Catalytic NOx Reduction System Using Trace Hydrogen Injection

This page updated November 23, 2005.

Makel Engineering, Inc.

Catalytic NOx Reduction System Using Trace Hydrogen Injection

CARB Grant Number ICAT 00-2

The statements and conclusions in this Report are those of the grantee and not necessarily those of the California Air Resources Board. The mention of commercial products, their source, or their use in connection with material reported herein is not to be construed as actual or implied endorsement of such products.

Project Summary
Makel Engineering Inc. (MEI) conducted pilot demonstration program under a grant from the California Air Resources Board (ARB) to develop a practical, low cost NOx emissions reduction system Suitable for lean burn natural gas fuel stationary power generators. This program directly supported the objectives of the ARBís Comprehensive Work Plan. In particular, this project supported the strategy in the 1994 State Implementation Plan (SIP) for achieving lower NOx emissions. The overall objectives of this project where:
  • Build a prototype NOx emissions reduction system.

  • Perform design optimization tests.

  • Complete a field test demonstration.
The resulting NOx emissions reduction system consists of a hydrogen production source, injection system, catalytic converter, sensors and control system. Laboratory tests were conducted at MEI and University of California at Berkeley (UCB). Once the design was completed optimization testing was conducted, and system refinements where made and the laboratory scale hardware was scaled up to be suitable for use on 100 to 250 kW class engines. Finally, a field test demonstration was commenced and performance data was gathered on a 100kw genset running in the field.
The resulting product addresses the need for effective NOx reduction systems for lean burn combustion devices. The initial target market for this technology is lean burn, natural gas powered reciprocating engines (stationary power generators). However, this technology may ultimately be adapted to diesel power generators and potentially to heavy-duty vehicles (CIDI engines) in conjunction with new particulate control systems and/or clean burning fuels currently under development.
In the presence of excess oxygen, conventional catalytic converters have very low NOx conversion rates. To address this limitation of existing technology, MEIís research represents an effective NOx reduction systems for lean burn combustion devices. The MicroNOx Trace Hydrogen Injection NOx reduction system is an exhaust after treatment system that is intended to be a system that can be used with existing natural gas or propane fueled lean burn engines without any modification to the engine control system. This system is applicable to both the retrofit and OEM engine / gen-set market. The system consists of a set of catalytic converters that are in parallel with each other and used in a cyclic fashion. The converters consist of NOx storage catalyst stages upstream of conventional three-way catalytic converter. The converters are used to store NOx and are then regenerated with a hydrogen / carbon monoxide product stream from an external microchannel based reformer. System control is achieved using a NOx sensor downstream of the converters. With proper sizing of the NOx storage catalysts, the required fuel flow for regeneration of the catalyst is less than 0.5% of the total fuel flow to the engine.
This research culminated in a field-test of a 100 kW natural gas generator configured with a MicroNOx exhaust system. Specifications for the system is provided in Table 1.

Table 1. MicroNOx System Operating Specifications

Fuel Type

Natural Gas or Propane

Exhaust Inlet Temperature

350 C min

Maximum Inlet Temperature

TBD (estimated less than 550 C)

NOx Reduction

Greater than 80%

Fuel Consumption

Approximately 0.5%

Inlet Power

24 VDC

Power Consumption

12 W

The field test site was the Butte Community College water pumping system site demonstrates the technologyís ability to utilize trace hydrogen to improve the NOx reduction efficiency of catalytic cleanup of NOx emissions. The Butte College water pumping station relies on an aerobic digester system and a series of evaporation ponds. The field test generator replaces the 175kw diesel generator and operated offline through a switching system. The BCC waste treatment plant is based on a digester system. Raw sewage is pumped into a pumping well and run through two 5 hp sewage grinders. Two 7.5 hp lift pumps feed the sewage into an aerobic digester. Two 25 hp blower aerate the sewage in the digester system. These blowers and pumps run continuously alternating between electric motors. The processed sewage is released into a gravity flow system, pouring into a series of holding ponds where it evaporates.
Testing with the final version of the system developed on this program demonstrated a NOx reduction of over 80% with up to 5% oxygen in the engine exhaust. The system was successfully operated over a nine-month field test with numerous starts as the system was typically used for sporadic short periods (typically a few hours).

Funding Source

Funding Amount





UC Berkely

$  49,600

Lubrizol Corporation

$  50,400

Click here for the entire final report.

ICAT Funded Projects