EP-4741822-A2 - EMISSION APPARATUSES FOR SENSOR CROSS-SENSITIVITY TO AMMONIA AND ASSOCIATED SYSTEMS AND METHODS

EP4741822A2EP 4741822 A2EP4741822 A2EP 4741822A2EP-4741822-A2

Abstract

Provided are embodiments for a sensor apparatus for measuring emissions, including: an extraction member (104) in fluid communication with the exhaust gas flow (114), the extraction member (104) having an inlet end (122) and an outlet end (124), the inlet end (122) receiving an exhaust gas sample from the exhaust gas flow (114); an ammonia capture media (110) positioned downstream of the inlet end (122) within the extraction member (104), the ammonia capture media (110) comprising a sorbent configured to remove ammonia from the exhaust gas sample; and a post-capture sensor (106b) positioned downstream of the ammonia capture media (110), the post-capture sensor (106b) configured to measure at least one downstream NOx concentration measurement in the exhaust gas sample of the exhaust gas flow (114). Further provided are associated systems and methods for measuring emissions.

Inventors

STELZER, ROBERT M
Puthuparampil, Jobin
Pong, Henry Ho Yin
Ostaltsov, Andrey

Assignees

Safety Power Inc.

Dates

Publication Date: 20260513
Application Date: 20251106

Claims (17)

A sensor apparatus for measuring emissions, the apparatus comprising: - an extraction member in fluid communication with the exhaust gas flow, the extraction member having an inlet end and an outlet end, the inlet end receiving an exhaust gas sample from the exhaust gas flow; - an ammonia capture media positioned downstream of the inlet end within the extraction member, the ammonia capture media comprising a sorbent configured to remove ammonia from the exhaust gas sample; - a post-capture sensor positioned downstream of the ammonia capture media, the post-capture sensor configured to measure at least one downstream NO x concentration measurement in the exhaust gas sample of the exhaust gas flow; and - wherein the post-capture sensor are cross-sensitive to ammonia.
The apparatus of claim 1 further comprising: - an pre-capture sensor positioned between the inlet end and the ammonia capture media and configured to measure at least one upstream NO x concentration measurement in the exhaust gas sample; and - a collector assembly connected to the inlet end, the collector assembly comprising at least two sample inlets in communication with the exhaust gas flow, a first sample inlet in the at least two sample inlets receiving a first portion of the exhaust gas sample at a first location of the exhaust gas flow and a second sample inlet in the at least two sample inlets receiving a second portion of the exhaust gas sample at a second location of the exhaust gas flow.
The apparatus of any one of claims 1 to 2, further comprising an eductor or a pump configured to increase a flow rate of the exhaust gas sample.
The apparatus of any one of claims 1 to 3, wherein the at least one downstream NOx concentration measurement and the at least one upstream NO x concentration measurement comprise at least one selected from the group of: nitric oxide and nitrogen dioxide, the at least one downstream NO x concentration measurement and the at least one upstream NO x concentration measurement further comprise at least one selected from the group of: nitric acid, nitrous acid, dinitrogen pentoxide, peroxyacetyl nitrate, alkyl nitrates, peroxyakyl bitrates, nitrate radical, and peroxynitric acid.
The apparatus of any one of claims 1 to 4, wherein the ammonia capture media further comprises: - a removable sorbent housing in communication with the exhaust gas; - wherein the sorbent is positioned within the removable sorbent housing .
The apparatus of any one of claims 1 to 5, wherein the sorbent is one of phosphoric acid or a condenser.
The apparatus of claim 1, wherein the pre-capture sensor, the post-capture sensor, and the ammonia capture housing are heated to an operating temperature by an external heat source, optionally the exhaust gas sample.
A method for reducing emissions in an exhaust gas flow, the method comprising: - extracting, from the exhaust gas flow into an inlet of an extraction member, a first exhaust gas sample; - reducing, using an ammonia capture media within the extraction member, a gaseous ammonia concentration in the first exhaust gas sample; - measuring, at a post-capture sensor positioned downstream from the ammonia capture media, at least one downstream NO x concentration measurement of the first exhaust gas sample; - receiving, at a processor, the at least one downstream NO x measurement; - determining, at the processor, an aggregate NO x concentration measurement based on the at least one downstream NOx concentration measurement; - transmitting, from the processor to an ammonia producing means positioned in the exhaust gas flow, a control signal based on the aggregate NOx concentration measurement; and - wherein the post-capture sensor are cross-sensitive to ammonia.
The method of claim 8 further comprising: - measuring, at an pre-capture sensor positioned between the inlet of the extraction member and the ammonia capture media, at least one upstream NO x concentration measurement of the first exhaust gas sample; - receiving, at the processor, the at least one upstream NO x measurement; - wherein the aggregate NO x concentration measurement is determined based on the at least one downstream NO x concentration measurement and the at least one upstream NO x concentration measurement.
The method of claim 9, wherein the at least one downstream NO x concentration measurement and the at least one upstream NO x concentration measurement comprise at least one selected from the group of: nitric oxide and nitrogen dioxide, the at least one downstream NO x concentration measurement and the at least one upstream NO x concentration measurement comprise at least one selected from the group of: nitric oxide, nitrogen dioxide, nitric acid, nitrous acid, dinitrogen pentoxide, peroxyacetyl nitrate, alkyl nitrates, peroxyakyl bitrates, nitrate radical, and peroxynitric acid.
The method of claim 10, further comprising: - storing in a memory at least one selected from the group of: the aggregate NO x concentration measurement, the at least one upstream NO x concentration measurement and the at least one downstream NO x concentration measurement; - determining an ammonia concentration based at least one selected from the group of: the aggregate NO x concentration measurement, the at least one upstream NO x concentration measurement and the at least one downstream NO x concentration measurement; and - sending a control signal to a pump receiving the first exhaust gas sample.
The method of claim 11, further comprising: - determining, at the processor, a state of the ammonia capture media; - transmitting, from the processor to a network device, the state of the ammonia capture media to a network device; and - determining the control signal for the ammonia producing means based on the aggregate NOx concentration measurement and the state of the ammonia capture media.
The method of claim 12, further comprising: - a pre-capture sensor external heat source and a post-capture sensor external heat source; - wherein the processor is configured to send a control signal to the first sensor external heat source and post-capture sensor external heat source.
The method of claim 8, further comprising: - receiving a signal from a secondary sensor positioned in a second exhaust gas sample; responsive to the signal from the secondary sensor, sending a signal to an isolation device upstream from the ammonia capture media, the signal to the isolation device permitting the first exhaust gas sample to flow.
A system for reducing emissions in an exhaust gas flow, the system comprising: - an ammonia capture media in an extraction member, an inlet end of the extraction member in fluid communication with the exhaust gas flow and receiving a first exhaust gas sample from the exhaust gas flow, the ammonia capture media for reducing gaseous ammonia in the first exhaust gas sample; - a post-capture sensor positioned downstream of the ammonia capture media, the post-capture sensor configured to measure at least one downstream NO x concentration measurement of the first exhaust gas sample; - a processor in communication with the post-capture sensor and an ammonia generation means the processor configured to perform the method of any one of claims 8 to 14; - wherein at least one of the pre-capture sensor and the post-capture sensor are cross-sensitive to ammonia.
The system of claim 15 further comprising: - an isolation device upstream from the ammonia capture media controlling the first exhaust gas sample; - a secondary sensor positioned in a second exhaust gas sample; and - wherein the processor is further configured to: - receive a signal from the secondary sensor; and - responsive to the signal from the secondary sensor, send a signal to the isolation device to permit the first exhaust gas sample to flow.
The system of claim 15 further comprising: - a secondary sensor positioned in a second exhaust gas sample; and - wherein the processor is further configured to: - receive a signal from the secondary sensor; and - responsive to the signal from the secondary sensor, send a signal to the pump or eductor to permit the first exhaust gas sample to flow.

Description

FIELD The present embodiments relate generally to emission sensing for combustion devices such as boilers, generators and internal combustion engines. More specifically, the present embodiments are directed to an emission apparatus for improving the operation of emissions sensors where such sensors are cross-sensitive to ammonia. BACKGROUND Exhaust gas emission control has become particularly important due to stringent regulatory emission limits on boilers, generators and reciprocating engines. A typical exhaust gas after-treatment system may comprise many different individual emission reduction functions in order to meet the regulatory emission standards. More specifically, the selective catalytic reduction (SCR) device is frequently used in the exhaust system of combustion devices to eliminate particles of nitrogen oxides (NOx) in the exhaust gas. The SCR device is normally located in the exhaust system downstream of the combustion that takes place in a boiler, generator or reciprocating engine. The SCR device contains a SCR catalyst to reduce NOx, particles in the exhaust gas as the SCR catalyst must be heated before it can be used to reduce NOx, particles. In other words, until the SCR catalyst reaches an activation temperature, which is the minimum temperature to which the SCR catalyst must be heated, the SCR catalyst does not provide NOx, emission reduction. Although the hot exhaust gas from the combustion in a boiler, generator or reciprocating engine heats up the SCR Catalyst, for certain applications the length of time required to heat up the SCR Catalyst using hot exhaust gas alone can be too long. SCR technology relies on a chemical reaction, which occurs between 260-540°C (500-1000F) to reduce NOx, particles in the exhaust gas. This commonly includes the use of gaseous ammonia provided by urea solution (i.e. CH4N2O or CO(NH2)2). Injecting gaseous ammonia is important because it is used as a reactant for reducing the NOx emissions at the SCR. The most common emission reduction reaction in the SCR of several NOx variants is 4NO + 4NH3 + O2 → 4N2 + 6H2O. Nitrogen oxides (NOx) emission sensor devices are used to measure the NOx emission concentrations within the exhaust gas flow in order to provide measurement data for the operation of the emissions system. This can include measurements for controlling the injection of liquid urea or liquid ammonia solution to generate gaseous ammonia to permit the emission control reaction at the SCR device. These sensors however, are commonly cross-sensitive to gaseous ammonia and therefore face challenges with providing accurate measurement data. Cross-sensitivity refers to a phenomenon that occurs when a gas other than the gas being monitored causes the gas sensor to show a reading, even when the target gas is not present. This cross-sensitive property can interfere with the accuracy of the sensor and thus prevent effective control or fine tuning of an emission control system. The injection of liquid urea or liquid ammonia solution into the exhaust stream also faces a challenge related to so-called "ammonia slip". Ammonia slip refers to the condition wherein unreacted ammonia (NH3), introduced as a reductant into the selective catalytic reduction (SCR) system for the purpose of reducing nitrogen oxides (NOx), passes through the catalyst without participating in the intended chemical reactions and is subsequently emitted in the exhaust stream. Ammonia slip may result from factors such as reductant over-dosing, insufficient catalyst activity, non-uniform reductant distribution, or suboptimal temperature conditions within the catalyst zone. Conventional NOx monitoring sensors address the ammonia/NOx cross-sensitivity problem by adjustment of the measurement of either the NOx or ammonia flow rate upstream of the SCR catalyst and monitoring the resulting downstream sensor reading, sometimes referred to as sensor dithering. The dithering approach is a poor solution since the NOx and/or ammonia concentrations in the exhaust flow would be unbalanced for a period of time during the dithering process, which may lead to issues meeting very stringent NOx emission targets. There is a need therefore for improved emission apparatuses to improve sensor accuracy. SUMMARY It is desirable to have a sensor apparatus for improving the precision of NOx measurements from an exhaust stream where gaseous ammonia is used to reduce the NOx emissions. This includes the fact that the improved precision of measurements would improve the control model for the emission reductions system. Downstream NOx sensor data provides a "feedback" into a control system that operates the emission reduction system, including corrections based on field conditions. The ammonia injection thus can interfere with post-capture sensor readings to cause an "inverse control" problem. The present embodiments provide a solution to the ammonia/NOx cross-sensitivity problem differently by providing a sorbent material to