UPDATE 1-EU deal to close dirty coal plants by end 2023

* Informal deal on acid pollution of large combustion plants

* "Limited lifetime derogation" deadline set at end 2023

* National delays allowed until June 30, 2020

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By Pete Harrison

BRUSSELS, June 17 (Reuters) - Old coal-fired power plants in Europe must be closed by the end of 2023 if their owners are not prepared to fit equipment to filter out acidifying pollutants, following an informal EU deal, officials involved in talks said.

All other power stations must start planning to cut out pollutants such as sulphur and nitrogen oxides that damage human health and soil and water quality, said Holger Krahmer, who represents the European Parliament in the talks.

But countries that are struggling to get the industry cleaned up can get a delay until June 30, 2020, under the informal deal on the Industrial Emissions Directive.

"Compared to the current situation, this offers more clarity and a better chance of a level playing field across Europe on environmental requirements for industrial installations," Krahmer told Reuters.

The compromise is designed to resolve a standoff between the European Union's 27 governments and parliament on the complex directive, which rolls together and updates seven laws on emissions from factories and power plants, including the Large Combustion Plant Directive.

The deal must get formal backing from member states on Friday and later from parliament before it enters force.

The existing laws contain so many opt-outs that many of the 52,000 European installations have managed to avoid cleaning up acidifying pollutants.

The quest for new rules started over two years ago but has been slowed by a row between countries such as Britain and Poland, which have many old coal-fired plants, and others led by Germany that have already invested millions in cleaning up.

The rules, which have gone through several different permutations over the last few months, will have a huge impact on countries energy investments and how much money utilities can make by sweating their coal assets.

Fourteen UK power stations are affected by the new directive, says the Confederation of British Industry. (Reporting by Pete Harrison; editing by William Hardy)