The event was hosted by The Southern Company from Monday, June 24, 2019, to Thursday, June 27, 2019. This seminar was held at the Sheraton Birmingham Hotel, located at 2101 Richard Arrington Jr. Blvd. North, Birmingham, AL 35203. The topics covered included a wide range of emissions issues and AQCS technologies on Particulate Matter, FGD (Dry & Wet Scrubbers), SCR and other power plant operations and maintenance issues. K&A as an industry expert participated in a number of sessions providing Voice of Customer (VOC) and market intelligence on a range of topics related to the US Power Industry. K&A also briefly discussed a recent AQCS market survey findings from the cement industry.

Market Survey Findings from the Cement Industry

K&A discussed a recent (2019) example of a cement plant subject to the NSPS standards where they added a new preheater/precalciner cement kiln with a rated throughput of 7716 tons of clinker per day at an existing facility. The kiln system consists of a 15-stage preheater, calciner and rotary kiln. Emissions are controlled by the Kiln Baghouse, low NOx burners, SNCR, and an activated carbon system. The kiln uses natural gas, coal, coke, fuel oils and/or non-hazardous fuels (chips and tires, whole tires, engineered fuels, dried bio-solids, high-carbon fly ash) and other biomass fuels

NOx Emission Limit: 1.50 pounds per ton of clinker, 30-day average. This limit is to be met by staged combustion, low-NOx burners and SNCR

Regarding dioxins/furans, the BACT consists of water spray injection into a gas conditioning tower.

SCR Requirement at US Cement Plants

K&A also opined that in some rare circumstances, if a unit is subject to NSPS and happens to be in a severely ozone nonattainment areas, plant have considered SCR and ACI as the BACT on a case by case basis. The USA has roughly 120 cement plants with kilns, there is only one cement plant in Illinois, a LaFarge plant that has an SCR.

Role of PAC and Mercury Control

K&A conducted a recent cement market survey where we spoke to many experts and some AEs who design the PAC and SNCR for cement plants, who said the answer was dependent on the size of the unit, the production rate, the quality and composition of the marl feedstock, mercury contained in the marl (which can vary tremendously), current baseline, amount of reductions required, etc. The variance can be quite a bit depending on whether you are sizing for a 500-600 tons/per day plant to a 3,000 ton/day plant:

The frequency of bag filter changes can be 2-3 years and is usually staged by compartment
About 70% of the cement plants have SNCR for NOx removal. They mostly use Aqueous Ammonia, and their feed rate can vary from 3 gallons/minute to sometimes 8 gallons/minute - 5 gallons/minute is a good rule of thumb for 30-40% NOx Reduction and can vary based on the design of the calciner, pre-heater etc.
The utilization of PAC can vary from 200-500 pounds/hr to 1 ton/hr depending on the size of the plant, operating hours, what they are trying to achieve, production rate, reduction required, feedstock quality etc. One of the feedback we got from a leading expert was :-

“The cement plant vary tremendously based on the raw material (for example there are cement plants, mercury content in the marl can vary between 10 parts per billion to 1000 parts per billion), assuming in some cases limestone can account for 85% of the rock, mercury concentration plays a key role in the compliance strategy. There is no universal system to say if one injects 500 pounds/hr., we are going to get a reduction of X as it is very plant specific as there are different arrangements with the kilns, baghouses and the feedstock source.” The cement plant’s compliance is impacted by NESHAP and in some cases CISWI.

For more information on this topic email us at info@krishnaninc.com to schedule a quick online discussion