Generator SCR Retrofit at a Guangdong Cement Plant

BOSCH urea dosing and SCR for a 300 kW standby genset

GuangdongShuangma SMKP-300GF300 kW / 540 AUrea SCR

A cement plant keeps its diesel genset for grid maintenance, load-shedding and blackouts. Because it runs so rarely, its emissions are easy to overlook: no EGR, no after-treatment, and when it does pick up load it does so at full output, releasing NOx and smoke in one go. This case covers a urea-SCR retrofit on a 300 kW standby set at a cement plant in Guangdong — the engine and the emergency start-up logic stay as they are, and the NOx gap gets closed.

1. Project overview

Location	A cement plant in Guangdong, China (client name withheld)
Genset	Jiangsu Shuangma SMKP-300GF diesel generating set
Rated power / voltage / current	300 kW / 400·230 V / 540 A
Frequency / speed / power factor	50 Hz / 1500 rpm / 0.8
Engine / alternator	KAIPU KP350 (1-hour rating 365 kW) / SMI-300-4
Genset weight	2250 kg
Condition before retrofit	Years in service with no exhaust after-treatment; visible smoke at start-up and under load; no NOx control

Cement plant standby diesel genset Shuangma SMKP-300GF 300 kW — The 300 kW SMKP-300GF standby set inside the existing power room

Shuangma SMKP-300GF genset nameplate 300 kW 400 V — Genset nameplate: 300 kW, 400/230 V, 1500 rpm, SMI-300-4 alternator

2. The hard part is not the reactor

No NOx control at all. An early non-road configuration without EGR or after-treatment, so raw NOx is high.
Low load factor, low exhaust temperature. The set is idle most of the year and only loads during tests and outages. Low temperature narrows the catalyst window and raises the risk of urea crystallisation.
A tight power room. The reactor has to be sized to the existing room and piping route.
Reliability is the red line. Nothing may compromise emergency start-up or load pickup, and installation can only happen in downtime windows.

The industry context matters too: ultra-low emission retrofits continue across Chinese cement plants, and supervision of on-site diesel machinery and standby power is tightening. A small standby set still shapes how the whole plant looks in an inspection.

3. The solution: urea-injection SCR

With SCR the reactor is rarely the problem; metering and mixing the urea is. Injection pulse width is calibrated against exhaust temperature and flow, a mixing section evens out the atomisation, and the nozzle position follows the casing layout to limit wall films. The reactor is sized by space velocity, the catalyst is selected for the operating temperature band, and insulation is added for low-load duty.

Injection system	BOSCH (Germany), sized for the 300 kW set
NOx sensor	Continental (Germany), real-time feedback for closed-loop correction
SCR reactor	Dinies coating (Germany), 345 mm dia. × 1100 mm (adjusted to site)
Urea tank assembly	1 set
Temperature / pressure sensors	PT100 exhaust temperature, intake temperature and pressure, ambient (optional per site)
Wiring harness	Customised to the power room
Control cabinet (power converter)	Purchased by the customer; AIFILTECH supplies wiring definitions and commissioning support

Control logic: the PT100 exhaust sensor and the intake temperature/pressure sensor feed the controller. Once exhaust temperature enters the catalyst window, urea is dosed against the NOx target; when temperature is too low, dosing stops, which rules out ammonia slip and crystallisation at the source. The NOx sensor closes the loop on dosing quantity.

4. The set and the site survey

KAIPU KP350 diesel engine nameplate 365 kW — Engine nameplate: KAIPU KP350, 1-hour rating 365 kW at 1500 rpm

Standby genset exhaust piping before SCR retrofit — Before retrofit: engine, exhaust routing and power-room layout during the survey

KAIPU KP350 injection pump during site survey — Injection pump and piping, surveyed to fix the dosing and signal points

5. How it was delivered

Site survey: outlet diameter, exhaust temperature profile, available space and piping route.
Custom design: reactor dimensions and nozzle position fixed to site conditions; harness made to the room layout.
Installation in downtime windows: no change to the engine or the emergency start-up logic, clamp-type pipe connection.
Commissioning: pulse width calibrated against temperature and the NOx target, closed loop engaged.
Handover: third-party testing can be arranged to confirm results.

6. Configuration and expected results

NOx reduction. The system is rated at up to 90% under standard conditions; actual results vary with exhaust temperature, load factor and fuel quality, and third-party testing confirms the outcome.
Core components. BOSCH dosing, a Continental NOx sensor and a Dinies-coated reactor, all with established spare-parts channels.
Power reliability. The engine and emergency start-up logic are untouched; installation happens inside downtime windows.
Extensible. A DOC, metal DPF and ASC can be added downstream for combined smoke and CO control.

7. Where it applies

The scheme fits diesel gensets used as standby power where NOx and smoke have to be controlled: cement and building-materials plants, mines, ceramics and glass, data centres, hospitals, airports and ports. AIFILTECH provides sizing, custom design, installation and commissioning.

8. FAQ

A standby unit rarely runs — is SCR really necessary?

Yes. Emissions during test runs and emergency operation are regulated too, and a standby set called into action usually runs at full load, releasing smoke and NOx in a burst. Insulation and temperature-gated dosing keep the SCR effective at low load.

Is the reactor size fixed?

No. 345 mm diameter by 1100 mm length is the baseline; the reactor is adjusted to the actual duct diameter, room space and exhaust temperature profile. Nozzle position and the wiring harness are customised on site.

How is urea crystallisation prevented?

Three measures: pulse width calibrated against temperature and flow with dosing suspended when temperature is low; a mixing section for even atomisation; nozzle position tailored to the casing to avoid wall films.

Will the retrofit affect power generation?

No. The engine and emergency start-up logic are untouched, and the reactor is designed for low backpressure. Work is completed inside downtime windows.

9. Related products and cases

Urea-injection SCR exhaust purifier — the system used here.
DOC + SCR + DPF + ASC purifier — when smoke and CO need treating as well.
Genset emission control — sizing by power and duty.
Jiangmen 1800 kVA retrofit — smoke and CO treated together.

A similar genset to treat? Send us the model, rated power, exhaust outlet diameter and available room space. We will run a sizing check first, then decide whether a site survey is needed.

Bruce Wen · +86 188 1936 6808 (mobile / WhatsApp / WeChat) · bruce.wen@aifiltech.com