Hydrocarbon Processing - April 2022 - 35

Process Optimization
check valves to prevent the " flashing " of butane pushing back
against the gasoline in the fill line. An inline static mixer (approximately
$7,000-$8,000) is also required to ensure blend
homogeneity to cut down on circulating the tank [to be determined
by testing the degree of homogeneity achieved with and
without circulation (4 hr, 8 hr, 16 hr), and then interpolating/
extrapolating as needed].
This scheme will produce a pressure drop of approximately
10%, so sufficient pumping capacity must be provided. The
quantity of butane injected is measured with a butane flowmeter
(turbine or Coriolis- type, at a cost of $5,000-$12,000, depending
on type).
A variation of this scheme is to inject butane sequentially
using the same scheme, where the amount of butane injected
is measured with a butane tank gauge (on the bullet). This
saves the cost of a butane flowmeter but prolongs the blending
time, and it can require additional homogenization time
via circulation.
Injection of butane and/or naphtha directly into the
product tank. In this scheme, butane is sequentially injected into
the tank filling line after the gasoline product has been pumped
into the tank. This means that a tank sample can be taken and its
properties analyzed, allowing the determination of the maximum
amount of butane that can be injected without throwing the gasoline
product off spec. A disadvantage is that it takes much longer
to homogenize the tank sample and analyze the tank, calculate
the amount of butane to be injected, physically add the butane,
circulate the tank to ensure homogeneity, sample the tank again,
and ensure it is on spec. This can easily add approximately 24 hr
to the cycle from beginning to end to " final " the product tank.
The scheme (shown in FIG. 2) determines the amount of injected
butane as measured with a butane tank gauge (on the bullet);
if not, a butane flowmeter will be required at additional cost.
Although this scheme uses a high-efficiency vortex nozzle
mixer, it is not as time-efficient as the first scheme mentioned
here with the sparger and static mixer; therefore, additional circulation
time must be allocated before taking tank samples. The
time can be determined experimentally.
GAME-CHANGING CVD COATINGS
FOR RELIABLE PROCESS EQUIPMENT
MAKE YOUR FLOW PATH INERT
Internal
floating roof
*
*
Nozzle with
6-in. jet
Eductor
4 ft
18 in.
30° angle towards
tank wall
FIG. 2. Sequential butane blending.
HC Feb 2022.indd 1
Hydrocarbon Processing | APRIL 2022 35
1/10/2022 3:20:00 PM
*
*
Extends product lifetimes in harsh
environments.
Reduce costs associated wiwth exotic
materials.
Improves process analyzer precision
and reliability.
Ensures emissions monitoring
compliance.
www.SilcoTek.com
+1(814) 353.1778
Inline blending of butane and/or naphtha into the product
tank. This scheme allows for precision blending of the
maximum possible amounts of butane and naphtha to maximize
gross profit per barrel. The price for this is the additional cost
of a skid-mounted inline blender, an online RVP analyzer and
blending software. A typical design is shown in FIG. 3.
The typical cost of the inline blender with three streams
[P/L gasoline, butane and natural gas liquids (NGL)] ranges from
$300,000-$700,000 (~$150,000 per meter run, plus $150,000
for an analyzer, plus blending software). Typical performance is
within the ASTM precision of measurement (r = 0.2 ON, RVP
Gasoline from pipeline
F
x
AC = RVP analyzer/controller
F = Flow sensor/transmitter
FC = Flow controller
RY = Multiplying relay
COA
COC
SPA = RVP set point/target
F
Butane from bullet
Blended gasoline
FIG. 3. Inline blending of butane.
PVW
RY
SPC
= Controller output signal
= Controller output signal
PVC
COC
SPA
AC
RVP
analyzer
FC
COA = PVC/PVw
OPTIMIZE PROCESSING PERFORMANCE WITH
10-in. pipe
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