of natural gas. The gas correction factor provided to mass flow controller is 0.72, assuming the natural gas is complete methane. In an event of higher hydrocarbon content increase in natural gas, for e.g.: (methane = 92%, ethane = 5%, propane = 2%, butane = 0.5%, pentane = 0.2%) the gas correction factor 0.72 acts against the higher hydrocarbons and reduces the total flow. For example: The mass flow fraction of 2 slm of ethane flowing through the methane calibrated MFC will result in = 2 x (0.5/0.72) = 1.38 slm. This effect happens to all fractions of higher hydrocarbon with re...