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Weak acid, strong effect Carbon dioxide neutralises alkaline wastewater in an environmentally friendly and cost-effective way.
Weak acid,strong effectCarbon dioxide neutralises alkalinewastewater in an environmentallyfriendly and cost-effective way.
Alkaline wastewater is generated in a wide rangeof industrial plants. As a rule, it is produced bypurification operations or through the use ofalkalis in production. Even process-related con-tact with raw materials or residues can signif-icantly increase the pH value of the wastewater.
In order to protect sewer systems and sewagetreatment plants against damage and failure dueto alkaline wastewater, European Unionlegislation stipulates that relevant quantities haveto be neutralised prior to discharge. Here carbondioxide and know-how from Messer ensure op-timum results.
Carbon dioxide – first choice for neutralisationTraditionally, mineral acids such as hydrochloricacid and sulphuric acid have been used as neu-tralising agents. But the requirement for envi-ronmentally compatible, safe and cost-effectivemethods means that neutralisation with carbondioxide (CO2) is becoming increasingly important.
An important advantage of carbon dioxide overmineral acids is its characteristic flat neutralisa-tion curve. Dissolved in water, carbon dioxide
acts as a bivalent, weak acid. This means that itseffect is dependent on the pH value. There istherefore no possibility of over-acidification,which is frequently the case when mineral acidsare used. And there is also no need for an elab-orate control system.
Since carbon dioxide is an inert gas, corrosion ofsurrounding hardware, associated withhydrochloric and sulphuric acid, does not occur.
Another advantage is that there is no need forinvestments for acid storage or for safetyhardware typical with mineral acids.
Neutralisation with carbon dioxide does notincrease the salt load of the waste waterwith chloride, sulphate, phosphate or nitrate.As well as being advantageous in environmentalterms, this can also have a positive impact ondischarge permits or load-based wastewaterdischarge fees.
Carbon dioxide is also superior to mineral acidswhen comparing the consumption figures.
The neutralisation of alkaline wastewater, as atthis biological treatment plant, is a necessaryprocess in many industries.
Wastewater neutralisation – relevant to many industries
Neutralisation with liquid carbon dioxide requires minimal space.
Carbon dioxide consumption compared with mineral acid
Schematic representation of the neutralisation curves ofsodium hydroxide solution when using carbon dioxide andmineral acid
Phase 1
Permitted range
Carbon dioxide consumption
Phase 2 Phase 3
CO2 H2SO4
96 % (w/w)HCI
37 % (w/w)
Mineral acid
Many industry sectors therefore use carbon di-oxide not only to neutralise wastewater, but alsoto adjust the pH of process water. A solution thatis of interest to, for example, pulp and papermanufacturers, steelworks, swimming pools andlaundries.
Practical implementation with MesserThe first step in wastewater neutralisation withcarbon dioxide is to select a suitable location. Onmany customers’ premises, existing plant compo-nents can be used, such as a wastewater pipe-line, a small basin or a pump sump.
For each project, the wastewater properties aswell as the on-site conditions are checked inorder to be able to propose the optimal tech-nology in each case. Messer supplies the ap-propriate hardware for metering and injection,chosen from a large portfolio of technologies.Generally, the plant components are verycompact. For example, larger quantities aredosed in liquid form, which is particularlyeconomical in terms of energy use.
Naturally, Messer also ensures that your carbondioxide requirements are fully met.
Carbon dioxide plus know-howMesser’s qualified scientists, engineers andtechnicians have accumulated a wealth of ex-perience in the neutralisation of many differenttypes of wastewater. Their know-how ensuresthat the carbon dioxide is used to best effect.
We offer a tailor-made package – consisting ofengineering, hardware and supply – that meetsevery requirement. A large number of referenceplants, with capacities ranging from just a fewgrams to 2000 kg of carbon dioxide per hour, arealready using know-how and gases from Messer.
Your advantages at a glance:
Over-acidification practically impossible•No handling of hazardous, aggressive acids•No corrosion problems•No increase in the salt load of wastewater•No investment costs for acid storage•Low operating costs•Minimal space and staff requirements•
Wastewater neutralisation with carbondioxide is also advantageous for smallerfactories like this dairy.
Easy adjustmentof the pH
Diagram of the neutralisation process
pH-regulation
Carbon dioxide-storage tank
Injection of liquid carbon dioxide
Neutra-Box
Finding the best solution togetherYou too can benefit from our experience in theneutralisation of alkaline wastewater. Ourapplications engineers will provide you withadvice tailored to your specific requirements:
Foodstuffs industry•Beverage industry and dairies•Chemical and pharmaceutical industry•Construction industry•Natural stone and concrete processing•Steel production to metal chemistry•Power plants•Drinking water production•Waste management and recycling•Glass production•Pulp and paper industry•Textile and leather industry•Laundries•and many more•
If you have any questions, please do not hesitateto contact us.
Dr. Monica Hermans,Technology Management Chemistry/EnvironmentE-mail: [email protected]
This and many other brochures can also bedownloaded from the Internet as a PDF file:www.messergroup.com
Messer Group GmbHGahlingspfad 31
47803 KrefeldTel. +49 2151 7811-0
Fax +49 2151 [email protected]
www.messergroup.com
