Cement Kilns: Difference between revisions

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The production of cement utilizes waste materials in two primary ways, firstly using specific [[Industrial Waste]] and [[Mining & Quarrying Waste]] (and waste from the kiln part of the process itself) as additives and replacement for traditional raw materials, and secondly as a fuel to substitute for the use of traditional fossil fuels in a cement kiln. In 2018 1,414,195 tonnes of waste was used as raw materials and fuel in the production of cement, with just over 43% of kiln thermal input replaced by [[Waste Derived Fuel]]. The five companies manufacturing cement together supplied 78% of the cement consumed in the market in 2018. <ref name=''ref1''>[https://cement.mineralproducts.org/documents/MPA_Cement_SD_Report_2019.pdf MPA Cement Sustainability Report 2019]</ref>

[[Category:Technologies & Solutions]]

[[File:Rotary Cement Kiln105454498 a39b402e4f.jpg|400px|left|Picture of Rotart Cement Kiln: source zkg.de]]

_''TOC''_

==The Process==

There are six main stages of cement manufacture<ref>https://civiltoday.com/civil-engineering-materials/cement/106-cement-manufacturing-process</ref>:

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'''In 1995''' there were 20 'cement factories' in the UK producing around 15 million tonnes a year of cement each year, with the cost of energy in the process representing 40 to 50% of running costs. There was a drive to substitute traditional fuels (coal and petroleum coke) with cheaper fuels slightly before this date, and trials were still running at this time with the ramifications of these trials captured in a Parliamentary Briefing Note<ref>[https://researchbriefings.files.parliament.uk/documents/POST-PN-60/POST-PN-60.pdf Parlimentary Briefing Note 60 April 1995]</ref>. [[Waste Derived Fuel]] had already started to play a more significant role in UK cement processing, in line with other countries (especially in Europe). It started with the use of solvent based hazardous wastes, named by some operators 'Chemfuel', which was being trialed at a substitution of 50% of traditional coal fuel (although at the time 100% substitution occurred in Belgium). At around the same time shredded/chipped waste [[Tyres|tyres]] were starting to also be used in some cement kilns as a [[Waste Derived Fuel]] as both the solvent based wastes and tyres had a high [[CV]] and attracted an income from taking them into a cement kiln. '''By 1998''' the MPA reports that 446,511 tonnes of waste by-products were used as fuel and raw materials, accounting for 4% of cement production and the proportion of fuel comprising waste was 5.7%<ref name = ''ref1''/>.

Cement kilns are an option for disposing of hazardous materials because:

* the temperatures in the kiln, which are much higher than in other combustion systems (e.g. incinerators),

* the alkaline conditions in the kiln, afforded by the high-calcium input mix or rawmix, which can absorb acidic combustion products,

* the ability of the clinker to absorb heavy metals into its structure<ref>[https://en.wikipedia.org/wiki/Cement_kiln Wikipedia Entry]</ref>

'''By 2005''' the range of alternative fuels had expanded in Europe to include [[Tyres|tyres]], [[Plastic|plastic]], [[Paper|paper]], [[Refuse Derived Fuel]], dried [[Sewage Sludge|sewage sludge]], [[MBM|meat and bone meal]] and some other waste streams, with fuel costs typically accounting for 30 to 40% of operating costs<ref>[https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/291569/scho0106bjzn-e-e.pdf Environment Agency Science report on Solid Waste Derived Fuels in Cement Kilns, an International perspective]</ref>. This was driven by the cement industry looking to reduce its costs and carbon emissions, and by changes in the waste sector around the [[Landfill Directive]] and the introduction of the [[Landfill Tax]] which made cement kilns an alternative outlet for suitably prepared waste materials/[[Waste Derived Fuel]].

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==Use of Waste - Current Context==

The UK cement kilns, on the whole, have waste permits and complete returns of the waste handled each quarter. The most recent data for each site is listed in the site specific page per cement kiln, although no returns have been made/are available for [[Cookstown]], [[Purfleet]] and [[Dunbar]]. An analysis of the waste returns for 2018 totals 753,~~783.67~~ tonnes - out of the 1,414,195 tonnes reported by the MPA<ref name = ''ref1''/>. The difference can be accounted for via several factors:

The UK cement kilns, on the whole, have waste permits and complete returns of the waste handled each quarter. The most recent data for each site is listed in the site specific page per cement kiln, although no returns have been made/are available for [[Cookstown]], [[Purfleet]] and [[Dunbar]]. An analysis of the waste returns for 2018 totals 753,784 tonnes - out of the 1,414,195 tonnes reported by the MPA<ref name = ''ref1''/>. The difference can be accounted for via several factors:

* There are no returns for 3 cement kilns

* The material may not be captured by the waste reports <ref> As an example, Blast Furnace Slag is considered a primary input for this type of cement, it is not defined as waste by the producer and therefore is not normally captured in [[UK Waste Tonnage]] figures or waste permit returns</ref>

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From the information that is available, the following breakdown for ~~all plants~~ is ~~available~~:

From the information that is available, the following breakdown for cement kilns is as follows:

{|class="wikitable"

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|[[EWCChap19|19 12 12]]||other wastes (including mixtures of materials) from mechanical treatment of wastes other than those mentioned in 19 12 11||style='text-align:right;'|66,865

|}

In the table above the [[EWC]] code for the waste is shown as well as the description - [[Hazardous Waste]] is signified by entries where the six-digit [[EWC]] code is marked by an asterisk (*). Note that the two codes [[EWCChap19|19 12 10]]([[SRF]]) and [[EWCChap19|19 12 12 (generally [[RDF]], but can be used to describe process fines by some operators) which together account for 318,595 tonnes (or 42% of the tonnage recorded) and comes primarily from the processing of [[Residual Waste]]. The other primary codes used as fuel are [[EWCChap19|19 02 08*]] (the solvent based fuels) and [[EWCChap16|16 01 03]] (waste tyres) which together account for 153,474 tonnes (or 20% of the tonnage recorded) meaning that of the 753,783 tonnes recorded in 2018, 62% were from 4 waste types that all were used as fuel in the cement process.

==List of UK Grinding and Blending Sites==