Kraus operators are used to decompose into operator form a quantum channel $\mathcal{E}: \rho \rightarrow \mathcal{E}(\rho)$ which is a CPTP map i.e. it sends density matrices into density matrices.

$$\mathcal{E}(\rho) = \sum_k K_k\rho K_k^\dagger$$

To derive the Lindbald master equation you need the following $$K_1 = \sqrt{dt}L$$ $$K_0 = I - \frac{i}{\hbar}H dt - \frac{1}{2}$$

You then use: $$\rho(t + dt) = K_0\rho K_0^\dagger + K_1\rrho K_1^\dagger$$