598
E. Fernández et al.
cannot be recovered. On the other hand, polyurethane has better energy efficiency
than the glass wool, but the later can be removed easier than the former, simplifying
thus the process of dismantling. Therefore, glass wool brings more benefits for EoL
of the product than polyurethane foam. We note that way to simplify the dismantling process is to put a nylon layer between the tank and the insulation, to avoid
polyurethane sticking to the tank.
39.4 Hybrid Production-Remanufacturing System
In this section we describe the hybrid production-remanufacturing system proposed
to evaluate the impact of including recovery options for DESWH. Hybrid productionremanufacturing systems refer to production systems in which the demand requirements of an item can be also satisfied by remanufacturing used items returned to the
origin. This hybrid system can be modelled as a Mixed-Integer Linear Programming
(MILP). This MILP consists of an objective function for minimizing the sum of the
costs involved and a set of equations and inequations for establishing the constraints
of the problem, all them composed by linear expressions of certain variables and
parameters. To solve the model and thus determine the optimal values of the variables, it is necessary to provide the values of the problem parameters. In this case it
involves the values of the demand, returns and the costs for both holding inventory
and carry out the production activities. We note that the current production system
of Rivomark does not consider recovery options. Therefore, the values of the parameters related to the returns were estimated based on the analysis of recoverability
of DESWHs presented in Sect. 39.3. The other values required for the model were
estimated along with Rivomark.
39.4.1 Problem Description
We consider the dynamic demand requirements of multiple items (i.e., different
DESWH types) over a finite number of periods, that can be satisfied by producing
new items or by remanufacturing used items returned to the origin. The condition of
the incoming returns is assumed diverse (heterogeneous returns) and an inspection
activity is required to determine their quality. The inspection process is that provided
in Sect. 39.3.1. Through inspection, the returns are graded into a finite number of
nominal quality levels of non-remanufacturable and remanufacturable items (inferior
and superior qualities). Two and five quality levels are considered in this study for
remanufacturable and non-remanufacturable returns, respectively. Remanufactured
and new products are assumed perfect substitutes despite the heterogeneous quality
of the incoming returns, i.e., remanufactured products look as good as new. Unit
costs are incurred for holding inventories of returns as well as serviceable products.
Separate inventories are considered for incoming as well as inspected-and-graded
E. Fernández et al.
cannot be recovered. On the other hand, polyurethane has better energy efficiency
than the glass wool, but the later can be removed easier than the former, simplifying
thus the process of dismantling. Therefore, glass wool brings more benefits for EoL
of the product than polyurethane foam. We note that way to simplify the dismantling process is to put a nylon layer between the tank and the insulation, to avoid
polyurethane sticking to the tank.
39.4 Hybrid Production-Remanufacturing System
In this section we describe the hybrid production-remanufacturing system proposed
to evaluate the impact of including recovery options for DESWH. Hybrid productionremanufacturing systems refer to production systems in which the demand requirements of an item can be also satisfied by remanufacturing used items returned to the
origin. This hybrid system can be modelled as a Mixed-Integer Linear Programming
(MILP). This MILP consists of an objective function for minimizing the sum of the
costs involved and a set of equations and inequations for establishing the constraints
of the problem, all them composed by linear expressions of certain variables and
parameters. To solve the model and thus determine the optimal values of the variables, it is necessary to provide the values of the problem parameters. In this case it
involves the values of the demand, returns and the costs for both holding inventory
and carry out the production activities. We note that the current production system
of Rivomark does not consider recovery options. Therefore, the values of the parameters related to the returns were estimated based on the analysis of recoverability
of DESWHs presented in Sect. 39.3. The other values required for the model were
estimated along with Rivomark.
39.4.1 Problem Description
We consider the dynamic demand requirements of multiple items (i.e., different
DESWH types) over a finite number of periods, that can be satisfied by producing
new items or by remanufacturing used items returned to the origin. The condition of
the incoming returns is assumed diverse (heterogeneous returns) and an inspection
activity is required to determine their quality. The inspection process is that provided
in Sect. 39.3.1. Through inspection, the returns are graded into a finite number of
nominal quality levels of non-remanufacturable and remanufacturable items (inferior
and superior qualities). Two and five quality levels are considered in this study for
remanufacturable and non-remanufacturable returns, respectively. Remanufactured
and new products are assumed perfect substitutes despite the heterogeneous quality
of the incoming returns, i.e., remanufactured products look as good as new. Unit
costs are incurred for holding inventories of returns as well as serviceable products.
Separate inventories are considered for incoming as well as inspected-and-graded