Pekka Oinas Chem Waste Min

Waste minimization 4.4.2006 P. Oinas 1(4) ------------------------------------------------------------------------------------------------------------------------

Waste minimization in chemical industry Special features of fine chemicals' manufacture, recycling of solvents and waste treatment 1 General Waste minimization is now an established feature of chemical, with respect to both improved process economics and compliance with stringent environmental and safety limits. These strategies typically aim at: -

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achieving remarkable reductions in aqueous and atmospheric waste emissions, in order to ease the load on existing treatment facilities and minimizing the need for external waste treatment facilities maximizing the recycling ratio of every possible waste or solvent stream for raw material saving and process yield enhancement understanding the nature of wastes

The reactor or set of reactors is considered as the core of the process, yielding in product spectrum which then dictates the nature and capacity required for downstream processing. These steps consist of: - separation of product streams from waste or solvent streams - separation and recycle of unreacted feed streams - purification of waste and solvent streams - waste destruction processes The reactor outlet stream contains the saleable speciality component itself, unconverted feed constituents, reacted by-products and solvents that may both be saleable or waste. Thus, in addition to the reactor and reaction, the separation processes downstream dictate the quality of the final product and have also a major impact on the economy of the process. Actually, the ‘product’ of the batch process is preferably quality than yield or capacity. No matter what the capacity of the process is, the saleable product must fulfil the requirements of specification. In fine chemicals industries and especially in pharmaceutical processes, the quality issue has become increasingly rigorous during the past decade. The operation of the ‘core’ reactor must be modified to minimize waste formation. In some organic processes, the molar yield of a multi-step synthesis process can be as low as 30% or even lower. This means that the rest of primary raw materials that do not produce the desired product are either waste or by-product that must be treated or recovered. Since the by-products plausibly react further in each of the steps and consume raw materials and require solvents as well, the obvious focus for process development of existing fine chemical processes is the increase of stepwise yields. Further, as the products are often isolated as solid from dilute suspensions, the goal of process development must be the increase of concentration of the process. These two targets may, however, be competing: concentrated solutions may generate more by-products in reaction processes and the purity of isolated solid product may be deteriorated.

-----------------------------------------------------------------------------------------------------------------------University of Oulu, Department of Process and Environmental Engineering Waste minimization and resources use optimization course, 3.-7.4. 2006

Waste minimization 4.4.2006 P. Oinas 2(4) -----------------------------------------------------------------------------------------------------------------------2 Implementation of a process to an existing production line (retrofit design) The first thing in design is to choose the equipment appropriate for the process. Generally, some pieces of new equipment are required as well. After this preliminary and basic choice, the mass balance of the process over all the units defined is calculated. Based on the mass balance, the new process implementation is designed in more detail. The mass balance is utilized when the processing capacity, raw material consumption and waste generation are appraised. The need for new equipment and piping is evaluated. The investment cost calculation follows. In the following, a cost estimate for quotation for the manufacture of an agrichemical E is presented. The total amount of the planned contract is 600 tons. This amount should be manufactured within three years. The batch size estimated is 2400 kg technical material (not 100% pure) and the bottlenecking step cycle time is 25 h. The first case describes the estimate when the recovery processes for solvents has not been designed and realized. The latter case involves a bigger investment for these recovery facilities. We can see that the impact of recycling is crucial both for the economy of the process and the total cost structure. This is the win-win –situation for both parties of the agreement.

-----------------------------------------------------------------------------------------------------------------------University of Oulu, Department of Process and Environmental Engineering Waste minimization and resources use optimization course, 3.-7.4. 2006

Waste minimization 4.4.2006 P. Oinas 3(4) -----------------------------------------------------------------------------------------------------------------------COST ESTIMATE FOR THE PRODUCTION OF AGRICHEMICAL E Production need

600 200

ton E ton E/year

Batch size Cycle time Capacity

2400 25 70,0

kg E h ton E/month

Raw materials and solvents R1 R2 S1 S2

Campaign time Production time Washing Solvent runs Total time

Unit ratio kg/kg E 1 2 1,5 3

Profit

Cost €/kg E 4 2 0,75 4,5 11,25

months 2,9 0,25 0,25 3,4

Cost estimate for production Raw materials and solvents Wastes Production cost Investment Profit Total cost Business potentia

Cost €/kg 4 1 0,5 1,5 Total

Basic case

16,48 5,49 5,40 1,80

€/kg E 11,25 5,25 0,7 1,25 9,0 27,5

Unit ratio kg/kg E W1 (organic) 3 W2 (aqueous) 15 Wastes

Cost €/kg 0,5 0,25

Cost €/kg E 1,5 3,75

Total

5,25

Production line cost

50000 0,7

€/month €/kg E

(including labour, utilities)

Investment

750000 1,25

€ €/kg E

for three years

% 41,0 19,1 2,6 4,6 32,8

M€ M€/year M€ M€/year

Fig. 1. Cost estimate for the manufacture of agrichemical E with limited recyling possibility.

-----------------------------------------------------------------------------------------------------------------------University of Oulu, Department of Process and Environmental Engineering Waste minimization and resources use optimization course, 3.-7.4. 2006

Waste minimization 4.4.2006 P. Oinas 4(4) -----------------------------------------------------------------------------------------------------------------------COST ESTIMATE FOR THE PRODUCTION OF AGRICHEMICAL E Production need

600 200

ton E ton E/year

Batch size Cycle time Capacity

2400 25 70,0

kg E h ton E/month

Unit ratio kg/kg E 1 2 1,5 0,5

Cost €/kg 4 1 0,5 0,75 Total

Raw materials and solvents R1 R2 S1 S2

Campaign time Production time Washing Solvent runs Total time

Profit

Cost €/kg E 4 2 0,75 0,375 7,125

months 2,9 0,25 0,25 3,4

Cost estimate for production Raw materials and solvents Wastes Production cost Investment Profit Total cost Business potentia

Solvent recycle case

13,58 4,53 6,60 2,20

Unit ratio kg/kg E 0,5 W1 (organic) 7,5 W2 (aqueous)

Wastes

Production line cost Investment

€/kg E 7,13 2,13 0,71 1,67 11,00 22,63

50000 0,7

Cost €/kg 0,5 0,25

Cost €/kg E 0,25 1,875

Total

2,125

€/month €/kg E

1000000 € 1,67 €/kg E

(including labour, utilities) for three years

% 31,5 9,4 3,2 7,4 48,6

M€ M€/year M€ M€/year

Fig. 2. Cost estimate for the manufacture of agrichemical E with extended recyling possibility.

__________________________________________________________________________ References: Reilly, A.J., (2002). Trans. IChemE 80, Part A, 587.

-----------------------------------------------------------------------------------------------------------------------University of Oulu, Department of Process and Environmental Engineering Waste minimization and resources use optimization course, 3.-7.4. 2006