From aa3bf7984c9dbce9f29202617c867baf2a12dd70 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ole=20Petter=20L=C3=B8d=C3=B8en?= <opl@equinor.com>
Date: Tue, 5 May 2026 15:54:51 +0200
Subject: [PATCH 1/3] fix(process): scale mass rate when LiquidRemover drops
 out liquid phase

---
 .../process/process_units/liquid_remover.py     | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/src/libecalc/process/process_units/liquid_remover.py b/src/libecalc/process/process_units/liquid_remover.py
index f75a5ddf8d..28c9acd784 100644
--- a/src/libecalc/process/process_units/liquid_remover.py
+++ b/src/libecalc/process/process_units/liquid_remover.py
@@ -16,7 +16,14 @@ def get_id(self) -> ProcessUnitId:
 
     def propagate_stream(self, inlet_stream: FluidStream) -> FluidStream:
         """
-        Removes liquid from the fluid stream.
+        Removes liquid from the fluid stream. The new stream's mass rate is scaled
+        down by the gas mass fraction so the dropped-out liquid isn't re-injected
+        into the gas phase.
+
+        The removed liquid (mass = inlet.mass_rate * (1 - gas_mass_fraction),
+        composition = inlet - new_fluid) is currently discarded. It could later
+        be exposed as a separate outlet stream — e.g. routed to an oil pump,
+        accounted for in emissions, or reported back to the user.
 
         Args:
             inlet_stream: The fluid stream to be scrubbed.
@@ -26,6 +33,12 @@ def propagate_stream(self, inlet_stream: FluidStream) -> FluidStream:
         """
         if inlet_stream.vapor_fraction_molar < ThermodynamicConstants.PURE_VAPOR_THRESHOLD:
             new_fluid = self._fluid_service.remove_liquid(inlet_stream.fluid)
-            return inlet_stream.with_new_fluid(new_fluid)
+            inlet_molar_mass = inlet_stream.fluid.molar_mass
+            if inlet_molar_mass > 0.0:
+                gas_mass_fraction = inlet_stream.vapor_fraction_molar * new_fluid.molar_mass / inlet_molar_mass
+            else:
+                gas_mass_fraction = 1.0
+            new_mass_rate = inlet_stream.mass_rate_kg_per_h * gas_mass_fraction
+            return inlet_stream.with_new_fluid(new_fluid).with_mass_rate(new_mass_rate)
         else:
             return inlet_stream

From 6248fabdf13c5842e9b6db3555b424d946ee07bb Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ole=20Petter=20L=C3=B8d=C3=B8en?= <opl@equinor.com>
Date: Thu, 7 May 2026 15:11:29 +0200
Subject: [PATCH 2/3] test(process): assert LiquidRemover scales mass rate by
 gas mass fraction

---
 .../process_units/test_liquid_remover.py      | 33 +++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/tests/libecalc/process/process_units/test_liquid_remover.py b/tests/libecalc/process/process_units/test_liquid_remover.py
index 3d433c0e69..62f5bfdab7 100644
--- a/tests/libecalc/process/process_units/test_liquid_remover.py
+++ b/tests/libecalc/process/process_units/test_liquid_remover.py
@@ -33,3 +33,36 @@ def test_liquid_remover_removes_liquid(fluid_service, liquid_remover_factory):
 
     assert inlet_stream.vapor_fraction_molar < 1.0
     assert outlet_stream.vapor_fraction_molar == 1.0
+
+    expected_gas_mass_fraction = (
+        inlet_stream.vapor_fraction_molar * outlet_stream.fluid.molar_mass / inlet_stream.fluid.molar_mass
+    )
+    expected_mass_rate = inlet_stream.mass_rate_kg_per_h * expected_gas_mass_fraction
+    assert outlet_stream.mass_rate_kg_per_h < inlet_stream.mass_rate_kg_per_h
+    assert outlet_stream.mass_rate_kg_per_h == expected_mass_rate
+
+
+def test_liquid_remover_passthrough_when_no_liquid(fluid_service, liquid_remover_factory):
+    composition = FluidComposition(
+        nitrogen=3,
+        CO2=1,
+        methane=80,
+        ethane=10,
+        propane=6,
+    )
+    fluid_model = FluidModel(eos_model=EoSModel.SRK, composition=composition)
+    fluid = fluid_service.create_fluid(
+        fluid_model=fluid_model,
+        pressure_bara=STANDARD_PRESSURE_BARA,
+        temperature_kelvin=STANDARD_TEMPERATURE_KELVIN,
+    )
+    inlet_stream = FluidStream.from_standard_rate(
+        standard_rate_m3_per_day=100000,
+        fluid_model=fluid.fluid_model,
+        fluid_properties=fluid.properties,
+    )
+    remover = liquid_remover_factory()
+    outlet_stream = remover.propagate_stream(inlet_stream)
+
+    assert inlet_stream.vapor_fraction_molar == 1.0
+    assert outlet_stream.mass_rate_kg_per_h == inlet_stream.mass_rate_kg_per_h

From 419f6618fad33da033c94524de80a69dec46026b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ole=20Petter=20L=C3=B8d=C3=B8en?= <opl@equinor.com>
Date: Thu, 7 May 2026 15:14:42 +0200
Subject: [PATCH 3/3] docs: changelog entry for LiquidRemover mass-rate fix

---
 docs/drafts/next.draft.md | 1 +
 1 file changed, 1 insertion(+)

diff --git a/docs/drafts/next.draft.md b/docs/drafts/next.draft.md
index 88ef8ad32b..4c526bf154 100644
--- a/docs/drafts/next.draft.md
+++ b/docs/drafts/next.draft.md
@@ -14,6 +14,7 @@ STP: "flare" column has been added to STP Export - for `FIXED` installations onl
 ## Bug Fixes
 
 - Hardened compressor PH flash handling so invalid thermodynamic states are no longer used in compressor outlet calculations.
+- `LiquidRemover` now scales the outlet mass rate by the gas mass fraction when liquid is dropped, so the removed liquid mass is no longer carried by the gas stream downstream.
 
 ## Breaking changes