Constraints Review
Feedstock:
0.32 MM tons/year Natural gas form the gas treatment plant
2.7 MM tons/year of Fe2O3, which will be shipped in by rail from the Minnesota
iron mines.
Conversion technology description:
The Midrex reformer takes in natural gas and coverts it into H2 and CO. It is
considered a dry reformer. No steam is directly input to the reformer, instead the
recycled CO2 from the top gas of the shaft furnace is the driving force in the
reformation. All of the required H2O comes from the recycled top gas as well and a
reverse water gas shift reaction that occurs at high temperatures. The water is
required in order to maintain the catalyst.
Separation technology:
MDEA is used to remove the CO2 from the stream that is going to be sent to the
combustion chamber of the reformer. It is a amine solvent that is a popular choice
for removal of CO2 from process gases.
A Guard bed is in place to remove any sulfur that is in the incoming natural gas, as
that would ruin our catalyst. The guard bed is zinc oxide.
Product description:
The DRI we create is a high purity iron, about 95% pure. It is desired by steel
makers because of its consistent chemical and physical properties which allow them
flexibility when choosing which furnace charge to use. It also can be used to
produce higher quality steel then lower purity iron. DRI is also low in residual
metals and nitrogen, as well as highly metallic.
Location sensitivity analysis:
The location for this plant is Wiliston ND. This location is ideal for this Midrex style
plant. The large amount of available natural gas provides the necessary reformer
and combustion input required to create the gas used to reduce the Fe2O3. The
location is also feasible to obtain the required Fe2O3 feed from Minnesota by rail as
well as ship the finished DRI product via rail or boat to the steel mills in Indiana.
ESH law compliance:
This plant has utilized all possible energy recovery and environmentally friendly
opportunities in its design. Low NOx emissions,CO2 capture mitigate the impact of
this plant on the environment. In the design of this process pollutants were not only
minimized, but in many cases eliminated. According to “Emission factors of
nitrogen oxides and carbon monoxides from natural gas combustion” from the EPA,
our 140 lb/MM SCF of NOx has an emissions factor rating of an A.
Law of physics compliance:
There is 2.7 MM tons/year of Fe2O3 feed being sent to the shaft furnace with 1.84
MM tons/year of DRI exiting the shaft furnace. The remaining 0.86 MM tons/year of
mass is the oxygen that is removed from the Fe2O3, which leaves the shaft furnace
in the top gas.
Turndown ratio:
We estimate that the turndown ratio for our plant is around 50%. On the other
hand, these plants are usually ran at about 120% of their designed capacity.