Algas-SDI Operations and Maintenance Manual – P/N – 54702
1-1
1.
Introduction
DESCRIPTION
The
BLENDAIRE
is the ALGAS-SDI second generation “parallel pipe” design
Synthetic Natural Gas (SNG) mixer. The
BLENDAIRE
is designed to mix LPG
vapor and air to simulate the combustion characteristics of natural gas. During
operation, the
BLENDAIRE
controls & responds to changes in discharge
pressure due to consumption changes. When operating in a piped network, as
network pressure decreases, the SNG flow rate will increase to maintain
pressure. Alternatively, when the network pressure rises, for example as
consumption is reduced, the SNG flow will decrease. The SNG discharge
pressure is established by the LPG regulator installed upstream of the
BLENDAIRE
. LPG vapor and air flow rates are measured by flow meters. The
ratio of these two flow rates is then compared to the calculated ratio of flow rates
required to achieve a Wobbe value match to the natural gas being simulated.
Adjustment of the ratio is made by adjusting the air flow only. As the flow of SNG
increases or decreases, the Air Flow Control Valve modulates to maintain the
correct and constant mixing ratio between the LPG and air.
There are two separate flow paths into the
BLENDAIRE
, one for air and one for
LPG vapor, (See Figure 1). The air inlet piping contains manual shutoff valve,
check valve, flow conditioner, flow meter, pressure transmitter, and a flow control
valve. A required air regulator installed upstream sets the pressure into flow
control valve. The LPG vapor inlet piping contains manual shutoff valve, check
valve, flow conditioner, flow meter, pressure transmitter, and a safety shutoff
valve. A required LPG vapor regulator upstream sets the mixed gas pressure at
the outlet of the
BLENDAIRE
. The mixed gas line includes a static mixer
section, safety shutoff valve, line pack pressure transmitter, and a manual shutoff
valve (See Figure 2). The line pack pressure transmitter automatically starts the
mixer to an adjustable cut in pressure set point and maintains mixed gas
pressure above this set point until desired line pressure is reached due to
decreased demand.
The
BLENDAIRE
utilizes a state-of-the-art PLC control technology designed by
Algas-SDI to communicate with sensors and actuators and control the mixing
ratio into the single gas line. Adjustments to operating/control parameters are
performed via the Human Machine Interface (HMI).
The
BLENDAIRE
achieves extremely high accuracy and stability in the mixing
process. Equally important, operation of the mixer is very simple. Once set up,
the operation is fully automatic requiring minimum human intervention.
In addition to high accuracy and stability, the
BLENDAIRE
maintains a high level
of safety through the use of automatic safety shut-off valves and closure of the
flow control valve.
