# US 2023/0264993 A1 · Method and system for comminuting and cleaning waste plastic > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2023/0264993 A1 - Document ID: US20230264993A1 - Status: Published application - Kind: A1 - Application number: 18/165,878 - Filed: 2023-02-07 - Published: 2023-08-24 - Earliest claimed: 2022-02-21 - Assignees: Krones AG - Applicants: Krones AG - Inventors: Michael RUSS; Franz BAUR; Michael AUBURGER; Jochen FORSTHOEVEL; Simon FISCHER - Web page: https://patentgrep.com/patent/US20230264993A1 ## CPC - B29B 17/02: Separating plastics from other materials - C02F 3/06: using submerged filters - B09B 3/35: Shredding, crushing or cutting - B29B 17/04: Disintegrating plastics, {e.g. by milling}(B29B9/02, B29B11/02, B29B13/10, {B29B17/02} take precedence) - B29B 2017/0289: {Washing the materials in liquids} - B29B 2017/0468: {Crushing, i.e. disintegrating into small particles} - C02F 2101/30: Organic compounds - C02F 2103/38: Polymers - C02F 2209/08: Chemical Oxygen Demand [COD]; Biological Oxygen Demand [BOD] - C02F 2303/24: Separation of coarse particles, e.g. by using sieves or screens - Y02W 30/62: Plastics recycling; Rubber recycling - B29B: PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS - C02F: TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE (separation in general B01D; special arrangements on waterborne vessels of installations for treating water, waste water or sewage, e.g. for producing fresh water, B63J; adding materials to water to prevent corrosion C23F; treating radioactively-contaminated liquids G21F9/04; regeneration of reactants for recirculation into processes, see the relevant places for the processes) - B09B: DISPOSAL OF SOLID WASTE NOT OTHERWISE PROVIDED FOR - Y02W: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT ## Abstract A method and a system for comminuting and cleaning waste plastic are described. For this purpose, waste plastic is comminuted and pre-washed in a wet mill and then cleaned in a washing system. The resulting wastewater is subjected to mechanical filtration and flotation and then temporarily stored as circulating water. Based on this, some of the circulating water is returned to the wet mill as first process water and some of the circulating water is returned to the washing system as second process water. In this way, the first and second portions of the circulating water may be specifically adapted to the respective water requirements of the wet mill and the washing system as well as to the required water qualities, if necessary with selective post-cleaning of the second portion of the circulating water. As a result, the fresh water requirement for the process described may be minimized. ## Claims ### Claim 1 Method for comminuting and cleaning waste plastic, wherein the latter is comminuted and pre-washed in a wet mill and then cleaned in a washing system, wherein wastewater is subjected to mechanical filtration and flotation and then temporarily stored as circulating water, and a first portion of the circulating water is then fed back to the wet mill as first process water and a second portion of the circulating water is fed back to the washing system as second process water. ### Claim 2 (depends on 1) Method according to claim 1, wherein the second portion of the circulating water is post-cleaned by a combination of biodegradation and membrane filtration or by electrocoagulation. ### Claim 3 (depends on 2) Method according to claim 2, wherein the second portion of the circulating water is further post-cleaned by reverse osmosis to a quality suitable for food processing. ### Claim 4 (depends on 1) Method according to claim 1, wherein the first portion of the circulating water is adjusted to at least twice the quantity of the second portion. ### Claim 5 (depends on 1) Method according to claim 1, wherein external fresh water is further supplied to the washing system and a ratio of the supplied second process water and the external fresh water is set to at least 1. ### Claim 6 (depends on 1) Method according to claim 1, wherein a chemical oxygen demand (COD) in the second portion of the circulating water is reduced by the post-cleaning compared to the first portion of the circulating water by at least half. ### Claim 7 (depends on 1) Method according to claim 1, wherein cutting/grinding tools and the waste plastic comminuted therewith are exposed to the first process water in the wet mill, the latter thereby takes up a proportion of a contaminant load present on the waste plastic. ### Claim 8 (depends on 1) Method according to claim 1, wherein the circulating water, which has been mechanically cleaned by filtration and flotation and decantation, is treated proportionally chemically and/or enzymatically, thereby breaking down minute particles of plastic contained in the circulating water, and is discharged as waste water. ### Claim 9 System for comminuting and cleaning waste plastic, comprising: a wet mill for comminuting and pre-washing the waste plastic; a washing system, for subsequent resource-preserving cleaning of the comminuted waste plastic; a mechanical filtration stage and a flotation stage for treating wastewater from the wet mill and the washing system to form circulating water; a buffer tank for intermediate storage of circulation water; and in each case connected thereto: a first circulation circuit for returning a first portion of the circulating water to the wet mill for use there as first process water, and a second circulation circuit for returning a second portion of the circulating water to the washing system for use there as second process water. ### Claim 10 (depends on 9) System according to claim 9, wherein the second circulation circuit comprises a one of a membrane bioreactor and an electrocoagulation stage and further comprises a respective downstream reverse osmosis stage. ### Claim 11 (depends on 9) System according to claim 9, wherein circulation circuits are connected to the buffer tank and configured to convey the circulating water so as to enable setting its first portion to be at least twice as large as its second portion. ### Claim 12 (depends on 10) System according to claim 10, wherein the membrane bioreactor comprises an aerobic biodegradation stage and a separate ultrafiltration stage. ### Claim 13 (depends on 9) System according to claim 9, wherein the mechanical filtration stage comprises a sand separator and a fine screen and/or is connected upstream of a tank for filtered wastewater. ### Claim 14 (depends on 9) System according to claim 9, further comprising a rainwater tank for collecting and admixing rainwater to the wastewater and/or circulating water. ### Claim 15 (depends on 9) System according to claim 9, wherein the washing system comprises at least three cleaning stages for pre-cleaning, main cleaning and post-cleaning, as well as an internal process water circuit for passing the second process water therein through the cleaning stages in counter-current to the comminuted waste plastic. ### Claim 16 (depends on 9) System according to claim 9, wherein the wet mill comprises a grinding chamber with cutting tools for comminuting the waste plastic with admixture of the first process water and a pre-washing stage for pre-washing the comminuted waste plastic with the first process water in order to take up a contaminant load of the waste plastic in the first process water and then to discharge the first process water as waste water. ### Claim 17 (depends on 9) System according to claim 9, further comprising a wastewater cleaning stage for chemical and/or enzymatic degradation of minute particles of plastic contained in the circulating water and for proportionally discharging circulating water thus cleaned as wastewater that is separated from the second portion of the circulating water. ### Claim 18 (depends on 1) Method according to claim 1, wherein cleaning in the washing system includes in a multistage resource-preserving washing system. ### Claim 19 (depends on 7) Method according to claim 7, wherein the latter thereby takes up a main proportion of the contaminant load present on the waste plastic, and is then fed completely as waste water to mechanical filtration and flotation. ### Claim 20 (depends on 17) System according to claim 17 wherein the separating is by additional membrane filtration, electrocoagulation and/or reverse osmosis.