2008 Spring Symposium

 
Andy Walk­er
HDD Glob­al Tech­nol­o­gy Direc­tor
John­son Matthey
Wayne, PA

Abstract — The role and require­ments of Diesel emis­sion con­trol sys­tems have changed­sub­stan­tial­ly since the intro­duc­tion of the ear­ly Diesel Oxi­da­tion Cat­a­lysts (DOC) tocon­trol car­bon monox­ide (CO) and hydro­car­bon (HC) emis­sions from light duty Die­selve­hi­cles. Since then, emis­sions leg­is­la­tion has tight­ened sig­nif­i­cant­ly around the world,driving the devel­op­ment and imple­men­ta­tion of com­plex sys­tems to con­trol emis­sions ofPar­tic­u­late Mat­ter (PM) and nitro­gen oxides (NOx), as well as CO and HC. This­p­re­sen­ta­tion pro­vides an overview of the sys­tems cur­rent­ly being used to meet today∍sDiesel leg­is­la­tion, and looks ahead to the cat­a­lyst sys­tems that will be used to meet­fu­ture, incom­ing reg­u­la­tions.

An overview will be giv­en of the require­ments and capa­bil­i­ties of the cur­rent­DOC plus Diesel Par­tic­u­late Fil­ter (DPF) sys­tems being used to con­trol CO, HC and PMe­mis­sions with very high effi­cien­cy. The chal­lenges that these sys­tems face, and the­ways in which these chal­lenges have been over­come will be out­lined. The futuredi­rec­tion of this tech­nol­o­gy will be dis­cussed.

Some of the main chal­lenges cur­rent­ly fac­ing the catalyst/engine com­mu­ni­tyre­late to the con­trol of NOx emis­sions from Diesel engines. Reduc­ing NOx (to nitrogen)under the high­ly oxi­diz­ing con­di­tions preva­lent in the Diesel exhaust is extreme­ly­chal­leng­ing, but two approach­es have already been suc­cess­ful­ly intro­duced into largescale series pro­duc­tion.

NOx Adsor­ber Cat­a­lysts (NAC) oper­ate by stor­ing NOx under oxi­diz­ing­con­di­tions, and then reduc­ing this NOx dur­ing the peri­od­ic, short-term reduc­ing eventscre­at­ed by run­ning the engine under fuel-rich con­di­tions. An overview of the oper­at­ing­prin­ci­ples, capa­bil­i­ties and future chal­lenges in the NAC area will be giv­en.

Selec­tive Cat­alyt­ic Reduc­tion (SCR) sys­tems oper­ate by using ammo­nia to react­s­e­lec­tive­ly with the NOx under oxi­diz­ing con­di­tions. SCR sys­tems are already in use onheavy duty Diesel vehi­cles in Europe, and are start­ing to be intro­duced into the NorthAmer­i­can mar­ket. The per­for­mance capa­bil­i­ties and future chal­lenges fac­ing SCR­cat­a­lyst tech­nol­o­gy will be dis­cussed. Some alter­na­tive NOx con­trol approach­es are alsobe­ing con­sid­ered, and a brief overview of the most promis­ing will be giv­en.

The increas­ing­ly strin­gent leg­is­la­tion requires simul­ta­ne­ous very high con­ver­sion­sof all four reg­u­lat­ed pol­lu­tants. This can be achieved by com­bin­ing DPF and NOx­con­trol sys­tems. The con­fig­u­ra­tions being used to pro­vide the nec­es­sary emis­sion­scon­trol are pre­sent­ed, and the future direc­tion of Diesel emis­sion con­trol will be dis­cussed.

Speaker’s Biog­ra­phy — Dr. Walk­er is Heavy Duty diesel Glob­al Tech­nol­o­gy Direc­tor at John­son Matthey, Emis­sion Con­trol Tech­nolo­gies. He is lead­ing the devel­op­ment of JM prod­ucts for the glob­al on-road and non-road HDD mar­kets.